/*
* tlsproxy is a transparent TLS proxy for HTTPS connections.
*
* Copyright (C) 2011 Simon Ruderich
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see .
*/
#include
#include
/* socket(), bind(), accept(), listen() */
#include
#include
/* close() */
#include
/* htons() */
#include
/* getaddrinfo() */
#include
/* strncmp() */
#include
/* poll() */
#include
/* Maximum line of the request line. Longer request lines are aborted with an
* error. The standard doesn't specify a maximum line length but this should
* be a good limit to make processing simpler. */
#define MAX_REQUEST_LINE 4096
/* Proxy hostname and port if specified on the command line. */
static char *use_proxy_host;
static char *use_proxy_port;
static void handle_connection(int socket);
static int read_http_request(FILE *client_fd, char *request, size_t length);
static void send_close_bad_request(FILE *client_fd);
static void send_close_forwarding_failure(FILE *client_fd);
static void transfer_data(int client, int server);
static int read_from_write_to(int from, int to);
static int connect_to_host(const char *hostname, const char *port);
static int parse_request(const char *buffer, char *host, char *port,
int *version_minor);
int main(int argc, char **argv) {
int port;
int client_socket, server_socket;
struct sockaddr_in6 server_in;
if (2 != argc && 5 != argc) {
printf("Usage: %s [-proxy hostname port] port\n", argv[0]);
return EXIT_FAILURE;
}
port = atoi(argv[5 == argc ? 4 : 1]);
if (0 >= port || 0xffff < port) {
printf("Usage: %s [-proxy hostname port] port\n", argv[0]);
printf("\n");
printf("Invalid port: %s!\n", argv[5 == argc ? 4 : 1]);
return EXIT_FAILURE;
}
if (5 == argc) {
use_proxy_host = strdup(argv[2]);
use_proxy_port = strdup(argv[3]);
if (NULL == use_proxy_host || NULL == use_proxy_port) {
perror("strdup()");
return EXIT_FAILURE;
}
#ifdef DEBUG
printf("Using proxy: %s:%s.\n", use_proxy_host, use_proxy_port);
#endif
}
server_socket = socket(PF_INET6, SOCK_STREAM, 0);
if (-1 == server_socket) {
perror("socket()");
return EXIT_FAILURE;
}
#ifdef DEBUG
/* Fast rebinding for debug mode, could cause invalid packets. */
{
int socket_option = 1;
setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR,
&socket_option, sizeof(socket_option));
}
#endif
/* Bind to the listen socket. */
memset(&server_in, 0, sizeof(server_in));
server_in.sin6_family = AF_INET6; /* IPv6 (and IPv4) */
server_in.sin6_addr = in6addr_any; /* bind to any address */
server_in.sin6_port = htons((uint16_t)port); /* port to bind to */
if (-1 == bind(server_socket, (struct sockaddr *)&server_in,
sizeof(server_in))) {
perror("bind()");
return EXIT_FAILURE;
}
/* And accept connections. */
if (-1 == listen(server_socket, 5)) {
perror("listen()");
return EXIT_FAILURE;
}
#ifdef DEBUG
printf("Listening for connections on port %d.\n", port);
#endif
for (;;) {
/* Accept new connection. */
client_socket = accept(server_socket, NULL, NULL);
if (-1 == client_socket) {
perror("accept()");
return EXIT_FAILURE;
}
handle_connection(client_socket);
}
return EXIT_SUCCESS;
}
static void handle_connection(int client_socket) {
int server_socket;
FILE *client_fd, *server_fd;
char buffer[MAX_REQUEST_LINE];
char host[MAX_REQUEST_LINE];
char port[5 + 1];
int version_minor;
int result;
client_fd = fdopen(client_socket, "a+");
if (NULL == client_fd) {
perror("fdopen()");
close(client_socket);
return;
}
#ifdef DEBUG
printf("New connection:\n");
#endif
/* Read request line (CONNECT ..) and headers (they are discarded). */
result = read_http_request(client_fd, buffer, sizeof(buffer));
if (result == -1) {
/* Read error. */
return;
} else if (result == -2) {
/* EOF */
send_close_bad_request(client_fd);
return;
}
#ifdef DEBUG
printf(" request: %s", buffer);
#endif
if (0 != parse_request(buffer, host, port, &version_minor)) {
send_close_bad_request(client_fd);
#ifdef DEBUG
printf(" bad request\n");
#endif
return;
}
#ifdef DEBUG
printf(" %s:%s (HTTP 1.%d)\n", host, port, version_minor);
#endif
/* Connect to proxy server or directly to server. */
if (NULL != use_proxy_host && NULL != use_proxy_port) {
server_socket = connect_to_host(use_proxy_host, use_proxy_port);
} else {
server_socket = connect_to_host(host, port);
}
if (-1 == server_socket) {
send_close_forwarding_failure(client_fd);
return;
}
server_fd = fdopen(server_socket, "a+");
if (NULL == server_fd) {
send_close_forwarding_failure(client_fd);
return;
}
/* Connect to proxy if requested (command line option). */
if (NULL != use_proxy_host && NULL != use_proxy_port) {
fprintf(server_fd, "CONNECT %s:%s HTTP/1.0\r\n", host, port);
fprintf(server_fd, "\r\n");
/* Read response line from proxy server. */
result = read_http_request(server_fd, buffer, sizeof(buffer));
if (result == -1) {
/* Read error. */
send_close_forwarding_failure(client_fd);
return;
} else if (result == -2) {
/* EOF */
fclose(server_fd);
send_close_forwarding_failure(client_fd);
return;
}
/* Check response of proxy server. */
if (0 != strncmp(buffer, "HTTP/1.0 200", 12)) {
#ifdef DEBUG
printf(" bad proxy response\n");
#endif
fclose(server_fd);
send_close_forwarding_failure(client_fd);
return;
}
}
#ifdef DEBUG
printf(" connection to server established\n");
#endif
/* We've established a connection, tell the client. */
fprintf(client_fd, "HTTP/1.0 200 Connection established\r\n");
fprintf(client_fd, "\r\n");
fflush(client_fd);
/* And transfer all data between client and server transparently. */
transfer_data(client_socket, server_socket);
fclose(client_fd);
fclose(server_fd);
}
/* Read HTTP request line and headers (ignored).
*
* On success 0 is returned, -1 on client error (we close client descriptor in
* this case), -2 on unexpected EOF.
*/
static int read_http_request(FILE *client_fd, char *request, size_t length) {
char buffer[MAX_REQUEST_LINE];
if (NULL == fgets(request, (int)length, client_fd)) {
if (ferror(client_fd)) {
perror("fgets(), request");
fclose(client_fd);
return -1;
}
return -2;
}
while (NULL != fgets(buffer, MAX_REQUEST_LINE, client_fd)) {
/* End of header. */
if (0 == strcmp(buffer, "\n") || 0 == strcmp(buffer, "\r\n")) {
break;
}
}
if (ferror(client_fd)) {
perror("fgets(), header");
fclose(client_fd);
return -1;
}
return 0;
}
static void send_close_bad_request(FILE *client_fd) {
fprintf(client_fd, "HTTP/1.0 400 Bad Request\r\n");
fprintf(client_fd, "\r\n");
fclose(client_fd);
}
static void send_close_forwarding_failure(FILE *client_fd) {
fprintf(client_fd, "HTTP/1.0 503 Forwarding failure\r\n");
fprintf(client_fd, "\r\n");
fclose(client_fd);
}
/* Transfer data between client and server sockets until one closes the
* connection. */
static void transfer_data(int client, int server) {
struct pollfd fds[2];
fds[0].fd = client;
fds[0].events = POLLIN | POLLPRI | POLLHUP | POLLERR;
fds[0].revents = 0;
fds[1].fd = server;
fds[1].events = POLLIN | POLLPRI | POLLHUP | POLLERR;
fds[1].revents = 0;
for (;;) {
int result = poll(fds, 2, 0);
if (result < 0) {
perror("poll()");
return;
}
/* Data available from client. */
if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
if (0 != read_from_write_to(client, server)) {
/* EOF (or other error) */
break;
}
}
/* Data available from server. */
if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
if (0 != read_from_write_to(server, client)) {
/* EOF (or other error) */
break;
}
}
/* Client closed connection. */
if (fds[0].revents & POLLERR || fds[0].revents & POLLHUP) {
break;
}
/* Server closed connection. */
if (fds[1].revents & POLLERR || fds[1].revents & POLLHUP) {
break;
}
}
}
/* Read available data from socket from and write it to socket to. At maximum
* 4096 bytes are read/written. */
static int read_from_write_to(int from, int to) {
ssize_t size_read;
ssize_t size_written;
char buffer[4096];
size_read = read(from, buffer, sizeof(buffer));
if (0 > size_read) {
perror("read()");
return -1;
}
/* EOF */
if (0 == size_read) {
return -1;
}
size_written = write(to, buffer, (size_t)size_read);
if (0 > size_written) {
perror("write()");
return -1;
}
if (size_read != size_written) {
printf("only written %ld of %ld bytes!\n", size_read, size_written);
return -1;
}
return 0;
}
static int connect_to_host(const char *hostname, const char *port) {
struct addrinfo gai_hints;
struct addrinfo *gai_result;
int gai_return;
int server_socket;
struct addrinfo *server;
if (NULL == hostname || NULL == port) {
return -1;
}
/* Get IP of hostname server. */
memset(&gai_hints, 0, sizeof(gai_hints));
gai_hints.ai_family = AF_UNSPEC;
gai_hints.ai_socktype = SOCK_STREAM;
gai_hints.ai_protocol = 0;
gai_hints.ai_flags = AI_NUMERICSERV /* given port is numeric */
| AI_ADDRCONFIG /* supported by this computer */
| AI_V4MAPPED; /* support IPv4 through IPv6 */
gai_return = getaddrinfo(hostname, port, &gai_hints, &gai_result);
if (0 != gai_return) {
perror("getaddrinfo()");
return -1;
}
/* Now try to connect to each server returned by getaddrinfo(), use the
* first successful connect. */
for (server = gai_result; NULL != server; server = server->ai_next) {
server_socket = socket(server->ai_family,
server->ai_socktype,
server->ai_protocol);
if (-1 == server_socket) {
perror("socket(), trying next");
continue;
}
if (-1 != connect(server_socket, server->ai_addr,
server->ai_addrlen)) {
break;
}
perror("connect(), trying next");
close(server_socket);
}
/* Make sure we free the result from getaddrinfo(). */
freeaddrinfo(gai_result);
if (NULL == server) {
fprintf(stderr, "no server found, aborting\n");
return -1;
}
return server_socket;
}
/* Parse HTTP CONNECT request string and save its parameters.
*
* The following format is expected: "CONNECT host:port HTTP/1.y".
*
* request and host must have the same size! port must be at least 6 bytes
* long (5 + '\0').
*/
static int parse_request(const char *request, char *host, char *port,
int *version_minor) {
int port_unused; /* just used to verify the port is numeric */
char *position;
/* scanf() doesn't check spaces. */
if (0 != strncmp(request, "CONNECT ", 8)) {
return -1;
}
/* Check request and extract data, "host:port" is not yet separated. */
if (2 != sscanf(request, "CONNECT %s HTTP/1.%d",
host, version_minor)) {
return -1;
}
/* Make sure ":port" is there. */
if (NULL == (position = strchr(host, ':'))) {
return -1;
}
/* Make sure port is numeric. */
if (1 != sscanf(position + 1, "%d", &port_unused)) {
return -1;
}
/* Store it in *port. */
strncpy(port, position + 1, 5);
port[5] = '\0';
/* And remove port from host. */
*position = '\0';
return 0;
}