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47e713be94
[mux.c] Friendlier error messages for mux fallback. ok djm@
729 lines
19 KiB
C
729 lines
19 KiB
C
/* $OpenBSD: mux.c,v 1.7 2008/06/13 17:21:20 dtucker Exp $ */
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/*
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* Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/* ssh session multiplexing support */
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#include "includes.h"
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/*
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* TODO:
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* 1. partial reads in muxserver_accept_control (maybe make channels
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* from accepted connections)
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* 2. Better signalling from master to slave, especially passing of
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* error messages
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* 3. Better fall-back from mux slave error to new connection.
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* 3. Add/delete forwardings via slave
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* 4. ExitOnForwardingFailure (after #3 obviously)
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* 5. Maybe extension mechanisms for multi-X11/multi-agent forwarding
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* 6. Document the mux mini-protocol somewhere.
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* 7. Support ~^Z in mux slaves.
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* 8. Inspect or control sessions in master.
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* 9. If we ever support the "signal" channel request, send signals on
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* sessions in master.
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*/
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/stat.h>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <stdarg.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#ifdef HAVE_PATHS_H
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#include <paths.h>
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#endif
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#ifdef HAVE_UTIL_H
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# include <util.h>
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#endif
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#ifdef HAVE_LIBUTIL_H
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# include <libutil.h>
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#endif
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#include "openbsd-compat/sys-queue.h"
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#include "xmalloc.h"
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#include "log.h"
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#include "ssh.h"
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#include "pathnames.h"
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#include "misc.h"
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#include "match.h"
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#include "buffer.h"
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#include "channels.h"
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#include "msg.h"
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#include "packet.h"
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#include "monitor_fdpass.h"
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#include "sshpty.h"
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#include "key.h"
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#include "readconf.h"
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#include "clientloop.h"
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/* from ssh.c */
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extern int tty_flag;
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extern Options options;
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extern int stdin_null_flag;
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extern char *host;
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int subsystem_flag;
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extern Buffer command;
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/* Context for session open confirmation callback */
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struct mux_session_confirm_ctx {
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int want_tty;
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int want_subsys;
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int want_x_fwd;
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int want_agent_fwd;
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Buffer cmd;
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char *term;
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struct termios tio;
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char **env;
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};
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/* fd to control socket */
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int muxserver_sock = -1;
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/* Multiplexing control command */
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u_int muxclient_command = 0;
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/* Set when signalled. */
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static volatile sig_atomic_t muxclient_terminate = 0;
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/* PID of multiplex server */
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static u_int muxserver_pid = 0;
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/* ** Multiplexing master support */
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/* Prepare a mux master to listen on a Unix domain socket. */
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void
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muxserver_listen(void)
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{
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struct sockaddr_un addr;
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mode_t old_umask;
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int addr_len;
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if (options.control_path == NULL ||
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options.control_master == SSHCTL_MASTER_NO)
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return;
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debug("setting up multiplex master socket");
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memset(&addr, '\0', sizeof(addr));
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addr.sun_family = AF_UNIX;
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addr_len = offsetof(struct sockaddr_un, sun_path) +
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strlen(options.control_path) + 1;
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if (strlcpy(addr.sun_path, options.control_path,
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sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
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fatal("ControlPath too long");
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if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
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fatal("%s socket(): %s", __func__, strerror(errno));
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old_umask = umask(0177);
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if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) {
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muxserver_sock = -1;
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if (errno == EINVAL || errno == EADDRINUSE) {
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error("ControlSocket %s already exists, "
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"disabling multiplexing", options.control_path);
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close(muxserver_sock);
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muxserver_sock = -1;
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xfree(options.control_path);
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options.control_path = NULL;
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options.control_master = SSHCTL_MASTER_NO;
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return;
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} else
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fatal("%s bind(): %s", __func__, strerror(errno));
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}
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umask(old_umask);
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if (listen(muxserver_sock, 64) == -1)
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fatal("%s listen(): %s", __func__, strerror(errno));
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set_nonblock(muxserver_sock);
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}
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/* Callback on open confirmation in mux master for a mux client session. */
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static void
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mux_session_confirm(int id, void *arg)
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{
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struct mux_session_confirm_ctx *cctx = arg;
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const char *display;
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Channel *c;
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int i;
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if (cctx == NULL)
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fatal("%s: cctx == NULL", __func__);
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if ((c = channel_lookup(id)) == NULL)
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fatal("%s: no channel for id %d", __func__, id);
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display = getenv("DISPLAY");
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if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
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char *proto, *data;
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/* Get reasonable local authentication information. */
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client_x11_get_proto(display, options.xauth_location,
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options.forward_x11_trusted, &proto, &data);
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/* Request forwarding with authentication spoofing. */
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debug("Requesting X11 forwarding with authentication spoofing.");
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x11_request_forwarding_with_spoofing(id, display, proto, data);
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/* XXX wait for reply */
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}
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if (cctx->want_agent_fwd && options.forward_agent) {
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debug("Requesting authentication agent forwarding.");
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channel_request_start(id, "auth-agent-req@openssh.com", 0);
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packet_send();
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}
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client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
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cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
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c->open_confirm_ctx = NULL;
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buffer_free(&cctx->cmd);
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xfree(cctx->term);
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if (cctx->env != NULL) {
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for (i = 0; cctx->env[i] != NULL; i++)
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xfree(cctx->env[i]);
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xfree(cctx->env);
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}
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xfree(cctx);
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}
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/*
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* Accept a connection on the mux master socket and process the
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* client's request. Returns flag indicating whether mux master should
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* begin graceful close.
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*/
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int
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muxserver_accept_control(void)
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{
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Buffer m;
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Channel *c;
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int client_fd, new_fd[3], ver, allowed, window, packetmax;
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socklen_t addrlen;
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struct sockaddr_storage addr;
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struct mux_session_confirm_ctx *cctx;
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char *cmd;
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u_int i, j, len, env_len, mux_command, flags, escape_char;
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uid_t euid;
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gid_t egid;
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int start_close = 0;
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/*
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* Accept connection on control socket
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*/
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memset(&addr, 0, sizeof(addr));
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addrlen = sizeof(addr);
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if ((client_fd = accept(muxserver_sock,
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(struct sockaddr*)&addr, &addrlen)) == -1) {
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error("%s accept: %s", __func__, strerror(errno));
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return 0;
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}
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if (getpeereid(client_fd, &euid, &egid) < 0) {
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error("%s getpeereid failed: %s", __func__, strerror(errno));
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close(client_fd);
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return 0;
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}
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if ((euid != 0) && (getuid() != euid)) {
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error("control mode uid mismatch: peer euid %u != uid %u",
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(u_int) euid, (u_int) getuid());
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close(client_fd);
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return 0;
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}
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/* XXX handle asynchronously */
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unset_nonblock(client_fd);
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/* Read command */
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buffer_init(&m);
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if (ssh_msg_recv(client_fd, &m) == -1) {
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error("%s: client msg_recv failed", __func__);
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close(client_fd);
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buffer_free(&m);
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return 0;
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}
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if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
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error("%s: wrong client version %d", __func__, ver);
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buffer_free(&m);
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close(client_fd);
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return 0;
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}
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allowed = 1;
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mux_command = buffer_get_int(&m);
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flags = buffer_get_int(&m);
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buffer_clear(&m);
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switch (mux_command) {
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case SSHMUX_COMMAND_OPEN:
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if (options.control_master == SSHCTL_MASTER_ASK ||
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options.control_master == SSHCTL_MASTER_AUTO_ASK)
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allowed = ask_permission("Allow shared connection "
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"to %s? ", host);
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/* continue below */
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break;
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case SSHMUX_COMMAND_TERMINATE:
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if (options.control_master == SSHCTL_MASTER_ASK ||
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options.control_master == SSHCTL_MASTER_AUTO_ASK)
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allowed = ask_permission("Terminate shared connection "
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"to %s? ", host);
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if (allowed)
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start_close = 1;
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/* FALLTHROUGH */
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case SSHMUX_COMMAND_ALIVE_CHECK:
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/* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
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buffer_clear(&m);
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buffer_put_int(&m, allowed);
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buffer_put_int(&m, getpid());
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if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
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error("%s: client msg_send failed", __func__);
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close(client_fd);
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buffer_free(&m);
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return start_close;
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}
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buffer_free(&m);
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close(client_fd);
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return start_close;
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default:
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error("Unsupported command %d", mux_command);
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buffer_free(&m);
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close(client_fd);
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return 0;
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}
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/* Reply for SSHMUX_COMMAND_OPEN */
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buffer_clear(&m);
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buffer_put_int(&m, allowed);
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buffer_put_int(&m, getpid());
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if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
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error("%s: client msg_send failed", __func__);
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close(client_fd);
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buffer_free(&m);
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return 0;
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}
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if (!allowed) {
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error("Refused control connection");
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close(client_fd);
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buffer_free(&m);
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return 0;
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}
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buffer_clear(&m);
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if (ssh_msg_recv(client_fd, &m) == -1) {
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error("%s: client msg_recv failed", __func__);
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close(client_fd);
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buffer_free(&m);
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return 0;
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}
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if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
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error("%s: wrong client version %d", __func__, ver);
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buffer_free(&m);
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close(client_fd);
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return 0;
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}
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cctx = xcalloc(1, sizeof(*cctx));
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cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
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cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
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cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
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cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
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cctx->term = buffer_get_string(&m, &len);
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escape_char = buffer_get_int(&m);
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cmd = buffer_get_string(&m, &len);
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buffer_init(&cctx->cmd);
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buffer_append(&cctx->cmd, cmd, strlen(cmd));
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env_len = buffer_get_int(&m);
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env_len = MIN(env_len, 4096);
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debug3("%s: receiving %d env vars", __func__, env_len);
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if (env_len != 0) {
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cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
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for (i = 0; i < env_len; i++)
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cctx->env[i] = buffer_get_string(&m, &len);
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cctx->env[i] = NULL;
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}
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debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
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cctx->want_tty, cctx->want_subsys, cmd);
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xfree(cmd);
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/* Gather fds from client */
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for(i = 0; i < 3; i++) {
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if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) {
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error("%s: failed to receive fd %d from slave",
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__func__, i);
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for (j = 0; j < i; j++)
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close(new_fd[j]);
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for (j = 0; j < env_len; j++)
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xfree(cctx->env[j]);
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if (env_len > 0)
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xfree(cctx->env);
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xfree(cctx->term);
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buffer_free(&cctx->cmd);
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close(client_fd);
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xfree(cctx);
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return 0;
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}
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}
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debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
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new_fd[0], new_fd[1], new_fd[2]);
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/* Try to pick up ttymodes from client before it goes raw */
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if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
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error("%s: tcgetattr: %s", __func__, strerror(errno));
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/* This roundtrip is just for synchronisation of ttymodes */
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buffer_clear(&m);
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if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
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error("%s: client msg_send failed", __func__);
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close(client_fd);
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close(new_fd[0]);
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close(new_fd[1]);
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close(new_fd[2]);
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buffer_free(&m);
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xfree(cctx->term);
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if (env_len != 0) {
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for (i = 0; i < env_len; i++)
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xfree(cctx->env[i]);
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xfree(cctx->env);
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}
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return 0;
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}
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buffer_free(&m);
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/* enable nonblocking unless tty */
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if (!isatty(new_fd[0]))
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set_nonblock(new_fd[0]);
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if (!isatty(new_fd[1]))
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set_nonblock(new_fd[1]);
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if (!isatty(new_fd[2]))
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set_nonblock(new_fd[2]);
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set_nonblock(client_fd);
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window = CHAN_SES_WINDOW_DEFAULT;
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packetmax = CHAN_SES_PACKET_DEFAULT;
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if (cctx->want_tty) {
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window >>= 1;
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packetmax >>= 1;
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}
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c = channel_new("session", SSH_CHANNEL_OPENING,
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new_fd[0], new_fd[1], new_fd[2], window, packetmax,
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CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0);
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c->ctl_fd = client_fd;
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if (cctx->want_tty && escape_char != 0xffffffff) {
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channel_register_filter(c->self,
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client_simple_escape_filter, NULL,
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client_filter_cleanup,
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client_new_escape_filter_ctx((int)escape_char));
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}
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debug3("%s: channel_new: %d", __func__, c->self);
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channel_send_open(c->self);
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channel_register_open_confirm(c->self, mux_session_confirm, cctx);
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return 0;
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}
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/* ** Multiplexing client support */
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/* Exit signal handler */
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static void
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control_client_sighandler(int signo)
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{
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muxclient_terminate = signo;
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}
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/*
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* Relay signal handler - used to pass some signals from mux client to
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* mux master.
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*/
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static void
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control_client_sigrelay(int signo)
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{
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int save_errno = errno;
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if (muxserver_pid > 1)
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kill(muxserver_pid, signo);
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errno = save_errno;
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}
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/* Check mux client environment variables before passing them to mux master. */
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static int
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env_permitted(char *env)
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{
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int i, ret;
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char name[1024], *cp;
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if ((cp = strchr(env, '=')) == NULL || cp == env)
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return (0);
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ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
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if (ret <= 0 || (size_t)ret >= sizeof(name))
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fatal("env_permitted: name '%.100s...' too long", env);
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for (i = 0; i < options.num_send_env; i++)
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if (match_pattern(name, options.send_env[i]))
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return (1);
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return (0);
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}
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/* Multiplex client main loop. */
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void
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muxclient(const char *path)
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{
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struct sockaddr_un addr;
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int i, r, fd, sock, exitval[2], num_env, addr_len;
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Buffer m;
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char *term;
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extern char **environ;
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u_int allowed, flags;
|
|
|
|
if (muxclient_command == 0)
|
|
muxclient_command = SSHMUX_COMMAND_OPEN;
|
|
|
|
switch (options.control_master) {
|
|
case SSHCTL_MASTER_AUTO:
|
|
case SSHCTL_MASTER_AUTO_ASK:
|
|
debug("auto-mux: Trying existing master");
|
|
/* FALLTHROUGH */
|
|
case SSHCTL_MASTER_NO:
|
|
break;
|
|
default:
|
|
return;
|
|
}
|
|
|
|
memset(&addr, '\0', sizeof(addr));
|
|
addr.sun_family = AF_UNIX;
|
|
addr_len = offsetof(struct sockaddr_un, sun_path) +
|
|
strlen(path) + 1;
|
|
|
|
if (strlcpy(addr.sun_path, path,
|
|
sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
|
|
fatal("ControlPath too long");
|
|
|
|
if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
|
|
fatal("%s socket(): %s", __func__, strerror(errno));
|
|
|
|
if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
|
|
if (muxclient_command != SSHMUX_COMMAND_OPEN) {
|
|
fatal("Control socket connect(%.100s): %s", path,
|
|
strerror(errno));
|
|
}
|
|
if (errno == ENOENT)
|
|
debug("Control socket \"%.100s\" does not exist", path);
|
|
else {
|
|
error("Control socket connect(%.100s): %s", path,
|
|
strerror(errno));
|
|
}
|
|
close(sock);
|
|
return;
|
|
}
|
|
|
|
if (stdin_null_flag) {
|
|
if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
|
|
fatal("open(/dev/null): %s", strerror(errno));
|
|
if (dup2(fd, STDIN_FILENO) == -1)
|
|
fatal("dup2: %s", strerror(errno));
|
|
if (fd > STDERR_FILENO)
|
|
close(fd);
|
|
}
|
|
|
|
term = getenv("TERM");
|
|
|
|
flags = 0;
|
|
if (tty_flag)
|
|
flags |= SSHMUX_FLAG_TTY;
|
|
if (subsystem_flag)
|
|
flags |= SSHMUX_FLAG_SUBSYS;
|
|
if (options.forward_x11)
|
|
flags |= SSHMUX_FLAG_X11_FWD;
|
|
if (options.forward_agent)
|
|
flags |= SSHMUX_FLAG_AGENT_FWD;
|
|
|
|
signal(SIGPIPE, SIG_IGN);
|
|
|
|
buffer_init(&m);
|
|
|
|
/* Send our command to server */
|
|
buffer_put_int(&m, muxclient_command);
|
|
buffer_put_int(&m, flags);
|
|
if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1) {
|
|
error("%s: msg_send", __func__);
|
|
muxerr:
|
|
close(sock);
|
|
buffer_free(&m);
|
|
if (muxclient_command != SSHMUX_COMMAND_OPEN)
|
|
cleanup_exit(255);
|
|
logit("Falling back to non-multiplexed connection");
|
|
xfree(options.control_path);
|
|
options.control_path = NULL;
|
|
options.control_master = SSHCTL_MASTER_NO;
|
|
return;
|
|
}
|
|
buffer_clear(&m);
|
|
|
|
/* Get authorisation status and PID of controlee */
|
|
if (ssh_msg_recv(sock, &m) == -1) {
|
|
error("%s: Did not receive reply from master", __func__);
|
|
goto muxerr;
|
|
}
|
|
if (buffer_get_char(&m) != SSHMUX_VER) {
|
|
error("%s: Master replied with wrong version", __func__);
|
|
goto muxerr;
|
|
}
|
|
if (buffer_get_int_ret(&allowed, &m) != 0) {
|
|
error("%s: bad server reply", __func__);
|
|
goto muxerr;
|
|
}
|
|
if (allowed != 1) {
|
|
error("Connection to master denied");
|
|
goto muxerr;
|
|
}
|
|
muxserver_pid = buffer_get_int(&m);
|
|
|
|
buffer_clear(&m);
|
|
|
|
switch (muxclient_command) {
|
|
case SSHMUX_COMMAND_ALIVE_CHECK:
|
|
fprintf(stderr, "Master running (pid=%d)\r\n",
|
|
muxserver_pid);
|
|
exit(0);
|
|
case SSHMUX_COMMAND_TERMINATE:
|
|
fprintf(stderr, "Exit request sent.\r\n");
|
|
exit(0);
|
|
case SSHMUX_COMMAND_OPEN:
|
|
buffer_put_cstring(&m, term ? term : "");
|
|
if (options.escape_char == SSH_ESCAPECHAR_NONE)
|
|
buffer_put_int(&m, 0xffffffff);
|
|
else
|
|
buffer_put_int(&m, options.escape_char);
|
|
buffer_append(&command, "\0", 1);
|
|
buffer_put_cstring(&m, buffer_ptr(&command));
|
|
|
|
if (options.num_send_env == 0 || environ == NULL) {
|
|
buffer_put_int(&m, 0);
|
|
} else {
|
|
/* Pass environment */
|
|
num_env = 0;
|
|
for (i = 0; environ[i] != NULL; i++) {
|
|
if (env_permitted(environ[i]))
|
|
num_env++; /* Count */
|
|
}
|
|
buffer_put_int(&m, num_env);
|
|
for (i = 0; environ[i] != NULL && num_env >= 0; i++) {
|
|
if (env_permitted(environ[i])) {
|
|
num_env--;
|
|
buffer_put_cstring(&m, environ[i]);
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
default:
|
|
fatal("unrecognised muxclient_command %d", muxclient_command);
|
|
}
|
|
|
|
if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1) {
|
|
error("%s: msg_send", __func__);
|
|
goto muxerr;
|
|
}
|
|
|
|
if (mm_send_fd(sock, STDIN_FILENO) == -1 ||
|
|
mm_send_fd(sock, STDOUT_FILENO) == -1 ||
|
|
mm_send_fd(sock, STDERR_FILENO) == -1) {
|
|
error("%s: send fds failed", __func__);
|
|
goto muxerr;
|
|
}
|
|
|
|
/*
|
|
* Mux errors are non-recoverable from this point as the master
|
|
* has ownership of the session now.
|
|
*/
|
|
|
|
/* Wait for reply, so master has a chance to gather ttymodes */
|
|
buffer_clear(&m);
|
|
if (ssh_msg_recv(sock, &m) == -1)
|
|
fatal("%s: msg_recv", __func__);
|
|
if (buffer_get_char(&m) != SSHMUX_VER)
|
|
fatal("%s: wrong version", __func__);
|
|
buffer_free(&m);
|
|
|
|
signal(SIGHUP, control_client_sighandler);
|
|
signal(SIGINT, control_client_sighandler);
|
|
signal(SIGTERM, control_client_sighandler);
|
|
signal(SIGWINCH, control_client_sigrelay);
|
|
|
|
if (tty_flag)
|
|
enter_raw_mode();
|
|
|
|
/*
|
|
* Stick around until the controlee closes the client_fd.
|
|
* Before it does, it is expected to write this process' exit
|
|
* value (one int). This process must read the value and wait for
|
|
* the closure of the client_fd; if this one closes early, the
|
|
* multiplex master will terminate early too (possibly losing data).
|
|
*/
|
|
exitval[0] = 0;
|
|
for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) {
|
|
r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
|
|
if (r == 0) {
|
|
debug2("Received EOF from master");
|
|
break;
|
|
}
|
|
if (r == -1) {
|
|
if (errno == EINTR)
|
|
continue;
|
|
fatal("%s: read %s", __func__, strerror(errno));
|
|
}
|
|
i += r;
|
|
}
|
|
|
|
close(sock);
|
|
leave_raw_mode();
|
|
if (i > (int)sizeof(int))
|
|
fatal("%s: master returned too much data (%d > %lu)",
|
|
__func__, i, (u_long)sizeof(int));
|
|
if (muxclient_terminate) {
|
|
debug2("Exiting on signal %d", muxclient_terminate);
|
|
exitval[0] = 255;
|
|
} else if (i < (int)sizeof(int)) {
|
|
debug2("Control master terminated unexpectedly");
|
|
exitval[0] = 255;
|
|
} else
|
|
debug2("Received exit status from master %d", exitval[0]);
|
|
|
|
if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
|
|
fprintf(stderr, "Shared connection to %s closed.\r\n", host);
|
|
|
|
exit(exitval[0]);
|
|
}
|