redsocks/utils.c

/* redsocks - transparent TCP-to-proxy redirector
 * Copyright (C) 2007-2018 Leonid Evdokimov <leon@darkk.net.ru>
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License.  You may obtain a copy
 * of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

#include <unistd.h>
#include <errno.h>
#include <assert.h>
#include <fcntl.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "log.h"
#include "base.h"
#include "utils.h"
#include "redsocks.h" // for redsocks_close
#include "libc-compat.h"

int red_recv_udp_pkt(int fd, char *buf, size_t buflen, struct sockaddr_in *inaddr, struct sockaddr_in *toaddr)
{
	socklen_t addrlen = sizeof(*inaddr);
	ssize_t pktlen;
	struct msghdr msg;
	struct iovec io;
	char control[1024];

	memset(&msg, 0, sizeof(msg));
	msg.msg_name = inaddr;
	msg.msg_namelen = sizeof(*inaddr);
	msg.msg_iov = &io;
	msg.msg_iovlen = 1;
	msg.msg_control = control;
	msg.msg_controllen = sizeof(control);
	io.iov_base = buf;
	io.iov_len = buflen;

	pktlen = recvmsg(fd, &msg, 0);
	if (pktlen == -1) {
		log_errno(LOG_WARNING, "recvfrom");
		return -1;
	}

	if (toaddr) {
		memset(toaddr, 0, sizeof(*toaddr));
		for (struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
			if (
				cmsg->cmsg_level == SOL_IP &&
				cmsg->cmsg_type == IP_ORIGDSTADDR &&
				cmsg->cmsg_len >= CMSG_LEN(sizeof(*toaddr))
			) {
				struct sockaddr_in* cmsgaddr = (struct sockaddr_in*)CMSG_DATA(cmsg);
				char buf[RED_INET_ADDRSTRLEN];
				log_error(LOG_DEBUG, "IP_ORIGDSTADDR: %s", red_inet_ntop(cmsgaddr, buf, sizeof(buf)));
				memcpy(toaddr, cmsgaddr, sizeof(*toaddr));
			}
			else {
				log_error(LOG_WARNING, "unexepcted cmsg (level,type) = (%d,%d)",
					cmsg->cmsg_level, cmsg->cmsg_type);
			}
		}
		if (toaddr->sin_family != AF_INET) {
			log_error(LOG_WARNING, "(SOL_IP, IP_ORIGDSTADDR) not found");
			return -1;
		}
	}

	if (addrlen != sizeof(*inaddr)) {
		log_error(LOG_WARNING, "unexpected address length %u instead of %zu", addrlen, sizeof(*inaddr));
		return -1;
	}

	if (pktlen >= buflen) {
		char buf[RED_INET_ADDRSTRLEN];
		log_error(LOG_WARNING, "wow! Truncated udp packet of size %zd from %s! impossible! dropping it...",
		          pktlen, red_inet_ntop(inaddr, buf, sizeof(buf)));
		return -1;
	}

	return pktlen;
}

uint32_t red_randui32()
{
	uint32_t ret;
	evutil_secure_rng_get_bytes(&ret, sizeof(ret));
	return ret;
}

time_t redsocks_time(time_t *t)
{
	time_t retval;
	retval = time(t);
	if (retval == ((time_t) -1))
		log_errno(LOG_WARNING, "time");
	return retval;
}

int redsocks_gettimeofday(struct timeval *tv)
{
	int retval = gettimeofday(tv, NULL);
	if (retval != 0)
		log_errno(LOG_WARNING, "gettimeofday");
	return retval;
}

char *redsocks_evbuffer_readline(struct evbuffer *buf)
{
#if _EVENT_NUMERIC_VERSION >= 0x02000000
	return evbuffer_readln(buf, NULL, EVBUFFER_EOL_CRLF);
#else
	return evbuffer_readline(buf);
#endif
}

int red_socket_client(int type)
{
	int fd = -1;
	int error;

	fd = socket(AF_INET, type, 0);
	if (fd == -1) {
		log_errno(LOG_ERR, "socket");
		goto fail;
	}

	error = fcntl_nonblock(fd);
	if (error) {
		log_errno(LOG_ERR, "fcntl");
		goto fail;
	}

	if (type == SOCK_STREAM) {
		if (apply_tcp_keepalive(fd))
			goto fail;
	}

	return fd;

fail:
	if (fd != -1)
		redsocks_close(fd);
	return -1;
}

int red_socket_server(int type, struct sockaddr_in *bindaddr)
{
	int on = 1;
	int error;
	int fd = red_socket_client(type);
	if (fd == -1)
		goto fail;

	error = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
	if (error) {
		log_errno(LOG_ERR, "setsockopt");
		goto fail;
	}

	error = bind(fd, (struct sockaddr*)bindaddr, sizeof(*bindaddr));
	if (error) {
		log_errno(LOG_ERR, "bind");
		goto fail;
	}

	return fd;
fail:
	if (fd != -1)
		redsocks_close(fd);
	return -1;

}


struct bufferevent* red_connect_relay(struct sockaddr_in *addr, evbuffercb writecb, everrorcb errorcb, void *cbarg)
{
	struct bufferevent *retval = NULL;
	int relay_fd = -1;
	int error;

	relay_fd = red_socket_client(SOCK_STREAM);

	error = connect(relay_fd, (struct sockaddr*)addr, sizeof(*addr));
	if (error && errno != EINPROGRESS) {
		log_errno(LOG_NOTICE, "connect");
		goto fail;
	}

	retval = bufferevent_new(relay_fd, NULL, writecb, errorcb, cbarg);
	if (!retval) {
		log_errno(LOG_ERR, "bufferevent_new");
		goto fail;
	}

	relay_fd = -1;

	error = bufferevent_enable(retval, EV_WRITE); // we wait for connection...
	if (error) {
		log_errno(LOG_ERR, "bufferevent_enable");
		goto fail;
	}

	return retval;

fail:
	if (relay_fd != -1)
		redsocks_close(relay_fd);
	if (retval)
		redsocks_bufferevent_free(retval);
	return NULL;
}

int red_socket_geterrno(struct bufferevent *buffev)
{
	int error;
	int pseudo_errno;
	socklen_t optlen = sizeof(pseudo_errno);

	assert(event_get_fd(&buffev->ev_read) == event_get_fd(&buffev->ev_write));

	error = getsockopt(event_get_fd(&buffev->ev_read), SOL_SOCKET, SO_ERROR, &pseudo_errno, &optlen);
	if (error) {
		log_errno(LOG_ERR, "getsockopt");
		return -1;
	}
	return pseudo_errno;
}

/** simple fcntl(2) wrapper, provides errno and all logging to caller
 * I have to use it in event-driven code because of accept(2) (see NOTES)
 * and connect(2) (see ERRORS about EINPROGRESS)
 */
int fcntl_nonblock(int fd)
{
	int error;
	int flags;

	flags = fcntl(fd, F_GETFL);
	if (flags == -1)
		return -1;

	error = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
	if (error)
		return -1;

	return 0;
}

int red_is_socket_connected_ok(struct bufferevent *buffev)
{
	int pseudo_errno = red_socket_geterrno(buffev);

	if (pseudo_errno == -1) {
		return 0;
	}
	else if (pseudo_errno) {
		errno = pseudo_errno;
		log_errno(LOG_NOTICE, "connect");
		return 0;
	}
	else {
		return 1;
	}
}

char *red_inet_ntop(const struct sockaddr_in* sa, char* buffer, size_t buffer_size)
{
	const char *retval = 0;
	size_t len = 0;
	uint16_t port;
	const char placeholder[] = "???:???";

	assert(buffer_size >= RED_INET_ADDRSTRLEN);

	memset(buffer, 0, buffer_size);
	if (sa->sin_family == AF_INET) {
		retval = inet_ntop(AF_INET, &sa->sin_addr, buffer, buffer_size);
		port = ((struct sockaddr_in*)sa)->sin_port;
	}
	else if (sa->sin_family == AF_INET6) {
		retval = inet_ntop(AF_INET6, &((const struct sockaddr_in6*)sa)->sin6_addr, buffer, buffer_size);
		port = ((struct sockaddr_in6*)sa)->sin6_port;
	}
	if (retval) {
		assert(retval == buffer);
		len = strlen(retval);
		snprintf(buffer + len, buffer_size - len, ":%d", ntohs(port));
	}
	else {
		strcpy(buffer, placeholder);
	}
	return buffer;
}

/* vim:set tabstop=4 softtabstop=4 shiftwidth=4: */