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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | FILES | EXAMPLES | SEE ALSO | AUTHORS | BUGS | SUPPORT | DISCLAIMER | COLOPHON |
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SUDO_LOGSRVD(8) System Manager's Manual SUDO_LOGSRVD(8)
sudo_logsrvd — sudo event and I/O log server
sudo_logsrvd [-hnV] [-f file] [-R percentage]
sudo_logsrvd is a high-performance log server that accepts event
and I/O logs from sudo. It can be used to implement centralized
logging of sudo logs. The server has two modes of operation:
local and relay. By default, sudo_logsrvd stores the logs locally
but it can also be configured to relay them to another server that
supports the sudo_logsrv.proto(5) protocol.
When not relaying, event log entries may be logged either via
syslog(3) or to a local file. I/O Logs stored locally by
sudo_logsrvd can be replayed via the sudoreplay(8) utility in the
same way as logs generated directly by the sudoers plugin.
The server also supports restarting interrupted log transfers. To
distinguish completed I/O logs from incomplete ones, the I/O log
timing file is set to be read-only when the log is complete.
Configuration parameters for sudo_logsrvd may be specified in the
sudo_logsrvd.conf(5) file or the file specified via the -f option.
sudo_logsrvd rereads its configuration file when it receives
SIGHUP and writes server state to the debug file (if one is
configured) when it receives SIGUSR1.
The options are as follows:
-f file, --file=file
Read configuration from file instead of the default,
/etc/sudo_logsrvd.conf.
-h, --help
Display a short help message to the standard output and
exit.
-n, --no-fork
Run sudo_logsrvd in the foreground instead of detaching
from the terminal and becoming a daemon.
-R percentage, --random-drop=percentage
For each message, there is a percentage chance that the
server will drop the connection. This is only intended
for debugging the ability of a client to restart a
connection.
-V, --version
Print the sudo_logsrvd version and exit.
Securing server connections
The I/O log data sent to sudo_logsrvd may contain sensitive
information such as passwords and should be secured using
Transport Layer Security (TLS). Doing so requires having a signed
certificate on the server and, if tls_checkpeer is enabled in
sudo_logsrvd.conf(5), a signed certificate on the client as well.
The certificates can either be signed by a well-known Certificate
Authority (CA), or a private CA can be used. Instructions for
creating a private CA are included below in the “EXAMPLES”
section.
Debugging sudo_logsrvd
sudo_logsrvd supports a flexible debugging framework that is
configured via Debug lines in the sudo.conf(5) file.
For more information on configuring sudo.conf(5), refer to its
manual.
/etc/sudo.conf Sudo front-end configuration
/etc/sudo_logsrvd.conf Sudo log server configuration file
/var/log/sudo_logsrvd/incoming
Directory where new journals are stored
when the store_first relay setting is
enabled.
/var/log/sudo_logsrvd/outgoing
Directory where completed journals are
stored when the store_first relay
setting is enabled.
/var/log/sudo-io Default I/O log file location
/run/sudo/sudo_logsrvd.pid
Process ID file for sudo_logsrvd
Creating self-signed certificates
Unless you are using certificates signed by a well-known
Certificate Authority (or a local enterprise CA), you will need to
create your own CA that can sign the certificates used by
sudo_logsrvd, sudo_sendlog, and the sudoers plugin. The following
steps use the openssl(1) command to create keys and certificates.
Initial setup
First, we need to create a directory structure to store the files
for the CA. We'll create a new directory hierarchy in
/etc/ssl/sudo for this purpose.
# mkdir /etc/ssl/sudo
# cd /etc/ssl/sudo
# mkdir certs csr newcerts private
# chmod 700 private
# touch index.txt
# echo 1000 > serial
The serial and index.txt files are used to keep track of signed
certificates.
Next, we need to make a copy of the openssl.conf file and
customize it for our new CA. The path to openssl.cnf is system-
dependent but /etc/ssl/openssl.cnf is the most common location.
You will need to adjust the example below if it has a different
location on your system.
# cp /etc/ssl/openssl.cnf .
Now edit the openssl.cnf file in the current directory and make
sure it contains “ca”, “CA_default”, “v3_ca”, and “usr_cert”
sections. Those sections should include at least the following
settings:
[ ca ]
default_ca = CA_default
[ CA_default ]
dir = /etc/ssl/sudo
certs = $dir/certs
database = $dir/index.txt
certificate = $dir/cacert.pem
serial = $dir/serial
[ v3_ca ]
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid:always,issuer
basicConstraints = critical,CA:true
keyUsage = cRLSign, keyCertSign
[ usr_cert ]
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, \
keyEncipherment
subjectKeyIdentifier = hash
authorityKeyIdentifier = keyid,issuer
If your openssl.conf file already has a “CA_default” section, you
may only need to modify the “dir” setting and enable the
“keyUsage” settings if they are commented out.
Creating the CA key and certificate
In order to create and sign our own certificates, we need to
create a private key and a certificate for the root of the CA.
First, create the private key and protect it with a pass phrase:
# openssl genrsa -aes256 -out private/cakey.pem 4096
# chmod 400 private/cakey.pem
Next, generate the root certificate, using appropriate values for
the site-specific fields:
# openssl req -config openssl.cnf -key private/cakey.pem \
-new -x509 -days 7300 -sha256 -extensions v3_ca \
-out cacert.pem
Enter pass phrase for private/cakey.pem:
You are about to be asked to enter information that will be
incorporated into your certificate request.
What you are about to enter is what is called a Distinguished Name
or a DN.
There are quite a few fields but you can leave some blank.
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:Colorado
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgets Pty Ltd]:sudo
Organizational Unit Name (eg, section) []:sudo Certificate Authority
Common Name (e.g., server FQDN or YOUR name) []:sudo Root CA
Email Address []:
# chmod 444 cacert.pem
Finally, verify the root certificate:
# openssl x509 -noout -text -in cacert.pem
Creating and signing certificates
The server and client certificates will be signed by the
previously created root CA. Usually, the root CA is not used to
sign server/client certificates directly. Instead, intermediate
certificates are created and signed with the root CA and the
intermediate certs are used to sign CSRs (Certificate Signing
Request). In this example we'll skip this part for simplicity's
sake and sign the CSRs with the root CA.
First, generate the private key without a pass phrase.
# openssl genrsa -out private/logsrvd_key.pem 2048
# chmod 400 private/logsrvd_key.pem
Next, create a certificate signing request (CSR) for the server's
certificate. The organization name must match the name given in
the root certificate. The common name should be either the
server's IP address or a fully qualified domain name.
# openssl req -config openssl.cnf -key private/logsrvd_key.pem -new \
-sha256 -out csr/logsrvd_csr.pem
Enter pass phrase for private/logsrvd_key.pem:
You are about to be asked to enter information that will be
incorporated into your certificate request.
What you are about to enter is what is called a Distinguished Name
or a DN.
There are quite a few fields but you can leave some blank.
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:Colorado
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgets Pty Ltd]:sudo
Organizational Unit Name (eg, section) []:sudo log server
Common Name (e.g., server FQDN or YOUR name) []:logserver.example.com
Email Address []:
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
Now sign the CSR that was just created:
# openssl ca -config openssl.cnf -days 375 -notext -md sha256 \
-in csr/logsrvd_csr.pem -out certs/logsrvd_cert.pem
Using configuration from openssl.cnf
Enter pass phrase for ./private/cakey.pem:
Check that the request matches the signature
Signature ok
Certificate Details:
Serial Number: 4096 (0x1000)
Validity
Not Before: Nov 11 14:05:05 2019 GMT
Not After : Nov 20 14:05:05 2020 GMT
Subject:
countryName = US
stateOrProvinceName = Colorado
organizationName = sudo
organizationalUnitName = sudo log server
commonName = logserve.example.com
X509v3 extensions:
X509v3 Basic Constraints:
CA:FALSE
X509v3 Key Usage:
Digital Signature, Non Repudiation, Key Encipherment
X509v3 Subject Key Identifier:
4C:50:F9:D0:BE:1A:4C:B2:AC:90:76:56:C7:9E:16:AE:E6:9E:E5:B5
X509v3 Authority Key Identifier:
keyid:D7:91:24:16:B1:03:06:65:1A:7A:6E:CF:51:E9:5C:CB:7A:95:3E:0C
Certificate is to be certified until Nov 20 14:05:05 2020 GMT (375 days)
Sign the certificate? [y/n]:y
1 out of 1 certificate requests certified, commit? [y/n]y
Write out database with 1 new entries
Data Base Updated
Finally, verify the new certificate:
# openssl verify -CAfile cacert.pem certs/logsrvd_cert.pem
certs/logsrvd_cert.pem: OK
The /etc/ssl/sudo/certs directory now contains a signed and
verified certificate for use with sudo_logsrvd.
To generate a client certificate, repeat the process above using a
different file name.
Configuring sudo_logsrvd to use TLS
To use TLS for client/server communication, both sudo_logsrvd and
the sudoers plugin need to be configured to use TLS. Configuring
sudo_logsrvd for TLS requires the following settings, assuming the
same path names used earlier:
# Listen on port 30344 for TLS connections to any address.
listen_address = *:30344(tls)
# Path to the certificate authority bundle file in PEM format.
tls_cacert = /etc/ssl/sudo/cacert.pem
# Path to the server's certificate file in PEM format.
tls_cert = /etc/ssl/sudo/certs/logsrvd_cert.pem
# Path to the server's private key file in PEM format.
tls_key = /etc/ssl/sudo/private/logsrvd_key.pem
The root CA cert (cacert.pem) must be installed on the system
running sudo_logsrvd. If peer authentication is enabled on the
client, a copy of cacert.pem must be present on the client system
too.
sudo.conf(5), sudo_logsrv.proto(5), sudo_logsrvd.conf(5),
sudoers(5), sudo(8), sudo_sendlog(8), sudoreplay(8)
Many people have worked on sudo over the years; this version
consists of code written primarily by:
Todd C. Miller
See the CONTRIBUTORS.md file in the sudo distribution
(https://www.sudo.ws/about/contributors/) for an exhaustive list
of people who have contributed to sudo.
If you believe you have found a bug in sudo_logsrvd, you can
either file a bug report in the sudo bug database,
https://bugzilla.sudo.ws/, or open an issue at
https://github.com/sudo-project/sudo/issues. If you would prefer
to use email, messages may be sent to the sudo-workers mailing
list, https://www.sudo.ws/mailman/listinfo/sudo-workers (public)
or <sudo@sudo.ws> (private).
Please not report security vulnerabilities through public GitHub
issues, Bugzilla or mailing lists. Instead, report them via email
to <Todd.Miller@sudo.ws>. You may encrypt your message with PGP
if you would like, using the key found at
https://www.sudo.ws/dist/PGPKEYS.
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.
sudo_logsrvd 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.md file distributed with sudo or
https://www.sudo.ws/about/license/ for complete details.
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 2025-02-02. (At that
time, the date of the most recent commit that was found in the
repository was 2025-01-21.) 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 1.9.16p2 July 14, 2024 SUDO_LOGSRVD(8)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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