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V-215288

CAT II (Medium)

All AIX shells referenced in passwd file must be listed in /etc/shells file, except any shells specified for the purpose of preventing logins.

Rule ID

SV-215288r991589_rule

STIG

IBM AIX 7.x Security Technical Implementation Guide

Version

V3R2

CCIs

CCI-000366

Discussion

The /etc/shells file lists approved default shells. It helps provide layered defense to the security approach by ensuring users cannot change their default shell to an unauthorized unsecure shell.

Check Content

Confirm the login shells referenced in the "/etc/passwd" file are listed in the "/etc/security/login.cfg" file's "shells =variable" in the usw stanza by running commands: 

#  more /etc/security/login.cfg | grep shells | grep -v '*'
        shells = /bin/sh,/bin/bsh,/bin/csh,/bin/ksh,/bin/tsh,/bin/ksh93,/usr/bin/sh,/usr/bin/bsh,/usr/bin/csh,/usr/bin/ksh,/usr/bin/tsh 

# more /etc/shells 
/bin/csh
/bin/ksh
/bin/psh
/bin/tsh
/bin/bsh
/usr/bin/csh
/usr/bin/ksh
/usr/bin/psh
/usr/bin/tsh
/usr/bin/bsh

The "/usr/bin/false", "/bin/false", "/dev/null", "/sbin/nologin" (and equivalents), and "sdshell" will be considered valid shells for use in the "/etc/passwd" file, but will not be listed in the shells stanza. 
If a shell referenced in "/etc/passwd" is not listed in the shells stanza, excluding the above mentioned shells, this is a finding.

Fix Text

Use the "chsh" utility or edit the "/etc/passwd" file and correct the error by changing the default shell of the account in error to an acceptable shell name contained in the "/etc/shells file". 

Alternatively, use the SMIT to change the "/etc/passwd" shell entry.