From 391dcd73543e36abe3328fa115ac3f21411e34a5 Mon Sep 17 00:00:00 2001
From: rofl0r <retnyg@gmx.net>
Date: Tue, 12 Sep 2017 16:29:01 +0100
Subject: [PATCH] force server's ip address for outgoing connection when not
 bound to 0.0.0.0

if the user specifies a specific ip address for the server to listen on,
then it is assumed he wants to use this ip for outgoing connections.

closes #5
---
 server.c   | 12 ++++++++++++
 server.h   |  3 +++
 sockssrv.c |  4 ++++
 3 files changed, 19 insertions(+)

diff --git a/server.c b/server.c
index a71de3d..5bab56b 100644
--- a/server.c
+++ b/server.c
@@ -1,5 +1,6 @@
 #include "server.h"
 #include <stdio.h>
+#include <string.h>
 #include <unistd.h>
 
 int resolve(const char *host, unsigned short port, struct addrinfo** addr) {
@@ -13,6 +14,12 @@ int resolve(const char *host, unsigned short port, struct addrinfo** addr) {
 	return getaddrinfo(host, port_buf, &hints, addr);
 }
 
+int server_bindtoip(const struct server *server, int fd) {
+	if(server->bindaddr.v4.sin_family != AF_UNSPEC)
+		return bind(fd, (struct sockaddr*) &server->bindaddr, server->bindaddrsz);
+	return 0;
+}
+
 int server_waitclient(struct server *server, struct client* client) {
 	socklen_t clen = sizeof client->addr;
 	return ((client->fd = accept(server->fd, (void*)&client->addr, &clen)) == -1)*-1;
@@ -42,5 +49,10 @@ int server_setup(struct server *server, const char* listenip, unsigned short por
 		return -3;
 	}
 	server->fd = listenfd;
+	if(strcmp(listenip, "0.0.0.0") && !resolve(listenip, 0, &ainfo)) {
+		server->bindaddrsz = ainfo->ai_addrlen;
+		memcpy(&server->bindaddr, ainfo->ai_addr, ainfo->ai_addrlen);
+		freeaddrinfo(ainfo);
+	} else server->bindaddr.v4.sin_family = AF_UNSPEC;
 	return 0;
 }
diff --git a/server.h b/server.h
index 8f2f1a2..46d0a88 100644
--- a/server.h
+++ b/server.h
@@ -20,10 +20,13 @@ struct client {
 };
 
 struct server {
+	union sockaddr_union bindaddr;
 	int fd;
+	socklen_t bindaddrsz;
 };
 
 int resolve(const char *host, unsigned short port, struct addrinfo** addr);
+int server_bindtoip(const struct server *server, int fd);
 int server_waitclient(struct server *server, struct client* client);
 int server_setup(struct server *server, const char* listenip, unsigned short port);
 
diff --git a/sockssrv.c b/sockssrv.c
index e26c04d..42ab94c 100644
--- a/sockssrv.c
+++ b/sockssrv.c
@@ -38,6 +38,7 @@ static const char* auth_user;
 static const char* auth_pass;
 static sblist* auth_ips;
 static pthread_mutex_t auth_ips_mutex = PTHREAD_MUTEX_INITIALIZER;
+static const struct server* server;
 
 enum socksstate {
 	SS_1_CONNECTED,
@@ -139,6 +140,8 @@ static int connect_socks_target(unsigned char *buf, size_t n, struct client *cli
 			return -EC_GENERAL_FAILURE;
 		}
 	}
+	if(server_bindtoip(server, fd) == -1)
+		goto eval_errno;
 	if(connect(fd, remote->ai_addr, remote->ai_addrlen) == -1)
 		goto eval_errno;
 
@@ -393,6 +396,7 @@ int main(int argc, char** argv) {
 		perror("server_setup");
 		return 1;
 	}
+	server = &s;
 	while(1) {
 		collect(threads);
 		struct client c;
-- 
2.11.4.GIT