diff options
Diffstat (limited to 'lib/getrandom.c')
| -rw-r--r-- | lib/getrandom.c | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/lib/getrandom.c b/lib/getrandom.c new file mode 100644 index 0000000..f8695ab --- /dev/null +++ b/lib/getrandom.c @@ -0,0 +1,187 @@ +/* Obtain a series of random bytes. + + Copyright 2020 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Paul Eggert. */ + +#include <config.h> + +#include <sys/random.h> + +#include <errno.h> +#include <fcntl.h> +#include <stdbool.h> +#include <unistd.h> + +#if defined _WIN32 && ! defined __CYGWIN__ +# define WIN32_LEAN_AND_MEAN +# include <windows.h> +# if HAVE_BCRYPT_H +# include <bcrypt.h> +# else +# define NTSTATUS LONG +typedef void * BCRYPT_ALG_HANDLE; +# define BCRYPT_USE_SYSTEM_PREFERRED_RNG 0x00000002 +# if HAVE_LIB_BCRYPT +extern NTSTATUS WINAPI BCryptGenRandom (BCRYPT_ALG_HANDLE, UCHAR *, ULONG, ULONG); +# endif +# endif +# if !HAVE_LIB_BCRYPT +# include <wincrypt.h> +# ifndef CRYPT_VERIFY_CONTEXT +# define CRYPT_VERIFY_CONTEXT 0xF0000000 +# endif +# endif +#endif + +#include "minmax.h" + +#if defined _WIN32 && ! defined __CYGWIN__ + +/* Don't assume that UNICODE is not defined. */ +# undef LoadLibrary +# define LoadLibrary LoadLibraryA +# undef CryptAcquireContext +# define CryptAcquireContext CryptAcquireContextA + +# if !HAVE_LIB_BCRYPT + +/* Avoid warnings from gcc -Wcast-function-type. */ +# define GetProcAddress \ + (void *) GetProcAddress + +/* BCryptGenRandom with the BCRYPT_USE_SYSTEM_PREFERRED_RNG flag works only + starting with Windows 7. */ +typedef NTSTATUS (WINAPI * BCryptGenRandomFuncType) (BCRYPT_ALG_HANDLE, UCHAR *, ULONG, ULONG); +static BCryptGenRandomFuncType BCryptGenRandomFunc = NULL; +static BOOL initialized = FALSE; + +static void +initialize (void) +{ + HMODULE bcrypt = LoadLibrary ("bcrypt.dll"); + if (bcrypt != NULL) + { + BCryptGenRandomFunc = + (BCryptGenRandomFuncType) GetProcAddress (bcrypt, "BCryptGenRandom"); + } + initialized = TRUE; +} + +# else + +# define BCryptGenRandomFunc BCryptGenRandom + +# endif + +#else +/* These devices exist on all platforms except native Windows. */ + +/* Name of a device through which the kernel returns high quality random + numbers, from an entropy pool. When the pool is empty, the call blocks + until entropy sources have added enough bits of entropy. */ +# ifndef NAME_OF_RANDOM_DEVICE +# define NAME_OF_RANDOM_DEVICE "/dev/random" +# endif + +/* Name of a device through which the kernel returns random or pseudo-random + numbers. It uses an entropy pool, but, in order to avoid blocking, adds + bits generated by a pseudo-random number generator, as needed. */ +# ifndef NAME_OF_NONCE_DEVICE +# define NAME_OF_NONCE_DEVICE "/dev/urandom" +# endif + +#endif + +/* Set BUFFER (of size LENGTH) to random bytes under the control of FLAGS. + Return the number of bytes written (> 0). + Upon error, return -1 and set errno. */ +ssize_t +getrandom (void *buffer, size_t length, unsigned int flags) +#undef getrandom +{ +#if defined _WIN32 && ! defined __CYGWIN__ + /* BCryptGenRandom, defined in <bcrypt.h> + <https://docs.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom> + with the BCRYPT_USE_SYSTEM_PREFERRED_RNG flag + works in Windows 7 and newer. */ + static int bcrypt_not_working /* = 0 */; + if (!bcrypt_not_working) + { +# if !HAVE_LIB_BCRYPT + if (!initialized) + initialize (); +# endif + if (BCryptGenRandomFunc != NULL + && BCryptGenRandomFunc (NULL, buffer, length, + BCRYPT_USE_SYSTEM_PREFERRED_RNG) + == 0 /*STATUS_SUCCESS*/) + return length; + bcrypt_not_working = 1; + } +# if !HAVE_LIB_BCRYPT + /* CryptGenRandom, defined in <wincrypt.h> + <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-cryptgenrandom> + works in older releases as well, but is now deprecated. + CryptAcquireContext, defined in <wincrypt.h> + <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-cryptacquirecontexta> */ + { + static int crypt_initialized /* = 0 */; + static HCRYPTPROV provider; + if (!crypt_initialized) + { + if (CryptAcquireContext (&provider, NULL, NULL, PROV_RSA_FULL, + CRYPT_VERIFY_CONTEXT)) + crypt_initialized = 1; + else + crypt_initialized = -1; + } + if (crypt_initialized >= 0) + { + if (!CryptGenRandom (provider, length, buffer)) + { + errno = EIO; + return -1; + } + return length; + } + } +# endif + errno = ENOSYS; + return -1; +#elif HAVE_GETRANDOM + return getrandom (buffer, length, flags); +#else + static int randfd[2] = { -1, -1 }; + bool devrandom = (flags & GRND_RANDOM) != 0; + int fd = randfd[devrandom]; + + if (fd < 0) + { + static char const randdevice[][MAX (sizeof NAME_OF_NONCE_DEVICE, + sizeof NAME_OF_RANDOM_DEVICE)] + = { NAME_OF_NONCE_DEVICE, NAME_OF_RANDOM_DEVICE }; + int oflags = (O_RDONLY + O_CLOEXEC + + (flags & GRND_NONBLOCK ? O_NONBLOCK : 0)); + fd = open (randdevice[devrandom], oflags); + if (fd < 0) + return fd; + randfd[devrandom] = fd; + } + + return read (fd, buffer, length); +#endif +} |