tls: Do not set verify_data_length unless needed

All current TLS cipher suites use a verify_data_length of 12.  In fact,
according to RFC 5246, most cipher suites are expected to be 12 bytes
unless specified otherwise.  Use this fact to simplify the cipher suite
definition: initialization of verify_data_length is no longer necessary
unless the length is greater than 12 bytes.

While here, also update struct tls_cipher_suite to use a size_t member
for verify_data_length instead of an int.

3 files changed, 22 insertions, 35 deletions

diff --git a/ell/tls-private.h b/ell/tls-private.h
index 8ceeb68d..8941e90d 100644
--- a/ell/tls-private.h
+++ b/ell/tls-private.h
@@ -112,7 +112,7 @@ struct tls_mac_algorithm {
 struct tls_cipher_suite {
 	uint8_t id[2];
 	const char *name;
-	int verify_data_length;
+	size_t verify_data_length;
 
 	struct tls_bulk_encryption_algorithm *encryption;
 	struct tls_signature_algorithm *signature;
diff --git a/ell/tls-suites.c b/ell/tls-suites.c
index 34141ab7..ee4e7ee6 100644
--- a/ell/tls-suites.c
+++ b/ell/tls-suites.c
@@ -1262,7 +1262,6 @@ static struct tls_mac_algorithm tls_sha = {
 static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 	.id = { 0x00, 0x0a },
 	.name = "TLS_RSA_WITH_3DES_EDE_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_3des_ede,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1270,7 +1269,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_dhe_rsa_with_3des_ede_cbc_sha = {
 	.id = { 0x00, 0x16 },
 	.name = "TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_3des_ede,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1278,7 +1276,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_rsa_with_aes_128_cbc_sha = {
 	.id = { 0x00, 0x2f },
 	.name = "TLS_RSA_WITH_AES_128_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1286,7 +1283,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_dhe_rsa_with_aes_128_cbc_sha = {
 	.id = { 0x00, 0x33 },
 	.name = "TLS_DHE_RSA_WITH_AES_128_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1294,7 +1290,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_rsa_with_aes_256_cbc_sha = {
 	.id = { 0x00, 0x35 },
 	.name = "TLS_RSA_WITH_AES_256_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1302,7 +1297,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_dhe_rsa_with_aes_256_cbc_sha = {
 	.id = { 0x00, 0x39 },
 	.name = "TLS_DHE_RSA_WITH_AES_256_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1310,7 +1304,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_rsa_with_aes_128_cbc_sha256 = {
 	.id = { 0x00, 0x3c },
 	.name = "TLS_RSA_WITH_AES_128_CBC_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha256,
 	.signature = &tls_rsa_signature,
@@ -1318,7 +1311,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_rsa_with_aes_256_cbc_sha256 = {
 	.id = { 0x00, 0x3d },
 	.name = "TLS_RSA_WITH_AES_256_CBC_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha256,
 	.signature = &tls_rsa_signature,
@@ -1326,7 +1318,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_dhe_rsa_with_aes_128_cbc_sha256 = {
 	.id = { 0x00, 0x67 },
 	.name = "TLS_DHE_RSA_WITH_AES_128_CBC_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha256,
 	.signature = &tls_rsa_signature,
@@ -1334,7 +1325,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_dhe_rsa_with_aes_256_cbc_sha256 = {
 	.id = { 0x00, 0x6b },
 	.name = "TLS_DHE_RSA_WITH_AES_256_CBC_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha256,
 	.signature = &tls_rsa_signature,
@@ -1342,14 +1332,12 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_rsa_with_aes_128_gcm_sha256 = {
 	.id = { 0x00, 0x9c },
 	.name = "TLS_RSA_WITH_AES_128_GCM_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128_gcm,
 	.signature = &tls_rsa_signature,
 	.key_xchg = &tls_rsa_key_xchg,
 }, tls_rsa_with_aes_256_gcm_sha384 = {
 	.id = { 0x00, 0x9d },
 	.name = "TLS_RSA_WITH_AES_256_GCM_SHA384",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256_gcm,
 	.prf_hmac = L_CHECKSUM_SHA384,
 	.signature = &tls_rsa_signature,
@@ -1357,14 +1345,12 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_dhe_rsa_with_aes_128_gcm_sha256 = {
 	.id = { 0x00, 0x9e },
 	.name = "TLS_DHE_RSA_WITH_AES_128_GCM_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128_gcm,
 	.signature = &tls_rsa_signature,
 	.key_xchg = &tls_dhe,
 }, tls_dhe_rsa_with_aes_256_gcm_sha384 = {
 	.id = { 0x00, 0x9f },
 	.name = "TLS_DHE_RSA_WITH_AES_256_GCM_SHA384",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256_gcm,
 	.prf_hmac = L_CHECKSUM_SHA384,
 	.signature = &tls_rsa_signature,
@@ -1372,7 +1358,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_rsa_with_3des_ede_cbc_sha = {
 	.id = { 0xc0, 0x12 },
 	.name = "TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_3des_ede,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1380,7 +1365,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_rsa_with_aes_128_cbc_sha = {
 	.id = { 0xc0, 0x13 },
 	.name = "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1388,7 +1372,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_rsa_with_aes_256_cbc_sha = {
 	.id = { 0xc0, 0x14 },
 	.name = "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha,
 	.signature = &tls_rsa_signature,
@@ -1396,7 +1379,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_rsa_with_aes_128_cbc_sha256 = {
 	.id = { 0xc0, 0x27 },
 	.name = "TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha256,
 	.signature = &tls_rsa_signature,
@@ -1404,7 +1386,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_rsa_with_aes_256_cbc_sha384 = {
 	.id = { 0xc0, 0x28 },
 	.name = "TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha384,
 	.prf_hmac = L_CHECKSUM_SHA384,
@@ -1413,14 +1394,12 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_rsa_with_aes_128_gcm_sha256 = {
 	.id = { 0xc0, 0x2f },
 	.name = "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128_gcm,
 	.signature = &tls_rsa_signature,
 	.key_xchg = &tls_ecdhe,
 }, tls_ecdhe_rsa_with_aes_256_gcm_sha384 = {
 	.id = { 0xc0, 0x30 },
 	.name = "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256_gcm,
 	.prf_hmac = L_CHECKSUM_SHA384,
 	.signature = &tls_rsa_signature,
@@ -1428,7 +1407,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_ecdsa_with_3des_ede_cbc_sha = {
 	.id = { 0xc0, 0x08 },
 	.name = "TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_3des_ede,
 	.mac = &tls_sha,
 	.signature = &tls_ecdsa_signature,
@@ -1436,7 +1414,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_ecdsa_with_aes_128_cbc_sha = {
 	.id = { 0xc0, 0x09 },
 	.name = "TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128,
 	.mac = &tls_sha,
 	.signature = &tls_ecdsa_signature,
@@ -1444,7 +1421,6 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_ecdsa_with_aes_256_cbc_sha = {
 	.id = { 0xc0, 0x0a },
 	.name = "TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256,
 	.mac = &tls_sha,
 	.signature = &tls_ecdsa_signature,
@@ -1452,14 +1428,12 @@ static struct tls_cipher_suite tls_rsa_with_3des_ede_cbc_sha = {
 }, tls_ecdhe_ecdsa_with_aes_128_gcm_sha256 = {
 	.id = { 0xc0, 0x2b },
 	.name = "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
-	.verify_data_length = 12,
 	.encryption = &tls_aes128_gcm,
 	.signature = &tls_ecdsa_signature,
 	.key_xchg = &tls_ecdhe,
 }, tls_ecdhe_ecdsa_with_aes_256_gcm_sha384 = {
 	.id = { 0xc0, 0x2c },
 	.name = "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
-	.verify_data_length = 12,
 	.encryption = &tls_aes256_gcm,
 	.prf_hmac = L_CHECKSUM_SHA384,
 	.signature = &tls_ecdsa_signature,
diff --git a/ell/tls.c b/ell/tls.c
index 136aa866..fa3df5d3 100644
--- a/ell/tls.c
+++ b/ell/tls.c
@@ -1370,11 +1370,25 @@ static void tls_send_change_cipher_spec(struct l_tls *tls)
 	tls_tx_record(tls, TLS_CT_CHANGE_CIPHER_SPEC, &buf, 1);
 }
 
+static size_t tls_verify_data_length(struct l_tls *tls, unsigned int index)
+{
+	/*
+	 * RFC 5246, Section 7.4.9:
+	 *
+	 * In previous versions of TLS, the verify_data was always 12 octets
+	 * long.  In the current version of TLS, it depends on the cipher
+	 * suite.  Any cipher suite which does not explicitly specify
+	 * verify_data_length has a verify_data_length equal to 12.
+	 */
+	return maxsize(tls->cipher_suite[index]->verify_data_length, 12);
+}
+
 static void tls_send_finished(struct l_tls *tls)
 {
 	uint8_t buf[512];
 	uint8_t *ptr = buf + TLS_HANDSHAKE_HEADER_SIZE;
 	uint8_t seed[HANDSHAKE_HASH_MAX_SIZE * 2];
+	size_t vdl = tls_verify_data_length(tls, 1);
 	size_t seed_len;
 
 	if (tls->negotiated_version >= L_TLS_V12) {
@@ -1391,8 +1405,8 @@ static void tls_send_finished(struct l_tls *tls)
 				tls->server ? "server finished" :
 				"client finished",
 				seed, seed_len,
-				ptr, tls->cipher_suite[1]->verify_data_length);
-	ptr += tls->cipher_suite[1]->verify_data_length;
+				ptr, vdl);
+	ptr += vdl;
 
 	tls_tx_handshake(tls, TLS_FINISHED, buf, ptr - buf);
 }
@@ -1400,14 +1414,14 @@ static void tls_send_finished(struct l_tls *tls)
 static bool tls_verify_finished(struct l_tls *tls, const uint8_t *received,
 				size_t len)
 {
-	uint8_t expected[tls->cipher_suite[0]->verify_data_length];
+	size_t vdl = tls_verify_data_length(tls, 0);
+	uint8_t expected[vdl];
 	uint8_t *seed;
 	size_t seed_len;
 
-	if (len != (size_t) tls->cipher_suite[0]->verify_data_length) {
+	if (len != vdl) {
 		TLS_DISCONNECT(TLS_ALERT_DECODE_ERROR, 0,
-				"TLS_FINISHED length not %i",
-				tls->cipher_suite[0]->verify_data_length);
+				"TLS_FINISHED length not %zu", vdl);
 
 		return false;
 	}
@@ -1428,8 +1442,7 @@ static bool tls_verify_finished(struct l_tls *tls, const uint8_t *received,
 				tls->server ? "client finished" :
 				"server finished",
 				seed, seed_len,
-				expected,
-				tls->cipher_suite[0]->verify_data_length);
+				expected, vdl);
 
 	if (memcmp(received, expected, len)) {
 		TLS_DISCONNECT(TLS_ALERT_DECRYPT_ERROR, 0,