traverseda
/
cpython
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Cleanup random.c 

Issue #27955: modify py_getrnadom() and dev_urandom()

* Add comments from Python 3.7
* PEP 7 style: add {...}
This commit is contained in:
Victor Stinner 2016-09-20 22:26:18 +02:00
parent a327331cec
commit af59732102
1 changed files with 53 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

81
Python/random.c
View File

@ -119,11 +119,20 @@ py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal)
#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 (failed with ENOSYS)
or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom
not initialized yet) and raise=0.
- 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 */
/* Is getrandom() supported by the running kernel? Set to 0 if getrandom()
failed with ENOSYS. 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
@ -134,8 +143,9 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
const int flags = GRND_NONBLOCK;
long n;
if (!getrandom_works)
if (!getrandom_works) {
return 0;
}
while (0 < size) {
#ifdef sun
@ -171,36 +181,42 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise)
#endif
if (n < 0) {
/* ENOSYS: getrandom() syscall not supported by the kernel (but
* maybe supported by the host which built Python). */
if (errno == ENOSYS) {
getrandom_works = 0;
return 0;
}
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. */
/* getrandom(GRND_NONBLOCK) fails with EAGAIN if the system
urandom is not initialiazed yet. In this case, fall back on
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;
}
if (errno == EINTR) {
if (PyErr_CheckSignals()) {
if (!raise)
if (!raise) {
Py_FatalError("getrandom() interrupted by a signal");
}
return -1;
}
/* retry getrandom() */
continue;
}
if (raise)
if (raise) {
PyErr_SetFromErrno(PyExc_OSError);
else
}
else {
Py_FatalError("getrandom() failed");
}
return -1;
}
@ -218,7 +234,9 @@ static struct {
} urandom_cache = { -1 };
/* Read size bytes from /dev/urandom into buffer.
/* Read 'size' random bytes from py_getrandom(). Fall back on reading from
/dev/urandom if getrandom() is not available.
Call Py_FatalError() on error. */
static void
dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)
@ -229,24 +247,26 @@ dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)
assert (0 < size);
#ifdef PY_GETRANDOM
if (py_getrandom(buffer, size, 0) == 1)
if (py_getrandom(buffer, size, 0) == 1) {
return;
/* getrandom() is not supported by the running kernel, fall back
* on reading /dev/urandom */
}
/* getrandom() failed with ENOSYS,
fall back on reading /dev/urandom */
#endif
fd = _Py_open_noraise("/dev/urandom", O_RDONLY);
if (fd < 0)
if (fd < 0) {
Py_FatalError("Failed to open /dev/urandom");
}
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 */
if (n <= 0) {
/* read() failed or returned 0 bytes */
Py_FatalError("Failed to read bytes from /dev/urandom");
break;
}
@ -256,8 +276,10 @@ dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size)
close(fd);
}
/* Read size bytes from /dev/urandom into buffer.
Return 0 on success, raise an exception and return -1 on error. */
/* Read 'size' random bytes from py_getrandom(). Fall back on reading from
/dev/urandom if getrandom() is not available.
Return 0 on success. Raise an exception and return -1 on error. */
static int
dev_urandom_python(char *buffer, Py_ssize_t size)
{
@ -273,12 +295,14 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
#ifdef PY_GETRANDOM
res = py_getrandom(buffer, size, 1);
if (res < 0)
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 */
}
/* getrandom() failed with ENOSYS,
fall back on reading /dev/urandom */
#endif
if (urandom_cache.fd >= 0) {
@ -325,8 +349,9 @@ dev_urandom_python(char *buffer, Py_ssize_t size)
do {
n = _Py_read(fd, buffer, (size_t)size);
if (n == -1)
if (n == -1) {
return -1;
}
if (n == 0) {
PyErr_Format(PyExc_RuntimeError,
"Failed to read %zi bytes from /dev/urandom",