X-Git-Url: https://www.tinc-vpn.org/git/browse?a=blobdiff_plain;f=src%2Fsptps.c;h=eeaf833ece81de30f3b5f3ed5d5b2ca4ded11456;hb=refs%2Fheads%2F1.1;hp=7bd271b936ba2591d39a926762d8a5b8d6870977;hpb=dece2db78e2c4ccd6e617e69195754639b086170;p=tinc

diff --git a/src/sptps.c b/src/sptps.c
index 7bd271b9..35c68bc9 100644
--- a/src/sptps.c
+++ b/src/sptps.c
@@ -21,12 +21,12 @@
 #include "system.h"
 
 #include "chacha-poly1305/chacha-poly1305.h"
-#include "crypto.h"
 #include "ecdh.h"
 #include "ecdsa.h"
-#include "logger.h"
 #include "prf.h"
 #include "sptps.h"
+#include "random.h"
+#include "xalloc.h"
 
 unsigned int sptps_replaywin = 16;
 
@@ -51,9 +51,16 @@ unsigned int sptps_replaywin = 16;
 */
 
 void sptps_log_quiet(sptps_t *s, int s_errno, const char *format, va_list ap) {
+	(void)s;
+	(void)s_errno;
+	(void)format;
+	(void)ap;
 }
 
 void sptps_log_stderr(sptps_t *s, int s_errno, const char *format, va_list ap) {
+	(void)s;
+	(void)s_errno;
+
 	vfprintf(stderr, format, ap);
 	fputc('\n', stderr);
 }
@@ -61,7 +68,11 @@ void sptps_log_stderr(sptps_t *s, int s_errno, const char *format, va_list ap) {
 void (*sptps_log)(sptps_t *s, int s_errno, const char *format, va_list ap) = sptps_log_stderr;
 
 // Log an error message.
+static bool error(sptps_t *s, int s_errno, const char *format, ...) ATTR_FORMAT(printf, 3, 4);
 static bool error(sptps_t *s, int s_errno, const char *format, ...) {
+	(void)s;
+	(void)s_errno;
+
 	if(format) {
 		va_list ap;
 		va_start(ap, format);
@@ -73,6 +84,7 @@ static bool error(sptps_t *s, int s_errno, const char *format, ...) {
 	return false;
 }
 
+static void warning(sptps_t *s, const char *format, ...) ATTR_FORMAT(printf, 2, 3);
 static void warning(sptps_t *s, const char *format, ...) {
 	va_list ap;
 	va_start(ap, format);
@@ -80,9 +92,25 @@ static void warning(sptps_t *s, const char *format, ...) {
 	va_end(ap);
 }
 
+static sptps_kex_t *new_sptps_kex(void) {
+	return xzalloc(sizeof(sptps_kex_t));
+}
+
+static void free_sptps_kex(sptps_kex_t *kex) {
+	xzfree(kex, sizeof(sptps_kex_t));
+}
+
+static sptps_key_t *new_sptps_key(void) {
+	return xzalloc(sizeof(sptps_key_t));
+}
+
+static void free_sptps_key(sptps_key_t *key) {
+	xzfree(key, sizeof(sptps_key_t));
+}
+
 // Send a record (datagram version, accepts all record types, handles encryption and authentication).
 static bool send_record_priv_datagram(sptps_t *s, uint8_t type, const void *data, uint16_t len) {
-	char buffer[len + 21UL];
+	uint8_t *buffer = alloca(len + 21UL);
 
 	// Create header with sequence number, length and record type
 	uint32_t seqno = s->outseqno++;
@@ -103,10 +131,11 @@ static bool send_record_priv_datagram(sptps_t *s, uint8_t type, const void *data
 }
 // Send a record (private version, accepts all record types, handles encryption and authentication).
 static bool send_record_priv(sptps_t *s, uint8_t type, const void *data, uint16_t len) {
-	if(s->datagram)
+	if(s->datagram) {
 		return send_record_priv_datagram(s, type, data, len);
+	}
 
-	char buffer[len + 19UL];
+	uint8_t *buffer = alloca(len + 19UL);
 
 	// Create header with sequence number, length and record type
 	uint32_t seqno = s->outseqno++;
@@ -130,93 +159,106 @@ static bool send_record_priv(sptps_t *s, uint8_t type, const void *data, uint16_
 bool sptps_send_record(sptps_t *s, uint8_t type, const void *data, uint16_t len) {
 	// Sanity checks: application cannot send data before handshake is finished,
 	// and only record types 0..127 are allowed.
-	if(!s->outstate)
+	if(!s->outstate) {
 		return error(s, EINVAL, "Handshake phase not finished yet");
+	}
 
-	if(type >= SPTPS_HANDSHAKE)
+	if(type >= SPTPS_HANDSHAKE) {
 		return error(s, EINVAL, "Invalid application record type");
+	}
 
 	return send_record_priv(s, type, data, len);
 }
 
 // Send a Key EXchange record, containing a random nonce and an ECDHE public key.
 static bool send_kex(sptps_t *s) {
-	size_t keylen = ECDH_SIZE;
-
 	// Make room for our KEX message, which we will keep around since send_sig() needs it.
-	if(s->mykex)
+	if(s->mykex) {
 		return false;
-	s->mykex = realloc(s->mykex, 1 + 32 + keylen);
-	if(!s->mykex)
-		return error(s, errno, strerror(errno));
+	}
+
+	s->mykex = new_sptps_kex();
 
 	// Set version byte to zero.
-	s->mykex[0] = SPTPS_VERSION;
+	s->mykex->version = SPTPS_VERSION;
 
 	// Create a random nonce.
-	randomize(s->mykex + 1, 32);
+	randomize(s->mykex->nonce, ECDH_SIZE);
 
 	// Create a new ECDH public key.
-	if(!(s->ecdh = ecdh_generate_public(s->mykex + 1 + 32)))
+	if(!(s->ecdh = ecdh_generate_public(s->mykex->pubkey))) {
 		return error(s, EINVAL, "Failed to generate ECDH public key");
+	}
 
-	return send_record_priv(s, SPTPS_HANDSHAKE, s->mykex, 1 + 32 + keylen);
+	return send_record_priv(s, SPTPS_HANDSHAKE, s->mykex, sizeof(sptps_kex_t));
+}
+
+static size_t sigmsg_len(size_t labellen) {
+	return 1 + 2 * sizeof(sptps_kex_t) + labellen;
+}
+
+static void fill_msg(uint8_t *msg, bool initiator, const sptps_kex_t *kex0, const sptps_kex_t *kex1, const sptps_t *s) {
+	*msg = initiator, msg++;
+	memcpy(msg, kex0, sizeof(*kex0)), msg += sizeof(*kex0);
+	memcpy(msg, kex1, sizeof(*kex1)), msg += sizeof(*kex1);
+	memcpy(msg, s->label, s->labellen);
 }
 
 // Send a SIGnature record, containing an Ed25519 signature over both KEX records.
 static bool send_sig(sptps_t *s) {
-	size_t keylen = ECDH_SIZE;
-	size_t siglen = ecdsa_size(s->mykey);
-
 	// Concatenate both KEX messages, plus tag indicating if it is from the connection originator, plus label
-	char msg[(1 + 32 + keylen) * 2 + 1 + s->labellen];
-	char sig[siglen];
-
-	msg[0] = s->initiator;
-	memcpy(msg + 1, s->mykex, 1 + 32 + keylen);
-	memcpy(msg + 1 + 33 + keylen, s->hiskex, 1 + 32 + keylen);
-	memcpy(msg + 1 + 2 * (33 + keylen), s->label, s->labellen);
+	size_t msglen = sigmsg_len(s->labellen);
+	uint8_t *msg = alloca(msglen);
+	fill_msg(msg, s->initiator, s->mykex, s->hiskex, s);
 
 	// Sign the result.
-	if(!ecdsa_sign(s->mykey, msg, sizeof msg, sig))
+	size_t siglen = ecdsa_size(s->mykey);
+	uint8_t *sig = alloca(siglen);
+
+	if(!ecdsa_sign(s->mykey, msg, msglen, sig)) {
 		return error(s, EINVAL, "Failed to sign SIG record");
+	}
 
 	// Send the SIG exchange record.
-	return send_record_priv(s, SPTPS_HANDSHAKE, sig, sizeof sig);
+	return send_record_priv(s, SPTPS_HANDSHAKE, sig, siglen);
 }
 
 // Generate key material from the shared secret created from the ECDHE key exchange.
-static bool generate_key_material(sptps_t *s, const char *shared, size_t len) {
+static bool generate_key_material(sptps_t *s, const uint8_t *shared, size_t len) {
 	// Initialise cipher and digest structures if necessary
 	if(!s->outstate) {
 		s->incipher = chacha_poly1305_init();
 		s->outcipher = chacha_poly1305_init();
-		if(!s->incipher || !s->outcipher)
+
+		if(!s->incipher || !s->outcipher) {
 			return error(s, EINVAL, "Failed to open cipher");
+		}
 	}
 
 	// Allocate memory for key material
-	size_t keylen = 2 * CHACHA_POLY1305_KEYLEN;
-
-	s->key = realloc(s->key, keylen);
-	if(!s->key)
-		return error(s, errno, strerror(errno));
+	s->key = new_sptps_key();
 
 	// Create the HMAC seed, which is "key expansion" + session label + server nonce + client nonce
-	char seed[s->labellen + 64 + 13];
-	strcpy(seed, "key expansion");
-	if(s->initiator) {
-		memcpy(seed + 13, s->mykex + 1, 32);
-		memcpy(seed + 45, s->hiskex + 1, 32);
-	} else {
-		memcpy(seed + 13, s->hiskex + 1, 32);
-		memcpy(seed + 45, s->mykex + 1, 32);
-	}
-	memcpy(seed + 77, s->label, s->labellen);
+	const size_t msglen = sizeof("key expansion") - 1;
+	const size_t seedlen = msglen + s->labellen + ECDH_SIZE * 2;
+	uint8_t *seed = alloca(seedlen);
+
+	uint8_t *ptr = seed;
+	memcpy(ptr, "key expansion", msglen);
+	ptr += msglen;
+
+	memcpy(ptr, (s->initiator ? s->mykex : s->hiskex)->nonce, ECDH_SIZE);
+	ptr += ECDH_SIZE;
+
+	memcpy(ptr, (s->initiator ? s->hiskex : s->mykex)->nonce, ECDH_SIZE);
+	ptr += ECDH_SIZE;
+
+	memcpy(ptr, s->label, s->labellen);
 
 	// Use PRF to generate the key material
-	if(!prf(shared, len, seed, s->labellen + 64 + 13, s->key, keylen))
+	if(!prf(shared, len, seed, seedlen, s->key->both, sizeof(sptps_key_t))) {
 		return error(s, EINVAL, "Failed to generate key material");
+	}
 
 	return true;
 }
@@ -227,19 +269,20 @@ static bool send_ack(sptps_t *s) {
 }
 
 // Receive an ACKnowledgement record.
-static bool receive_ack(sptps_t *s, const char *data, uint16_t len) {
-	if(len)
+static bool receive_ack(sptps_t *s, const uint8_t *data, uint16_t len) {
+	(void)data;
+
+	if(len) {
 		return error(s, EIO, "Invalid ACK record length");
+	}
 
-	if(s->initiator) {
-		if(!chacha_poly1305_set_key(s->incipher, s->key))
-			return error(s, EINVAL, "Failed to set counter");
-	} else {
-		if(!chacha_poly1305_set_key(s->incipher, s->key + CHACHA_POLY1305_KEYLEN))
-			return error(s, EINVAL, "Failed to set counter");
+	uint8_t *key = s->initiator ? s->key->key0 : s->key->key1;
+
+	if(!chacha_poly1305_set_key(s->incipher, key)) {
+		return error(s, EINVAL, "Failed to set counter");
 	}
 
-	free(s->key);
+	free_sptps_key(s->key);
 	s->key = NULL;
 	s->instate = true;
 
@@ -247,73 +290,86 @@ static bool receive_ack(sptps_t *s, const char *data, uint16_t len) {
 }
 
 // Receive a Key EXchange record, respond by sending a SIG record.
-static bool receive_kex(sptps_t *s, const char *data, uint16_t len) {
+static bool receive_kex(sptps_t *s, const uint8_t *data, uint16_t len) {
 	// Verify length of the HELLO record
-	if(len != 1 + 32 + ECDH_SIZE)
+	if(len != sizeof(sptps_kex_t)) {
 		return error(s, EIO, "Invalid KEX record length");
+	}
 
-	// Ignore version number for now.
+	if(*data != SPTPS_VERSION) {
+		return error(s, EINVAL, "Received incorrect version %d", *data);
+	}
 
 	// Make a copy of the KEX message, send_sig() and receive_sig() need it
-	if(s->hiskex)
+	if(s->hiskex) {
 		return error(s, EINVAL, "Received a second KEX message before first has been processed");
-	s->hiskex = realloc(s->hiskex, len);
-	if(!s->hiskex)
-		return error(s, errno, strerror(errno));
+	}
 
-	memcpy(s->hiskex, data, len);
+	s->hiskex = new_sptps_kex();
+	memcpy(s->hiskex, data, sizeof(sptps_kex_t));
 
-	return send_sig(s);
+	if(s->initiator) {
+		return send_sig(s);
+	} else {
+		return true;
+	}
 }
 
 // Receive a SIGnature record, verify it, if it passed, compute the shared secret and calculate the session keys.
-static bool receive_sig(sptps_t *s, const char *data, uint16_t len) {
-	size_t keylen = ECDH_SIZE;
-	size_t siglen = ecdsa_size(s->hiskey);
-
+static bool receive_sig(sptps_t *s, const uint8_t *data, uint16_t len) {
 	// Verify length of KEX record.
-	if(len != siglen)
+	if(len != ecdsa_size(s->hiskey)) {
 		return error(s, EIO, "Invalid KEX record length");
+	}
 
 	// Concatenate both KEX messages, plus tag indicating if it is from the connection originator
-	char msg[(1 + 32 + keylen) * 2 + 1 + s->labellen];
-
-	msg[0] = !s->initiator;
-	memcpy(msg + 1, s->hiskex, 1 + 32 + keylen);
-	memcpy(msg + 1 + 33 + keylen, s->mykex, 1 + 32 + keylen);
-	memcpy(msg + 1 + 2 * (33 + keylen), s->label, s->labellen);
+	const size_t msglen = sigmsg_len(s->labellen);
+	uint8_t *msg = alloca(msglen);
+	fill_msg(msg, !s->initiator, s->hiskex, s->mykex, s);
 
 	// Verify signature.
-	if(!ecdsa_verify(s->hiskey, msg, sizeof msg, data))
+	if(!ecdsa_verify(s->hiskey, msg, msglen, data)) {
 		return error(s, EIO, "Failed to verify SIG record");
+	}
 
 	// Compute shared secret.
-	char shared[ECDH_SHARED_SIZE];
-	if(!ecdh_compute_shared(s->ecdh, s->hiskex + 1 + 32, shared))
+	uint8_t shared[ECDH_SHARED_SIZE];
+
+	if(!ecdh_compute_shared(s->ecdh, s->hiskex->pubkey, shared)) {
+		memzero(shared, sizeof(shared));
 		return error(s, EINVAL, "Failed to compute ECDH shared secret");
+	}
+
 	s->ecdh = NULL;
 
 	// Generate key material from shared secret.
-	if(!generate_key_material(s, shared, sizeof shared))
+	bool generated = generate_key_material(s, shared, sizeof(shared));
+	memzero(shared, sizeof(shared));
+
+	if(!generated) {
 		return false;
+	}
 
-	free(s->mykex);
-	free(s->hiskex);
+	if(!s->initiator && !send_sig(s)) {
+		return false;
+	}
 
+	free_sptps_kex(s->mykex);
 	s->mykex = NULL;
+
+	free_sptps_kex(s->hiskex);
 	s->hiskex = NULL;
 
 	// Send cipher change record
-	if(s->outstate && !send_ack(s))
+	if(s->outstate && !send_ack(s)) {
 		return false;
+	}
 
 	// TODO: only set new keys after ACK has been set/received
-	if(s->initiator) {
-		if(!chacha_poly1305_set_key(s->outcipher, s->key + CHACHA_POLY1305_KEYLEN))
-			return error(s, EINVAL, "Failed to set key");
-	} else {
-		if(!chacha_poly1305_set_key(s->outcipher, s->key))
-			return error(s, EINVAL, "Failed to set key");
+	uint8_t *key = s->initiator ? s->key->key1 : s->key->key0;
+
+	if(!chacha_poly1305_set_key(s->outcipher, key)) {
+		return error(s, EINVAL, "Failed to set key");
 	}
 
 	return true;
@@ -321,52 +377,72 @@ static bool receive_sig(sptps_t *s, const char *data, uint16_t len) {
 
 // Force another Key EXchange (for testing purposes).
 bool sptps_force_kex(sptps_t *s) {
-	if(!s->outstate || s->state != SPTPS_SECONDARY_KEX)
+	if(!s->outstate || s->state != SPTPS_SECONDARY_KEX) {
 		return error(s, EINVAL, "Cannot force KEX in current state");
+	}
 
 	s->state = SPTPS_KEX;
 	return send_kex(s);
 }
 
 // Receive a handshake record.
-static bool receive_handshake(sptps_t *s, const char *data, uint16_t len) {
+static bool receive_handshake(sptps_t *s, const uint8_t *data, uint16_t len) {
 	// Only a few states to deal with handshaking.
 	switch(s->state) {
-		case SPTPS_SECONDARY_KEX:
-			// We receive a secondary KEX request, first respond by sending our own.
-			if(!send_kex(s))
-				return false;
-		case SPTPS_KEX:
-			// We have sent our KEX request, we expect our peer to sent one as well.
-			if(!receive_kex(s, data, len))
-				return false;
-			s->state = SPTPS_SIG;
-			return true;
-		case SPTPS_SIG:
-			// If we already sent our secondary public ECDH key, we expect the peer to send his.
-			if(!receive_sig(s, data, len))
+	case SPTPS_SECONDARY_KEX:
+
+		// We receive a secondary KEX request, first respond by sending our own.
+		if(!send_kex(s)) {
+			return false;
+		}
+
+	// Fall through
+	case SPTPS_KEX:
+
+		// We have sent our KEX request, we expect our peer to sent one as well.
+		if(!receive_kex(s, data, len)) {
+			return false;
+		}
+
+		s->state = SPTPS_SIG;
+		return true;
+
+	case SPTPS_SIG:
+
+		// If we already sent our secondary public ECDH key, we expect the peer to send his.
+		if(!receive_sig(s, data, len)) {
+			return false;
+		}
+
+		if(s->outstate) {
+			s->state = SPTPS_ACK;
+		} else {
+			s->outstate = true;
+
+			if(!receive_ack(s, NULL, 0)) {
 				return false;
-			if(s->outstate)
-				s->state = SPTPS_ACK;
-			else {
-				s->outstate = true;
-				if(!receive_ack(s, NULL, 0))
-					return false;
-				s->receive_record(s->handle, SPTPS_HANDSHAKE, NULL, 0);
-				s->state = SPTPS_SECONDARY_KEX;
 			}
 
-			return true;
-		case SPTPS_ACK:
-			// We expect a handshake message to indicate transition to the new keys.
-			if(!receive_ack(s, data, len))
-				return false;
 			s->receive_record(s->handle, SPTPS_HANDSHAKE, NULL, 0);
 			s->state = SPTPS_SECONDARY_KEX;
-			return true;
-		// TODO: split ACK into a VERify and ACK?
-		default:
-			return error(s, EIO, "Invalid session state %d", s->state);
+		}
+
+		return true;
+
+	case SPTPS_ACK:
+
+		// We expect a handshake message to indicate transition to the new keys.
+		if(!receive_ack(s, data, len)) {
+			return false;
+		}
+
+		s->receive_record(s->handle, SPTPS_HANDSHAKE, NULL, 0);
+		s->state = SPTPS_SECONDARY_KEX;
+		return true;
+
+	// TODO: split ACK into a VERify and ACK?
+	default:
+		return error(s, EIO, "Invalid session state %d", s->state);
 	}
 }
 
@@ -381,98 +457,120 @@ static bool sptps_check_seqno(sptps_t *s, uint32_t seqno, bool update_state) {
 			if(seqno >= s->inseqno + s->replaywin * 8) {
 				// Prevent packets that jump far ahead of the queue from causing many others to be dropped.
 				bool farfuture = s->farfuture < s->replaywin >> 2;
-				if (update_state)
+
+				if(update_state) {
 					s->farfuture++;
-				if(farfuture)
+				}
+
+				if(farfuture) {
 					return update_state ? error(s, EIO, "Packet is %d seqs in the future, dropped (%u)\n", seqno - s->inseqno, s->farfuture) : false;
+				}
 
 				// Unless we have seen lots of them, in which case we consider the others lost.
-				if(update_state)
+				if(update_state) {
 					warning(s, "Lost %d packets\n", seqno - s->inseqno);
-				if (update_state) {
+				}
+
+				if(update_state) {
 					// Mark all packets in the replay window as being late.
 					memset(s->late, 255, s->replaywin);
 				}
-			} else if (seqno < s->inseqno) {
+			} else if(seqno < s->inseqno) {
 				// If the sequence number is farther in the past than the bitmap goes, or if the packet was already received, drop it.
-				if((s->inseqno >= s->replaywin * 8 && seqno < s->inseqno - s->replaywin * 8) || !(s->late[(seqno / 8) % s->replaywin] & (1 << seqno % 8)))
+				if((s->inseqno >= s->replaywin * 8 && seqno < s->inseqno - s->replaywin * 8) || !(s->late[(seqno / 8) % s->replaywin] & (1 << seqno % 8))) {
 					return update_state ? error(s, EIO, "Received late or replayed packet, seqno %d, last received %d\n", seqno, s->inseqno) : false;
-			} else if (update_state) {
+				}
+			} else if(update_state) {
 				// We missed some packets. Mark them in the bitmap as being late.
-				for(int i = s->inseqno; i < seqno; i++)
+				for(uint32_t i = s->inseqno; i < seqno; i++) {
 					s->late[(i / 8) % s->replaywin] |= 1 << i % 8;
+				}
 			}
 		}
 
-		if (update_state) {
+		if(update_state) {
 			// Mark the current packet as not being late.
 			s->late[(seqno / 8) % s->replaywin] &= ~(1 << seqno % 8);
 			s->farfuture = 0;
 		}
 	}
 
-	if (update_state) {
-		if(seqno >= s->inseqno)
+	if(update_state) {
+		if(seqno >= s->inseqno) {
 			s->inseqno = seqno + 1;
+		}
 
-		if(!s->inseqno)
+		if(!s->inseqno) {
 			s->received = 0;
-		else
+		} else {
 			s->received++;
+		}
 	}
 
 	return true;
 }
 
 // Check datagram for valid HMAC
-bool sptps_verify_datagram(sptps_t *s, const void *data, size_t len) {
-	if(!s->instate || len < 21)
+bool sptps_verify_datagram(sptps_t *s, const void *vdata, size_t len) {
+	if(!s->instate || len < 21) {
 		return error(s, EIO, "Received short packet");
+	}
 
+	const uint8_t *data = vdata;
 	uint32_t seqno;
 	memcpy(&seqno, data, 4);
 	seqno = ntohl(seqno);
-	if (!sptps_check_seqno(s, seqno, false))
+
+	if(!sptps_check_seqno(s, seqno, false)) {
 		return false;
+	}
 
-	char buffer[len];
+	uint8_t *buffer = alloca(len);
 	size_t outlen;
 	return chacha_poly1305_decrypt(s->incipher, seqno, data + 4, len - 4, buffer, &outlen);
 }
 
 // Receive incoming data, datagram version.
-static bool sptps_receive_data_datagram(sptps_t *s, const char *data, size_t len) {
-	if(len < (s->instate ? 21 : 5))
+static bool sptps_receive_data_datagram(sptps_t *s, const uint8_t *data, size_t len) {
+	if(len < (s->instate ? 21 : 5)) {
 		return error(s, EIO, "Received short packet");
+	}
 
 	uint32_t seqno;
 	memcpy(&seqno, data, 4);
 	seqno = ntohl(seqno);
-	data += 4; len -= 4;
+	data += 4;
+	len -= 4;
 
 	if(!s->instate) {
-		if(seqno != s->inseqno)
+		if(seqno != s->inseqno) {
 			return error(s, EIO, "Invalid packet seqno: %d != %d", seqno, s->inseqno);
+		}
 
 		s->inseqno = seqno + 1;
 
-		uint8_t type = *(data++); len--;
+		uint8_t type = *(data++);
+		len--;
 
-		if(type != SPTPS_HANDSHAKE)
+		if(type != SPTPS_HANDSHAKE) {
 			return error(s, EIO, "Application record received before handshake finished");
+		}
 
 		return receive_handshake(s, data, len);
 	}
 
 	// Decrypt
 
-	char buffer[len];
+	uint8_t *buffer = alloca(len);
 	size_t outlen;
-	if(!chacha_poly1305_decrypt(s->incipher, seqno, data, len, buffer, &outlen))
+
+	if(!chacha_poly1305_decrypt(s->incipher, seqno, data, len, buffer, &outlen)) {
 		return error(s, EIO, "Failed to decrypt and verify packet");
+	}
 
-	if(!sptps_check_seqno(s, seqno, true))
+	if(!sptps_check_seqno(s, seqno, true)) {
 		return false;
+	}
 
 	// Append a NULL byte for safety.
 	buffer[outlen] = 0;
@@ -480,16 +578,21 @@ static bool sptps_receive_data_datagram(sptps_t *s, const char *data, size_t len
 	data = buffer;
 	len = outlen;
 
-	uint8_t type = *(data++); len--;
+	uint8_t type = *(data++);
+	len--;
 
 	if(type < SPTPS_HANDSHAKE) {
-		if(!s->instate)
+		if(!s->instate) {
 			return error(s, EIO, "Application record received before handshake finished");
-		if(!s->receive_record(s->handle, type, data, len))
+		}
+
+		if(!s->receive_record(s->handle, type, data, len)) {
 			return false;
+		}
 	} else if(type == SPTPS_HANDSHAKE) {
-		if(!receive_handshake(s, data, len))
+		if(!receive_handshake(s, data, len)) {
 			return false;
+		}
 	} else {
 		return error(s, EIO, "Invalid record type %d", type);
 	}
@@ -498,20 +601,25 @@ static bool sptps_receive_data_datagram(sptps_t *s, const char *data, size_t len
 }
 
 // Receive incoming data. Check if it contains a complete record, if so, handle it.
-size_t sptps_receive_data(sptps_t *s, const void *data, size_t len) {
+size_t sptps_receive_data(sptps_t *s, const void *vdata, size_t len) {
+	const uint8_t *data = vdata;
 	size_t total_read = 0;
 
-	if(!s->state)
+	if(!s->state) {
 		return error(s, EIO, "Invalid session state zero");
+	}
 
-	if(s->datagram)
+	if(s->datagram) {
 		return sptps_receive_data_datagram(s, data, len) ? len : false;
+	}
 
 	// First read the 2 length bytes.
 	if(s->buflen < 2) {
 		size_t toread = 2 - s->buflen;
-		if(toread > len)
+
+		if(toread > len) {
 			toread = len;
+		}
 
 		memcpy(s->inbuf + s->buflen, data, toread);
 
@@ -521,8 +629,9 @@ size_t sptps_receive_data(sptps_t *s, const void *data, size_t len) {
 		data += toread;
 
 		// Exit early if we don't have the full length.
-		if(s->buflen < 2)
+		if(s->buflen < 2) {
 			return total_read;
+		}
 
 		// Get the length bytes
 
@@ -531,28 +640,32 @@ size_t sptps_receive_data(sptps_t *s, const void *data, size_t len) {
 
 		// If we have the length bytes, ensure our buffer can hold the whole request.
 		s->inbuf = realloc(s->inbuf, s->reclen + 19UL);
-		if(!s->inbuf)
-			return error(s, errno, strerror(errno));
+
+		if(!s->inbuf) {
+			return error(s, errno, "%s", strerror(errno));
+		}
 
 		// Exit early if we have no more data to process.
-		if(!len)
+		if(!len) {
 			return total_read;
+		}
 	}
 
 	// Read up to the end of the record.
 	size_t toread = s->reclen + (s->instate ? 19UL : 3UL) - s->buflen;
-	if(toread > len)
+
+	if(toread > len) {
 		toread = len;
+	}
 
 	memcpy(s->inbuf + s->buflen, data, toread);
 	total_read += toread;
 	s->buflen += toread;
-	len -= toread;
-	data += toread;
 
 	// If we don't have a whole record, exit.
-	if(s->buflen < s->reclen + (s->instate ? 19UL : 3UL))
+	if(s->buflen < s->reclen + (s->instate ? 19UL : 3UL)) {
 		return total_read;
+	}
 
 	// Update sequence number.
 
@@ -560,8 +673,9 @@ size_t sptps_receive_data(sptps_t *s, const void *data, size_t len) {
 
 	// Check HMAC and decrypt.
 	if(s->instate) {
-		if(!chacha_poly1305_decrypt(s->incipher, seqno, s->inbuf + 2UL, s->reclen + 17UL, s->inbuf + 2UL, NULL))
+		if(!chacha_poly1305_decrypt(s->incipher, seqno, s->inbuf + 2UL, s->reclen + 17UL, s->inbuf + 2UL, NULL)) {
 			return error(s, EINVAL, "Failed to decrypt and verify record");
+		}
 	}
 
 	// Append a NULL byte for safety.
@@ -570,13 +684,17 @@ size_t sptps_receive_data(sptps_t *s, const void *data, size_t len) {
 	uint8_t type = s->inbuf[2];
 
 	if(type < SPTPS_HANDSHAKE) {
-		if(!s->instate)
+		if(!s->instate) {
 			return error(s, EIO, "Application record received before handshake finished");
-		if(!s->receive_record(s->handle, type, s->inbuf + 3, s->reclen))
+		}
+
+		if(!s->receive_record(s->handle, type, s->inbuf + 3, s->reclen)) {
 			return false;
+		}
 	} else if(type == SPTPS_HANDSHAKE) {
-		if(!receive_handshake(s, s->inbuf + 3, s->reclen))
+		if(!receive_handshake(s, s->inbuf + 3, s->reclen)) {
 			return false;
+		}
 	} else {
 		return error(s, EIO, "Invalid record type %d", type);
 	}
@@ -589,7 +707,7 @@ size_t sptps_receive_data(sptps_t *s, const void *data, size_t len) {
 // Start a SPTPS session.
 bool sptps_start(sptps_t *s, void *handle, bool initiator, bool datagram, ecdsa_t *mykey, ecdsa_t *hiskey, const void *label, size_t labellen, send_data_t send_data, receive_record_t receive_record) {
 	// Initialise struct sptps
-	memset(s, 0, sizeof *s);
+	memset(s, 0, sizeof(*s));
 
 	s->handle = handle;
 	s->initiator = initiator;
@@ -597,21 +715,30 @@ bool sptps_start(sptps_t *s, void *handle, bool initiator, bool datagram, ecdsa_
 	s->mykey = mykey;
 	s->hiskey = hiskey;
 	s->replaywin = sptps_replaywin;
+
 	if(s->replaywin) {
 		s->late = malloc(s->replaywin);
-		if(!s->late)
-			return error(s, errno, strerror(errno));
+
+		if(!s->late) {
+			return error(s, errno, "%s", strerror(errno));
+		}
+
 		memset(s->late, 0, s->replaywin);
 	}
 
 	s->label = malloc(labellen);
-	if(!s->label)
-		return error(s, errno, strerror(errno));
+
+	if(!s->label) {
+		return error(s, errno, "%s", strerror(errno));
+	}
 
 	if(!datagram) {
 		s->inbuf = malloc(7);
-		if(!s->inbuf)
-			return error(s, errno, strerror(errno));
+
+		if(!s->inbuf) {
+			return error(s, errno, "%s", strerror(errno));
+		}
+
 		s->buflen = 0;
 	}
 
@@ -633,11 +760,11 @@ bool sptps_stop(sptps_t *s) {
 	chacha_poly1305_exit(s->outcipher);
 	ecdh_free(s->ecdh);
 	free(s->inbuf);
-	free(s->mykex);
-	free(s->hiskex);
-	free(s->key);
+	free_sptps_kex(s->mykex);
+	free_sptps_kex(s->hiskex);
+	free_sptps_key(s->key);
 	free(s->label);
 	free(s->late);
-	memset(s, 0, sizeof *s);
+	memset(s, 0, sizeof(*s));
 	return true;
 }