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/*
* Dropbear - a SSH2 server
*
* Copyright (c) 2002,2003 Matt Johnston
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
#include "includes.h"
#ifndef DISABLE_X11FWD
#include "x11fwd.h"
#include "session.h"
#include "ssh.h"
#include "dbutil.h"
#include "chansession.h"
#include "channel.h"
#include "packet.h"
#include "buffer.h"
#include "auth.h"
#define X11BASEPORT 6000
#define X11BINDBASE 6010
static void x11accept(struct Listener* listener, int sock);
static int bindport(int fd);
static int send_msg_channel_open_x11(int fd, struct sockaddr_in* addr);
/* called as a request for a session channel, sets up listening X11 */
/* returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
int x11req(struct ChanSess * chansess) {
int fd;
if (!svr_pubkey_allows_x11fwd()) {
return DROPBEAR_FAILURE;
}
/* we already have an x11 connection */
if (chansess->x11listener != NULL) {
return DROPBEAR_FAILURE;
}
chansess->x11singleconn = buf_getbool(ses.payload);
chansess->x11authprot = buf_getstring(ses.payload, NULL);
chansess->x11authcookie = buf_getstring(ses.payload, NULL);
chansess->x11screennum = buf_getint(ses.payload);
/* create listening socket */
fd = socket(PF_INET, SOCK_STREAM, 0);
if (fd < 0) {
goto fail;
}
/* allocate port and bind */
chansess->x11port = bindport(fd);
if (chansess->x11port < 0) {
goto fail;
}
/* listen */
if (listen(fd, 20) < 0) {
goto fail;
}
/* set non-blocking */
setnonblocking(fd);
/* listener code will handle the socket now.
* No cleanup handler needed, since listener_remove only happens
* from our cleanup anyway */
chansess->x11listener = new_listener( &fd, 1, 0, chansess, x11accept, NULL);
if (chansess->x11listener == NULL) {
goto fail;
}
return DROPBEAR_SUCCESS;
fail:
/* cleanup */
m_free(chansess->x11authprot);
m_free(chansess->x11authcookie);
close(fd);
return DROPBEAR_FAILURE;
}
/* accepts a new X11 socket */
/* returns DROPBEAR_FAILURE or DROPBEAR_SUCCESS */
static void x11accept(struct Listener* listener, int sock) {
int fd;
struct sockaddr_in addr;
int len;
int ret;
struct ChanSess * chansess = (struct ChanSess *)(listener->typedata);
len = sizeof(addr);
fd = accept(sock, (struct sockaddr*)&addr, &len);
if (fd < 0) {
return;
}
/* if single-connection we close it up */
if (chansess->x11singleconn) {
x11cleanup(chansess);
}
ret = send_msg_channel_open_x11(fd, &addr);
if (ret == DROPBEAR_FAILURE) {
close(fd);
}
}
/* This is called after switching to the user, and sets up the xauth
* and environment variables. */
void x11setauth(struct ChanSess *chansess) {
char display[20]; /* space for "localhost:12345.123" */
FILE * authprog = NULL;
int val;
if (chansess->x11listener == NULL) {
return;
}
/* create the DISPLAY string */
val = snprintf(display, sizeof(display), "localhost:%d.%d",
chansess->x11port - X11BASEPORT, chansess->x11screennum);
if (val < 0 || val >= (int)sizeof(display)) {
/* string was truncated */
return;
}
addnewvar("DISPLAY", display);
/* create the xauth string */
val = snprintf(display, sizeof(display), "unix:%d.%d",
chansess->x11port - X11BASEPORT, chansess->x11screennum);
if (val < 0 || val >= (int)sizeof(display)) {
/* string was truncated */
return;
}
/* popen is a nice function - code is strongly based on OpenSSH's */
authprog = popen(XAUTH_COMMAND, "w");
if (authprog) {
fprintf(authprog, "add %s %s %s\n",
display, chansess->x11authprot, chansess->x11authcookie);
pclose(authprog);
} else {
fprintf(stderr, "Failed to run %s\n", XAUTH_COMMAND);
}
}
void x11cleanup(struct ChanSess *chansess) {
m_free(chansess->x11authprot);
m_free(chansess->x11authcookie);
TRACE(("chansess %x", chansess))
if (chansess->x11listener != NULL) {
remove_listener(chansess->x11listener);
chansess->x11listener = NULL;
}
}
static const struct ChanType chan_x11 = {
0, /* sepfds */
"x11",
NULL, /* inithandler */
NULL, /* checkclose */
NULL, /* reqhandler */
NULL /* closehandler */
};
static int send_msg_channel_open_x11(int fd, struct sockaddr_in* addr) {
char* ipstring = NULL;
if (send_msg_channel_open_init(fd, &chan_x11) == DROPBEAR_SUCCESS) {
ipstring = inet_ntoa(addr->sin_addr);
buf_putstring(ses.writepayload, ipstring, strlen(ipstring));
buf_putint(ses.writepayload, addr->sin_port);
encrypt_packet();
return DROPBEAR_SUCCESS;
} else {
return DROPBEAR_FAILURE;
}
}
/* returns the port bound to, or -1 on failure.
* Will attempt to bind to a port X11BINDBASE (6010 usually) or upwards */
static int bindport(int fd) {
struct sockaddr_in addr;
uint16_t port;
memset((void*)&addr, 0x0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
/* if we can't find one in 2000 ports free, something's wrong */
for (port = X11BINDBASE; port < X11BINDBASE + 2000; port++) {
addr.sin_port = htons(port);
if (bind(fd, (struct sockaddr*)&addr,
sizeof(struct sockaddr_in)) == 0) {
/* success */
return port;
}
if (errno == EADDRINUSE) {
/* try the next port */
continue;
}
/* otherwise it was an error we don't know about */
dropbear_log(LOG_DEBUG, "Failed to bind x11 socket");
break;
}
return -1;
}
#endif /* DROPBEAR_X11FWD */
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