[Python-checkins] bpo-40286: Add randbytes() method to random.Random (GH-19527)
Victor Stinner
webhook-mailer at python.org
Fri Apr 17 13:05:51 EDT 2020
https://github.com/python/cpython/commit/9f5fe7910f4a1bf5a425837d4915e332b945eb7b
commit: 9f5fe7910f4a1bf5a425837d4915e332b945eb7b
branch: master
author: Victor Stinner <vstinner at python.org>
committer: GitHub <noreply at github.com>
date: 2020-04-17T19:05:35+02:00
summary:
bpo-40286: Add randbytes() method to random.Random (GH-19527)
Add random.randbytes() function and random.Random.randbytes()
method to generate random bytes.
Modify secrets.token_bytes() to use SystemRandom.randbytes()
rather than calling directly os.urandom().
Rename also genrand_int32() to genrand_uint32(), since it returns an
unsigned 32-bit integer, not a signed integer.
The _random module is now built with Py_BUILD_CORE_MODULE defined.
files:
A Misc/NEWS.d/next/Library/2020-04-15-00-39-25.bpo-40286.ai80FA.rst
M Doc/library/random.rst
M Doc/whatsnew/3.9.rst
M Lib/random.py
M Lib/secrets.py
M Lib/test/test_random.py
M Modules/Setup
M Modules/_randommodule.c
M Modules/clinic/_randommodule.c.h
M setup.py
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index 1eb39bbda42e8..51242cb0e9581 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -112,6 +112,13 @@ Bookkeeping functions
:meth:`randrange` to handle arbitrarily large ranges.
+.. function:: randbytes(n)
+
+ Generate *n* random bytes.
+
+ .. versionadded:: 3.9
+
+
Functions for integers
----------------------
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index aae8e5b0c9716..2b36b0f154b31 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -353,6 +353,12 @@ The documentation string is now shown not only for class, function,
method etc, but for any object that has its own ``__doc__`` attribute.
(Contributed by Serhiy Storchaka in :issue:`40257`.)
+random
+------
+
+Add a new :attr:`random.Random.randbytes` method: generate random bytes.
+(Contributed by Victor Stinner in :issue:`40286`.)
+
signal
------
diff --git a/Lib/random.py b/Lib/random.py
index e24737d4508a8..82345fab92131 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -739,6 +739,12 @@ def getrandbits(self, k):
x = int.from_bytes(_urandom(numbytes), 'big')
return x >> (numbytes * 8 - k) # trim excess bits
+ def randbytes(self, n):
+ """Generate n random bytes."""
+ # os.urandom(n) fails with ValueError for n < 0
+ # and returns an empty bytes string for n == 0.
+ return _urandom(n)
+
def seed(self, *args, **kwds):
"Stub method. Not used for a system random number generator."
return None
@@ -819,6 +825,7 @@ def _test(N=2000):
getstate = _inst.getstate
setstate = _inst.setstate
getrandbits = _inst.getrandbits
+randbytes = _inst.randbytes
if hasattr(_os, "fork"):
_os.register_at_fork(after_in_child=_inst.seed)
diff --git a/Lib/secrets.py b/Lib/secrets.py
index 130434229e96a..a546efbdd4204 100644
--- a/Lib/secrets.py
+++ b/Lib/secrets.py
@@ -14,7 +14,6 @@
import base64
import binascii
-import os
from hmac import compare_digest
from random import SystemRandom
@@ -44,7 +43,7 @@ def token_bytes(nbytes=None):
"""
if nbytes is None:
nbytes = DEFAULT_ENTROPY
- return os.urandom(nbytes)
+ return _sysrand.randbytes(nbytes)
def token_hex(nbytes=None):
"""Return a random text string, in hexadecimal.
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index 548af706dbee2..f709e52ecb805 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -291,6 +291,22 @@ def test_bug_9025(self):
k = sum(randrange(6755399441055744) % 3 == 2 for i in range(n))
self.assertTrue(0.30 < k/n < .37, (k/n))
+ def test_randbytes(self):
+ # Verify ranges
+ for n in range(1, 10):
+ data = self.gen.randbytes(n)
+ self.assertEqual(type(data), bytes)
+ self.assertEqual(len(data), n)
+
+ self.assertEqual(self.gen.randbytes(0), b'')
+
+ # Verify argument checking
+ self.assertRaises(TypeError, self.gen.randbytes)
+ self.assertRaises(TypeError, self.gen.randbytes, 1, 2)
+ self.assertRaises(ValueError, self.gen.randbytes, -1)
+ self.assertRaises(TypeError, self.gen.randbytes, 1.0)
+
+
try:
random.SystemRandom().random()
except NotImplementedError:
@@ -747,6 +763,41 @@ def test_choices_algorithms(self):
c = self.gen.choices(population, cum_weights=cum_weights, k=10000)
self.assertEqual(a, c)
+ def test_randbytes(self):
+ super().test_randbytes()
+
+ # Mersenne Twister randbytes() is deterministic
+ # and does not depend on the endian and bitness.
+ seed = 8675309
+ expected = b'f\xf9\xa836\xd0\xa4\xf4\x82\x9f\x8f\x19\xf0eo\x02'
+
+ self.gen.seed(seed)
+ self.assertEqual(self.gen.randbytes(16), expected)
+
+ # randbytes(0) must not consume any entropy
+ self.gen.seed(seed)
+ self.assertEqual(self.gen.randbytes(0), b'')
+ self.assertEqual(self.gen.randbytes(16), expected)
+
+ # Four randbytes(4) calls give the same output than randbytes(16)
+ self.gen.seed(seed)
+ self.assertEqual(b''.join([self.gen.randbytes(4) for _ in range(4)]),
+ expected)
+
+ # Each randbytes(2) or randbytes(3) call consumes 4 bytes of entropy
+ self.gen.seed(seed)
+ expected2 = b''.join(expected[i:i + 2]
+ for i in range(0, len(expected), 4))
+ self.assertEqual(b''.join(self.gen.randbytes(2) for _ in range(4)),
+ expected2)
+
+ self.gen.seed(seed)
+ expected3 = b''.join(expected[i:i + 3]
+ for i in range(0, len(expected), 4))
+ self.assertEqual(b''.join(self.gen.randbytes(3) for _ in range(4)),
+ expected3)
+
+
def gamma(z, sqrt2pi=(2.0*pi)**0.5):
# Reflection to right half of complex plane
if z < 0.5:
diff --git a/Misc/NEWS.d/next/Library/2020-04-15-00-39-25.bpo-40286.ai80FA.rst b/Misc/NEWS.d/next/Library/2020-04-15-00-39-25.bpo-40286.ai80FA.rst
new file mode 100644
index 0000000000000..69c9cff10aa99
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-04-15-00-39-25.bpo-40286.ai80FA.rst
@@ -0,0 +1,2 @@
+Add :func:`random.randbytes` function and
+:meth:`random.Random.randbytes` method to generate random bytes.
diff --git a/Modules/Setup b/Modules/Setup
index 9dcca13100078..6f0374a206315 100644
--- a/Modules/Setup
+++ b/Modules/Setup
@@ -174,7 +174,7 @@ _symtable symtablemodule.c
#_weakref _weakref.c # basic weak reference support
#_testcapi _testcapimodule.c # Python C API test module
#_testinternalcapi _testinternalcapi.c -I$(srcdir)/Include/internal -DPy_BUILD_CORE_MODULE # Python internal C API test module
-#_random _randommodule.c # Random number generator
+#_random _randommodule.c -DPy_BUILD_CORE_MODULE # Random number generator
#_elementtree -I$(srcdir)/Modules/expat -DHAVE_EXPAT_CONFIG_H -DUSE_PYEXPAT_CAPI _elementtree.c # elementtree accelerator
#_pickle _pickle.c # pickle accelerator
#_datetime _datetimemodule.c # datetime accelerator
diff --git a/Modules/_randommodule.c b/Modules/_randommodule.c
index 90762758f9311..560460b9a44be 100644
--- a/Modules/_randommodule.c
+++ b/Modules/_randommodule.c
@@ -11,7 +11,7 @@
* renamed genrand_res53() to random_random() and wrapped
in python calling/return code.
- * genrand_int32() and the helper functions, init_genrand()
+ * genrand_uint32() and the helper functions, init_genrand()
and init_by_array(), were declared static, wrapped in
Python calling/return code. also, their global data
references were replaced with structure references.
@@ -67,9 +67,9 @@
/* ---------------------------------------------------------------*/
#include "Python.h"
-#include <time.h> /* for seeding to current time */
+#include "pycore_byteswap.h" // _Py_bswap32()
#ifdef HAVE_PROCESS_H
-# include <process.h> /* needed for getpid() */
+# include <process.h> // getpid()
#endif
/* Period parameters -- These are all magic. Don't change. */
@@ -116,7 +116,7 @@ class _random.Random "RandomObject *" "&Random_Type"
/* generates a random number on [0,0xffffffff]-interval */
static uint32_t
-genrand_int32(RandomObject *self)
+genrand_uint32(RandomObject *self)
{
uint32_t y;
static const uint32_t mag01[2] = {0x0U, MATRIX_A};
@@ -171,7 +171,7 @@ static PyObject *
_random_Random_random_impl(RandomObject *self)
/*[clinic end generated code: output=117ff99ee53d755c input=afb2a59cbbb00349]*/
{
- uint32_t a=genrand_int32(self)>>5, b=genrand_int32(self)>>6;
+ uint32_t a=genrand_uint32(self)>>5, b=genrand_uint32(self)>>6;
return PyFloat_FromDouble((a*67108864.0+b)*(1.0/9007199254740992.0));
}
@@ -481,7 +481,7 @@ _random_Random_getrandbits_impl(RandomObject *self, int k)
}
if (k <= 32) /* Fast path */
- return PyLong_FromUnsignedLong(genrand_int32(self) >> (32 - k));
+ return PyLong_FromUnsignedLong(genrand_uint32(self) >> (32 - k));
words = (k - 1) / 32 + 1;
wordarray = (uint32_t *)PyMem_Malloc(words * 4);
@@ -498,7 +498,7 @@ _random_Random_getrandbits_impl(RandomObject *self, int k)
for (i = words - 1; i >= 0; i--, k -= 32)
#endif
{
- r = genrand_int32(self);
+ r = genrand_uint32(self);
if (k < 32)
r >>= (32 - k); /* Drop least significant bits */
wordarray[i] = r;
@@ -510,6 +510,56 @@ _random_Random_getrandbits_impl(RandomObject *self, int k)
return result;
}
+/*[clinic input]
+
+_random.Random.randbytes
+
+ self: self(type="RandomObject *")
+ n: Py_ssize_t
+ /
+
+Generate n random bytes.
+[clinic start generated code]*/
+
+static PyObject *
+_random_Random_randbytes_impl(RandomObject *self, Py_ssize_t n)
+/*[clinic end generated code: output=67a28548079a17ea input=7ba658a24150d233]*/
+{
+ if (n < 0) {
+ PyErr_SetString(PyExc_ValueError,
+ "number of bytes must be non-negative");
+ return NULL;
+ }
+
+ if (n == 0) {
+ /* Don't consume any entropy */
+ return PyBytes_FromStringAndSize(NULL, 0);
+ }
+
+ PyObject *bytes = PyBytes_FromStringAndSize(NULL, n);
+ if (bytes == NULL) {
+ return NULL;
+ }
+ uint8_t *ptr = (uint8_t *)PyBytes_AS_STRING(bytes);
+
+ do {
+ uint32_t word = genrand_uint32(self);
+#if PY_LITTLE_ENDIAN
+ /* Convert to big endian */
+ word = _Py_bswap32(word);
+#endif
+ if (n < 4) {
+ memcpy(ptr, &word, n);
+ break;
+ }
+ memcpy(ptr, &word, 4);
+ ptr += 4;
+ n -= 4;
+ } while (n);
+
+ return bytes;
+}
+
static PyObject *
random_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
@@ -539,6 +589,7 @@ static PyMethodDef random_methods[] = {
_RANDOM_RANDOM_GETSTATE_METHODDEF
_RANDOM_RANDOM_SETSTATE_METHODDEF
_RANDOM_RANDOM_GETRANDBITS_METHODDEF
+ _RANDOM_RANDOM_RANDBYTES_METHODDEF
{NULL, NULL} /* sentinel */
};
diff --git a/Modules/clinic/_randommodule.c.h b/Modules/clinic/_randommodule.c.h
index a467811d93b27..dda78f6013cfe 100644
--- a/Modules/clinic/_randommodule.c.h
+++ b/Modules/clinic/_randommodule.c.h
@@ -114,4 +114,45 @@ _random_Random_getrandbits(RandomObject *self, PyObject *arg)
exit:
return return_value;
}
-/*[clinic end generated code: output=a7feb0c9c8d1b627 input=a9049054013a1b77]*/
+
+PyDoc_STRVAR(_random_Random_randbytes__doc__,
+"randbytes($self, n, /)\n"
+"--\n"
+"\n"
+"Generate n random bytes.");
+
+#define _RANDOM_RANDOM_RANDBYTES_METHODDEF \
+ {"randbytes", (PyCFunction)_random_Random_randbytes, METH_O, _random_Random_randbytes__doc__},
+
+static PyObject *
+_random_Random_randbytes_impl(RandomObject *self, Py_ssize_t n);
+
+static PyObject *
+_random_Random_randbytes(RandomObject *self, PyObject *arg)
+{
+ PyObject *return_value = NULL;
+ Py_ssize_t n;
+
+ if (PyFloat_Check(arg)) {
+ PyErr_SetString(PyExc_TypeError,
+ "integer argument expected, got float" );
+ goto exit;
+ }
+ {
+ Py_ssize_t ival = -1;
+ PyObject *iobj = PyNumber_Index(arg);
+ if (iobj != NULL) {
+ ival = PyLong_AsSsize_t(iobj);
+ Py_DECREF(iobj);
+ }
+ if (ival == -1 && PyErr_Occurred()) {
+ goto exit;
+ }
+ n = ival;
+ }
+ return_value = _random_Random_randbytes_impl(self, n);
+
+exit:
+ return return_value;
+}
+/*[clinic end generated code: output=e515c651860c4001 input=a9049054013a1b77]*/
diff --git a/setup.py b/setup.py
index 65a1cfab078c5..d241dc0b4b406 100644
--- a/setup.py
+++ b/setup.py
@@ -808,7 +808,8 @@ def detect_simple_extensions(self):
self.add(Extension('_datetime', ['_datetimemodule.c'],
libraries=['m']))
# random number generator implemented in C
- self.add(Extension("_random", ["_randommodule.c"]))
+ self.add(Extension("_random", ["_randommodule.c"],
+ extra_compile_args=['-DPy_BUILD_CORE_MODULE']))
# bisect
self.add(Extension("_bisect", ["_bisectmodule.c"]))
# heapq
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