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System Administration Guide: Security Services
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Protecting Against Programs With Security Risk (Task Map)

The following task map points to procedures that find risky executables on the system, and that prevent programs from exploiting an executable stack.

Task

Description

For Instructions

Find files with special permissions

Locates files with the setuid bit set, but that are not owned by the root user.

How to Find Files With Special File Permissions

Prevent executable stack from overflowing

Prevents programs from exploiting an executable stack.

How to Disable Programs From Using Executable Stacks

Prevent logging of executable stack messages

Turns off logging of executable stack messages.

Example 7-13

How to Find Files With Special File Permissions

You should monitor your system for any unauthorized use of the setuid and setgid permissions on programs. The setuid and setgid permissions enable ordinary users to gain superuser capabilities. A suspicious executable file grants ownership to a user rather than to root or bin.

  1. Assume the Primary Administrator role, or become superuser.

    The Primary Administrator role includes the Primary Administrator profile. To create the role and assign the role to a user, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.

  2. Find files with setuid permissions by using the find command.
    # find directory -user root -perm -4000 -exec ls -ldb {} \; >/tmp/filename
    find directory

    Checks all mounted paths starting at the specified directory, which can be root (/), sys, bin, or mail.

    -user root

    Displays files owned only by root.

    -perm -4000

    Displays files only with permissions set to 4000.

    -exec ls -ldb

    Displays the output of the find command in ls -ldb format.

    >/tmp/filename

    Is the file that contains the results of the find command.

  3. Display the results in /tmp/filename.
    # more /tmp/filename

    For background information on setuid permissions, see setuid Permission.

Example 7-12 Finding Files With setuid Permissions

The output from the following example shows that a user named rar has made a personal copy of /usr/bin/sh, and has set the permissions as setuid to root. As a result, the /usr/rar/bin/sh program runs with root permissions.

This output was saved for future reference by moving the file out of the /tmp directory.

# find / -user root -perm -4000 -exec ls -ldb {} \; > /var/tmp/ckprm
# cat /var/tmp/ckprm
-r-sr-xr-x 1 root bin 38836 Aug 10 16:16 /usr/bin/at
-r-sr-xr-x 1 root bin 19812 Aug 10 16:16 /usr/bin/crontab
---s--x--x 1 root sys 46040 Aug 10 15:18 /usr/bin/ct
-r-sr-xr-x 1 root sys 12092 Aug 11 01:29 /usr/lib/mv_dir
-r-sr-sr-x 1 root bin 33208 Aug 10 15:55 /usr/lib/lpadmin
-r-sr-sr-x 1 root bin 38696 Aug 10 15:55 /usr/lib/lpsched
---s--x--- 1 root rar 45376 Aug 18 15:11 /usr/rar/bin/sh
-r-sr-xr-x 1 root bin 12524 Aug 11 01:27 /usr/bin/df
-rwsr-xr-x 1 root sys 21780 Aug 11 01:27 /usr/bin/newgrp
-r-sr-sr-x 1 root sys 23000 Aug 11 01:27 /usr/bin/passwd
-r-sr-xr-x 1 root sys 23824 Aug 11 01:27 /usr/bin/su
# mv /var/tmp/ckprm /export/sysreports/ckprm

How to Disable Programs From Using Executable Stacks

For a description of the security risks of executable stacks, see Preventing Executable Files From Compromising Security.

  1. Assume the Primary Administrator role, or become superuser.

    The Primary Administrator role includes the Primary Administrator profile. To create the role and assign the role to a user, see Chapter 2, Working With the Solaris Management Console (Tasks), in System Administration Guide: Basic Administration.

  2. Edit the /etc/system file, and add the following line:
    set noexec_user_stack=1
  3. Reboot the system.
    # init 6
Example 7-13 Disabling the Logging of Executable Stack Messages

In this example, the logging of executable stack messages is disabled, and then the system is rebooted.

# cat /etc/system
set noexec_user_stack=1
set noexec_user_stack_log=0
# init 6
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