+/*
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+/* close() */
+#include <unistd.h>
+/* getaddrinfo() */
+#include <netdb.h>
+/* poll() */
+#include <poll.h>
+
+#include "connection.h"
+#include "tlsproxy.h"
+
+
+/* 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
+
+
+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);
+
+
+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, -1 /* no timeout */);
+ 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", (long int)size_read,
+ (long int)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;
+}