The shipped /etc/security/mkuser.sys file on AIX must not be customized directly.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-91211	AIX7-00-001015	SV-101311r1_rule		Medium

Description
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.

STIG	Date
IBM AIX 7.x Security Technical Implementation Guide	2020-02-24

Details

Check Text ( C-90367r1_chk )
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.

Check Text ( C-90367r1_chk )

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 (F-97411r1_fix)
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

Fix Text (F-97411r1_fix)

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