diff options
Diffstat (limited to 'Python/random.c')
| -rw-r--r-- | Python/random.c | 340 |
1 files changed, 175 insertions, 165 deletions
diff --git a/Python/random.c b/Python/random.c index f2ada5f..6f9f711 100644 --- a/Python/random.c +++ b/Python/random.c @@ -1,6 +1,9 @@ #include "Python.h" #ifdef MS_WINDOWS # include <windows.h> +/* All sample MSDN wincrypt programs include the header below. It is at least + * required with Min GW. */ +# include <wincrypt.h> #else # include <fcntl.h> # ifdef HAVE_SYS_STAT_H @@ -36,10 +39,9 @@ win32_urandom_init(int raise) return 0; error: - if (raise) + if (raise) { PyErr_SetFromWindowsErr(0); - else - Py_FatalError("Failed to initialize Windows random API (CryptoGen)"); + } return -1; } @@ -52,8 +54,9 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise) if (hCryptProv == 0) { - if (win32_urandom_init(raise) == -1) + if (win32_urandom_init(raise) == -1) { return -1; + } } while (size > 0) @@ -62,11 +65,9 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise) if (!CryptGenRandom(hCryptProv, (DWORD)chunk, buffer)) { /* CryptGenRandom() failed */ - if (raise) + if (raise) { PyErr_SetFromWindowsErr(0); - else - Py_FatalError("Failed to initialized the randomized hash " - "secret using CryptoGen)"); + } return -1; } buffer += chunk; @@ -83,29 +84,28 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise) /* Fill buffer with size pseudo-random bytes generated by getentropy(). Return 0 on success, or raise an exception and return -1 on error. - If fatal is nonzero, call Py_FatalError() instead of raising an exception - on error. */ + If raise is zero, don't raise an exception on error. */ static int -py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal) +py_getentropy(char *buffer, Py_ssize_t size, int raise) { while (size > 0) { Py_ssize_t len = Py_MIN(size, 256); int res; - if (!fatal) { + if (raise) { Py_BEGIN_ALLOW_THREADS res = getentropy(buffer, len); Py_END_ALLOW_THREADS - - if (res < 0) { - PyErr_SetFromErrno(PyExc_OSError); - return -1; - } } else { res = getentropy(buffer, len); - if (res < 0) - Py_FatalError("getentropy() failed"); + } + + if (res < 0) { + if (raise) { + PyErr_SetFromErrno(PyExc_OSError); + } + return -1; } buffer += len; @@ -128,25 +128,22 @@ py_getentropy(unsigned char *buffer, Py_ssize_t size, int fatal) 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) +py_getrandom(void *buffer, Py_ssize_t size, int blocking, int raise) { /* Is getrandom() supported by the running kernel? Set to 0 if getrandom() failed with ENOSYS or EPERM. 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. */ - const int flags = GRND_NONBLOCK; + int flags; + char *dest; long n; if (!getrandom_works) { return 0; } + flags = blocking ? 0 : GRND_NONBLOCK; + dest = buffer; while (0 < size) { #ifdef sun /* Issue #26735: On Solaris, getrandom() is limited to returning up @@ -160,23 +157,23 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise) #ifdef HAVE_GETRANDOM if (raise) { Py_BEGIN_ALLOW_THREADS - n = getrandom(buffer, n, flags); + n = getrandom(dest, n, flags); Py_END_ALLOW_THREADS } else { - n = getrandom(buffer, n, flags); + n = getrandom(dest, n, flags); } #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, buffer, n, flags); + n = syscall(SYS_getrandom, dest, n, flags); Py_END_ALLOW_THREADS } else { - n = syscall(SYS_getrandom, buffer, n, flags); + n = syscall(SYS_getrandom, dest, n, flags); } #endif @@ -188,40 +185,33 @@ py_getrandom(void *buffer, Py_ssize_t size, int raise) getrandom_works = 0; return 0; } - if (errno == EAGAIN) { - /* 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; + + /* getrandom(GRND_NONBLOCK) fails with EAGAIN if the system urandom + is not initialiazed yet. For _PyRandom_Init(), we ignore their + error and fall back on reading /dev/urandom which never blocks, + even if the system urandom is not initialized yet. */ + if (errno == EAGAIN && !raise && !blocking) { return 0; } if (errno == EINTR) { - if (PyErr_CheckSignals()) { - if (!raise) { - Py_FatalError("getrandom() interrupted by a signal"); + if (raise) { + if (PyErr_CheckSignals()) { + return -1; } - return -1; } - /* retry getrandom() */ + /* retry getrandom() if it was interrupted by a signal */ continue; } if (raise) { PyErr_SetFromErrno(PyExc_OSError); } - else { - Py_FatalError("getrandom() failed"); - } return -1; } - buffer += n; + dest += n; size -= n; } return 1; @@ -238,64 +228,21 @@ static struct { /* 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) -{ - int fd; - Py_ssize_t n; - - assert (0 < size); - -#ifdef PY_GETRANDOM - if (py_getrandom(buffer, size, 0) == 1) { - return; - } - /* getrandom() failed with ENOSYS or EPERM, - 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"); - } - - while (0 < size) - { - do { - n = read(fd, buffer, (size_t)size); - } while (n < 0 && errno == EINTR); - - if (n <= 0) { - /* read() failed or returned 0 bytes */ - Py_FatalError("Failed to read bytes from /dev/urandom"); - break; - } - buffer += n; - size -= n; - } - close(fd); -} - -/* 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. */ + Return 0 on success. Raise an exception (if raise is non-zero) and return -1 + on error. */ static int -dev_urandom_python(char *buffer, Py_ssize_t size) +dev_urandom(char *buffer, Py_ssize_t size, int blocking, int raise) { 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); + res = py_getrandom(buffer, size, blocking, raise); if (res < 0) { return -1; } @@ -306,64 +253,90 @@ dev_urandom_python(char *buffer, Py_ssize_t size) 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 (_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 */ + close(fd); + return -1; + } + buffer += n; + size -= n; + } + close(fd); + } return 0; } @@ -399,38 +372,71 @@ lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size) } } -/* Fill buffer with size pseudo-random bytes from the operating system random - number generator (RNG). It is suitable for most cryptographic purposes - except long living private keys for asymmetric encryption. - - Return 0 on success, raise an exception and return -1 on error. */ -int -_PyOS_URandom(void *buffer, Py_ssize_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. */ +static int +pyurandom(void *buffer, Py_ssize_t size, int blocking, int raise) { if (size < 0) { - PyErr_Format(PyExc_ValueError, - "negative argument not allowed"); + if (raise) { + PyErr_Format(PyExc_ValueError, + "negative argument not allowed"); + } return -1; } - if (size == 0) + + if (size == 0) { return 0; + } #ifdef MS_WINDOWS - return win32_urandom((unsigned char *)buffer, size, 1); + return win32_urandom((unsigned char *)buffer, size, raise); #elif defined(PY_GETENTROPY) - return py_getentropy(buffer, size, 0); + return py_getentropy(buffer, size, raise); #else - return dev_urandom_python((char*)buffer, size); + return dev_urandom(buffer, size, blocking, raise); #endif } +/* Fill buffer with size pseudo-random bytes from the operating system random + number generator (RNG). It is suitable for most cryptographic purposes + except long living private keys for asymmetric encryption. + + On Linux 3.17 and newer, the getrandom() syscall is used in blocking mode: + block until the system urandom entropy pool is initialized (128 bits are + collected by the kernel). + + Return 0 on success. Raise an exception and return -1 on error. */ +int +_PyOS_URandom(void *buffer, Py_ssize_t size) +{ + return pyurandom(buffer, size, 1, 1); +} + +/* Fill buffer with size pseudo-random bytes from the operating system random + number generator (RNG). It is not suitable for cryptographic purpose. + + On Linux 3.17 and newer (when getrandom() syscall is used), if the system + urandom is not initialized yet, the function returns "weak" entropy read + from /dev/urandom. + + Return 0 on success. Raise an exception and return -1 on error. */ +int +_PyOS_URandomNonblock(void *buffer, Py_ssize_t size) +{ + return pyurandom(buffer, size, 0, 1); +} + void _PyRandom_Init(void) { char *env; unsigned char *secret = (unsigned char *)&_Py_HashSecret.uc; Py_ssize_t secret_size = sizeof(_Py_HashSecret_t); - assert(secret_size == sizeof(_Py_HashSecret.uc)); + Py_BUILD_ASSERT(sizeof(_Py_HashSecret_t) == sizeof(_Py_HashSecret.uc)); if (_Py_HashSecret_Initialized) return; @@ -462,13 +468,17 @@ _PyRandom_Init(void) } } else { -#ifdef MS_WINDOWS - (void)win32_urandom(secret, secret_size, 0); -#elif defined(PY_GETENTROPY) - (void)py_getentropy(secret, secret_size, 1); -#else - dev_urandom_noraise(secret, secret_size); -#endif + int res; + + /* _PyRandom_Init() is called very early in the Python initialization + and so exceptions cannot be used (use raise=0). + + _PyRandom_Init() must not block Python initialization: call + pyurandom() is non-blocking mode (blocking=0): see the PEP 524. */ + res = pyurandom(secret, secret_size, 0, 0); + if (res < 0) { + Py_FatalError("failed to get random numbers to initialize Python"); + } } } |