324 lines
10 KiB
C
324 lines
10 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/aead.h>
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#include <openssl/cipher.h>
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#include <openssl/crypto.h>
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#include <openssl/err.h>
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#include "internal.h"
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#if !defined(OPENSSL_SMALL)
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#define EVP_AEAD_AES_GCM_SIV_NONCE_LEN 12
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#define EVP_AEAD_AES_GCM_SIV_TAG_LEN 16
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struct aead_aes_gcm_siv_ctx {
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union {
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double align;
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AES_KEY ks;
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} ks;
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block128_f kgk_block;
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unsigned is_256:1;
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};
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static int aead_aes_gcm_siv_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
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size_t key_len, size_t tag_len) {
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const size_t key_bits = key_len * 8;
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if (key_bits != 128 && key_bits != 256) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);
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return 0; /* EVP_AEAD_CTX_init should catch this. */
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}
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if (tag_len == EVP_AEAD_DEFAULT_TAG_LENGTH) {
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tag_len = EVP_AEAD_AES_GCM_SIV_TAG_LEN;
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}
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if (tag_len != EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TAG_TOO_LARGE);
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return 0;
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}
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struct aead_aes_gcm_siv_ctx *gcm_siv_ctx =
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OPENSSL_malloc(sizeof(struct aead_aes_gcm_siv_ctx));
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if (gcm_siv_ctx == NULL) {
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return 0;
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}
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OPENSSL_memset(gcm_siv_ctx, 0, sizeof(struct aead_aes_gcm_siv_ctx));
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aes_ctr_set_key(&gcm_siv_ctx->ks.ks, NULL, &gcm_siv_ctx->kgk_block, key,
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key_len);
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gcm_siv_ctx->is_256 = (key_len == 32);
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ctx->aead_state = gcm_siv_ctx;
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return 1;
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}
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static void aead_aes_gcm_siv_cleanup(EVP_AEAD_CTX *ctx) {
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struct aead_aes_gcm_siv_ctx *gcm_siv_ctx = ctx->aead_state;
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OPENSSL_cleanse(gcm_siv_ctx, sizeof(struct aead_aes_gcm_siv_ctx));
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OPENSSL_free(gcm_siv_ctx);
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}
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/* gcm_siv_crypt encrypts (or decrypts—it's the same thing) |in_len| bytes from
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* |in| to |out|, using the block function |enc_block| with |key| in counter
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* mode, starting at |initial_counter|. This differs from the traditional
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* counter mode code in that the counter is handled little-endian, only the
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* first four bytes are used and the GCM-SIV tweak to the final byte is
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* applied. The |in| and |out| pointers may be equal but otherwise must not
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* alias. */
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static void gcm_siv_crypt(uint8_t *out, const uint8_t *in, size_t in_len,
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const uint8_t initial_counter[AES_BLOCK_SIZE],
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block128_f enc_block, const AES_KEY *key) {
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union {
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uint32_t w[4];
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uint8_t c[16];
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} counter;
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OPENSSL_memcpy(counter.c, initial_counter, AES_BLOCK_SIZE);
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counter.c[15] |= 0x80;
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for (size_t done = 0; done < in_len;) {
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uint8_t keystream[AES_BLOCK_SIZE];
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enc_block(counter.c, keystream, key);
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counter.w[0]++;
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size_t todo = AES_BLOCK_SIZE;
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if (in_len - done < todo) {
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todo = in_len - done;
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}
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for (size_t i = 0; i < todo; i++) {
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out[done + i] = keystream[i] ^ in[done + i];
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}
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done += todo;
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}
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}
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/* gcm_siv_polyval evaluates POLYVAL at |auth_key| on the given plaintext and
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* AD. The result is written to |out_tag|. */
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static void gcm_siv_polyval(
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uint8_t out_tag[16], const uint8_t *in, size_t in_len, const uint8_t *ad,
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size_t ad_len, const uint8_t auth_key[16],
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const uint8_t nonce[EVP_AEAD_AES_GCM_SIV_NONCE_LEN]) {
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struct polyval_ctx polyval_ctx;
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CRYPTO_POLYVAL_init(&polyval_ctx, auth_key);
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CRYPTO_POLYVAL_update_blocks(&polyval_ctx, ad, ad_len & ~15);
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uint8_t scratch[16];
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if (ad_len & 15) {
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OPENSSL_memset(scratch, 0, sizeof(scratch));
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OPENSSL_memcpy(scratch, &ad[ad_len & ~15], ad_len & 15);
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CRYPTO_POLYVAL_update_blocks(&polyval_ctx, scratch, sizeof(scratch));
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}
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CRYPTO_POLYVAL_update_blocks(&polyval_ctx, in, in_len & ~15);
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if (in_len & 15) {
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OPENSSL_memset(scratch, 0, sizeof(scratch));
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OPENSSL_memcpy(scratch, &in[in_len & ~15], in_len & 15);
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CRYPTO_POLYVAL_update_blocks(&polyval_ctx, scratch, sizeof(scratch));
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}
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union {
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uint8_t c[16];
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struct {
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uint64_t ad;
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uint64_t in;
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} bitlens;
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} length_block;
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length_block.bitlens.ad = ad_len * 8;
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length_block.bitlens.in = in_len * 8;
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CRYPTO_POLYVAL_update_blocks(&polyval_ctx, length_block.c,
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sizeof(length_block));
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CRYPTO_POLYVAL_finish(&polyval_ctx, out_tag);
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for (size_t i = 0; i < EVP_AEAD_AES_GCM_SIV_NONCE_LEN; i++) {
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out_tag[i] ^= nonce[i];
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}
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out_tag[15] &= 0x7f;
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}
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/* gcm_siv_record_keys contains the keys used for a specific GCM-SIV record. */
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struct gcm_siv_record_keys {
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uint8_t auth_key[16];
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union {
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double align;
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AES_KEY ks;
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} enc_key;
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block128_f enc_block;
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};
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/* gcm_siv_keys calculates the keys for a specific GCM-SIV record with the
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* given nonce and writes them to |*out_keys|. */
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static void gcm_siv_keys(
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const struct aead_aes_gcm_siv_ctx *gcm_siv_ctx,
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struct gcm_siv_record_keys *out_keys,
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const uint8_t nonce[EVP_AEAD_AES_GCM_SIV_NONCE_LEN]) {
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const AES_KEY *const key = &gcm_siv_ctx->ks.ks;
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uint8_t key_material[(128 /* POLYVAL key */ + 256 /* max AES key */) / 8];
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const size_t blocks_needed = gcm_siv_ctx->is_256 ? 6 : 4;
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uint8_t counter[AES_BLOCK_SIZE];
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OPENSSL_memset(counter, 0, AES_BLOCK_SIZE - EVP_AEAD_AES_GCM_SIV_NONCE_LEN);
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OPENSSL_memcpy(counter + AES_BLOCK_SIZE - EVP_AEAD_AES_GCM_SIV_NONCE_LEN,
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nonce, EVP_AEAD_AES_GCM_SIV_NONCE_LEN);
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for (size_t i = 0; i < blocks_needed; i++) {
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counter[0] = i;
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uint8_t ciphertext[AES_BLOCK_SIZE];
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gcm_siv_ctx->kgk_block(counter, ciphertext, key);
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OPENSSL_memcpy(&key_material[i * 8], ciphertext, 8);
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}
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OPENSSL_memcpy(out_keys->auth_key, key_material, 16);
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aes_ctr_set_key(&out_keys->enc_key.ks, NULL, &out_keys->enc_block,
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key_material + 16, gcm_siv_ctx->is_256 ? 32 : 16);
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}
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static int aead_aes_gcm_siv_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
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size_t *out_len, size_t max_out_len,
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const uint8_t *nonce, size_t nonce_len,
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const uint8_t *in, size_t in_len,
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const uint8_t *ad, size_t ad_len) {
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const struct aead_aes_gcm_siv_ctx *gcm_siv_ctx = ctx->aead_state;
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const uint64_t in_len_64 = in_len;
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const uint64_t ad_len_64 = ad_len;
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if (in_len + EVP_AEAD_AES_GCM_SIV_TAG_LEN < in_len ||
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in_len_64 > (UINT64_C(1) << 36) ||
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ad_len_64 >= (UINT64_C(1) << 61)) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
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return 0;
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}
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if (max_out_len < in_len + EVP_AEAD_AES_GCM_SIV_TAG_LEN) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
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return 0;
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}
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if (nonce_len != EVP_AEAD_AES_GCM_SIV_NONCE_LEN) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
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return 0;
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}
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struct gcm_siv_record_keys keys;
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gcm_siv_keys(gcm_siv_ctx, &keys, nonce);
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uint8_t tag[16];
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gcm_siv_polyval(tag, in, in_len, ad, ad_len, keys.auth_key, nonce);
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keys.enc_block(tag, tag, &keys.enc_key.ks);
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gcm_siv_crypt(out, in, in_len, tag, keys.enc_block, &keys.enc_key.ks);
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OPENSSL_memcpy(&out[in_len], tag, EVP_AEAD_AES_GCM_SIV_TAG_LEN);
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*out_len = in_len + EVP_AEAD_AES_GCM_SIV_TAG_LEN;
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return 1;
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}
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static int aead_aes_gcm_siv_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
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size_t *out_len, size_t max_out_len,
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const uint8_t *nonce, size_t nonce_len,
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const uint8_t *in, size_t in_len,
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const uint8_t *ad, size_t ad_len) {
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const uint64_t ad_len_64 = ad_len;
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if (ad_len_64 >= (UINT64_C(1) << 61)) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
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return 0;
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}
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const uint64_t in_len_64 = in_len;
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if (in_len < EVP_AEAD_AES_GCM_SIV_TAG_LEN ||
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in_len_64 > (UINT64_C(1) << 36) + AES_BLOCK_SIZE) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
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return 0;
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}
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if (nonce_len != EVP_AEAD_AES_GCM_SIV_NONCE_LEN) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
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return 0;
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}
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const struct aead_aes_gcm_siv_ctx *gcm_siv_ctx = ctx->aead_state;
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const size_t plaintext_len = in_len - EVP_AEAD_AES_GCM_SIV_TAG_LEN;
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if (max_out_len < plaintext_len) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
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return 0;
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}
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struct gcm_siv_record_keys keys;
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gcm_siv_keys(gcm_siv_ctx, &keys, nonce);
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gcm_siv_crypt(out, in, plaintext_len, &in[plaintext_len], keys.enc_block,
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&keys.enc_key.ks);
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uint8_t expected_tag[EVP_AEAD_AES_GCM_SIV_TAG_LEN];
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gcm_siv_polyval(expected_tag, out, plaintext_len, ad, ad_len, keys.auth_key,
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nonce);
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keys.enc_block(expected_tag, expected_tag, &keys.enc_key.ks);
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if (CRYPTO_memcmp(expected_tag, &in[plaintext_len], sizeof(expected_tag)) !=
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0) {
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OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
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return 0;
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}
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*out_len = plaintext_len;
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return 1;
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}
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static const EVP_AEAD aead_aes_128_gcm_siv = {
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16, /* key length */
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EVP_AEAD_AES_GCM_SIV_NONCE_LEN, /* nonce length */
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EVP_AEAD_AES_GCM_SIV_TAG_LEN, /* overhead */
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EVP_AEAD_AES_GCM_SIV_TAG_LEN, /* max tag length */
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aead_aes_gcm_siv_init,
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NULL /* init_with_direction */,
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aead_aes_gcm_siv_cleanup,
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aead_aes_gcm_siv_seal,
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aead_aes_gcm_siv_open,
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NULL /* get_iv */,
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};
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static const EVP_AEAD aead_aes_256_gcm_siv = {
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32, /* key length */
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EVP_AEAD_AES_GCM_SIV_NONCE_LEN, /* nonce length */
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EVP_AEAD_AES_GCM_SIV_TAG_LEN, /* overhead */
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EVP_AEAD_AES_GCM_SIV_TAG_LEN, /* max tag length */
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aead_aes_gcm_siv_init,
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NULL /* init_with_direction */,
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aead_aes_gcm_siv_cleanup,
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aead_aes_gcm_siv_seal,
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aead_aes_gcm_siv_open,
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NULL /* get_iv */,
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};
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const EVP_AEAD *EVP_aead_aes_128_gcm_siv(void) {
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return &aead_aes_128_gcm_siv;
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}
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const EVP_AEAD *EVP_aead_aes_256_gcm_siv(void) {
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return &aead_aes_256_gcm_siv;
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|
|
}
|
||
|
|
|
||
|
|
#endif /* !OPENSSL_SMALL */
|