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Diffstat (limited to 'third_party/bearssl/src/sysrng.c')
| -rw-r--r-- | third_party/bearssl/src/sysrng.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/third_party/bearssl/src/sysrng.c b/third_party/bearssl/src/sysrng.c new file mode 100644 index 0000000..5a92114 --- /dev/null +++ b/third_party/bearssl/src/sysrng.c @@ -0,0 +1,252 @@ +/* + * Copyright (c) 2017 Thomas Pornin <[email protected]> + * + * Permission is hereby granted, free of charge, to any person obtaining + * a copy of this software and associated documentation files (the + * "Software"), to deal in the Software without restriction, including + * without limitation the rights to use, copy, modify, merge, publish, + * distribute, sublicense, and/or sell copies of the Software, and to + * permit persons to whom the Software is furnished to do so, subject to + * the following conditions: + * + * The above copyright notice and this permission notice shall be + * included in all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +#define BR_ENABLE_INTRINSICS 1 +#include "inner.h" + +#if BR_USE_GETENTROPY +#include <unistd.h> +#endif + +#if BR_USE_URANDOM +#include <sys/types.h> +#include <unistd.h> +#include <fcntl.h> +#include <errno.h> +#endif + +#if BR_USE_WIN32_RAND +#include <windows.h> +#include <wincrypt.h> +#pragma comment(lib, "advapi32") +#endif + +/* + * Seeder that uses the RDRAND opcodes (on x86 CPU). + */ +#if BR_RDRAND +BR_TARGETS_X86_UP +BR_TARGET("rdrnd") +static int +seeder_rdrand(const br_prng_class **ctx) +{ + unsigned char tmp[32]; + size_t u; + + for (u = 0; u < sizeof tmp; u += sizeof(uint32_t)) { + int j; + uint32_t x; + + /* + * We use the 32-bit intrinsic so that code is compatible + * with both 32-bit and 64-bit architectures. + * + * Intel recommends trying at least 10 times in case of + * failure. + * + * AMD bug: there are reports that some AMD processors + * have a bug that makes them fail silently after a + * suspend/resume cycle, in which case RDRAND will report + * a success but always return 0xFFFFFFFF. + * see: https://bugzilla.kernel.org/show_bug.cgi?id=85911 + * + * As a mitigation, if the 32-bit value is 0 or -1, then + * it is considered a failure and tried again. This should + * reliably detect the buggy case, at least. This also + * implies that the selected seed values can never be + * 0x00000000 or 0xFFFFFFFF, which is not a problem since + * we are generating a seed for a PRNG, and we overdo it + * a bit (we generate 32 bytes of randomness, and 256 bits + * of entropy are really overkill). + */ + for (j = 0; j < 10; j ++) { + if (_rdrand32_step(&x) && x != 0 && x != (uint32_t)-1) { + goto next_word; + } + } + return 0; + next_word: + br_enc32le(tmp + u, x); + } + (*ctx)->update(ctx, tmp, sizeof tmp); + return 1; +} +BR_TARGETS_X86_DOWN + +static int +rdrand_supported(void) +{ + /* + * The RDRND support is bit 30 of ECX, as returned by CPUID. + */ + return br_cpuid(0, 0, 0x40000000, 0); +} +#endif + +/* + * Seeder that uses /dev/urandom (on Unix-like systems). + */ +#if BR_USE_URANDOM +static int +seeder_urandom(const br_prng_class **ctx) +{ + int f; + + f = open("/dev/urandom", O_RDONLY); + if (f >= 0) { + unsigned char tmp[32]; + size_t u; + + for (u = 0; u < sizeof tmp;) { + ssize_t len; + + len = read(f, tmp + u, (sizeof tmp) - u); + if (len < 0) { + if (errno == EINTR) { + continue; + } + break; + } + u += (size_t)len; + } + close(f); + if (u == sizeof tmp) { + (*ctx)->update(ctx, tmp, sizeof tmp); + return 1; + } + } + return 0; +} +#endif + +/* + * Seeder that uses getentropy() (backed by getrandom() on some systems, + * e.g. Linux). On failure, it will use the /dev/urandom seeder (if + * enabled). + */ +#if BR_USE_GETENTROPY +static int +seeder_getentropy(const br_prng_class **ctx) +{ + unsigned char tmp[32]; + + if (getentropy(tmp, sizeof tmp) == 0) { + (*ctx)->update(ctx, tmp, sizeof tmp); + return 1; + } +#if BR_USE_URANDOM + return seeder_urandom(ctx); +#else + return 0; +#endif +} +#endif + +/* + * Seeder that uses CryptGenRandom() (on Windows). + */ +#if BR_USE_WIN32_RAND +static int +seeder_win32(const br_prng_class **ctx) +{ + HCRYPTPROV hp; + + if (CryptAcquireContext(&hp, 0, 0, PROV_RSA_FULL, + CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) + { + BYTE buf[32]; + BOOL r; + + r = CryptGenRandom(hp, sizeof buf, buf); + CryptReleaseContext(hp, 0); + if (r) { + (*ctx)->update(ctx, buf, sizeof buf); + return 1; + } + } + return 0; +} +#endif + +/* + * An aggregate seeder that uses RDRAND, and falls back to an OS-provided + * source if RDRAND fails. + */ +#if BR_RDRAND && (BR_USE_GETENTROPY || BR_USE_URANDOM || BR_USE_WIN32_RAND) +static int +seeder_rdrand_with_fallback(const br_prng_class **ctx) +{ + if (!seeder_rdrand(ctx)) { +#if BR_USE_GETENTROPY + return seeder_getentropy(ctx); +#elif BR_USE_URANDOM + return seeder_urandom(ctx); +#elif BR_USE_WIN32_RAND + return seeder_win32(ctx); +#else +#error "macro selection has gone wrong" +#endif + } + return 1; +} +#endif + +/* see bearssl_rand.h */ +br_prng_seeder +br_prng_seeder_system(const char **name) +{ +#if BR_RDRAND + if (rdrand_supported()) { + if (name != NULL) { + *name = "rdrand"; + } +#if BR_USE_GETENTROPY || BR_USE_URANDOM || BR_USE_WIN32_RAND + return &seeder_rdrand_with_fallback; +#else + return &seeder_rdrand; +#endif + } +#endif +#if BR_USE_GETENTROPY + if (name != NULL) { + *name = "getentropy"; + } + return &seeder_getentropy; +#elif BR_USE_URANDOM + if (name != NULL) { + *name = "urandom"; + } + return &seeder_urandom; +#elif BR_USE_WIN32_RAND + if (name != NULL) { + *name = "win32"; + } + return &seeder_win32; +#else + if (name != NULL) { + *name = "none"; + } + return 0; +#endif +} |