/* How much overhead does the IV, MAC, TAG and padding bytes introduce ? */
static uint16_t overhead(struct s2n_connection *conn)
{
struct s2n_crypto_parameters *active = conn->server;
if (conn->mode == S2N_CLIENT) {
active = conn->client;
}
uint8_t extra;
GUARD(s2n_hmac_digest_size(active->cipher_suite->record_alg->hmac_alg, &extra));
if (active->cipher_suite->record_alg->cipher->type == S2N_CBC) {
/* Subtract one for the padding length byte */
extra += 1;
if (conn->actual_protocol_version > S2N_TLS10) {
extra += active->cipher_suite->record_alg->cipher->io.cbc.record_iv_size;
}
} else if (active->cipher_suite->record_alg->cipher->type == S2N_AEAD) {
extra += active->cipher_suite->record_alg->cipher->io.aead.tag_size;
extra += active->cipher_suite->record_alg->cipher->io.aead.record_iv_size;
} else if (active->cipher_suite->record_alg->cipher->type == S2N_COMPOSITE && conn->actual_protocol_version > S2N_TLS10) {
extra += active->cipher_suite->record_alg->cipher->io.comp.record_iv_size;
}
return extra;
}
static int s2n_p_hash(struct s2n_prf_working_space *ws, s2n_hmac_algorithm alg, struct s2n_blob *secret, struct s2n_blob *label,
struct s2n_blob *seed_a, struct s2n_blob *seed_b, struct s2n_blob *seed_c, struct s2n_blob *out)
{
uint8_t digest_size;
GUARD(s2n_hmac_digest_size(alg, &digest_size));
const struct s2n_p_hash_hmac *hmac = ws->tls.p_hash_hmac_impl;
/* First compute hmac(secret + A(0)) */
GUARD(hmac->init(ws, alg, secret));
GUARD(hmac->update(ws, label->data, label->size));
GUARD(hmac->update(ws, seed_a->data, seed_a->size));
if (seed_b) {
GUARD(hmac->update(ws, seed_b->data, seed_b->size));
if (seed_c) {
GUARD(hmac->update(ws, seed_c->data, seed_c->size));
}
}
GUARD(hmac->final(ws, ws->tls.digest0, digest_size));
uint32_t outputlen = out->size;
uint8_t *output = out->data;
while (outputlen) {
/* Now compute hmac(secret + A(N - 1) + seed) */
GUARD(hmac->reset(ws));
GUARD(hmac->update(ws, ws->tls.digest0, digest_size));
/* Add the label + seed and compute this round's A */
GUARD(hmac->update(ws, label->data, label->size));
GUARD(hmac->update(ws, seed_a->data, seed_a->size));
if (seed_b) {
GUARD(hmac->update(ws, seed_b->data, seed_b->size));
if (seed_c) {
GUARD(hmac->update(ws, seed_c->data, seed_c->size));
}
}
GUARD(hmac->final(ws, ws->tls.digest1, digest_size));
uint32_t bytes_to_xor = MIN(outputlen, digest_size);
for (int i = 0; i < bytes_to_xor; i++) {
*output ^= ws->tls.digest1[i];
output++;
outputlen--;
}
/* Stash a digest of A(N), in A(N), for the next round */
GUARD(hmac->reset(ws));
GUARD(hmac->update(ws, ws->tls.digest0, digest_size));
GUARD(hmac->final(ws, ws->tls.digest0, digest_size));
}
GUARD(hmac->cleanup(ws));
return 0;
}
/* A TLS CBC record looks like ..
*
* [ Payload data ] [ HMAC ] [ Padding ] [ Padding length byte ]
*
* Each byte in the padding is expected to be set to the same value
* as the padding length byte. So if the padding length byte is '2'
* then the padding will be [ '2', '2' ] (there'll be three bytes
* set to that value if you include the padding length byte).
*
* The goal of s2n_verify_cbc() is to verify that the padding and hmac
* are correct, without leaking (via timing) how much padding there
* actually is: as this is considered secret.
*
* In addition to our efforts here though, s2n also wraps any CBC
* verification error (or record parsing error in general) with
* a randomized delay of between 1ms and 10 seconds. See s2n_connection.c.
* This amount of delay randomization is sufficient to increase the
* complexity of attack for even a 1 microsecond timing leak (which
* is quite large) by a factor of around 83 trillion.
*/
int s2n_verify_cbc(struct s2n_connection *conn, struct s2n_hmac_state *hmac, struct s2n_blob *decrypted)
{
struct s2n_hmac_state copy;
int mac_digest_size = s2n_hmac_digest_size(hmac->alg);
/* The record has to be at least big enough to contain the MAC,
* plus the padding length byte */
gt_check(decrypted->size, mac_digest_size);
int payload_and_padding_size = decrypted->size - mac_digest_size;
/* Determine what the padding length is */
uint8_t padding_length = decrypted->data[decrypted->size - 1];
int payload_length = MAX(payload_and_padding_size - padding_length - 1, 0);
/* Update the MAC */
GUARD(s2n_hmac_update(hmac, decrypted->data, payload_length));
GUARD(s2n_hmac_copy(©, hmac));
/* Check the MAC */
uint8_t check_digest[S2N_MAX_DIGEST_LEN];
lte_check(mac_digest_size, sizeof(check_digest));
GUARD(s2n_hmac_digest_two_compression_rounds(hmac, check_digest, mac_digest_size));
int mismatches = s2n_constant_time_equals(decrypted->data + payload_length, check_digest, mac_digest_size) ^ 1;
/* Compute a MAC on the rest of the data so that we perform the same number of hash operations */
GUARD(s2n_hmac_update(©, decrypted->data + payload_length + mac_digest_size, decrypted->size - payload_length - mac_digest_size - 1));
/* SSLv3 doesn't specify what the padding should actually be */
if (conn->actual_protocol_version == S2N_SSLv3) {
return 0 - mismatches;
}
/* Check the maximum amount that could theoritically be padding */
int check = MIN(255, (payload_and_padding_size - 1));
int cutoff = check - padding_length;
for (int i = 0, j = decrypted->size - 1 - check; i < check && j < decrypted->size; i++, j++) {
uint8_t mask = ~(0xff << ((i >= cutoff) * 8));
mismatches |= (decrypted->data[j] ^ padding_length) & mask;
}
if (mismatches) {
S2N_ERROR(S2N_ERR_CBC_VERIFY);
}
return 0;
}
static int s2n_p_hash(union s2n_prf_working_space *ws, s2n_hmac_algorithm alg, struct s2n_blob *secret,
struct s2n_blob *label, struct s2n_blob *seed_a, struct s2n_blob *seed_b, struct s2n_blob *out)
{
struct s2n_hmac_state *hmac = &ws->tls.hmac;
uint32_t digest_size = s2n_hmac_digest_size(alg);
/* First compute hmac(secret + A(0)) */
GUARD(s2n_hmac_init(hmac, alg, secret->data, secret->size));
GUARD(s2n_hmac_update(hmac, label->data, label->size));
GUARD(s2n_hmac_update(hmac, seed_a->data, seed_a->size));
if (seed_b) {
GUARD(s2n_hmac_update(hmac, seed_b->data, seed_b->size));
}
GUARD(s2n_hmac_digest(hmac, ws->tls.digest0, digest_size));
uint32_t outputlen = out->size;
uint8_t *output = out->data;
while (outputlen) {
/* Now compute hmac(secret + A(N - 1) + seed) */
GUARD(s2n_hmac_reset(hmac));
GUARD(s2n_hmac_update(hmac, ws->tls.digest0, digest_size));
/* Add the label + seed and compute this round's A */
GUARD(s2n_hmac_update(hmac, label->data, label->size));
GUARD(s2n_hmac_update(hmac, seed_a->data, seed_a->size));
if (seed_b) {
GUARD(s2n_hmac_update(hmac, seed_b->data, seed_b->size));
}
GUARD(s2n_hmac_digest(hmac, ws->tls.digest1, digest_size));
uint32_t bytes_to_xor = MIN(outputlen, digest_size);
for (int i = 0; i < bytes_to_xor; i++) {
*output ^= ws->tls.digest1[i];
output++;
outputlen--;
}
/* Stash a digest of A(N), in A(N), for the next round */
GUARD(s2n_hmac_reset(hmac));
GUARD(s2n_hmac_update(hmac, ws->tls.digest0, digest_size));
GUARD(s2n_hmac_digest(hmac, ws->tls.digest0, digest_size));
}
return 0;
}
int s2n_record_write(struct s2n_connection *conn, uint8_t content_type, struct s2n_blob *in)
{
struct s2n_blob out, iv, aad;
uint8_t padding = 0;
uint16_t block_size = 0;
uint8_t aad_gen[S2N_TLS_MAX_AAD_LEN] = { 0 };
uint8_t aad_iv[S2N_TLS_MAX_IV_LEN] = { 0 };
uint8_t *sequence_number = conn->server->server_sequence_number;
struct s2n_hmac_state *mac = &conn->server->server_record_mac;
struct s2n_session_key *session_key = &conn->server->server_key;
const struct s2n_cipher_suite *cipher_suite = conn->server->cipher_suite;
uint8_t *implicit_iv = conn->server->server_implicit_iv;
if (conn->mode == S2N_CLIENT) {
sequence_number = conn->client->client_sequence_number;
mac = &conn->client->client_record_mac;
session_key = &conn->client->client_key;
cipher_suite = conn->client->cipher_suite;
implicit_iv = conn->client->client_implicit_iv;
}
S2N_ERROR_IF(s2n_stuffer_data_available(&conn->out), S2N_ERR_BAD_MESSAGE);
uint8_t mac_digest_size;
GUARD(s2n_hmac_digest_size(mac->alg, &mac_digest_size));
/* Before we do anything, we need to figure out what the length of the
* fragment is going to be.
*/
uint16_t data_bytes_to_take = MIN(in->size, s2n_record_max_write_payload_size(conn));
uint16_t extra = overhead(conn);
/* If we have padding to worry about, figure that out too */
if (cipher_suite->record_alg->cipher->type == S2N_CBC) {
block_size = cipher_suite->record_alg->cipher->io.cbc.block_size;
if (((data_bytes_to_take + extra) % block_size)) {
padding = block_size - ((data_bytes_to_take + extra) % block_size);
}
} else if (cipher_suite->record_alg->cipher->type == S2N_COMPOSITE) {
block_size = cipher_suite->record_alg->cipher->io.comp.block_size;
}
/* Start the MAC with the sequence number */
GUARD(s2n_hmac_update(mac, sequence_number, S2N_TLS_SEQUENCE_NUM_LEN));
/* Now that we know the length, start writing the record */
GUARD(s2n_stuffer_write_uint8(&conn->out, content_type));
GUARD(s2n_record_write_protocol_version(conn));
/* First write a header that has the payload length, this is for the MAC */
GUARD(s2n_stuffer_write_uint16(&conn->out, data_bytes_to_take));
if (conn->actual_protocol_version > S2N_SSLv3) {
GUARD(s2n_hmac_update(mac, conn->out.blob.data, S2N_TLS_RECORD_HEADER_LENGTH));
} else {
/* SSLv3 doesn't include the protocol version in the MAC */
GUARD(s2n_hmac_update(mac, conn->out.blob.data, 1));
GUARD(s2n_hmac_update(mac, conn->out.blob.data + 3, 2));
}
/* Compute non-payload parts of the MAC(seq num, type, proto vers, fragment length) for composite ciphers.
* Composite "encrypt" will MAC the payload data and fill in padding.
*/
if (cipher_suite->record_alg->cipher->type == S2N_COMPOSITE) {
/* Only fragment length is needed for MAC, but the EVP ctrl function needs fragment length + eiv len. */
uint16_t payload_and_eiv_len = data_bytes_to_take;
if (conn->actual_protocol_version > S2N_TLS10) {
payload_and_eiv_len += block_size;
}
/* Outputs number of extra bytes required for MAC and padding */
int pad_and_mac_len;
GUARD(cipher_suite->record_alg->cipher->io.comp.initial_hmac(session_key, sequence_number, content_type, conn->actual_protocol_version,
payload_and_eiv_len, &pad_and_mac_len));
extra += pad_and_mac_len;
}
/* Rewrite the length to be the actual fragment length */
uint16_t actual_fragment_length = data_bytes_to_take + padding + extra;
GUARD(s2n_stuffer_wipe_n(&conn->out, 2));
GUARD(s2n_stuffer_write_uint16(&conn->out, actual_fragment_length));
/* If we're AEAD, write the sequence number as an IV, and generate the AAD */
if (cipher_suite->record_alg->cipher->type == S2N_AEAD) {
struct s2n_stuffer iv_stuffer = {{0}};
iv.data = aad_iv;
iv.size = sizeof(aad_iv);
GUARD(s2n_stuffer_init(&iv_stuffer, &iv));
if (cipher_suite->record_alg->flags & S2N_TLS12_AES_GCM_AEAD_NONCE) {
/* Partially explicit nonce. See RFC 5288 Section 3 */
GUARD(s2n_stuffer_write_bytes(&conn->out, sequence_number, S2N_TLS_SEQUENCE_NUM_LEN));
GUARD(s2n_stuffer_write_bytes(&iv_stuffer, implicit_iv, cipher_suite->record_alg->cipher->io.aead.fixed_iv_size));
GUARD(s2n_stuffer_write_bytes(&iv_stuffer, sequence_number, S2N_TLS_SEQUENCE_NUM_LEN));
} else if (cipher_suite->record_alg->flags & S2N_TLS12_CHACHA_POLY_AEAD_NONCE) {
/* Fully implicit nonce. See RFC7905 Section 2 */
uint8_t four_zeroes[4] = { 0 };
GUARD(s2n_stuffer_write_bytes(&iv_stuffer, four_zeroes, 4));
GUARD(s2n_stuffer_write_bytes(&iv_stuffer, sequence_number, S2N_TLS_SEQUENCE_NUM_LEN));
for(int i = 0; i < cipher_suite->record_alg->cipher->io.aead.fixed_iv_size; i++) {
aad_iv[i] = aad_iv[i] ^ implicit_iv[i];
}
} else {
S2N_ERROR(S2N_ERR_INVALID_NONCE_TYPE);
}
/* Set the IV size to the amount of data written */
iv.size = s2n_stuffer_data_available(&iv_stuffer);
aad.data = aad_gen;
aad.size = sizeof(aad_gen);
struct s2n_stuffer ad_stuffer = {{0}};
GUARD(s2n_stuffer_init(&ad_stuffer, &aad));
GUARD(s2n_aead_aad_init(conn, sequence_number, content_type, data_bytes_to_take, &ad_stuffer));
} else if (cipher_suite->record_alg->cipher->type == S2N_CBC || cipher_suite->record_alg->cipher->type == S2N_COMPOSITE) {
iv.size = block_size;
iv.data = implicit_iv;
/* For TLS1.1/1.2; write the IV with random data */
if (conn->actual_protocol_version > S2N_TLS10) {
GUARD(s2n_get_public_random_data(&iv));
GUARD(s2n_stuffer_write(&conn->out, &iv));
}
}
/* We are done with this sequence number, so we can increment it */
struct s2n_blob seq = {.data = sequence_number,.size = S2N_TLS_SEQUENCE_NUM_LEN };
GUARD(s2n_increment_sequence_number(&seq));
/* Write the plaintext data */
out.data = in->data;
out.size = data_bytes_to_take;
GUARD(s2n_stuffer_write(&conn->out, &out));
GUARD(s2n_hmac_update(mac, out.data, out.size));
/* Write the digest */
uint8_t *digest = s2n_stuffer_raw_write(&conn->out, mac_digest_size);
notnull_check(digest);
GUARD(s2n_hmac_digest(mac, digest, mac_digest_size));
GUARD(s2n_hmac_reset(mac));
if (cipher_suite->record_alg->cipher->type == S2N_CBC) {
/* Include padding bytes, each with the value 'p', and
* include an extra padding length byte, also with the value 'p'.
*/
for (int i = 0; i <= padding; i++) {
GUARD(s2n_stuffer_write_uint8(&conn->out, padding));
}
}
/* Rewind to rewrite/encrypt the packet */
GUARD(s2n_stuffer_rewrite(&conn->out));
/* Skip the header */
GUARD(s2n_stuffer_skip_write(&conn->out, S2N_TLS_RECORD_HEADER_LENGTH));
uint16_t encrypted_length = data_bytes_to_take + mac_digest_size;
switch (cipher_suite->record_alg->cipher->type) {
case S2N_AEAD:
GUARD(s2n_stuffer_skip_write(&conn->out, cipher_suite->record_alg->cipher->io.aead.record_iv_size));
encrypted_length += cipher_suite->record_alg->cipher->io.aead.tag_size;
break;
case S2N_CBC:
if (conn->actual_protocol_version > S2N_TLS10) {
/* Leave the IV alone and unencrypted */
GUARD(s2n_stuffer_skip_write(&conn->out, iv.size));
}
/* Encrypt the padding and the padding length byte too */
encrypted_length += padding + 1;
break;
case S2N_COMPOSITE:
/* Composite CBC expects a pointer starting at explicit IV: [Explicit IV | fragment | MAC | padding | padding len ]
* extra will account for the explicit IV len(if applicable), MAC digest len, padding len + padding byte.
*/
encrypted_length += extra;
break;
default:
break;
}
/* Do the encryption */
struct s2n_blob en = {0};
en.size = encrypted_length;
en.data = s2n_stuffer_raw_write(&conn->out, en.size);
notnull_check(en.data);
switch (cipher_suite->record_alg->cipher->type) {
case S2N_STREAM:
GUARD(cipher_suite->record_alg->cipher->io.stream.encrypt(session_key, &en, &en));
break;
case S2N_CBC:
GUARD(cipher_suite->record_alg->cipher->io.cbc.encrypt(session_key, &iv, &en, &en));
/* Copy the last encrypted block to be the next IV */
if (conn->actual_protocol_version < S2N_TLS11) {
gte_check(en.size, block_size);
memcpy_check(implicit_iv, en.data + en.size - block_size, block_size);
}
break;
case S2N_AEAD:
GUARD(cipher_suite->record_alg->cipher->io.aead.encrypt(session_key, &iv, &aad, &en, &en));
break;
case S2N_COMPOSITE:
/* This will: compute mac, append padding, append padding length, and encrypt */
GUARD(cipher_suite->record_alg->cipher->io.comp.encrypt(session_key, &iv, &en, &en));
/* Copy the last encrypted block to be the next IV */
gte_check(en.size, block_size);
memcpy_check(implicit_iv, en.data + en.size - block_size, block_size);
break;
default:
S2N_ERROR(S2N_ERR_CIPHER_TYPE);
break;
}
conn->wire_bytes_out += actual_fragment_length + S2N_TLS_RECORD_HEADER_LENGTH;
return data_bytes_to_take;
}
static int s2n_prf(struct s2n_connection *conn, struct s2n_blob *secret, struct s2n_blob *label, struct s2n_blob *seed_a,
struct s2n_blob *seed_b, struct s2n_blob *seed_c, struct s2n_blob *out)
{
/* seed_a is always required, seed_b is optional, if seed_c is provided seed_b must also be provided */
S2N_ERROR_IF(seed_a == NULL, S2N_ERR_PRF_INVALID_SEED);
S2N_ERROR_IF(seed_b == NULL && seed_c != NULL, S2N_ERR_PRF_INVALID_SEED);
if (conn->actual_protocol_version == S2N_SSLv3) {
return s2n_sslv3_prf(&conn->prf_space, secret, seed_a, seed_b, seed_c, out);
}
/* We zero the out blob because p_hash works by XOR'ing with the existing
* buffer. This is a little convoluted but means we can avoid dynamic memory
* allocation. When we call p_hash once (in the TLS1.2 case) it will produce
* the right values. When we call it twice in the regular case, the two
* outputs will be XORd just ass the TLS 1.0 and 1.1 RFCs require.
*/
GUARD(s2n_blob_zero(out));
/* Ensure that p_hash_hmac_impl is set, as it may have been reset for prf_space on s2n_connection_wipe.
* When in FIPS mode, the EVP API's must be used for the p_hash HMAC.
*/
conn->prf_space.tls.p_hash_hmac_impl = s2n_is_in_fips_mode() ? &s2n_evp_hmac : &s2n_hmac;
if (conn->actual_protocol_version == S2N_TLS12) {
return s2n_p_hash(&conn->prf_space, conn->secure.cipher_suite->tls12_prf_alg, secret, label, seed_a, seed_b,
seed_c, out);
}
struct s2n_blob half_secret = {.data = secret->data,.size = (secret->size + 1) / 2 };
GUARD(s2n_p_hash(&conn->prf_space, S2N_HMAC_MD5, &half_secret, label, seed_a, seed_b, seed_c, out));
half_secret.data += secret->size - half_secret.size;
GUARD(s2n_p_hash(&conn->prf_space, S2N_HMAC_SHA1, &half_secret, label, seed_a, seed_b, seed_c, out));
return 0;
}
int s2n_tls_prf_master_secret(struct s2n_connection *conn, struct s2n_blob *premaster_secret)
{
struct s2n_blob client_random = {.size = sizeof(conn->secure.client_random), .data = conn->secure.client_random};
struct s2n_blob server_random = {.size = sizeof(conn->secure.server_random), .data = conn->secure.server_random};
struct s2n_blob master_secret = {.size = sizeof(conn->secure.master_secret), .data = conn->secure.master_secret};
uint8_t master_secret_label[] = "master secret";
struct s2n_blob label = {.size = sizeof(master_secret_label) - 1, .data = master_secret_label};
return s2n_prf(conn, premaster_secret, &label, &client_random, &server_random, NULL, &master_secret);
}
int s2n_hybrid_prf_master_secret(struct s2n_connection *conn, struct s2n_blob *premaster_secret)
{
struct s2n_blob client_random = {.size = sizeof(conn->secure.client_random), .data = conn->secure.client_random};
struct s2n_blob server_random = {.size = sizeof(conn->secure.server_random), .data = conn->secure.server_random};
struct s2n_blob master_secret = {.size = sizeof(conn->secure.master_secret), .data = conn->secure.master_secret};
uint8_t master_secret_label[] = "hybrid master secret";
struct s2n_blob label = {.size = sizeof(master_secret_label) - 1, .data = master_secret_label};
return s2n_prf(conn, premaster_secret, &label, &client_random, &server_random, &conn->secure.client_key_exchange_message, &master_secret);
}
static int s2n_sslv3_finished(struct s2n_connection *conn, uint8_t prefix[4], struct s2n_hash_state *md5, struct s2n_hash_state *sha1, uint8_t * out)
{
uint8_t xorpad1[48] =
{ 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36,
0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36
};
uint8_t xorpad2[48] =
{ 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c,
0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c
};
uint8_t *md5_digest = out;
uint8_t *sha_digest = out + MD5_DIGEST_LENGTH;
lte_check(MD5_DIGEST_LENGTH + SHA_DIGEST_LENGTH, sizeof(conn->handshake.client_finished));
GUARD(s2n_hash_update(md5, prefix, 4));
GUARD(s2n_hash_update(md5, conn->secure.master_secret, sizeof(conn->secure.master_secret)));
GUARD(s2n_hash_update(md5, xorpad1, 48));
GUARD(s2n_hash_digest(md5, md5_digest, MD5_DIGEST_LENGTH));
GUARD(s2n_hash_reset(md5));
GUARD(s2n_hash_update(md5, conn->secure.master_secret, sizeof(conn->secure.master_secret)));
GUARD(s2n_hash_update(md5, xorpad2, 48));
GUARD(s2n_hash_update(md5, md5_digest, MD5_DIGEST_LENGTH));
GUARD(s2n_hash_digest(md5, md5_digest, MD5_DIGEST_LENGTH));
GUARD(s2n_hash_reset(md5));
GUARD(s2n_hash_update(sha1, prefix, 4));
GUARD(s2n_hash_update(sha1, conn->secure.master_secret, sizeof(conn->secure.master_secret)));
GUARD(s2n_hash_update(sha1, xorpad1, 40));
GUARD(s2n_hash_digest(sha1, sha_digest, SHA_DIGEST_LENGTH));
GUARD(s2n_hash_reset(sha1));
GUARD(s2n_hash_update(sha1, conn->secure.master_secret, sizeof(conn->secure.master_secret)));
GUARD(s2n_hash_update(sha1, xorpad2, 40));
GUARD(s2n_hash_update(sha1, sha_digest, SHA_DIGEST_LENGTH));
GUARD(s2n_hash_digest(sha1, sha_digest, SHA_DIGEST_LENGTH));
GUARD(s2n_hash_reset(sha1));
return 0;
}
static int s2n_sslv3_client_finished(struct s2n_connection *conn)
{
uint8_t prefix[4] = { 0x43, 0x4c, 0x4e, 0x54 };
lte_check(MD5_DIGEST_LENGTH + SHA_DIGEST_LENGTH, sizeof(conn->handshake.client_finished));
GUARD(s2n_hash_copy(&conn->handshake.prf_md5_hash_copy, &conn->handshake.md5));
GUARD(s2n_hash_copy(&conn->handshake.prf_sha1_hash_copy, &conn->handshake.sha1));
return s2n_sslv3_finished(conn, prefix, &conn->handshake.prf_md5_hash_copy, &conn->handshake.prf_sha1_hash_copy, conn->handshake.client_finished);
}
static int s2n_sslv3_server_finished(struct s2n_connection *conn)
{
uint8_t prefix[4] = { 0x53, 0x52, 0x56, 0x52 };
lte_check(MD5_DIGEST_LENGTH + SHA_DIGEST_LENGTH, sizeof(conn->handshake.server_finished));
GUARD(s2n_hash_copy(&conn->handshake.prf_md5_hash_copy, &conn->handshake.md5));
GUARD(s2n_hash_copy(&conn->handshake.prf_sha1_hash_copy, &conn->handshake.sha1));
return s2n_sslv3_finished(conn, prefix, &conn->handshake.prf_md5_hash_copy, &conn->handshake.prf_sha1_hash_copy, conn->handshake.server_finished);
}
int s2n_prf_client_finished(struct s2n_connection *conn)
{
struct s2n_blob master_secret, md5, sha;
uint8_t md5_digest[MD5_DIGEST_LENGTH];
uint8_t sha_digest[SHA384_DIGEST_LENGTH];
uint8_t client_finished_label[] = "client finished";
struct s2n_blob client_finished = {0};
struct s2n_blob label = {0};
if (conn->actual_protocol_version == S2N_SSLv3) {
return s2n_sslv3_client_finished(conn);
}
client_finished.data = conn->handshake.client_finished;
client_finished.size = S2N_TLS_FINISHED_LEN;
label.data = client_finished_label;
label.size = sizeof(client_finished_label) - 1;
master_secret.data = conn->secure.master_secret;
master_secret.size = sizeof(conn->secure.master_secret);
if (conn->actual_protocol_version == S2N_TLS12) {
switch (conn->secure.cipher_suite->tls12_prf_alg) {
case S2N_HMAC_SHA256:
GUARD(s2n_hash_copy(&conn->handshake.prf_tls12_hash_copy, &conn->handshake.sha256));
GUARD(s2n_hash_digest(&conn->handshake.prf_tls12_hash_copy, sha_digest, SHA256_DIGEST_LENGTH));
sha.size = SHA256_DIGEST_LENGTH;
break;
case S2N_HMAC_SHA384:
GUARD(s2n_hash_copy(&conn->handshake.prf_tls12_hash_copy, &conn->handshake.sha384));
GUARD(s2n_hash_digest(&conn->handshake.prf_tls12_hash_copy, sha_digest, SHA384_DIGEST_LENGTH));
sha.size = SHA384_DIGEST_LENGTH;
break;
default:
S2N_ERROR(S2N_ERR_PRF_INVALID_ALGORITHM);
}
sha.data = sha_digest;
return s2n_prf(conn, &master_secret, &label, &sha, NULL, NULL, &client_finished);
}
GUARD(s2n_hash_copy(&conn->handshake.prf_md5_hash_copy, &conn->handshake.md5));
GUARD(s2n_hash_copy(&conn->handshake.prf_sha1_hash_copy, &conn->handshake.sha1));
GUARD(s2n_hash_digest(&conn->handshake.prf_md5_hash_copy, md5_digest, MD5_DIGEST_LENGTH));
GUARD(s2n_hash_digest(&conn->handshake.prf_sha1_hash_copy, sha_digest, SHA_DIGEST_LENGTH));
md5.data = md5_digest;
md5.size = MD5_DIGEST_LENGTH;
sha.data = sha_digest;
sha.size = SHA_DIGEST_LENGTH;
return s2n_prf(conn, &master_secret, &label, &md5, &sha, NULL, &client_finished);
}
int s2n_prf_server_finished(struct s2n_connection *conn)
{
struct s2n_blob master_secret, md5, sha;
uint8_t md5_digest[MD5_DIGEST_LENGTH];
uint8_t sha_digest[SHA384_DIGEST_LENGTH];
uint8_t server_finished_label[] = "server finished";
struct s2n_blob server_finished = {0};
struct s2n_blob label = {0};
if (conn->actual_protocol_version == S2N_SSLv3) {
return s2n_sslv3_server_finished(conn);
}
server_finished.data = conn->handshake.server_finished;
server_finished.size = S2N_TLS_FINISHED_LEN;
label.data = server_finished_label;
label.size = sizeof(server_finished_label) - 1;
master_secret.data = conn->secure.master_secret;
master_secret.size = sizeof(conn->secure.master_secret);
if (conn->actual_protocol_version == S2N_TLS12) {
switch (conn->secure.cipher_suite->tls12_prf_alg) {
case S2N_HMAC_SHA256:
GUARD(s2n_hash_copy(&conn->handshake.prf_tls12_hash_copy, &conn->handshake.sha256));
GUARD(s2n_hash_digest(&conn->handshake.prf_tls12_hash_copy, sha_digest, SHA256_DIGEST_LENGTH));
sha.size = SHA256_DIGEST_LENGTH;
break;
case S2N_HMAC_SHA384:
GUARD(s2n_hash_copy(&conn->handshake.prf_tls12_hash_copy, &conn->handshake.sha384));
GUARD(s2n_hash_digest(&conn->handshake.prf_tls12_hash_copy, sha_digest, SHA384_DIGEST_LENGTH));
sha.size = SHA384_DIGEST_LENGTH;
break;
default:
S2N_ERROR(S2N_ERR_PRF_INVALID_ALGORITHM);
}
sha.data = sha_digest;
return s2n_prf(conn, &master_secret, &label, &sha, NULL, NULL, &server_finished);
}
GUARD(s2n_hash_copy(&conn->handshake.prf_md5_hash_copy, &conn->handshake.md5));
GUARD(s2n_hash_copy(&conn->handshake.prf_sha1_hash_copy, &conn->handshake.sha1));
GUARD(s2n_hash_digest(&conn->handshake.prf_md5_hash_copy, md5_digest, MD5_DIGEST_LENGTH));
GUARD(s2n_hash_digest(&conn->handshake.prf_sha1_hash_copy, sha_digest, SHA_DIGEST_LENGTH));
md5.data = md5_digest;
md5.size = MD5_DIGEST_LENGTH;
sha.data = sha_digest;
sha.size = SHA_DIGEST_LENGTH;
return s2n_prf(conn, &master_secret, &label, &md5, &sha, NULL, &server_finished);
}
static int s2n_prf_make_client_key(struct s2n_connection *conn, struct s2n_stuffer *key_material)
{
struct s2n_blob client_key = {0};
client_key.size = conn->secure.cipher_suite->record_alg->cipher->key_material_size;
client_key.data = s2n_stuffer_raw_read(key_material, client_key.size);
notnull_check(client_key.data);
if (conn->mode == S2N_CLIENT) {
GUARD(conn->secure.cipher_suite->record_alg->cipher->set_encryption_key(&conn->secure.client_key, &client_key));
} else {
GUARD(conn->secure.cipher_suite->record_alg->cipher->set_decryption_key(&conn->secure.client_key, &client_key));
}
return 0;
}
static int s2n_prf_make_server_key(struct s2n_connection *conn, struct s2n_stuffer *key_material)
{
struct s2n_blob server_key = {0};
server_key.size = conn->secure.cipher_suite->record_alg->cipher->key_material_size;
server_key.data = s2n_stuffer_raw_read(key_material, server_key.size);
notnull_check(server_key.data);
if (conn->mode == S2N_SERVER) {
GUARD(conn->secure.cipher_suite->record_alg->cipher->set_encryption_key(&conn->secure.server_key, &server_key));
} else {
GUARD(conn->secure.cipher_suite->record_alg->cipher->set_decryption_key(&conn->secure.server_key, &server_key));
}
return 0;
}
int s2n_prf_key_expansion(struct s2n_connection *conn)
{
struct s2n_blob client_random = {.data = conn->secure.client_random,.size = sizeof(conn->secure.client_random) };
struct s2n_blob server_random = {.data = conn->secure.server_random,.size = sizeof(conn->secure.server_random) };
struct s2n_blob master_secret = {.data = conn->secure.master_secret,.size = sizeof(conn->secure.master_secret) };
struct s2n_blob label, out;
uint8_t key_expansion_label[] = "key expansion";
uint8_t key_block[S2N_MAX_KEY_BLOCK_LEN];
label.data = key_expansion_label;
label.size = sizeof(key_expansion_label) - 1;
out.data = key_block;
out.size = sizeof(key_block);
struct s2n_stuffer key_material = {{0}};
GUARD(s2n_prf(conn, &master_secret, &label, &server_random, &client_random, NULL, &out));
GUARD(s2n_stuffer_init(&key_material, &out));
GUARD(s2n_stuffer_write(&key_material, &out));
GUARD(conn->secure.cipher_suite->record_alg->cipher->init(&conn->secure.client_key));
GUARD(conn->secure.cipher_suite->record_alg->cipher->init(&conn->secure.server_key));
/* Check that we have a valid MAC and key size */
uint8_t mac_size;
if (conn->secure.cipher_suite->record_alg->cipher->type == S2N_COMPOSITE) {
mac_size = conn->secure.cipher_suite->record_alg->cipher->io.comp.mac_key_size;
} else {
GUARD(s2n_hmac_digest_size(conn->secure.cipher_suite->record_alg->hmac_alg, &mac_size));
}
/* Seed the client MAC */
uint8_t *client_mac_write_key = s2n_stuffer_raw_read(&key_material, mac_size);
notnull_check(client_mac_write_key);
GUARD(s2n_hmac_reset(&conn->secure.client_record_mac));
GUARD(s2n_hmac_init(&conn->secure.client_record_mac, conn->secure.cipher_suite->record_alg->hmac_alg, client_mac_write_key, mac_size));
/* Seed the server MAC */
uint8_t *server_mac_write_key = s2n_stuffer_raw_read(&key_material, mac_size);
notnull_check(server_mac_write_key);
GUARD(s2n_hmac_reset(&conn->secure.server_record_mac));
GUARD(s2n_hmac_init(&conn->secure.server_record_mac, conn->secure.cipher_suite->record_alg->hmac_alg, server_mac_write_key, mac_size));
/* Make the client key */
GUARD(s2n_prf_make_client_key(conn, &key_material));
/* Make the server key */
GUARD(s2n_prf_make_server_key(conn, &key_material));
/* Composite CBC does MAC inside the cipher, pass it the MAC key.
* Must happen after setting encryption/decryption keys.
*/
if (conn->secure.cipher_suite->record_alg->cipher->type == S2N_COMPOSITE) {
GUARD(conn->secure.cipher_suite->record_alg->cipher->io.comp.set_mac_write_key(&conn->secure.server_key, server_mac_write_key, mac_size));
GUARD(conn->secure.cipher_suite->record_alg->cipher->io.comp.set_mac_write_key(&conn->secure.client_key, client_mac_write_key, mac_size));
}
/* TLS >= 1.1 has no implicit IVs for non AEAD ciphers */
if (conn->actual_protocol_version > S2N_TLS10 && conn->secure.cipher_suite->record_alg->cipher->type != S2N_AEAD) {
return 0;
}
uint32_t implicit_iv_size = 0;
switch (conn->secure.cipher_suite->record_alg->cipher->type) {
case S2N_AEAD:
implicit_iv_size = conn->secure.cipher_suite->record_alg->cipher->io.aead.fixed_iv_size;
break;
case S2N_CBC:
implicit_iv_size = conn->secure.cipher_suite->record_alg->cipher->io.cbc.block_size;
break;
case S2N_COMPOSITE:
implicit_iv_size = conn->secure.cipher_suite->record_alg->cipher->io.comp.block_size;
break;
/* No-op for stream ciphers */
default:
break;
}
struct s2n_blob client_implicit_iv = {.data = conn->secure.client_implicit_iv,.size = implicit_iv_size };
struct s2n_blob server_implicit_iv = {.data = conn->secure.server_implicit_iv,.size = implicit_iv_size };
GUARD(s2n_stuffer_read(&key_material, &client_implicit_iv));
GUARD(s2n_stuffer_read(&key_material, &server_implicit_iv));
return 0;
}
int main(int argc, char **argv)
{
uint8_t digest_pad[256];
uint8_t check_pad[256];
uint8_t output_pad[256];
struct s2n_stuffer output;
uint8_t sekrit[] = "sekrit";
uint8_t longsekrit[] = "This is a really really really long key on purpose to make sure that it's longer than the block size";
uint8_t hello[] = "Hello world!";
struct s2n_hmac_state hmac, copy;
struct s2n_hmac_state cmac;
struct s2n_blob out = {.data = output_pad,.size = sizeof(output_pad) };
BEGIN_TEST();
/* Initialise our output stuffers */
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_MD5), 16);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_MD5, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_copy(©, &hmac));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 16));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "3ad68c53dc1a3cf35f6469877fae4585", 16 * 2), 0);
/* Check the copy */
EXPECT_SUCCESS(s2n_hmac_digest(©, digest_pad, 16));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "3ad68c53dc1a3cf35f6469877fae4585", 16 * 2), 0);
/* Test that a reset works */
EXPECT_SUCCESS(s2n_hmac_reset(&hmac));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 16));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "3ad68c53dc1a3cf35f6469877fae4585", 16 * 2), 0);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_MD5, longsekrit, strlen((char *)longsekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 16));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "2ce569d61f4ee6ad9ceebe02a112ace7", 16 * 2), 0);
/* Test that a reset works */
EXPECT_SUCCESS(s2n_hmac_reset(&hmac));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 16));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "2ce569d61f4ee6ad9ceebe02a112ace7", 16 * 2), 0);
/* Verify that _verify works */
EXPECT_SUCCESS(s2n_hmac_init(&cmac, S2N_HMAC_MD5, longsekrit, strlen((char *)longsekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&cmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&cmac, check_pad, 16));
EXPECT_SUCCESS(s2n_hmac_digest_verify(digest_pad, 16, check_pad, 16));
/* Try SHA1 */
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_SHA1), 20);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_SHA1, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 20));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 20; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "6d301861b599938eca94f6de917362886d97882f", 20 * 2), 0);
/* Try SHA256 */
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_SHA256), 32);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_SHA256, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 32));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 32; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "adc20b12d236e6d1824d690622e33ead4f67ba5a2be9606fe762b2dd859a78a9", 32 * 2), 0);
/* Try SHA384 */
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_SHA384), 48);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_SHA384, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 48));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 48; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "8552563cadd583b79dcc7225bb79bc6483c63f259187162e1c9d4283eb6299ef1bc3ca81c0c40fc7b22f7a1f3b93adb4", 48 * 2), 0);
/* Try SHA512 */
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_SHA512), 64);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_SHA512, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 64));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 64; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from python */
EXPECT_EQUAL(memcmp(output_pad, "0a834a1ed265042e2897405edb4fdd9818950cd5bea10b828f2fed45a1cb6dbd2107e4b04eb20f211998cd4e8c7e11ebdcb0103ac63882481e1bb8083d07f4be", 64 * 2), 0);
/* Try SSLv3 MD5 */
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_SSLv3_MD5), 16);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_SSLv3_MD5, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 16));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from Go */
EXPECT_EQUAL(memcmp(output_pad, "d4f0d06b9765de23e6c3e33a24c5ded0", 16 * 2), 0);
/* Test that a reset works */
EXPECT_SUCCESS(s2n_hmac_reset(&hmac));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 16));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 16; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
EXPECT_EQUAL(memcmp(output_pad, "d4f0d06b9765de23e6c3e33a24c5ded0", 16 * 2), 0);
/* Try SSLv3 SHA1 */
EXPECT_EQUAL(s2n_hmac_digest_size(S2N_HMAC_SSLv3_SHA1), 20);
EXPECT_SUCCESS(s2n_hmac_init(&hmac, S2N_HMAC_SSLv3_SHA1, sekrit, strlen((char *)sekrit)));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 20));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 20; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
/* Reference value from Go */
EXPECT_EQUAL(memcmp(output_pad, "b0c66179f6eb5a46b4b7c4fca84b3ea5161b7326", 20 * 2), 0);
/* Test that a reset works */
EXPECT_SUCCESS(s2n_hmac_reset(&hmac));
EXPECT_SUCCESS(s2n_hmac_update(&hmac, hello, strlen((char *)hello)));
EXPECT_SUCCESS(s2n_hmac_digest(&hmac, digest_pad, 20));
EXPECT_SUCCESS(s2n_stuffer_init(&output, &out));
for (int i = 0; i < 20; i++) {
EXPECT_SUCCESS(s2n_stuffer_write_uint8_hex(&output, digest_pad[i]));
}
EXPECT_EQUAL(memcmp(output_pad, "b0c66179f6eb5a46b4b7c4fca84b3ea5161b7326", 20 * 2), 0);
END_TEST();
}
int s2n_prf_key_expansion(struct s2n_connection *conn)
{
struct s2n_blob client_random = {.data = conn->secure.client_random,.size = sizeof(conn->secure.client_random) };
struct s2n_blob server_random = {.data = conn->secure.server_random,.size = sizeof(conn->secure.server_random) };
struct s2n_blob master_secret = {.data = conn->secure.master_secret,.size = sizeof(conn->secure.master_secret) };
struct s2n_blob label, out;
uint8_t key_expansion_label[] = "key expansion";
uint8_t key_block[S2N_MAX_KEY_BLOCK_LEN];
label.data = key_expansion_label;
label.size = sizeof(key_expansion_label) - 1;
out.data = key_block;
out.size = sizeof(key_block);
struct s2n_stuffer key_material;
GUARD(s2n_prf(conn, &master_secret, &label, &server_random, &client_random, &out));
GUARD(s2n_stuffer_init(&key_material, &out));
GUARD(s2n_stuffer_write(&key_material, &out));
GUARD(conn->secure.cipher_suite->cipher->init(&conn->secure.client_key));
GUARD(conn->secure.cipher_suite->cipher->init(&conn->secure.server_key));
/* What's our hmac algorithm? */
s2n_hmac_algorithm hmac_alg = conn->secure.cipher_suite->hmac_alg;
if (conn->actual_protocol_version == S2N_SSLv3) {
if (hmac_alg == S2N_HMAC_SHA1) {
hmac_alg = S2N_HMAC_SSLv3_SHA1;
} else if (hmac_alg == S2N_HMAC_MD5) {
hmac_alg = S2N_HMAC_SSLv3_MD5;
} else {
S2N_ERROR(S2N_ERR_HMAC_INVALID_ALGORITHM);
}
}
/* Check that we have a valid MAC and key size */
int mac_size;
GUARD((mac_size = s2n_hmac_digest_size(hmac_alg)));
/* Seed the client MAC */
uint8_t *client_write_mac_key = s2n_stuffer_raw_read(&key_material, mac_size);
notnull_check(client_write_mac_key);
GUARD(s2n_hmac_init(&conn->secure.client_record_mac, hmac_alg, client_write_mac_key, mac_size));
/* Seed the server MAC */
uint8_t *server_write_mac_key = s2n_stuffer_raw_read(&key_material, mac_size);
notnull_check(server_write_mac_key);
GUARD(s2n_hmac_init(&conn->secure.server_record_mac, hmac_alg, server_write_mac_key, mac_size));
/* Make the client key */
struct s2n_blob client_key;
client_key.size = conn->secure.cipher_suite->cipher->key_material_size;
client_key.data = s2n_stuffer_raw_read(&key_material, client_key.size);
notnull_check(client_key.data);
if (conn->mode == S2N_CLIENT) {
GUARD(conn->secure.cipher_suite->cipher->get_encryption_key(&conn->secure.client_key, &client_key));
} else {
GUARD(conn->secure.cipher_suite->cipher->get_decryption_key(&conn->secure.client_key, &client_key));
}
/* Make the server key */
struct s2n_blob server_key;
server_key.size = conn->secure.cipher_suite->cipher->key_material_size;
server_key.data = s2n_stuffer_raw_read(&key_material, server_key.size);
notnull_check(server_key.data);
if (conn->mode == S2N_SERVER) {
GUARD(conn->secure.cipher_suite->cipher->get_encryption_key(&conn->secure.server_key, &server_key));
} else {
GUARD(conn->secure.cipher_suite->cipher->get_decryption_key(&conn->secure.server_key, &server_key));
}
/* TLS >= 1.1 has no implicit IVs for non AEAD ciphers */
if (conn->actual_protocol_version > S2N_TLS10 &&
conn->secure.cipher_suite->cipher->type != S2N_AEAD) {
return 0;
}
uint32_t implicit_iv_size = 0;
switch(conn->secure.cipher_suite->cipher->type) {
case S2N_AEAD:
implicit_iv_size = conn->secure.cipher_suite->cipher->io.aead.fixed_iv_size;
break;
case S2N_CBC:
implicit_iv_size = conn->secure.cipher_suite->cipher->io.cbc.block_size;
break;
/* No-op for stream ciphers */
default:
break;
}
struct s2n_blob client_implicit_iv = { .data = conn->secure.client_implicit_iv, .size = implicit_iv_size };
struct s2n_blob server_implicit_iv = { .data = conn->secure.server_implicit_iv, .size = implicit_iv_size };
GUARD(s2n_stuffer_read(&key_material, &client_implicit_iv));
GUARD(s2n_stuffer_read(&key_material, &server_implicit_iv));
return 0;
}