From: Guus Sliepen <guus@tinc-vpn.org>
Date: Fri, 18 Dec 2009 00:15:25 +0000 (+0100)
Subject: Fix packet authentication.
X-Git-Tag: import-tinc-1.1~568
X-Git-Url: https://git.meshlink.io/?a=commitdiff_plain;h=c845bc109c85e6fb350096c63e13ef8e617ee29b;p=meshlink

Fix packet authentication.

This wasn't working at all, since we didn't do HMAC but just a plain hash.
Also, verification of packets failed because it was checking the whole packet,
not the packet minus the HMAC.
---

diff --git a/src/gcrypt/digest.c b/src/gcrypt/digest.c
index 34f9d280..066600f9 100644
--- a/src/gcrypt/digest.c
+++ b/src/gcrypt/digest.c
@@ -87,6 +87,7 @@ static bool digest_open(digest_t *digest, int algo, int maclength) {
 		digest->maclength = maclength;
 	
 	digest->algo = algo;
+	digest->hmac = NULL;
 
 	return true;
 }
@@ -118,24 +119,45 @@ bool digest_open_sha1(digest_t *digest, int maclength) {
 }
 
 void digest_close(digest_t *digest) {
+	if(digest->hmac)
+		gcry_md_close(digest->hmac);
+	digest->hmac = NULL;
+}
+
+bool digest_set_key(digest_t *digest, const void *key, size_t len) {
+	if(!digest->hmac)
+		gcry_md_open(&digest->hmac, digest->algo, GCRY_MD_FLAG_HMAC);
+	if(!digest->hmac)
+		return false;
+
+	return !gcry_md_setkey(digest->hmac, key, len);
 }
 
 bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *outdata) {
 	unsigned int len = gcry_md_get_algo_dlen(digest->algo);
-	char tmpdata[len];
 
-	gcry_md_hash_buffer(digest->algo, tmpdata, indata, inlen);
-	memcpy(outdata, tmpdata, digest->maclength);
+	if(digest->hmac) {
+		char *tmpdata;
+		gcry_md_reset(digest->hmac);
+		gcry_md_write(digest->hmac, indata, inlen);
+		tmpdata = gcry_md_read(digest->hmac, digest->algo);
+		if(!tmpdata)
+			return false;
+		memcpy(outdata, tmpdata, digest->maclength);
+	} else {
+		char tmpdata[len];
+		gcry_md_hash_buffer(digest->algo, tmpdata, indata, inlen);
+		memcpy(outdata, tmpdata, digest->maclength);
+	}
 
 	return true;
 }
 
 bool digest_verify(digest_t *digest, const void *indata, size_t inlen, const void *cmpdata) {
-	unsigned int len = gcry_md_get_algo_dlen(digest->algo);
+	unsigned int len = digest->maclength;
 	char outdata[len];
 
-	gcry_md_hash_buffer(digest->algo, outdata, indata, inlen);
-	return !memcmp(cmpdata, outdata, digest->maclength);
+	return digest_create(digest, indata, inlen, outdata) && !memcmp(cmpdata, outdata, len);
 }
 
 int digest_get_nid(const digest_t *digest) {
diff --git a/src/gcrypt/digest.h b/src/gcrypt/digest.h
index f70fecce..1188496a 100644
--- a/src/gcrypt/digest.h
+++ b/src/gcrypt/digest.h
@@ -28,6 +28,7 @@ typedef struct digest {
 	int algo;
 	int nid;
 	int maclength;
+	gcry_md_hd_t hmac;
 } digest_t;
 
 extern bool digest_open_by_name(struct digest *, const char *name, int maclength);
@@ -36,6 +37,7 @@ extern bool digest_open_sha1(struct digest *, int maclength);
 extern void digest_close(struct digest *);
 extern bool digest_create(struct digest *, const void *indata, size_t inlen, void *outdata);
 extern bool digest_verify(struct digest *, const void *indata, size_t inlen, const void *digestdata);
+extern bool digest_set_key(struct digest *, const void *key, size_t len);
 extern int digest_get_nid(const struct digest *);
 extern size_t digest_length(const struct digest *);
 extern bool digest_active(const struct digest *);
diff --git a/src/net_packet.c b/src/net_packet.c
index aaa0c720..df6f4826 100644
--- a/src/net_packet.c
+++ b/src/net_packet.c
@@ -195,7 +195,7 @@ static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
 	if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
 		return false;
 
-	return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len);
+	return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
 }
 
 static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
@@ -222,11 +222,13 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
 
 	/* Check the message authentication code */
 
-	if(digest_active(&n->indigest) && !digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
-		ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
-		return;
+	if(digest_active(&n->indigest)) {
+		inpkt->len -= n->indigest.maclength;
+ 		if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
+			ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
+			return;
+		}
 	}
-
 	/* Decrypt the packet */
 
 	if(cipher_active(&n->incipher)) {
@@ -501,31 +503,28 @@ void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
 
 static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 	splay_node_t *node;
-	edge_t *e;
-	node_t *n = NULL;
+	node_t *n, *found = NULL;
 	static time_t last_hard_try = 0;
 	time_t now = time(NULL);
 
-	for(node = edge_weight_tree->head; node; node = node->next) {
-		e = node->data;
-
-		if(sockaddrcmp_noport(from, &e->address)) {
-			if(last_hard_try == now)
-				continue;
-			last_hard_try = now;
-		}
+	if(last_hard_try == now)
+		return NULL;
+	else
+		last_hard_try = now;
 
-		if(!n)
-			n = e->to;
+	for(node = node_tree->head; node; node = node->next) {
+		n = node->data;
 
-		if(!try_mac(e->to, pkt))
+		if(n == myself || !digest_active(&n->indigest))
 			continue;
 
-		n = e->to;
-		break;
+		if(try_mac(n, pkt)) {
+			found = n;
+			break;
+		}
 	}
 
-	return n;
+	return found;
 }
 
 void handle_incoming_vpn_data(int sock, short events, void *data) {
diff --git a/src/openssl/digest.c b/src/openssl/digest.c
index ff350daa..f20a9755 100644
--- a/src/openssl/digest.c
+++ b/src/openssl/digest.c
@@ -18,8 +18,11 @@
 */
 
 #include "system.h"
+#include "utils.h"
+#include "xalloc.h"
 
 #include <openssl/err.h>
+#include <openssl/hmac.h>
 
 #include "digest.h"
 #include "logger.h"
@@ -35,6 +38,7 @@ static void set_maclength(digest_t *digest, int maclength) {
 
 bool digest_open_by_name(digest_t *digest, const char *name, int maclength) {
 	digest->digest = EVP_get_digestbyname(name);
+	digest->key = NULL;
 
 	if(!digest->digest) {
 		logger(LOG_DEBUG, "Unknown digest name '%s'!", name);
@@ -47,6 +51,7 @@ bool digest_open_by_name(digest_t *digest, const char *name, int maclength) {
 
 bool digest_open_by_nid(digest_t *digest, int nid, int maclength) {
 	digest->digest = EVP_get_digestbynid(nid);
+	digest->key = NULL;
 
 	if(!digest->digest) {
 		logger(LOG_DEBUG, "Unknown digest nid %d!", nid);
@@ -59,25 +64,39 @@ bool digest_open_by_nid(digest_t *digest, int nid, int maclength) {
 
 bool digest_open_sha1(digest_t *digest, int maclength) {
 	digest->digest = EVP_sha1();
+	digest->key = NULL;
 
 	set_maclength(digest, maclength);
 	return true;
 }
 
+bool digest_set_key(digest_t *digest, const void *key, size_t len) {
+	digest->key = xrealloc(digest->key, len);
+	memcpy(digest->key, key, len);
+	digest->keylength = len;
+}
+
 void digest_close(digest_t *digest) {
+	if(digest->key)
+		free(digest->key);
+	digest->key = NULL;
 }
 
 bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *outdata) {
 	size_t len = EVP_MD_size(digest->digest);
 	unsigned char tmpdata[len];
 
-	EVP_MD_CTX ctx;
-
-	if(!EVP_DigestInit(&ctx, digest->digest)
-			|| !EVP_DigestUpdate(&ctx, indata, inlen)
-			|| !EVP_DigestFinal(&ctx, tmpdata, NULL)) {
-		logger(LOG_DEBUG, "Error creating digest: %s", ERR_error_string(ERR_get_error(), NULL));
-		return false;
+	if(digest->key) {
+		HMAC(digest->digest, digest->key, digest->keylength, indata, inlen, tmpdata, NULL);
+	} else {
+		EVP_MD_CTX ctx;
+
+		if(!EVP_DigestInit(&ctx, digest->digest)
+				|| !EVP_DigestUpdate(&ctx, indata, inlen)
+				|| !EVP_DigestFinal(&ctx, tmpdata, NULL)) {
+			logger(LOG_DEBUG, "Error creating digest: %s", ERR_error_string(ERR_get_error(), NULL));
+			return false;
+		}
 	}
 
 	memcpy(outdata, tmpdata, digest->maclength);
@@ -85,7 +104,7 @@ bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *out
 }
 
 bool digest_verify(digest_t *digest, const void *indata, size_t inlen, const void *cmpdata) {
-	size_t len = EVP_MD_size(digest->digest);
+	size_t len = digest->maclength;
 	unsigned char outdata[len];
 
 	return digest_create(digest, indata, inlen, outdata) && !memcmp(cmpdata, outdata, digest->maclength);
diff --git a/src/openssl/digest.h b/src/openssl/digest.h
index 258bcf6c..f3855c92 100644
--- a/src/openssl/digest.h
+++ b/src/openssl/digest.h
@@ -27,6 +27,8 @@
 typedef struct digest {
 	const EVP_MD *digest;
 	int maclength;
+	int keylength;
+	char *key;
 } digest_t;
 
 extern bool digest_open_by_name(struct digest *, const char *name, int maclength);
@@ -35,6 +37,7 @@ extern bool digest_open_sha1(struct digest *, int maclength);
 extern void digest_close(struct digest *);
 extern bool digest_create(struct digest *, const void *indata, size_t inlen, void *outdata);
 extern bool digest_verify(struct digest *, const void *indata, size_t inlen, const void *digestdata);
+extern bool digest_set_key(struct digest *, const void *key, size_t len);
 extern int digest_get_nid(const struct digest *);
 extern size_t digest_length(const struct digest *);
 extern bool digest_active(const struct digest *);
diff --git a/src/protocol_key.c b/src/protocol_key.c
index aae5516c..3b022679 100644
--- a/src/protocol_key.c
+++ b/src/protocol_key.c
@@ -139,6 +139,7 @@ bool send_ans_key(node_t *to) {
 
 	randomize(key, keylen);
 	cipher_set_key(&to->incipher, key, true);
+	digest_set_key(&to->indigest, key, keylen);
 
 	bin2hex(key, key, keylen);
 	key[keylen * 2] = '\0';
@@ -160,7 +161,7 @@ bool ans_key_h(connection_t *c, char *request) {
 	char from_name[MAX_STRING_SIZE];
 	char to_name[MAX_STRING_SIZE];
 	char key[MAX_STRING_SIZE];
-	int cipher, digest, maclength, compression;
+	int cipher, digest, maclength, compression, keylen;
 	node_t *from, *to;
 
 	if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d",
@@ -209,7 +210,9 @@ bool ans_key_h(connection_t *c, char *request) {
 		return false;
 	}
 
-	if(strlen(key) / 2 != cipher_keylength(&from->outcipher)) {
+	keylen = strlen(key) / 2;
+
+	if(keylen != cipher_keylength(&from->outcipher)) {
 		logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
 		return false;
 	}
@@ -233,8 +236,9 @@ bool ans_key_h(connection_t *c, char *request) {
 
 	/* Update our copy of the origin's packet key */
 
-	hex2bin(key, key, cipher_keylength(&from->outcipher));
+	hex2bin(key, key, keylen);
 	cipher_set_key(&from->outcipher, key, false);
+	digest_set_key(&from->outdigest, key, keylen);
 
 	from->status.validkey = true;
 	from->status.waitingforkey = false;