int s2n_conn_update_handshake_hashes()

in tls/s2n_handshake_transcript.c [38:96]

• 37 lines of code
• 12 McCabe index (conditional complexity)

int s2n_conn_update_handshake_hashes(struct s2n_connection *conn, struct s2n_blob *data)
{
    POSIX_ENSURE_REF(conn);
    POSIX_ENSURE_REF(data);
    POSIX_ENSURE_REF(conn->handshake.hashes);

    if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_MD5)) {
        /* The handshake MD5 hash state will fail the s2n_hash_is_available() check
         * since MD5 is not permitted in FIPS mode. This check will not be used as
         * the handshake MD5 hash state is specifically used by the TLS 1.0 and TLS 1.1
         * PRF, which is required to comply with the TLS 1.0 and 1.1 RFCs and is approved
         * as per NIST Special Publication 800-52 Revision 1.
         */
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->md5, data->data, data->size));
    }

    if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA1)) {
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->sha1, data->data, data->size));
    }

    const uint8_t md5_sha1_required = (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_MD5) &&
                                       s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA1));

    if (md5_sha1_required) {
        /* The MD5_SHA1 hash can still be used for TLS 1.0 and 1.1 in FIPS mode for 
         * the handshake hashes. This will only be used for the signature check in the
         * CertificateVerify message and the PRF. NIST SP 800-52r1 approves use
         * of MD5_SHA1 for these use cases (see footnotes 15 and 20, and section
         * 3.3.2) */
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->md5_sha1, data->data, data->size));
    }

    if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA224)) {
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->sha224, data->data, data->size));
    }

    if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA256)) {
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->sha256, data->data, data->size));
    }

    if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA384)) {
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->sha384, data->data, data->size));
    }

    if (s2n_handshake_is_hash_required(&conn->handshake, S2N_HASH_SHA512)) {
        POSIX_GUARD(s2n_hash_update(&conn->handshake.hashes->sha512, data->data, data->size));
    }

    /* Copy hashes that TLS1.3 will need later. */
    if (s2n_connection_get_protocol_version(conn) >= S2N_TLS13) {
        if (s2n_conn_get_current_message_type(conn) == SERVER_HELLO) {
            POSIX_GUARD(s2n_tls13_conn_copy_hash(conn, &conn->handshake.hashes->server_hello_copy));
        } else if (s2n_conn_get_current_message_type(conn) == SERVER_FINISHED) {
            POSIX_GUARD(s2n_tls13_conn_copy_hash(conn, &conn->handshake.hashes->server_finished_copy));
        }
    }

    return S2N_SUCCESS;
}