Placeholder bug for CVE-2014-7817.
* CVE-2104-7817 The wordexp function could ignore the WRDE_NOCMD flag
under certain input conditions resulting in the execution of a shell for
command substitution when the applicaiton did not request it. The
implementation now checks WRDE_NOCMD immediately before executing the
shell and returns the error WRDE_CMDSUB as expected.
Fixed on trunk.
Author: Carlos O'Donell <email@example.com>
Date: Wed Nov 19 11:44:12 2014 -0500
CVE-2014-7817: wordexp fails to honour WRDE_NOCMD.
The function wordexp() fails to properly handle the WRDE_NOCMD
flag when processing arithmetic inputs in the form of "$((... ``))"
where "..." can be anything valid. The backticks in the arithmetic
epxression are evaluated by in a shell even if WRDE_NOCMD forbade
command substitution. This allows an attacker to attempt to pass
dangerous commands via constructs of the above form, and bypass
the WRDE_NOCMD flag. This patch fixes this by checking for WRDE_NOCMD
in exec_comm(), the only place that can execute a shell. All other
checks for WRDE_NOCMD are superfluous and removed.
We expand the testsuite and add 3 new regression tests of roughly
the same form but with a couple of nested levels.
On top of the 3 new tests we add fork validation to the WRDE_NOCMD
testing. If any forks are detected during the execution of a wordexp()
call with WRDE_NOCMD, the test is marked as failed. This is slightly
heuristic since vfork might be used in the future, but it provides a
higher level of assurance that no shells were executed as part of
command substitution with WRDE_NOCMD in effect. In addition it doesn't
require libpthread or libdl, instead we use the public implementation
namespace function __register_atfork (already part of the public ABI
Tested on x86_64 with no regressions.