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.
diff --git a/Modules/Setup b/Modules/Setup
index 9dcca13..6f0374a 100644
--- a/Modules/Setup
+++ b/Modules/Setup
@@ -174,7 +174,7 @@
#_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 9076275..560460b 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 @@
/* 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 @@
_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 @@
}
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 @@
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 @@
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 @@
_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 a467811..dda78f6 100644
--- a/Modules/clinic/_randommodule.c.h
+++ b/Modules/clinic/_randommodule.c.h
@@ -114,4 +114,45 @@
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]*/