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