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- /* Copyright (c) 2014, 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 <openssl/aead.h>
-
- #include <string.h>
-
- #include <openssl/chacha.h>
- #include <openssl/cipher.h>
- #include <openssl/err.h>
- #include <openssl/mem.h>
- #include <openssl/poly1305.h>
-
- #include "internal.h"
-
-
- #define POLY1305_TAG_LEN 16
- #define CHACHA20_NONCE_LEN 8
-
- struct aead_chacha20_poly1305_ctx {
- unsigned char key[32];
- unsigned char tag_len;
- };
-
- static int aead_chacha20_poly1305_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
- size_t key_len, size_t tag_len) {
- struct aead_chacha20_poly1305_ctx *c20_ctx;
-
- if (tag_len == 0) {
- tag_len = POLY1305_TAG_LEN;
- }
-
- if (tag_len > POLY1305_TAG_LEN) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
- return 0;
- }
-
- if (key_len != sizeof(c20_ctx->key)) {
- return 0; /* internal error - EVP_AEAD_CTX_init should catch this. */
- }
-
- c20_ctx = OPENSSL_malloc(sizeof(struct aead_chacha20_poly1305_ctx));
- if (c20_ctx == NULL) {
- return 0;
- }
-
- memcpy(c20_ctx->key, key, key_len);
- c20_ctx->tag_len = tag_len;
- ctx->aead_state = c20_ctx;
-
- return 1;
- }
-
- static void aead_chacha20_poly1305_cleanup(EVP_AEAD_CTX *ctx) {
- struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
- OPENSSL_cleanse(c20_ctx->key, sizeof(c20_ctx->key));
- OPENSSL_free(c20_ctx);
- }
-
- static void poly1305_update_with_length(poly1305_state *poly1305,
- const uint8_t *data, size_t data_len) {
- size_t j = data_len;
- uint8_t length_bytes[8];
- unsigned i;
-
- for (i = 0; i < sizeof(length_bytes); i++) {
- length_bytes[i] = j;
- j >>= 8;
- }
-
- CRYPTO_poly1305_update(poly1305, data, data_len);
- CRYPTO_poly1305_update(poly1305, length_bytes, sizeof(length_bytes));
- }
-
- #if defined(__arm__)
- #define ALIGNED __attribute__((aligned(16)))
- #else
- #define ALIGNED
- #endif
-
- static int aead_chacha20_poly1305_seal(const EVP_AEAD_CTX *ctx, uint8_t *out,
- size_t *out_len, size_t max_out_len,
- const uint8_t *nonce, size_t nonce_len,
- const uint8_t *in, size_t in_len,
- const uint8_t *ad, size_t ad_len) {
- const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
- uint8_t poly1305_key[32] ALIGNED;
- poly1305_state poly1305;
- const uint64_t in_len_64 = in_len;
-
- /* The underlying ChaCha implementation may not overflow the block
- * counter into the second counter word. Therefore we disallow
- * individual operations that work on more than 256GB at a time.
- * |in_len_64| is needed because, on 32-bit platforms, size_t is only
- * 32-bits and this produces a warning because it's always false.
- * Casting to uint64_t inside the conditional is not sufficient to stop
- * the warning. */
- if (in_len_64 >= (1ull << 32) * 64 - 64) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
- return 0;
- }
-
- if (in_len + c20_ctx->tag_len < in_len) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
- return 0;
- }
-
- if (max_out_len < in_len + c20_ctx->tag_len) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
- return 0;
- }
-
- if (nonce_len != CHACHA20_NONCE_LEN) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_IV_TOO_LARGE);
- return 0;
- }
-
- memset(poly1305_key, 0, sizeof(poly1305_key));
- CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
- c20_ctx->key, nonce, 0);
-
- CRYPTO_poly1305_init(&poly1305, poly1305_key);
- poly1305_update_with_length(&poly1305, ad, ad_len);
- CRYPTO_chacha_20(out, in, in_len, c20_ctx->key, nonce, 1);
- poly1305_update_with_length(&poly1305, out, in_len);
-
- uint8_t tag[POLY1305_TAG_LEN] ALIGNED;
- CRYPTO_poly1305_finish(&poly1305, tag);
- memcpy(out + in_len, tag, c20_ctx->tag_len);
- *out_len = in_len + c20_ctx->tag_len;
- return 1;
- }
-
- static int aead_chacha20_poly1305_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
- size_t *out_len, size_t max_out_len,
- const uint8_t *nonce, size_t nonce_len,
- const uint8_t *in, size_t in_len,
- const uint8_t *ad, size_t ad_len) {
- const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
- uint8_t mac[POLY1305_TAG_LEN];
- uint8_t poly1305_key[32] ALIGNED;
- size_t plaintext_len;
- poly1305_state poly1305;
- const uint64_t in_len_64 = in_len;
-
- if (in_len < c20_ctx->tag_len) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
- return 0;
- }
-
- /* The underlying ChaCha implementation may not overflow the block
- * counter into the second counter word. Therefore we disallow
- * individual operations that work on more than 256GB at a time.
- * |in_len_64| is needed because, on 32-bit platforms, size_t is only
- * 32-bits and this produces a warning because it's always false.
- * Casting to uint64_t inside the conditional is not sufficient to stop
- * the warning. */
- if (in_len_64 >= (1ull << 32) * 64 - 64) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
- return 0;
- }
-
- if (nonce_len != CHACHA20_NONCE_LEN) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_IV_TOO_LARGE);
- return 0;
- }
-
- plaintext_len = in_len - c20_ctx->tag_len;
-
- if (max_out_len < plaintext_len) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
- return 0;
- }
-
- memset(poly1305_key, 0, sizeof(poly1305_key));
- CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
- c20_ctx->key, nonce, 0);
-
- CRYPTO_poly1305_init(&poly1305, poly1305_key);
- poly1305_update_with_length(&poly1305, ad, ad_len);
- poly1305_update_with_length(&poly1305, in, plaintext_len);
- CRYPTO_poly1305_finish(&poly1305, mac);
-
- if (CRYPTO_memcmp(mac, in + plaintext_len, c20_ctx->tag_len) != 0) {
- OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
- return 0;
- }
-
- CRYPTO_chacha_20(out, in, plaintext_len, c20_ctx->key, nonce, 1);
- *out_len = plaintext_len;
- return 1;
- }
-
- static const EVP_AEAD aead_chacha20_poly1305 = {
- 32, /* key len */
- CHACHA20_NONCE_LEN, /* nonce len */
- POLY1305_TAG_LEN, /* overhead */
- POLY1305_TAG_LEN, /* max tag length */
- aead_chacha20_poly1305_init,
- NULL, /* init_with_direction */
- aead_chacha20_poly1305_cleanup,
- aead_chacha20_poly1305_seal,
- aead_chacha20_poly1305_open,
- NULL, /* get_rc4_state */
- };
-
- const EVP_AEAD *EVP_aead_chacha20_poly1305(void) {
- return &aead_chacha20_poly1305;
- }
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