Ensure Logs Sent To Remote Host
Description
To configure rsyslog to send logs to a remote log server,
open /etc/rsyslog.conf and read and understand the last section of the file,
which describes the multiple directives necessary to activate remote
logging.
Along with these other directives, the system can be configured
to forward its logs to a particular log server by
adding or correcting one of the following lines,
substituting appropriately.
The choice of protocol depends on the environment of the system;
although TCP and RELP provide more reliable message delivery,
they may not be supported in all environments.
To use UDP for log message delivery:
To use TCP for log message delivery:
To use RELP for log message delivery:
There must be a resolvable DNS CNAME or Alias record set to "" for logs to be sent correctly to the centralized logging utility.
Rationale
A log server (loghost) receives syslog messages from one or more
systems. This data can be used as an additional log source in the event a
system is compromised and its local logs are suspect. Forwarding log messages
to a remote loghost also provides system administrators with a centralized
place to view the status of multiple hosts within the enterprise.
Shell script
The following script can be run on the host to remediate the issue.
# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then
rsyslog\_remote\_loghost\_address=''
# Strip any search characters in the key arg so that the key can be replaced without
# adding any search characters to the config file.
stripped\_key=$(sed 's/[\^=\$,;+]\*//g' <<< "^\\*\.\\*")
# shellcheck disable=SC2059
printf -v formatted\_output "%s %s" "$stripped\_key" "@@$rsyslog\_remote\_loghost\_address"
# If the key exists, change it. Otherwise, add it to the config\_file.
# We search for the key string followed by a word boundary (matched by \>),
# so if we search for 'setting', 'setting2' won't match.
if LC\_ALL=C grep -q -m 1 -i -e "^\\*\.\\*\\>" "/etc/rsyslog.conf"; then
escaped\_formatted\_output=$(sed -e 's|/|\\/|g' <<< "$formatted\_output")
LC\_ALL=C sed -i --follow-symlinks "s/^\\*\.\\*\\>.\*/$escaped\_formatted\_output/gi" "/etc/rsyslog.conf"
else
if [[ -s "/etc/rsyslog.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/rsyslog.conf" || true)" ]]; then
LC\_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/rsyslog.conf"
fi
printf '%s\n' "$formatted\_output" >> "/etc/rsyslog.conf"
fi
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Warning
It is important to configure queues in case the client is sending log
messages to a remote server. If queues are not configured,
the system will stop functioning when the connection
to the remote server is not available. Please consult Rsyslog
documentation for more information about configuration of queues. The
example configuration which should go into /etc/rsyslog.conf
can look like the following lines:
$ActionQueueType LinkedList
$ActionQueueFileName queuefilename
$ActionQueueMaxDiskSpace 1g
$ActionQueueSaveOnShutdown on
$ActionResumeRetryCount -1
