Title

The shipped /etc/security/mkuser.sys file on AIX must not be customized directly. (Cat II impact)

Discussion

The "/etc/security/mkuser.sys" script customizes the new user account when a new user is created, or a user is logging into the system without a home directory. An improper "/etc/security/mkuser.sys" script increases the risk that non-privileged users may obtain elevated privileges.

Check Content

Use the "cat" command to show the content of "/etc/security/mkuser.sys" script: # cat /etc/security/mkuser.sys The cat command should display the following: # This file is no longer user customizable. To have a customized mkuser.sys script # create a file /etc/security/mkuser.sys.custom and the /etc/security/mkuser.sys # will run this script instead of the original mkuser.sys script. export PATH=/usr/bin:/usr/sbin:$PATH # # Check the number of arguments first # if [ $# -ne 4 ] then exit 1 fi # # If a customer mkuser.sys.custom script exists # then execute it instead and exit passing all arguments # and returning the return code from mkuser.sys.custom # if [ -x /etc/security/mkuser.sys.custom ] then /etc/security/mkuser.sys.custom $* exit $? fi # # Create the named directory if it does not already exist # and set the file ownership and permission # if [ ! -d $1 ] then last=$1 while [ 1 ] do dir=`dirname $last` if [ -d $last ] then break elif [ -d $dir ] then mkdir -p $1 chown -R bin:bin $last chmod -R 755 $last break else last=$dir fi done chgrp "$3" $1 chown $2 $1 fi # # Copy the user's default .profile if it does not already # exist and change the file ownership, etc. # if [ `basename $4` != "csh" ] && [ ! -f $1/.profile ] then cp /etc/security/.profile $1/.profile chmod u+rwx,go-w $1/.profile chgrp "$3" $1/.profile chown $2 $1/.profile else if [ `basename $4` = "csh" ] && [ ! -f $1/.login ] then echo "#!/bin/csh" > "$1"/.login echo "set path = ( /usr/bin /etc /usr/sbin /usr/ucb \$HOME/bin /usr/bin/X11 /sbin . )" >> "$1"/.login echo "setenv MAIL \"/var/spool/mail/\$LOGNAME\"" >> "$1"/.login echo "setenv MAILMSG \"[YOU HAVE NEW MAIL]\"" >> "$1"/.login echo "if ( -f \"\$MAIL\" && ! -z \"\$MAIL\") then" >> "$1"/.login echo " echo \"\$MAILMSG\"" >> "$1"/.login echo "endif" >> "$1"/.login chmod u+rwx,go-w $1/.login chgrp "$3" $1/.login chown $2 $1/.login fi fi If the "cat" command shows the script as different than the content listed above, this is a finding.

Fix Text

Edit the script /etc/security/mkuser.sys to contain the following: # This file is no longer user customizable. To have a customized mkuser.sys script # create a file /etc/security/mkuser.sys.custom and the /etc/security/mkuser.sys # will run this script instead of the original mkuser.sys script. export PATH=/usr/bin:/usr/sbin:$PATH # # Check the number of arguments first # if [ $# -ne 4 ] then exit 1 fi # # If a customer mkuser.sys.custom script exists # then execute it instead and exit passing all arguments # and returning the return code from mkuser.sys.custom # if [ -x /etc/security/mkuser.sys.custom ] then /etc/security/mkuser.sys.custom $* exit $? fi # # Create the named directory if it does not already exist # and set the file ownership and permission # if [ ! -d $1 ] then last=$1 while [ 1 ] do dir=`dirname $last` if [ -d $last ] then break elif [ -d $dir ] then mkdir -p $1 chown -R bin:bin $last chmod -R 755 $last break else last=$dir fi done chgrp "$3" $1 chown $2 $1 fi # # Copy the user's default .profile if it does not already # exist and change the file ownership, etc. # if [ `basename $4` != "csh" ] && [ ! -f $1/.profile ] then cp /etc/security/.profile $1/.profile chmod u+rwx,go-w $1/.profile chgrp "$3" $1/.profile chown $2 $1/.profile else if [ `basename $4` = "csh" ] && [ ! -f $1/.login ] then echo "#!/bin/csh" > "$1"/.login echo "set path = ( /usr/bin /etc /usr/sbin /usr/ucb \$HOME/bin /usr/bin/X11 /sbin . )" >> "$1"/.login echo "setenv MAIL \"/var/spool/mail/\$LOGNAME\"" >> "$1"/.login echo "setenv MAILMSG \"[YOU HAVE NEW MAIL]\"" >> "$1"/.login echo "if ( -f \"\$MAIL\" && ! -z \"\$MAIL\") then" >> "$1"/.login echo " echo \"\$MAILMSG\"" >> "$1"/.login echo "endif" >> "$1"/.login chmod u+rwx,go-w $1/.login chgrp "$3" $1/.login chown $2 $1/.login fi fi

Additional Identifiers

Rule ID: SV-215181r958362_rule

Vulnerability ID: V-215181

Group Title: SRG-OS-000001-GPOS-00001

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