SUDO_LOGSRVD(8) BSD System Manager's Manual SUDO_LOGSRVD(8)
NAME
sudo_logsrvd — sudo event and I/O log server
SYNOPSIS
sudo_logsrvd [-hnV] [-f file] [-R percentage]
DESCRIPTION
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 de-
fault, 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 re-
played 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 dis-
tinguish 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 re-
ceives 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 Author-
ity (CA), or a private CA can be used. Instructions for creating a pri-
vate 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.
FILES
/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
EXAMPLES
Creating self-signed certificates
Unless you are using certificates signed by a well-known Certificate Au-
thority (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 certifi-
cates.
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 ad-
just 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 Widgits 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 cre-
ated 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 cer-
tificate. 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 Widgits 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 cer-
tificate for use with sudo_logsrvd.
To generate a client certificate, repeat the process above using a dif-
ferent 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.
SEE ALSO
sudo.conf(5), sudo_logsrvd.conf(5), sudoers(5), sudo(8), sudo_sendlog(8),
sudoreplay(8)
AUTHORS
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 peo-
ple who have contributed to sudo.
BUGS
If you believe you have found a bug in sudo_logsrvd, you can submit a bug
report at https://bugzilla.sudo.ws/
SUPPORT
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
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 com-
plete details.
Sudo 1.9.13p3 January 16, 2023 Sudo 1.9.13p3
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