make remote_dns_subnet a config option

src/core.c

@@ -44,6 +44,7 @@ pthread_mutex_t internal_ips_lock;
 extern int tcp_read_time_out;
 extern int tcp_connect_time_out;
 extern int proxychains_quiet_mode;
+extern unsigned int remote_dns_subnet;
 
 internal_ip_lookup_table internal_ips = {0, 0, NULL};
 
@@ -84,7 +85,7 @@ in_addr_t make_internal_ip(uint32_t index) {
 	ip_type ret;
 	index++; // so we can start at .0.0.1
 	if(index > 0xFFFFFF) return (in_addr_t) -1;
-	ret.octet[0] = 224;
+	ret.octet[0] = remote_dns_subnet & 0xFF;
 	ret.octet[1] = (index & 0xFF0000) >> 16;
 	ret.octet[2] = (index & 0xFF00) >> 8;
 	ret.octet[3] = index & 0xFF;
@@ -260,7 +261,8 @@ static int tunnel_to(int sock, ip_type ip, unsigned short port, proxy_type pt,ch
 	// we use ip addresses with 224.* to lookup their dns name in our table, to allow remote DNS resolution
 	// the range 224-255.* is reserved, and it won't go outside (unless the app does some other stuff with
 	// the results returned from gethostbyname et al.)
-	if(ip.octet[0] == 224) {
+	// the hardcoded number 224 can now be changed using the config option remote_dns_subnet to i.e. 127
+	if(ip.octet[0] == remote_dns_subnet) {
 		dns_name = string_from_internal_ip(ip);
 		if(!dns_name) goto err;
 		dns_len = strlen(dns_name);
@@ -584,7 +586,7 @@ static int chain_step(int ns, proxy_data *pfrom, proxy_data *pto)
 #ifdef DEBUG
 	PDEBUG("chain_step()\n");
 #endif
-	if(pto->ip.octet[0] == 224) {
+	if(pto->ip.octet[0] == remote_dns_subnet) {
 		hostname = string_from_internal_ip(pto->ip);
 		if(!hostname) goto usenumericip;
 	} else {

src/libproxychains.c

@@ -55,6 +55,7 @@ int proxychains_resolver = 0;
 static int init_l = 0;
 localaddr_arg localnet_addr[MAX_LOCALNET];
 size_t num_localnet_addr = 0;
+unsigned int remote_dns_subnet = 224;
 
 static inline void get_chain_data(proxy_data *pd, unsigned int *proxy_count,
 	chain_type *ct);
@@ -232,18 +233,24 @@ static inline void get_chain_data(
 			 } else {
 				if(strstr(buff,"[ProxyList]")) {
 					list=1;
-				} else if(strstr(buff,"random_chain")) {
+				} else if(strstr(buff, "random_chain")) {
 					*ct=RANDOM_TYPE;
-				} else if(strstr(buff,"strict_chain")) {
+				} else if(strstr(buff, "strict_chain")) {
 					*ct=STRICT_TYPE;
-				} else if(strstr(buff,"dynamic_chain")) {
+				} else if(strstr(buff, "dynamic_chain")) {
 					*ct=DYNAMIC_TYPE;
 				} else if(strstr(buff,"tcp_read_time_out")){
-					sscanf(buff,"%s %d",user,&tcp_read_time_out) ;
+					sscanf(buff, "%s %d", user, &tcp_read_time_out);
 				} else if(strstr(buff,"tcp_connect_time_out")){
-					sscanf(buff,"%s %d",user,&tcp_connect_time_out) ;
+					sscanf(buff, "%s %d", user, &tcp_connect_time_out);
-				} else if(strstr(buff,"localnet")) {
+				} else if(strstr(buff,"remote_dns_subnet")){
-					if (sscanf(buff,"%s %21[^/]/%15s", user,
+					sscanf(buff, "%s %d", user, &remote_dns_subnet);
+					if(remote_dns_subnet >= 256) {
+						fprintf(stderr, "remote_dns_subnet: invalid value. requires a number between 0 and 255.\n");
+						exit(1);
+					}
+				} else if(strstr(buff, "localnet")) {
+					if (sscanf(buff, "%s %21[^/]/%15s", user,
 						local_in_addr_port, local_netmask) < 3) {
 						fprintf(stderr, "localnet format error");
 						exit(1);

src/proxychains.conf

@@ -37,6 +37,19 @@ strict_chain
 # Proxy DNS requests - no leak for DNS data
 proxy_dns 
 
+# set the class A subnet number to usefor use of the internal remote DNS mapping
+# we use the reserved 224.x.x.x range by default,
+# if the proxified app does a DNS request, we will return an IP from that range.
+# on further accesses to this ip we will send the saved DNS name to the proxy.
+# in case some control-freak app checks the returned ip, and denies to 
+# connect, you can use another subnet, e.g. 10.x.x.x or 127.x.x.x.
+# of course you should make sure that the proxified app does not need
+# *real* access to this subnet. 
+# i.e. dont use the same subnet then in the localnet section
+#remote_dns_subnet 127 
+#remote_dns_subnet 10
+remote_dns_subnet 224
+
 # Some timeouts in milliseconds
 tcp_read_time_out 15000
 tcp_connect_time_out 8000