diff options
-rw-r--r-- | ChangeLog | 23 | ||||
-rw-r--r-- | channels.c | 214 | ||||
-rw-r--r-- | channels.h | 18 | ||||
-rw-r--r-- | clientloop.c | 35 | ||||
-rw-r--r-- | clientloop.h | 12 | ||||
-rw-r--r-- | mux.c | 1840 | ||||
-rw-r--r-- | nchan.c | 21 | ||||
-rw-r--r-- | ssh.c | 22 |
8 files changed, 1676 insertions, 509 deletions
@@ -8,6 +8,29 @@ [roaming_client.c] s/long long unsigned/unsigned long long/, from tim via portable (Id sync only, change already in portable) + - djm@cvs.openbsd.org 2010/01/26 01:28:35 + [channels.c channels.h clientloop.c clientloop.h mux.c nchan.c ssh.c] + rewrite ssh(1) multiplexing code to a more sensible protocol. + + The new multiplexing code uses channels for the listener and + accepted control sockets to make the mux master non-blocking, so + no stalls when processing messages from a slave. + + avoid use of fatal() in mux master protocol parsing so an errant slave + process cannot take down a running master. + + implement requesting of port-forwards over multiplexed sessions. Any + port forwards requested by the slave are added to those the master has + established. + + add support for stdio forwarding ("ssh -W host:port ...") in mux slaves. + + document master/slave mux protocol so that other tools can use it to + control a running ssh(1). Note: there are no guarantees that this + protocol won't be incompatibly changed (though it is versioned). + + feedback Salvador Fandino, dtucker@ + channel changes ok markus@ 20100122 - (tim) [configure.ac] Due to constraints in Windows Sockets in terms of @@ -1,4 +1,4 @@ -/* $OpenBSD: channels.c,v 1.301 2010/01/11 01:39:46 dtucker Exp $ */ +/* $OpenBSD: channels.c,v 1.302 2010/01/26 01:28:35 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland @@ -239,7 +239,6 @@ channel_register_fds(Channel *c, int rfd, int wfd, int efd, c->rfd = rfd; c->wfd = wfd; c->sock = (rfd == wfd) ? rfd : -1; - c->ctl_fd = -1; /* XXX: set elsewhere */ c->efd = efd; c->extended_usage = extusage; @@ -328,6 +327,9 @@ channel_new(char *ctype, int type, int rfd, int wfd, int efd, c->output_filter = NULL; c->filter_ctx = NULL; c->filter_cleanup = NULL; + c->ctl_chan = -1; + c->mux_rcb = NULL; + c->mux_ctx = NULL; c->delayed = 1; /* prevent call to channel_post handler */ TAILQ_INIT(&c->status_confirms); debug("channel %d: new [%s]", found, remote_name); @@ -370,11 +372,10 @@ channel_close_fd(int *fdp) static void channel_close_fds(Channel *c) { - debug3("channel %d: close_fds r %d w %d e %d c %d", - c->self, c->rfd, c->wfd, c->efd, c->ctl_fd); + debug3("channel %d: close_fds r %d w %d e %d", + c->self, c->rfd, c->wfd, c->efd); channel_close_fd(&c->sock); - channel_close_fd(&c->ctl_fd); channel_close_fd(&c->rfd); channel_close_fd(&c->wfd); channel_close_fd(&c->efd); @@ -400,8 +401,6 @@ channel_free(Channel *c) if (c->sock != -1) shutdown(c->sock, SHUT_RDWR); - if (c->ctl_fd != -1) - shutdown(c->ctl_fd, SHUT_RDWR); channel_close_fds(c); buffer_free(&c->input); buffer_free(&c->output); @@ -523,6 +522,7 @@ channel_still_open(void) case SSH_CHANNEL_X11_LISTENER: case SSH_CHANNEL_PORT_LISTENER: case SSH_CHANNEL_RPORT_LISTENER: + case SSH_CHANNEL_MUX_LISTENER: case SSH_CHANNEL_CLOSED: case SSH_CHANNEL_AUTH_SOCKET: case SSH_CHANNEL_DYNAMIC: @@ -536,6 +536,7 @@ channel_still_open(void) case SSH_CHANNEL_OPENING: case SSH_CHANNEL_OPEN: case SSH_CHANNEL_X11_OPEN: + case SSH_CHANNEL_MUX_CLIENT: return 1; case SSH_CHANNEL_INPUT_DRAINING: case SSH_CHANNEL_OUTPUT_DRAINING: @@ -567,6 +568,8 @@ channel_find_open(void) case SSH_CHANNEL_X11_LISTENER: case SSH_CHANNEL_PORT_LISTENER: case SSH_CHANNEL_RPORT_LISTENER: + case SSH_CHANNEL_MUX_LISTENER: + case SSH_CHANNEL_MUX_CLIENT: case SSH_CHANNEL_OPENING: case SSH_CHANNEL_CONNECTING: case SSH_CHANNEL_ZOMBIE: @@ -617,6 +620,8 @@ channel_open_message(void) case SSH_CHANNEL_CLOSED: case SSH_CHANNEL_AUTH_SOCKET: case SSH_CHANNEL_ZOMBIE: + case SSH_CHANNEL_MUX_CLIENT: + case SSH_CHANNEL_MUX_LISTENER: continue; case SSH_CHANNEL_LARVAL: case SSH_CHANNEL_OPENING: @@ -627,12 +632,12 @@ channel_open_message(void) case SSH_CHANNEL_INPUT_DRAINING: case SSH_CHANNEL_OUTPUT_DRAINING: snprintf(buf, sizeof buf, - " #%d %.300s (t%d r%d i%d/%d o%d/%d fd %d/%d cfd %d)\r\n", + " #%d %.300s (t%d r%d i%d/%d o%d/%d fd %d/%d cc %d)\r\n", c->self, c->remote_name, c->type, c->remote_id, c->istate, buffer_len(&c->input), c->ostate, buffer_len(&c->output), - c->rfd, c->wfd, c->ctl_fd); + c->rfd, c->wfd, c->ctl_chan); buffer_append(&buffer, buf, strlen(buf)); continue; default: @@ -839,9 +844,6 @@ channel_pre_open(Channel *c, fd_set *readset, fd_set *writeset) FD_SET(c->efd, readset); } /* XXX: What about efd? races? */ - if (compat20 && c->ctl_fd != -1 && - c->istate == CHAN_INPUT_OPEN && c->ostate == CHAN_OUTPUT_OPEN) - FD_SET(c->ctl_fd, readset); } /* ARGSUSED */ @@ -986,6 +988,28 @@ channel_pre_x11_open(Channel *c, fd_set *readset, fd_set *writeset) } } +static void +channel_pre_mux_client(Channel *c, fd_set *readset, fd_set *writeset) +{ + if (c->istate == CHAN_INPUT_OPEN && + buffer_check_alloc(&c->input, CHAN_RBUF)) + FD_SET(c->rfd, readset); + if (c->istate == CHAN_INPUT_WAIT_DRAIN) { + /* clear buffer immediately (discard any partial packet) */ + buffer_clear(&c->input); + chan_ibuf_empty(c); + /* Start output drain. XXX just kill chan? */ + chan_rcvd_oclose(c); + } + if (c->ostate == CHAN_OUTPUT_OPEN || + c->ostate == CHAN_OUTPUT_WAIT_DRAIN) { + if (buffer_len(&c->output) > 0) + FD_SET(c->wfd, writeset); + else if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN) + chan_obuf_empty(c); + } +} + /* try to decode a socks4 header */ /* ARGSUSED */ static int @@ -1218,19 +1242,14 @@ channel_decode_socks5(Channel *c, fd_set *readset, fd_set *writeset) } Channel * -channel_connect_stdio_fwd(const char *host_to_connect, u_short port_to_connect) +channel_connect_stdio_fwd(const char *host_to_connect, u_short port_to_connect, + int in, int out) { Channel *c; - int in, out; debug("channel_connect_stdio_fwd %s:%d", host_to_connect, port_to_connect); - in = dup(STDIN_FILENO); - out = dup(STDOUT_FILENO); - if (in < 0 || out < 0) - fatal("channel_connect_stdio_fwd: dup() in/out failed"); - c = channel_new("stdio-forward", SSH_CHANNEL_OPENING, in, out, -1, CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "stdio-forward", /*nonblock*/0); @@ -1749,36 +1768,6 @@ channel_handle_efd(Channel *c, fd_set *readset, fd_set *writeset) return 1; } -/* ARGSUSED */ -static int -channel_handle_ctl(Channel *c, fd_set *readset, fd_set *writeset) -{ - char buf[16]; - int len; - - /* Monitor control fd to detect if the slave client exits */ - if (c->ctl_fd != -1 && FD_ISSET(c->ctl_fd, readset)) { - len = read(c->ctl_fd, buf, sizeof(buf)); - if (len < 0 && - (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) - return 1; - if (len <= 0) { - debug2("channel %d: ctl read<=0", c->self); - if (c->type != SSH_CHANNEL_OPEN) { - debug2("channel %d: not open", c->self); - chan_mark_dead(c); - return -1; - } else { - chan_read_failed(c); - chan_write_failed(c); - } - return -1; - } else - fatal("%s: unexpected data on ctl fd", __func__); - } - return 1; -} - static int channel_check_window(Channel *c) { @@ -1809,10 +1798,131 @@ channel_post_open(Channel *c, fd_set *readset, fd_set *writeset) if (!compat20) return; channel_handle_efd(c, readset, writeset); - channel_handle_ctl(c, readset, writeset); channel_check_window(c); } +static u_int +read_mux(Channel *c, u_int need) +{ + char buf[CHAN_RBUF]; + int len; + u_int rlen; + + if (buffer_len(&c->input) < need) { + rlen = need - buffer_len(&c->input); + len = read(c->rfd, buf, MIN(rlen, CHAN_RBUF)); + if (len <= 0) { + if (errno != EINTR && errno != EAGAIN) { + debug2("channel %d: ctl read<=0 rfd %d len %d", + c->self, c->rfd, len); + chan_read_failed(c); + return 0; + } + } else + buffer_append(&c->input, buf, len); + } + return buffer_len(&c->input); +} + +static void +channel_post_mux_client(Channel *c, fd_set *readset, fd_set *writeset) +{ + u_int need; + ssize_t len; + + if (!compat20) + fatal("%s: entered with !compat20", __func__); + + if (c->rfd != -1 && FD_ISSET(c->rfd, readset) && + (c->istate == CHAN_INPUT_OPEN || + c->istate == CHAN_INPUT_WAIT_DRAIN)) { + /* + * Don't not read past the precise end of packets to + * avoid disrupting fd passing. + */ + if (read_mux(c, 4) < 4) /* read header */ + return; + need = get_u32(buffer_ptr(&c->input)); +#define CHANNEL_MUX_MAX_PACKET (256 * 1024) + if (need > CHANNEL_MUX_MAX_PACKET) { + debug2("channel %d: packet too big %u > %u", + c->self, CHANNEL_MUX_MAX_PACKET, need); + chan_rcvd_oclose(c); + return; + } + if (read_mux(c, need + 4) < need + 4) /* read body */ + return; + if (c->mux_rcb(c) != 0) { + debug("channel %d: mux_rcb failed", c->self); + chan_mark_dead(c); + return; + } + } + + if (c->wfd != -1 && FD_ISSET(c->wfd, writeset) && + buffer_len(&c->output) > 0) { + len = write(c->wfd, buffer_ptr(&c->output), + buffer_len(&c->output)); + if (len < 0 && (errno == EINTR || errno == EAGAIN)) + return; + if (len <= 0) { + chan_mark_dead(c); + return; + } + buffer_consume(&c->output, len); + } +} + +static void +channel_post_mux_listener(Channel *c, fd_set *readset, fd_set *writeset) +{ + Channel *nc; + struct sockaddr_storage addr; + socklen_t addrlen; + int newsock; + uid_t euid; + gid_t egid; + + if (!FD_ISSET(c->sock, readset)) + return; + + debug("multiplexing control connection"); + + /* + * Accept connection on control socket + */ + memset(&addr, 0, sizeof(addr)); + addrlen = sizeof(addr); + if ((newsock = accept(c->sock, (struct sockaddr*)&addr, + &addrlen)) == -1) { + error("%s accept: %s", __func__, strerror(errno)); + return; + } + + if (getpeereid(newsock, &euid, &egid) < 0) { + error("%s getpeereid failed: %s", __func__, + strerror(errno)); + close(newsock); + return; + } + if ((euid != 0) && (getuid() != euid)) { + error("multiplex uid mismatch: peer euid %u != uid %u", + (u_int)euid, (u_int)getuid()); + close(newsock); + return; + } + nc = channel_new("multiplex client", SSH_CHANNEL_MUX_CLIENT, + newsock, newsock, -1, c->local_window_max, + c->local_maxpacket, 0, "mux-control", 1); + nc->mux_rcb = c->mux_rcb; + debug3("%s: new mux channel %d fd %d", __func__, + nc->self, nc->sock); + /* establish state */ + nc->mux_rcb(nc); + /* mux state transitions must not elicit protocol messages */ + nc->flags |= CHAN_LOCAL; +} + /* ARGSUSED */ static void channel_post_output_drain_13(Channel *c, fd_set *readset, fd_set *writeset) @@ -1841,6 +1951,8 @@ channel_handler_init_20(void) channel_pre[SSH_CHANNEL_AUTH_SOCKET] = &channel_pre_listener; channel_pre[SSH_CHANNEL_CONNECTING] = &channel_pre_connecting; channel_pre[SSH_CHANNEL_DYNAMIC] = &channel_pre_dynamic; + channel_pre[SSH_CHANNEL_MUX_LISTENER] = &channel_pre_listener; + channel_pre[SSH_CHANNEL_MUX_CLIENT] = &channel_pre_mux_client; channel_post[SSH_CHANNEL_OPEN] = &channel_post_open; channel_post[SSH_CHANNEL_PORT_LISTENER] = &channel_post_port_listener; @@ -1849,6 +1961,8 @@ channel_handler_init_20(void) channel_post[SSH_CHANNEL_AUTH_SOCKET] = &channel_post_auth_listener; channel_post[SSH_CHANNEL_CONNECTING] = &channel_post_connecting; channel_post[SSH_CHANNEL_DYNAMIC] = &channel_post_open; + channel_post[SSH_CHANNEL_MUX_LISTENER] = &channel_post_mux_listener; + channel_post[SSH_CHANNEL_MUX_CLIENT] = &channel_post_mux_client; } static void @@ -1,4 +1,4 @@ -/* $OpenBSD: channels.h,v 1.102 2010/01/11 01:39:46 dtucker Exp $ */ +/* $OpenBSD: channels.h,v 1.103 2010/01/26 01:28:35 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> @@ -53,7 +53,9 @@ #define SSH_CHANNEL_CONNECTING 12 #define SSH_CHANNEL_DYNAMIC 13 #define SSH_CHANNEL_ZOMBIE 14 /* Almost dead. */ -#define SSH_CHANNEL_MAX_TYPE 15 +#define SSH_CHANNEL_MUX_LISTENER 15 /* Listener for mux conn. */ +#define SSH_CHANNEL_MUX_CLIENT 16 /* Conn. to mux slave */ +#define SSH_CHANNEL_MAX_TYPE 17 struct Channel; typedef struct Channel Channel; @@ -81,6 +83,9 @@ struct channel_connect { struct addrinfo *ai, *aitop; }; +/* Callbacks for mux channels back into client-specific code */ +typedef int mux_callback_fn(struct Channel *); + struct Channel { int type; /* channel type/state */ int self; /* my own channel identifier */ @@ -92,7 +97,7 @@ struct Channel { int wfd; /* write fd */ int efd; /* extended fd */ int sock; /* sock fd */ - int ctl_fd; /* control fd (client sharing) */ + int ctl_chan; /* control channel (multiplexed connections) */ int isatty; /* rfd is a tty */ int wfd_isatty; /* wfd is a tty */ int client_tty; /* (client) TTY has been requested */ @@ -142,6 +147,10 @@ struct Channel { /* non-blocking connect */ struct channel_connect connect_ctx; + + /* multiplexing protocol hook, called for each packet received */ + mux_callback_fn *mux_rcb; + void *mux_ctx; }; #define CHAN_EXTENDED_IGNORE 0 @@ -172,6 +181,7 @@ struct Channel { #define CHAN_CLOSE_RCVD 0x02 #define CHAN_EOF_SENT 0x04 #define CHAN_EOF_RCVD 0x08 +#define CHAN_LOCAL 0x10 #define CHAN_RBUF 16*1024 @@ -243,7 +253,7 @@ void channel_clear_adm_permitted_opens(void); void channel_print_adm_permitted_opens(void); int channel_input_port_forward_request(int, int); Channel *channel_connect_to(const char *, u_short, char *, char *); -Channel *channel_connect_stdio_fwd(const char*, u_short); +Channel *channel_connect_stdio_fwd(const char*, u_short, int, int); Channel *channel_connect_by_listen_address(u_short, char *, char *); int channel_request_remote_forwarding(const char *, u_short, const char *, u_short); diff --git a/clientloop.c b/clientloop.c index 5793a6e9..05f4720a 100644 --- a/clientloop.c +++ b/clientloop.c @@ -1,4 +1,4 @@ -/* $OpenBSD: clientloop.c,v 1.216 2010/01/09 05:04:24 djm Exp $ */ +/* $OpenBSD: clientloop.c,v 1.217 2010/01/26 01:28:35 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland @@ -121,7 +121,7 @@ extern int stdin_null_flag; extern int no_shell_flag; /* Control socket */ -extern int muxserver_sock; +extern int muxserver_sock; /* XXX use mux_client_cleanup() instead */ /* * Name of the host we are connecting to. This is the name given on the @@ -146,7 +146,7 @@ static volatile sig_atomic_t received_signal = 0; static int in_non_blocking_mode = 0; /* Common data for the client loop code. */ -static volatile sig_atomic_t quit_pending; /* Set non-zero to quit the loop. */ +volatile sig_atomic_t quit_pending; /* Set non-zero to quit the loop. */ static int escape_char1; /* Escape character. (proto1 only) */ static int escape_pending1; /* Last character was an escape (proto1 only) */ static int last_was_cr; /* Last character was a newline. */ @@ -564,9 +564,6 @@ client_wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, if (packet_have_data_to_write()) FD_SET(connection_out, *writesetp); - if (muxserver_sock != -1) - FD_SET(muxserver_sock, *readsetp); - /* * Wait for something to happen. This will suspend the process until * some selected descriptor can be read, written, or has some other @@ -695,7 +692,7 @@ client_status_confirm(int type, Channel *c, void *ctx) /* XXX supress on mux _client_ quietmode */ tochan = options.log_level >= SYSLOG_LEVEL_ERROR && - c->ctl_fd != -1 && c->extended_usage == CHAN_EXTENDED_WRITE; + c->ctl_chan != -1 && c->extended_usage == CHAN_EXTENDED_WRITE; if (type == SSH2_MSG_CHANNEL_SUCCESS) { debug2("%s request accepted on channel %d", @@ -839,6 +836,7 @@ process_cmdline(void) while (isspace(*++s)) ; + /* XXX update list of forwards in options */ if (delete) { cancel_port = 0; cancel_host = hpdelim(&s); /* may be NULL */ @@ -936,7 +934,7 @@ process_escapes(Channel *c, Buffer *bin, Buffer *bout, Buffer *berr, escape_char); buffer_append(berr, string, strlen(string)); - if (c && c->ctl_fd != -1) { + if (c && c->ctl_chan != -1) { chan_read_failed(c); chan_write_failed(c); return 0; @@ -946,7 +944,7 @@ process_escapes(Channel *c, Buffer *bin, Buffer *bout, Buffer *berr, case 'Z' - 64: /* XXX support this for mux clients */ - if (c && c->ctl_fd != -1) { + if (c && c->ctl_chan != -1) { noescape: snprintf(string, sizeof string, "%c%c escape not available to " @@ -991,7 +989,7 @@ process_escapes(Channel *c, Buffer *bin, Buffer *bout, Buffer *berr, continue; case '&': - if (c && c->ctl_fd != -1) + if (c && c->ctl_chan != -1) goto noescape; /* * Detach the program (continue to serve @@ -1042,7 +1040,7 @@ process_escapes(Channel *c, Buffer *bin, Buffer *bout, Buffer *berr, continue; case '?': - if (c && c->ctl_fd != -1) { + if (c && c->ctl_chan != -1) { snprintf(string, sizeof string, "%c?\r\n\ Supported escape sequences:\r\n\ @@ -1091,7 +1089,7 @@ Supported escape sequences:\r\n\ continue; case 'C': - if (c && c->ctl_fd != -1) + if (c && c->ctl_chan != -1) goto noescape; process_cmdline(); continue; @@ -1327,8 +1325,6 @@ client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id) connection_in = packet_get_connection_in(); connection_out = packet_get_connection_out(); max_fd = MAX(connection_in, connection_out); - if (muxserver_sock != -1) - max_fd = MAX(max_fd, muxserver_sock); if (!compat20) { /* enable nonblocking unless tty */ @@ -1446,12 +1442,6 @@ client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id) /* Buffer input from the connection. */ client_process_net_input(readset); - /* Accept control connections. */ - if (muxserver_sock != -1 &&FD_ISSET(muxserver_sock, readset)) { - if (muxserver_accept_control()) - quit_pending = 1; - } - if (quit_pending) break; @@ -1859,9 +1849,8 @@ client_input_channel_req(int type, u_int32_t seq, void *ctxt) chan_rcvd_eow(c); } else if (strcmp(rtype, "exit-status") == 0) { exitval = packet_get_int(); - if (c->ctl_fd != -1) { - /* Dispatch to mux client */ - atomicio(vwrite, c->ctl_fd, &exitval, sizeof(exitval)); + if (c->ctl_chan != -1) { + mux_exit_message(c, exitval); success = 1; } else if (id == session_ident) { /* Record exit value of local session */ diff --git a/clientloop.h b/clientloop.h index 8bb874b3..0b8257b9 100644 --- a/clientloop.h +++ b/clientloop.h @@ -1,4 +1,4 @@ -/* $OpenBSD: clientloop.h,v 1.22 2008/06/12 15:19:17 djm Exp $ */ +/* $OpenBSD: clientloop.h,v 1.23 2010/01/26 01:28:35 djm Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> @@ -56,18 +56,14 @@ typedef void global_confirm_cb(int, u_int32_t seq, void *); void client_register_global_confirm(global_confirm_cb *, void *); /* Multiplexing protocol version */ -#define SSHMUX_VER 2 +#define SSHMUX_VER 4 /* Multiplexing control protocol flags */ #define SSHMUX_COMMAND_OPEN 1 /* Open new connection */ #define SSHMUX_COMMAND_ALIVE_CHECK 2 /* Check master is alive */ #define SSHMUX_COMMAND_TERMINATE 3 /* Ask master to exit */ - -#define SSHMUX_FLAG_TTY (1) /* Request tty on open */ -#define SSHMUX_FLAG_SUBSYS (1<<1) /* Subsystem request on open */ -#define SSHMUX_FLAG_X11_FWD (1<<2) /* Request X11 forwarding */ -#define SSHMUX_FLAG_AGENT_FWD (1<<3) /* Request agent forwarding */ +#define SSHMUX_COMMAND_STDIO_FWD 4 /* Open stdio fwd (ssh -W) */ void muxserver_listen(void); -int muxserver_accept_control(void); void muxclient(const char *); +void mux_exit_message(Channel *, int); @@ -1,4 +1,4 @@ -/* $OpenBSD: mux.c,v 1.9 2010/01/09 05:04:24 djm Exp $ */ +/* $OpenBSD: mux.c,v 1.10 2010/01/26 01:28:35 djm Exp $ */ /* * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org> * @@ -17,25 +17,21 @@ /* 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 + * - 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. + * - Better fall-back from mux slave error to new connection. + * - ExitOnForwardingFailure + * - Maybe extension mechanisms for multi-X11/multi-agent forwarding + * - Support ~^Z in mux slaves. + * - Inspect or control sessions in master. + * - If we ever support the "signal" channel request, send signals on + * sessions in master. */ +#include "includes.h" + #include <sys/types.h> #include <sys/param.h> #include <sys/stat.h> @@ -55,6 +51,14 @@ #include <paths.h> #endif +#ifdef HAVE_POLL_H +#include <poll.h> +#else +# ifdef HAVE_SYS_POLL_H +# include <sys/poll.h> +# endif +#endif + #ifdef HAVE_UTIL_H # include <util.h> #endif @@ -88,13 +92,16 @@ extern int stdin_null_flag; extern char *host; extern int subsystem_flag; extern Buffer command; +extern volatile sig_atomic_t quit_pending; +extern char *stdio_forward_host; +extern int stdio_forward_port; /* 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; + u_int want_tty; + u_int want_subsys; + u_int want_x_fwd; + u_int want_agent_fwd; Buffer cmd; char *term; struct termios tio; @@ -104,6 +111,9 @@ struct mux_session_confirm_ctx { /* fd to control socket */ int muxserver_sock = -1; +/* client request id */ +u_int muxclient_request_id = 0; + /* Multiplexing control command */ u_int muxclient_command = 0; @@ -113,16 +123,823 @@ static volatile sig_atomic_t muxclient_terminate = 0; /* PID of multiplex server */ static u_int muxserver_pid = 0; +static Channel *mux_listener_channel = NULL; + +struct mux_master_state { + int hello_rcvd; +}; + +/* mux protocol messages */ +#define MUX_MSG_HELLO 0x00000001 +#define MUX_C_NEW_SESSION 0x10000002 +#define MUX_C_ALIVE_CHECK 0x10000004 +#define MUX_C_TERMINATE 0x10000005 +#define MUX_C_OPEN_FWD 0x10000006 +#define MUX_C_CLOSE_FWD 0x10000007 +#define MUX_C_NEW_STDIO_FWD 0x10000008 +#define MUX_S_OK 0x80000001 +#define MUX_S_PERMISSION_DENIED 0x80000002 +#define MUX_S_FAILURE 0x80000003 +#define MUX_S_EXIT_MESSAGE 0x80000004 +#define MUX_S_ALIVE 0x80000005 +#define MUX_S_SESSION_OPENED 0x80000006 + +/* type codes for MUX_C_OPEN_FWD and MUX_C_CLOSE_FWD */ +#define MUX_FWD_LOCAL 1 +#define MUX_FWD_REMOTE 2 +#define MUX_FWD_DYNAMIC 3 + +static void mux_session_confirm(int, void *); + +static int process_mux_master_hello(u_int, Channel *, Buffer *, Buffer *); +static int process_mux_new_session(u_int, Channel *, Buffer *, Buffer *); +static int process_mux_alive_check(u_int, Channel *, Buffer *, Buffer *); +static int process_mux_terminate(u_int, Channel *, Buffer *, Buffer *); +static int process_mux_open_fwd(u_int, Channel *, Buffer *, Buffer *); +static int process_mux_close_fwd(u_int, Channel *, Buffer *, Buffer *); +static int process_mux_stdio_fwd(u_int, Channel *, Buffer *, Buffer *); + +static const struct { + u_int type; + int (*handler)(u_int, Channel *, Buffer *, Buffer *); +} mux_master_handlers[] = { + { MUX_MSG_HELLO, process_mux_master_hello }, + { MUX_C_NEW_SESSION, process_mux_new_session }, + { MUX_C_ALIVE_CHECK, process_mux_alive_check }, + { MUX_C_TERMINATE, process_mux_terminate }, + { MUX_C_OPEN_FWD, process_mux_open_fwd }, + { MUX_C_CLOSE_FWD, process_mux_close_fwd }, + { MUX_C_NEW_STDIO_FWD, process_mux_stdio_fwd }, + { 0, NULL } +}; + +/* Cleanup callback fired on closure of mux slave _session_ channel */ +/* ARGSUSED */ +static void +mux_master_session_cleanup_cb(int cid, void *unused) +{ + Channel *cc, *c = channel_by_id(cid); + + debug3("%s: entering for channel %d", __func__, cid); + if (c == NULL) + fatal("%s: channel_by_id(%i) == NULL", __func__, cid); + if (c->ctl_chan != -1) { + if ((cc = channel_by_id(c->ctl_chan)) == NULL) + fatal("%s: channel %d missing control channel %d", + __func__, c->self, c->ctl_chan); + c->ctl_chan = -1; + cc->remote_id = -1; + chan_rcvd_oclose(cc); + } + channel_cancel_cleanup(c->self); +} + +/* Cleanup callback fired on closure of mux slave _control_ channel */ +/* ARGSUSED */ +static void +mux_master_control_cleanup_cb(int cid, void *unused) +{ + Channel *sc, *c = channel_by_id(cid); + + debug3("%s: entering for channel %d", __func__, cid); + if (c == NULL) + fatal("%s: channel_by_id(%i) == NULL", __func__, cid); + if (c->remote_id != -1) { + if ((sc = channel_by_id(c->remote_id)) == NULL) + debug2("%s: channel %d n session channel %d", + __func__, c->self, c->remote_id); + c->remote_id = -1; + sc->ctl_chan = -1; + chan_mark_dead(sc); + } + channel_cancel_cleanup(c->self); +} + +/* 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)) { + error("env_permitted: name '%.100s...' too long", env); + return 0; + } + + for (i = 0; i < options.num_send_env; i++) + if (match_pattern(name, options.send_env[i])) + return 1; + + return 0; +} + +/* Mux master protocol message handlers */ + +static int +process_mux_master_hello(u_int rid, Channel *c, Buffer *m, Buffer *r) +{ + u_int ver; + struct mux_master_state *state = (struct mux_master_state *)c->mux_ctx; + + if (state == NULL) + fatal("%s: channel %d: c->mux_ctx == NULL", __func__, c->self); + if (state->hello_rcvd) { + error("%s: HELLO received twice", __func__); + return -1; + } + if (buffer_get_int_ret(&ver, m) != 0) { + malf: + error("%s: malformed message", __func__); + return -1; + } + if (ver != SSHMUX_VER) { + error("Unsupported multiplexing protocol version %d " + "(expected %d)", ver, SSHMUX_VER); + return -1; + } + debug2("%s: channel %d slave version %u", __func__, c->self, ver); + + /* No extensions are presently defined */ + while (buffer_len(m) > 0) { + char *name = buffer_get_string_ret(m, NULL); + char *value = buffer_get_string_ret(m, NULL); + + if (name == NULL || value == NULL) { + if (name != NULL) + xfree(name); + goto malf; + } + debug2("Unrecognised slave extension \"%s\"", name); + xfree(name); + xfree(value); + } + state->hello_rcvd = 1; + return 0; +} + +static int +process_mux_new_session(u_int rid, Channel *c, Buffer *m, Buffer *r) +{ + Channel *nc; + struct mux_session_confirm_ctx *cctx; + char *reserved, *cmd, *cp; + u_int i, j, len, env_len, escape_char, window, packetmax; + int new_fd[3]; + + /* Reply for SSHMUX_COMMAND_OPEN */ + cctx = xcalloc(1, sizeof(*cctx)); + cctx->term = NULL; + cmd = reserved = NULL; + if ((reserved = buffer_get_string_ret(m, NULL)) == NULL || + buffer_get_int_ret(&cctx->want_tty, m) != 0 || + buffer_get_int_ret(&cctx->want_x_fwd, m) != 0 || + buffer_get_int_ret(&cctx->want_agent_fwd, m) != 0 || + buffer_get_int_ret(&cctx->want_subsys, m) != 0 || + buffer_get_int_ret(&escape_char, m) != 0 || + (cctx->term = buffer_get_string_ret(m, &len)) == NULL || + (cmd = buffer_get_string_ret(m, &len)) == NULL) { + malf: + if (cmd != NULL) + xfree(cmd); + if (reserved != NULL) + xfree(reserved); + if (cctx->term != NULL) + xfree(cctx->term); + error("%s: malformed message", __func__); + return -1; + } + xfree(reserved); + reserved = NULL; + + cctx->env = NULL; + env_len = 0; + while (buffer_len(m) > 0) { +#define MUX_MAX_ENV_VARS 4096 + if ((cp = buffer_get_string_ret(m, &len)) == NULL) { + xfree(cmd); + goto malf; + } + if (!env_permitted(cp)) { + xfree(cp); + continue; + } + cctx->env = xrealloc(cctx->env, env_len + 2, + sizeof(*cctx->env)); + cctx->env[env_len++] = cp; + cctx->env[env_len] = NULL; + if (env_len > MUX_MAX_ENV_VARS) { + error(">%d environment variables received, ignoring " + "additional", MUX_MAX_ENV_VARS); + break; + } + } + + debug2("%s: channel %d: request tty %d, X %d, agent %d, subsys %d, " + "term \"%s\", cmd \"%s\", env %u", __func__, c->self, + cctx->want_tty, cctx->want_x_fwd, cctx->want_agent_fwd, + cctx->want_subsys, cctx->term, cmd, env_len); + + buffer_init(&cctx->cmd); + buffer_append(&cctx->cmd, cmd, strlen(cmd)); + xfree(cmd); + cmd = NULL; + + /* Gather fds from client */ + for(i = 0; i < 3; i++) { + if ((new_fd[i] = mm_receive_fd(c->sock)) == -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); + xfree(cctx); + + /* prepare reply */ + buffer_put_int(r, MUX_S_FAILURE); + buffer_put_int(r, rid); + buffer_put_cstring(r, + "did not receive file descriptors"); + return -1; + } + } + + debug3("%s: got fds stdin %d, stdout %d, stderr %d", __func__, + new_fd[0], new_fd[1], new_fd[2]); + + /* XXX support multiple child sessions in future */ + if (c->remote_id != -1) { + debug2("%s: session already open", __func__); + /* prepare reply */ + buffer_put_int(r, MUX_S_FAILURE); + buffer_put_int(r, rid); + buffer_put_cstring(r, "Multiple sessions not supported"); + cleanup: + close(new_fd[0]); + close(new_fd[1]); + close(new_fd[2]); + xfree(cctx->term); + if (env_len != 0) { + for (i = 0; i < env_len; i++) + xfree(cctx->env[i]); + xfree(cctx->env); + } + buffer_free(&cctx->cmd); + return 0; + } + + if (options.control_master == SSHCTL_MASTER_ASK || + options.control_master == SSHCTL_MASTER_AUTO_ASK) { + if (!ask_permission("Allow shared connection to %s? ", host)) { + debug2("%s: session refused by user", __func__); + /* prepare reply */ + buffer_put_int(r, MUX_S_PERMISSION_DENIED); + buffer_put_int(r, rid); + buffer_put_cstring(r, "Permission denied"); + goto cleanup; + } + } + + /* Try to pick up ttymodes from client before it goes raw */ + if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1) |