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/* -*- C -*- */
/*
* Uses Windows CryptoAPI CryptGenRandom to get random bytes
*
* Distribute and use freely; there are no restrictions on further
* dissemination and usage except those imposed by the laws of your
* country of residence. This software is provided "as is" without
* warranty of fitness for use or suitability for any purpose, express
* or implied. Use at your own risk or not at all.
*
*/
/* Author: Mark Moraes */
#include "Python.h"
#ifdef MS_WIN32
#define _WIN32_WINNT 0x400
#define WINSOCK
#include <windows.h>
#include <wincrypt.h>
LPVOID PrintWindowsError(char* msg, DWORD error)
{
LPVOID lpMsgBuf;
if (!FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, error,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
(LPTSTR) &lpMsgBuf,
0,
NULL )) {
fprintf(stderr, "FormatMessage had an error when processing this error (%d) and this message (%s)!", error, msg);
}
fprintf(stderr, "%s: %s\n", msg, lpMsgBuf);
LocalFree(lpMsgBuf);
}
static char winrandom__doc__[] =
"winrandom(nbytes): Returns nbytes of random data from Windows CryptGenRandom,"
"a cryptographically strong pseudo-random generator using system entropy";
static PyObject *
winrandom(PyObject *self, PyObject *args)
{
HCRYPTPROV hcp = 0;
int n, nbytes;
PyObject *res;
char *buf;
if (!PyArg_ParseTuple(args, "i", &n)) {
return NULL;
}
/* Just in case char != BYTE */
nbytes = (n * sizeof(char)) / sizeof(BYTE);
if (nbytes <= 0) {
PyErr_SetString(PyExc_ValueError, "nbytes must be positive number");
return NULL;
}
if ((buf = (char *) PyMem_Malloc(nbytes)) == NULL)
return PyErr_NoMemory();
if (! CryptAcquireContext(&hcp, NULL, NULL, PROV_RSA_FULL, 0)) {
// If the last error was a bad keyset, then it might be
// because we need to generate a keyset, so we call
// CryptAcquireContext again in order to try to create
// a key set this time.
DWORD lastError = GetLastError();
if (lastError == NTE_BAD_KEYSET) {
if (!CryptAcquireContext(&hcp, NULL, NULL, PROV_RSA_FULL,
CRYPT_NEWKEYSET)) {
lastError = GetLastError();
} else {
lastError = 0;
}
}
if (lastError != 0) {
PyErr_Format(PyExc_SystemError,
"CryptAcquireContext failed, error %i",
lastError);
PrintWindowsError("CryptAcquireContext failed", lastError);
PyMem_Free(buf);
return NULL;
}
}
if (! CryptGenRandom(hcp, (DWORD) nbytes, (BYTE *) buf)) {
PyErr_Format(PyExc_SystemError,
"CryptGenRandom failed, error %i",
GetLastError());
PyMem_Free(buf);
(void) CryptReleaseContext(hcp, 0);
return NULL;
}
if (! CryptReleaseContext(hcp, 0)) {
PyErr_Format(PyExc_SystemError,
"CryptReleaseContext failed, error %i",
GetLastError());
return NULL;
}
res = PyString_FromStringAndSize(buf, n);
PyMem_Free(buf);
return res;
}
static PyMethodDef WRMethods[] = {
{"winrandom", (PyCFunction) winrandom, METH_VARARGS, winrandom__doc__},
{NULL, NULL} /* Sentinel */
};
void
initwinrandom()
{
(void) Py_InitModule("winrandom", WRMethods);
}
#endif /* MS_WIN32 */
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