The key identifiers passed to or returned from keyctl are, in
general, positive integers. There are, however, some special values
with special meanings that can be passed as arguments:
(*) No key: 0
(*) Thread keyring: @t or -1
Each thread may have its own keyring. This is searched first, before
all others. The thread keyring is replaced by (v)fork, exec and
(*) Process keyring: @p or -2
Each process (thread group) may have its own keyring. This is shared
between all members of a group and will be searched after the thread
keyring. The process keyring is replaced by (v)fork and exec.
(*) Session keyring: @s or -3
Each process subscribes to a session keyring that is inherited across
(v)fork, exec and clone. This is searched after the process keyring.
Session keyrings can be named and an extant keyring can be joined in
place of a process's current session keyring.
(*) User specific keyring: @u or -4
This keyring is shared between all the processes owned by a
particular user. It isn't searched directly, but is normally linked
to from the session keyring.
(*) User default session keyring: @us or -5
This is the default session keyring for a particular user. Login
processes that change to a particular user will bind to this session
until another session is set.
(*) Group specific keyring: @g or -6
This is a place holder for a group specific keyring, but is not
actually implemented yet in the kernel.
(*) Assumed request_key authorisation key: @a or -7
This selects the authorisation key provided to the request_key()
helper to permit it to access the callers keyrings and instantiate
the target key.
(*) Keyring by name: %:<name>
A named keyring. This will be searched for in the process's keyrings
and in /proc/keys.
(*) Key by name: %<type>:<name>
A named key of the given type. This will be searched for in the
process's keyrings and in /proc/keys.
Any non-ambiguous shortening of a command name may be used in lieu of
the full command name. This facility should not be used in scripting
as new commands may be added in future that then cause ambiguity.
(*) Display the package version numberkeyctl --version
This command prints the package version number and build date and
keyctl from keyutils-1.5.3 (Built 2011-08-24)
(*) Show process keyringskeyctl show [-x] [<keyring>]
By default this command recursively shows what keyrings a process is
subscribed to and what keys and keyrings they contain. If a keyring
is specified then that keyring will be dumped instead. If -x is
specified then the keyring IDs will be dumped in hex instead of
(*) Add a key to a keyringkeyctl add <type> <desc> <data> <keyring>
keyctl padd <type> <desc> <keyring>
This command creates a key of the specified type and description;
instantiates it with the given data and attaches it to the specified
keyring. It then prints the new key's ID on stdout:
testbox>keyctl add user mykey stuff @u
The padd variant of the command reads the data from stdin rather than
taking it from the command line:
testbox>echo -n stuff | keyctl padd user mykey @u
(*) Request a keykeyctl request <type> <desc> [<dest_keyring>]
keyctl request2 <type> <desc> <info> [<dest_keyring>]
keyctl prequest2 <type> <desc> [<dest_keyring>]
These three commands request the lookup of a key of the given type
and description. The process's keyrings will be searched, and if a
match is found the matching key's ID will be printed to stdout; and
if a destination keyring is given, the key will be added to that
If there is no key, the first command will simply return the error
ENOKEY and fail. The second and third commands will create a partial
key with the type and description, and call out to /sbin/request-key
with that key and the extra information supplied. This will then
attempt to instantiate the key in some manner, such that a valid key
The third command is like the second, except that the callout
information is read from stdin rather than being passed on the
If a valid key is obtained, the ID will be printed and the key
attached as if the original search had succeeded.
If there wasn't a valid key obtained, a temporary negative key will
be attached to the destination keyring if given and the error
"Requested key not available" will be given.
testbox>keyctl request2 user debug:hello wibble
testbox>echo -n wibble | keyctl prequest2 user debug:hello
testbox>keyctl request user debug:hello
(*) Update a keykeyctl update <key> <data>
keyctl pupdate <key>
This command replaces the data attached to a key with a new set of
data. If the type of the key doesn't support update then error
"Operation not supported" will be returned.
testbox>keyctl update 23 zebra
The pupdate variant of the command reads the data from stdin rather
than taking it from the command line:
testbox>echo -n zebra | keyctl pupdate 23
(*) Create a keyringkeyctl newring <name> <keyring>
This command creates a new keyring of the specified name and attaches
it to the specified keyring. The ID of the new keyring will be
printed to stdout if successful.
testbox>keyctl newring squelch @us
(*) Revoke a keykeyctl revoke <key>
This command marks a key as being revoked. Any further operations on
that key (apart from unlinking it) will return error "Key has been
testbox>keyctl revoke 26
testbox>keyctl describe 26
keyctl_describe: Key has been revoked
(*) Clear a keyringkeyctl clear <keyring>
This command unlinks all the keys attached to the specified keyring.
Error "Not a directory" will be returned if the key specified is not
testbox>keyctl clear 27
(*) Link a key to a keyringkeyctl link <key> <keyring>
This command makes a link from the key to the keyring if there's
enough capacity to do so. Error "Not a directory" will be returned if
the destination is not a keyring. Error "Permission denied" will be
returned if the key doesn't have link permission or the keyring
doesn't have write permission. Error "File table overflow" will be
returned if the keyring is full. Error "Resource deadlock avoided"
will be returned if an attempt was made to introduce a recursive
testbox>keyctl link 23 27
testbox>keyctl link 27 27
keyctl_link: Resource deadlock avoided
(*) Unlink a key from a keyring or the session keyring treekeyctl unlink <key> [<keyring>]
If the keyring is specified, this command removes a link to the key
from the keyring. Error "Not a directory" will be returned if the
destination is not a keyring. Error "Permission denied" will be
returned if the keyring doesn't have write permission. Error "No such
file or directory" will be returned if the key is not linked to by
If the keyring is not specified, this command performs a depth-first
search of the session keyring tree and removes all the links to the
nominated key that it finds (and that it is permitted to remove). It
prints the number of successful unlinks before exiting.
testbox>keyctl unlink 23 27
(*) Search a keyringkeyctl search <keyring> <type> <desc> [<dest_keyring>]
This command non-recursively searches a keyring for a key of a
particular type and description. If found, the ID of the key will be
printed on stdout and the key will be attached to the destination
keyring if present. Error "Requested key not available" will be
returned if the key is not found.
testbox>keyctl search @us user debug:hello
testbox>keyctl search @us user debug:bye
keyctl_search: Requested key not available
(*) Read a keykeyctl read <key>
keyctl pipe <key>
keyctl print <key>
These commands read the payload of a key. "read" prints it on stdout
as a hex dump, "pipe" dumps the raw data to stdout and "print" dumps
it to stdout directly if it's entirely printable or as a hexdump
preceded by ":hex:" if not.
If the key type does not support reading of the payload, then error
"Operation not supported" will be returned.
testbox>keyctl read 26
1 bytes of data in key:
testbox>keyctl print 26
testbox>keyctl pipe 26
(*) List a keyringkeyctl list <keyring>
keyctl rlist <keyring>
These commands list the contents of a key as a keyring. "list" pretty
prints the contents and "rlist" just produces a space-separated list
of key IDs.
No attempt is made to check that the specified keyring is a keyring.
testbox>keyctl list @us
2 keys in keyring:
22: vrwsl---------- 4043 -1 keyring: _uid.4043
23: vrwsl---------- 4043 4043 user: debug:hello
testbox>keyctl rlist @us
(*) Describe a keykeyctl describe <keyring>
keyctl rdescribe <keyring> [sep]
These commands fetch a description of a keyring. "describe" pretty
prints the description in the same fashion as the "list" command;
"rdescribe" prints the raw data returned from the kernel.
testbox>keyctl describe @us
-5: vrwsl---------- 4043 -1 keyring: _uid_ses.4043
testbox>keyctl rdescribe @us
The raw string is "<type>;<uid>;<gid>;<perms>;<description>", where
uid and gid are the decimal user and group IDs, perms is the
permissions mask in hex, type and description are the type name and
description strings (neither of which will contain semicolons).
(*) Change the access controls on a keykeyctl chown <key> <uid>
keyctl chgrp <key> <gid>
These two commands change the UID and GID associated with evaluating
a key's permissions mask. The UID also governs which quota a key is
taken out of.
The chown command is not currently supported; attempting it will earn
the error "Operation not supported" at best.
For non-superuser users, the GID may only be set to the process's GID
or a GID in the process's groups list. The superuser may set any GID
testbox>sudo keyctl chown 27 0
keyctl_chown: Operation not supported
testbox>sudo keyctl chgrp 27 0
(*) Set the permissions mask on a keykeyctl setperm <key> <mask>
This command changes the permission control mask on a key. The mask
may be specified as a hex number if it begins "0x", an octal number
if it begins "0" or a decimal number otherwise.
The hex numbers are a combination of:
Possessor UID GID Other Permission Granted
======== ======== ======== ======== ==================
01000000 00010000 00000100 00000001 View
02000000 00020000 00000200 00000002 Read
04000000 00040000 00000400 00000004 Write
08000000 00080000 00000800 00000008 Search
10000000 00100000 00001000 00000010 Link
20000000 00200000 00002000 00000020 Set Attribute
3f000000 003f0000 00003f00 0000003f All
View permits the type, description and other parameters of a key to
Read permits the payload (or keyring list) to be read if supported by
Write permits the payload (or keyring list) to be modified or
Search on a key permits it to be found when a keyring to which it is
linked is searched.
Link permits a key to be linked to a keyring.
Set Attribute permits a key to have its owner, group membership,
permissions mask and timeout changed.
testbox>keyctl setperm 27 0x1f1f1f00
(*) Start a new session with fresh keyringskeyctl sessionkeyctl session - [<prog> <arg1> <arg2> ...]
keyctl session <name> [<prog> <arg1> <arg2> ...]
These commands join or create a new keyring and then run a shell or
other program with that keyring as the session key.
The variation with no arguments just creates an anonymous session
keyring and attaches that as the session keyring; it then exec's
The variation with a dash in place of a name creates an anonymous
session keyring and attaches that as the session keyring; it then
exec's the supplied command, or $SHELL if one isn't supplied.
The variation with a name supplied creates or joins the named keyring
and attaches that as the session keyring; it then exec's the supplied
command, or $SHELL if one isn't supplied.
testbox>keyctl rdescribe @s
Joined session keyring: 28
testbox>keyctl rdescribe @s
testbox>keyctl session -
Joined session keyring: 29
testbox>keyctl rdescribe @s
testbox>keyctl session - keyctl rdescribe @s
Joined session keyring: 30
testbox>keyctl session fish
Joined session keyring: 34
testbox>keyctl rdescribe @s
testbox>keyctl session fish keyctl rdesc @s
Joined session keyring: 35
(*) Instantiate a keykeyctl instantiate <key> <data> <keyring>
keyctl pinstantiate <key> <keyring>
keyctl negate <key> <timeout> <keyring>
keyctl reject <key> <timeout> <error> <keyring>
These commands are used to attach data to a partially set up key (as
created by the kernel and passed to /sbin/request-key).
"instantiate" marks a key as being valid and attaches the data as the
payload. "negate" and "reject" mark a key as invalid and sets a
timeout on it so that it'll go away after a while. This prevents a
lot of quickly sequential requests from slowing the system down
overmuch when they all fail, as all subsequent requests will then
fail with error "Requested key not found" (if negated) or the
specified error (if rejected) until the negative key has expired.
Reject's error argument can either be a UNIX error number or one of
'rejected', 'expired' or 'revoked'.
The newly instantiated key will be attached to the specified keyring.
These commands may only be run from the program run by request-key -
a special authorisation key is set up by the kernel and attached to
the request-key's session keyring. This special key is revoked once
the key to which it refers has been instantiated one way or another.
testbox>keyctl instantiate $1 "Debug $3" $4
testbox>keyctl negate $1 30 $4
testbox>keyctl reject $1 30 64 $4
The pinstantiate variant of the command reads the data from stdin
rather than taking it from the command line:
testbox>echo -n "Debug $3" | keyctl pinstantiate $1 $4
(*) Set the expiry time on a keykeyctl timeout <key> <timeout>
This command is used to set the timeout on a key, or clear an
existing timeout if the value specified is zero. The timeout is given
as a number of seconds into the future.
testbox>keyctl timeout $1 45
(*) Retrieve a key's security contextkeyctl security <key>
This command is used to retrieve a key's LSM security context. The
label is printed on stdout.
testbox>keyctl security @s
(*) Give the parent process a new session keyringkeyctl new_session
This command is used to give the invoking process (typically a shell)
a new session keyring, discarding its old session keyring.
testbox> keyctl session foo
Joined session keyring: 723488146
testbox> keyctl show
-3 --alswrv 0 0 keyring: foo
testbox> keyctl new_session
testbox> keyctl show
-3 --alswrv 0 0 keyring: _ses
Note that this affects the parent of the process that invokes the
system call, and so may only affect processes with matching
credentials. Furthermore, the change does not take effect till the
parent process next transitions from kernel space to user space -
typically when the wait() system call returns.
(*) Remove dead keys from the session keyring treekeyctl reap
This command performs a depth-first search of the caller's session
keyring tree and attempts to unlink any key that it finds that is
inaccessible due to expiry, revocation, rejection or negation. It
does not attempt to remove live keys that are unavailable simply due
to a lack of granted permission.
A key that is designated reapable will only be removed from a keyring
if the caller has Write permission on that keyring, and only keyrings
that grant Search permission to the caller will be searched.
The command prints the number of keys reaped before it exits. If the
-v flag is passed then the reaped keys are listed as they're being
reaped, together with the success or failure of the unlink.
(*) Remove matching keys from the session keyring treekeyctl purge <type>
keyctl purge [-i] [-p] <type> <desc>
keyctl purge -s <type> <desc>
These commands perform a depth-first search to find matching keys in
the caller's session keyring tree and attempts to unlink them. The
number of keys successfully unlinked is printed at the end.
The keyrings must grant Read and View permission to the caller to be
searched, and the keys to be removed must also grant View permission.
Keys can only be removed from keyrings that grant Write permission.
The first variant purges all keys of the specified type.
The second variant purges all keys of the specified type that also
match the given description literally. The -i flag allows a case-
independent match and the -p flag allows a prefix match.
The third variant purges all keys of the specified type and matching
description using the key type's comparator in the kernel to match
the description. This permits the key type to match a key with a
variety of descriptions.
(*) Get persistent keyringkeyctl get_persistent <keyring> [<uid>]
This command gets the persistent keyring for either the current UID
or the specified UID and attaches it to the nominated keyring. The
persistent keyring's ID will be printed on stdout.
The kernel will create the keyring if it doesn't exist and every time
this command is called, will reset the expiration timeout on the
keyring to the value in:
(by default three days). Should the timeout be reached, the
persistent keyring will be removed and everything it pins can then be
If a UID other than the process's real or effective UIDs is
specified, then an error will be given if the process does not have
the CAP_SETUID capability.
(*) Compute a Diffie-Hellman shared secret or public keykeyctl dh_compute <private> <prime> <base>
This command computes either a Diffie-Hellman shared secret or the
public key corresponding to the provided private key using the
payloads of three keys. The computation is:
base ^ private (mod prime)
The three inputs must be user keys with read permission. If the
provided base key contains the shared generator value, the public key
will be computed. If the provided base key contains the remote
public key value, the shared secret will be computed.
The result is printed to stdout as a hex dump.
testbox>keyctl dh_compute $1 $2 $3
8 bytes of data in result:
There are a number of common errors returned by this program:
"Not a directory" - a key wasn't a keyring.
"Requested key not found" - the looked for key isn't available.
"Key has been revoked" - a revoked key was accessed.
"Key has expired" - an expired key was accessed.
"Permission denied" - permission was denied by a UID/GID/mask
This page is part of the keyutils (key management utilities) project.
Information about the project can be found at [unknown -- if you
know, please contact firstname.lastname@example.org] If you have a bug report for
this manual page, send it to email@example.com. This page was
obtained from the project's upstream Git repository
on 2017-03-13. 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 firstname.lastname@example.org
Linux 20 Feb 2014 KEYCTL(1)