execstack(8) System Manager's Manual execstack(8)NAME
execstack - tool to set, clear, or query executable stack flag of ELF binaries and shared libraries
execstack [OPTION...] [FILES]
execstack is a program which sets, clears, or queries executable stack flag of ELF binaries and shared libraries. Linux has in the past
allowed execution of instructions on the stack and there are lots of binaries and shared libraries assuming this behaviour. Furthermore,
GCC trampoline code for e.g. nested functions requires executable stack on many architectures. To avoid breaking binaries and shared
libraries which need executable stack, ELF binaries and shared libraries now can be marked as requiring executable stack or not requiring
it. This marking is done through the p_flags field in the PT_GNU_STACK program header entry. If the marking is missing, kernel or dynamic
linker need to assume it might need executable stack. The marking is done automatically by recent GCC versions (objects using trampolines
on the stack are marked as requiring executable stack, all other newly built objects are marked as not requiring it) and linker collects
these markings into marking of the whole binary or shared library. The user can override this at assembly time (through --execstack or
--noexecstack assembler options), at link time (through -z execstack or -z noexecstack linker options) and using the execstack tool also on
an already linker binary or shared library. This tool is especially useful for third party shared libraries where it is known that they
don't need executable stack or testing proves it.
OPTIONS -s --set-execstack
Mark binary or shared library as requiring executable stack.
Mark binary or shared library as not requiring executable stack.
Query executable stack marking of binaries and shared libraries. For each file it prints either - when executable stack is not
required, X when executable stack is required or ? when it is unknown whether the object requires or doesn't require executable
stack (the marking is missing).
-V Print execstack version and exit.
Print help message.
Print a short usage message.
Command line arguments should be names of ELF binaries and shared libraries which should be modified or queried.
# execstack -s ~/lib/libfoo.so.1
will mark ~/lib/libfoo.so.1 as requiring executable stack.
# execstack -c ~/bin/bar
will mark ~/bin/bar as not requiring executable stack.
# execstack -q ~/lib/libfoo.so.1 ~/bin/bar
will query executable stack marking of the given files.
SEE ALSO ld.so(8).
execstack doesn't support yet marking of executables if they do not have PT_GNU_STACK program header entry nor they have room for program
segment header table growth.
Jakub Jelinek <email@example.com>.
28 October 2003 execstack(8)
Check Out this Related Man Page
HARDENING-CHECK(1) User Contributed Perl Documentation HARDENING-CHECK(1)NAME
hardening-check - check binaries for security hardening features
hardening-check [options] [ELF ...]
Examine a given set of ELF binaries and check for several security hardening features, failing if they are not all found.
This utility checks a given list of ELF binaries for several security hardening features that can be compiled into an executable. These
Position Independent Executable
This indicates that the executable was built in such a way (PIE) that the "text" section of the program can be relocated in memory.
To take full advantage of this feature, the executing kernel must support text Address Space Layout Randomization (ASLR).
This indicates that there is evidence that the ELF was compiled with the gcc(1) option -fstack-protector (e.g. uses
__stack_chk_fail). The program will be resistant to having its stack overflowed.
When an executable was built without any character arrays being allocated on the stack, this check will lead to false alarms (since
there is no use of __stack_chk_fail), even though it was compiled with the correct options.
Fortify Source functions
This indicates that the executable was compiled with -D_FORTIFY_SOURCE=2 and -O1 or higher. This causes certain unsafe glibc
functions with their safer counterparts (e.g. strncpy instead of strcpy), or replaces calls that are verifiable at runtime with the
runtime-check version (e.g. __memcpy_chk insteade of memcpy).
When an executable was built such that the fortified versions of the glibc functions are not useful (e.g. use is verified as safe
at compile time, or use cannot be verified at runtime), this check will lead to false alarms. In an effort to mitigate this, the
check will pass if any fortified function is found, and will fail if only unfortified functions are found. Uncheckable conditions
also pass (e.g. no functions that could be fortified are found, or not linked against glibc).
This indicates that the executable was build with -Wl,-z,relro to have ELF markings (RELRO) that ask the runtime linker to mark any
regions of the relocation table as "read-only" if they were resolved before execution begins. This reduces the possible areas of
memory in a program that can be used by an attacker that performs a successful memory corruption exploit.
This indicates that the executable was built with -Wl,-z,now to have ELF markings (BIND_NOW) that ask the runtime linker to resolve
all relocations before starting program execution. When combined with RELRO above, this further reduces the regions of memory
available to memory corruption attacks.
OPTIONS --nopie, -p
No not require that the checked binaries be built as PIE.
No not require that the checked binaries be built with the stack protector.
No not require that the checked binaries be built with Fority Source.
No not require that the checked binaries be built with RELRO.
No not require that the checked binaries be built with BIND_NOW.
Only report failures.
Report verbosely on failures.
After the report, display all external functions needed by the ELF.
Instead of the regular report, locate the libc for the first ELF on the command line and report all the known "fortified" functions
exported by libc.
--color Enable colorized status output.
Switch reporting to lintian-check-parsable output.
--debug Report some debugging during processing.
--help, -h, -?
Print a brief help message and exit.
--man Print the manual page and exit.
When all checked binaries have all checkable hardening features detected, this program will finish with an exit code of 0. If any check
fails, the exit code with be 1. Individual checks can be disabled via command line options.
Kees Cook <firstname.lastname@example.org>
COPYRIGHT AND LICENSE
Copyright 2009-2012 Kees Cook <email@example.com>.
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 or later.
SEE ALSO gcc(1), hardening-wrapper(1)perl v5.14.2 2012-06-14 HARDENING-CHECK(1)