3.6.1.9 Configuring SSH - set LogLevel to INFO or VERBOSE

Information

The INFO parameter specifices that record login and logout activity will be logged.

Rationale:

SSH provides several logging levels with varying amounts of verbosity. DEBUG is specifically not recommended other than strictly for debugging SSH communications since it provides so much data that it is difficult to identify important security information. INFO level is the basic level that only records login activity of SSH users. In many situations, such as Incident Response, it is important to determine when a particular user was active on a system. The logout record can eliminate those users who disconnected, which helps narrow the field.

Solution

Edit the /etc/ssh/sshd_config:

vi /etc/ssh/sshd_config

Set:

LogLevel INFO

or

LogLevel VERBOSE

Re-cycle the sshd daemon to pick up the configuration changes:

stopsrc -s sshd
sleep 5
startsrc -s sshd

Additional Information:

To resolve accountability for who is logging in as root using publickey authentication together with LogLevel INFO remember that AIX syslog must also be configured to provide .info level for the facility chosen (default is auth).

For example: auth.info /var/log/syslog/auth.log rotate size 1m files 4

Properly configured provides the following syslog information showing the fingerprint of the key used to access an account:

Jun 25 09:26:41 x071 auth|security:info sshd[8323282]: Accepted publickey for michael from 192.168.129.11 port 54278 ssh2: RSA SHA256:dRHxa5CGr5HCdC89suwYIBtAT8lyogz4SErSxTq0JXk

Jun 25 09:26:52 x071 auth|security:info sshd[8847396]: Accepted publickey for root from 192.168.129.11 port 54279 ssh2: RSA SHA256:dRHxa5CGr5HCdC89suwYIBtAT8lyogz4SErSxTq0JXk

Jun 25 09:26:53 x071 auth|security:info sshd[9044142]: Accepted publickey for root from 192.168.129.11 port 54280 ssh2: RSA SHA256:dRHxa5CGr5HCdC89suwYIBtAT8lyogz4SErSxTq0JXk

See Also

https://workbench.cisecurity.org/files/4119

Item Details

Category: AUDIT AND ACCOUNTABILITY

References: 800-53|AU-2, 800-53|AU-7, 800-53|AU-12, CSCv7|6.2

Plugin: Unix

Control ID: 42af47df946570fa0b448f958b7fd5b4366b860cef122ecac0c6318f86c38097