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changeset: 102701:86d0d74bc2e1 user: Victor Stinner victor.stinner@gmail.com date: Tue Aug 16 18:46:38 2016 +0200 files: Python/random.c description: Issue #27776: Cleanup random.c Merge dev_urandom_python() and dev_urandom_noraise() functions to reduce code duplication. diff -r 265644bad99e -r 86d0d74bc2e1 Python/random.c --- a/Python/random.c Tue Aug 16 15:19:09 2016 +0200 +++ b/Python/random.c Tue Aug 16 18:46:38 2016 +0200 @@ -77,7 +77,7 @@ } /* 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 @@ #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 @@ } #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 @@ } 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 @@ } 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 (raise) { + struct _Py_stat_struct st; + + 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 (urandom_cache.fd >= 0) { - /* urandom_fd was initialized by another thread while we were - not holding the GIL, keep it. */ - close(fd); + 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 @@ } /* 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 @@ #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 @@ 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"); /victor.stinner@gmail.com