diff options
Diffstat (limited to 'Python/random.c')
| -rw-r--r-- | Python/random.c | 143 |
1 files changed, 107 insertions, 36 deletions
diff --git a/Python/random.c b/Python/random.c index 3f307cf..9c9d505 100644 --- a/Python/random.c +++ b/Python/random.c @@ -1,11 +1,14 @@ #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_GETRANDOM_SYSCALL +# include <sys/syscall.h> +# endif #endif #ifdef Py_DEBUG @@ -102,13 +105,74 @@ py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal) return 0; } -#else +#else /* !HAVE_GETENTROPY */ + +#ifdef HAVE_GETRANDOM_SYSCALL +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; + + /* Use syscall() because the libc doesn't expose getrandom() yet, see: + * https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */ + if (raise) { + Py_BEGIN_ALLOW_THREADS + n = syscall(SYS_getrandom, buffer, size, flags); + Py_END_ALLOW_THREADS + } + else { + n = syscall(SYS_getrandom, buffer, size, flags); + } + + if (n < 0) { + if (errno == ENOSYS) { + getrandom_works = 0; + return 0; + } + + if (errno == EINTR) { + /* Note: EINTR should not occur with flags=0 */ + 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 @@ -119,7 +183,14 @@ dev_urandom_noraise(unsigned char *buffer, Py_ssize_t size) assert (0 < size); - fd = _Py_open("/dev/urandom", O_RDONLY); +#ifdef HAVE_GETRANDOM_SYSCALL + if (py_getrandom(buffer, size, 0) == 1) + return; + /* 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) Py_FatalError("Failed to open /dev/urandom"); @@ -147,14 +218,27 @@ dev_urandom_python(char *buffer, Py_ssize_t size) { int fd; Py_ssize_t n; - struct stat st; + struct _Py_stat_struct st; +#ifdef HAVE_GETRANDOM_SYSCALL + int res; +#endif if (size <= 0) return 0; +#ifdef HAVE_GETRANDOM_SYSCALL + 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) + 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, @@ -166,17 +250,13 @@ dev_urandom_python(char *buffer, Py_ssize_t size) if (urandom_cache.fd >= 0) fd = urandom_cache.fd; else { - Py_BEGIN_ALLOW_THREADS fd = _Py_open("/dev/urandom", O_RDONLY); - Py_END_ALLOW_THREADS - if (fd < 0) - { + if (fd < 0) { if (errno == ENOENT || errno == ENXIO || errno == ENODEV || errno == EACCES) PyErr_SetString(PyExc_NotImplementedError, "/dev/urandom (or equivalent) not found"); - else - PyErr_SetFromErrno(PyExc_OSError); + /* otherwise, keep the OSError exception raised by _Py_open() */ return -1; } if (urandom_cache.fd >= 0) { @@ -186,8 +266,7 @@ dev_urandom_python(char *buffer, Py_ssize_t size) fd = urandom_cache.fd; } else { - if (fstat(fd, &st)) { - PyErr_SetFromErrno(PyExc_OSError); + if (_Py_fstat(fd, &st)) { close(fd); return -1; } @@ -199,29 +278,21 @@ dev_urandom_python(char *buffer, Py_ssize_t size) } } - Py_BEGIN_ALLOW_THREADS do { - do { - n = read(fd, buffer, (size_t)size); - } while (n < 0 && errno == EINTR); - if (n <= 0) - break; + 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 -= (Py_ssize_t)n; + size -= n; } while (0 < size); - Py_END_ALLOW_THREADS - if (n <= 0) - { - /* stop on error or if read(size) returned 0 */ - if (n < 0) - PyErr_SetFromErrno(PyExc_OSError); - else - PyErr_Format(PyExc_RuntimeError, - "Failed to read %zi bytes from /dev/urandom", - size); - return -1; - } return 0; } |