/* $NetBSD: sshd-session.c,v 1.10 2025/04/11 17:09:23 christos Exp $ */ /* $OpenBSD: sshd-session.c,v 1.12 2025/03/12 22:43:44 djm Exp $ */ /* * SSH2 implementation: * Privilege Separation: * * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. * Copyright (c) 2002 Niels Provos. 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" __RCSID("$NetBSD: sshd-session.c,v 1.10 2025/04/11 17:09:23 christos Exp $"); #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef WITH_OPENSSL #include #include #endif #include #include "xmalloc.h" #include "ssh.h" #include "ssh2.h" #include "sshpty.h" #include "packet.h" #include "log.h" #include "sshbuf.h" #include "misc.h" #include "match.h" #include "servconf.h" #include "uidswap.h" #include "compat.h" #include "cipher.h" #include "digest.h" #include "sshkey.h" #include "kex.h" #include "authfile.h" #include "pathnames.h" #include "atomicio.h" #include "canohost.h" #include "hostfile.h" #include "auth.h" #include "authfd.h" #include "msg.h" #include "dispatch.h" #include "channels.h" #include "session.h" #include "monitor.h" #ifdef GSSAPI #include "ssh-gss.h" #endif #include "monitor_wrap.h" #include "auth-options.h" #include "version.h" #include "ssherr.h" #include "sk-api.h" #include "srclimit.h" #include "dh.h" #include "pfilter.h" #ifdef LIBWRAP #include #include int allow_severity = LOG_INFO; int deny_severity = LOG_WARNING; static void check_connection(const char *argv0, int sock_in) { struct request_info req; request_init(&req, RQ_DAEMON, argv0, RQ_FILE, sock_in, 0); fromhost(&req); if (hosts_access(&req)) return; debug("Connection refused by tcp wrapper"); /* n.b. hosts_access(3) has logged and notified blocklistd */ refuse(&req); /* NOTREACHED */ fatal("libwrap refuse returns"); } #endif /* LIBWRAP */ #ifdef WITH_LDAP_PUBKEY #include "ldapauth.h" #endif #ifndef HOST_NAME_MAX #define HOST_NAME_MAX MAXHOSTNAMELEN #endif /* Re-exec fds */ #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 2) #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 3) /* Privsep fds */ #define PRIVSEP_MONITOR_FD (STDERR_FILENO + 1) #define PRIVSEP_LOG_FD (STDERR_FILENO + 2) #define PRIVSEP_MIN_FREE_FD (STDERR_FILENO + 3) extern char *__progname; /* Server configuration options. */ ServerOptions options; /* Name of the server configuration file. */ const char *config_file_name = _PATH_SERVER_CONFIG_FILE; /* * Debug mode flag. This can be set on the command line. If debug * mode is enabled, extra debugging output will be sent to the system * log, the daemon will not go to background, and will exit after processing * the first connection. */ int debug_flag = 0; /* Flag indicating that the daemon is being started from inetd. */ static int inetd_flag = 0; /* debug goes to stderr unless inetd_flag is set */ static int log_stderr = 0; /* Saved arguments to main(). */ static char **saved_argv; /* Daemon's agent connection */ int auth_sock = -1; static int have_agent = 0; /* * Any really sensitive data in the application is contained in this * structure. The idea is that this structure could be locked into memory so * that the pages do not get written into swap. However, there are some * problems. The private key contains BIGNUMs, and we do not (in principle) * have access to the internals of them, and locking just the structure is * not very useful. Currently, memory locking is not implemented. */ struct { u_int num_hostkeys; struct sshkey **host_keys; /* all private host keys */ struct sshkey **host_pubkeys; /* all public host keys */ struct sshkey **host_certificates; /* all public host certificates */ } sensitive_data; /* record remote hostname or ip */ u_int utmp_len = HOST_NAME_MAX+1; static int startup_pipe = -1; /* in child */ /* variables used for privilege separation */ struct monitor *pmonitor = NULL; int privsep_is_preauth = 1; /* global connection state and authentication contexts */ Authctxt *the_authctxt = NULL; struct ssh *the_active_state; /* global key/cert auth options. XXX move to permanent ssh->authctxt? */ struct sshauthopt *auth_opts = NULL; /* sshd_config buffer */ struct sshbuf *cfg; /* Included files from the configuration file */ struct include_list includes = TAILQ_HEAD_INITIALIZER(includes); /* message to be displayed after login */ struct sshbuf *loginmsg; /* Prototypes for various functions defined later in this file. */ void destroy_sensitive_data(void); void demote_sensitive_data(void); /* XXX reduce to stub once postauth split */ int mm_is_monitor(void) { /* * m_pid is only set in the privileged part, and * points to the unprivileged child. */ return (pmonitor && pmonitor->m_pid > 0); } /* * Signal handler for the alarm after the login grace period has expired. * As usual, this may only take signal-safe actions, even though it is * terminal. */ __dead static void grace_alarm_handler(int sig) { pfilter_notify(1); /* * Try to kill any processes that we have spawned, E.g. authorized * keys command helpers or privsep children. */ if (getpgid(0) == getpid()) { struct sigaction sa; /* mask all other signals while in handler */ memset(&sa, 0, sizeof(sa)); sa.sa_handler = SIG_IGN; sigfillset(&sa.sa_mask); sa.sa_flags = SA_RESTART; (void)sigaction(SIGTERM, &sa, NULL); kill(0, SIGTERM); } _exit(EXIT_LOGIN_GRACE); } /* Destroy the host and server keys. They will no longer be needed. */ void destroy_sensitive_data(void) { u_int i; for (i = 0; i < options.num_host_key_files; i++) { if (sensitive_data.host_keys[i]) { sshkey_free(sensitive_data.host_keys[i]); sensitive_data.host_keys[i] = NULL; } if (sensitive_data.host_certificates[i]) { sshkey_free(sensitive_data.host_certificates[i]); sensitive_data.host_certificates[i] = NULL; } } } /* Demote private to public keys for network child */ void demote_sensitive_data(void) { struct sshkey *tmp; u_int i; int r; for (i = 0; i < options.num_host_key_files; i++) { if (sensitive_data.host_keys[i]) { if ((r = sshkey_from_private( sensitive_data.host_keys[i], &tmp)) != 0) fatal_r(r, "could not demote host %s key", sshkey_type(sensitive_data.host_keys[i])); sshkey_free(sensitive_data.host_keys[i]); sensitive_data.host_keys[i] = tmp; } /* Certs do not need demotion */ } } struct sshbuf * pack_hostkeys(void) { struct sshbuf *keybuf = NULL, *hostkeys = NULL; int r; u_int i; if ((hostkeys = sshbuf_new()) == NULL) fatal_f("sshbuf_new failed"); /* pack hostkeys into a string. Empty key slots get empty strings */ for (i = 0; i < options.num_host_key_files; i++) { /* public key */ if (sensitive_data.host_pubkeys[i] != NULL) { if ((r = sshkey_puts(sensitive_data.host_pubkeys[i], hostkeys)) != 0) fatal_fr(r, "compose hostkey public"); } else { if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0) fatal_fr(r, "compose hostkey empty public"); } /* cert */ if (sensitive_data.host_certificates[i] != NULL) { if ((r = sshkey_puts( sensitive_data.host_certificates[i], hostkeys)) != 0) fatal_fr(r, "compose host cert"); } else { if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0) fatal_fr(r, "compose host cert empty"); } } sshbuf_free(keybuf); return hostkeys; } static int privsep_preauth(struct ssh *ssh) { int status, r; pid_t pid; /* Set up unprivileged child process to deal with network data */ pmonitor = monitor_init(); /* Store a pointer to the kex for later rekeying */ pmonitor->m_pkex = &ssh->kex; if ((pid = fork()) == -1) fatal("fork of unprivileged child failed"); else if (pid != 0) { debug2("Network child is on pid %ld", (long)pid); pmonitor->m_pid = pid; if (have_agent) { r = ssh_get_authentication_socket(&auth_sock); if (r != 0) { error_r(r, "Could not get agent socket"); have_agent = 0; } } monitor_child_preauth(ssh, pmonitor); /* Wait for the child's exit status */ while (waitpid(pid, &status, 0) == -1) { if (errno == EINTR) continue; pmonitor->m_pid = -1; fatal_f("waitpid: %s", strerror(errno)); } privsep_is_preauth = 0; pmonitor->m_pid = -1; if (WIFEXITED(status)) { if (WEXITSTATUS(status) != 0) fatal_f("preauth child exited with status %d", WEXITSTATUS(status)); } else if (WIFSIGNALED(status)) fatal_f("preauth child terminated by signal %d", WTERMSIG(status)); return 1; } else { /* child */ close(pmonitor->m_sendfd); close(pmonitor->m_log_recvfd); /* * Arrange unpriv-preauth child process fds: * 0, 1 network socket * 2 optional stderr * 3 reserved * 4 monitor message socket * 5 monitor logging socket * * We know that the monitor sockets will have fds > 4 because * of the reserved fds in main() */ if (ssh_packet_get_connection_in(ssh) != STDIN_FILENO && dup2(ssh_packet_get_connection_in(ssh), STDIN_FILENO) == -1) fatal("dup2 stdin failed: %s", strerror(errno)); if (ssh_packet_get_connection_out(ssh) != STDOUT_FILENO && dup2(ssh_packet_get_connection_out(ssh), STDOUT_FILENO) == -1) fatal("dup2 stdout failed: %s", strerror(errno)); /* leave stderr as-is */ log_redirect_stderr_to(NULL); /* dup can clobber log fd */ if (pmonitor->m_recvfd != PRIVSEP_MONITOR_FD && dup2(pmonitor->m_recvfd, PRIVSEP_MONITOR_FD) == -1) fatal("dup2 monitor fd: %s", strerror(errno)); if (pmonitor->m_log_sendfd != PRIVSEP_LOG_FD && dup2(pmonitor->m_log_sendfd, PRIVSEP_LOG_FD) == -1) fatal("dup2 log fd: %s", strerror(errno)); closefrom(PRIVSEP_MIN_FREE_FD); saved_argv[0] = options.sshd_auth_path; execv(options.sshd_auth_path, saved_argv); fatal_f("exec of %s failed: %s", options.sshd_auth_path, strerror(errno)); } } static void privsep_postauth(struct ssh *ssh, Authctxt *authctxt) { /* New socket pair */ monitor_reinit(pmonitor); pmonitor->m_pid = fork(); if (pmonitor->m_pid == -1) fatal("fork of unprivileged child failed"); else if (pmonitor->m_pid != 0) { verbose("User child is on pid %ld", (long)pmonitor->m_pid); sshbuf_reset(loginmsg); monitor_clear_keystate(ssh, pmonitor); monitor_child_postauth(ssh, pmonitor); /* NEVERREACHED */ exit(0); } /* child */ close(pmonitor->m_sendfd); pmonitor->m_sendfd = -1; /* Demote the private keys to public keys. */ demote_sensitive_data(); /* Drop privileges */ do_setusercontext(authctxt->pw); /* It is safe now to apply the key state */ monitor_apply_keystate(ssh, pmonitor); /* * Tell the packet layer that authentication was successful, since * this information is not part of the key state. */ ssh_packet_set_authenticated(ssh); } static struct sshkey * get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) { u_int i; struct sshkey *key; for (i = 0; i < options.num_host_key_files; i++) { switch (type) { case KEY_RSA_CERT: case KEY_DSA_CERT: case KEY_ECDSA_CERT: case KEY_ED25519_CERT: case KEY_ECDSA_SK_CERT: case KEY_ED25519_SK_CERT: case KEY_XMSS_CERT: key = sensitive_data.host_certificates[i]; break; default: key = sensitive_data.host_keys[i]; if (key == NULL && !need_private) key = sensitive_data.host_pubkeys[i]; break; } if (key == NULL || key->type != type) continue; switch (type) { case KEY_ECDSA: case KEY_ECDSA_SK: case KEY_ECDSA_CERT: case KEY_ECDSA_SK_CERT: if (key->ecdsa_nid != nid) continue; /* FALLTHROUGH */ default: return need_private ? sensitive_data.host_keys[i] : key; } } return NULL; } struct sshkey * get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) { return get_hostkey_by_type(type, nid, 0, ssh); } struct sshkey * get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) { return get_hostkey_by_type(type, nid, 1, ssh); } struct sshkey * get_hostkey_by_index(int ind) { if (ind < 0 || (u_int)ind >= options.num_host_key_files) return (NULL); return (sensitive_data.host_keys[ind]); } struct sshkey * get_hostkey_public_by_index(int ind, struct ssh *ssh) { if (ind < 0 || (u_int)ind >= options.num_host_key_files) return (NULL); return (sensitive_data.host_pubkeys[ind]); } int get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh) { u_int i; for (i = 0; i < options.num_host_key_files; i++) { if (sshkey_is_cert(key)) { if (key == sensitive_data.host_certificates[i] || (compare && sensitive_data.host_certificates[i] && sshkey_equal(key, sensitive_data.host_certificates[i]))) return (i); } else { if (key == sensitive_data.host_keys[i] || (compare && sensitive_data.host_keys[i] && sshkey_equal(key, sensitive_data.host_keys[i]))) return (i); if (key == sensitive_data.host_pubkeys[i] || (compare && sensitive_data.host_pubkeys[i] && sshkey_equal(key, sensitive_data.host_pubkeys[i]))) return (i); } } return (-1); } /* Inform the client of all hostkeys */ static void notify_hostkeys(struct ssh *ssh) { struct sshbuf *buf; struct sshkey *key; u_int i, nkeys; int r; char *fp; /* Some clients cannot cope with the hostkeys message, skip those. */ if (ssh->compat & SSH_BUG_HOSTKEYS) return; if ((buf = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); for (i = nkeys = 0; i < options.num_host_key_files; i++) { key = get_hostkey_public_by_index(i, ssh); if (key == NULL || key->type == KEY_UNSPEC || sshkey_is_cert(key)) continue; fp = sshkey_fingerprint(key, options.fingerprint_hash, SSH_FP_DEFAULT); debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp); free(fp); if (nkeys == 0) { /* * Start building the request when we find the * first usable key. */ if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 || (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */ sshpkt_fatal(ssh, r, "%s: start request", __func__); } /* Append the key to the request */ sshbuf_reset(buf); if ((r = sshkey_putb(key, buf)) != 0) fatal_fr(r, "couldn't put hostkey %d", i); if ((r = sshpkt_put_stringb(ssh, buf)) != 0) sshpkt_fatal(ssh, r, "%s: append key", __func__); nkeys++; } debug3_f("sent %u hostkeys", nkeys); if (nkeys == 0) fatal_f("no hostkeys"); if ((r = sshpkt_send(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: send", __func__); sshbuf_free(buf); } __dead static void usage(void) { fprintf(stderr, "%s, %s\n", SSH_VERSION, SSH_OPENSSL_VERSION); fprintf(stderr, "usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n" " [-E log_file] [-f config_file] [-g login_grace_time]\n" " [-h host_key_file] [-o option] [-p port] [-u len]\n" ); exit(1); } static void parse_hostkeys(struct sshbuf *hostkeys) { int r; u_int num_keys = 0; struct sshkey *k; struct sshbuf *kbuf; const u_char *cp; size_t len; while (sshbuf_len(hostkeys) != 0) { if (num_keys > 2048) fatal_f("too many hostkeys"); sensitive_data.host_keys = xrecallocarray( sensitive_data.host_keys, num_keys, num_keys + 1, sizeof(*sensitive_data.host_pubkeys)); sensitive_data.host_pubkeys = xrecallocarray( sensitive_data.host_pubkeys, num_keys, num_keys + 1, sizeof(*sensitive_data.host_pubkeys)); sensitive_data.host_certificates = xrecallocarray( sensitive_data.host_certificates, num_keys, num_keys + 1, sizeof(*sensitive_data.host_certificates)); /* private key */ k = NULL; if ((r = sshbuf_froms(hostkeys, &kbuf)) != 0) fatal_fr(r, "extract privkey"); if (sshbuf_len(kbuf) != 0 && (r = sshkey_private_deserialize(kbuf, &k)) != 0) fatal_fr(r, "parse pubkey"); sensitive_data.host_keys[num_keys] = k; sshbuf_free(kbuf); if (k) debug2_f("privkey %u: %s", num_keys, sshkey_ssh_name(k)); /* public key */ k = NULL; if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0) fatal_fr(r, "extract pubkey"); if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0) fatal_fr(r, "parse pubkey"); sensitive_data.host_pubkeys[num_keys] = k; if (k) debug2_f("pubkey %u: %s", num_keys, sshkey_ssh_name(k)); /* certificate */ k = NULL; if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0) fatal_fr(r, "extract pubkey"); if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0) fatal_fr(r, "parse pubkey"); sensitive_data.host_certificates[num_keys] = k; if (k) debug2_f("cert %u: %s", num_keys, sshkey_ssh_name(k)); num_keys++; } sensitive_data.num_hostkeys = num_keys; } static void recv_rexec_state(int fd, struct sshbuf *conf, uint64_t *timing_secretp) { struct sshbuf *m, *inc, *hostkeys; u_char *cp, ver; size_t len; int r; struct include_item *item; debug3_f("entering fd = %d", fd); if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) fatal_f("sshbuf_new failed"); /* receive config */ if (ssh_msg_recv(fd, m) == -1) fatal_f("ssh_msg_recv failed"); if ((r = sshbuf_get_u8(m, &ver)) != 0) fatal_fr(r, "parse version"); if (ver != 0) fatal_f("rexec version mismatch"); if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || /* XXX _direct */ (r = sshbuf_get_u64(m, timing_secretp)) != 0 || (r = sshbuf_get_stringb(m, inc)) != 0) fatal_fr(r, "parse config"); if (conf != NULL && (r = sshbuf_put(conf, cp, len))) fatal_fr(r, "sshbuf_put"); while (sshbuf_len(inc) != 0) { item = xcalloc(1, sizeof(*item)); if ((item->contents = sshbuf_new()) == NULL) fatal_f("sshbuf_new failed"); if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 || (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 || (r = sshbuf_get_stringb(inc, item->contents)) != 0) fatal_fr(r, "parse includes"); TAILQ_INSERT_TAIL(&includes, item, entry); } /* receive hostkeys */ sshbuf_reset(m); if (ssh_msg_recv(fd, m) == -1) fatal_f("ssh_msg_recv failed"); if ((r = sshbuf_get_u8(m, NULL)) != 0 || (r = sshbuf_froms(m, &hostkeys)) != 0) fatal_fr(r, "parse config"); parse_hostkeys(hostkeys); free(cp); sshbuf_free(m); sshbuf_free(hostkeys); sshbuf_free(inc); debug3_f("done"); } /* * If IP options are supported, make sure there are none (log and * return an error if any are found). Basically we are worried about * source routing; it can be used to pretend you are somebody * (ip-address) you are not. That itself may be "almost acceptable" * under certain circumstances, but rhosts authentication is useless * if source routing is accepted. Notice also that if we just dropped * source routing here, the other side could use IP spoofing to do * rest of the interaction and could still bypass security. So we * exit here if we detect any IP options. */ static void check_ip_options(struct ssh *ssh) { int sock_in = ssh_packet_get_connection_in(ssh); struct sockaddr_storage from; u_char opts[200]; socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from); char text[sizeof(opts) * 3 + 1]; memset(&from, 0, sizeof(from)); if (getpeername(sock_in, (struct sockaddr *)&from, &fromlen) == -1) return; if (from.ss_family != AF_INET) return; /* XXX IPv6 options? */ if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts, &option_size) >= 0 && option_size != 0) { text[0] = '\0'; for (i = 0; i < option_size; i++) snprintf(text + i*3, sizeof(text) - i*3, " %2.2x", opts[i]); fatal("Connection from %.100s port %d with IP opts: %.800s", ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text); } } #ifdef __OpenBSD__ /* Set the routing domain for this process */ static void set_process_rdomain(struct ssh *ssh, const char *name) { int rtable, ortable = getrtable(); const char *errstr; if (name == NULL) return; /* default */ if (strcmp(name, "%D") == 0) { /* "expands" to routing domain of connection */ if ((name = ssh_packet_rdomain_in(ssh)) == NULL) return; } rtable = (int)strtonum(name, 0, 255, &errstr); if (errstr != NULL) /* Shouldn't happen */ fatal("Invalid routing domain \"%s\": %s", name, errstr); if (rtable != ortable && setrtable(rtable) != 0) fatal("Unable to set routing domain %d: %s", rtable, strerror(errno)); debug_f("set routing domain %d (was %d)", rtable, ortable); } #endif /* * Main program for the daemon. */ int main(int ac, char **av) { struct ssh *ssh = NULL; extern char *optarg; extern int optind; int devnull, r, opt, on = 1, remote_port; int sock_in = -1, sock_out = -1, rexeced_flag = 0, have_key = 0; const char *remote_ip, *rdomain; char *line, *laddr, *logfile = NULL; u_int i; u_int64_t ibytes, obytes; mode_t new_umask; Authctxt *authctxt; struct connection_info *connection_info = NULL; sigset_t sigmask; uint64_t timing_secret = 0; struct itimerval itv; sigemptyset(&sigmask); sigprocmask(SIG_SETMASK, &sigmask, NULL); /* Save argv. */ saved_argv = av; /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ sanitise_stdfd(); /* Initialize configuration options to their default values. */ initialize_server_options(&options); /* Parse command-line arguments. */ while ((opt = getopt(ac, av, "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) { switch (opt) { case '4': options.address_family = AF_INET; break; case '6': options.address_family = AF_INET6; break; case 'f': config_file_name = optarg; break; case 'c': servconf_add_hostcert("[command-line]", 0, &options, optarg); break; case 'd': if (debug_flag == 0) { debug_flag = 1; options.log_level = SYSLOG_LEVEL_DEBUG1; } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) options.log_level++; break; case 'D': /* ignore */ break; case 'E': logfile = optarg; /* FALLTHROUGH */ case 'e': log_stderr = 1; break; case 'i': inetd_flag = 1; break; case 'r': /* ignore */ break; case 'R': rexeced_flag = 1; break; case 'Q': /* ignored */ break; case 'q': options.log_level = SYSLOG_LEVEL_QUIET; break; case 'b': /* protocol 1, ignored */ break; case 'p': options.ports_from_cmdline = 1; if (options.num_ports >= MAX_PORTS) { fprintf(stderr, "too many ports.\n"); exit(1); } options.ports[options.num_ports++] = a2port(optarg); if (options.ports[options.num_ports-1] <= 0) { fprintf(stderr, "Bad port number.\n"); exit(1); } break; case 'g': if ((options.login_grace_time = convtime(optarg)) == -1) { fprintf(stderr, "Invalid login grace time.\n"); exit(1); } break; case 'k': /* protocol 1, ignored */ break; case 'h': servconf_add_hostkey("[command-line]", 0, &options, optarg, 1); break; case 't': case 'T': case 'G': fatal("test/dump modes not supported"); break; case 'C': connection_info = server_get_connection_info(ssh, 0, 0); if (parse_server_match_testspec(connection_info, optarg) == -1) exit(1); break; case 'u': utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); if (utmp_len > HOST_NAME_MAX+1) { fprintf(stderr, "Invalid utmp length.\n"); exit(1); } break; case 'o': line = xstrdup(optarg); if (process_server_config_line(&options, line, "command-line", 0, NULL, NULL, &includes) != 0) exit(1); free(line); break; case 'V': fprintf(stderr, "%s, %s\n", SSH_VERSION, SSH_OPENSSL_VERSION); exit(0); default: usage(); break; } } /* Check that there are no remaining arguments. */ if (optind < ac) { fprintf(stderr, "Extra argument %s.\n", av[optind]); exit(1); } debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION); if (!rexeced_flag) fatal("sshd-session should not be executed directly"); closefrom(REEXEC_MIN_FREE_FD); /* Reserve fds we'll need later for reexec things */ if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) fatal("open %s: %s", _PATH_DEVNULL, strerror(errno)); while (devnull < PRIVSEP_MIN_FREE_FD) { if ((devnull = dup(devnull)) == -1) fatal("dup %s: %s", _PATH_DEVNULL, strerror(errno)); } #ifdef WITH_OPENSSL OpenSSL_add_all_algorithms(); #endif /* If requested, redirect the logs to the specified logfile. */ if (logfile != NULL) { char *cp, pid_s[32]; snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid()); cp = percent_expand(logfile, "p", pid_s, "P", "sshd-session", (char *)NULL); log_redirect_stderr_to(cp); free(cp); } /* * Force logging to stderr until we have loaded the private host * key (unless started from inetd) */ log_init(__progname, options.log_level == SYSLOG_LEVEL_NOT_SET ? SYSLOG_LEVEL_INFO : options.log_level, options.log_facility == SYSLOG_FACILITY_NOT_SET ? SYSLOG_FACILITY_AUTH : options.log_facility, log_stderr || !inetd_flag || debug_flag); /* Fetch our configuration */ if ((cfg = sshbuf_new()) == NULL) fatal("sshbuf_new config buf failed"); setproctitle("%s", "[rexeced]"); recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg, &timing_secret); parse_server_config(&options, "rexec", cfg, &includes, NULL, 1); /* Fill in default values for those options not explicitly set. */ fill_default_server_options(&options); options.timing_secret = timing_secret; /* Reinit logging in case config set Level, Facility or Verbose. */ log_init(__progname, options.log_level, options.log_facility, log_stderr || !inetd_flag || debug_flag); debug("sshd-session version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION); #ifdef WITH_LDAP_PUBKEY /* ldap_options_print(&options.lpk); */ /* XXX initialize/check ldap connection and set *LD */ if (options.lpk.on) { if (options.lpk.l_conf && (ldap_parse_lconf(&options.lpk) < 0) ) error("[LDAP] could not parse %s", options.lpk.l_conf); if (ldap_xconnect(&options.lpk) < 0) error("[LDAP] could not initialize ldap connection"); } #endif if (!debug_flag && !inetd_flag) { if ((startup_pipe = dup(REEXEC_CONFIG_PASS_FD)) == -1) fatal("internal error: no startup pipe"); /* * Signal parent that this child is at a point where * they can go away if they have a SIGHUP pending. */ (void)atomicio(vwrite, startup_pipe, __UNCONST("\0"), 1); } /* close the fd, but keep the slot reserved */ if (dup2(devnull, REEXEC_CONFIG_PASS_FD) == -1) fatal("dup2 devnull->config fd: %s", strerror(errno)); /* Check that options are sensible */ if (options.authorized_keys_command_user == NULL && (options.authorized_keys_command != NULL && strcasecmp(options.authorized_keys_command, "none") != 0)) fatal("AuthorizedKeysCommand set without " "AuthorizedKeysCommandUser"); if (options.authorized_principals_command_user == NULL && (options.authorized_principals_command != NULL && strcasecmp(options.authorized_principals_command, "none") != 0)) fatal("AuthorizedPrincipalsCommand set without " "AuthorizedPrincipalsCommandUser"); /* * Check whether there is any path through configured auth methods. * Unfortunately it is not possible to verify this generally before * daemonisation in the presence of Match block, but this catches * and warns for trivial misconfigurations that could break login. */ if (options.num_auth_methods != 0) { for (i = 0; i < options.num_auth_methods; i++) { if (auth2_methods_valid(options.auth_methods[i], 1) == 0) break; } if (i >= options.num_auth_methods) fatal("AuthenticationMethods cannot be satisfied by " "enabled authentication methods"); } #ifdef WITH_OPENSSL if (options.moduli_file != NULL) dh_set_moduli_file(options.moduli_file); #endif if (options.host_key_agent) { if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) setenv(SSH_AUTHSOCKET_ENV_NAME, options.host_key_agent, 1); if ((r = ssh_get_authentication_socket(NULL)) == 0) have_agent = 1; else error_r(r, "Could not connect to agent \"%s\"", options.host_key_agent); } if (options.num_host_key_files != sensitive_data.num_hostkeys) { fatal("internal error: hostkeys confused (config %u recvd %u)", options.num_host_key_files, sensitive_data.num_hostkeys); } for (i = 0; i < options.num_host_key_files; i++) { if (sensitive_data.host_keys[i] != NULL || (have_agent && sensitive_data.host_pubkeys[i] != NULL)) { have_key = 1; break; } } if (!have_key) fatal("internal error: monitor received no hostkeys"); /* Ensure that umask disallows at least group and world write */ new_umask = umask(0077) | 0022; (void) umask(new_umask); /* Initialize the log (it is reinitialized below in case we forked). */ if (debug_flag) log_stderr = 1; log_init(__progname, options.log_level, options.log_facility, log_stderr); for (i = 0; i < options.num_log_verbose; i++) log_verbose_add(options.log_verbose[i]); /* Reinitialize the log (because of the fork above). */ log_init(__progname, options.log_level, options.log_facility, log_stderr); /* * Chdir to the root directory so that the current disk can be * unmounted if desired. */ if (chdir("/") == -1) error("chdir(\"/\"): %s", strerror(errno)); /* ignore SIGPIPE */ ssh_signal(SIGPIPE, SIG_IGN); /* Get a connection, either from inetd or rexec */ if (inetd_flag) { /* * NB. must be different fd numbers for the !socket case, * as packet_connection_is_on_socket() depends on this. */ sock_in = dup(STDIN_FILENO); sock_out = dup(STDOUT_FILENO); } else { /* rexec case; accept()ed socket in ancestor listener */ sock_in = sock_out = dup(STDIN_FILENO); } /* * We intentionally do not close the descriptors 0, 1, and 2 * as our code for setting the descriptors won't work if * ttyfd happens to be one of those. */ if (stdfd_devnull(1, 1, !log_stderr) == -1) error("stdfd_devnull failed"); debug("network sockets: %d, %d", sock_in, sock_out); /* This is the child processing a new connection. */ setproctitle("%s", "[accepted]"); /* Executed child processes don't need these. */ fcntl(sock_out, F_SETFD, FD_CLOEXEC); fcntl(sock_in, F_SETFD, FD_CLOEXEC); /* We will not restart on SIGHUP since it no longer makes sense. */ ssh_signal(SIGALRM, SIG_DFL); ssh_signal(SIGHUP, SIG_DFL); ssh_signal(SIGTERM, SIG_DFL); ssh_signal(SIGQUIT, SIG_DFL); ssh_signal(SIGCHLD, SIG_DFL); pfilter_init(); /* * Register our connection. This turns encryption off because we do * not have a key. */ if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL) fatal("Unable to create connection"); the_active_state = ssh; ssh_packet_set_server(ssh); check_ip_options(ssh); /* Prepare the channels layer */ channel_init_channels(ssh); channel_set_af(ssh, options.address_family); server_process_channel_timeouts(ssh); server_process_permitopen(ssh); /* Set SO_KEEPALIVE if requested. */ if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) && setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1) error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); if ((remote_port = ssh_remote_port(ssh)) < 0) { debug("ssh_remote_port failed"); cleanup_exit(255); } /* * The rest of the code depends on the fact that * ssh_remote_ipaddr() caches the remote ip, even if * the socket goes away. */ remote_ip = ssh_remote_ipaddr(ssh); #ifdef LIBWRAP /* Check whether logins are denied from this host. */ if (ssh_packet_connection_is_on_socket(ssh)) { /* First, try with the value stored in __progname */ check_connection(__progname, sock_in); /* * Test with "sshd" as well, since that is what most people * will have in their hosts.allow and hosts.deny files. */ check_connection("sshd", sock_in); } #endif /* LIBWRAP */ rdomain = ssh_packet_rdomain_in(ssh); /* Log the connection. */ laddr = get_local_ipaddr(sock_in); verbose("Connection from %s port %d on %s port %d%s%s%s", remote_ip, remote_port, laddr, ssh_local_port(ssh), rdomain == NULL ? "" : " rdomain \"", rdomain == NULL ? "" : rdomain, rdomain == NULL ? "" : "\""); free(laddr); /* * We don't want to listen forever unless the other side * successfully authenticates itself. So we set up an alarm which is * cleared after successful authentication. A limit of zero * indicates no limit. Note that we don't set the alarm in debugging * mode; it is just annoying to have the server exit just when you * are about to discover the bug. */ ssh_signal(SIGALRM, grace_alarm_handler); if (!debug_flag && options.login_grace_time > 0) { int ujitter = arc4random_uniform(4 * 1000000); timerclear(&itv.it_interval); itv.it_value.tv_sec = options.login_grace_time; itv.it_value.tv_sec += ujitter / 1000000; itv.it_value.tv_usec = ujitter % 1000000; if (setitimer(ITIMER_REAL, &itv, NULL) == -1) fatal("login grace time setitimer failed"); } if ((r = kex_exchange_identification(ssh, -1, options.version_addendum)) != 0) { pfilter_notify(1); sshpkt_fatal(ssh, r, "banner exchange"); } ssh_packet_set_nonblocking(ssh); /* allocate authentication context */ authctxt = xcalloc(1, sizeof(*authctxt)); ssh->authctxt = authctxt; /* XXX global for cleanup, access from other modules */ the_authctxt = authctxt; /* Set default key authentication options */ if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL) fatal("allocation failed"); /* prepare buffer to collect messages to display to user after login */ if ((loginmsg = sshbuf_new()) == NULL) fatal("sshbuf_new loginmsg failed"); auth_debug_reset(); if (privsep_preauth(ssh) != 1) fatal("privsep_preauth failed"); /* Now user is authenticated */ /* * Cancel the alarm we set to limit the time taken for * authentication. */ timerclear(&itv.it_interval); timerclear(&itv.it_value); if (setitimer(ITIMER_REAL, &itv, NULL) == -1) fatal("login grace time clear failed"); ssh_signal(SIGALRM, SIG_DFL); authctxt->authenticated = 1; if (startup_pipe != -1) { /* signal listener that authentication completed successfully */ (void)atomicio(vwrite, startup_pipe, __UNCONST("\001"), 1); close(startup_pipe); startup_pipe = -1; } #ifdef __OpenBSD__ if (options.routing_domain != NULL) set_process_rdomain(ssh, options.routing_domain); #endif #ifdef GSSAPI if (options.gss_authentication) { temporarily_use_uid(authctxt->pw); ssh_gssapi_storecreds(); restore_uid(); } #endif #ifdef USE_PAM if (options.use_pam) { do_pam_setcred(); do_pam_session(ssh); } #endif /* * In privilege separation, we fork another child and prepare * file descriptor passing. */ privsep_postauth(ssh, authctxt); /* the monitor process [priv] will not return */ ssh_packet_set_timeout(ssh, options.client_alive_interval, options.client_alive_count_max); /* Try to send all our hostkeys to the client */ notify_hostkeys(ssh); /* Start session. */ do_authenticated(ssh, authctxt); /* The connection has been terminated. */ ssh_packet_get_bytes(ssh, &ibytes, &obytes); verbose("Transferred: sent %llu, received %llu bytes", (unsigned long long)obytes, (unsigned long long)ibytes); #ifdef USE_PAM if (options.use_pam) finish_pam(); #endif /* USE_PAM */ verbose("Closing connection to %.500s port %d", remote_ip, remote_port); ssh_packet_close(ssh); mm_terminate(); exit(0); } int sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey, struct sshkey *pubkey, u_char **signature, size_t *slenp, const u_char *data, size_t dlen, const char *alg) { if (privkey) { if (mm_sshkey_sign(ssh, privkey, signature, slenp, data, dlen, alg, options.sk_provider, NULL, ssh->compat) < 0) fatal_f("privkey sign failed"); } else { if (mm_sshkey_sign(ssh, pubkey, signature, slenp, data, dlen, alg, options.sk_provider, NULL, ssh->compat) < 0) fatal_f("pubkey sign failed"); } return 0; } /* server specific fatal cleanup */ void cleanup_exit(int i) { extern int auth_attempted; /* monitor.c */ if (the_active_state != NULL && the_authctxt != NULL) { do_cleanup(the_active_state, the_authctxt); if (privsep_is_preauth && pmonitor != NULL && pmonitor->m_pid > 1) { debug("Killing privsep child %d", pmonitor->m_pid); if (kill(pmonitor->m_pid, SIGKILL) != 0 && errno != ESRCH) { error_f("kill(%d): %s", pmonitor->m_pid, strerror(errno)); } } } /* Override default fatal exit value when auth was attempted */ if (i == 255 && auth_attempted) { pfilter_notify(1); _exit(EXIT_AUTH_ATTEMPTED); } _exit(i); }