Checksec is a bash shell script that is used to check the properties of executables (like PIE, RELRO, Canaries, ASLR, Fortify Source) and the linux kernel. It has been originally written by Tobias Klein in 2011 and the original source is available here: http://www.trapkit.de/tools/checksec.html

Manually verify checksec

openssl dgst -sha256 -verify checksec.pub -signature checksec.sig checksec

Examples

normal (or –format=cli)

$ checksec --file=/bin/ls
RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH      FILE
Partial RELRO   Canary found      NX enabled    No PIE          No RPATH   No RUNPATH   /bin/ls

csv

$ checksec --output=csv --file=/bin/ls
Partial RELRO,Canary found,NX enabled,No PIE,No RPATH,No RUNPATH,/bin/ls

xml

$ checksec --output=xml --file=/bin/ls
<?xml version="1.0" encoding="UTF-8"?>
<file relro="partial" canary="yes" nx="yes" pie="no" rpath="no" runpath="no" filename='/bin/ls'/>

json

$ checksec --output=json --file=/bin/ls
{ "file": { "relro":"partial","canary":"yes","nx":"yes","pie":"no","rpath":"no","runpath":"no","filename":"/bin/ls" } }

Fortify test in cli

$ checksec --fortify-proc=1
* Process name (PID)                         : init (1)
* FORTIFY_SOURCE support available (libc)    : Yes
* Binary compiled with FORTIFY_SOURCE support: Yes

------ EXECUTABLE-FILE ------- . -------- LIBC --------
FORTIFY-able library functions | Checked function names
-------------------------------------------------------
fdelt_chk                      | __fdelt_chk
read                           | __read_chk
syslog_chk                     | __syslog_chk
fprintf_chk                    | __fprintf_chk
vsnprintf_chk                  | __vsnprintf_chk
fgets                          | __fgets_chk
strncpy                        | __strncpy_chk
snprintf_chk                   | __snprintf_chk
memset                         | __memset_chk
strncat_chk                    | __strncat_chk
memcpy                         | __memcpy_chk
fread                          | __fread_chk
sprintf_chk                    | __sprintf_chk

SUMMARY:

* Number of checked functions in libc                : 78
* Total number of library functions in the executable: 116
* Number of FORTIFY-able functions in the executable : 13
* Number of checked functions in the executable      : 7
* Number of unchecked functions in the executable    : 6

Note on Fortify results. There is not currently a known way to determine if the binary was compiled with FORTIFY_SOURCE level 1, 2, or 3 in a reliable manner.

Some binaries include some details about how it was compiled. For example, VIM on ubuntu is compiled with -D_FORTIFY_SOURCE=1. This can be identified with strings on the binary. Most binaries do not include this data, but some do.

$ strings vim | grep FORTIFY
gcc -c -I. -Iproto -DHAVE_CONFIG_H -Wdate-time -g -O2 -ffile-prefix-map=/build/vim-CSyBG7/vim-8.2.3995=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -D_REENTRANT -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1

Kernel test in Cli

$ checksec --kernel
* Kernel protection information:

Description - List the status of kernel protection mechanisms. Rather than
inspect kernel mechanisms that may aid in the prevention of exploitation of
userspace processes, this option lists the status of kernel configuration
options that harden the kernel itself against attack.

Kernel config: /proc/config.gz

    GCC stack protector support:            Enabled
    Strict user copy checks:                Disabled
    Enforce read-only kernel data:          Disabled
    Restrict /dev/mem access:               Enabled
    Restrict /dev/kmem access:              Enabled

* Kernel Heap Hardening: No KERNHEAP

The KERNHEAP hardening patchset is available here:
    https://www.subreption.com/kernheap/

Kernel Test in XML

$ checksec --output=xml --kernel
<?xml version="1.0" encoding="UTF-8"?>
<kernel config='/boot/config-3.11-2-amd64' gcc_stack_protector='yes' strict_user_copy_check='no' ro_kernel_data='yes' restrict_dev_mem_access='yes' restrict_dev_kmem_access='no'>
<kernheap config='no' />
</kernel>

Kernel Test in Json

$ checksec --output=json --kernel
{ "kernel": { "KernelConfig":"/boot/config-3.11-2-amd64","gcc_stack_protector":"yes","strict_user_copy_check":"no","ro_kernel_data":"yes","restrict_dev_mem_access":"yes","restrict_dev_kmem_access":"no" },{ "kernheap_config":"no" } }

Using with Cross-compiled Systems

The checksec tool can be used against cross-compiled target file-systems offline. Key limitations to note:

• Kernel tests - require you to execute the script on the running system you’d like to check as they directly access kernel resources to identify system configuration/state. You can specify the config file for the kernel after the -k option.

• File check - the offline testing works for all the checks but the Fortify feature. Fortify, uses the running system’s libraries vs those in the offline file-system. There are ways to workaround this (chroot) but at the moment, the ideal configuration would have this script executing on the running system when checking the files.

The checksec tool’s normal use case is for runtime checking of the systems configuration. If the system is an embedded target, the native binutils tools like readelf may not be present. This would restrict which parts of the script will work.

Even with those limitations, information this script provides still makes it a valuable tool for checking offline file-systems.

OSX and BSD based systems Support

Most of the tools do not work on mach-O binaries, the OSX kernel or BSD kernels. It may work on certain BSD based systems but is not officially supported.