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, aead_chacha20_poly1305_open, 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, aead_chacha20_poly1305_open, CIPHER_R_TOO_LARGE);
return 0;
}
if (nonce_len != CHACHA20_NONCE_LEN) {
OPENSSL_PUT_ERROR(CIPHER, aead_chacha20_poly1305_open, 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, aead_chacha20_poly1305_open,
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, aead_chacha20_poly1305_open, CIPHER_R_BAD_DECRYPT);
return 0;
}
CRYPTO_chacha_20(out, in, plaintext_len, c20_ctx->key, nonce, 1);
*out_len = plaintext_len;
return 1;
}
// calc_tag fills |tag| with the authentication tag for the given inputs.
static void calc_tag(uint8_t tag[POLY1305_TAG_LEN], const uint8_t *key,
const uint8_t nonce[12], const uint8_t *ad, size_t ad_len,
const uint8_t *ciphertext, size_t ciphertext_len,
const uint8_t *ciphertext_extra,
size_t ciphertext_extra_len) {
alignas(16) uint8_t poly1305_key[32];
OPENSSL_memset(poly1305_key, 0, sizeof(poly1305_key));
CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key), key, nonce,
0);
static const uint8_t padding[16] = { 0 }; // Padding is all zeros.
poly1305_state ctx;
CRYPTO_poly1305_init(&ctx, poly1305_key);
CRYPTO_poly1305_update(&ctx, ad, ad_len);
if (ad_len % 16 != 0) {
CRYPTO_poly1305_update(&ctx, padding, sizeof(padding) - (ad_len % 16));
}
CRYPTO_poly1305_update(&ctx, ciphertext, ciphertext_len);
CRYPTO_poly1305_update(&ctx, ciphertext_extra, ciphertext_extra_len);
const size_t ciphertext_total = ciphertext_len + ciphertext_extra_len;
if (ciphertext_total % 16 != 0) {
CRYPTO_poly1305_update(&ctx, padding,
sizeof(padding) - (ciphertext_total % 16));
}
poly1305_update_length(&ctx, ad_len);
poly1305_update_length(&ctx, ciphertext_total);
CRYPTO_poly1305_finish(&ctx, tag);
}
static ssize_t aead_chacha20_poly1305_seal(const EVP_AEAD_CTX *ctx,
unsigned char *out, size_t max_out_len,
const unsigned char *nonce, size_t nonce_len,
const unsigned char *in, size_t in_len,
const unsigned char *ad, size_t ad_len)
{
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
unsigned char 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 2TB 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)
{
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_SEAL, EVP_R_TOO_LARGE);
return -1;
}
if (max_out_len < in_len + c20_ctx->tag_len)
{
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_SEAL, EVP_R_BUFFER_TOO_SMALL);
return -1;
}
if (nonce_len != CHACHA20_NONCE_LEN)
{
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_SEAL, EVP_R_IV_TOO_LARGE);
return -1;
}
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);
if (c20_ctx->tag_len != POLY1305_TAG_LEN)
{
unsigned char tag[POLY1305_TAG_LEN];
CRYPTO_poly1305_finish(&poly1305, tag);
memcpy(out + in_len, tag, c20_ctx->tag_len);
return in_len + c20_ctx->tag_len;
}
CRYPTO_poly1305_finish(&poly1305, out + in_len);
return in_len + POLY1305_TAG_LEN;
}
/* aead_poly1305 fills |tag| with the authentication tag for the given
* inputs, using |update| to control the order and format that the inputs are
* signed/authenticated. */
static void aead_poly1305(aead_poly1305_update update,
uint8_t tag[POLY1305_TAG_LEN],
const struct aead_chacha20_poly1305_ctx *c20_ctx,
const uint8_t nonce[12], const uint8_t *ad,
size_t ad_len, const uint8_t *ciphertext,
size_t ciphertext_len) {
uint8_t poly1305_key[32] ALIGNED;
memset(poly1305_key, 0, sizeof(poly1305_key));
CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key),
c20_ctx->key, nonce, 0);
poly1305_state ctx;
CRYPTO_poly1305_init(&ctx, poly1305_key);
update(&ctx, ad, ad_len, ciphertext, ciphertext_len);
CRYPTO_poly1305_finish(&ctx, tag);
}
static int
aead_chacha20_poly1305_open(const EVP_AEAD_CTX *ctx, unsigned char *out,
size_t *out_len, size_t max_out_len, const unsigned char *nonce,
size_t nonce_len, const unsigned char *in, size_t in_len,
const unsigned char *ad, size_t ad_len)
{
const struct aead_chacha20_poly1305_ctx *c20_ctx = ctx->aead_state;
unsigned char mac[POLY1305_TAG_LEN];
unsigned char poly1305_key[32];
const unsigned char *iv = nonce;
poly1305_state poly1305;
const uint64_t in_len_64 = in_len;
size_t plaintext_len;
uint64_t ctr = 0;
if (in_len < c20_ctx->tag_len) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_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 2TB 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) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_TOO_LARGE);
return 0;
}
if (nonce_len != ctx->aead->nonce_len) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_IV_TOO_LARGE);
return 0;
}
plaintext_len = in_len - c20_ctx->tag_len;
if (max_out_len < plaintext_len) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN,
EVP_R_BUFFER_TOO_SMALL);
return 0;
}
if (nonce_len == CHACHA20_NONCE_LEN_OLD) {
/* Google's draft-agl-tls-chacha20poly1305-04, Nov 2013 */
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);
} else if (nonce_len == CHACHA20_NONCE_LEN) {
/* RFC 7539, May 2015 */
ctr = (uint64_t)(nonce[0] | nonce[1] << 8 |
nonce[2] << 16 | nonce[3] << 24) << 32;
iv = nonce + CHACHA20_CONSTANT_LEN;
memset(poly1305_key, 0, sizeof(poly1305_key));
CRYPTO_chacha_20(poly1305_key, poly1305_key,
sizeof(poly1305_key), c20_ctx->key, iv, ctr);
CRYPTO_poly1305_init(&poly1305, poly1305_key);
poly1305_update_with_pad16(&poly1305, ad, ad_len);
poly1305_update_with_pad16(&poly1305, in, plaintext_len);
poly1305_update_with_length(&poly1305, NULL, ad_len);
poly1305_update_with_length(&poly1305, NULL, plaintext_len);
}
CRYPTO_poly1305_finish(&poly1305, mac);
if (timingsafe_memcmp(mac, in + plaintext_len, c20_ctx->tag_len) != 0) {
EVPerr(EVP_F_AEAD_CHACHA20_POLY1305_OPEN, EVP_R_BAD_DECRYPT);
return 0;
}
CRYPTO_chacha_20(out, in, plaintext_len, c20_ctx->key, iv, ctr + 1);
*out_len = plaintext_len;
return 1;
}
