saymrwulf/cryptography
1
0
Fork 0
mirror of https://github.com/saymrwulf/cryptography.git synced 2026-05-14 20:37:55 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

C locking callback (#3226)

Browse source 
* Remove Python OpenSSL locking callback and replace it with one in C

The Python OpenSSL locking callback is unsafe; if GC is triggered
during the callback's invocation, it can result in the callback being
invoked reentrantly, which can lead to deadlocks. This patch replaces
it with one in C that gets built at compile time via cffi along with
the rest of the OpenSSL binding.

* fixes for some issues

* unused

* revert these changes

* these two for good measure

* missing param

* sigh, syntax

* delete tests that assumed an ability to mess with locks

* style fixes

* licensing stuff

* utf8

* Unicode. Huh. What it isn't good for, absolutely nothing.
This commit is contained in:
Alex Gaynor 2016-11-13 15:55:22 -05:00 committed by Paul Kehrer
parent 562b9a9055
commit d862933de5
5 changed files with 118 additions and 95 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
LICENSE
View file

@ -1,3 +1,6 @@
This software is made available under the terms of *either* of the licenses
found in LICENSE.APACHE or LICENSE.BSD. Contributions to cryptography are made
under the terms of *both* these licenses.
The code used in the OpenSSL locking callback is derived from the same in
Python itself, and is licensed under the terms of the PSF License Agreement.

41
LICENSE.PSF Normal file
View file

@ -0,0 +1,41 @@
1. This LICENSE AGREEMENT is between the Python Software Foundation ("PSF"), and
the Individual or Organization ("Licensee") accessing and otherwise using Python
2.7.12 software in source or binary form and its associated documentation.
2. Subject to the terms and conditions of this License Agreement, PSF hereby
grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
analyze, test, perform and/or display publicly, prepare derivative works,
distribute, and otherwise use Python 2.7.12 alone or in any derivative
version, provided, however, that PSF's License Agreement and PSF's notice of
copyright, i.e., "Copyright © 2001-2016 Python Software Foundation; All Rights
Reserved" are retained in Python 2.7.12 alone or in any derivative version
prepared by Licensee.
3. In the event Licensee prepares a derivative work that is based on or
incorporates Python 2.7.12 or any part thereof, and wants to make the
derivative work available to others as provided herein, then Licensee hereby
agrees to include in any such work a brief summary of the changes made to Python
2.7.12.
4. PSF is making Python 2.7.12 available to Licensee on an "AS IS" basis.
PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED. BY WAY OF
EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND DISCLAIMS ANY REPRESENTATION OR
WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR THAT THE
USE OF PYTHON 2.7.12 WILL NOT INFRINGE ANY THIRD PARTY RIGHTS.
5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON 2.7.12
FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS A RESULT OF
MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 2.7.12, OR ANY DERIVATIVE
THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
6. This License Agreement will automatically terminate upon a material breach of
its terms and conditions.
7. Nothing in this License Agreement shall be deemed to create any relationship
of agency, partnership, or joint venture between PSF and Licensee. This License
Agreement does not grant permission to use PSF trademarks or trade name in a
trademark sense to endorse or promote products or services of Licensee, or any
third party.
8. By copying, installing or otherwise using Python 2.7.12, Licensee agrees
to be bound by the terms and conditions of this License Agreement.

73
src/_cffi_src/openssl/callbacks.py
View file

@ -12,6 +12,9 @@ INCLUDES = """
#include <openssl/ssl.h>
#include <openssl/x509.h>
#include <openssl/x509_vfy.h>
#include <openssl/crypto.h>
#include <pythread.h>
"""
TYPES = """
@ -37,6 +40,7 @@ extern "Python" int Cryptography_rand_status(void);
"""
FUNCTIONS = """
int _setup_ssl_threads(void);
"""
MACROS = """
@ -50,4 +54,71 @@ if cffi.__version_info__ < (1, 4, 0) or sys.version_info >= (3, 5):
# backwards compatibility for old cffi version on PyPy
# and Python >=3.5 (https://github.com/pyca/cryptography/issues/2970)
TYPES = "static const long Cryptography_STATIC_CALLBACKS;"
CUSTOMIZATIONS = "static const long Cryptography_STATIC_CALLBACKS = 0;"
CUSTOMIZATIONS = """static const long Cryptography_STATIC_CALLBACKS = 0;
"""
CUSTOMIZATIONS += """
/* This code is derived from the locking code found in the Python _ssl module's
locking callback for OpenSSL.
Copyright 2001-2016 Python Software Foundation; All Rights Reserved.
*/
static unsigned int _ssl_locks_count = 0;
static PyThread_type_lock *_ssl_locks = NULL;
static void _ssl_thread_locking_function(int mode, int n, const char *file,
int line) {
/* this function is needed to perform locking on shared data
structures. (Note that OpenSSL uses a number of global data
structures that will be implicitly shared whenever multiple
threads use OpenSSL.) Multi-threaded applications will
crash at random if it is not set.
locking_function() must be able to handle up to
CRYPTO_num_locks() different mutex locks. It sets the n-th
lock if mode & CRYPTO_LOCK, and releases it otherwise.
file and line are the file number of the function setting the
lock. They can be useful for debugging.
*/
if ((_ssl_locks == NULL) ||
(n < 0) || ((unsigned)n >= _ssl_locks_count)) {
return;
}
if (mode & CRYPTO_LOCK) {
PyThread_acquire_lock(_ssl_locks[n], 1);
} else {
PyThread_release_lock(_ssl_locks[n]);
}
}
int _setup_ssl_threads(void) {
unsigned int i;
if (_ssl_locks == NULL) {
_ssl_locks_count = CRYPTO_num_locks();
_ssl_locks = PyMem_New(PyThread_type_lock, _ssl_locks_count);
if (_ssl_locks == NULL) {
PyErr_NoMemory();
return 0;
}
memset(_ssl_locks, 0, sizeof(PyThread_type_lock) * _ssl_locks_count);
for (i = 0; i < _ssl_locks_count; i++) {
_ssl_locks[i] = PyThread_allocate_lock();
if (_ssl_locks[i] == NULL) {
unsigned int j;
for (j = 0; j < i; j++) {
PyThread_free_lock(_ssl_locks[j]);
}
PyMem_Free(_ssl_locks);
return 0;
}
}
CRYPTO_set_locking_callback(_ssl_thread_locking_function);
}
return 1;
}
"""

31
src/cryptography/hazmat/bindings/openssl/binding.py
View file

@ -118,8 +118,6 @@ class Binding(object):
lib = None
ffi = ffi
_lib_loaded = False
_locks = None
_lock_cb_handle = None
_init_lock = threading.Lock()
_lock_init_lock = threading.Lock()
@ -178,14 +176,6 @@ class Binding(object):
def init_static_locks(cls):
with cls._lock_init_lock:
cls._ensure_ffi_initialized()
if not cls._lock_cb_handle:
wrapper = ffi_callback(
"void(int, int, const char *, int)",
name="Cryptography_locking_cb",
)
cls._lock_cb_handle = wrapper(cls._lock_cb)
# Use Python's implementation if available, importing _ssl triggers
# the setup for this.
__import__("_ssl")
@ -195,25 +185,8 @@ class Binding(object):
# If nothing else has setup a locking callback already, we set up
# our own
num_locks = cls.lib.CRYPTO_num_locks()
cls._locks = [threading.Lock() for n in range(num_locks)]
cls.lib.CRYPTO_set_locking_callback(cls._lock_cb_handle)
@classmethod
def _lock_cb(cls, mode, n, file, line):
lock = cls._locks[n]
if mode & cls.lib.CRYPTO_LOCK:
lock.acquire()
elif mode & cls.lib.CRYPTO_UNLOCK:
lock.release()
else:
raise RuntimeError(
"Unknown lock mode {0}: lock={1}, file={2}, line={3}.".format(
mode, n, file, line
)
)
res = lib._setup_ssl_threads()
_openssl_assert(cls.lib, res == 1)
def _verify_openssl_version(version):

65
tests/hazmat/bindings/test_openssl.py
View file

@ -31,71 +31,6 @@ class TestOpenSSL(object):
lock_cb = b.lib.CRYPTO_get_locking_callback()
assert lock_cb != b.ffi.NULL
def _skip_if_not_fallback_lock(self, b):
# only run this test if we are using our locking cb
original_cb = b.lib.CRYPTO_get_locking_callback()
if original_cb != b._lock_cb_handle:
pytest.skip(
"Not using the fallback Python locking callback "
"implementation. Probably because import _ssl set one"
)
def test_fallback_crypto_lock_via_openssl_api(self):
b = Binding()
b.init_static_locks()
self._skip_if_not_fallback_lock(b)
# check that the lock state changes appropriately
lock = b._locks[b.lib.CRYPTO_LOCK_SSL]
# starts out unlocked
assert lock.acquire(False)
lock.release()
b.lib.CRYPTO_lock(
b.lib.CRYPTO_LOCK | b.lib.CRYPTO_READ,
b.lib.CRYPTO_LOCK_SSL, b.ffi.NULL, 0
)
# becomes locked
assert not lock.acquire(False)
b.lib.CRYPTO_lock(
b.lib.CRYPTO_UNLOCK | b.lib.CRYPTO_READ,
b.lib.CRYPTO_LOCK_SSL, b.ffi.NULL, 0
)
# then unlocked
assert lock.acquire(False)
lock.release()
def test_fallback_crypto_lock_via_binding_api(self):
b = Binding()
b.init_static_locks()
self._skip_if_not_fallback_lock(b)
lock = b._locks[b.lib.CRYPTO_LOCK_SSL]
with pytest.raises(RuntimeError):
b._lock_cb(0, b.lib.CRYPTO_LOCK_SSL, "<test>", 1)
# errors shouldn't cause locking
assert lock.acquire(False)
lock.release()
b._lock_cb(b.lib.CRYPTO_LOCK | b.lib.CRYPTO_READ,
b.lib.CRYPTO_LOCK_SSL, "<test>", 1)
# locked
assert not lock.acquire(False)
b._lock_cb(b.lib.CRYPTO_UNLOCK | b.lib.CRYPTO_READ,
b.lib.CRYPTO_LOCK_SSL, "<test>", 1)
# unlocked
assert lock.acquire(False)
lock.release()
def test_add_engine_more_than_once(self):
b = Binding()
b._register_osrandom_engine()