/* Copyright (c) 2017, Google Inc. * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #include "internal.h" #include "../cipher/internal.h" /* Section references in this file refer to SP 800-90Ar1: * http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf */ /* See table 3. */ static const uint64_t kMaxReseedCount = UINT64_C(1) << 48; int CTR_DRBG_init(CTR_DRBG_STATE *drbg, const uint8_t entropy[CTR_DRBG_ENTROPY_LEN], const uint8_t *personalization, size_t personalization_len) { /* Section 10.2.1.3.1 */ if (personalization_len > CTR_DRBG_ENTROPY_LEN) { return 0; } uint8_t seed_material[CTR_DRBG_ENTROPY_LEN]; OPENSSL_memcpy(seed_material, entropy, CTR_DRBG_ENTROPY_LEN); for (size_t i = 0; i < personalization_len; i++) { seed_material[i] ^= personalization[i]; } /* Section 10.2.1.2 */ /* kInitMask is the result of encrypting blocks with big-endian value 1, 2 * and 3 with the all-zero AES-256 key. */ static const uint8_t kInitMask[CTR_DRBG_ENTROPY_LEN] = { 0x53, 0x0f, 0x8a, 0xfb, 0xc7, 0x45, 0x36, 0xb9, 0xa9, 0x63, 0xb4, 0xf1, 0xc4, 0xcb, 0x73, 0x8b, 0xce, 0xa7, 0x40, 0x3d, 0x4d, 0x60, 0x6b, 0x6e, 0x07, 0x4e, 0xc5, 0xd3, 0xba, 0xf3, 0x9d, 0x18, 0x72, 0x60, 0x03, 0xca, 0x37, 0xa6, 0x2a, 0x74, 0xd1, 0xa2, 0xf5, 0x8e, 0x75, 0x06, 0x35, 0x8e, }; for (size_t i = 0; i < sizeof(kInitMask); i++) { seed_material[i] ^= kInitMask[i]; } drbg->ctr = aes_ctr_set_key(&drbg->ks, NULL, &drbg->block, seed_material, 32); OPENSSL_memcpy(drbg->counter.bytes, seed_material + 32, 16); drbg->reseed_counter = 1; return 1; } OPENSSL_COMPILE_ASSERT(CTR_DRBG_ENTROPY_LEN % AES_BLOCK_SIZE == 0, not_a_multiple_of_block_size); /* ctr_inc adds |n| to the last four bytes of |drbg->counter|, treated as a * big-endian number. */ static void ctr32_add(CTR_DRBG_STATE *drbg, uint32_t n) { drbg->counter.words[3] = CRYPTO_bswap4(CRYPTO_bswap4(drbg->counter.words[3]) + n); } static int CTR_DRBG_update(CTR_DRBG_STATE *drbg, const uint8_t *data, size_t data_len) { /* Section 10.2.1.2. A value of |data_len| which less than * |CTR_DRBG_ENTROPY_LEN| is permitted and acts the same as right-padding * with zeros. This can save a copy. */ if (data_len > CTR_DRBG_ENTROPY_LEN) { return 0; } uint8_t temp[CTR_DRBG_ENTROPY_LEN]; for (size_t i = 0; i < CTR_DRBG_ENTROPY_LEN; i += AES_BLOCK_SIZE) { ctr32_add(drbg, 1); drbg->block(drbg->counter.bytes, temp + i, &drbg->ks); } for (size_t i = 0; i < data_len; i++) { temp[i] ^= data[i]; } drbg->ctr = aes_ctr_set_key(&drbg->ks, NULL, &drbg->block, temp, 32); OPENSSL_memcpy(drbg->counter.bytes, temp + 32, 16); return 1; } int CTR_DRBG_reseed(CTR_DRBG_STATE *drbg, const uint8_t entropy[CTR_DRBG_ENTROPY_LEN], const uint8_t *additional_data, size_t additional_data_len) { /* Section 10.2.1.4 */ uint8_t entropy_copy[CTR_DRBG_ENTROPY_LEN]; if (additional_data_len > 0) { if (additional_data_len > CTR_DRBG_ENTROPY_LEN) { return 0; } OPENSSL_memcpy(entropy_copy, entropy, CTR_DRBG_ENTROPY_LEN); for (size_t i = 0; i < additional_data_len; i++) { entropy_copy[i] ^= additional_data[i]; } entropy = entropy_copy; } if (!CTR_DRBG_update(drbg, entropy, CTR_DRBG_ENTROPY_LEN)) { return 0; } drbg->reseed_counter = 1; return 1; } int CTR_DRBG_generate(CTR_DRBG_STATE *drbg, uint8_t *out, size_t out_len, const uint8_t *additional_data, size_t additional_data_len) { /* See 9.3.1 */ if (out_len > CTR_DRBG_MAX_GENERATE_LENGTH) { return 0; } /* See 10.2.1.5.1 */ if (drbg->reseed_counter > kMaxReseedCount) { return 0; } if (additional_data_len != 0 && !CTR_DRBG_update(drbg, additional_data, additional_data_len)) { return 0; } /* kChunkSize is used to interact better with the cache. Since the AES-CTR * code assumes that it's encrypting rather than just writing keystream, the * buffer has to be zeroed first. Without chunking, large reads would zero * the whole buffer, flushing the L1 cache, and then do another pass (missing * the cache every time) to “encrypt” it. The code can avoid this by * chunking. */ static const size_t kChunkSize = 8 * 1024; while (out_len >= AES_BLOCK_SIZE) { size_t todo = kChunkSize; if (todo > out_len) { todo = out_len; } todo &= ~(AES_BLOCK_SIZE-1); const size_t num_blocks = todo / AES_BLOCK_SIZE; if (drbg->ctr) { OPENSSL_memset(out, 0, todo); ctr32_add(drbg, 1); drbg->ctr(out, out, num_blocks, &drbg->ks, drbg->counter.bytes); ctr32_add(drbg, num_blocks - 1); } else { for (size_t i = 0; i < todo; i += AES_BLOCK_SIZE) { ctr32_add(drbg, 1); drbg->block(drbg->counter.bytes, out + i, &drbg->ks); } } out += todo; out_len -= todo; } if (out_len > 0) { uint8_t block[AES_BLOCK_SIZE]; ctr32_add(drbg, 1); drbg->block(drbg->counter.bytes, block, &drbg->ks); OPENSSL_memcpy(out, block, out_len); } if (!CTR_DRBG_update(drbg, additional_data, additional_data_len)) { return 0; } drbg->reseed_counter++; return 1; } void CTR_DRBG_clear(CTR_DRBG_STATE *drbg) { OPENSSL_cleanse(drbg, sizeof(CTR_DRBG_STATE)); }