X-Git-Url: https://tinc-vpn.org/git/browse?p=tinc;a=blobdiff_plain;f=src%2Fprotocol_key.c;h=c392a469846e3878a53a65b84a110f43698df02e;hp=f52e8961b9b8fb250954c1db6888f48c6299966d;hb=3fba80174dbe29bcfe0d121a2a1d2e61be5ee57b;hpb=8dfa072733feab737cabf69f000c70657719826a

diff --git a/src/protocol_key.c b/src/protocol_key.c
index f52e8961..c392a469 100644
--- a/src/protocol_key.c
+++ b/src/protocol_key.c
@@ -29,6 +29,7 @@
 #include "net.h"
 #include "netutl.h"
 #include "node.h"
+#include "prf.h"
 #include "protocol.h"
 #include "utils.h"
 #include "xalloc.h"
@@ -39,7 +40,7 @@ void send_key_changed(void) {
 	splay_node_t *node;
 	connection_t *c;
 
-	send_request(broadcast, "%d %x %s", KEY_CHANGED, rand(), myself->name);
+	send_request(everyone, "%d %x %s", KEY_CHANGED, rand(), myself->name);
 
 	/* Immediately send new keys to directly connected nodes to keep UDP mappings alive */
 
@@ -83,7 +84,7 @@ bool key_changed_h(connection_t *c, char *request) {
 }
 
 bool send_req_key(node_t *to) {
-	return send_request(to->nexthop->connection, "%d %s %s 1", REQ_KEY, myself->name, to->name);
+	return send_request(to->nexthop->connection, "%d %s %s %d", REQ_KEY, myself->name, to->name, experimental ? 1 : 0);
 }
 
 bool req_key_h(connection_t *c, char *request) {
@@ -122,7 +123,7 @@ bool req_key_h(connection_t *c, char *request) {
 	/* Check if this key request is for us */
 
 	if(to == myself) {			/* Yes, send our own key back */
-		if(kx_version > 0) {
+		if(experimental && kx_version >= 1) {
 			logger(LOG_DEBUG, "Got ECDH key request from %s", from->name);
 			from->status.ecdh = true;
 		}
@@ -144,23 +145,35 @@ bool req_key_h(connection_t *c, char *request) {
 }
 
 bool send_ans_key_ecdh(node_t *to) {
-	char key[ECDH_SIZE * 2 + 1];
+	int siglen = ecdsa_size(&myself->connection->ecdsa);
+	char key[(ECDH_SIZE + siglen) * 2 + 1];
 
-	ecdh_generate_public(&to->ecdh, key);
+	if(!ecdh_generate_public(&to->ecdh, key))
+		return false;
 
-	bin2hex(key, key, ECDH_SIZE);
-	key[ECDH_SIZE * 2] = '\0';
+	if(!ecdsa_sign(&myself->connection->ecdsa, key, ECDH_SIZE, key + ECDH_SIZE))
+		return false;
 
-	return send_request(to->nexthop->connection, "%d %s %s ECDH:%s %d %d %zu %d", ANS_KEY,
-						myself->name, to->name, key,
+	b64encode(key, key, ECDH_SIZE + siglen);
+
+	char *pubkey = ecdsa_get_base64_public_key(&myself->connection->ecdsa);
+
+	if(!pubkey)
+		return false;
+
+	int result = send_request(to->nexthop->connection, "%d %s %s ECDH:%s:%s %d %d %zu %d", ANS_KEY,
+						myself->name, to->name, key, pubkey,
 						cipher_get_nid(&myself->incipher),
 						digest_get_nid(&myself->indigest),
 						digest_length(&myself->indigest),
 						myself->incompression);
+
+	free(pubkey);
+	return result;
 }
 
 bool send_ans_key(node_t *to) {
-	if(to->status.ecdh)
+	if(experimental && to->status.ecdh)
 		return send_ans_key_ecdh(to);
 
 	size_t keylen = cipher_keylength(&myself->incipher);
@@ -171,11 +184,10 @@ bool send_ans_key(node_t *to) {
 	to->incompression = myself->incompression;
 
 	randomize(key, keylen);
-	cipher_set_key(&to->incipher, key, true);
+	cipher_set_key(&to->incipher, key, false);
 	digest_set_key(&to->indigest, key, keylen);
 
 	bin2hex(key, key, keylen);
-	key[keylen * 2] = '\0';
 
 	// Reset sequence number and late packet window
 	mykeyused = true;
@@ -199,7 +211,7 @@ bool ans_key_h(connection_t *c, char *request) {
 	int cipher, digest, maclength, compression, keylen;
 	node_t *from, *to;
 
-	if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING" %d",
+	if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d "MAX_STRING" "MAX_STRING,
 		from_name, to_name, key, &cipher, &digest, &maclength,
 		&compression, address, port) < 7) {
 		logger(LOG_ERR, "Got bad %s from %s (%s)", "ANS_KEY", c->name,
@@ -278,64 +290,89 @@ bool ans_key_h(connection_t *c, char *request) {
 	from->outcompression = compression;
 
 	/* ECDH or old-style key exchange? */
-	/* TODO: look at SSH and TLS to see how they derive cipher and HMAC keys from shared secret properly */
 	
-	if(!strncmp(key, "ECDH:", 5)) {
-		logger(LOG_DEBUG, "Got ECDH key from %s", from->name);
+	if(experimental && !strncmp(key, "ECDH:", 5)) {
+		char *pubkey = strchr(key + 5, ':');
+		if(pubkey)
+			*pubkey++ = 0;
+			
+		/* Check if we already have an ECDSA public key for this node.
+		 * If not, use the one from the key exchange, and store it. */
+
+		if(!node_read_ecdsa_public_key(from)) {
+			if(!pubkey) {
+				logger(LOG_ERR, "No ECDSA public key known for %s (%s), cannot verify ECDH key exchange!", from->name, from->hostname);
+				return true;
+			}
+
+			if(!ecdsa_set_base64_public_key(&from->ecdsa, pubkey))
+				return true;
+
+			append_config_file(from->name, "ECDSAPublicKey", pubkey);
+		}
 
-		keylen = (strlen(key) - 5) / 2;
+		int siglen = ecdsa_size(&from->ecdsa);
+		int keylen = b64decode(key + 5, key + 5, sizeof key - 5);
 
-		if(keylen != ECDH_SIZE) {
-			logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
-			return false;
+		if(keylen != ECDH_SIZE + siglen) {
+			logger(LOG_ERR, "Node %s (%s) uses wrong keylength! %d != %d", from->name, from->hostname, keylen, ECDH_SIZE + siglen);
+			return true;
 		}
 
 		if(ECDH_SHARED_SIZE < cipher_keylength(&from->outcipher)) {
 			logger(LOG_ERR, "ECDH key too short for cipher of %s!", from->name);
-			return false;
+			return true;
+		}
+
+		if(!ecdsa_verify(&from->ecdsa, key + 5, ECDH_SIZE, key + 5 + ECDH_SIZE)) {
+			logger(LOG_ERR, "Possible intruder %s (%s): %s", from->name, from->hostname, "invalid ECDSA signature");
+			return true;
 		}
 
 		if(!from->ecdh) {
-			logger(LOG_DEBUG, "Woops, we didn't generate our public key yet");
 			from->status.ecdh = true;
 			if(!send_ans_key(from))
-				return false;
+				return true;
 		}
 
 		char shared[ECDH_SHARED_SIZE * 2 + 1];
-		char hex[ECDH_SHARED_SIZE * 2 + 1];
-		hex2bin(key + 5, key + 5, keylen);
 
 		if(!ecdh_compute_shared(&from->ecdh, key + 5, shared))
-			return false;
+			return true;
 
 		/* Update our crypto end */
 
-		char *mykey;
 		size_t mykeylen = cipher_keylength(&myself->incipher);
-		keylen = cipher_keylength(&from->outcipher);
-
-		if(ECDH_SHARED_SIZE < mykeylen) {
-			logger(LOG_ERR, "ECDH key too short for cipher of MYSELF!");
-			return false;
-		}
+		size_t hiskeylen = cipher_keylength(&from->outcipher);
 
+		char *mykey;
+		char *hiskey;
+		char *seed;
+		
 		if(strcmp(myself->name, from->name) < 0) {
-			logger(LOG_DEBUG, "Using left half of shared secret");
-			mykey = shared;
-			memcpy(key, shared + ECDH_SHARED_SIZE - keylen, keylen);
+			mykey = key;
+			hiskey = key + mykeylen * 2;
+			xasprintf(&seed, "tinc UDP key expansion %s %s", myself->name, from->name);
 		} else {
-			logger(LOG_DEBUG, "Using right half of shared secret");
-			mykey = shared + ECDH_SHARED_SIZE - mykeylen;
-			memcpy(key, shared, keylen);
+			mykey = key + hiskeylen * 2;
+			hiskey = key;
+			xasprintf(&seed, "tinc UDP key expansion %s %s", from->name, myself->name);
 		}
 
+		if(!prf(shared, ECDH_SHARED_SIZE, seed, strlen(seed), key, hiskeylen * 2 + mykeylen * 2))
+			return true;
+
+		free(seed);
+
 		cipher_open_by_nid(&from->incipher, cipher_get_nid(&myself->incipher));
 		digest_open_by_nid(&from->indigest, digest_get_nid(&myself->indigest), digest_length(&myself->indigest));
 		from->incompression = myself->incompression;
 
-		cipher_set_key(&from->incipher, mykey, true);
-		digest_set_key(&from->indigest, mykey, mykeylen);
+		cipher_set_key(&from->incipher, mykey, false);
+		digest_set_key(&from->indigest, mykey + mykeylen, mykeylen);
+
+		cipher_set_key(&from->outcipher, hiskey, true);
+		digest_set_key(&from->outdigest, hiskey + hiskeylen, hiskeylen);
 
 		// Reset sequence number and late packet window
 		mykeyused = true;
@@ -343,32 +380,22 @@ bool ans_key_h(connection_t *c, char *request) {
 		if(replaywin)
 			memset(from->late, 0, replaywin);
 
-		bin2hex(shared, hex, ECDH_SHARED_SIZE);
-		hex[ECDH_SHARED_SIZE * 2] = 0;
-		logger(LOG_DEBUG, "Shared secret was %s", hex);
-
-		bin2hex(mykey, hex, mykeylen);
-		hex[mykeylen * 2] = 0;
-		logger(LOG_DEBUG, "My part is: %s (%d)", hex, mykeylen);
-
-		bin2hex(key, hex, keylen);
-		hex[keylen * 2] = 0;
-		logger(LOG_DEBUG, "His part is: %s (%d)", hex, keylen);
+		if(strcmp(myself->name, from->name) < 0)
+			memmove(key, key + mykeylen * 2, hiskeylen * 2);
 	} else {
-		keylen = strlen(key) / 2;
-		hex2bin(key, key, keylen);
-	}
+		keylen = hex2bin(key, key, sizeof key);
+
+		if(keylen != cipher_keylength(&from->outcipher)) {
+			logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
+			return true;
+		}
 
-	/* Update our copy of the origin's packet key */
+		/* Update our copy of the origin's packet key */
 
-	if(keylen != cipher_keylength(&from->outcipher)) {
-		logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
-		return false;
+		cipher_set_key(&from->outcipher, key, true);
+		digest_set_key(&from->outdigest, key, keylen);
 	}
 
-	cipher_set_key(&from->outcipher, key, false);
-	digest_set_key(&from->outdigest, key, keylen);
-
 	from->status.validkey = true;
 	from->sent_seqno = 0;