/*
* For each name in the cert. Iterate them. Call the callback. If one returns true, then consider it validated,
* if none of them return true, the cert is considered invalid.
*/
static uint8_t s2n_verify_host_information(struct s2n_x509_validator *validator, struct s2n_connection *conn, X509 *public_cert) {
uint8_t verified = 0;
uint8_t san_found = 0;
/* Check SubjectAltNames before CommonName as per RFC 6125 6.4.4 */
STACK_OF(GENERAL_NAME) *names_list = X509_get_ext_d2i(public_cert, NID_subject_alt_name, NULL, NULL);
int n = sk_GENERAL_NAME_num(names_list);
for (int i = 0; i < n && !verified; i++) {
GENERAL_NAME *current_name = sk_GENERAL_NAME_value(names_list, i);
if (current_name->type == GEN_DNS) {
san_found = 1;
const char *name = (const char *) ASN1_STRING_data(current_name->d.ia5);
size_t name_len = (size_t) ASN1_STRING_length(current_name->d.ia5);
verified = conn->verify_host_fn(name, name_len, conn->data_for_verify_host);
}
}
GENERAL_NAMES_free(names_list);
/* if no SubjectAltNames of type DNS found, go to the common name. */
if (!san_found) {
X509_NAME *subject_name = X509_get_subject_name(public_cert);
if (subject_name) {
int next_idx = 0, curr_idx = -1;
while ((next_idx = X509_NAME_get_index_by_NID(subject_name, NID_commonName, curr_idx)) >= 0) {
curr_idx = next_idx;
}
if (curr_idx >= 0) {
ASN1_STRING *common_name =
X509_NAME_ENTRY_get_data(X509_NAME_get_entry(subject_name, curr_idx));
if (common_name) {
char peer_cn[255];
static size_t peer_cn_size = sizeof(peer_cn);
memset_check(&peer_cn, 0, peer_cn_size);
// X520CommonName allows the following ANSI string types per RFC 5280 Appendix A.1
if (ASN1_STRING_type(common_name) == V_ASN1_TELETEXSTRING ||
ASN1_STRING_type(common_name) == V_ASN1_PRINTABLESTRING ||
ASN1_STRING_type(common_name) == V_ASN1_UNIVERSALSTRING ||
ASN1_STRING_type(common_name) == V_ASN1_UTF8STRING ||
ASN1_STRING_type(common_name) == V_ASN1_BMPSTRING ) {
size_t len = (size_t) ASN1_STRING_length(common_name);
lte_check(len, sizeof(peer_cn) - 1);
memcpy_check(peer_cn, ASN1_STRING_data(common_name), len);
verified = conn->verify_host_fn(peer_cn, len, conn->data_for_verify_host);
}
}
}
}
}
return verified;
}
int s2n_client_extensions_recv(struct s2n_connection *conn, struct s2n_blob *extensions)
{
struct s2n_stuffer in;
GUARD(s2n_stuffer_init(&in, extensions));
GUARD(s2n_stuffer_write(&in, extensions));
while (s2n_stuffer_data_available(&in)) {
struct s2n_blob ext;
uint16_t extension_type, extension_size;
struct s2n_stuffer extension;
GUARD(s2n_stuffer_read_uint16(&in, &extension_type));
GUARD(s2n_stuffer_read_uint16(&in, &extension_size));
ext.size = extension_size;
lte_check(extension_size, s2n_stuffer_data_available(&in));
ext.data = s2n_stuffer_raw_read(&in, ext.size);
notnull_check(ext.data);
GUARD(s2n_stuffer_init(&extension, &ext));
GUARD(s2n_stuffer_write(&extension, &ext));
switch (extension_type) {
case TLS_EXTENSION_SERVER_NAME:
GUARD(s2n_recv_client_server_name(conn, &extension));
break;
case TLS_EXTENSION_SIGNATURE_ALGORITHMS:
GUARD(s2n_recv_client_signature_algorithms(conn, &extension, &conn->secure.conn_hash_alg, &conn->secure.conn_sig_alg));
break;
case TLS_EXTENSION_ALPN:
GUARD(s2n_recv_client_alpn(conn, &extension));
break;
case TLS_EXTENSION_STATUS_REQUEST:
GUARD(s2n_recv_client_status_request(conn, &extension));
break;
case TLS_EXTENSION_ELLIPTIC_CURVES:
GUARD(s2n_recv_client_elliptic_curves(conn, &extension));
break;
case TLS_EXTENSION_EC_POINT_FORMATS:
GUARD(s2n_recv_client_ec_point_formats(conn, &extension));
break;
case TLS_EXTENSION_RENEGOTIATION_INFO:
GUARD(s2n_recv_client_renegotiation_info(conn, &extension));
break;
case TLS_EXTENSION_SCT_LIST:
GUARD(s2n_recv_client_sct_list(conn, &extension));
break;
case TLS_EXTENSION_MAX_FRAG_LEN:
GUARD(s2n_recv_client_max_frag_len(conn, &extension));
break;
}
}
return 0;
}
static int s2n_sslv3_server_finished(struct s2n_connection *conn)
{
uint8_t prefix[4] = { 0x53, 0x52, 0x56, 0x52 };
struct s2n_hash_state md5, sha1;
lte_check(MD5_DIGEST_LENGTH + SHA_DIGEST_LENGTH, sizeof(conn->handshake.server_finished));
GUARD(s2n_hash_copy(&md5, &conn->handshake.md5));
GUARD(s2n_hash_copy(&sha1, &conn->handshake.sha1));
return s2n_sslv3_finished(conn, prefix, &md5, &sha1, conn->handshake.server_finished);
}
/* 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_ecdsa_verify(const struct s2n_pkey *pub, struct s2n_hash_state *digest, struct s2n_blob *signature)
{
const s2n_ecdsa_public_key *key = &pub->key.ecdsa_key;
notnull_check(key->ec_key);
uint8_t digest_length;
GUARD(s2n_hash_digest_size(digest->alg, &digest_length));
lte_check(digest_length, S2N_MAX_DIGEST_LEN);
uint8_t digest_out[S2N_MAX_DIGEST_LEN];
GUARD(s2n_hash_digest(digest, digest_out, digest_length));
/* ECDSA_verify ignores the first parameter */
GUARD_OSSL(ECDSA_verify(0, digest_out, digest_length, signature->data, signature->size, key->ec_key), S2N_ERR_VERIFY_SIGNATURE);
GUARD(s2n_hash_reset(digest));
return 0;
}
static int s2n_ecdsa_sign(const struct s2n_pkey *priv, struct s2n_hash_state *digest, struct s2n_blob *signature)
{
const s2n_ecdsa_private_key *key = &priv->key.ecdsa_key;
notnull_check(key->ec_key);
uint8_t digest_length;
GUARD(s2n_hash_digest_size(digest->alg, &digest_length));
lte_check(digest_length, S2N_MAX_DIGEST_LEN);
uint8_t digest_out[S2N_MAX_DIGEST_LEN];
GUARD(s2n_hash_digest(digest, digest_out, digest_length));
unsigned int signature_size = signature->size;
GUARD_OSSL(ECDSA_sign(0, digest_out, digest_length, signature->data, &signature_size, key->ec_key), S2N_ERR_SIGN);
S2N_ERROR_IF(signature_size > signature->size, S2N_ERR_SIZE_MISMATCH);
signature->size = signature_size;
GUARD(s2n_hash_reset(digest));
return 0;
}
int s2n_rsa_keys_match(struct s2n_rsa_public_key *pub, struct s2n_rsa_private_key *priv)
{
uint8_t plain_inpad[36], plain_outpad[36], encpad[8192];
struct s2n_blob plain_in, plain_out, enc;
plain_in.data = plain_inpad;
plain_in.size = sizeof(plain_inpad);
GUARD(s2n_get_private_random_data(&plain_in));
enc.data = encpad;
enc.size = s2n_rsa_public_encrypted_size(pub);
lte_check(enc.size, sizeof(encpad));
GUARD(s2n_rsa_encrypt(pub, &plain_in, &enc));
plain_out.data = plain_outpad;
plain_out.size = sizeof(plain_outpad);
GUARD(s2n_rsa_decrypt(priv, &enc, &plain_out));
if (memcmp(plain_in.data, plain_out.data, plain_in.size)) {
S2N_ERROR(S2N_ERR_KEY_MISMATCH);
}
return 0;
}
/**
* Private helper: write n (up to 64) bits of hex data
*/
static int s2n_stuffer_write_n_bits_hex(struct s2n_stuffer *stuffer, uint8_t n, uint64_t u)
{
uint8_t hex_data[16] = { 0 };
struct s2n_blob b = { .data = hex_data, .size = n / 4 };
lte_check(n, 64);
for (int i = b.size; i > 0; i--) {
b.data[i - 1] = hex[u & 0x0f];
u >>= 4;
}
GUARD(s2n_stuffer_write(stuffer, &b));
return 0;
}
int s2n_stuffer_write_uint64_hex(struct s2n_stuffer *stuffer, uint64_t u)
{
return s2n_stuffer_write_n_bits_hex(stuffer, 64, u);
}
int s2n_stuffer_write_uint32_hex(struct s2n_stuffer *stuffer, uint32_t u)
{
return s2n_stuffer_write_n_bits_hex(stuffer, 32, u);
}
int s2n_stuffer_write_uint16_hex(struct s2n_stuffer *stuffer, uint16_t u)
{
return s2n_stuffer_write_n_bits_hex(stuffer, 16, u);
}
int s2n_stuffer_write_uint8_hex(struct s2n_stuffer *stuffer, uint8_t u)
{
return s2n_stuffer_write_n_bits_hex(stuffer, 8, u);
}
int s2n_stuffer_alloc_ro_from_hex_string(struct s2n_stuffer *stuffer, const char *str)
{
if (strlen(str) % 2) {
S2N_ERROR(S2N_ERR_SIZE_MISMATCH);
}
GUARD(s2n_stuffer_alloc(stuffer, strlen(str) / 2));
for (int i = 0; i < strlen(str); i += 2) {
uint8_t u = 0;
if (str[i] >= '0' && str[i] <= '9') {
u = str[i] - '0';
} else if (str[i] >= 'a' && str[i] <= 'f') {
u = str[i] - 'a' + 10;
} else if (str[i] >= 'A' && str[i] <= 'F') {
u = str[i] - 'A' + 10;
} else {
S2N_ERROR(S2N_ERR_BAD_MESSAGE);
}
u <<= 4;
if (str[i + 1] >= '0' && str[i + 1] <= '9') {
u |= str[i + 1] - '0';
} else if (str[i + 1] >= 'a' && str[i + 1] <= 'f') {
u |= str[i + 1] - 'a' + 10;
} else if (str[i + 1] >= 'A' && str[i + 1] <= 'F') {
u |= str[i + 1] - 'A' + 10;
} else {
S2N_ERROR(S2N_ERR_BAD_MESSAGE);
}
GUARD(s2n_stuffer_write_uint8(stuffer, u));
}
return 0;
}
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;
}
static int s2n_drbg_bits(struct s2n_drbg *drbg, struct s2n_blob *out)
{
struct s2n_blob value = {.data = drbg->v,.size = sizeof(drbg->v) };
int block_aligned_size = out->size - (out->size % S2N_DRBG_BLOCK_SIZE);
/* Per NIST SP800-90A 10.2.1.2: */
for (int i = 0; i < block_aligned_size; i += S2N_DRBG_BLOCK_SIZE) {
GUARD(s2n_increment_sequence_number(&value));
GUARD(s2n_drbg_block_encrypt(drbg->ctx, drbg->v, out->data + i));
drbg->bytes_used += S2N_DRBG_BLOCK_SIZE;
}
if (out->size <= block_aligned_size) {
return 0;
}
uint8_t spare_block[S2N_DRBG_BLOCK_SIZE];
GUARD(s2n_increment_sequence_number(&value));
GUARD(s2n_drbg_block_encrypt(drbg->ctx, drbg->v, spare_block));
drbg->bytes_used += S2N_DRBG_BLOCK_SIZE;
memcpy_check(out->data + block_aligned_size, spare_block, out->size - block_aligned_size);
return 0;
}
static int s2n_drbg_update(struct s2n_drbg *drbg, struct s2n_blob *provided_data)
{
uint8_t temp[32];
struct s2n_blob temp_blob = {.data = temp,.size = sizeof(temp) };
eq_check(provided_data->size, sizeof(temp));
GUARD(s2n_drbg_bits(drbg, &temp_blob));
/* XOR in the provided data */
for (int i = 0; i < provided_data->size; i++) {
temp[i] ^= provided_data->data[i];
}
/* Update the key and value */
GUARD_OSSL(EVP_EncryptInit_ex(drbg->ctx, EVP_aes_128_ecb(), NULL, temp, NULL), S2N_ERR_DRBG);
memcpy_check(drbg->v, temp + S2N_DRBG_BLOCK_SIZE, S2N_DRBG_BLOCK_SIZE);
return 0;
}
int s2n_drbg_seed(struct s2n_drbg *drbg, struct s2n_blob *ps)
{
uint8_t seed[32];
struct s2n_blob blob = {.data = seed,.size = sizeof(seed) };
lte_check(ps->size, sizeof(seed));
if (drbg->entropy_generator) {
GUARD(drbg->entropy_generator(&blob));
} else {
GUARD(s2n_get_urandom_data(&blob));
}
for (int i = 0; i < ps->size; i++) {
blob.data[i] ^= ps->data[i];
}
GUARD(s2n_drbg_update(drbg, &blob));
drbg->bytes_used = 0;
drbg->generation += 1;
return 0;
}
int s2n_drbg_instantiate(struct s2n_drbg *drbg, struct s2n_blob *personalization_string)
{
struct s2n_blob value = {.data = drbg->v,.size = sizeof(drbg->v) };
uint8_t ps_prefix[32];
struct s2n_blob ps = {.data = ps_prefix,.size = sizeof(ps_prefix) };
/* Start off with zeroed data, per 10.2.1.3.1 item 4 */
GUARD(s2n_blob_zero(&value));
drbg->ctx = EVP_CIPHER_CTX_new();
S2N_ERROR_IF(!drbg->ctx, S2N_ERR_DRBG);
(void)EVP_CIPHER_CTX_init(drbg->ctx);
/* Start off with zeroed key, per 10.2.1.3.1 item 5 */
GUARD_OSSL(EVP_EncryptInit_ex(drbg->ctx, EVP_aes_128_ecb(), NULL, drbg->v, NULL), S2N_ERR_DRBG);
/* Copy the personalization string */
GUARD(s2n_blob_zero(&ps));
memcpy_check(ps.data, personalization_string->data, MIN(ps.size, personalization_string->size));
/* Seed / update the DRBG */
GUARD(s2n_drbg_seed(drbg, &ps));
/* After initial seeding, pivot to RDRAND if available and not overridden */
if (drbg->entropy_generator == NULL && s2n_cpu_supports_rdrand()) {
drbg->entropy_generator = s2n_get_rdrand_data;
}
return 0;
}
int s2n_drbg_generate(struct s2n_drbg *drbg, struct s2n_blob *blob)
{
uint8_t all_zeros[32] = { 0 };
struct s2n_blob zeros = {.data = all_zeros,.size = sizeof(all_zeros) };
S2N_ERROR_IF(blob->size > S2N_DRBG_GENERATE_LIMIT, S2N_ERR_DRBG_REQUEST_SIZE);
/* If either the entropy generator is set, for prediction resistance,
* or if we reach the definitely-need-to-reseed limit, then reseed.
*/
if (drbg->entropy_generator || drbg->bytes_used + blob->size + S2N_DRBG_BLOCK_SIZE >= S2N_DRBG_RESEED_LIMIT) {
GUARD(s2n_drbg_seed(drbg, &zeros));
}
GUARD(s2n_drbg_bits(drbg, blob));
GUARD(s2n_drbg_update(drbg, &zeros));
return 0;
}
int s2n_drbg_wipe(struct s2n_drbg *drbg)
{
struct s2n_blob state = {.data = (void *)drbg,.size = sizeof(struct s2n_drbg) };
if (drbg->ctx) {
GUARD_OSSL(EVP_CIPHER_CTX_cleanup(drbg->ctx), S2N_ERR_DRBG);
EVP_CIPHER_CTX_free(drbg->ctx);
drbg->ctx = NULL;
}
GUARD(s2n_blob_zero(&state));
return 0;
}
int s2n_drbg_bytes_used(struct s2n_drbg *drbg)
{
return drbg->bytes_used;
}
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 *out)
{
if (conn->actual_protocol_version == S2N_SSLv3) {
return s2n_sslv3_prf(&conn->prf_space, secret, seed_a, seed_b, out);
}
/* We zero the out blob because p_hash works by XOR'ing with the existing
* buffer. This is a little convuloted 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));
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, 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, 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, out));
return 0;
}
int s2n_prf_master_secret(struct s2n_connection *conn, struct s2n_blob *premaster_secret)
{
struct s2n_blob client_random, server_random, master_secret;
struct s2n_blob label;
uint8_t master_secret_label[] = "master secret";
client_random.data = conn->secure.client_random;
client_random.size = sizeof(conn->secure.client_random);
server_random.data = conn->secure.server_random;
server_random.size = sizeof(conn->secure.server_random);
master_secret.data = conn->secure.master_secret;
master_secret.size = sizeof(conn->secure.master_secret);
label.data = master_secret_label;
label.size = sizeof(master_secret_label) - 1;
return s2n_prf(conn, premaster_secret, &label, &client_random, &server_random, &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;
}
