Rietveld Code Review Tool
Help | Bug tracker | Discussion group | Source code | Sign in
(181045)

Unified Diff: Python/random.c

Issue 22181: os.urandom() should use Linux 3.17 getrandom() syscall
Patch Set: Created 4 years, 4 months ago
Use n/p to move between diff chunks; N/P to move between comments. Please Sign in to add in-line comments.
Jump to:
View side-by-side diff with in-line comments
Download patch
« no previous file with comments | « no previous file | no next file » | no next file with comments »
Expand Comments ('e') | Collapse Comments ('c') | Show Comments Hide Comments ('s')
--- a/Python/random.c Tue Feb 17 23:36:19 2015 +0100
+++ b/Python/random.c Tue Mar 03 03:00:15 2015 +0100
@@ -1,11 +1,17 @@
#include "Python.h"
#ifdef MS_WINDOWS
-#include <windows.h>
+# include <windows.h>
#else
-#include <fcntl.h>
-#ifdef HAVE_SYS_STAT_H
-#include <sys/stat.h>
-#endif
+# include <fcntl.h>
+# ifdef HAVE_SYS_STAT_H
+# include <sys/stat.h>
+# endif
+# ifdef HAVE_SYS_SYSCALL_H
+# include <sys/syscall.h>
+# if defined(__linux__) && defined(SYS_getrandom)
+# define HAVE_GETRANDOM
+# endif
+# endif
#endif
#ifdef Py_DEBUG
@@ -94,13 +100,64 @@ py_getentropy(unsigned char *buffer, Py_
return 0;
}
-#else
+#else /* !HAVE_GETENTROPY */
+
+#ifdef HAVE_GETRANDOM
+static int
+py_getrandom(void *buffer, Py_ssize_t size, int raise)
+{
+ /* is getrandom() supported by the running kernel?
+ * need Linux kernel 3.17 or later */
+ static int getrandom_works = 1;
+ /* Use /dev/urandom, block if the kernel has no entropy */
+ const int flags = 0;
+ int n;
+
+ if (!getrandom_works)
+ return 0;
+
+ while (0 < size) {
+ errno = 0;
+ /* the libc doesn't expose getrandom() yet, see:
+ * https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
+ n = syscall(SYS_getrandom, buffer, size, flags);
+ if (n < 0) {
+ if (errno == ENOSYS) {
+ getrandom_works = 0;
+ return 0;
+ }
+
+ if (errno == EINTR) {
+ if (PyErr_CheckSignals()) {
+ if (!raise)
+ Py_FatalError("getrandom() interrupted by a signal");
+ return -1;
+ }
+ /* retry getrandom() */
+ continue;
+ }
+
+ if (raise)
+ PyErr_SetFromErrno(PyExc_OSError);
+ else
+ Py_FatalError("getrandom() failed");
+ return -1;
+ }
+
+ buffer += n;
+ size -= n;
+ }
+ return 1;
+}
+#endif
+
static struct {
int fd;
dev_t st_dev;
ino_t st_ino;
} urandom_cache = { -1 };
+
/* Read size bytes from /dev/urandom into buffer.
Call Py_FatalError() on error. */
static void
@@ -115,6 +172,13 @@ dev_urandom_noraise(unsigned char *buffe
if (fd < 0)
Py_FatalError("Failed to open /dev/urandom");
+#ifdef HAVE_GETRANDOM
+ if (py_getrandom(buffer, size, 0) == 1)
+ return;
+ /* getrandom() is not supported by the running kernel, fall back
+ * on reading /dev/urandom */
+#endif
+
while (0 < size)
{
do {
@@ -140,10 +204,23 @@ dev_urandom_python(char *buffer, Py_ssiz
int fd;
Py_ssize_t n;
struct stat st;
+#ifdef HAVE_GETRANDOM
+ int res;
+#endif
if (size <= 0)
return 0;
+#ifdef HAVE_GETRANDOM
+ res = py_getrandom(buffer, size, 1);
+ if (res < 0)
+ return -1;
+ if (res == 1)
+ return 0;
+ /* getrandom() is not supported by the running kernel, fall back
+ * on reading /dev/urandom */
+#endif
+
if (urandom_cache.fd >= 0) {
/* Does the fd point to the same thing as before? (issue #21207) */
if (fstat(urandom_cache.fd, &st)
« no previous file with comments | « no previous file | no next file » | no next file with comments »

RSS Feeds Recent Issues | This issue
This is Rietveld 894c83f36cb7+