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Issue #21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew.

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This commit is contained in:
Antoine Pitrou 2014-04-26 14:35:19 +02:00
commit 4432cf45c6
3 changed files with 85 additions and 10 deletions
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49
Python/random.c
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@ -3,6 +3,9 @@
#include <windows.h>
#else
#include <fcntl.h>
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#endif
#ifdef Py_DEBUG
@ -69,7 +72,11 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
#ifndef MS_WINDOWS
static int urandom_fd = -1;
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. */
@ -109,12 +116,24 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
{
int fd;
Py_ssize_t n;
struct stat st;
if (size <= 0)
return 0;
if (urandom_fd >= 0)
fd = urandom_fd;
if (urandom_cache.fd >= 0) {
/* Does the fd point to the same thing as before? (issue #21207) */
if (fstat(urandom_cache.fd, &st)
|| st.st_dev != urandom_cache.st_dev
|| st.st_ino != urandom_cache.st_ino) {
/* Something changed: forget the cached fd (but don't close it,
since it probably points to something important for some
third-party code). */
urandom_cache.fd = -1;
}
}
if (urandom_cache.fd >= 0)
fd = urandom_cache.fd;
else {
Py_BEGIN_ALLOW_THREADS
fd = _Py_open("/dev/urandom", O_RDONLY);
@ -129,14 +148,24 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
PyErr_SetFromErrno(PyExc_OSError);
return -1;
}
if (urandom_fd >= 0) {
if (urandom_cache.fd >= 0) {
/* urandom_fd was initialized by another thread while we were
not holding the GIL, keep it. */
close(fd);
fd = urandom_fd;
fd = urandom_cache.fd;
}
else {
if (fstat(fd, &st)) {
PyErr_SetFromErrno(PyExc_OSError);
close(fd);
return -1;
}
else {
urandom_cache.fd = fd;
urandom_cache.st_dev = st.st_dev;
urandom_cache.st_ino = st.st_ino;
}
}
else
urandom_fd = fd;
}
Py_BEGIN_ALLOW_THREADS
@ -168,9 +197,9 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
static void
dev_urandom_close(void)
{
if (urandom_fd >= 0) {
close(urandom_fd);
urandom_fd = -1;
if (urandom_cache.fd >= 0) {
close(urandom_cache.fd);
urandom_cache.fd = -1;
}
}