1 files changed, 18 insertions, 31 deletions

diff --git a/src/methods/generic_gcm/generic_gcm.c b/src/methods/generic_gcm/generic_gcm.c
index fc665dd..0817a57 100644
--- a/src/methods/generic_gcm/generic_gcm.c
+++ b/src/methods/generic_gcm/generic_gcm.c
@@ -156,8 +156,7 @@ static inline void put_size(fastd_block128_t *out, size_t len) {
 }
 
 static bool method_encrypt(fastd_context_t *ctx, fastd_peer_t *peer UNUSED, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in) {
-	fastd_buffer_pull_head(ctx, &in, sizeof(fastd_block128_t));
-	memset(in.data, 0, sizeof(fastd_block128_t));
+	fastd_buffer_pull_head_zero(ctx, &in, sizeof(fastd_block128_t));
 
 	size_t tail_len = alignto(in.len, sizeof(fastd_block128_t))-in.len;
 	*out = fastd_buffer_alloc(ctx, in.len, alignto(COMMON_HEADBYTES, 16), sizeof(fastd_block128_t)+tail_len);
@@ -165,17 +164,14 @@ static bool method_encrypt(fastd_context_t *ctx, fastd_peer_t *peer UNUSED, fast
 	if (tail_len)
 		memset(in.data+in.len, 0, tail_len);
 
-	size_t iv_length = session->method->cipher_info->iv_length;
-	uint8_t nonce[iv_length];
-	memset(nonce, 0, iv_length);
-	memcpy(nonce, session->common.send_nonce, COMMON_NONCEBYTES);
-	nonce[iv_length-1] = 1;
+	uint8_t nonce[session->method->cipher_info->iv_length];
+	fastd_method_expand_nonce(nonce, session->common.send_nonce, sizeof(nonce));
 
 	int n_blocks = block_count(in.len, sizeof(fastd_block128_t));
 
 	fastd_block128_t *inblocks = in.data;
 	fastd_block128_t *outblocks = out->data;
-	fastd_block128_t sig;
+	fastd_block128_t tag;
 
 	bool ok = session->cipher->crypt(session->cipher_state, outblocks, inblocks, n_blocks*sizeof(fastd_block128_t), nonce);
 
@@ -185,27 +181,21 @@ static bool method_encrypt(fastd_context_t *ctx, fastd_peer_t *peer UNUSED, fast
 
 		put_size(&outblocks[n_blocks], in.len-sizeof(fastd_block128_t));
 
-		ok = session->ghash->hash(session->ghash_state, &sig, outblocks+1, n_blocks);
+		ok = session->ghash->hash(session->ghash_state, &tag, outblocks+1, n_blocks);
 	}
 
 	if (!ok) {
-		/* restore original buffer */
-		fastd_buffer_push_head(ctx, &in, sizeof(fastd_block128_t));
 		fastd_buffer_free(*out);
 		return false;
 	}
 
-	xor_a(&outblocks[0], sig);
+	xor_a(&outblocks[0], tag);
 
 	fastd_buffer_free(in);
 
-	fastd_buffer_pull_head(ctx, out, COMMON_HEADBYTES);
-
-	memcpy(out->data, session->common.send_nonce, COMMON_NONCEBYTES);
+	fastd_method_put_common_header(ctx, out, session->common.send_nonce, 0);
 	fastd_method_increment_nonce(&session->common);
 
-	((uint8_t*)out->data)[COMMON_NONCEBYTES] = 0; /* flags */
-
 	return true;
 }
 
@@ -216,20 +206,17 @@ static bool method_decrypt(fastd_context_t *ctx, fastd_peer_t *peer, fastd_metho
 	if (!method_session_is_valid(ctx, session))
 		return false;
 
-	if (((const uint8_t*)in.data)[COMMON_NONCEBYTES]) /* flags */
+	uint8_t in_nonce[COMMON_NONCEBYTES];
+	uint8_t flags;
+	int64_t age;
+	if (!fastd_method_handle_common_header(ctx, &session->common, &in, in_nonce, &flags, &age))
 		return false;
 
-	size_t iv_length = session->method->cipher_info->iv_length;
-	uint8_t nonce[iv_length];
-	memset(nonce, 0, iv_length);
-	memcpy(nonce, in.data, COMMON_NONCEBYTES);
-	nonce[iv_length-1] = 1;
-
-	int64_t age;
-	if (!fastd_method_is_nonce_valid(ctx, &session->common, nonce, &age))
+	if (flags)
 		return false;
 
-	fastd_buffer_push_head(ctx, &in, COMMON_HEADBYTES);
+	uint8_t nonce[session->method->cipher_info->iv_length];
+	fastd_method_expand_nonce(nonce, in_nonce, sizeof(nonce));
 
 	size_t tail_len = alignto(in.len, sizeof(fastd_block128_t))-in.len;
 	*out = fastd_buffer_alloc(ctx, in.len, 0, tail_len);
@@ -238,7 +225,7 @@ static bool method_decrypt(fastd_context_t *ctx, fastd_peer_t *peer, fastd_metho
 
 	fastd_block128_t *inblocks = in.data;
 	fastd_block128_t *outblocks = out->data;
-	fastd_block128_t sig;
+	fastd_block128_t tag;
 
 	bool ok = session->cipher->crypt(session->cipher_state, outblocks, inblocks, n_blocks*sizeof(fastd_block128_t), nonce);
 
@@ -248,10 +235,10 @@ static bool method_decrypt(fastd_context_t *ctx, fastd_peer_t *peer, fastd_metho
 
 		put_size(&inblocks[n_blocks], in.len-sizeof(fastd_block128_t));
 
-		ok = session->ghash->hash(session->ghash_state, &sig, inblocks+1, n_blocks);
+		ok = session->ghash->hash(session->ghash_state, &tag, inblocks+1, n_blocks);
 	}
 
-	if (!ok || memcmp(&sig, &outblocks[0], sizeof(fastd_block128_t)) != 0) {
+	if (!ok || memcmp(&tag, &outblocks[0], sizeof(fastd_block128_t)) != 0) {
 		fastd_buffer_free(*out);
 		return false;
 	}
@@ -260,7 +247,7 @@ static bool method_decrypt(fastd_context_t *ctx, fastd_peer_t *peer, fastd_metho
 
 	fastd_buffer_push_head(ctx, out, sizeof(fastd_block128_t));
 
-	if (!fastd_method_reorder_check(ctx, peer, &session->common, nonce, age)) {
+	if (!fastd_method_reorder_check(ctx, peer, &session->common, in_nonce, age)) {
 		fastd_buffer_free(*out);
 		*out = fastd_buffer_alloc(ctx, 0, 0, 0);
 	}