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Issue #27776: Cleanup random.c

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Merge dev_urandom_python() and dev_urandom_noraise() functions to reduce code
duplication.
This commit is contained in:
Victor Stinner 2016-08-16 18:46:38 +02:00
parent cecdd9634b
commit 6974cf2c27
1 changed files with 111 additions and 122 deletions
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233
Python/random.c
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@ -77,7 +77,7 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
}
/* Issue #25003: Don't use getentropy() on Solaris (available since
* Solaris 11.3), it is blocking whereas os.urandom() should not block. */
Solaris 11.3), it is blocking whereas os.urandom() should not block. */
#elif defined(HAVE_GETENTROPY) && !defined(sun)
#define PY_GETENTROPY 1
@ -119,25 +119,32 @@ py_getentropy(char *buffer, Py_ssize_t size, int raise)
#if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
#define PY_GETRANDOM 1
/* Call getrandom()
- Return 1 on success
- Return 0 if getrandom() syscall is not available (fails with ENOSYS).
- Raise an exception (if raise is non-zero) and return -1 on error:
getrandom() failed with EINTR and the Python signal handler raised an
exception, or getrandom() failed with a different error. */
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 newer, or Solaris 11.3 or newer */
Need Linux kernel 3.17 or newer, or Solaris 11.3 or newer */
static int getrandom_works = 1;
/* getrandom() on Linux will block if called before the kernel has
* initialized the urandom entropy pool. This will cause Python
* to hang on startup if called very early in the boot process -
* see https://bugs.python.org/issue26839. To avoid this, use the
* GRND_NONBLOCK flag. */
initialized the urandom entropy pool. This will cause Python
to hang on startup if called very early in the boot process -
see https://bugs.python.org/issue26839. To avoid this, use the
GRND_NONBLOCK flag. */
const int flags = GRND_NONBLOCK;
char *dest;
long n;
if (!getrandom_works)
if (!getrandom_works) {
return 0;
}
dest = buffer;
while (0 < size) {
@ -161,8 +168,8 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
}
#else
/* On Linux, use the syscall() function because the GNU libc doesn't
* expose the Linux getrandom() syscall yet. See:
* https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
expose the Linux getrandom() syscall yet. See:
https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
if (raise) {
Py_BEGIN_ALLOW_THREADS
n = syscall(SYS_getrandom, dest, n, flags);
@ -180,12 +187,12 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
}
if (errno == EAGAIN) {
/* If we failed with EAGAIN, the entropy pool was
* uninitialized. In this case, we return failure to fall
* back to reading from /dev/urandom.
*
* Note: In this case the data read will not be random so
* should not be used for cryptographic purposes. Retaining
* the existing semantics for practical purposes. */
uninitialized. In this case, we return failure to fall
back to reading from /dev/urandom.
Note: In this case the data read will not be random so
should not be used for cryptographic purposes. Retaining
the existing semantics for practical purposes. */
getrandom_works = 0;
return 0;
}
@ -221,130 +228,117 @@ static struct {
} urandom_cache = { -1 };
/* Read size bytes from /dev/urandom into buffer.
Return 0 success, or return -1 on error. */
/* Read 'size' random bytes from getrandom(). Fall back on reading from
/dev/urandom if getrandom() is not available.
Return 0 on success. Raise an exception (if raise is non-zero) and return -1
on error. */
static int
dev_urandom_noraise(char *buffer, Py_ssize_t size)
dev_urandom(char *buffer, Py_ssize_t size, int raise)
{
int fd;
Py_ssize_t n;
assert (0 < size);
#ifdef PY_GETRANDOM
if (py_getrandom(buffer, size, 0) == 1) {
return 0;
}
/* getrandom() is not supported by the running kernel, fall back
* on reading /dev/urandom */
#endif
fd = _Py_open_noraise("/dev/urandom", O_RDONLY);
if (fd < 0) {
return -1;
}
while (0 < size)
{
do {
n = read(fd, buffer, (size_t)size);
} while (n < 0 && errno == EINTR);
if (n <= 0) {
/* stop on error or if read(size) returned 0 */
return -1;
}
buffer += n;
size -= n;
}
close(fd);
return 0;
}
/* Read size bytes from /dev/urandom into buffer.
Return 0 on success, raise an exception and return -1 on error. */
static int
dev_urandom_python(char *buffer, Py_ssize_t size)
{
int fd;
Py_ssize_t n;
struct _Py_stat_struct st;
#ifdef PY_GETRANDOM
int res;
#endif
if (size <= 0)
return 0;
assert(size > 0);
#ifdef PY_GETRANDOM
res = py_getrandom(buffer, size, 1);
if (res < 0)
res = py_getrandom(buffer, size, raise);
if (res < 0) {
return -1;
if (res == 1)
}
if (res == 1) {
return 0;
}
/* getrandom() is not supported by the running kernel, fall back
* on reading /dev/urandom */
on reading /dev/urandom */
#endif
if (urandom_cache.fd >= 0) {
/* Does the fd point to the same thing as before? (issue #21207) */
if (_Py_fstat_noraise(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 {
fd = _Py_open("/dev/urandom", O_RDONLY);
if (fd < 0) {
if (errno == ENOENT || errno == ENXIO ||
errno == ENODEV || errno == EACCES)
PyErr_SetString(PyExc_NotImplementedError,
"/dev/urandom (or equivalent) not found");
/* otherwise, keep the OSError exception raised by _Py_open() */
return -1;
}
if (raise) {
struct _Py_stat_struct st;
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_cache.fd;
/* Does the fd point to the same thing as before? (issue #21207) */
if (_Py_fstat_noraise(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 {
if (_Py_fstat(fd, &st)) {
close(fd);
fd = _Py_open("/dev/urandom", O_RDONLY);
if (fd < 0) {
if (errno == ENOENT || errno == ENXIO ||
errno == ENODEV || errno == EACCES)
PyErr_SetString(PyExc_NotImplementedError,
"/dev/urandom (or equivalent) not found");
/* otherwise, keep the OSError exception raised by _Py_open() */
return -1;
}
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_cache.fd;
}
else {
urandom_cache.fd = fd;
urandom_cache.st_dev = st.st_dev;
urandom_cache.st_ino = st.st_ino;
if (_Py_fstat(fd, &st)) {
close(fd);
return -1;
}
else {
urandom_cache.fd = fd;
urandom_cache.st_dev = st.st_dev;
urandom_cache.st_ino = st.st_ino;
}
}
}
}
do {
n = _Py_read(fd, buffer, (size_t)size);
if (n == -1)
return -1;
if (n == 0) {
PyErr_Format(PyExc_RuntimeError,
"Failed to read %zi bytes from /dev/urandom",
size);
do {
n = _Py_read(fd, buffer, (size_t)size);
if (n == -1)
return -1;
if (n == 0) {
PyErr_Format(PyExc_RuntimeError,
"Failed to read %zi bytes from /dev/urandom",
size);
return -1;
}
buffer += n;
size -= n;
} while (0 < size);
}
else {
fd = _Py_open_noraise("/dev/urandom", O_RDONLY);
if (fd < 0) {
return -1;
}
buffer += n;
size -= n;
} while (0 < size);
while (0 < size)
{
do {
n = read(fd, buffer, (size_t)size);
} while (n < 0 && errno == EINTR);
if (n <= 0) {
/* stop on error or if read(size) returned 0 */
return -1;
}
buffer += n;
size -= n;
}
close(fd);
}
return 0;
}
@ -381,10 +375,10 @@ lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
}
/* If raise is zero:
* - Don't raise exceptions on error
* - Don't call PyErr_CheckSignals() on EINTR (retry directly the interrupted
* syscall)
* - Don't release the GIL to call syscalls. */
- Don't raise exceptions on error
- Don't call PyErr_CheckSignals() on EINTR (retry directly the interrupted
syscall)
- Don't release the GIL to call syscalls. */
static int
pyurandom(void *buffer, Py_ssize_t size, int raise)
{
@ -405,12 +399,7 @@ pyurandom(void *buffer, Py_ssize_t size, int raise)
#elif defined(PY_GETENTROPY)
return py_getentropy(buffer, size, raise);
#else
if (raise) {
return dev_urandom_python(buffer, size);
}
else {
return dev_urandom_noraise(buffer, size);
}
return dev_urandom(buffer, size, raise);
#endif
}
@ -466,7 +455,7 @@ _PyRandom_Init(void)
int res;
/* _PyRandom_Init() is called very early in the Python initialization
* and so exceptions cannot be used. */
and so exceptions cannot be used (use raise=0). */
res = pyurandom(secret, secret_size, 0);
if (res < 0) {
Py_FatalError("failed to get random numbers to initialize Python");