[Python-checkins] cpython (3.5): Issue #22636: avoid using a shell in the ctypes.util module
martin.panter
python-checkins at python.org
Mon Jun 13 23:03:40 EDT 2016
https://hg.python.org/cpython/rev/0715d403cae2
changeset: 101989:0715d403cae2
branch: 3.5
user: Martin Panter <vadmium+py at gmail.com>
date: Tue Jun 14 01:27:11 2016 +0000
summary:
Issue #22636: avoid using a shell in the ctypes.util module
Replace os.popen() with subprocess.Popen. Based on patch by Victor Stinner.
If the "gcc", "cc" or "objdump" command is not available, the code was
supposed to raise an OSError exception. But there was a bug in the code. The
shell code returns the exit code 10 if the required command is missing, and the
code tries to check for the status 10. The problem is that os.popen() doesn't
return the exit code directly, but a status which should be processed by
os.WIFEXITED() and os.WEXITSTATUS(). In practice, the exception was never
raised. The OSError exception was not documented and ctypes.util.find_library()
is expected to return None if the library is not found.
files:
Lib/ctypes/test/test_find.py | 7 +-
Lib/ctypes/util.py | 119 ++++++++++++++--------
Misc/NEWS | 3 +
3 files changed, 85 insertions(+), 44 deletions(-)
diff --git a/Lib/ctypes/test/test_find.py b/Lib/ctypes/test/test_find.py
--- a/Lib/ctypes/test/test_find.py
+++ b/Lib/ctypes/test/test_find.py
@@ -1,5 +1,5 @@
import unittest
-import os
+import os, os.path
import sys
import test.support
from ctypes import *
@@ -64,6 +64,11 @@
self.skipTest('lib_gle not available')
self.gle.gleGetJoinStyle
+ def test_shell_injection(self):
+ result = find_library('; echo Hello shell > ' + test.support.TESTFN)
+ self.assertFalse(os.path.lexists(test.support.TESTFN))
+ self.assertIsNone(result)
+
# On platforms where the default shared library suffix is '.so',
# at least some libraries can be loaded as attributes of the cdll
# object, since ctypes now tries loading the lib again
diff --git a/Lib/ctypes/util.py b/Lib/ctypes/util.py
--- a/Lib/ctypes/util.py
+++ b/Lib/ctypes/util.py
@@ -1,6 +1,7 @@
-import sys, os
-import contextlib
+import os
+import shutil
import subprocess
+import sys
# find_library(name) returns the pathname of a library, or None.
if os.name == "nt":
@@ -94,28 +95,43 @@
import re, tempfile
def _findLib_gcc(name):
- expr = r'[^\(\)\s]*lib%s\.[^\(\)\s]*' % re.escape(name)
- fdout, ccout = tempfile.mkstemp()
- os.close(fdout)
- cmd = 'if type gcc >/dev/null 2>&1; then CC=gcc; elif type cc >/dev/null 2>&1; then CC=cc;else exit 10; fi;' \
- 'LANG=C LC_ALL=C $CC -Wl,-t -o ' + ccout + ' 2>&1 -l' + name
+ # Run GCC's linker with the -t (aka --trace) option and examine the
+ # library name it prints out. The GCC command will fail because we
+ # haven't supplied a proper program with main(), but that does not
+ # matter.
+ expr = os.fsencode(r'[^\(\)\s]*lib%s\.[^\(\)\s]*' % re.escape(name))
+
+ c_compiler = shutil.which('gcc')
+ if not c_compiler:
+ c_compiler = shutil.which('cc')
+ if not c_compiler:
+ # No C compiler available, give up
+ return None
+
+ temp = tempfile.NamedTemporaryFile()
try:
- f = os.popen(cmd)
- try:
- trace = f.read()
- finally:
- rv = f.close()
+ args = [c_compiler, '-Wl,-t', '-o', temp.name, '-l' + name]
+
+ env = dict(os.environ)
+ env['LC_ALL'] = 'C'
+ env['LANG'] = 'C'
+ proc = subprocess.Popen(args,
+ stdout=subprocess.PIPE,
+ stderr=subprocess.STDOUT,
+ env=env)
+ with proc:
+ trace = proc.stdout.read()
finally:
try:
- os.unlink(ccout)
+ temp.close()
except FileNotFoundError:
+ # Raised if the file was already removed, which is the normal
+ # behaviour of GCC if linking fails
pass
- if rv == 10:
- raise OSError('gcc or cc command not found')
res = re.search(expr, trace)
if not res:
return None
- return res.group(0)
+ return os.fsdecode(res.group(0))
if sys.platform == "sunos5":
@@ -123,55 +139,65 @@
def _get_soname(f):
if not f:
return None
- cmd = "/usr/ccs/bin/dump -Lpv 2>/dev/null " + f
- with contextlib.closing(os.popen(cmd)) as f:
- data = f.read()
- res = re.search(r'\[.*\]\sSONAME\s+([^\s]+)', data)
+
+ proc = subprocess.Popen(("/usr/ccs/bin/dump", "-Lpv", f),
+ stdout=subprocess.PIPE,
+ stderr=subprocess.DEVNULL)
+ with proc:
+ data = proc.stdout.read()
+ res = re.search(br'\[.*\]\sSONAME\s+([^\s]+)', data)
if not res:
return None
- return res.group(1)
+ return os.fsdecode(res.group(1))
else:
def _get_soname(f):
# assuming GNU binutils / ELF
if not f:
return None
- cmd = 'if ! type objdump >/dev/null 2>&1; then exit 10; fi;' \
- "objdump -p -j .dynamic 2>/dev/null " + f
- f = os.popen(cmd)
- try:
- dump = f.read()
- finally:
- rv = f.close()
- if rv == 10:
- raise OSError('objdump command not found')
- res = re.search(r'\sSONAME\s+([^\s]+)', dump)
+ objdump = shutil.which('objdump')
+ if not objdump:
+ # objdump is not available, give up
+ return None
+
+ proc = subprocess.Popen((objdump, '-p', '-j', '.dynamic', f),
+ stdout=subprocess.PIPE,
+ stderr=subprocess.DEVNULL)
+ with proc:
+ dump = proc.stdout.read()
+ res = re.search(br'\sSONAME\s+([^\s]+)', dump)
if not res:
return None
- return res.group(1)
+ return os.fsdecode(res.group(1))
if sys.platform.startswith(("freebsd", "openbsd", "dragonfly")):
def _num_version(libname):
# "libxyz.so.MAJOR.MINOR" => [ MAJOR, MINOR ]
- parts = libname.split(".")
+ parts = libname.split(b".")
nums = []
try:
while parts:
nums.insert(0, int(parts.pop()))
except ValueError:
pass
- return nums or [ sys.maxsize ]
+ return nums or [sys.maxsize]
def find_library(name):
ename = re.escape(name)
expr = r':-l%s\.\S+ => \S*/(lib%s\.\S+)' % (ename, ename)
- with contextlib.closing(os.popen('/sbin/ldconfig -r 2>/dev/null')) as f:
- data = f.read()
+ expr = os.fsencode(expr)
+
+ proc = subprocess.Popen(('/sbin/ldconfig', '-r'),
+ stdout=subprocess.PIPE,
+ stderr=subprocess.DEVNULL)
+ with proc:
+ data = proc.stdout.read()
+
res = re.findall(expr, data)
if not res:
return _get_soname(_findLib_gcc(name))
res.sort(key=_num_version)
- return res[-1]
+ return os.fsdecode(res[-1])
elif sys.platform == "sunos5":
@@ -179,17 +205,24 @@
if not os.path.exists('/usr/bin/crle'):
return None
+ env = dict(os.environ)
+ env['LC_ALL'] = 'C'
+
if is64:
- cmd = 'env LC_ALL=C /usr/bin/crle -64 2>/dev/null'
+ args = ('/usr/bin/crle', '-64')
else:
- cmd = 'env LC_ALL=C /usr/bin/crle 2>/dev/null'
+ args = ('/usr/bin/crle',)
paths = None
- with contextlib.closing(os.popen(cmd)) as f:
- for line in f.readlines():
+ proc = subprocess.Popen(args,
+ stdout=subprocess.PIPE,
+ stderr=subprocess.DEVNULL,
+ env=env)
+ with proc:
+ for line in proc.stdout:
line = line.strip()
- if line.startswith('Default Library Path (ELF):'):
- paths = line.split()[4]
+ if line.startswith(b'Default Library Path (ELF):'):
+ paths = os.fsdecode(line).split()[4]
if not paths:
return None
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -13,6 +13,9 @@
Library
-------
+- Issue #22636: Avoid shell injection problems with
+ ctypes.util.find_library().
+
- Issue #16182: Fix various functions in the "readline" module to use the
locale encoding, and fix get_begidx() and get_endidx() to return code point
indexes.
--
Repository URL: https://hg.python.org/cpython
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