diff options
Diffstat (limited to 'crypto/openssh/mux.c')
| -rw-r--r-- | crypto/openssh/mux.c | 728 |
1 files changed, 728 insertions, 0 deletions
diff --git a/crypto/openssh/mux.c b/crypto/openssh/mux.c new file mode 100644 index 0000000..79f8376 --- /dev/null +++ b/crypto/openssh/mux.c @@ -0,0 +1,728 @@ +/* $OpenBSD: mux.c,v 1.7 2008/06/13 17:21:20 dtucker Exp $ */ +/* + * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ + +/* ssh session multiplexing support */ + +#include "includes.h" + +/* + * TODO: + * 1. partial reads in muxserver_accept_control (maybe make channels + * from accepted connections) + * 2. Better signalling from master to slave, especially passing of + * error messages + * 3. Better fall-back from mux slave error to new connection. + * 3. Add/delete forwardings via slave + * 4. ExitOnForwardingFailure (after #3 obviously) + * 5. Maybe extension mechanisms for multi-X11/multi-agent forwarding + * 6. Document the mux mini-protocol somewhere. + * 7. Support ~^Z in mux slaves. + * 8. Inspect or control sessions in master. + * 9. If we ever support the "signal" channel request, send signals on + * sessions in master. + */ + +#include <sys/types.h> +#include <sys/param.h> +#include <sys/stat.h> +#include <sys/socket.h> +#include <sys/un.h> + +#include <errno.h> +#include <fcntl.h> +#include <signal.h> +#include <stdarg.h> +#include <stddef.h> +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> +#ifdef HAVE_PATHS_H +#include <paths.h> +#endif + +#ifdef HAVE_UTIL_H +# include <util.h> +#endif + +#ifdef HAVE_LIBUTIL_H +# include <libutil.h> +#endif + +#include "openbsd-compat/sys-queue.h" +#include "xmalloc.h" +#include "log.h" +#include "ssh.h" +#include "pathnames.h" +#include "misc.h" +#include "match.h" +#include "buffer.h" +#include "channels.h" +#include "msg.h" +#include "packet.h" +#include "monitor_fdpass.h" +#include "sshpty.h" +#include "key.h" +#include "readconf.h" +#include "clientloop.h" + +/* from ssh.c */ +extern int tty_flag; +extern Options options; +extern int stdin_null_flag; +extern char *host; +int subsystem_flag; +extern Buffer command; + +/* Context for session open confirmation callback */ +struct mux_session_confirm_ctx { + int want_tty; + int want_subsys; + int want_x_fwd; + int want_agent_fwd; + Buffer cmd; + char *term; + struct termios tio; + char **env; +}; + +/* fd to control socket */ +int muxserver_sock = -1; + +/* Multiplexing control command */ +u_int muxclient_command = 0; + +/* Set when signalled. */ +static volatile sig_atomic_t muxclient_terminate = 0; + +/* PID of multiplex server */ +static u_int muxserver_pid = 0; + + +/* ** Multiplexing master support */ + +/* Prepare a mux master to listen on a Unix domain socket. */ +void +muxserver_listen(void) +{ + struct sockaddr_un addr; + mode_t old_umask; + int addr_len; + + if (options.control_path == NULL || + options.control_master == SSHCTL_MASTER_NO) + return; + + debug("setting up multiplex master socket"); + + memset(&addr, '\0', sizeof(addr)); + addr.sun_family = AF_UNIX; + addr_len = offsetof(struct sockaddr_un, sun_path) + + strlen(options.control_path) + 1; + + if (strlcpy(addr.sun_path, options.control_path, + sizeof(addr.sun_path)) >= sizeof(addr.sun_path)) + fatal("ControlPath too long"); + + if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) + fatal("%s socket(): %s", __func__, strerror(errno)); + + old_umask = umask(0177); + if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) { + muxserver_sock = -1; + if (errno == EINVAL || errno == EADDRINUSE) { + error("ControlSocket %s already exists, " + "disabling multiplexing", options.control_path); + close(muxserver_sock); + muxserver_sock = -1; + xfree(options.control_path); + options.control_path = NULL; + options.control_master = SSHCTL_MASTER_NO; + return; + } else + fatal("%s bind(): %s", __func__, strerror(errno)); + } + umask(old_umask); + + if (listen(muxserver_sock, 64) == -1) + fatal("%s listen(): %s", __func__, strerror(errno)); + + set_nonblock(muxserver_sock); +} + +/* Callback on open confirmation in mux master for a mux client session. */ +static void +mux_session_confirm(int id, void *arg) +{ + struct mux_session_confirm_ctx *cctx = arg; + const char *display; + Channel *c; + int i; + + if (cctx == NULL) + fatal("%s: cctx == NULL", __func__); + if ((c = channel_lookup(id)) == NULL) + fatal("%s: no channel for id %d", __func__, id); + + display = getenv("DISPLAY"); + if (cctx->want_x_fwd && options.forward_x11 && display != NULL) { + char *proto, *data; + /* Get reasonable local authentication information. */ + client_x11_get_proto(display, options.xauth_location, + options.forward_x11_trusted, &proto, &data); + /* Request forwarding with authentication spoofing. */ + debug("Requesting X11 forwarding with authentication spoofing."); + x11_request_forwarding_with_spoofing(id, display, proto, data); + /* XXX wait for reply */ + } + + if (cctx->want_agent_fwd && options.forward_agent) { + debug("Requesting authentication agent forwarding."); + channel_request_start(id, "auth-agent-req@openssh.com", 0); + packet_send(); + } + + client_session2_setup(id, cctx->want_tty, cctx->want_subsys, + cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env); + + c->open_confirm_ctx = NULL; + buffer_free(&cctx->cmd); + xfree(cctx->term); + if (cctx->env != NULL) { + for (i = 0; cctx->env[i] != NULL; i++) + xfree(cctx->env[i]); + xfree(cctx->env); + } + xfree(cctx); +} + +/* + * Accept a connection on the mux master socket and process the + * client's request. Returns flag indicating whether mux master should + * begin graceful close. + */ +int +muxserver_accept_control(void) +{ + Buffer m; + Channel *c; + int client_fd, new_fd[3], ver, allowed, window, packetmax; + socklen_t addrlen; + struct sockaddr_storage addr; + struct mux_session_confirm_ctx *cctx; + char *cmd; + u_int i, j, len, env_len, mux_command, flags, escape_char; + uid_t euid; + gid_t egid; + int start_close = 0; + + /* + * Accept connection on control socket + */ + memset(&addr, 0, sizeof(addr)); + addrlen = sizeof(addr); + if ((client_fd = accept(muxserver_sock, + (struct sockaddr*)&addr, &addrlen)) == -1) { + error("%s accept: %s", __func__, strerror(errno)); + return 0; + } + + if (getpeereid(client_fd, &euid, &egid) < 0) { + error("%s getpeereid failed: %s", __func__, strerror(errno)); + close(client_fd); + return 0; + } + if ((euid != 0) && (getuid() != euid)) { + error("control mode uid mismatch: peer euid %u != uid %u", + (u_int) euid, (u_int) getuid()); + close(client_fd); + return 0; + } + + /* XXX handle asynchronously */ + unset_nonblock(client_fd); + + /* Read command */ + buffer_init(&m); + if (ssh_msg_recv(client_fd, &m) == -1) { + error("%s: client msg_recv failed", __func__); + close(client_fd); + buffer_free(&m); + return 0; + } + if ((ver = buffer_get_char(&m)) != SSHMUX_VER) { + error("%s: wrong client version %d", __func__, ver); + buffer_free(&m); + close(client_fd); + return 0; + } + + allowed = 1; + mux_command = buffer_get_int(&m); + flags = buffer_get_int(&m); + + buffer_clear(&m); + + switch (mux_command) { + case SSHMUX_COMMAND_OPEN: + if (options.control_master == SSHCTL_MASTER_ASK || + options.control_master == SSHCTL_MASTER_AUTO_ASK) + allowed = ask_permission("Allow shared connection " + "to %s? ", host); + /* continue below */ + break; + case SSHMUX_COMMAND_TERMINATE: + if (options.control_master == SSHCTL_MASTER_ASK || + options.control_master == SSHCTL_MASTER_AUTO_ASK) + allowed = ask_permission("Terminate shared connection " + "to %s? ", host); + if (allowed) + start_close = 1; + /* FALLTHROUGH */ + case SSHMUX_COMMAND_ALIVE_CHECK: + /* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */ + buffer_clear(&m); + buffer_put_int(&m, allowed); + buffer_put_int(&m, getpid()); + if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) { + error("%s: client msg_send failed", __func__); + close(client_fd); + buffer_free(&m); + return start_close; + } + buffer_free(&m); + close(client_fd); + return start_close; + default: + error("Unsupported command %d", mux_command); + buffer_free(&m); + close(client_fd); + return 0; + } + + /* Reply for SSHMUX_COMMAND_OPEN */ + buffer_clear(&m); + buffer_put_int(&m, allowed); + buffer_put_int(&m, getpid()); + if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) { + error("%s: client msg_send failed", __func__); + close(client_fd); + buffer_free(&m); + return 0; + } + + if (!allowed) { + error("Refused control connection"); + close(client_fd); + buffer_free(&m); + return 0; + } + + buffer_clear(&m); + if (ssh_msg_recv(client_fd, &m) == -1) { + error("%s: client msg_recv failed", __func__); + close(client_fd); + buffer_free(&m); + return 0; + } + if ((ver = buffer_get_char(&m)) != SSHMUX_VER) { + error("%s: wrong client version %d", __func__, ver); + buffer_free(&m); + close(client_fd); + return 0; + } + + cctx = xcalloc(1, sizeof(*cctx)); + cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0; + cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0; + cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0; + cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0; + cctx->term = buffer_get_string(&m, &len); + escape_char = buffer_get_int(&m); + + cmd = buffer_get_string(&m, &len); + buffer_init(&cctx->cmd); + buffer_append(&cctx->cmd, cmd, strlen(cmd)); + + env_len = buffer_get_int(&m); + env_len = MIN(env_len, 4096); + debug3("%s: receiving %d env vars", __func__, env_len); + if (env_len != 0) { + cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env)); + for (i = 0; i < env_len; i++) + cctx->env[i] = buffer_get_string(&m, &len); + cctx->env[i] = NULL; + } + + debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__, + cctx->want_tty, cctx->want_subsys, cmd); + xfree(cmd); + + /* Gather fds from client */ + for(i = 0; i < 3; i++) { + if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) { + error("%s: failed to receive fd %d from slave", + __func__, i); + for (j = 0; j < i; j++) + close(new_fd[j]); + for (j = 0; j < env_len; j++) + xfree(cctx->env[j]); + if (env_len > 0) + xfree(cctx->env); + xfree(cctx->term); + buffer_free(&cctx->cmd); + close(client_fd); + xfree(cctx); + return 0; + } + } + + debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__, + new_fd[0], new_fd[1], new_fd[2]); + + /* Try to pick up ttymodes from client before it goes raw */ + if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1) + error("%s: tcgetattr: %s", __func__, strerror(errno)); + + /* This roundtrip is just for synchronisation of ttymodes */ + buffer_clear(&m); + if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) { + error("%s: client msg_send failed", __func__); + close(client_fd); + close(new_fd[0]); + close(new_fd[1]); + close(new_fd[2]); + buffer_free(&m); + xfree(cctx->term); + if (env_len != 0) { + for (i = 0; i < env_len; i++) + xfree(cctx->env[i]); + xfree(cctx->env); + } + return 0; + } + buffer_free(&m); + + /* enable nonblocking unless tty */ + if (!isatty(new_fd[0])) + set_nonblock(new_fd[0]); + if (!isatty(new_fd[1])) + set_nonblock(new_fd[1]); + if (!isatty(new_fd[2])) + set_nonblock(new_fd[2]); + + set_nonblock(client_fd); + + window = CHAN_SES_WINDOW_DEFAULT; + packetmax = CHAN_SES_PACKET_DEFAULT; + if (cctx->want_tty) { + window >>= 1; + packetmax >>= 1; + } + + c = channel_new("session", SSH_CHANNEL_OPENING, + new_fd[0], new_fd[1], new_fd[2], window, packetmax, + CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0); + + c->ctl_fd = client_fd; + if (cctx->want_tty && escape_char != 0xffffffff) { + channel_register_filter(c->self, + client_simple_escape_filter, NULL, + client_filter_cleanup, + client_new_escape_filter_ctx((int)escape_char)); + } + + debug3("%s: channel_new: %d", __func__, c->self); + + channel_send_open(c->self); + channel_register_open_confirm(c->self, mux_session_confirm, cctx); + return 0; +} + +/* ** Multiplexing client support */ + +/* Exit signal handler */ +static void +control_client_sighandler(int signo) +{ + muxclient_terminate = signo; +} + +/* + * Relay signal handler - used to pass some signals from mux client to + * mux master. + */ +static void +control_client_sigrelay(int signo) +{ + int save_errno = errno; + + if (muxserver_pid > 1) + kill(muxserver_pid, signo); + + errno = save_errno; +} + +/* Check mux client environment variables before passing them to mux master. */ +static int +env_permitted(char *env) +{ + int i, ret; + char name[1024], *cp; + + if ((cp = strchr(env, '=')) == NULL || cp == env) + return (0); + ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env); + if (ret <= 0 || (size_t)ret >= sizeof(name)) + fatal("env_permitted: name '%.100s...' too long", env); + + for (i = 0; i < options.num_send_env; i++) + if (match_pattern(name, options.send_env[i])) + return (1); + + return (0); +} + +/* Multiplex client main loop. */ +void +muxclient(const char *path) +{ + struct sockaddr_un addr; + int i, r, fd, sock, exitval[2], num_env, addr_len; + Buffer m; + char *term; + extern char **environ; + 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]); +} |
