From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sat, 29 Oct 2016 17:51:35 +0000 (+0200)
Subject: Enforce maximum amount of bytes sent/received on meta-connections.
X-Git-Tag: release-1.0.30~5
X-Git-Url: https://git.tinc-vpn.org/git/browse?a=commitdiff_plain;h=42ed8fd4cf3b3e527a38c03d713739fcdc6bf520;p=tinc

Enforce maximum amount of bytes sent/received on meta-connections.

This is sqrt(2^{block_length_in_bits}).
---

diff --git a/src/connection.c b/src/connection.c
index fd7ae843..8966d65d 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -91,6 +91,8 @@ void free_connection_partially(connection_t *c) {
 	c->outbufstart = 0;
 	c->last_ping_time = 0;
 	c->last_flushed_time = 0;
+	c->inbudget = 0;
+	c->outbudget = 0;
 
 	if(c->inctx) {
 		EVP_CIPHER_CTX_cleanup(c->inctx);
diff --git a/src/connection.h b/src/connection.h
index d3e9224d..0922fbea 100644
--- a/src/connection.h
+++ b/src/connection.h
@@ -71,6 +71,8 @@ typedef struct connection_t {
 	const EVP_CIPHER *outcipher;	/* Cipher we will use to send data to him */
 	EVP_CIPHER_CTX *inctx;		/* Context of encrypted meta data that will come from him to us */
 	EVP_CIPHER_CTX *outctx;		/* Context of encrypted meta data that will be sent from us to him */
+	uint64_t inbudget;              /* Encrypted bytes send budget */
+	uint64_t outbudget;             /* Encrypted bytes receive budget */
 	char *inkey;				/* His symmetric meta key + iv */
 	char *outkey;				/* Our symmetric meta key + iv */
 	int inkeylength;			/* Length of his key + iv */
diff --git a/src/meta.c b/src/meta.c
index 06ab96e4..63f565fe 100644
--- a/src/meta.c
+++ b/src/meta.c
@@ -62,6 +62,14 @@ bool send_meta(connection_t *c, const char *buffer, int length) {
 
 	/* Add our data to buffer */
 	if(c->status.encryptout) {
+		/* Check encryption limits */
+		if(length > c->outbudget) {
+			ifdebug(META) logger(LOG_ERR, "Byte limit exceeded for encryption to %s (%s)", c->name, c->hostname);
+			return false;
+		} else {
+			c->outbudget -= length;
+		}
+
 		result = EVP_EncryptUpdate(c->outctx, (unsigned char *)c->outbuf + c->outbufstart + c->outbuflen,
 				&outlen, (unsigned char *)buffer, length);
 		if(!result || outlen < length) {
@@ -175,6 +183,14 @@ bool receive_meta(connection_t *c) {
 		/* Decrypt */
 
 		if(c->status.decryptin && !decrypted) {
+			/* Check decryption limits */
+			if(lenin > c->inbudget) {
+				ifdebug(META) logger(LOG_ERR, "Byte limit exceeded for decryption from %s (%s)", c->name, c->hostname);
+				return false;
+			} else {
+				c->inbudget -= lenin;
+			}
+
 			result = EVP_DecryptUpdate(c->inctx, (unsigned char *)inbuf, &lenout, (unsigned char *)c->buffer + oldlen, lenin);
 			if(!result || lenout != lenin) {
 				logger(LOG_ERR, "Error while decrypting metadata from %s (%s): %s",
diff --git a/src/protocol_auth.c b/src/protocol_auth.c
index 46b38eb8..ddecbc62 100644
--- a/src/protocol_auth.c
+++ b/src/protocol_auth.c
@@ -195,6 +195,7 @@ bool send_metakey(connection_t *c) {
 			return false;
 		}
 
+		c->outbudget = (uint64_t)4 << EVP_CIPHER_key_length(c->outcipher);
 		c->status.encryptout = true;
 	}
 
@@ -273,6 +274,7 @@ bool metakey_h(connection_t *c) {
 			return false;
 		}
 
+		c->inbudget = (uint64_t)4 << EVP_CIPHER_key_length(c->incipher);
 		c->status.decryptin = true;
 	} else {
 		c->incipher = NULL;