- Issue #13703: oCERT-2011-003: add -R command-line option and PYTHONHASHSEED

environment variable, to provide an opt-in way to protect against denial of
  service attacks due to hash collisions within the dict and set types.  Patch
  by David Malcolm, based on work by Victor Stinner.
This commit is contained in:
Barry Warsaw 2012-02-20 20:42:21 -05:00
parent f5a5beb339
commit 1e13eb084f
27 changed files with 706 additions and 152 deletions

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@ -289,6 +289,11 @@ always available.
+------------------------------+------------------------------------------+
| :const:`bytes_warning` | -b |
+------------------------------+------------------------------------------+
+------------------------------+------------------------------------------+
| :const:`hash_randomization` | -R |
| | |
| | .. versionadded:: 2.6.8 |
+------------------------------+------------------------------------------+
.. versionadded:: 2.6

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@ -1273,6 +1273,8 @@ Basic customization
modules are still available at the time when the :meth:`__del__` method is
called.
See also the :option:`-R` command-line option.
.. method:: object.__repr__(self)

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@ -21,7 +21,7 @@ Command line
When invoking Python, you may specify any of these options::
python [-BdEiOQsStuUvVWxX3?] [-c command | -m module-name | script | - ] [args]
python [-BdEiOQsRStuUvVWxX3?] [-c command | -m module-name | script | - ] [args]
The most common use case is, of course, a simple invocation of a script::
@ -239,6 +239,29 @@ Miscellaneous options
:pep:`238` -- Changing the division operator
.. cmdoption:: -R
Turn on hash randomization, so that the :meth:`__hash__` values of str,
bytes and datetime objects are "salted" with an unpredictable random value.
Although they remain constant within an individual Python process, they are
not predictable between repeated invocations of Python.
This is intended to provide protection against a denial-of-service caused by
carefully-chosen inputs that exploit the worst case performance of a dict
insertion, O(n^2) complexity. See
http://www.ocert.org/advisories/ocert-2011-003.html for details.
Changing hash values affects the order in which keys are retrieved from a
dict. Although Python has never made guarantees about this ordering (and it
typically varies between 32-bit and 64-bit builds), enough real-world code
implicitly relies on this non-guaranteed behavior that the randomization is
disabled by default.
See also :envvar:`PYTHONHASHSEED`.
.. versionadded:: 2.6.8
.. cmdoption:: -s
Don't add user site directory to sys.path
@ -501,6 +524,27 @@ These environment variables influence Python's behavior.
.. versionadded:: 2.6
.. envvar:: PYTHONHASHSEED
If this variable is set to ``random``, the effect is the same as specifying
the :option:`-R` option: a random value is used to seed the hashes of str,
bytes and datetime objects.
If :envvar:`PYTHONHASHSEED` is set to an integer value, it is used as a
fixed seed for generating the hash() of the types covered by the hash
randomization.
Its purpose is to allow repeatable hashing, such as for selftests for the
interpreter itself, or to allow a cluster of python processes to share hash
values.
The integer must be a decimal number in the range [0,4294967295].
Specifying the value 0 will lead to the same hash values as when hash
randomization is disabled.
.. versionadded:: 2.6.8
.. envvar:: PYTHONIOENCODING
Overrides the encoding used for stdin/stdout/stderr, in the syntax

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@ -506,6 +506,12 @@ PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
PyAPI_FUNC(long) _Py_HashDouble(double);
PyAPI_FUNC(long) _Py_HashPointer(void*);
typedef struct {
long prefix;
long suffix;
} _Py_HashSecret_t;
PyAPI_DATA(_Py_HashSecret_t) _Py_HashSecret;
/* Helper for passing objects to printf and the like */
#define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))

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@ -26,6 +26,7 @@ PyAPI_DATA(int) Py_NoUserSiteDirectory;
PyAPI_DATA(int) _Py_QnewFlag;
/* Warn about 3.x issues */
PyAPI_DATA(int) Py_Py3kWarningFlag;
PyAPI_DATA(int) Py_HashRandomizationFlag;
/* this is a wrapper around getenv() that pays attention to
Py_IgnoreEnvironmentFlag. It should be used for getting variables like

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@ -168,6 +168,8 @@ typedef void (*PyOS_sighandler_t)(int);
PyAPI_FUNC(PyOS_sighandler_t) PyOS_getsig(int);
PyAPI_FUNC(PyOS_sighandler_t) PyOS_setsig(int, PyOS_sighandler_t);
/* Random */
PyAPI_FUNC(int) _PyOS_URandom (void *buffer, Py_ssize_t size);
#ifdef __cplusplus
}

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@ -742,22 +742,3 @@ try:
_make_statvfs_result)
except NameError: # statvfs_result may not exist
pass
if not _exists("urandom"):
def urandom(n):
"""urandom(n) -> str
Return a string of n random bytes suitable for cryptographic use.
"""
try:
_urandomfd = open("/dev/urandom", O_RDONLY)
except (OSError, IOError):
raise NotImplementedError("/dev/urandom (or equivalent) not found")
try:
bs = b""
while n - len(bs) >= 1:
bs += read(_urandomfd, n - len(bs))
finally:
close(_urandomfd)
return bs

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@ -103,6 +103,20 @@ class CmdLineTest(unittest.TestCase):
self.exit_code('-c', 'pass'),
0)
def test_hash_randomization(self):
# Verify that -R enables hash randomization:
self.verify_valid_flag('-R')
hashes = []
for i in range(2):
code = 'print(hash("spam"))'
data = self.start_python('-R', '-c', code)
hashes.append(data)
self.assertNotEqual(hashes[0], hashes[1])
# Verify that sys.flags contains hash_randomization
code = 'import sys; print sys.flags'
data = self.start_python('-R', '-c', code)
self.assertTrue('hash_randomization=1' in data)
def test_main():
test.test_support.run_unittest(CmdLineTest)

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@ -3,10 +3,18 @@
#
# Also test that hash implementations are inherited as expected
import os
import sys
import struct
import datetime
import unittest
import subprocess
from test import test_support
from collections import Hashable
IS_64BIT = (struct.calcsize('l') == 8)
class HashEqualityTestCase(unittest.TestCase):
@ -133,10 +141,100 @@ class HashBuiltinsTestCase(unittest.TestCase):
for obj in self.hashes_to_check:
self.assertEqual(hash(obj), _default_hash(obj))
class HashRandomizationTests(unittest.TestCase):
# Each subclass should define a field "repr_", containing the repr() of
# an object to be tested
def get_hash_command(self, repr_):
return 'print(hash(%s))' % repr_
def get_hash(self, repr_, seed=None):
env = os.environ.copy()
if seed is not None:
env['PYTHONHASHSEED'] = str(seed)
else:
env.pop('PYTHONHASHSEED', None)
cmd_line = [sys.executable, '-c', self.get_hash_command(repr_)]
p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.STDOUT,
env=env)
out, err = p.communicate()
out = test_support.strip_python_stderr(out)
return int(out.strip())
def test_randomized_hash(self):
# two runs should return different hashes
run1 = self.get_hash(self.repr_, seed='random')
run2 = self.get_hash(self.repr_, seed='random')
self.assertNotEqual(run1, run2)
class StringlikeHashRandomizationTests(HashRandomizationTests):
def test_null_hash(self):
# PYTHONHASHSEED=0 disables the randomized hash
if IS_64BIT:
known_hash_of_obj = 1453079729188098211
else:
known_hash_of_obj = -1600925533
# Randomization is disabled by default:
self.assertEqual(self.get_hash(self.repr_), known_hash_of_obj)
# It can also be disabled by setting the seed to 0:
self.assertEqual(self.get_hash(self.repr_, seed=0), known_hash_of_obj)
def test_fixed_hash(self):
# test a fixed seed for the randomized hash
# Note that all types share the same values:
if IS_64BIT:
h = -4410911502303878509
else:
h = -206076799
self.assertEqual(self.get_hash(self.repr_, seed=42), h)
class StrHashRandomizationTests(StringlikeHashRandomizationTests):
repr_ = repr('abc')
def test_empty_string(self):
self.assertEqual(hash(""), 0)
class UnicodeHashRandomizationTests(StringlikeHashRandomizationTests):
repr_ = repr(u'abc')
def test_empty_string(self):
self.assertEqual(hash(u""), 0)
class BufferHashRandomizationTests(StringlikeHashRandomizationTests):
repr_ = 'buffer("abc")'
def test_empty_string(self):
self.assertEqual(hash(buffer("")), 0)
class DatetimeTests(HashRandomizationTests):
def get_hash_command(self, repr_):
return 'import datetime; print(hash(%s))' % repr_
class DatetimeDateTests(DatetimeTests):
repr_ = repr(datetime.date(1066, 10, 14))
class DatetimeDatetimeTests(DatetimeTests):
repr_ = repr(datetime.datetime(1, 2, 3, 4, 5, 6, 7))
class DatetimeTimeTests(DatetimeTests):
repr_ = repr(datetime.time(0))
def test_main():
test_support.run_unittest(HashEqualityTestCase,
HashInheritanceTestCase,
HashBuiltinsTestCase)
HashBuiltinsTestCase,
StrHashRandomizationTests,
UnicodeHashRandomizationTests,
BufferHashRandomizationTests,
DatetimeDateTests,
DatetimeDatetimeTests,
DatetimeTimeTests)
if __name__ == "__main__":

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@ -6,6 +6,8 @@ import os
import unittest
import warnings
import sys
import subprocess
from test import test_support
warnings.filterwarnings("ignore", "tempnam", RuntimeWarning, __name__)
@ -499,18 +501,46 @@ class DevNullTests (unittest.TestCase):
class URandomTests (unittest.TestCase):
def test_urandom(self):
try:
with test_support.check_warnings():
self.assertEqual(len(os.urandom(1)), 1)
self.assertEqual(len(os.urandom(10)), 10)
self.assertEqual(len(os.urandom(100)), 100)
self.assertEqual(len(os.urandom(1000)), 1000)
# see http://bugs.python.org/issue3708
self.assertEqual(len(os.urandom(0.9)), 0)
self.assertEqual(len(os.urandom(1.1)), 1)
self.assertEqual(len(os.urandom(2.0)), 2)
except NotImplementedError:
pass
with test_support.check_warnings():
self.assertEqual(len(os.urandom(1)), 1)
self.assertEqual(len(os.urandom(10)), 10)
self.assertEqual(len(os.urandom(100)), 100)
self.assertEqual(len(os.urandom(1000)), 1000)
# see http://bugs.python.org/issue3708
self.assertEqual(len(os.urandom(0.9)), 0)
self.assertEqual(len(os.urandom(1.1)), 1)
self.assertEqual(len(os.urandom(2.0)), 2)
def test_urandom_length(self):
self.assertEqual(len(os.urandom(0)), 0)
self.assertEqual(len(os.urandom(1)), 1)
self.assertEqual(len(os.urandom(10)), 10)
self.assertEqual(len(os.urandom(100)), 100)
self.assertEqual(len(os.urandom(1000)), 1000)
def test_urandom_value(self):
data1 = os.urandom(16)
data2 = os.urandom(16)
self.assertNotEqual(data1, data2)
def get_urandom_subprocess(self, count):
code = '\n'.join((
'import os, sys',
'data = os.urandom(%s)' % count,
'sys.stdout.write(data)',
'sys.stdout.flush()'))
cmd_line = [sys.executable, '-c', code]
p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
out, err = p.communicate()
out = test_support.strip_python_stderr(out)
self.assertEqual(len(out), count)
return out
def test_urandom_subprocess(self):
data1 = self.get_urandom_subprocess(16)
data2 = self.get_urandom_subprocess(16)
self.assertNotEqual(data1, data2)
class Win32ErrorTests(unittest.TestCase):
def test_rename(self):

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@ -6,7 +6,6 @@ import weakref
import operator
import copy
import pickle
import os
from random import randrange, shuffle
import sys
import collections
@ -688,6 +687,17 @@ class TestBasicOps(unittest.TestCase):
if self.repr is not None:
self.assertEqual(repr(self.set), self.repr)
def check_repr_against_values(self):
text = repr(self.set)
self.assertTrue(text.startswith('{'))
self.assertTrue(text.endswith('}'))
result = text[1:-1].split(', ')
result.sort()
sorted_repr_values = [repr(value) for value in self.values]
sorted_repr_values.sort()
self.assertEqual(result, sorted_repr_values)
def test_print(self):
fo = open(test_support.TESTFN, "wb")
try:
@ -837,6 +847,46 @@ class TestBasicOpsTriple(TestBasicOps):
self.length = 3
self.repr = None
#------------------------------------------------------------------------------
class TestBasicOpsString(TestBasicOps):
def setUp(self):
self.case = "string set"
self.values = ["a", "b", "c"]
self.set = set(self.values)
self.dup = set(self.values)
self.length = 3
def test_repr(self):
self.check_repr_against_values()
#------------------------------------------------------------------------------
class TestBasicOpsUnicode(TestBasicOps):
def setUp(self):
self.case = "unicode set"
self.values = [u"a", u"b", u"c"]
self.set = set(self.values)
self.dup = set(self.values)
self.length = 3
def test_repr(self):
self.check_repr_against_values()
#------------------------------------------------------------------------------
class TestBasicOpsMixedStringUnicode(TestBasicOps):
def setUp(self):
self.case = "string and bytes set"
self.values = ["a", "b", u"a", u"b"]
self.set = set(self.values)
self.dup = set(self.values)
self.length = 4
def test_repr(self):
with test_support.check_warnings():
self.check_repr_against_values()
#==============================================================================
def baditer():

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@ -24,7 +24,7 @@ __all__ = ["Error", "TestFailed", "TestSkipped", "ResourceDenied", "import_modul
"captured_stdout", "TransientResource", "transient_internet",
"run_with_locale", "set_memlimit", "bigmemtest", "bigaddrspacetest",
"BasicTestRunner", "run_unittest", "run_doctest", "threading_setup",
"threading_cleanup", "reap_children"]
"threading_cleanup", "reap_children", "strip_python_stderr"]
class Error(Exception):
"""Base class for regression test exceptions."""
@ -893,3 +893,13 @@ def reap_children():
break
except:
break
def strip_python_stderr(stderr):
"""Strip the stderr of a Python process from potential debug output
emitted by the interpreter.
This will typically be run on the result of the communicate() method
of a subprocess.Popen object.
"""
stderr = re.sub(br"\[\d+ refs\]\r?\n?$", b"", stderr).strip()
return stderr

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@ -105,10 +105,11 @@ class SymtableTest(unittest.TestCase):
def test_function_info(self):
func = self.spam
self.assertEqual(func.get_parameters(), ("a", "b", "kw", "var"))
self.assertEqual(func.get_locals(),
self.assertEqual(
tuple(sorted(func.get_parameters())), ("a", "b", "kw", "var"))
self.assertEqual(tuple(sorted(func.get_locals())),
("a", "b", "bar", "internal", "kw", "var", "x"))
self.assertEqual(func.get_globals(), ("bar", "glob"))
self.assertEqual(tuple(sorted(func.get_globals())), ("bar", "glob"))
self.assertEqual(self.internal.get_frees(), ("x",))
def test_globals(self):

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@ -384,7 +384,7 @@ class SysModuleTest(unittest.TestCase):
attrs = ("debug", "py3k_warning", "division_warning", "division_new",
"inspect", "interactive", "optimize", "dont_write_bytecode",
"no_site", "ignore_environment", "tabcheck", "verbose",
"unicode", "bytes_warning")
"unicode", "bytes_warning", "hash_randomization")
for attr in attrs:
self.assert_(hasattr(sys.flags, attr), attr)
self.assertEqual(type(getattr(sys.flags, attr)), int, attr)

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@ -280,6 +280,7 @@ PYTHON_OBJS= \
Python/pymath.o \
Python/pystate.o \
Python/pythonrun.o \
Python/random.o \
Python/structmember.o \
Python/symtable.o \
Python/sysmodule.o \
@ -708,7 +709,7 @@ buildbottest: all platform
-@if which pybuildbot.identify >/dev/null 2>&1; then \
pybuildbot.identify "CC='$(CC)'" "CXX='$(CXX)'"; \
fi
$(TESTPYTHON) $(TESTPROG) -uall -rw $(TESTOPTS)
$(TESTPYTHON) -R $(TESTPROG) -uall -rw $(TESTOPTS)
QUICKTESTOPTS= $(TESTOPTS) -x test_thread test_signal test_strftime \
test_unicodedata test_re test_sre test_select test_poll \

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@ -10,6 +10,11 @@ What's New in Python 2.6.8 rc 1?
Core and Builtins
-----------------
- Issue #13703: oCERT-2011-003: add -R command-line option and PYTHONHASHSEED
environment variable, to provide an opt-in way to protect against denial of
service attacks due to hash collisions within the dict and set types. Patch
by David Malcolm, based on work by Victor Stinner.
Library
-------

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@ -34,6 +34,9 @@ python \- an interpreted, interactive, object-oriented programming language
.B \-O0
]
[
.B \-R
]
[
.B -Q
.I argument
]
@ -151,6 +154,18 @@ to \fI.pyo\fP. Given twice, causes docstrings to be discarded.
.B \-O0
Discard docstrings in addition to the \fB-O\fP optimizations.
.TP
.B \-R
Turn on "hash randomization", so that the hash() values of str, bytes and
datetime objects are "salted" with an unpredictable pseudo-random value.
Although they remain constant within an individual Python process, they are
not predictable between repeated invocations of Python.
.IP
This is intended to provide protection against a denial of service
caused by carefully-chosen inputs that exploit the worst case performance
of a dict insertion, O(n^2) complexity. See
http://www.ocert.org/advisories/ocert-2011-003.html
for details.
.TP
.BI "\-Q " argument
Division control; see PEP 238. The argument must be one of "old" (the
default, int/int and long/long return an int or long), "new" (new
@ -411,6 +426,20 @@ the \fB\-u\fP option.
If this is set to a non-empty string it is equivalent to specifying
the \fB\-v\fP option. If set to an integer, it is equivalent to
specifying \fB\-v\fP multiple times.
.IP PYTHONHASHSEED
If this variable is set to "random", the effect is the same as specifying
the \fB-R\fP option: a random value is used to seed the hashes of str,
bytes and datetime objects.
If PYTHONHASHSEED is set to an integer value, it is used as a fixed seed for
generating the hash() of the types covered by the hash randomization. Its
purpose is to allow repeatable hashing, such as for selftests for the
interpreter itself, or to allow a cluster of python processes to share hash
values.
The integer must be a decimal number in the range [0,4294967295]. Specifying
the value 0 will lead to the same hash values as when hash randomization is
disabled.
.SH AUTHOR
The Python Software Foundation: http://www.python.org/psf
.SH INTERNET RESOURCES

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@ -40,7 +40,7 @@ static char **orig_argv;
static int orig_argc;
/* command line options */
#define BASE_OPTS "3bBc:dEhiJm:OQ:sStuUvVW:xX?"
#define BASE_OPTS "3bBc:dEhiJm:OQ:RsStuUvVW:xX?"
#ifndef RISCOS
#define PROGRAM_OPTS BASE_OPTS
@ -71,6 +71,9 @@ static char *usage_2 = "\
-m mod : run library module as a script (terminates option list)\n\
-O : optimize generated bytecode slightly; also PYTHONOPTIMIZE=x\n\
-OO : remove doc-strings in addition to the -O optimizations\n\
-R : use a pseudo-random salt to make hash() values of various types be\n\
unpredictable between separate invocations of the interpreter, as\n\
a defense against denial-of-service attacks\n\
-Q arg : division options: -Qold (default), -Qwarn, -Qwarnall, -Qnew\n\
-s : don't add user site directory to sys.path; also PYTHONNOUSERSITE\n\
-S : don't imply 'import site' on initialization\n\
@ -101,6 +104,12 @@ PYTHONHOME : alternate <prefix> directory (or <prefix>%c<exec_prefix>).\n\
PYTHONCASEOK : ignore case in 'import' statements (Windows).\n\
PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.\n\
";
static char *usage_6 = "\
PYTHONHASHSEED: if this variable is set to ``random``, the effect is the same \n\
as specifying the :option:`-R` option: a random value is used to seed the\n\
hashes of str, bytes and datetime objects. It can also be set to an integer\n\
in the range [0,4294967295] to get hash values with a predictable seed.\n\
";
static int
@ -117,6 +126,7 @@ usage(int exitcode, char* program)
fputs(usage_3, f);
fprintf(f, usage_4, DELIM);
fprintf(f, usage_5, DELIM, PYTHONHOMEHELP);
fputs(usage_6, f);
}
#if defined(__VMS)
if (exitcode == 0) {
@ -388,6 +398,10 @@ Py_Main(int argc, char **argv)
PySys_AddWarnOption(_PyOS_optarg);
break;
case 'R':
Py_HashRandomizationFlag++;
break;
/* This space reserved for other options */
default:

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@ -8371,117 +8371,35 @@ posix_getloadavg(PyObject *self, PyObject *noargs)
}
#endif
#ifdef MS_WINDOWS
PyDoc_STRVAR(win32_urandom__doc__,
PyDoc_STRVAR(posix_urandom__doc__,
"urandom(n) -> str\n\n\
Return a string of n random bytes suitable for cryptographic use.");
Return n random bytes suitable for cryptographic use.");
typedef BOOL (WINAPI *CRYPTACQUIRECONTEXTA)(HCRYPTPROV *phProv,\
LPCSTR pszContainer, LPCSTR pszProvider, DWORD dwProvType,\
DWORD dwFlags );
typedef BOOL (WINAPI *CRYPTGENRANDOM)(HCRYPTPROV hProv, DWORD dwLen,\
BYTE *pbBuffer );
static CRYPTGENRANDOM pCryptGenRandom = NULL;
/* This handle is never explicitly released. Instead, the operating
system will release it when the process terminates. */
static HCRYPTPROV hCryptProv = 0;
static PyObject*
win32_urandom(PyObject *self, PyObject *args)
static PyObject *
posix_urandom(PyObject *self, PyObject *args)
{
int howMany;
PyObject* result;
Py_ssize_t size;
PyObject *result;
int ret;
/* Read arguments */
if (! PyArg_ParseTuple(args, "i:urandom", &howMany))
/* Read arguments */
if (!PyArg_ParseTuple(args, "n:urandom", &size))
return NULL;
if (howMany < 0)
if (size < 0)
return PyErr_Format(PyExc_ValueError,
"negative argument not allowed");
result = PyBytes_FromStringAndSize(NULL, size);
if (result == NULL)
return NULL;
if (hCryptProv == 0) {
HINSTANCE hAdvAPI32 = NULL;
CRYPTACQUIRECONTEXTA pCryptAcquireContext = NULL;
/* Obtain handle to the DLL containing CryptoAPI
This should not fail */
hAdvAPI32 = GetModuleHandle("advapi32.dll");
if(hAdvAPI32 == NULL)
return win32_error("GetModuleHandle", NULL);
/* Obtain pointers to the CryptoAPI functions
This will fail on some early versions of Win95 */
pCryptAcquireContext = (CRYPTACQUIRECONTEXTA)GetProcAddress(
hAdvAPI32,
"CryptAcquireContextA");
if (pCryptAcquireContext == NULL)
return PyErr_Format(PyExc_NotImplementedError,
"CryptAcquireContextA not found");
pCryptGenRandom = (CRYPTGENRANDOM)GetProcAddress(
hAdvAPI32, "CryptGenRandom");
if (pCryptGenRandom == NULL)
return PyErr_Format(PyExc_NotImplementedError,
"CryptGenRandom not found");
/* Acquire context */
if (! pCryptAcquireContext(&hCryptProv, NULL, NULL,
PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
return win32_error("CryptAcquireContext", NULL);
}
/* Allocate bytes */
result = PyString_FromStringAndSize(NULL, howMany);
if (result != NULL) {
/* Get random data */
memset(PyString_AS_STRING(result), 0, howMany); /* zero seed */
if (! pCryptGenRandom(hCryptProv, howMany, (unsigned char*)
PyString_AS_STRING(result))) {
Py_DECREF(result);
return win32_error("CryptGenRandom", NULL);
}
ret = _PyOS_URandom(PyBytes_AS_STRING(result),
PyBytes_GET_SIZE(result));
if (ret == -1) {
Py_DECREF(result);
return NULL;
}
return result;
}
#endif
#ifdef __VMS
/* Use openssl random routine */
#include <openssl/rand.h>
PyDoc_STRVAR(vms_urandom__doc__,
"urandom(n) -> str\n\n\
Return a string of n random bytes suitable for cryptographic use.");
static PyObject*
vms_urandom(PyObject *self, PyObject *args)
{
int howMany;
PyObject* result;
/* Read arguments */
if (! PyArg_ParseTuple(args, "i:urandom", &howMany))
return NULL;
if (howMany < 0)
return PyErr_Format(PyExc_ValueError,
"negative argument not allowed");
/* Allocate bytes */
result = PyString_FromStringAndSize(NULL, howMany);
if (result != NULL) {
/* Get random data */
if (RAND_pseudo_bytes((unsigned char*)
PyString_AS_STRING(result),
howMany) < 0) {
Py_DECREF(result);
return PyErr_Format(PyExc_ValueError,
"RAND_pseudo_bytes");
}
}
return result;
}
#endif
static PyMethodDef posix_methods[] = {
{"access", posix_access, METH_VARARGS, posix_access__doc__},
@ -8787,12 +8705,7 @@ static PyMethodDef posix_methods[] = {
#ifdef HAVE_GETLOADAVG
{"getloadavg", posix_getloadavg, METH_NOARGS, posix_getloadavg__doc__},
#endif
#ifdef MS_WINDOWS
{"urandom", win32_urandom, METH_VARARGS, win32_urandom__doc__},
#endif
#ifdef __VMS
{"urandom", vms_urandom, METH_VARARGS, vms_urandom__doc__},
#endif
{"urandom", posix_urandom, METH_VARARGS, posix_urandom__doc__},
{NULL, NULL} /* Sentinel */
};

View File

@ -334,10 +334,20 @@ buffer_hash(PyBufferObject *self)
return -1;
p = (unsigned char *) ptr;
len = size;
x = *p << 7;
/*
We make the hash of the empty buffer be 0, rather than using
(prefix ^ suffix), since this slightly obfuscates the hash secret
*/
if (len == 0) {
self->b_hash = 0;
return 0;
}
x = _Py_HashSecret.prefix;
x ^= *p << 7;
while (--len >= 0)
x = (1000003*x) ^ *p++;
x ^= size;
x ^= _Py_HashSecret.suffix;
if (x == -1)
x = -2;
self->b_hash = x;

View File

@ -1101,6 +1101,8 @@ PyObject_HashNotImplemented(PyObject *self)
return -1;
}
_Py_HashSecret_t _Py_HashSecret;
long
PyObject_Hash(PyObject *v)
{

View File

@ -1212,11 +1212,21 @@ string_hash(PyStringObject *a)
if (a->ob_shash != -1)
return a->ob_shash;
len = Py_SIZE(a);
/*
We make the hash of the empty string be 0, rather than using
(prefix ^ suffix), since this slightly obfuscates the hash secret
*/
if (len == 0) {
a->ob_shash = 0;
return 0;
}
p = (unsigned char *) a->ob_sval;
x = *p << 7;
x = _Py_HashSecret.prefix;
x ^= *p << 7;
while (--len >= 0)
x = (1000003*x) ^ *p++;
x ^= Py_SIZE(a);
x ^= _Py_HashSecret.suffix;
if (x == -1)
x = -2;
a->ob_shash = x;

View File

@ -6695,11 +6695,21 @@ unicode_hash(PyUnicodeObject *self)
if (self->hash != -1)
return self->hash;
len = PyUnicode_GET_SIZE(self);
/*
We make the hash of the empty string be 0, rather than using
(prefix ^ suffix), since this slightly obfuscates the hash secret
*/
if (len == 0) {
self->hash = 0;
return 0;
}
p = PyUnicode_AS_UNICODE(self);
x = *p << 7;
x = _Py_HashSecret.prefix;
x ^= *p << 7;
while (--len >= 0)
x = (1000003*x) ^ *p++;
x ^= PyUnicode_GET_SIZE(self);
x ^= _Py_HashSecret.suffix;
if (x == -1)
x = -2;
self->hash = x;

View File

@ -1778,6 +1778,10 @@
RelativePath="..\Python\pythonrun.c"
>
</File>
<File
RelativePath="..\Python\random.c"
>
</File>
<File
RelativePath="..\Python\structmember.c"
>

View File

@ -67,6 +67,7 @@ static void call_sys_exitfunc(void);
static void call_ll_exitfuncs(void);
extern void _PyUnicode_Init(void);
extern void _PyUnicode_Fini(void);
extern void _PyRandom_Init(void);
#ifdef WITH_THREAD
extern void _PyGILState_Init(PyInterpreterState *, PyThreadState *);
@ -89,6 +90,7 @@ int Py_IgnoreEnvironmentFlag; /* e.g. PYTHONPATH, PYTHONHOME */
true divisions (which they will be in 2.3). */
int _Py_QnewFlag = 0;
int Py_NoUserSiteDirectory = 0; /* for -s and site.py */
int Py_HashRandomizationFlag = 0; /* for -R and PYTHONHASHSEED */
/* PyModule_GetWarningsModule is no longer necessary as of 2.6
since _warnings is builtin. This API should not be used. */
@ -166,6 +168,12 @@ Py_InitializeEx(int install_sigs)
Py_OptimizeFlag = add_flag(Py_OptimizeFlag, p);
if ((p = Py_GETENV("PYTHONDONTWRITEBYTECODE")) && *p != '\0')
Py_DontWriteBytecodeFlag = add_flag(Py_DontWriteBytecodeFlag, p);
/* The variable is only tested for existence here; _PyRandom_Init will
check its value further. */
if ((p = Py_GETENV("PYTHONHASHSEED")) && *p != '\0')
Py_HashRandomizationFlag = add_flag(Py_HashRandomizationFlag, p);
_PyRandom_Init();
interp = PyInterpreterState_New();
if (interp == NULL)

302
Python/random.c Normal file
View File

@ -0,0 +1,302 @@
#include "Python.h"
#ifdef MS_WINDOWS
#include <windows.h>
#else
#include <fcntl.h>
#endif
static int random_initialized = 0;
#ifdef MS_WINDOWS
typedef BOOL (WINAPI *CRYPTACQUIRECONTEXTA)(HCRYPTPROV *phProv,\
LPCSTR pszContainer, LPCSTR pszProvider, DWORD dwProvType,\
DWORD dwFlags );
typedef BOOL (WINAPI *CRYPTGENRANDOM)(HCRYPTPROV hProv, DWORD dwLen,\
BYTE *pbBuffer );
static CRYPTGENRANDOM pCryptGenRandom = NULL;
/* This handle is never explicitly released. Instead, the operating
system will release it when the process terminates. */
static HCRYPTPROV hCryptProv = 0;
static int
win32_urandom_init(int raise)
{
HINSTANCE hAdvAPI32 = NULL;
CRYPTACQUIRECONTEXTA pCryptAcquireContext = NULL;
/* Obtain handle to the DLL containing CryptoAPI. This should not fail. */
hAdvAPI32 = GetModuleHandle("advapi32.dll");
if(hAdvAPI32 == NULL)
goto error;
/* Obtain pointers to the CryptoAPI functions. This will fail on some early
versions of Win95. */
pCryptAcquireContext = (CRYPTACQUIRECONTEXTA)GetProcAddress(
hAdvAPI32, "CryptAcquireContextA");
if (pCryptAcquireContext == NULL)
goto error;
pCryptGenRandom = (CRYPTGENRANDOM)GetProcAddress(hAdvAPI32,
"CryptGenRandom");
if (pCryptGenRandom == NULL)
goto error;
/* Acquire context */
if (! pCryptAcquireContext(&hCryptProv, NULL, NULL,
PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
goto error;
return 0;
error:
if (raise)
PyErr_SetFromWindowsErr(0);
else
Py_FatalError("Failed to initialize Windows random API (CryptoGen)");
return -1;
}
/* Fill buffer with size pseudo-random bytes generated by the Windows CryptoGen
API. Return 0 on success, or -1 on error. */
static int
win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
{
Py_ssize_t chunk;
if (hCryptProv == 0)
{
if (win32_urandom_init(raise) == -1)
return -1;
}
while (size > 0)
{
chunk = size > INT_MAX ? INT_MAX : size;
if (!pCryptGenRandom(hCryptProv, chunk, buffer))
{
/* CryptGenRandom() failed */
if (raise)
PyErr_SetFromWindowsErr(0);
else
Py_FatalError("Failed to initialized the randomized hash "
"secret using CryptoGen)");
return -1;
}
buffer += chunk;
size -= chunk;
}
return 0;
}
#endif /* MS_WINDOWS */
#ifdef __VMS
/* Use openssl random routine */
#include <openssl/rand.h>
static int
vms_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
{
if (RAND_pseudo_bytes(buffer, size) < 0) {
if (raise) {
PyErr_Format(PyExc_ValueError,
"RAND_pseudo_bytes");
} else {
Py_FatalError("Failed to initialize the randomized hash "
"secret using RAND_pseudo_bytes");
}
return -1;
}
return 0;
}
#endif /* __VMS */
#if !defined(MS_WINDOWS) && !defined(__VMS)
/* Read size bytes from /dev/urandom into buffer.
Call Py_FatalError() on error. */
static void
dev_urandom_noraise(char *buffer, Py_ssize_t size)
{
int fd;
Py_ssize_t n;
assert (0 < size);
fd = open("/dev/urandom", O_RDONLY);
if (fd < 0)
Py_FatalError("Failed to open /dev/urandom");
while (0 < size)
{
do {
n = read(fd, buffer, (size_t)size);
} while (n < 0 && errno == EINTR);
if (n <= 0)
{
/* stop on error or if read(size) returned 0 */
Py_FatalError("Failed to read bytes from /dev/urandom");
break;
}
buffer += n;
size -= (Py_ssize_t)n;
}
close(fd);
}
/* Read size bytes from /dev/urandom into buffer.
Return 0 on success, raise an exception and return -1 on error. */
static int
dev_urandom_python(char *buffer, Py_ssize_t size)
{
int fd;
Py_ssize_t n;
if (size <= 0)
return 0;
Py_BEGIN_ALLOW_THREADS
fd = open("/dev/urandom", O_RDONLY);
Py_END_ALLOW_THREADS
if (fd < 0)
{
PyErr_SetFromErrnoWithFilename(PyExc_OSError, "/dev/urandom");
return -1;
}
Py_BEGIN_ALLOW_THREADS
do {
do {
n = read(fd, buffer, (size_t)size);
} while (n < 0 && errno == EINTR);
if (n <= 0)
break;
buffer += n;
size -= (Py_ssize_t)n;
} while (0 < size);
Py_END_ALLOW_THREADS
if (n <= 0)
{
/* stop on error or if read(size) returned 0 */
if (n < 0)
PyErr_SetFromErrno(PyExc_OSError);
else
PyErr_Format(PyExc_RuntimeError,
"Failed to read %zi bytes from /dev/urandom",
size);
close(fd);
return -1;
}
close(fd);
return 0;
}
#endif /* !defined(MS_WINDOWS) && !defined(__VMS) */
/* Fill buffer with pseudo-random bytes generated by a linear congruent
generator (LCG):
x(n+1) = (x(n) * 214013 + 2531011) % 2^32
Use bits 23..16 of x(n) to generate a byte. */
static void
lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
{
size_t index;
unsigned int x;
x = x0;
for (index=0; index < size; index++) {
x *= 214013;
x += 2531011;
/* modulo 2 ^ (8 * sizeof(int)) */
buffer[index] = (x >> 16) & 0xff;
}
}
/* Fill buffer with size pseudo-random bytes, not suitable for cryptographic
use, from the operating random number generator (RNG).
Return 0 on success, raise an exception and return -1 on error. */
int
_PyOS_URandom(void *buffer, Py_ssize_t size)
{
if (size < 0) {
PyErr_Format(PyExc_ValueError,
"negative argument not allowed");
return -1;
}
if (size == 0)
return 0;
#ifdef MS_WINDOWS
return win32_urandom((unsigned char *)buffer, size, 1);
#else
# ifdef __VMS
return vms_urandom((unsigned char *)buffer, size, 1);
# else
return dev_urandom_python((char*)buffer, size);
# endif
#endif
}
void
_PyRandom_Init(void)
{
char *env;
void *secret = &_Py_HashSecret;
Py_ssize_t secret_size = sizeof(_Py_HashSecret);
if (random_initialized)
return;
random_initialized = 1;
/*
By default, hash randomization is disabled, and only
enabled if PYTHONHASHSEED is set to non-empty or if
"-R" is provided at the command line:
*/
if (!Py_HashRandomizationFlag) {
/* Disable the randomized hash: */
memset(secret, 0, secret_size);
return;
}
/*
Hash randomization is enabled. Generate a per-process secret,
using PYTHONHASHSEED if provided.
*/
env = Py_GETENV("PYTHONHASHSEED");
if (env && *env != '\0' && strcmp(env, "random") != 0) {
char *endptr = env;
unsigned long seed;
seed = strtoul(env, &endptr, 10);
if (*endptr != '\0'
|| seed > 4294967295UL
|| (errno == ERANGE && seed == ULONG_MAX))
{
Py_FatalError("PYTHONHASHSEED must be \"random\" or an integer "
"in range [0; 4294967295]");
}
if (seed == 0) {
/* disable the randomized hash */
memset(secret, 0, secret_size);
}
else {
lcg_urandom(seed, (unsigned char*)secret, secret_size);
}
}
else {
#ifdef MS_WINDOWS
(void)win32_urandom((unsigned char *)secret, secret_size, 0);
#else /* #ifdef MS_WINDOWS */
# ifdef __VMS
vms_urandom((unsigned char *)secret, secret_size, 0);
# else
dev_urandom_noraise((char*)secret, secret_size);
# endif
#endif
}
}

View File

@ -1224,6 +1224,7 @@ static PyStructSequence_Field flags_fields[] = {
{"unicode", "-U"},
/* {"skip_first", "-x"}, */
{"bytes_warning", "-b"},
{"hash_randomization", "-R"},
{0}
};
@ -1232,9 +1233,9 @@ static PyStructSequence_Desc flags_desc = {
flags__doc__, /* doc */
flags_fields, /* fields */
#ifdef RISCOS
16
17
#else
15
16
#endif
};
@ -1271,6 +1272,7 @@ make_flags(void)
SetFlag(Py_UnicodeFlag);
/* SetFlag(skipfirstline); */
SetFlag(Py_BytesWarningFlag);
SetFlag(Py_HashRandomizationFlag);
#undef SetFlag
if (PyErr_Occurred()) {