339 lines
8.4 KiB
C
339 lines
8.4 KiB
C
#include "Python.h"
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#ifdef MS_WINDOWS
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#include <windows.h>
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#else
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#include <fcntl.h>
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#ifdef HAVE_SYS_STAT_H
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#include <sys/stat.h>
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#endif
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#endif
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#ifdef Py_DEBUG
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int _Py_HashSecret_Initialized = 0;
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#else
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static int _Py_HashSecret_Initialized = 0;
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#endif
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#ifdef MS_WINDOWS
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static HCRYPTPROV hCryptProv = 0;
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static int
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win32_urandom_init(int raise)
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{
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/* Acquire context */
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if (!CryptAcquireContext(&hCryptProv, NULL, NULL,
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PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
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goto error;
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return 0;
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error:
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if (raise)
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PyErr_SetFromWindowsErr(0);
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else
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Py_FatalError("Failed to initialize Windows random API (CryptoGen)");
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return -1;
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}
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/* Fill buffer with size pseudo-random bytes generated by the Windows CryptoGen
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API. Return 0 on success, or raise an exception and return -1 on error. */
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static int
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win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
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{
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Py_ssize_t chunk;
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if (hCryptProv == 0)
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{
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if (win32_urandom_init(raise) == -1)
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return -1;
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}
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while (size > 0)
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{
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chunk = size > INT_MAX ? INT_MAX : size;
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if (!CryptGenRandom(hCryptProv, (DWORD)chunk, buffer))
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{
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/* CryptGenRandom() failed */
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if (raise)
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PyErr_SetFromWindowsErr(0);
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else
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Py_FatalError("Failed to initialized the randomized hash "
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"secret using CryptoGen)");
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return -1;
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}
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buffer += chunk;
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size -= chunk;
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}
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return 0;
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}
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#elif HAVE_GETENTROPY
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/* Fill buffer with size pseudo-random bytes generated by getentropy().
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Return 0 on success, or raise an exception and return -1 on error.
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If fatal is nonzero, call Py_FatalError() instead of raising an exception
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on error. */
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static int
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py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal)
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{
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while (size > 0) {
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Py_ssize_t len = Py_MIN(size, 256);
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int res = getentropy(buffer, len);
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if (res < 0) {
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if (fatal) {
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Py_FatalError("getentropy() failed");
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}
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else {
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PyErr_SetFromErrno(PyExc_OSError);
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return -1;
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}
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}
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buffer += len;
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size -= len;
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}
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return 0;
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}
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#else
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static struct {
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int fd;
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dev_t st_dev;
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ino_t st_ino;
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} urandom_cache = { -1 };
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/* Read size bytes from /dev/urandom into buffer.
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Call Py_FatalError() on error. */
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static void
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dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)
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{
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int fd;
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Py_ssize_t n;
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assert (0 < size);
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fd = _Py_open("/dev/urandom", O_RDONLY);
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if (fd < 0)
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Py_FatalError("Failed to open /dev/urandom");
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while (0 < size)
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{
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do {
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n = read(fd, buffer, (size_t)size);
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} while (n < 0 && errno == EINTR);
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if (n <= 0)
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{
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/* stop on error or if read(size) returned 0 */
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Py_FatalError("Failed to read bytes from /dev/urandom");
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break;
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}
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buffer += n;
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size -= (Py_ssize_t)n;
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}
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close(fd);
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}
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/* Read size bytes from /dev/urandom into buffer.
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Return 0 on success, raise an exception and return -1 on error. */
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static int
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dev_urandom_python(char *buffer, Py_ssize_t size)
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{
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int fd;
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Py_ssize_t n;
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struct _Py_stat_struct st;
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if (size <= 0)
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return 0;
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if (urandom_cache.fd >= 0) {
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/* Does the fd point to the same thing as before? (issue #21207) */
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if (_Py_fstat(urandom_cache.fd, &st)
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|| st.st_dev != urandom_cache.st_dev
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|| st.st_ino != urandom_cache.st_ino) {
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/* Something changed: forget the cached fd (but don't close it,
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since it probably points to something important for some
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third-party code). */
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urandom_cache.fd = -1;
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}
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}
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if (urandom_cache.fd >= 0)
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fd = urandom_cache.fd;
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else {
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Py_BEGIN_ALLOW_THREADS
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fd = _Py_open("/dev/urandom", O_RDONLY);
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Py_END_ALLOW_THREADS
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if (fd < 0)
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{
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if (errno == ENOENT || errno == ENXIO ||
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errno == ENODEV || errno == EACCES)
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PyErr_SetString(PyExc_NotImplementedError,
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"/dev/urandom (or equivalent) not found");
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else
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PyErr_SetFromErrno(PyExc_OSError);
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return -1;
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}
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if (urandom_cache.fd >= 0) {
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/* urandom_fd was initialized by another thread while we were
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not holding the GIL, keep it. */
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close(fd);
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fd = urandom_cache.fd;
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}
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else {
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if (_Py_fstat(fd, &st)) {
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PyErr_SetFromErrno(PyExc_OSError);
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close(fd);
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return -1;
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}
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else {
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urandom_cache.fd = fd;
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urandom_cache.st_dev = st.st_dev;
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urandom_cache.st_ino = st.st_ino;
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}
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}
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}
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Py_BEGIN_ALLOW_THREADS
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do {
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do {
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n = read(fd, buffer, (size_t)size);
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} while (n < 0 && errno == EINTR);
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if (n <= 0)
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break;
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buffer += n;
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size -= (Py_ssize_t)n;
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} while (0 < size);
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Py_END_ALLOW_THREADS
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if (n <= 0)
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{
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/* stop on error or if read(size) returned 0 */
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if (n < 0)
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PyErr_SetFromErrno(PyExc_OSError);
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else
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PyErr_Format(PyExc_RuntimeError,
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"Failed to read %zi bytes from /dev/urandom",
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size);
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return -1;
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}
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return 0;
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}
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static void
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dev_urandom_close(void)
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{
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if (urandom_cache.fd >= 0) {
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close(urandom_cache.fd);
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urandom_cache.fd = -1;
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}
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}
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#endif /* HAVE_GETENTROPY */
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/* Fill buffer with pseudo-random bytes generated by a linear congruent
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generator (LCG):
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x(n+1) = (x(n) * 214013 + 2531011) % 2^32
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Use bits 23..16 of x(n) to generate a byte. */
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static void
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lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
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{
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size_t index;
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unsigned int x;
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x = x0;
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for (index=0; index < size; index++) {
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x *= 214013;
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x += 2531011;
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/* modulo 2 ^ (8 * sizeof(int)) */
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buffer[index] = (x >> 16) & 0xff;
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}
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}
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/* Fill buffer with size pseudo-random bytes from the operating system random
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number generator (RNG). It is suitable for most cryptographic purposes
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except long living private keys for asymmetric encryption.
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Return 0 on success, raise an exception and return -1 on error. */
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int
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_PyOS_URandom(void *buffer, Py_ssize_t size)
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{
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if (size < 0) {
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PyErr_Format(PyExc_ValueError,
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"negative argument not allowed");
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return -1;
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}
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if (size == 0)
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return 0;
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#ifdef MS_WINDOWS
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return win32_urandom((unsigned char *)buffer, size, 1);
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#elif HAVE_GETENTROPY
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return py_getentropy(buffer, size, 0);
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#else
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return dev_urandom_python((char*)buffer, size);
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#endif
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}
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void
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_PyRandom_Init(void)
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{
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char *env;
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unsigned char *secret = (unsigned char *)&_Py_HashSecret.uc;
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Py_ssize_t secret_size = sizeof(_Py_HashSecret_t);
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assert(secret_size == sizeof(_Py_HashSecret.uc));
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if (_Py_HashSecret_Initialized)
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return;
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_Py_HashSecret_Initialized = 1;
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/*
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Hash randomization is enabled. Generate a per-process secret,
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using PYTHONHASHSEED if provided.
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*/
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env = Py_GETENV("PYTHONHASHSEED");
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if (env && *env != '\0' && strcmp(env, "random") != 0) {
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char *endptr = env;
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unsigned long seed;
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seed = strtoul(env, &endptr, 10);
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if (*endptr != '\0'
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|| seed > 4294967295UL
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|| (errno == ERANGE && seed == ULONG_MAX))
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{
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Py_FatalError("PYTHONHASHSEED must be \"random\" or an integer "
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"in range [0; 4294967295]");
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}
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if (seed == 0) {
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/* disable the randomized hash */
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memset(secret, 0, secret_size);
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}
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else {
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lcg_urandom(seed, secret, secret_size);
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}
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}
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else {
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#ifdef MS_WINDOWS
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(void)win32_urandom(secret, secret_size, 0);
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#elif HAVE_GETENTROPY
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(void)py_getentropy(secret, secret_size, 1);
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#else
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dev_urandom_noraise(secret, secret_size);
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#endif
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}
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}
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void
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_PyRandom_Fini(void)
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{
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#ifdef MS_WINDOWS
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if (hCryptProv) {
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CryptReleaseContext(hCryptProv, 0);
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hCryptProv = 0;
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}
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#elif HAVE_GETENTROPY
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/* nothing to clean */
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#else
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dev_urandom_close();
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#endif
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}
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