/*
* Handle 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 "tlsproxy.h"
#include "connection.h"
#include "verify.h"
/* close() */
#include
/* getaddrinfo() */
#include
/* poll() */
#include
/* errno */
#include
/* Maximum line of a HTTP 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
static int initialize_tls_session_client(int peer_socket,
const char *hostname,
gnutls_session_t *session,
gnutls_certificate_credentials_t *x509_cred);
static int initialize_tls_session_server(int peer_socket,
gnutls_session_t *session,
gnutls_certificate_credentials_t *x509_cred);
static int read_http_request(FILE *client_fd, char *request, size_t length);
static void send_bad_request(FILE *client_fd);
static void send_forwarding_failure(FILE *client_fd);
static void tls_send_invalid_cert_message(gnutls_session_t session);
#if 0
static void transfer_data(int client, int server);
static int read_from_write_to(int from, int to);
#endif
static void transfer_data_tls(int client, int server,
gnutls_session_t client_session,
gnutls_session_t server_session);
static int read_from_write_to_tls(gnutls_session_t from, gnutls_session_t 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);
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_x509_cred is used when talking to the client (acting as a TSL
* server), server_x509_cred is used when talking to the server (acting as
* a TSL client). */
gnutls_certificate_credentials_t client_x509_cred, server_x509_cred;
gnutls_session_t client_session, server_session;
/* initialize_tls_session_*() called? - used for goto out */
int client_session_init, server_session_init;
/* gnutls_handshake() called? - used for goto out */
int client_session_started, server_session_started;
/* Validation failed? If yes we need to send the special "invalid"
* certificate. */
int validation_failed;
LOG(LOG_DEBUG, "new connection");
server_socket = -1;
client_fd = NULL;
server_fd = NULL;
client_session_init = 0;
server_session_init = 0;
client_session_started = 0;
server_session_started = 0;
validation_failed = 0;
client_fd = fdopen(client_socket, "a+");
if (NULL == client_fd) {
LOG_PERROR(LOG_WARNING, "fdopen(): client failed");
goto out;
}
/* Read request line (CONNECT ..) and headers (they are discarded). */
result = read_http_request(client_fd, buffer, sizeof(buffer));
if (-1 == result) {
/* Read error. */
LOG(LOG_WARNING, "read_http_request(): client read error");
goto out;
} else if (-2 == result) {
/* EOF */
LOG(LOG_WARNING, "read_http_request(): client EOF");
send_bad_request(client_fd);
goto out;
}
if (0 != parse_request(buffer, host, port, &version_minor)) {
LOG(LOG_WARNING, "bad request: %s", buffer);
send_bad_request(client_fd);
goto out;
}
LOG(LOG_DEBUG, "target: %s:%s (HTTP 1.%d)", host, port, version_minor);
/* Connect to proxy server or directly to server. */
if (NULL != global_proxy_host && NULL != global_proxy_port) {
LOG(LOG_DEBUG, "connecting to %s:%s", global_proxy_host,
global_proxy_port);
server_socket = connect_to_host(global_proxy_host, global_proxy_port);
} else {
LOG(LOG_DEBUG, "connecting to %s:%s", host, port);
server_socket = connect_to_host(host, port);
}
if (-1 == server_socket) {
LOG(LOG_WARNING, "failed to connect to server");
send_forwarding_failure(client_fd);
goto out;
}
server_fd = fdopen(server_socket, "a+");
if (NULL == server_fd) {
LOG_PERROR(LOG_WARNING, "fdopen(): server failed");
send_forwarding_failure(client_fd);
goto out;
}
/* Connect to proxy if requested (command line option). */
if (NULL != global_proxy_host && NULL != global_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 (-1 == result) {
/* Read error. */
LOG(LOG_WARNING, "read_http_request(): proxy read error");
send_forwarding_failure(client_fd);
goto out;
} else if (-2 == result) {
/* EOF */
LOG(LOG_WARNING, "read_http_request(): proxy EOF");
send_forwarding_failure(client_fd);
goto out;
}
/* Check response of proxy server. */
if (0 != strncmp(buffer, "HTTP/1.0 200", 12)) {
LOG(LOG_WARNING, "bad proxy response: %s", buffer);
send_forwarding_failure(client_fd);
goto out;
}
}
LOG(LOG_DEBUG, "connection to server established");
result = initialize_tls_session_server(server_socket, &server_session,
&server_x509_cred);
/* Initialize TLS client credentials to talk to the server. */
if (0 != result) {
LOG(LOG_WARNING, "initialize_tls_session_server() failed");
send_forwarding_failure(client_fd);
goto out;
}
server_session_init = 1;
LOG(LOG_DEBUG, "starting server TLS handshake");
/* Try to establish TLS handshake between us and server. */
result = gnutls_handshake(server_session);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_WARNING, "server TLS handshake failed: %s",
gnutls_strerror(result));
send_forwarding_failure(client_fd);
goto out;
}
server_session_started = 1;
LOG(LOG_DEBUG, "server TLS handshake finished");
/* Make sure the server certificate is valid and known. */
if (0 != verify_tls_connection(server_session, host)) {
LOG(LOG_ERROR, "server certificate validation failed!");
/* We send the error message over our TLS connection to the client,
* but with an invalid certificate. */
validation_failed = 1;
}
/* Initialize TLS server credentials to talk to the client. */
result = initialize_tls_session_client(client_socket,
/* use special host if the server
* certificate was invalid */
(validation_failed) ? "invalid"
: host,
&client_session,
&client_x509_cred);
if (0 != result) {
LOG(LOG_WARNING, "initialize_tls_session_client() failed");
send_forwarding_failure(client_fd);
goto out;
}
client_session_init = 1;
/* 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);
LOG(LOG_DEBUG, "starting client TLS handshake");
/* Try to establish TLS handshake between client and us. */
result = gnutls_handshake(client_session);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_WARNING, "client TLS handshake failed: %s",
gnutls_strerror(result));
send_forwarding_failure(client_fd);
goto out;
}
client_session_started = 1;
LOG(LOG_DEBUG, "client TLS handshake finished");
/* Tell the client that the verification failed. Shouldn't be necessary as
* the client should terminate the connection because he received the
* invalid certificate but better be sure. */
if (validation_failed) {
tls_send_invalid_cert_message(client_session);
goto out;
}
LOG(LOG_DEBUG, "transferring data");
/* Proxy data between client and server until one suite is done (EOF or
* error). */
transfer_data_tls(client_socket, server_socket,
client_session, server_session);
LOG(LOG_DEBUG, "finished transferring data");
out:
/* Close TLS sessions if necessary. Use GNUTLS_SHUT_RDWR so the data is
* reliable transmitted. */
if (0 != server_session_started) {
gnutls_bye(server_session, GNUTLS_SHUT_RDWR);
}
if (0 != client_session_started) {
gnutls_bye(client_session, GNUTLS_SHUT_RDWR);
}
if (0 != server_session_init) {
gnutls_deinit(server_session);
gnutls_certificate_free_credentials(server_x509_cred);
}
if (0 != client_session_init) {
gnutls_deinit(client_session);
gnutls_certificate_free_cas(client_x509_cred);
gnutls_certificate_free_keys(client_x509_cred);
gnutls_certificate_free_credentials(client_x509_cred);
}
/* Close connection to server/proxy. */
if (NULL != server_fd) {
fclose(server_fd);
} else if (-1 != server_socket) {
close(server_socket);
}
LOG(LOG_DEBUG, "connection to server closed");
/* Close connection to client. */
if (NULL != client_fd) {
fclose(client_fd);
} else {
close(client_socket);
}
LOG(LOG_DEBUG, "connection to client closed");
LOG(LOG_DEBUG, "connection finished");
}
static int initialize_tls_session_client(int peer_socket,
const char *hostname,
gnutls_session_t *session,
gnutls_certificate_credentials_t *x509_cred) {
int result;
int use_invalid_cert;
char path[1024];
/* The "invalid" hostname is special. If it's used we send an invalid
* certificate to let the client know something is wrong. */
use_invalid_cert = 0 == strcmp(hostname, "invalid");
/* Hostname too long. */
if (sizeof(path) - strlen(PROXY_SERVER_CERT_FORMAT) <= strlen(hostname)) {
LOG(LOG_WARNING,
"initialize_tls_session_client(): hostname too long: '%s'",
hostname);
return -1;
}
/* Try to prevent path traversals in hostnames. */
if (NULL != strstr(hostname, "..")) {
LOG(LOG_WARNING,
"initialize_tls_session_client(): possible path traversal: '%s'",
hostname);
return -1;
}
snprintf(path, sizeof(path), PROXY_SERVER_CERT_FORMAT, hostname);
result = gnutls_certificate_allocate_credentials(x509_cred);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_client(): \
gnutls_certificate_allocate_credentials(): %s",
gnutls_strerror(result));
return -1;
}
/* Load proxy CA file, this CA "list" is send to the client. */
if (!use_invalid_cert) {
result = gnutls_certificate_set_x509_trust_file(*x509_cred,
PROXY_CA_FILE,
GNUTLS_X509_FMT_PEM);
/* If the invalid hostname was specified do nothing, we use a self-signed
* certificate in this case. */
} else {
result = 1;
}
if (0 >= result) {
LOG(LOG_ERROR,
"initialize_tls_session_client(): can't read CA file: '%s'",
PROXY_CA_FILE);
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
/* And certificate for this website and proxy's private key. */
if (!use_invalid_cert) {
result = gnutls_certificate_set_x509_key_file(*x509_cred,
path, PROXY_KEY_FILE,
GNUTLS_X509_FMT_PEM);
/* If the invalid hostname was specified load our special "invalid"
* certificate. */
} else {
result = gnutls_certificate_set_x509_key_file(*x509_cred,
PROXY_INVALID_CERT_FILE,
PROXY_KEY_FILE,
GNUTLS_X509_FMT_PEM);
}
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_client(): \
can't read server certificate ('%s') or key file ('%s'): %s",
path, PROXY_KEY_FILE, gnutls_strerror(result));
gnutls_certificate_free_credentials(*x509_cred);
/* Could be a missing certificate. */
return -2;
}
gnutls_certificate_set_dh_params(*x509_cred, tls_dh_params);
result = gnutls_init(session, GNUTLS_SERVER);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_client(): gnutls_init(): %s",
gnutls_strerror(result));
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
result = gnutls_priority_set(*session, tls_priority_cache);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_client(): gnutls_priority_set(): %s",
gnutls_strerror(result));
gnutls_deinit(*session);
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
result = gnutls_credentials_set(*session,
GNUTLS_CRD_CERTIFICATE, *x509_cred);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_client(): gnutls_credentials_set(): %s",
gnutls_strerror(result));
gnutls_deinit(*session);
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
return 0;
}
static int initialize_tls_session_server(int peer_socket,
gnutls_session_t *session,
gnutls_certificate_credentials_t *x509_cred) {
int result;
result = gnutls_certificate_allocate_credentials(x509_cred);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_server(): \
gnutls_certificate_allocate_credentials(): %s",
gnutls_strerror(result));
return -1;
}
result = gnutls_init(session, GNUTLS_CLIENT);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_server(): gnutls_init(): %s",
gnutls_strerror(result));
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
gnutls_priority_set(*session, tls_priority_cache);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_server(): gnutls_priority_set(): %s",
gnutls_strerror(result));
gnutls_deinit(*session);
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
result = gnutls_credentials_set(*session,
GNUTLS_CRD_CERTIFICATE, *x509_cred);
if (GNUTLS_E_SUCCESS != result) {
LOG(LOG_ERROR,
"initialize_tls_session_server(): gnutls_credentials_set(): %s",
gnutls_strerror(result));
gnutls_deinit(*session);
gnutls_certificate_free_credentials(*x509_cred);
return -1;
}
gnutls_transport_set_ptr(*session, (gnutls_transport_ptr_t)peer_socket);
return 0;
}
/* Read HTTP request line and headers (ignored).
*
* On success 0 is returned, -1 on client error, -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)) {
LOG_PERROR(LOG_WARNING, "read_http_request(): fgets()");
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)) {
LOG_PERROR(LOG_WARNING, "read_http_request(): fgets()");
return -1;
}
return 0;
}
static void send_bad_request(FILE *client_fd) {
fprintf(client_fd, "HTTP/1.0 400 Bad Request\r\n");
fprintf(client_fd, "\r\n");
}
static void send_forwarding_failure(FILE *client_fd) {
fprintf(client_fd, "HTTP/1.0 503 Forwarding failure\r\n");
fprintf(client_fd, "\r\n");
}
static void tls_send_invalid_cert_message(gnutls_session_t session) {
gnutls_record_send(session, "HTTP/1.0 500 Internal Server Error\r\n", 36);
gnutls_record_send(session, "\r\n", 2);
}
#if 0
/* 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, -1 /* no timeout */);
if (result < 0) {
LOG_PERROR(LOG_ERROR, "transfer_data(): 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) {
LOG_PERROR(LOG_WARNING, "read_from_write_to(): read()");
return -1;
}
/* EOF */
if (0 == size_read) {
return -1;
}
size_written = write(to, buffer, (size_t)size_read);
if (0 > size_written) {
LOG_PERROR(LOG_WARNING, "read_from_write_to(): write()");
return -1;
}
if (size_read != size_written) {
LOG(LOG_ERROR, "read_from_write_to(): only written %ld of %ld bytes!",
(long int)size_written, (long int)size_read);
return -1;
}
return 0;
}
#endif
/* Transfer data between client and server TLS connection until one closes the
* connection. */
static void transfer_data_tls(int client, int server,
gnutls_session_t client_session,
gnutls_session_t server_session) {
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, -1 /* no timeout */);
if (result < 0) {
LOG_PERROR(LOG_ERROR, "transfer_data(): poll()");
return;
}
/* Data available from client. */
if (fds[0].revents & POLLIN || fds[0].revents & POLLPRI) {
if (0 != read_from_write_to_tls(client_session, server_session)) {
/* EOF (or other error) */
break;
}
}
/* Data available from server. */
if (fds[1].revents & POLLIN || fds[1].revents & POLLPRI) {
if (0 != read_from_write_to_tls(server_session, client_session)) {
/* 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 session from and write to session to. */
static int read_from_write_to_tls(gnutls_session_t from,
gnutls_session_t to) {
size_t size;
ssize_t size_read;
ssize_t size_written;
char buffer[16384];
/* Get maximum possible buffer size. */
size = gnutls_record_get_max_size(from);
LOG(LOG_DEBUG, "read_from_write_to_tls(): suggested buffer size: %ld",
(long int)size);
if (size > gnutls_record_get_max_size(to)) {
size = gnutls_record_get_max_size(to);
}
if (size > sizeof(buffer)) {
size = sizeof(buffer);
}
LOG(LOG_DEBUG, "read_from_write_to_tls(): used buffer size: %ld",
(long int)size);
size_read = gnutls_record_recv(from, buffer, size);
if (0 > size_read) {
LOG(LOG_WARNING, "read_from_write_to_tls(): gnutls_record_recv(): %s",
gnutls_strerror((int)size_read));
return -1;
}
/* EOF */
if (0 == size_read) {
return -1;
}
size_written = gnutls_record_send(to, buffer, (size_t)size_read);
if (0 > size_written) {
LOG(LOG_WARNING, "read_from_write_to_tls(): gnutls_record_send(): %s",
gnutls_strerror((int)size_written));
return -1;
}
if (size_read != size_written) {
LOG(LOG_ERROR, "read_from_write_to_tls(): only written %ld of %ld bytes!",
(long int)size_written, (long int)size_read);
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) {
LOG_PERROR(LOG_WARNING, "connect_to_host(): 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) {
LOG_PERROR(LOG_DEBUG, "connect_to_host(): socket(), trying next");
continue;
}
if (-1 != connect(server_socket, server->ai_addr,
server->ai_addrlen)) {
break;
}
LOG_PERROR(LOG_DEBUG, "connect_to_host(): connect(), trying next");
close(server_socket);
}
/* Make sure we free the result from getaddrinfo(). */
freeaddrinfo(gai_result);
if (NULL == server) {
LOG_PERROR(LOG_WARNING, "connect_to_host(): no server found, abort");
return -1;
}
return server_socket;
}
/* Parse HTTP CONNECT request string and save its parameters.
*
* The following format is expected: "CONNECT host:port HTTP/1.x".
*
* 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;
}