support for dhcpv6

dhcp_protect.c

 
 	if ( conf->debug ) printf("got a packet, len = %i\n", pktlen);
 
-	/* a bit too much ;)
-	if ( conf->debug ) {
-		for(i=0; i<pktlen; i++) {
-			if ( !(i%16) ) printf("\n");
-			printf("%02x ", pkt[i]);
-		}
-	}
-	*/
-
 	// can we read the IP proto and IP header length ?
 	if ( pktlen > 0 ) {
 		ipver = pkt[offset];
 		ihl   = pkt[offset];
 		ihl  &= 0x0f;
 
-		if ( ipver != 4 ) {
+		if ( ipver == 4 ) {
+			// jump to DHCPv4
+			offset += ( ihl * 4 ) + 8;
+			dhcpv4_check(conf, pkt, pktlen, offset, &remoteid, &remoteidlen);
+		}
+		else if ( ipver == 6 ) {
+			// jump to DHCPv6
+			offset += 48 + 8;
+			dhcpv6_check(conf, pkt, pktlen, offset, &remoteid, &remoteidlen);
+		}
+		else {		
 			if ( conf->debug ) printf("not an IPv4 packet\n");
-			rv = NF_ACCEPT;
 			goto end;
 		}
+	}
 
-		// jump over the IPv4 header
-		offset += ihl * 4;
+	if ( remoteidlen>0 ) {
+		// count the packet, even when blacklisted.
+		dp_accounting_add(conf, remoteid, remoteidlen);
+
+		// check if already in the blacklist
+		if ( dp_blacklist_check(conf, remoteid, remoteidlen) == NF_DROP )
+			rv = NF_DROP;
+
+		// check if it must be added to the blacklist
+		else if ( dp_accounting_check(conf, remoteid, remoteidlen) == NF_DROP ) {
+			dp_blacklist_add(conf, remoteid, remoteidlen);
+			rv = NF_DROP;
+		}
 	}
 
+	end:
+
+	dp_hash_cleanup(conf);
 
-	// jump over UDP + DHCP header
-	offset += 8 + 28 + 16 + 64 + 128;
+	return rv;
+}
+
+void dhcpv6_check(dp_conf *conf, unsigned char *pkt, int pktlen, int offset, unsigned char *remoteid, int *remoteidlen) {
+
+	while(offset<pktlen) {
+		uint8_t msgtype = (uint8_t)pkt[offset];
+
+		switch(msgtype) {
+			case 11: // RELAY-FORW
+			case 12: // RELAY-REPL
+				offset += 2 + 16 + 16; // msg-type, hop-count, link-addr, peer-addr
+				break;
+			default: // all other msgtypes
+				offset += 2; // msg-type, hop-count
+		}
+
+		while(offset+1<pktlen) {
+			uint8_t code = (uint8_t)pkt[offset];
+			uint8_t len  = (uint8_t)pkt[offset+1];
+
+			offset+2;
+
+			if ( code == 1 ) { // Client identifier / DUID
+				remoteid = pkt+offset;
+				*remoteidlen = len;
+				break;
+			}
+			offset+=len;
+		}
+
+		if ( *remoteidlen>0 )
+			break;
+	}
+}
+
+
+void dhcpv4_check(dp_conf *conf, unsigned char *pkt, int pktlen, int offset, unsigned char *remoteid, int *remoteidlen) {
+	int hwaddrpos = offset + 28; // remember where the hw addr is if we need to fallback to it
+	int hwlenpos = offset + 2;   // remember where the hw addr len is if we need to fallback to it
+
+	// jump DHCP header
+	offset += 28 + 16 + 64 + 128;
 
 	// minimum packet size, fixed header + magic cookie (4 octets)
 	if ( pktlen < offset + 4 ) {
 		if ( conf->debug ) printf("packet too small\n");
-		rv = NF_ACCEPT;
-		goto end;
+		return;
 	}
 
 	// check magic cookie
 				"invalid magic cookie %02x%02x%02x%02x\n",
 				pkt[offset], pkt[offset+1],
 				pkt[offset+2], pkt[offset+3]);
-
-		rv = NF_ACCEPT;
-		goto end;
+		return;
 	}
 	offset+=4;
 
 					// make sure we don't overflow and can read all data
 					if ( o82off + olen > len ) {
 						if ( conf->debug) printf("option 82.2 data too long\n");
-						rv = NF_ACCEPT;
-						goto end;
+						break;
 					}
 					else {
 						remoteid = o82 + o82off;
-						remoteidlen = olen;
-						found=1;
+						*remoteidlen = olen;
 					}
 				}
 
 		offset+=len;
 	}
 
-	if ( found ) {
-		// count the packet, even when blacklisted.
-		dp_accounting_add(conf, remoteid, remoteidlen);
-
-		// check if already in the blacklist
-		if ( dp_blacklist_check(conf, remoteid, remoteidlen) == NF_DROP )
-			rv = NF_DROP;
-
-		// check if it must be added to the blacklist
-		else if ( dp_accounting_check(conf, remoteid, remoteidlen) == NF_DROP ) {
-			dp_blacklist_add(conf, remoteid, remoteidlen);
-			rv = NF_DROP;
+	// if we didn't find opt82.2, we fallback to the hw addr
+	if ( *remoteidlen == 0 ) {
+		// nope, we won't overflow
+		if ( (uint8_t)pkt[hwlenpos] <= 16 ) {
+			remoteid = pkt+hwaddrpos;
+			remoteidlen = (uint8_t)pkt[hwlenpos];
 		}
 	}
-
-	end:
-
-	dp_hash_cleanup(conf);
-
-	return rv;
 }
 
 // netfilter queue callback