sudo_plugin(8) — Linux manual page

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SUDO_PLUGIN(5)           BSD File Formats Manual          SUDO_PLUGIN(5)

NAME         top

     sudo_plugin — Sudo Plugin API

DESCRIPTION         top

     Starting with version 1.8, sudo supports a plugin API for policy
     and session logging.  Plugins may be compiled as dynamic shared
     objects (the default on systems that support them) or compiled
     statically into the sudo binary itself.  By default, the sudoers
     policy plugin and an associated I/O logging plugin are used.  Via
     the plugin API, sudo can be configured to use alternate policy
     and/or I/O logging plugins provided by third parties.  The plugins
     to be used are specified in the sudo.conf(5) file.

     The API is versioned with a major and minor number.  The minor
     version number is incremented when additions are made.  The major
     number is incremented when incompatible changes are made.  A plugin
     should be check the version passed to it and make sure that the
     major version matches.

     The plugin API is defined by the sudo_plugin.h header file.

   Policy plugin API
     A policy plugin must declare and populate a policy_plugin struct in
     the global scope.  This structure contains pointers to the
     functions that implement the sudo policy checks.  The name of the
     symbol should be specified in sudo.conf(5) along with a path to the
     plugin so that sudo can load it.

     struct policy_plugin {
     #define SUDO_POLICY_PLUGIN     1
         unsigned int type; /* always SUDO_POLICY_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t plugin_printf, char * const settings[],
             char * const user_info[], char * const user_env[],
             char * const plugin_options[], const char **errstr);
         void (*close)(int exit_status, int error);
         int (*show_version)(int verbose);
         int (*check_policy)(int argc, char * const argv[],
             char *env_add[], char **command_info[],
             char **argv_out[], char **user_env_out[], const char **errstr);
         int (*list)(int argc, char * const argv[], int verbose,
             const char *list_user, const char **errstr);
         int (*validate)(const char **errstr);
         void (*invalidate)(int remove);
         int (*init_session)(struct passwd *pwd, char **user_env[],
             const char **errstr);
         void (*register_hooks)(int version,
            int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
            int (*deregister_hook)(struct sudo_hook *hook));
         struct sudo_plugin_event * (*event_alloc)(void);
     };

     The policy_plugin struct has the following fields:

     type  The type field should always be set to SUDO_POLICY_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was
           built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t plugin_printf, char * const settings[],
               char * const user_info[], char * const user_env[],
               char * const plugin_options[], const char **errstr);

           Returns 1 on success, 0 on failure, -1 if a general error
           occurred, or -2 if there was a usage error.  In the latter
           case, sudo will print a usage message before it exits.  If an
           error occurs, the plugin may optionally call the
           conversation() or plugin_printf() function with
           SUDO_CONF_ERROR_MSG to present additional error information
           to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to
                 determine the major and minor version number of the
                 plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that can be
                 used by the plugin to interact with the user (see
                 Conversation API for details).  Returns 0 on success
                 and -1 on failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used
                 to display informational or error messages (see
                 Conversation API for details).  Returns the number of
                 characters printed on success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of
                 “name=value” strings.  The vector is terminated by a
                 NULL pointer.  These settings correspond to options the
                 user specified when running sudo.  As such, they will
                 only be present when the corresponding option has been
                 specified on the command line.

                 When parsing settings, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 The following values may be set by sudo:

                 bsdauth_type=string
                       Authentication type, if specified by the -a
                       option, to use on systems where BSD
                       authentication is supported.

                 closefrom=number
                       If specified, the user has requested via the -C
                       option that sudo close all files descriptors with
                       a value of number or higher.  The plugin may
                       optionally pass this, or another value, back in
                       the command_info list.

                 cmnd_chroot=string
                       The root directory (see chroot(2)) to run the
                       command in, as specified by the user via the -R
                       option.  The plugin may ignore or restrict the
                       user's ability to specify a new root directory.
                       Only available starting with API version 1.16.

                 cmnd_cwd=string
                       The working directory to run the command in, as
                       specified by the user via the -D option.  The
                       plugin may ignore or restrict the user's ability
                       to specify a new working directory.  Only
                       available starting with API version 1.16.

                 debug_flags=string
                       A debug file path name followed by a space and a
                       comma-separated list of debug flags that
                       correspond to the plugin's Debug entry in
                       sudo.conf(5), if there is one.  The flags are
                       passed to the plugin exactly as they appear in
                       sudo.conf(5).  The syntax used by sudo and the
                       sudoers plugin is subsystem@priority but a plugin
                       is free to use a different format so long as it
                       does not include a comma (‘,’).  Prior to sudo
                       1.8.12, there was no way to specify plugin-
                       specific debug_flags so the value was always the
                       same as that used by the sudo front end and did
                       not include a path name, only the flags
                       themselves.  As of version 1.7 of the plugin
                       interface, sudo will only pass debug_flags if
                       sudo.conf(5) contains a plugin-specific Debug
                       entry.

                 ignore_ticket=bool
                       Set to true if the user specified the -k option
                       along with a command, indicating that the user
                       wishes to ignore any cached authentication
                       credentials.  implied_shell to true.  This allows
                       sudo with no arguments to be used similarly to
                       su(1).  If the plugin does not to support this
                       usage, it may return a value of -2 from the
                       check_policy() function, which will cause sudo to
                       print a usage message and exit.

                 implied_shell=bool
                       If the user does not specify a program on the
                       command line, sudo will pass the plugin the path
                       to the user's shell and set

                 login_class=string
                       BSD login class to use when setting resource
                       limits and nice value, if specified by the -c
                       option.

                 login_shell=bool
                       Set to true if the user specified the -i option,
                       indicating that the user wishes to run a login
                       shell.

                 max_groups=int
                       The maximum number of groups a user may belong
                       to.  This will only be present if there is a
                       corresponding setting in sudo.conf(5).

                 network_addrs=list
                       A space-separated list of IP network addresses
                       and netmasks in the form “addr/netmask”, e.g.,
                       “192.168.1.2/255.255.255.0”.  The address and
                       netmask pairs may be either IPv4 or IPv6,
                       depending on what the operating system supports.
                       If the address contains a colon (‘:’), it is an
                       IPv6 address, else it is IPv4.

                 noninteractive=bool
                       Set to true if the user specified the -n option,
                       indicating that sudo should operate in non-
                       interactive mode.  The plugin may reject a
                       command run in non-interactive mode if user
                       interaction is required.

                 plugin_dir=string
                       The default plugin directory used by the sudo
                       front end.  This is the default directory set at
                       compile time and may not correspond to the
                       directory the running plugin was loaded from.  It
                       may be used by a plugin to locate support files.

                 plugin_path=string
                       The path name of plugin loaded by the sudo front
                       end.  The path name will be a fully-qualified
                       unless the plugin was statically compiled into
                       sudo.

                 preserve_environment=bool
                       Set to true if the user specified the -E option,
                       indicating that the user wishes to preserve the
                       environment.

                 preserve_groups=bool
                       Set to true if the user specified the -P option,
                       indicating that the user wishes to preserve the
                       group vector instead of setting it based on the
                       runas user.

                 progname=string
                       The command name that sudo was run as, typically
                       “sudo” or “sudoedit”.

                 prompt=string
                       The prompt to use when requesting a password, if
                       specified via the -p option.

                 remote_host=string
                       The name of the remote host to run the command
                       on, if specified via the -h option.  Support for
                       running the command on a remote host is meant to
                       be implemented via a helper program that is
                       executed in place of the user-specified command.
                       The sudo front end is only capable of executing
                       commands on the local host.  Only available
                       starting with API version 1.4.

                 run_shell=bool
                       Set to true if the user specified the -s option,
                       indicating that the user wishes to run a shell.

                 runas_group=string
                       The group name or gid to run the command as, if
                       specified via the -g option.

                 runas_user=string
                       The user name or uid to run the command as, if
                       specified via the -u option.

                 selinux_role=string
                       SELinux role to use when executing the command,
                       if specified by the -r option.

                 selinux_type=string
                       SELinux type to use when executing the command,
                       if specified by the -t option.

                 set_home=bool
                       Set to true if the user specified the -H option.
                       If true, set the HOME environment variable to the
                       target user's home directory.

                 sudoedit=bool
                       Set to true when the -e option is specified or if
                       invoked as sudoedit.  The plugin shall substitute
                       an editor into argv in the check_policy()
                       function or return -2 with a usage error if the
                       plugin does not support sudoedit.  For more
                       information, see the check_policy section.

                 timeout=string
                       Command timeout specified by the user via the -T
                       option.  Not all plugins support command timeouts
                       and the ability of the user to set a timeout may
                       be restricted by policy.  The format of the
                       timeout string is plugin-specific.

                 Additional settings may be added in the future so the
                 plugin should silently ignore settings that it does not
                 recognize.

           user_info
                 A vector of information about the user running the
                 command in the form of “name=value” strings.  The
                 vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 The following values may be set by sudo:

                 cols=int
                       The number of columns the user's terminal
                       supports.  If there is no terminal device
                       available, a default value of 80 is used.

                 cwd=string
                       The user's current working directory.

                 egid=gid_t
                       The effective group-ID of the user invoking sudo.

                 euid=uid_t
                       The effective user-ID of the user invoking sudo.

                 gid=gid_t
                       The real group-ID of the user invoking sudo.

                 groups=list
                       The user's supplementary group list formatted as
                       a string of comma-separated group-IDs.

                 host=string
                       The local machine's hostname as returned by the
                       gethostname(2) system call.

                 lines=int
                       The number of lines the user's terminal supports.
                       If there is no terminal device available, a
                       default value of 24 is used.

                 pgid=int
                       The ID of the process group that the running sudo
                       process is a member of.  Only available starting
                       with API version 1.2.

                 pid=int
                       The process ID of the running sudo process.  Only
                       available starting with API version 1.2.

                 ppid=int
                       The parent process ID of the running sudo
                       process.  Only available starting with API
                       version 1.2.

                 rlimit_as=soft,hard
                       The maximum size to which the process's address
                       space may grow (in bytes), if supported by the
                       operating system.  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_core=soft,hard
                       The largest size core dump file that may be
                       created (in bytes).  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_cpu=soft,hard
                       The maximum amount of CPU time that the process
                       may use (in seconds).  The soft and hard limits
                       are separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_data=soft,hard
                       The maximum size of the data segment for the
                       process (in bytes).  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_fsize=soft,hard
                       The largest size file that the process may create
                       (in bytes).  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_locks=soft,hard
                       The maximum number of locks that the process may
                       establish, if supported by the operating system.
                       The soft and hard limits are separated by a
                       comma.  A value of “infinity” indicates that
                       there is no limit.  Only available starting with
                       API version 1.16.

                 rlimit_memlock=soft,hard
                       The maximum size that the process may lock in
                       memory (in bytes), if supported by the operating
                       system.  The soft and hard limits are separated
                       by a comma.  A value of “infinity” indicates that
                       there is no limit.  Only available starting with
                       API version 1.16.

                 rlimit_nofile=soft,hard
                       The maximum number of files that the process may
                       have open.  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_nproc=soft,hard
                       The maximum number of processes that the user may
                       run simultaneously.  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 rlimit_rss=soft,hard
                       The maximum size to which the process's resident
                       set size may grow (in bytes).  The soft and hard
                       limits are separated by a comma.  A value of
                       “infinity” indicates that there is no limit.
                       Only available starting with API version 1.16.

                 rlimit_stack=soft,hard
                       The maximum size to which the process's stack may
                       grow (in bytes).  The soft and hard limits are
                       separated by a comma.  A value of “infinity”
                       indicates that there is no limit.  Only available
                       starting with API version 1.16.

                 sid=int
                       The session ID of the running sudo process or 0
                       if sudo is not part of a POSIX job control
                       session.  Only available starting with API
                       version 1.2.

                 tcpgid=int
                       The ID of the foreground process group associated
                       with the terminal device associated with the sudo
                       process or 0 if there is no terminal present.
                       Only available starting with API version 1.2.

                 tty=string
                       The path to the user's terminal device.  If the
                       user has no terminal device associated with the
                       session, the value will be empty, as in “tty=”.

                 uid=uid_t
                       The real user-ID of the user invoking sudo.

                 umask=octal
                       The invoking user's file creation mask.  Only
                       available starting with API version 1.10.

                 user=string
                       The name of the user invoking sudo.

           user_env
                 The user's environment in the form of a NULL-terminated
                 vector of “name=value” strings.

                 When parsing user_env, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin
                 path are passed as arguments to the plugin.  These
                 arguments are split on a white space boundary and are
                 passed to the plugin in the form of a NULL-terminated
                 array of strings.  If no arguments were specified,
                 plugin_options will be the NULL pointer.

                 NOTE: the plugin_options parameter is only available
                 starting with API version 1.2.  A plugin must check the
                 API version specified by the sudo front end before
                 using plugin_options.  Failure to do so may result in a
                 crash.

           errstr
                 If the open() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     close
           void (*close)(int exit_status, int error);

           The close() function is called when sudo is finished, shortly
           before it exits.  Starting with API version 1.15, close() is
           called regardless of whether or not a command was actually
           executed.  This makes it possible for plugins to perform
           cleanup even when a command was not run.  It is not possible
           to tell whether a command was run based solely on the
           arguments passed to the close() function.  To determine if a
           command was actually run, the plugin must keep track of
           whether or not the check_policy() function returned
           successfully.

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2)
                 system call, or zero if no command was run.  The value
                 of exit_status is undefined if error is non-zero.

           error
                 If the command could not be executed, this is set to
                 the value of errno set by the execve(2) system call.
                 The plugin is responsible for displaying error
                 information via the conversation() or plugin_printf()
                 function.  If the command was successfully executed,
                 the value of error is zero.

           If no close() function is defined, no I/O logging plugins are
           loaded, and neither the timeout not use_pty options are set
           in the command_info list, the sudo front end may execute the
           command directly instead of running it as a child process.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user
           specifies the -V option.  The plugin may display its version
           information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.  If the
           user requests detailed version information, the verbose flag
           will be set.

           Returns 1 on success, 0 on failure, -1 if a general error
           occurred, or -2 if there was a usage error, although the
           return value is currently ignored.

     check_policy
           int (*check_policy)(int argc, char * const argv[], char *env_add[],
               char **command_info[], char **argv_out[], char **user_env_out[],
               const char **errstr);

           The check_policy() function is called by sudo to determine
           whether the user is allowed to run the specified commands.

           If the sudoedit option was enabled in the settings array
           passed to the open() function, the user has requested
           sudoedit mode.  sudoedit is a mechanism for editing one or
           more files where an editor is run with the user's credentials
           instead of with elevated privileges.  sudo achieves this by
           creating user-writable temporary copies of the files to be
           edited and then overwriting the originals with the temporary
           copies after editing is complete.  If the plugin supports
           sudoedit, it should choose the editor to be used, potentially
           from a variable in the user's environment, such as EDITOR,
           and include it in argv_out (note that environment variables
           may include command line options).  The files to be edited
           should be copied from argv into argv_out, separated from the
           editor and its arguments by a “--” element.  The “--” will be
           removed by sudo before the editor is executed.  The plugin
           should also set sudoedit=true in the command_info list.

           The check_policy() function returns 1 if the command is
           allowed, 0 if not allowed, -1 for a general error, or -2 for
           a usage error or if sudoedit was specified but is unsupported
           by the plugin.  In the latter case, sudo will print a usage
           message before it exits.  If an error occurs, the plugin may
           optionally call the conversation() or plugin_printf()
           function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           The function arguments are as follows:

           argc  The number of elements in argv, not counting the final
                 NULL pointer.

           argv  The argument vector describing the command the user
                 wishes to run, in the same form as what would be passed
                 to the execve(2) system call.  The vector is terminated
                 by a NULL pointer.

           env_add
                 Additional environment variables specified by the user
                 on the command line in the form of a NULL-terminated
                 vector of “name=value” strings.  The plugin may reject
                 the command if one or more variables are not allowed to
                 be set, or it may silently ignore such variables.

                 When parsing env_add, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

           command_info
                 Information about the command being run in the form of
                 “name=value” strings.  These values are used by sudo to
                 set the execution environment when running a command.
                 The plugin is responsible for creating and populating
                 the vector, which must be terminated with a NULL
                 pointer.  The following values are recognized by sudo:

                 chroot=string
                       The root directory to use when running the
                       command.

                 closefrom=number
                       If specified, sudo will close all files
                       descriptors with a value of number or higher.

                 command=string
                       Fully qualified path to the command to be
                       executed.

                 cwd=string
                       The current working directory to change to when
                       executing the command.  If sudo is unable to
                       change to the new working directory, the command
                       will not be run unless cwd_optional is also set
                       (see below).

                 cwd_optional=bool
                       If enabled, sudo will treat an inability to
                       change to the new working directory as a non-
                       fatal error.  This setting has no effect unless
                       cwd is also set.

                 exec_background=bool
                       By default, sudo runs a command as the foreground
                       process as long as sudo itself is running in the
                       foreground.  When exec_background is enabled and
                       the command is being run in a pseudo-terminal
                       (due to I/O logging or the use_pty setting), the
                       command will be run as a background process.
                       Attempts to read from the controlling terminal
                       (or to change terminal settings) will result in
                       the command being suspended with the SIGTTIN
                       signal (or SIGTTOU in the case of terminal
                       settings).  If this happens when sudo is a
                       foreground process, the command will be granted
                       the controlling terminal and resumed in the
                       foreground with no user intervention required.
                       The advantage of initially running the command in
                       the background is that sudo need not read from
                       the terminal unless the command explicitly
                       requests it.  Otherwise, any terminal input must
                       be passed to the command, whether it has required
                       it or not (the kernel buffers terminals so it is
                       not possible to tell whether the command really
                       wants the input).  This is different from
                       historic sudo behavior or when the command is not
                       being run in a pseudo-terminal.

                       For this to work seamlessly, the operating system
                       must support the automatic restarting of system
                       calls.  Unfortunately, not all operating systems
                       do this by default, and even those that do may
                       have bugs.  For example, macOS fails to restart
                       the tcgetattr() and tcsetattr() system calls
                       (this is a bug in macOS).  Furthermore, because
                       this behavior depends on the command stopping
                       with the SIGTTIN or SIGTTOU signals, programs
                       that catch these signals and suspend themselves
                       with a different signal (usually SIGTOP) will not
                       be automatically foregrounded.  Some versions of
                       the linux su(1) command behave this way.  Because
                       of this, a plugin should not set exec_background
                       unless it is explicitly enabled by the
                       administrator and there should be a way to
                       enabled or disable it on a per-command basis.

                       This setting has no effect unless I/O logging is
                       enabled or use_pty is enabled.

                 execfd=number
                       If specified, sudo will use the fexecve(2) system
                       call to execute the command instead of execve(2).
                       The specified number must refer to an open file
                       descriptor.

                 iolog_compress=bool
                       Set to true if the I/O logging plugins, if any,
                       should compress the log data.  This is a hint to
                       the I/O logging plugin which may choose to ignore
                       it.

                 iolog_group=string
                       The group that will own newly created I/O log
                       files and directories.  This is a hint to the I/O
                       logging plugin which may choose to ignore it.

                 iolog_mode=octal
                       The file permission mode to use when creating I/O
                       log files and directories.  This is a hint to the
                       I/O logging plugin which may choose to ignore it.

                 iolog_user=string
                       The user that will own newly created I/O log
                       files and directories.  This is a hint to the I/O
                       logging plugin which may choose to ignore it.

                 iolog_path=string
                       Fully qualified path to the file or directory in
                       which I/O log is to be stored.  This is a hint to
                       the I/O logging plugin which may choose to ignore
                       it.  If no I/O logging plugin is loaded, this
                       setting has no effect.

                 iolog_stdin=bool
                       Set to true if the I/O logging plugins, if any,
                       should log the standard input if it is not
                       connected to a terminal device.  This is a hint
                       to the I/O logging plugin which may choose to
                       ignore it.

                 iolog_stdout=bool
                       Set to true if the I/O logging plugins, if any,
                       should log the standard output if it is not
                       connected to a terminal device.  This is a hint
                       to the I/O logging plugin which may choose to
                       ignore it.

                 iolog_stderr=bool
                       Set to true if the I/O logging plugins, if any,
                       should log the standard error if it is not
                       connected to a terminal device.  This is a hint
                       to the I/O logging plugin which may choose to
                       ignore it.

                 iolog_ttyin=bool
                       Set to true if the I/O logging plugins, if any,
                       should log all terminal input.  This only
                       includes input typed by the user and not from a
                       pipe or redirected from a file.  This is a hint
                       to the I/O logging plugin which may choose to
                       ignore it.

                 iolog_ttyout=bool
                       Set to true if the I/O logging plugins, if any,
                       should log all terminal output.  This only
                       includes output to the screen, not output to a
                       pipe or file.  This is a hint to the I/O logging
                       plugin which may choose to ignore it.

                 login_class=string
                       BSD login class to use when setting resource
                       limits and nice value (optional).  This option is
                       only set on systems that support login classes.

                 nice=int
                       Nice value (priority) to use when executing the
                       command.  The nice value, if specified, overrides
                       the priority associated with the login_class on
                       BSD systems.

                 noexec=bool
                       If set, prevent the command from executing other
                       programs.

                 preserve_fds=list
                       A comma-separated list of file descriptors that
                       should be preserved, regardless of the value of
                       the closefrom setting.  Only available starting
                       with API version 1.5.

                 preserve_groups=bool
                       If set, sudo will preserve the user's group
                       vector instead of initializing the group vector
                       based on runas_user.

                 runas_egid=gid
                       Effective group-ID to run the command as.  If not
                       specified, the value of runas_gid is used.

                 runas_euid=uid
                       Effective user-ID to run the command as.  If not
                       specified, the value of runas_uid is used.

                 runas_gid=gid
                       Group-ID to run the command as.

                 runas_group=string
                       The name of the group the command will run as, if
                       it is different from the runas_user's default
                       group.  This value is provided for auditing
                       purposes only, the sudo front-end uses runas_egid
                       and runas_gid when executing the command.

                 runas_groups=list
                       The supplementary group vector to use for the
                       command in the form of a comma-separated list of
                       group-IDs.  If preserve_groups is set, this
                       option is ignored.

                 runas_uid=uid
                       User-ID to run the command as.

                 runas_user=string
                       The name of the user the command will run as,
                       which should correspond to runas_euid (or
                       runas_uid if runas_euid is not set).  This value
                       is provided for auditing purposes only, the sudo
                       front-end uses runas_euid and runas_uid when
                       executing the command.

                 selinux_role=string
                       SELinux role to use when executing the command.

                 selinux_type=string
                       SELinux type to use when executing the command.

                 set_utmp=bool
                       Create a utmp (or utmpx) entry when a pseudo-
                       terminal is allocated.  By default, the new entry
                       will be a copy of the user's existing utmp entry
                       (if any), with the tty, time, type and pid fields
                       updated.

                 sudoedit=bool
                       Set to true when in sudoedit mode.  The plugin
                       may enable sudoedit mode even if sudo was not
                       invoked as sudoedit.  This allows the plugin to
                       perform command substitution and transparently
                       enable sudoedit when the user attempts to run an
                       editor.

                 sudoedit_checkdir=bool
                       Set to false to disable directory writability
                       checks in sudoedit.  By default, sudoedit 1.8.16
                       and higher will check all directory components of
                       the path to be edited for writability by the
                       invoking user.  Symbolic links will not be
                       followed in writable directories and sudoedit
                       will refuse to edit a file located in a writable
                       directory.  These restrictions are not enforced
                       when sudoedit is run by root.  The
                       sudoedit_follow option can be set to false to
                       disable this check.  Only available starting with
                       API version 1.8.

                 sudoedit_follow=bool
                       Set to true to allow sudoedit to edit files that
                       are symbolic links.  By default, sudoedit 1.8.15
                       and higher will refuse to open a symbolic link.
                       The sudoedit_follow option can be used to restore
                       the older behavior and allow sudoedit to open
                       symbolic links.  Only available starting with API
                       version 1.8.

                 timeout=int
                       Command timeout.  If non-zero then when the
                       timeout expires the command will be killed.

                 umask=octal
                       The file creation mask to use when executing the
                       command.  This value may be overridden by PAM or
                       login.conf on some systems unless the
                       umask_override option is also set.

                 umask_override=bool
                       Force the value specified by the umask option to
                       override any umask set by PAM or login.conf.

                 use_pty=bool
                       Allocate a pseudo-terminal to run the command in,
                       regardless of whether or not I/O logging is in
                       use.  By default, sudo will only run the command
                       in a pseudo-terminal when an I/O log plugin is
                       loaded.

                 utmp_user=string
                       User name to use when constructing a new utmp (or
                       utmpx) entry when set_utmp is enabled.  This
                       option can be used to set the user field in the
                       utmp entry to the user the command runs as rather
                       than the invoking user.  If not set, sudo will
                       base the new entry on the invoking user's
                       existing entry.

                 Unsupported values will be ignored.

           argv_out
                 The NULL-terminated argument vector to pass to the
                 execve(2) system call when executing the command.  The
                 plugin is responsible for allocating and populating the
                 vector.

           user_env_out
                 The NULL-terminated environment vector to use when
                 executing the command.  The plugin is responsible for
                 allocating and populating the vector.

           errstr
                 If the check_policy() function returns a value other
                 than 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     list
           int (*list)(int argc, char * const argv[], int verbose,
               const char *list_user, const char **errstr);

           List available privileges for the invoking user.  Returns 1
           on success, 0 on failure and -1 on error.  On error, the
           plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present
           additional error information to the user.

           Privileges should be output via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.

           The function arguments are as follows:

           argc  The number of elements in argv, not counting the final
                 NULL pointer.

           argv  If non-NULL, an argument vector describing a command
                 the user wishes to check against the policy in the same
                 form as what would be passed to the execve(2) system
                 call.  If the command is permitted by the policy, the
                 fully-qualified path to the command should be displayed
                 along with any command line arguments.

           verbose
                 Flag indicating whether to list in verbose mode or not.

           list_user
                 The name of a different user to list privileges for if
                 the policy allows it.  If NULL, the plugin should list
                 the privileges of the invoking user.

           errstr
                 If the list() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     validate
           int (*validate)(const char **errstr);

           The validate() function is called when sudo is run with the
           -v option.  For policy plugins such as sudoers that cache
           authentication credentials, this function will validate and
           cache the credentials.

           The validate() function should be NULL if the plugin does not
           support credential caching.

           Returns 1 on success, 0 on failure and -1 on error.  On
           error, the plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present
           additional error information to the user.

           The function arguments are as follows:

           errstr
                 If the validate() function returns a value other than
                 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     invalidate
           void (*invalidate)(int remove);

           The invalidate() function is called when sudo is run with the
           -k or -K option.  For policy plugins such as sudoers that
           cache authentication credentials, this function will
           invalidate the credentials.  If the remove flag is set, the
           plugin may remove the credentials instead of simply
           invalidating them.

           The invalidate() function should be NULL if the plugin does
           not support credential caching.

     init_session
           int (*init_session)(struct passwd *pwd, char **user_env_out[]);

           The init_session() function is called before sudo sets up the
           execution environment for the command.  It is run in the
           parent sudo process and before any uid or gid changes.  This
           can be used to perform session setup that is not supported by
           command_info, such as opening the PAM session.  The close()
           function can be used to tear down the session that was opened
           by init_session.

           The pwd argument points to a passwd struct for the user the
           command will be run as if the uid the command will run as was
           found in the password database, otherwise it will be NULL.

           The user_env_out argument points to the environment the
           command will run in, in the form of a NULL-terminated vector
           of “name=value” strings.  This is the same string passed back
           to the front end via the Policy Plugin's user_env_out
           parameter.  If the init_session() function needs to modify
           the user environment, it should update the pointer stored in
           user_env_out.  The expected use case is to merge the contents
           of the PAM environment (if any) with the contents of
           user_env_out.  NOTE: the user_env_out parameter is only
           available starting with API version 1.2.  A plugin must check
           the API version specified by the sudo front end before using
           user_env_out.  Failure to do so may result in a crash.

           Returns 1 on success, 0 on failure and -1 on error.  On
           error, the plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present
           additional error information to the user.

     register_hooks
           void (*register_hooks)(int version,
              int (*register_hook)(struct sudo_hook *hook));

           The register_hooks() function is called by the sudo front end
           to register any hooks the plugin needs.  If the plugin does
           not support hooks, register_hooks should be set to the NULL
           pointer.

           The version argument describes the version of the hooks API
           supported by the sudo front end.

           The register_hook() function should be used to register any
           supported hooks the plugin needs.  It returns 0 on success, 1
           if the hook type is not supported and -1 if the major version
           in struct hook does not match the front end's major hook API
           version.

           See the Hook function API section below for more information
           about hooks.

           NOTE: the register_hooks() function is only available
           starting with API version 1.2.  If the sudo front end doesn't
           support API version 1.2 or higher, register_hooks will not be
           called.

     deregister_hooks
           void (*deregister_hooks)(int version,
              int (*deregister_hook)(struct sudo_hook *hook));

           The deregister_hooks() function is called by the sudo front
           end to deregister any hooks the plugin has registered.  If
           the plugin does not support hooks, deregister_hooks should be
           set to the NULL pointer.

           The version argument describes the version of the hooks API
           supported by the sudo front end.

           The deregister_hook() function should be used to deregister
           any hooks that were put in place by the register_hook()
           function.  If the plugin tries to deregister a hook that the
           front end does not support, deregister_hook will return an
           error.

           See the Hook function API section below for more information
           about hooks.

           NOTE: the deregister_hooks() function is only available
           starting with API version 1.2.  If the sudo front end doesn't
           support API version 1.2 or higher, deregister_hooks will not
           be called.

     event_alloc
           struct sudo_plugin_event * (*event_alloc)(void);

           The event_alloc() function is used to allocate a struct
           sudo_plugin_event which provides access to the main sudo
           event loop.  Unlike the other fields, the event_alloc()
           pointer is filled in by the sudo front end, not by the
           plugin.

           See the Event API section below for more information about
           events.

           NOTE: the event_alloc() function is only available starting
           with API version 1.15.  If the sudo front end doesn't support
           API version 1.15 or higher, event_alloc() will not be set.

     errstr
           If the init_session() function returns a value other than 1,
           the plugin may store a message describing the failure or
           error in errstr.  The sudo front end will then pass this
           value to any registered audit plugins.  The string stored in
           errstr must remain valid until the plugin's close() function
           is called.

           NOTE: the errstr parameter is only available starting with
           API version 1.15.  A plugin must check the API version
           specified by the sudo front end before using errstr.  Failure
           to do so may result in a crash.

     Policy Plugin Version Macros

     /* Plugin API version major/minor. */
     #define SUDO_API_VERSION_MAJOR 1
     #define SUDO_API_VERSION_MINOR 13
     #define SUDO_API_MKVERSION(x, y) ((x << 16) | y)
     #define SUDO_API_VERSION SUDO_API_MKVERSION(SUDO_API_VERSION_MAJOR,\
                                                 SUDO_API_VERSION_MINOR)

     /* Getters and setters for API version */
     #define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16)
     #define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
     #define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \
         *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \
     } while(0)
     #define SUDO_API_VERSION_SET_MINOR(vp, n) do { \
         *(vp) = (*(vp) & 0xffff0000) | (n); \
     } while(0)

   I/O plugin API
     struct io_plugin {
     #define SUDO_IO_PLUGIN 2
         unsigned int type; /* always SUDO_IO_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t plugin_printf, char * const settings[],
             char * const user_info[], char * const command_info[],
             int argc, char * const argv[], char * const user_env[],
             char * const plugin_options[], const char **errstr);
         void (*close)(int exit_status, int error); /* wait status or error */
         int (*show_version)(int verbose);
         int (*log_ttyin)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_ttyout)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_stdin)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_stdout)(const char *buf, unsigned int len,
             const char **errstr);
         int (*log_stderr)(const char *buf, unsigned int len,
             const char **errstr);
         void (*register_hooks)(int version,
            int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
            int (*deregister_hook)(struct sudo_hook *hook));
         int (*change_winsize)(unsigned int lines, unsigned int cols,
             const char **errstr);
         int (*log_suspend)(int signo, const char **errstr);
         struct sudo_plugin_event * (*event_alloc)(void);
     };

     When an I/O plugin is loaded, sudo runs the command in a pseudo-
     terminal.  This makes it possible to log the input and output from
     the user's session.  If any of the standard input, standard output
     or standard error do not correspond to a tty, sudo will open a pipe
     to capture the I/O for logging before passing it on.

     The log_ttyin function receives the raw user input from the
     terminal device (note that this will include input even when echo
     is disabled, such as when a password is read).  The log_ttyout
     function receives output from the pseudo-terminal that is suitable
     for replaying the user's session at a later time.  The log_stdin(),
     log_stdout() and log_stderr() functions are only called if the
     standard input, standard output or standard error respectively
     correspond to something other than a tty.

     Any of the logging functions may be set to the NULL pointer if no
     logging is to be performed.  If the open function returns 0, no I/O
     will be sent to the plugin.

     If a logging function returns an error (-1), the running command
     will be terminated and all of the plugin's logging functions will
     be disabled.  Other I/O logging plugins will still receive any
     remaining input or output that has not yet been processed.

     If an input logging function rejects the data by returning 0, the
     command will be terminated and the data will not be passed to the
     command, though it will still be sent to any other I/O logging
     plugins.  If an output logging function rejects the data by
     returning 0, the command will be terminated and the data will not
     be written to the terminal, though it will still be sent to any
     other I/O logging plugins.

     The audit_plugin struct has the following fields:

     type  The type field should always be set to SUDO_IO_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was
           built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t plugin_printf, char * const settings[],
               char * const user_info[], char * const command_info[],
               int argc, char * const argv[], char * const user_env[],
               char * const plugin_options[]);

           The open() function is run before the log_ttyin(),
           log_ttyout(), log_stdin(), log_stdout(), log_stderr(),
           log_suspend(), change_winsize(), or show_version() functions
           are called.  It is only called if the version is being
           requested or if the policy plugin's check_policy() function
           has returned successfully.  It returns 1 on success, 0 on
           failure, -1 if a general error occurred, or -2 if there was a
           usage error.  In the latter case, sudo will print a usage
           message before it exits.  If an error occurs, the plugin may
           optionally call the conversation() or plugin_printf()
           function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to
                 determine the major and minor version number of the
                 plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that may be
                 used by the show_version() function to display version
                 information (see show_version() below).  The
                 conversation() function may also be used to display
                 additional error message to the user.  The
                 conversation() function returns 0 on success and -1 on
                 failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used
                 by the show_version() function to display version
                 information (see show_version below).  The
                 plugin_printf() function may also be used to display
                 additional error message to the user.  The
                 plugin_printf() function returns number of characters
                 printed on success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of
                 “name=value” strings.  The vector is terminated by a
                 NULL pointer.  These settings correspond to options the
                 user specified when running sudo.  As such, they will
                 only be present when the corresponding option has been
                 specified on the command line.

                 When parsing settings, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible settings.

           user_info
                 A vector of information about the user running the
                 command in the form of “name=value” strings.  The
                 vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           command_info
                 A vector of information describing the command being
                 run in the form of “name=value” strings.  The vector is
                 terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           argc  The number of elements in argv, not counting the final
                 NULL pointer.  It can be zero, when sudo is called with
                 -V.

           argv  If non-NULL, an argument vector describing a command
                 the user wishes to run in the same form as what would
                 be passed to the execve(2) system call.

           user_env
                 The user's environment in the form of a NULL-terminated
                 vector of “name=value” strings.

                 When parsing user_env, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin
                 path are treated as arguments to the plugin.  These
                 arguments are split on a white space boundary and are
                 passed to the plugin in the form of a NULL-terminated
                 array of strings.  If no arguments were specified,
                 plugin_options will be the NULL pointer.

                 NOTE: the plugin_options parameter is only available
                 starting with API version 1.2.  A plugin must check the
                 API version specified by the sudo front end before
                 using plugin_options.  Failure to do so may result in a
                 crash.

           errstr
                 If the open() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     close
           void (*close)(int exit_status, int error);

           The close() function is called when sudo is finished, shortly
           before it exits.

           The function arguments are as follows:

           exit_status
                 The command's exit status, as returned by the wait(2)
                 system call, or zero if no command was run.  The value
                 of exit_status is undefined if error is non-zero.

           error
                 If the command could not be executed, this is set to
                 the value of errno set by the execve(2) system call.
                 If the command was successfully executed, the value of
                 error is zero.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user
           specifies the -V option.  The plugin may display its version
           information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.

           Returns 1 on success, 0 on failure, -1 if a general error
           occurred, or -2 if there was a usage error, although the
           return value is currently ignored.

     log_ttyin
           int (*log_ttyin)(const char *buf, unsigned int len,
               const char **errstr);

           The log_ttyin() function is called whenever data can be read
           from the user but before it is passed to the running command.
           This allows the plugin to reject data if it chooses to (for
           instance if the input contains banned content).  Returns 1 if
           the data should be passed to the command, 0 if the data is
           rejected (which will terminate the running command) or -1 if
           an error occurred.

           The function arguments are as follows:

           buf   The buffer containing user input.

           len   The length of buf in bytes.

           errstr
                 If the log_ttyin() function returns a value other than
                 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     log_ttyout
           int (*log_ttyout)(const char *buf, unsigned int len,
               const char **errstr);

           The log_ttyout() function is called whenever data can be read
           from the command but before it is written to the user's
           terminal.  This allows the plugin to reject data if it
           chooses to (for instance if the output contains banned
           content).  Returns 1 if the data should be passed to the
           user, 0 if the data is rejected (which will terminate the
           running command) or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing command output.

           len   The length of buf in bytes.

           errstr
                 If the log_ttyout() function returns a value other than
                 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     log_stdin
           int (*log_stdin)(const char *buf, unsigned int len,
               const char **errstr);

           The log_stdin() function is only used if the standard input
           does not correspond to a tty device.  It is called whenever
           data can be read from the standard input but before it is
           passed to the running command.  This allows the plugin to
           reject data if it chooses to (for instance if the input
           contains banned content).  Returns 1 if the data should be
           passed to the command, 0 if the data is rejected (which will
           terminate the running command) or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing user input.

           len   The length of buf in bytes.

           errstr
                 If the log_stdin() function returns a value other than
                 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     log_stdout
           int (*log_stdout)(const char *buf, unsigned int len,
               const char **errstr);

           The log_stdout() function is only used if the standard output
           does not correspond to a tty device.  It is called whenever
           data can be read from the command but before it is written to
           the standard output.  This allows the plugin to reject data
           if it chooses to (for instance if the output contains banned
           content).  Returns 1 if the data should be passed to the
           user, 0 if the data is rejected (which will terminate the
           running command) or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing command output.

           len   The length of buf in bytes.

           errstr
                 If the log_stdout() function returns a value other than
                 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     log_stderr
           int (*log_stderr)(const char *buf, unsigned int len,
               const char **errstr);

           The log_stderr() function is only used if the standard error
           does not correspond to a tty device.  It is called whenever
           data can be read from the command but before it is written to
           the standard error.  This allows the plugin to reject data if
           it chooses to (for instance if the output contains banned
           content).  Returns 1 if the data should be passed to the
           user, 0 if the data is rejected (which will terminate the
           running command) or -1 if an error occurred.

           The function arguments are as follows:

           buf   The buffer containing command output.

           len   The length of buf in bytes.

           errstr
                 If the log_stderr() function returns a value other than
                 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     register_hooks
           See the Policy plugin API section for a description of
           register_hooks.

     deregister_hooks
           See the Policy plugin API section for a description of
           deregister_hooks.

     change_winsize
           int (*change_winsize)(unsigned int lines, unsigned int cols,
               const char **errstr);

           The change_winsize() function is called whenever the window
           size of the terminal changes from the initial values
           specified in the user_info list.  Returns -1 if an error
           occurred, in which case no further calls to change_winsize()
           will be made,

           The function arguments are as follows:

           lines
                 The number of lines (rows) in the re-sized terminal.

           cols  The number of columns in the re-sized terminal.

           errstr
                 If the change_winsize() function returns a value other
                 than 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

     log_suspend
           int (*log_suspend)(int signo, const char **errstr);

           The log_suspend() function is called whenever a command is
           suspended or resumed.  Logging this information makes it
           possible to skip the period of time when the command was
           suspended during playback of a session.  Returns -1 if an
           error occurred, in which case no further calls to
           log_suspend() will be made,

           The function arguments are as follows:

           signo
                 The signal that caused the command to be suspended, or
                 SIGCONT if the command was resumed.

           errstr
                 If the log_suspend() function returns a value other
                 than 1, the plugin may store a message describing the
                 failure or error in errstr.  The sudo front end will
                 then pass this value to any registered audit plugins.
                 The string stored in errstr must remain valid until the
                 plugin's close() function is called.

                 NOTE: the errstr parameter is only available starting
                 with API version 1.15.  A plugin must check the API
                 version specified by the sudo front end before using
                 errstr.  Failure to do so may result in a crash.

           event_alloc
                 struct sudo_plugin_event * (*event_alloc)(void);

                 The event_alloc() function is used to allocate a struct
                 sudo_plugin_event which provides access to the main
                 sudo event loop.  Unlike the other fields, the
                 event_alloc() pointer is filled in by the sudo front
                 end, not by the plugin.

                 See the Event API section below for more information
                 about events.

                 NOTE: the event_alloc() function is only available
                 starting with API version 1.15.  If the sudo front end
                 doesn't support API version 1.15 or higher,
                 event_alloc() will not be set.

           I/O Plugin Version Macros

           Same as for the Policy plugin API.

   Audit plugin API
     /* Audit plugin close function status types. */
     #define SUDO_PLUGIN_NO_STATUS           0
     #define SUDO_PLUGIN_WAIT_STATUS         1
     #define SUDO_PLUGIN_EXEC_ERROR          2
     #define SUDO_PLUGIN_SUDO_ERROR          3

     #define SUDO_AUDIT_PLUGIN 3
     struct audit_plugin {
         unsigned int type; /* always SUDO_AUDIT_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t sudo_printf, char * const settings[],
             char * const user_info[], int submit_optind,
             char * const submit_argv[], char * const submit_envp[],
             char * const plugin_options[], const char **errstr);
         void (*close)(int status_type, int status);
         int (*accept)(const char *plugin_name,
             unsigned int plugin_type, char * const command_info[],
             char * const run_argv[], char * const run_envp[],
             const char **errstr);
         int (*reject)(const char *plugin_name, unsigned int plugin_type,
             const char *audit_msg, char * const command_info[],
             const char **errstr);
         int (*error)(const char *plugin_name, unsigned int plugin_type,
             const char *audit_msg, char * const command_info[],
             const char **errstr);
         int (*show_version)(int verbose);
         void (*register_hooks)(int version,
             int (*register_hook)(struct sudo_hook *hook));
         void (*deregister_hooks)(int version,
             int (*deregister_hook)(struct sudo_hook *hook));
         struct sudo_plugin_event * (*event_alloc)(void);
     }

     An audit plugin can be used to log successful and unsuccessful
     attempts to run sudo independent of the policy or any I/O plugins.
     Multiple audit plugins may be specified in sudo.conf(5).

     The audit_plugin struct has the following fields:

     type  The type field should always be set to SUDO_AUDIT_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was
           built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t sudo_printf, char * const settings[],
               char * const user_info[], int submit_optind,
               char * const submit_argv[], char * const submit_envp[],
               char * const plugin_options[], const char **errstr);

           The audit open() function is run before any other sudo plugin
           API functions.  This makes it possible to audit failures in
           the other plugins.  It returns 1 on success, 0 on failure, -1
           if a general error occurred, or -2 if there was a usage
           error.  In the latter case, sudo will print a usage message
           before it exits.  If an error occurs, the plugin may
           optionally call the conversation() or plugin_printf()
           function with SUDO_CONF_ERROR_MSG to present additional error
           information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to
                 determine the major and minor version number of the
                 plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that may be
                 used by the show_version() function to display version
                 information (see show_version() below).  The
                 conversation() function may also be used to display
                 additional error message to the user.  The
                 conversation() function returns 0 on success and -1 on
                 failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used
                 by the show_version() function to display version
                 information (see show_version below).  The
                 plugin_printf() function may also be used to display
                 additional error message to the user.  The
                 plugin_printf() function returns number of characters
                 printed on success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of
                 “name=value” strings.  The vector is terminated by a
                 NULL pointer.  These settings correspond to options the
                 user specified when running sudo.  As such, they will
                 only be present when the corresponding option has been
                 specified on the command line.

                 When parsing settings, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible settings.

           user_info
                 A vector of information about the user running the
                 command in the form of “name=value” strings.  The
                 vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           submit_optind
                 The index into submit_argv that corresponds to the
                 first entry that is not a command line option.  If
                 submit_argv only consists of options, which may be the
                 case with the -l or -v options,
                 submit_argv[submit_optind] will evaluate to the NULL
                 pointer.

           submit_argv
                 The argument vector sudo was invoked with, including
                 all command line options.  The submit_optind argument
                 can be used to determine the end of the command line
                 options.

           submit_envp
                 The invoking user's environment in the form of a
                 NULL-terminated vector of “name=value” strings.

                 When parsing submit_envp, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin
                 path are treated as arguments to the plugin.  These
                 arguments are split on a white space boundary and are
                 passed to the plugin in the form of a NULL-terminated
                 array of strings.  If no arguments were specified,
                 plugin_options will be the NULL pointer.

           errstr
                 If the open() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

     close
           void (*close)(int status_type, int status);

           The close() function is called when sudo is finished, shortly
           before it exits.

           The function arguments are as follows:

           status_type
                 The type of status being passed.  One of
                 SUDO_PLUGIN_NO_STATUS, SUDO_PLUGIN_WAIT_STATUS,
                 SUDO_PLUGIN_EXEC_ERROR or SUDO_PLUGIN_SUDO_ERROR.

           status
                 Depending on the value of status_type, this value is
                 either ignored, the command's exit status as returned
                 by the wait(2) system call, the value of errno set by
                 the execve(2) system call, or the value of errno
                 resulting from an error in the sudo front end.

     accept
           int (*accept)(const char *plugin_name, unsigned int plugin_type,
               char * const command_info[], char * const run_argv[],
               char * const run_envp[], const char **errstr);

           The accept() function is called when a command or action is
           accepted by a policy or approval plugin.  The function
           arguments are as follows:

           plugin_name
                 The name of the plugin that accepted the command or
                 “sudo” for the sudo front-end.

           plugin_type
                 The type of plugin that accepted the command, currently
                 either SUDO_POLICY_PLUGIN, SUDO_POLICY_APPROVAL or
                 SUDO_FRONT_END.  The accept() function is called
                 multiple times--once for each policy or approval plugin
                 that succeeds and once for the sudo front-end.  When
                 called on behalf of the sudo front-end, command_info
                 may include information from an I/O logging plugin as
                 well.

                 Typically, an audit plugin is interested in either the
                 accept status from the sudo front-end or from the
                 various policy and approval plugins, but not both.  It
                 is possible for the policy plugin to accept a command
                 that is later rejected by an approval plugin, in which
                 case the audit plugin's accept() and reject() functions
                 will both be called.

           command_info
                 An optional vector of information describing the
                 command being run in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           run_argv
                 A NULL-terminated argument vector describing a command
                 that will be run in the same form as what would be
                 passed to the execve(2) system call.

           run_envp
                 The environment the command will be run with in the
                 form of a NULL-terminated vector of “name=value”
                 strings.

                 When parsing run_envp, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

           errstr
                 If the accept() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

     reject
           int (*reject)(const char *plugin_name, unsigned int plugin_type,
               const char *audit_msg, char * const command_info[],
               const char **errstr);

           The reject() function is called when a command or action is
           rejected by a plugin.  The function arguments are as follows:

           plugin_name
                 The name of the plugin that rejected the command.

           plugin_type
                 The type of plugin that rejected the command, currently
                 either SUDO_POLICY_PLUGIN, SUDO_APPROVAL_PLUGIN or
                 SUDO_IO_PLUGIN.

                 Unlike the accept() function, the reject() function is
                 not called on behalf of the sudo front-end.

           audit_msg
                 An optional string describing the reason the command
                 was rejected by the plugin.  If the plugin did not
                 provide a reason, audit_msg will be the NULL pointer.

           command_info
                 An optional vector of information describing the
                 command being run in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           errstr
                 If the reject() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

     error
           int (*error)(const char *plugin_name, unsigned int plugin_type,
               const char *audit_msg, char * const command_info[],
               const char **errstr);

           The error() function is called when a plugin or the sudo
           front-end returns an error.  The function arguments are as
           follows:

           plugin_name
                 The name of the plugin that generated the error or
                 “sudo” for the sudo front-end.

           plugin_type
                 The type of plugin that generated the error, or
                 SUDO_FRONT_END for the sudo front-end.

           audit_msg
                 An optional string describing the plugin error.  If the
                 plugin did not provide a description, audit_msg will be
                 the NULL pointer.

           command_info
                 An optional vector of information describing the
                 command being run in the form of “name=value” strings.
                 The vector is terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           errstr
                 If the error() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user
           specifies the -V option.  The plugin may display its version
           information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.  If the
           user requests detailed version information, the verbose flag
           will be set.

           Returns 1 on success, 0 on failure, -1 if a general error
           occurred, or -2 if there was a usage error, although the
           return value is currently ignored.

     register_hooks
           See the Policy plugin API section for a description of
           register_hooks.

     deregister_hooks
           See the Policy plugin API section for a description of
           deregister_hooks.

     event_alloc
           struct sudo_plugin_event * (*event_alloc)(void);

           The event_alloc() function is used to allocate a struct
           sudo_plugin_event which provides access to the main sudo
           event loop.  Unlike the other fields, the event_alloc()
           pointer is filled in by the sudo front end, not by the
           plugin.

           See the Event API section below for more information about
           events.

           NOTE: the event_alloc() function is only available starting
           with API version 1.17.  If the sudo front end doesn't support
           API version 1.17 or higher, event_alloc() will not be set.

   Approval plugin API
     struct approval_plugin {
     #define SUDO_APPROVAL_PLUGIN 4
         unsigned int type; /* always SUDO_APPROVAL_PLUGIN */
         unsigned int version; /* always SUDO_API_VERSION */
         int (*open)(unsigned int version, sudo_conv_t conversation,
             sudo_printf_t sudo_printf, char * const settings[],
             char * const user_info[], int submit_optind,
             char * const submit_argv[], char * const submit_envp[],
             char * const plugin_options[], const char **errstr);
         void (*close)(void);
         int (*check)(char * const command_info[], char * const run_argv[],
             char * const run_envp[], const char **errstr);
         int (*show_version)(int verbose);
     };

     An approval plugin can be used to apply extra constraints after a
     command has been accepted by the policy plugin.  Unlike the other
     plugin types, it does not remain open until the command completes.
     The plugin is opened before a call to check() or show_version() and
     closed shortly thereafter (audit plugin functions must be called
     before the plugin is closed).  Multiple approval plugins may be
     specified in sudo.conf(5).

     The approval_plugin struct has the following fields:

     type  The type field should always be set to SUDO_APPROVAL_PLUGIN.

     version
           The version field should be set to SUDO_API_VERSION.

           This allows sudo to determine the API version the plugin was
           built against.

     open
           int (*open)(unsigned int version, sudo_conv_t conversation,
               sudo_printf_t sudo_printf, char * const settings[],
               char * const user_info[], int submit_optind,
               char * const submit_argv[], char * const submit_envp[],
               char * const plugin_options[], const char **errstr);

           The approval open() function is run immediately before a call
           to the plugin's check() or show_version() functions.  It is
           only called if the version is being requested or if the
           policy plugin's check_policy() function has returned
           successfully.  It returns 1 on success, 0 on failure, -1 if a
           general error occurred, or -2 if there was a usage error.  In
           the latter case, sudo will print a usage message before it
           exits.  If an error occurs, the plugin may optionally call
           the conversation() or plugin_printf() function with
           SUDO_CONF_ERROR_MSG to present additional error information
           to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudo allows the plugin to
                 determine the major and minor version number of the
                 plugin API supported by sudo.

           conversation
                 A pointer to the conversation() function that can be
                 used by the plugin to interact with the user (see
                 Conversation API for details).  Returns 0 on success
                 and -1 on failure.

           plugin_printf
                 A pointer to a printf()-style function that may be used
                 to display informational or error messages (see
                 Conversation API for details).  Returns the number of
                 characters printed on success and -1 on failure.

           settings
                 A vector of user-supplied sudo settings in the form of
                 “name=value” strings.  The vector is terminated by a
                 NULL pointer.  These settings correspond to options the
                 user specified when running sudo.  As such, they will
                 only be present when the corresponding option has been
                 specified on the command line.

                 When parsing settings, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible settings.

           user_info
                 A vector of information about the user running the
                 command in the form of “name=value” strings.  The
                 vector is terminated by a NULL pointer.

                 When parsing user_info, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           submit_optind
                 The index into submit_argv that corresponds to the
                 first entry that is not a command line option.  If
                 submit_argv only consists of options, which may be the
                 case with the -l or -v options,
                 submit_argv[submit_optind] will evaluate to the NULL
                 pointer.

           submit_argv
                 The argument vector sudo was invoked with, including
                 all command line options.  The submit_optind argument
                 can be used to determine the end of the command line
                 options.

           submit_envp
                 The invoking user's environment in the form of a
                 NULL-terminated vector of “name=value” strings.

                 When parsing submit_envp, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

           plugin_options
                 Any (non-comment) strings immediately after the plugin
                 path are treated as arguments to the plugin.  These
                 arguments are split on a white space boundary and are
                 passed to the plugin in the form of a NULL-terminated
                 array of strings.  If no arguments were specified,
                 plugin_options will be the NULL pointer.

           errstr
                 If the open() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

     close
           void (*close)(void);

           The close() function is called after the approval plugin's
           check() or show_version() functions have been called.  It
           takes no arguments.  The close() function is typically used
           to perform plugin-specific cleanup, such as the freeing of
           memory objects allocated by the plugin.  If the plugin does
           not need to perform any cleanup, close() may be set to the
           NULL pointer.

     check
           int (*check)(char * const command_info[], char * const run_argv[],
               char * const run_envp[], const char **errstr);

           The approval check() function is run after the policy plugin
           check_policy() function and before any I/O logging plugins.
           If multiple approval plugins are loaded, they must all
           succeed for the command to be allowed.  It returns 1 on
           success, 0 on failure, -1 if a general error occurred, or -2
           if there was a usage error.  In the latter case, sudo will
           print a usage message before it exits.  If an error occurs,
           the plugin may optionally call the conversation() or
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present
           additional error information to the user.

           The function arguments are as follows:

           command_info
                 A vector of information describing the command being
                 run in the form of “name=value” strings.  The vector is
                 terminated by a NULL pointer.

                 When parsing command_info, the plugin should split on
                 the first equal sign (‘=’) since the name field will
                 never include one itself but the value might.

                 See the Policy plugin API section for a list of all
                 possible strings.

           run_argv
                 A NULL-terminated argument vector describing a command
                 that will be run in the same form as what would be
                 passed to the execve(2) system call.

           run_envp
                 The environment the command will be run with in the
                 form of a NULL-terminated vector of “name=value”
                 strings.

                 When parsing run_envp, the plugin should split on the
                 first equal sign (‘=’) since the name field will never
                 include one itself but the value might.

           errstr
                 If the open() function returns a value other than 1,
                 the plugin may store a message describing the failure
                 or error in errstr.  The sudo front end will then pass
                 this value to any registered audit plugins.  The string
                 stored in errstr must remain valid until the plugin's
                 close() function is called.

     show_version
           int (*show_version)(int verbose);

           The show_version() function is called by sudo when the user
           specifies the -V option.  The plugin may display its version
           information to the user via the conversation() or
           plugin_printf() function using SUDO_CONV_INFO_MSG.  If the
           user requests detailed version information, the verbose flag
           will be set.

           Returns 1 on success, 0 on failure, -1 if a general error
           occurred, or -2 if there was a usage error, although the
           return value is currently ignored.

   Signal handlers
     The sudo front end installs default signal handlers to trap common
     signals while the plugin functions are run.  The following signals
     are trapped by default before the command is executed:

     SIGALRM
     SIGHUP
     SIGINT
     SIGPIPE
     SIGQUIT
     SIGTERM
     SIGTSTP
     SIGUSR1
     SIGUSR2

     If a fatal signal is received before the command is executed, sudo
     will call the plugin's close() function with an exit status of 128
     plus the value of the signal that was received.  This allows for
     consistent logging of commands killed by a signal for plugins that
     log such information in their close() function.  An exception to
     this is SIGPIPE, which is ignored until the command is executed.

     A plugin may temporarily install its own signal handlers but must
     restore the original handler before the plugin function returns.

   Hook function API
     Beginning with plugin API version 1.2, it is possible to install
     hooks for certain functions called by the sudo front end.

     Currently, the only supported hooks relate to the handling of
     environment variables.  Hooks can be used to intercept attempts to
     get, set, or remove environment variables so that these changes can
     be reflected in the version of the environment that is used to
     execute a command.  A future version of the API will support
     hooking internal sudo front end functions as well.

     Hook structure

     Hooks in sudo are described by the following structure:

     typedef int (*sudo_hook_fn_t)();

     struct sudo_hook {
         unsigned int hook_version;
         unsigned int hook_type;
         sudo_hook_fn_t hook_fn;
         void *closure;
     };

     The sudo_hook structure has the following fields:

     hook_version
           The hook_version field should be set to SUDO_HOOK_VERSION.

     hook_type
           The hook_type field may be one of the following supported
           hook types:

           SUDO_HOOK_SETENV
                 The C library setenv(3) function.  Any registered hooks
                 will run before the C library implementation.  The
                 hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_setenv_t)(const char *name,
                    const char *value, int overwrite, void *closure);

                 If the registered hook does not match the typedef the
                 results are unspecified.

           SUDO_HOOK_UNSETENV
                 The C library unsetenv(3) function.  Any registered
                 hooks will run before the C library implementation.
                 The hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_unsetenv_t)(const char *name,
                    void *closure);

           SUDO_HOOK_GETENV
                 The C library getenv(3) function.  Any registered hooks
                 will run before the C library implementation.  The
                 hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_getenv_t)(const char *name,
                    char **value, void *closure);

                 If the registered hook does not match the typedef the
                 results are unspecified.

           SUDO_HOOK_PUTENV
                 The C library putenv(3) function.  Any registered hooks
                 will run before the C library implementation.  The
                 hook_fn field should be a function that matches the
                 following typedef:

                 typedef int (*sudo_hook_fn_putenv_t)(char *string,
                    void *closure);

                 If the registered hook does not match the typedef the
                 results are unspecified.

     hook_fn
           sudo_hook_fn_t hook_fn;

           The hook_fn field should be set to the plugin's hook
           implementation.  The actual function arguments will vary
           depending on the hook_type (see hook_type above).  In all
           cases, the closure field of struct sudo_hook is passed as the
           last function parameter.  This can be used to pass arbitrary
           data to the plugin's hook implementation.

           The function return value may be one of the following:

           SUDO_HOOK_RET_ERROR
                 The hook function encountered an error.

           SUDO_HOOK_RET_NEXT
                 The hook completed without error, go on to the next
                 hook (including the system implementation if
                 applicable).  For example, a getenv(3) hook might
                 return SUDO_HOOK_RET_NEXT if the specified variable was
                 not found in the private copy of the environment.

           SUDO_HOOK_RET_STOP
                 The hook completed without error, stop processing hooks
                 for this invocation.  This can be used to replace the
                 system implementation.  For example, a setenv hook that
                 operates on a private copy of the environment but
                 leaves environ unchanged.

     Note that it is very easy to create an infinite loop when hooking C
     library functions.  For example, a getenv(3) hook that calls the
     snprintf(3) function may create a loop if the snprintf(3)
     implementation calls getenv(3) to check the locale.  To prevent
     this, you may wish to use a static variable in the hook function to
     guard against nested calls.  For example:

     static int in_progress = 0; /* avoid recursion */
     if (in_progress)
         return SUDO_HOOK_RET_NEXT;
     in_progress = 1;
     ...
     in_progress = 0;
     return SUDO_HOOK_RET_STOP;

     Hook API Version Macros

     /* Hook API version major/minor */
     #define SUDO_HOOK_VERSION_MAJOR 1
     #define SUDO_HOOK_VERSION_MINOR 0
     #define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\
                                                   SUDO_HOOK_VERSION_MINOR)

     For getters and setters see the Policy plugin API.

   Event API
     When sudo runs a command, it uses an event loop to service signals
     and I/O.  Events may be triggered based on time, a file or socket
     descriptor becoming ready, or due to receipt of a signal.  Starting
     with API version 1.15, it is possible for a plugin to participate
     in this event loop by calling the event_alloc() function.

     Event structure

     Events are described by the following structure:

     typedef void (*sudo_plugin_ev_callback_t)(int fd, int what, void *closure);

     struct sudo_plugin_event {
         int (*set)(struct sudo_plugin_event *pev, int fd, int events,
             sudo_plugin_ev_callback_t callback, void *closure);
         int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
         int (*del)(struct sudo_plugin_event *pev);
         int (*pending)(struct sudo_plugin_event *pev, int events,
             struct timespec *ts);
         int (*fd)(struct sudo_plugin_event *pev);
         void (*setbase)(struct sudo_plugin_event *pev, void *base);
         void (*loopbreak)(struct sudo_plugin_event *pev);
         void (*free)(struct sudo_plugin_event *pev);
     };

     The sudo_plugin_event struct contains the following function
     pointers:

     set()
           int (*set)(struct sudo_plugin_event *pev, int fd, int events,
               sudo_plugin_ev_callback_t callback, void *closure);

           The set() function takes the following arguments:

           struct sudo_plugin_event *pev
                 A pointer to the struct sudo_plugin_event itself.

           fd    The file or socket descriptor for I/O-based events or
                 the signal number for signal events.  For time-based
                 events, fd must be -1.

           events
                 The following values determine what will trigger the
                 event callback:

                 SUDO_PLUGIN_EV_TIMEOUT
                       callback is run after the specified timeout
                       expires

                 SUDO_PLUGIN_EV_READ
                       callback is run when the file descriptor is
                       readable

                 SUDO_PLUGIN_EV_WRITE
                       callback is run when the file descriptor is
                       writable

                 SUDO_PLUGIN_EV_PERSIST
                       event is persistent and remains enabled until
                       explicitly deleted

                 SUDO_PLUGIN_EV_SIGNAL
                       callback is run when the specified signal is
                       received

                 The SUDO_PLUGIN_EV_PERSIST flag may be ORed with any of
                 the event types.  It is also possible to OR
                 SUDO_PLUGIN_EV_READ and SUDO_PLUGIN_EV_WRITE together
                 to run the callback when a descriptor is ready to be
                 either read from or written to.  All other event values
                 are mutually exclusive.

           sudo_plugin_ev_callback_t callback
                 typedef void (*sudo_plugin_ev_callback_t)(int fd, int what,
                     void *closure);

                 The function to call when an event is triggered.  The
                 callback() function is run with the following
                 arguments:

                 fd    The file or socket descriptor for I/O-based
                       events or the signal number for signal events.

                 what  The event type that triggered that callback.  For
                       events that have multiple event types (for
                       example SUDO_PLUGIN_EV_READ and
                       SUDO_PLUGIN_EV_WRITE) or have an associated
                       timeout, what can be used to determine why the
                       callback was run.

                 closure
                       The generic pointer that was specified in the
                       set() function.

           closure
                 A generic pointer that will be passed to the callback
                 function.

           The set() function returns 1 on success, and -1 if a error
           occurred.

     add()
           int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);

           The add() function adds the event pev to sudo's event loop.
           The event must have previously been initialized via the set()
           function.  If the timeout argument is not NULL, it should
           specify a (relative) timeout after which the event will be
           triggered if the main event criteria has not been met.  This
           is often used to implement an I/O timeout where the event
           will fire if a descriptor is not ready within a certain time
           period.  If the event is already present in the event loop,
           its timeout will be adjusted to match the new value, if any.

           The add() function returns 1 on success, and -1 if a error
           occurred.

     del()
           int (*del)(struct sudo_plugin_event *pev);

           The del() function deletes the event pev from sudo's event
           loop.  Deleted events can be added back via the add()
           function.

           The del() function returns 1 on success, and -1 if a error
           occurred.

     pending()
           int (*pending)(struct sudo_plugin_event *pev, int events,
               struct timespec *ts);

           The pending() function can be used to determine whether one
           or more events is pending.  The events argument specifies
           which events to check for.  See the set() function for a list
           of valid event types.  If SUDO_PLUGIN_EV_TIMEOUT is specified
           in events, the event has an associated timeout and the ts
           pointer is non-NULL, it will be filled in with the remaining
           time.

     fd()
           int (*fd)(struct sudo_plugin_event *pev);

           The fd() function returns the descriptor or signal number
           associated with the event pev.

     setbase()
           void (*setbase)(struct sudo_plugin_event *pev, void *base);

           The setbase() function sets the underlying event base for pev
           to the specified value.  This can be used to move an event
           created via event_alloc() to a new event loop allocated by
           sudo's event subsystem.  If base is NULL, pev's event base is
           reset to the default value, which corresponds to sudo's main
           event loop.  Using this function requires linking the plugin
           with the sudo_util library.  It is unlikely to be used
           outside of the sudoers plugin.

     loopbreak()
           void (*loopbreak)(struct sudo_plugin_event *pev);

           The loopbreak() function causes sudo's event loop to exit
           immediately and the running command to be terminated.

     free()
           void (*free)(struct sudo_plugin_event *pev);

           The free() function deletes the event pev from the event loop
           and frees the memory associated with it.

   Remote command execution
     The sudo front end does not support running remote commands.
     However, starting with sudo 1.8.8, the -h option may be used to
     specify a remote host that is passed to the policy plugin.  A
     plugin may also accept a runas_user in the form of “user@hostname”
     which will work with older versions of sudo.  It is anticipated
     that remote commands will be supported by executing a “helper”
     program.  The policy plugin should setup the execution environment
     such that the sudo front end will run the helper which, in turn,
     will connect to the remote host and run the command.

     For example, the policy plugin could utilize ssh to perform remote
     command execution.  The helper program would be responsible for
     running ssh with the proper options to use a private key or
     certificate that the remote host will accept and run a program on
     the remote host that would setup the execution environment
     accordingly.

     Note that remote sudoedit functionality must be handled by the
     policy plugin, not sudo itself as the front end has no knowledge
     that a remote command is being executed.  This may be addressed in
     a future revision of the plugin API.

   Conversation API
     If the plugin needs to interact with the user, it may do so via the
     conversation() function.  A plugin should not attempt to read
     directly from the standard input or the user's tty (neither of
     which are guaranteed to exist).  The caller must include a trailing
     newline in msg if one is to be printed.

     A printf()-style function is also available that can be used to
     display informational or error messages to the user, which is
     usually more convenient for simple messages where no use input is
     required.

     Conversation function structures

     The conversation function takes as arguments pointers to the
     following structures:

     struct sudo_conv_message {
     #define SUDO_CONV_PROMPT_ECHO_OFF  0x0001 /* do not echo user input */
     #define SUDO_CONV_PROMPT_ECHO_ON   0x0002 /* echo user input */
     #define SUDO_CONV_ERROR_MSG        0x0003 /* error message */
     #define SUDO_CONV_INFO_MSG         0x0004 /* informational message */
     #define SUDO_CONV_PROMPT_MASK      0x0005 /* mask user input */
     #define SUDO_CONV_PROMPT_ECHO_OK   0x1000 /* flag: allow echo if no tty */
     #define SUDO_CONV_PREFER_TTY       0x2000 /* flag: use tty if possible */
         int msg_type;
         int timeout;
         const char *msg;
     };

     #define SUDO_CONV_REPL_MAX      1023

     struct sudo_conv_reply {
         char *reply;
     };

     typedef int (*sudo_conv_callback_fn_t)(int signo, void *closure);
     struct sudo_conv_callback {
         unsigned int version;
         void *closure;
         sudo_conv_callback_fn_t on_suspend;
         sudo_conv_callback_fn_t on_resume;
     };

     Pointers to the conversation() and printf()-style functions are
     passed in to the plugin's open() function when the plugin is
     initialized.  The following type definitions can be used in the
     declaration of the open() function:

     typedef int (*sudo_conv_t)(int num_msgs,
         const struct sudo_conv_message msgs[],
         struct sudo_conv_reply replies[], struct sudo_conv_callback *callback);

     typedef int (*sudo_printf_t)(int msg_type, const char *fmt, ...);

     To use the conversation() function, the plugin must pass an array
     of sudo_conv_message and sudo_conv_reply structures.  There must be
     a struct sudo_conv_message and struct sudo_conv_reply for each
     message in the conversation, that is, both arrays must have the
     same number of elements.  Each struct sudo_conv_reply must have its
     reply member initialized to NULL.  The struct sudo_conv_callback
     pointer, if not NULL, should contain function pointers to be called
     when the sudo process is suspended and/or resumed during
     conversation input.  The on_suspend and on_resume functions are
     called with the signal that caused sudo to be suspended and the
     closure pointer from the struct sudo_conv_callback.  These
     functions should return 0 on success and -1 on error.  On error,
     the conversation will end and the conversation function will return
     a value of -1.  The intended use is to allow the plugin to release
     resources, such as locks, that should not be held indefinitely
     while suspended and then reacquire them when the process is
     resumed.  Note that the functions are not actually invoked from
     within a signal handler.

     The msg_type must be set to one of the following values:

     SUDO_CONV_PROMPT_ECHO_OFF
           Prompt the user for input with echo disabled; this is
           generally used for passwords.  The reply will be stored in
           the replies array, and it will never be NULL.

     SUDO_CONV_PROMPT_ECHO_ON
           Prompt the user for input with echo enabled.  The reply will
           be stored in the replies array, and it will never be NULL.

     SUDO_CONV_ERROR_MSG
           Display an error message.  The message is written to the
           standard error unless the SUDO_CONV_PREFER_TTY flag is set,
           in which case it is written to the user's terminal if
           possible.

     SUDO_CONV_INFO_MSG
           Display a message.  The message is written to the standard
           output unless the SUDO_CONV_PREFER_TTY flag is set, in which
           case it is written to the user's terminal if possible.

     SUDO_CONV_PROMPT_MASK
           Prompt the user for input but echo an asterisk character for
           each character read.  The reply will be stored in the replies
           array, and it will never be NULL.  This can be used to
           provide visual feedback to the user while reading sensitive
           information that should not be displayed.

     In addition to the above values, the following flag bits may also
     be set:

     SUDO_CONV_PROMPT_ECHO_OK
           Allow input to be read when echo cannot be disabled when the
           message type is SUDO_CONV_PROMPT_ECHO_OFF or
           SUDO_CONV_PROMPT_MASK.  By default, sudo will refuse to read
           input if the echo cannot be disabled for those message types.

     SUDO_CONV_PREFER_TTY
           When displaying a message via SUDO_CONV_ERROR_MSG or
           SUDO_CONV_INFO_MSG, try to write the message to the user's
           terminal.  If the terminal is unavailable, the standard error
           or standard output will be used, depending upon whether The
           user's terminal is always used when possible for input, this
           flag is only used for output.  SUDO_CONV_ERROR_MSG or
           SUDO_CONV_INFO_MSG was used.

     The timeout in seconds until the prompt will wait for no more
     input.  A zero value implies an infinite timeout.

     The plugin is responsible for freeing the reply buffer located in
     each struct sudo_conv_reply, if it is not NULL.  SUDO_CONV_REPL_MAX
     represents the maximum length of the reply buffer (not including
     the trailing NUL character).  In practical terms, this is the
     longest password sudo will support.

     The printf()-style function uses the same underlying mechanism as
     the conversation() function but only supports SUDO_CONV_INFO_MSG
     and SUDO_CONV_ERROR_MSG for the msg_type parameter.  It can be more
     convenient than using the conversation() function if no user reply
     is needed and supports standard printf() escape sequences.

     See the sample plugin for an example of the conversation() function
     usage.

   Plugin invocation order
     As of sudo 1.9.0, the plugin open() and close() functions are
     called in the following order:

     1.   audit open

     2.   policy open

     3.   approval open

     4.   approval close

     5.   I/O log open

     6.   command runs

     7.   command exits

     8.   I/O log close

     9.   policy close

     10.  audit close

     11.  sudo exits

     Prior to sudo 1.9.0, the I/O log close() function was called after
     the policy close() function.

   Sudoers group plugin API
     The sudoers plugin supports its own plugin interface to allow non-
     Unix group lookups.  This can be used to query a group source other
     than the standard Unix group database.  Two sample group plugins
     are bundled with sudo, group_file and system_group, are detailed in
     sudoers(5).  Third party group plugins include a QAS AD plugin
     available from Quest Software.

     A group plugin must declare and populate a sudoers_group_plugin
     struct in the global scope.  This structure contains pointers to
     the functions that implement plugin initialization, cleanup and
     group lookup.

     struct sudoers_group_plugin {
         unsigned int version;
         int (*init)(int version, sudo_printf_t sudo_printf,
             char *const argv[]);
         void (*cleanup)(void);
         int (*query)(const char *user, const char *group,
             const struct passwd *pwd);
     };

     The sudoers_group_plugin struct has the following fields:

     version
           The version field should be set to GROUP_API_VERSION.

           This allows sudoers to determine the API version the group
           plugin was built against.

     init
           int (*init)(int version, sudo_printf_t plugin_printf,
               char *const argv[]);

           The init() function is called after sudoers has been parsed
           but before any policy checks.  It returns 1 on success, 0 on
           failure (or if the plugin is not configured), and -1 if a
           error occurred.  If an error occurs, the plugin may call the
           plugin_printf() function with SUDO_CONF_ERROR_MSG to present
           additional error information to the user.

           The function arguments are as follows:

           version
                 The version passed in by sudoers allows the plugin to
                 determine the major and minor version number of the
                 group plugin API supported by sudoers.

           plugin_printf
                 A pointer to a printf()-style function that may be used
                 to display informational or error message to the user.
                 Returns the number of characters printed on success and
                 -1 on failure.

           argv  A NULL-terminated array of arguments generated from the
                 group_plugin option in sudoers.  If no arguments were
                 given, argv will be NULL.

     cleanup
           void (*cleanup)();

           The cleanup() function is called when sudoers has finished
           its group checks.  The plugin should free any memory it has
           allocated and close open file handles.

     query
           int (*query)(const char *user, const char *group,
               const struct passwd *pwd);

           The query() function is used to ask the group plugin whether
           user is a member of group.

           The function arguments are as follows:

           user  The name of the user being looked up in the external
                 group database.

           group
                 The name of the group being queried.

           pwd   The password database entry for user, if any.  If user
                 is not present in the password database, pwd will be
                 NULL.

     Group API Version Macros

     /* Sudoers group plugin version major/minor */
     #define GROUP_API_VERSION_MAJOR 1
     #define GROUP_API_VERSION_MINOR 0
     #define GROUP_API_VERSION ((GROUP_API_VERSION_MAJOR << 16) | \
                                GROUP_API_VERSION_MINOR)
     For getters and setters see the Policy plugin API.

PLUGIN API CHANGELOG         top

     The following revisions have been made to the Sudo Plugin API.

     Version 1.0
           Initial API version.

     Version 1.1 (sudo 1.8.0)
           The I/O logging plugin's open() function was modified to take
           the command_info list as an argument.

     Version 1.2 (sudo 1.8.5)
           The Policy and I/O logging plugins' open() functions are now
           passed a list of plugin parameters if any are specified in
           sudo.conf(5).

           A simple hooks API has been introduced to allow plugins to
           hook in to the system's environment handling functions.

           The init_session Policy plugin function is now passed a
           pointer to the user environment which can be updated as
           needed.  This can be used to merge in environment variables
           stored in the PAM handle before a command is run.

     Version 1.3 (sudo 1.8.7)
           Support for the exec_background entry has been added to the
           command_info list.

           The max_groups and plugin_dir entries were added to the
           settings list.

           The version() and close() functions are now optional.
           Previously, a missing version() or close() function would
           result in a crash.  If no policy plugin close() function is
           defined, a default close() function will be provided by the
           sudo front end that displays a warning if the command could
           not be executed.

           The sudo front end now installs default signal handlers to
           trap common signals while the plugin functions are run.

     Version 1.4 (sudo 1.8.8)
           The remote_host entry was added to the settings list.

     Version 1.5 (sudo 1.8.9)
           The preserve_fds entry was added to the command_info list.

     Version 1.6 (sudo 1.8.11)
           The behavior when an I/O logging plugin returns an error (-1)
           has changed.  Previously, the sudo front end took no action
           when the log_ttyin(), log_ttyout(), log_stdin(),
           log_stdout(), or log_stderr() function returned an error.

           The behavior when an I/O logging plugin returns 0 has
           changed.  Previously, output from the command would be
           displayed to the terminal even if an output logging function
           returned 0.

     Version 1.7 (sudo 1.8.12)
           The plugin_path entry was added to the settings list.

           The debug_flags entry now starts with a debug file path name
           and may occur multiple times if there are multiple plugin-
           specific Debug lines in the sudo.conf(5) file.

     Version 1.8 (sudo 1.8.15)
           The sudoedit_checkdir and sudoedit_follow entries were added
           to the command_info list.  The default value of
           sudoedit_checkdir was changed to true in sudo 1.8.16.

           The sudo conversation function now takes a pointer to a
           struct sudo_conv_callback as its fourth argument.  The
           sudo_conv_t definition has been updated to match.  The plugin
           must specify that it supports plugin API version 1.8 or
           higher to receive a conversation function pointer that
           supports this argument.

     Version 1.9 (sudo 1.8.16)
           The execfd entry was added to the command_info list.

     Version 1.10 (sudo 1.8.19)
           The umask entry was added to the user_info list.  The
           iolog_group, iolog_mode, and iolog_user entries were added to
           the command_info list.

     Version 1.11 (sudo 1.8.20)
           The timeout entry was added to the settings list.

     Version 1.12 (sudo 1.8.21)
           The change_winsize field was added to the io_plugin struct.

     Version 1.13 (sudo 1.8.26)
           The log_suspend field was added to the io_plugin struct.

     Version 1.14 (sudo 1.8.29)
           The umask_override entry was added to the command_info list.

     Version 1.15 (sudo 1.9.0)
           The cwd_optional entry was added to the command_info list.

           The event_alloc field was added to the policy_plugin and
           io_plugin structs.

           The errstr argument was added to the policy and I/O plugin
           functions which the plugin function can use to return an
           error string.  This string may be used by the audit plugin to
           report failure or error conditions set by the other plugins.

           The close() function is now is called regardless of whether
           or not a command was actually executed.  This makes it
           possible for plugins to perform cleanup even when a command
           was not run.

           SUDO_CONV_REPL_MAX has increased from 255 to 1023 bytes.

           Support for audit and approval plugins was added.

     Version 1.16 (sudo 1.9.3)
           Initial resource limit values were added to the user_info
           list.

           The cmnd_chroot and cmnd_cwd enties were added to the
           settings list.

     Version 1.17 (sudo 1.9.4)
           The event_alloc field was added to the audit_plugin and
           approval_plugin structs.

SEE ALSO         top

     sudo.conf(5), sudoers(5), sudo(8)

AUTHORS         top

     Many people have worked on sudo over the years; this version
     consists of code written primarily by:

           Todd C. Miller

     See the CONTRIBUTORS file in the sudo distribution
     (https://www.sudo.ws/contributors.html) for an exhaustive list of
     people who have contributed to sudo.

BUGS         top

     If you feel you have found a bug in sudo, please submit a bug
     report at https://bugzilla.sudo.ws/

SUPPORT         top

     Limited free support is available via the sudo-users mailing list,
     see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
     search the archives.

DISCLAIMER         top

     sudo is provided “AS IS” and any express or implied warranties,
     including, but not limited to, the implied warranties of
     merchantability and fitness for a particular purpose are
     disclaimed.  See the LICENSE file distributed with sudo or
     https://www.sudo.ws/license.html for complete details.

COLOPHON         top

     This page is part of the sudo (execute a command as another user)
     project.  Information about the project can be found at
     https://www.sudo.ws/.  If you have a bug report for this manual
     page, see ⟨https://bugzilla.sudo.ws/⟩.  This page was obtained from
     the project's upstream Git repository
     ⟨https://github.com/sudo-project/sudo⟩ on 2021-06-20.  (At that
     time, the date of the most recent commit that was found in the
     repository was 2021-06-19.)  If you discover any rendering problems
     in this HTML version of the page, or you believe there is a better
     or more up-to-date source for the page, or you have corrections or
     improvements to the information in this COLOPHON (which is not part
     of the original manual page), send a mail to man-pages@man7.org

Sudo 1.9.7p1                November 17, 2020               Sudo 1.9.7p1