diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 14:40:04 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 14:40:04 +0000 |
commit | 25505898530a333011f4fd5cbc841ad6b26c089c (patch) | |
tree | 333a33fdd60930bcccc3f177ed9467d535e9bac6 /serverloop.c | |
parent | Initial commit. (diff) | |
download | openssh-upstream.tar.xz openssh-upstream.zip |
Adding upstream version 1:9.2p1.upstream/1%9.2p1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'serverloop.c')
-rw-r--r-- | serverloop.c | 935 |
1 files changed, 935 insertions, 0 deletions
diff --git a/serverloop.c b/serverloop.c new file mode 100644 index 0000000..6db0916 --- /dev/null +++ b/serverloop.c @@ -0,0 +1,935 @@ +/* $OpenBSD: serverloop.c,v 1.234 2023/01/17 09:44:48 djm Exp $ */ +/* + * Author: Tatu Ylonen <ylo@cs.hut.fi> + * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland + * All rights reserved + * Server main loop for handling the interactive session. + * + * As far as I am concerned, the code I have written for this software + * can be used freely for any purpose. Any derived versions of this + * software must be clearly marked as such, and if the derived work is + * incompatible with the protocol description in the RFC file, it must be + * called by a name other than "ssh" or "Secure Shell". + * + * SSH2 support by Markus Friedl. + * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#include <sys/types.h> +#include <sys/wait.h> +#include <sys/socket.h> +#ifdef HAVE_SYS_TIME_H +# include <sys/time.h> +#endif + +#include <netinet/in.h> + +#include <errno.h> +#include <fcntl.h> +#include <pwd.h> +#include <limits.h> +#ifdef HAVE_POLL_H +#include <poll.h> +#endif +#include <signal.h> +#include <string.h> +#include <termios.h> +#include <unistd.h> +#include <stdarg.h> + +#include "openbsd-compat/sys-queue.h" +#include "xmalloc.h" +#include "packet.h" +#include "sshbuf.h" +#include "log.h" +#include "misc.h" +#include "servconf.h" +#include "canohost.h" +#include "sshpty.h" +#include "channels.h" +#include "compat.h" +#include "ssh2.h" +#include "sshkey.h" +#include "cipher.h" +#include "kex.h" +#include "hostfile.h" +#include "auth.h" +#include "session.h" +#include "dispatch.h" +#include "auth-options.h" +#include "serverloop.h" +#include "ssherr.h" + +extern ServerOptions options; + +/* XXX */ +extern Authctxt *the_authctxt; +extern struct sshauthopt *auth_opts; +extern int use_privsep; + +static int no_more_sessions = 0; /* Disallow further sessions. */ + +static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ + +/* Cleanup on signals (!use_privsep case only) */ +static volatile sig_atomic_t received_sigterm = 0; + +/* prototypes */ +static void server_init_dispatch(struct ssh *); + +/* requested tunnel forwarding interface(s), shared with session.c */ +char *tun_fwd_ifnames = NULL; + +/* returns 1 if bind to specified port by specified user is permitted */ +static int +bind_permitted(int port, uid_t uid) +{ + if (use_privsep) + return 1; /* allow system to decide */ + if (port < IPPORT_RESERVED && uid != 0) + return 0; + return 1; +} + +/*ARGSUSED*/ +static void +sigchld_handler(int sig) +{ + child_terminated = 1; +} + +/*ARGSUSED*/ +static void +sigterm_handler(int sig) +{ + received_sigterm = sig; +} + +static void +client_alive_check(struct ssh *ssh) +{ + char remote_id[512]; + int r, channel_id; + + /* timeout, check to see how many we have had */ + if (options.client_alive_count_max > 0 && + ssh_packet_inc_alive_timeouts(ssh) > + options.client_alive_count_max) { + sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); + logit("Timeout, client not responding from %s", remote_id); + cleanup_exit(255); + } + + /* + * send a bogus global/channel request with "wantreply", + * we should get back a failure + */ + if ((channel_id = channel_find_open(ssh)) == -1) { + if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || + (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) + != 0 || + (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ + fatal_fr(r, "compose"); + } else { + channel_request_start(ssh, channel_id, + "keepalive@openssh.com", 1); + } + if ((r = sshpkt_send(ssh)) != 0) + fatal_fr(r, "send"); +} + +/* + * Sleep in ppoll() until we can do something. + * Optionally, a maximum time can be specified for the duration of + * the wait (0 = infinite). + */ +static void +wait_until_can_do_something(struct ssh *ssh, + int connection_in, int connection_out, struct pollfd **pfdp, + u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, + int *conn_in_readyp, int *conn_out_readyp) +{ + struct timespec timeout; + char remote_id[512]; + int ret; + int client_alive_scheduled = 0; + u_int p; + time_t now; + static time_t last_client_time, unused_connection_expiry; + + *conn_in_readyp = *conn_out_readyp = 0; + + /* Prepare channel poll. First two pollfd entries are reserved */ + ptimeout_init(&timeout); + channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); + now = monotime(); + if (*npfd_activep < 2) + fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ + if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { + ptimeout_deadline_sec(&timeout, + ssh_packet_get_rekey_timeout(ssh)); + } + + /* + * If no channels are open and UnusedConnectionTimeout is set, then + * start the clock to terminate the connection. + */ + if (options.unused_connection_timeout != 0) { + if (channel_still_open(ssh) || unused_connection_expiry == 0) { + unused_connection_expiry = now + + options.unused_connection_timeout; + } + ptimeout_deadline_monotime(&timeout, unused_connection_expiry); + } + + /* + * if using client_alive, set the max timeout accordingly, + * and indicate that this particular timeout was for client + * alive by setting the client_alive_scheduled flag. + * + * this could be randomized somewhat to make traffic + * analysis more difficult, but we're not doing it yet. + */ + if (options.client_alive_interval) { + /* Time we last heard from the client OR sent a keepalive */ + if (last_client_time == 0) + last_client_time = now; + ptimeout_deadline_sec(&timeout, options.client_alive_interval); + /* XXX ? deadline_monotime(last_client_time + alive_interval) */ + client_alive_scheduled = 1; + } + +#if 0 + /* wrong: bad condition XXX */ + if (channel_not_very_much_buffered_data()) +#endif + /* Monitor client connection on reserved pollfd entries */ + (*pfdp)[0].fd = connection_in; + (*pfdp)[0].events = POLLIN; + (*pfdp)[1].fd = connection_out; + (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; + + /* + * If child has terminated and there is enough buffer space to read + * from it, then read as much as is available and exit. + */ + if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) + ptimeout_deadline_ms(&timeout, 100); + + /* Wait for something to happen, or the timeout to expire. */ + ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); + + if (ret == -1) { + for (p = 0; p < *npfd_activep; p++) + (*pfdp)[p].revents = 0; + if (errno != EINTR) + fatal_f("ppoll: %.100s", strerror(errno)); + return; + } + + *conn_in_readyp = (*pfdp)[0].revents != 0; + *conn_out_readyp = (*pfdp)[1].revents != 0; + + now = monotime(); /* need to reset after ppoll() */ + /* ClientAliveInterval probing */ + if (client_alive_scheduled) { + if (ret == 0 && + now > last_client_time + options.client_alive_interval) { + /* ppoll timed out and we're due to probe */ + client_alive_check(ssh); + last_client_time = now; + } else if (ret != 0 && *conn_in_readyp) { + /* Data from peer; reset probe timer. */ + last_client_time = now; + } + } + + /* UnusedConnectionTimeout handling */ + if (unused_connection_expiry != 0 && + now > unused_connection_expiry && !channel_still_open(ssh)) { + sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); + logit("terminating inactive connection from %s", remote_id); + cleanup_exit(255); + } +} + +/* + * Processes input from the client and the program. Input data is stored + * in buffers and processed later. + */ +static int +process_input(struct ssh *ssh, int connection_in) +{ + int r; + + if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) + return 0; /* success */ + if (r == SSH_ERR_SYSTEM_ERROR) { + if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK) + return 0; + if (errno == EPIPE) { + verbose("Connection closed by %.100s port %d", + ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); + return -1; + } + verbose("Read error from remote host %s port %d: %s", + ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), + strerror(errno)); + cleanup_exit(255); + } + return -1; +} + +/* + * Sends data from internal buffers to client program stdin. + */ +static void +process_output(struct ssh *ssh, int connection_out) +{ + int r; + + /* Send any buffered packet data to the client. */ + if ((r = ssh_packet_write_poll(ssh)) != 0) { + sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", + __func__); + } +} + +static void +process_buffered_input_packets(struct ssh *ssh) +{ + ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); +} + +static void +collect_children(struct ssh *ssh) +{ + pid_t pid; + int status; + + if (child_terminated) { + debug("Received SIGCHLD."); + while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || + (pid == -1 && errno == EINTR)) + if (pid > 0) + session_close_by_pid(ssh, pid, status); + child_terminated = 0; + } +} + +void +server_loop2(struct ssh *ssh, Authctxt *authctxt) +{ + struct pollfd *pfd = NULL; + u_int npfd_alloc = 0, npfd_active = 0; + int r, conn_in_ready, conn_out_ready; + u_int connection_in, connection_out; + sigset_t bsigset, osigset; + + debug("Entering interactive session for SSH2."); + + if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) + error_f("bsigset setup: %s", strerror(errno)); + ssh_signal(SIGCHLD, sigchld_handler); + child_terminated = 0; + connection_in = ssh_packet_get_connection_in(ssh); + connection_out = ssh_packet_get_connection_out(ssh); + + if (!use_privsep) { + ssh_signal(SIGTERM, sigterm_handler); + ssh_signal(SIGINT, sigterm_handler); + ssh_signal(SIGQUIT, sigterm_handler); + } + + server_init_dispatch(ssh); + + for (;;) { + process_buffered_input_packets(ssh); + + if (!ssh_packet_is_rekeying(ssh) && + ssh_packet_not_very_much_data_to_write(ssh)) + channel_output_poll(ssh); + + /* + * Block SIGCHLD while we check for dead children, then pass + * the old signal mask through to ppoll() so that it'll wake + * up immediately if a child exits after we've called waitpid(). + */ + if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) + error_f("bsigset sigprocmask: %s", strerror(errno)); + collect_children(ssh); + wait_until_can_do_something(ssh, connection_in, connection_out, + &pfd, &npfd_alloc, &npfd_active, &osigset, + &conn_in_ready, &conn_out_ready); + if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) + error_f("osigset sigprocmask: %s", strerror(errno)); + + if (received_sigterm) { + logit("Exiting on signal %d", (int)received_sigterm); + /* Clean up sessions, utmp, etc. */ + cleanup_exit(255); + } + + channel_after_poll(ssh, pfd, npfd_active); + if (conn_in_ready && + process_input(ssh, connection_in) < 0) + break; + /* A timeout may have triggered rekeying */ + if ((r = ssh_packet_check_rekey(ssh)) != 0) + fatal_fr(r, "cannot start rekeying"); + if (conn_out_ready) + process_output(ssh, connection_out); + } + collect_children(ssh); + free(pfd); + + /* free all channels, no more reads and writes */ + channel_free_all(ssh); + + /* free remaining sessions, e.g. remove wtmp entries */ + session_destroy_all(ssh, NULL); +} + +static int +server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) +{ + debug("Got %d/%u for keepalive", type, seq); + /* + * reset timeout, since we got a sane answer from the client. + * even if this was generated by something other than + * the bogus CHANNEL_REQUEST we send for keepalives. + */ + ssh_packet_set_alive_timeouts(ssh, 0); + return 0; +} + +static Channel * +server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) +{ + Channel *c = NULL; + char *target = NULL, *originator = NULL; + u_int target_port = 0, originator_port = 0; + int r; + + if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || + (r = sshpkt_get_u32(ssh, &target_port)) != 0 || + (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || + (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + if (target_port > 0xFFFF) { + error_f("invalid target port"); + *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; + goto out; + } + if (originator_port > 0xFFFF) { + error_f("invalid originator port"); + *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; + goto out; + } + + debug_f("originator %s port %u, target %s port %u", + originator, originator_port, target, target_port); + + /* XXX fine grained permissions */ + if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && + auth_opts->permit_port_forwarding_flag && + !options.disable_forwarding) { + c = channel_connect_to_port(ssh, target, target_port, + "direct-tcpip", "direct-tcpip", reason, errmsg); + } else { + logit("refused local port forward: " + "originator %s port %d, target %s port %d", + originator, originator_port, target, target_port); + if (reason != NULL) + *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; + } + + out: + free(originator); + free(target); + return c; +} + +static Channel * +server_request_direct_streamlocal(struct ssh *ssh) +{ + Channel *c = NULL; + char *target = NULL, *originator = NULL; + u_int originator_port = 0; + struct passwd *pw = the_authctxt->pw; + int r; + + if (pw == NULL || !the_authctxt->valid) + fatal_f("no/invalid user"); + + if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || + (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || + (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || + (r = sshpkt_get_end(ssh)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + if (originator_port > 0xFFFF) { + error_f("invalid originator port"); + goto out; + } + + debug_f("originator %s port %d, target %s", + originator, originator_port, target); + + /* XXX fine grained permissions */ + if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && + auth_opts->permit_port_forwarding_flag && + !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { + c = channel_connect_to_path(ssh, target, + "direct-streamlocal@openssh.com", "direct-streamlocal"); + } else { + logit("refused streamlocal port forward: " + "originator %s port %d, target %s", + originator, originator_port, target); + } + +out: + free(originator); + free(target); + return c; +} + +static Channel * +server_request_tun(struct ssh *ssh) +{ + Channel *c = NULL; + u_int mode, tun; + int r, sock; + char *tmp, *ifname = NULL; + + if ((r = sshpkt_get_u32(ssh, &mode)) != 0) + sshpkt_fatal(ssh, r, "%s: parse mode", __func__); + switch (mode) { + case SSH_TUNMODE_POINTOPOINT: + case SSH_TUNMODE_ETHERNET: + break; + default: + ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); + return NULL; + } + if ((options.permit_tun & mode) == 0) { + ssh_packet_send_debug(ssh, "Server has rejected tunnel device " + "forwarding"); + return NULL; + } + + if ((r = sshpkt_get_u32(ssh, &tun)) != 0) + sshpkt_fatal(ssh, r, "%s: parse device", __func__); + if (tun > INT_MAX) { + debug_f("invalid tun"); + goto done; + } + if (auth_opts->force_tun_device != -1) { + if (tun != SSH_TUNID_ANY && + auth_opts->force_tun_device != (int)tun) + goto done; + tun = auth_opts->force_tun_device; + } + sock = tun_open(tun, mode, &ifname); + if (sock < 0) + goto done; + debug("Tunnel forwarding using interface %s", ifname); + + c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, + CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); + c->datagram = 1; +#if defined(SSH_TUN_FILTER) + if (mode == SSH_TUNMODE_POINTOPOINT) + channel_register_filter(ssh, c->self, sys_tun_infilter, + sys_tun_outfilter, NULL, NULL); +#endif + + /* + * Update the list of names exposed to the session + * XXX remove these if the tunnels are closed (won't matter + * much if they are already in the environment though) + */ + tmp = tun_fwd_ifnames; + xasprintf(&tun_fwd_ifnames, "%s%s%s", + tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, + tun_fwd_ifnames == NULL ? "" : ",", + ifname); + free(tmp); + free(ifname); + + done: + if (c == NULL) + ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); + return c; +} + +static Channel * +server_request_session(struct ssh *ssh) +{ + Channel *c; + int r; + + debug("input_session_request"); + if ((r = sshpkt_get_end(ssh)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + + if (no_more_sessions) { + ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " + "session after additional sessions disabled"); + } + + /* + * A server session has no fd to read or write until a + * CHANNEL_REQUEST for a shell is made, so we set the type to + * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all + * CHANNEL_REQUEST messages is registered. + */ + c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, + -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, + 0, "server-session", 1); + if (session_open(the_authctxt, c->self) != 1) { + debug("session open failed, free channel %d", c->self); + channel_free(ssh, c); + return NULL; + } + channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); + return c; +} + +static int +server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) +{ + Channel *c = NULL; + char *ctype = NULL; + const char *errmsg = NULL; + int r, reason = SSH2_OPEN_CONNECT_FAILED; + u_int rchan = 0, rmaxpack = 0, rwindow = 0; + + if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || + (r = sshpkt_get_u32(ssh, &rchan)) != 0 || + (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || + (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + debug_f("ctype %s rchan %u win %u max %u", + ctype, rchan, rwindow, rmaxpack); + + if (strcmp(ctype, "session") == 0) { + c = server_request_session(ssh); + } else if (strcmp(ctype, "direct-tcpip") == 0) { + c = server_request_direct_tcpip(ssh, &reason, &errmsg); + } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { + c = server_request_direct_streamlocal(ssh); + } else if (strcmp(ctype, "tun@openssh.com") == 0) { + c = server_request_tun(ssh); + } + if (c != NULL) { + debug_f("confirm %s", ctype); + c->remote_id = rchan; + c->have_remote_id = 1; + c->remote_window = rwindow; + c->remote_maxpacket = rmaxpack; + if (c->type != SSH_CHANNEL_CONNECTING) { + if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || + (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || + (r = sshpkt_put_u32(ssh, c->self)) != 0 || + (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || + (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || + (r = sshpkt_send(ssh)) != 0) { + sshpkt_fatal(ssh, r, + "%s: send open confirm", __func__); + } + } + } else { + debug_f("failure %s", ctype); + if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || + (r = sshpkt_put_u32(ssh, rchan)) != 0 || + (r = sshpkt_put_u32(ssh, reason)) != 0 || + (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || + (r = sshpkt_put_cstring(ssh, "")) != 0 || + (r = sshpkt_send(ssh)) != 0) { + sshpkt_fatal(ssh, r, + "%s: send open failure", __func__); + } + } + free(ctype); + return 0; +} + +static int +server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) +{ + struct sshbuf *resp = NULL; + struct sshbuf *sigbuf = NULL; + struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; + int r, ndx, success = 0; + const u_char *blob; + const char *sigalg, *kex_rsa_sigalg = NULL; + u_char *sig = 0; + size_t blen, slen; + + if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) + fatal_f("sshbuf_new"); + if (sshkey_type_plain(sshkey_type_from_name( + ssh->kex->hostkey_alg)) == KEY_RSA) + kex_rsa_sigalg = ssh->kex->hostkey_alg; + while (ssh_packet_remaining(ssh) > 0) { + sshkey_free(key); + key = NULL; + if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || + (r = sshkey_from_blob(blob, blen, &key)) != 0) { + error_fr(r, "parse key"); + goto out; + } + /* + * Better check that this is actually one of our hostkeys + * before attempting to sign anything with it. + */ + if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { + error_f("unknown host %s key", sshkey_type(key)); + goto out; + } + /* + * XXX refactor: make kex->sign just use an index rather + * than passing in public and private keys + */ + if ((key_prv = get_hostkey_by_index(ndx)) == NULL && + (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { + error_f("can't retrieve hostkey %d", ndx); + goto out; + } + sshbuf_reset(sigbuf); + free(sig); + sig = NULL; + /* + * For RSA keys, prefer to use the signature type negotiated + * during KEX to the default (SHA1). + */ + sigalg = NULL; + if (sshkey_type_plain(key->type) == KEY_RSA) { + if (kex_rsa_sigalg != NULL) + sigalg = kex_rsa_sigalg; + else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) + sigalg = "rsa-sha2-512"; + else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) + sigalg = "rsa-sha2-256"; + } + debug3_f("sign %s key (index %d) using sigalg %s", + sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); + if ((r = sshbuf_put_cstring(sigbuf, + "hostkeys-prove-00@openssh.com")) != 0 || + (r = sshbuf_put_stringb(sigbuf, + ssh->kex->session_id)) != 0 || + (r = sshkey_puts(key, sigbuf)) != 0 || + (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, + sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || + (r = sshbuf_put_string(resp, sig, slen)) != 0) { + error_fr(r, "assemble signature"); + goto out; + } + } + /* Success */ + *respp = resp; + resp = NULL; /* don't free it */ + success = 1; + out: + free(sig); + sshbuf_free(resp); + sshbuf_free(sigbuf); + sshkey_free(key); + return success; +} + +static int +server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) +{ + char *rtype = NULL; + u_char want_reply = 0; + int r, success = 0, allocated_listen_port = 0; + u_int port = 0; + struct sshbuf *resp = NULL; + struct passwd *pw = the_authctxt->pw; + struct Forward fwd; + + memset(&fwd, 0, sizeof(fwd)); + if (pw == NULL || !the_authctxt->valid) + fatal_f("no/invalid user"); + + if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || + (r = sshpkt_get_u8(ssh, &want_reply)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + debug_f("rtype %s want_reply %d", rtype, want_reply); + + /* -R style forwarding */ + if (strcmp(rtype, "tcpip-forward") == 0) { + if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || + (r = sshpkt_get_u32(ssh, &port)) != 0) + sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); + debug_f("tcpip-forward listen %s port %u", + fwd.listen_host, port); + if (port <= INT_MAX) + fwd.listen_port = (int)port; + /* check permissions */ + if (port > INT_MAX || + (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || + !auth_opts->permit_port_forwarding_flag || + options.disable_forwarding || + (!want_reply && fwd.listen_port == 0) || + (fwd.listen_port != 0 && + !bind_permitted(fwd.listen_port, pw->pw_uid))) { + success = 0; + ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); + } else { + /* Start listening on the port */ + success = channel_setup_remote_fwd_listener(ssh, &fwd, + &allocated_listen_port, &options.fwd_opts); + } + if ((resp = sshbuf_new()) == NULL) + fatal_f("sshbuf_new"); + if (allocated_listen_port != 0 && + (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) + fatal_fr(r, "sshbuf_put_u32"); + } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { + if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || + (r = sshpkt_get_u32(ssh, &port)) != 0) + sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); + + debug_f("cancel-tcpip-forward addr %s port %d", + fwd.listen_host, port); + if (port <= INT_MAX) { + fwd.listen_port = (int)port; + success = channel_cancel_rport_listener(ssh, &fwd); + } + } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { + if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) + sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); + debug_f("streamlocal-forward listen path %s", + fwd.listen_path); + + /* check permissions */ + if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 + || !auth_opts->permit_port_forwarding_flag || + options.disable_forwarding || + (pw->pw_uid != 0 && !use_privsep)) { + success = 0; + ssh_packet_send_debug(ssh, "Server has disabled " + "streamlocal forwarding."); + } else { + /* Start listening on the socket */ + success = channel_setup_remote_fwd_listener(ssh, + &fwd, NULL, &options.fwd_opts); + } + } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { + if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) + sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); + debug_f("cancel-streamlocal-forward path %s", + fwd.listen_path); + + success = channel_cancel_rport_listener(ssh, &fwd); + } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { + no_more_sessions = 1; + success = 1; + } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { + success = server_input_hostkeys_prove(ssh, &resp); + } + /* XXX sshpkt_get_end() */ + if (want_reply) { + if ((r = sshpkt_start(ssh, success ? + SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || + (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || + (r = sshpkt_send(ssh)) != 0 || + (r = ssh_packet_write_wait(ssh)) != 0) + sshpkt_fatal(ssh, r, "%s: send reply", __func__); + } + free(fwd.listen_host); + free(fwd.listen_path); + free(rtype); + sshbuf_free(resp); + return 0; +} + +static int +server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) +{ + Channel *c; + int r, success = 0; + char *rtype = NULL; + u_char want_reply = 0; + u_int id = 0; + + if ((r = sshpkt_get_u32(ssh, &id)) != 0 || + (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || + (r = sshpkt_get_u8(ssh, &want_reply)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + + debug("server_input_channel_req: channel %u request %s reply %d", + id, rtype, want_reply); + + if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { + ssh_packet_disconnect(ssh, "%s: unknown channel %d", + __func__, id); + } + if (!strcmp(rtype, "eow@openssh.com")) { + if ((r = sshpkt_get_end(ssh)) != 0) + sshpkt_fatal(ssh, r, "%s: parse packet", __func__); + chan_rcvd_eow(ssh, c); + } else if ((c->type == SSH_CHANNEL_LARVAL || + c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) + success = session_input_channel_req(ssh, c, rtype); + if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { + if (!c->have_remote_id) + fatal_f("channel %d: no remote_id", c->self); + if ((r = sshpkt_start(ssh, success ? + SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || + (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || + (r = sshpkt_send(ssh)) != 0) + sshpkt_fatal(ssh, r, "%s: send reply", __func__); + } + free(rtype); + return 0; +} + +static void +server_init_dispatch(struct ssh *ssh) +{ + debug("server_init_dispatch"); + ssh_dispatch_init(ssh, &dispatch_protocol_error); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); + ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); + /* client_alive */ + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); + ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); + ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); + ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); + /* rekeying */ + ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); +} |