Title

The SSH client must not permit GSSAPI authentication unless needed. (Cat III impact)

Discussion

GSSAPI authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system’s GSSAPI to remote hosts, increasing the attack surface of the system. GSSAPI authentication must be disabled unless needed.

Check Content

Check the SSH client configuration. Note that keywords are case-insensitive and arguments (args) are case-sensitive. keyword=GSSAPIAuthentication arg(s)=no Default values include: "no" Note: When the default "arg" value exactly matches the required "arg" value (see above), the <keyword=arg> entry is not required to exist (commented or uncommented) in the ssh (client) or sshd (server) configuration file. While not required, it is recommended that the configuration file(s) be populated with all keywords and assigned arg values as a means to explicitly document the ssh(d) binary's expected behavior. Examine the file. # cat /opt/ssh/etc/ssh_config | tr '\011' ' ' | tr -s ' ' | sed -e 's/^[ \t]*//' | grep -v '^#' | grep -i "GSSAPIAuthentication" If the return value is yes, this is a finding.

Fix Text

Edit the configuration file and set/add (if necessary) the GSSAPIAuthentication directive set to no.

Additional Identifiers

Rule ID: SV-35068r1_rule

Vulnerability ID: V-22474

Group Title: GEN005525

Expert Comments

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