/* $OpenBSD: sshd.c,v 1.537 2019/06/28 13:35:04 deraadt Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * This program is the ssh daemon. It listens for connections from clients, * and performs authentication, executes use commands or shell, and forwards * information to/from the application to the user client over an encrypted * connection. This can also handle forwarding of X11, TCP/IP, and * authentication agent connections. * * 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 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef WITH_OPENSSL #include #endif #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 "myproposal.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 "ssh-sandbox.h" #include "auth-options.h" #include "version.h" #include "ssherr.h" /* Re-exec fds */ #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) extern char *__progname; /* Server configuration options. */ ServerOptions options; /* Name of the server configuration file. */ 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; /* * Indicating that the daemon should only test the configuration and keys. * If test_flag > 1 ("-T" flag), then sshd will also dump the effective * configuration, optionally using connection information provided by the * "-C" flag. */ static int test_flag = 0; /* Flag indicating that the daemon is being started from inetd. */ static int inetd_flag = 0; /* Flag indicating that sshd should not detach and become a daemon. */ static int no_daemon_flag = 0; /* debug goes to stderr unless inetd_flag is set */ static int log_stderr = 0; /* Saved arguments to main(). */ static char **saved_argv; /* re-exec */ static int rexeced_flag = 0; static int rexec_flag = 1; static int rexec_argc = 0; static char **rexec_argv; /* * The sockets that the server is listening; this is used in the SIGHUP * signal handler. */ #define MAX_LISTEN_SOCKS 16 static int listen_socks[MAX_LISTEN_SOCKS]; static int num_listen_socks = 0; /* 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 { struct sshkey **host_keys; /* all private host keys */ struct sshkey **host_pubkeys; /* all public host keys */ struct sshkey **host_certificates; /* all public host certificates */ int have_ssh2_key; } sensitive_data; /* This is set to true when a signal is received. */ static volatile sig_atomic_t received_sighup = 0; static volatile sig_atomic_t received_sigterm = 0; /* session identifier, used by RSA-auth */ u_char session_id[16]; /* same for ssh2 */ u_char *session_id2 = NULL; u_int session_id2_len = 0; /* record remote hostname or ip */ u_int utmp_len = HOST_NAME_MAX+1; /* * startup_pipes/flags are used for tracking children of the listening sshd * process early in their lifespans. This tracking is needed for three things: * * 1) Implementing the MaxStartups limit of concurrent unauthenticated * connections. * 2) Avoiding a race condition for SIGHUP processing, where child processes * may have listen_socks open that could collide with main listener process * after it restarts. * 3) Ensuring that rexec'd sshd processes have received their initial state * from the parent listen process before handling SIGHUP. * * Child processes signal that they have completed closure of the listen_socks * and (if applicable) received their rexec state by sending a char over their * sock. Child processes signal that authentication has completed by closing * the sock (or by exiting). */ static int *startup_pipes = NULL; static int *startup_flags = NULL; /* Indicates child closed listener */ static int startup_pipe = -1; /* in child */ /* variables used for privilege separation */ int use_privsep = -1; 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; /* 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); static void do_ssh2_kex(struct ssh *); /* * Close all listening sockets */ static void close_listen_socks(void) { int i; for (i = 0; i < num_listen_socks; i++) close(listen_socks[i]); num_listen_socks = -1; } static void close_startup_pipes(void) { int i; if (startup_pipes) for (i = 0; i < options.max_startups; i++) if (startup_pipes[i] != -1) close(startup_pipes[i]); } /* * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; * the effect is to reread the configuration file (and to regenerate * the server key). */ /*ARGSUSED*/ static void sighup_handler(int sig) { int save_errno = errno; received_sighup = 1; errno = save_errno; } /* * Called from the main program after receiving SIGHUP. * Restarts the server. */ static void sighup_restart(void) { logit("Received SIGHUP; restarting."); if (options.pid_file != NULL) unlink(options.pid_file); close_listen_socks(); close_startup_pipes(); alarm(0); /* alarm timer persists across exec */ signal(SIGHUP, SIG_IGN); /* will be restored after exec */ execv(saved_argv[0], saved_argv); logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno)); exit(1); } /* * Generic signal handler for terminating signals in the master daemon. */ /*ARGSUSED*/ static void sigterm_handler(int sig) { received_sigterm = sig; } /* * SIGCHLD handler. This is called whenever a child dies. This will then * reap any zombies left by exited children. */ /*ARGSUSED*/ static void main_sigchld_handler(int sig) { int save_errno = errno; pid_t pid; int status; while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || (pid == -1 && errno == EINTR)) ; errno = save_errno; } /* * Signal handler for the alarm after the login grace period has expired. */ /*ARGSUSED*/ static void grace_alarm_handler(int sig) { if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) kill(pmonitor->m_pid, SIGALRM); /* * Try to kill any processes that we have spawned, E.g. authorized * keys command helpers. */ if (getpgid(0) == getpid()) { signal(SIGTERM, SIG_IGN); kill(0, SIGTERM); } /* XXX pre-format ipaddr/port so we don't need to access active_state */ /* Log error and exit. */ sigdie("Timeout before authentication for %s port %d", ssh_remote_ipaddr(the_active_state), ssh_remote_port(the_active_state)); } /* 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("could not demote host %s key: %s", sshkey_type(sensitive_data.host_keys[i]), ssh_err(r)); sshkey_free(sensitive_data.host_keys[i]); sensitive_data.host_keys[i] = tmp; } /* Certs do not need demotion */ } } static void privsep_preauth_child(void) { gid_t gidset[1]; struct passwd *pw; /* Enable challenge-response authentication for privilege separation */ privsep_challenge_enable(); #ifdef GSSAPI /* Cache supported mechanism OIDs for later use */ ssh_gssapi_prepare_supported_oids(); #endif /* Demote the private keys to public keys. */ demote_sensitive_data(); /* Demote the child */ if (getuid() == 0 || geteuid() == 0) { if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) fatal("Privilege separation user %s does not exist", SSH_PRIVSEP_USER); pw = pwcopy(pw); /* Ensure mutable */ endpwent(); freezero(pw->pw_passwd, strlen(pw->pw_passwd)); /* Change our root directory */ if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, strerror(errno)); if (chdir("/") == -1) fatal("chdir(\"/\"): %s", strerror(errno)); /* * Drop our privileges * NB. Can't use setusercontext() after chroot. */ debug3("privsep user:group %u:%u", (u_int)pw->pw_uid, (u_int)pw->pw_gid); gidset[0] = pw->pw_gid; if (setgroups(1, gidset) == -1) fatal("setgroups: %.100s", strerror(errno)); permanently_set_uid(pw); } } static int privsep_preauth(struct ssh *ssh) { int status, r; pid_t pid; struct ssh_sandbox *box = NULL; /* 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 (use_privsep == PRIVSEP_ON) box = ssh_sandbox_init(); pid = fork(); if (pid == -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("Could not get agent socket: %s", ssh_err(r)); have_agent = 0; } } if (box != NULL) ssh_sandbox_parent_preauth(box, pid); 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("%s: waitpid: %s", __func__, strerror(errno)); } privsep_is_preauth = 0; pmonitor->m_pid = -1; if (WIFEXITED(status)) { if (WEXITSTATUS(status) != 0) fatal("%s: preauth child exited with status %d", __func__, WEXITSTATUS(status)); } else if (WIFSIGNALED(status)) fatal("%s: preauth child terminated by signal %d", __func__, WTERMSIG(status)); if (box != NULL) ssh_sandbox_parent_finish(box); return 1; } else { /* child */ close(pmonitor->m_sendfd); close(pmonitor->m_log_recvfd); /* Arrange for logging to be sent to the monitor */ set_log_handler(mm_log_handler, pmonitor); privsep_preauth_child(); setproctitle("%s", "[net]"); if (box != NULL) ssh_sandbox_child(box); return 0; } } static void privsep_postauth(struct ssh *ssh, Authctxt *authctxt) { if (authctxt->pw->pw_uid == 0) { /* File descriptor passing is broken or root login */ use_privsep = 0; goto skip; } /* 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); skip: /* 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 void append_hostkey_type(struct sshbuf *b, const char *s) { int r; if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) { debug3("%s: %s key not permitted by HostkeyAlgorithms", __func__, s); return; } if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0) fatal("%s: sshbuf_putf: %s", __func__, ssh_err(r)); } static char * list_hostkey_types(void) { struct sshbuf *b; struct sshkey *key; char *ret; u_int i; if ((b = sshbuf_new()) == NULL) fatal("%s: sshbuf_new failed", __func__); for (i = 0; i < options.num_host_key_files; i++) { key = sensitive_data.host_keys[i]; if (key == NULL) key = sensitive_data.host_pubkeys[i]; if (key == NULL) continue; switch (key->type) { case KEY_RSA: /* for RSA we also support SHA2 signatures */ append_hostkey_type(b, "rsa-sha2-512"); append_hostkey_type(b, "rsa-sha2-256"); /* FALLTHROUGH */ case KEY_DSA: case KEY_ECDSA: case KEY_ED25519: case KEY_XMSS: append_hostkey_type(b, sshkey_ssh_name(key)); break; } /* If the private key has a cert peer, then list that too */ key = sensitive_data.host_certificates[i]; if (key == NULL) continue; switch (key->type) { case KEY_RSA_CERT: /* for RSA we also support SHA2 signatures */ append_hostkey_type(b, "rsa-sha2-512-cert-v01@openssh.com"); append_hostkey_type(b, "rsa-sha2-256-cert-v01@openssh.com"); /* FALLTHROUGH */ case KEY_DSA_CERT: case KEY_ECDSA_CERT: case KEY_ED25519_CERT: case KEY_XMSS_CERT: append_hostkey_type(b, sshkey_ssh_name(key)); break; } } if ((ret = sshbuf_dup_string(b)) == NULL) fatal("%s: sshbuf_dup_string failed", __func__); sshbuf_free(b); debug("%s: %s", __func__, ret); return ret; } 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_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 && (key->type != KEY_ECDSA || key->ecdsa_nid == nid)) 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("%s: sshbuf_new", __func__); 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("%s: key %d: %s %s", __func__, 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("%s: couldn't put hostkey %d: %s", __func__, i, ssh_err(r)); if ((r = sshpkt_put_stringb(ssh, buf)) != 0) sshpkt_fatal(ssh, r, "%s: append key", __func__); nkeys++; } debug3("%s: sent %u hostkeys", __func__, nkeys); if (nkeys == 0) fatal("%s: no hostkeys", __func__); if ((r = sshpkt_send(ssh)) != 0) sshpkt_fatal(ssh, r, "%s: send", __func__); sshbuf_free(buf); } /* * returns 1 if connection should be dropped, 0 otherwise. * dropping starts at connection #max_startups_begin with a probability * of (max_startups_rate/100). the probability increases linearly until * all connections are dropped for startups > max_startups */ static int drop_connection(int startups) { int p, r; if (startups < options.max_startups_begin) return 0; if (startups >= options.max_startups) return 1; if (options.max_startups_rate == 100) return 1; p = 100 - options.max_startups_rate; p *= startups - options.max_startups_begin; p /= options.max_startups - options.max_startups_begin; p += options.max_startups_rate; r = arc4random_uniform(100); debug("drop_connection: p %d, r %d", p, r); return (r < p) ? 1 : 0; } static void usage(void) { fprintf(stderr, "%s, %s\n", SSH_VERSION, #ifdef WITH_OPENSSL OpenSSL_version(OPENSSL_VERSION) #else "without OpenSSL" #endif ); fprintf(stderr, "usage: sshd [-46DdeiqTt] [-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 send_rexec_state(int fd, struct sshbuf *conf) { struct sshbuf *m; int r; debug3("%s: entering fd = %d config len %zu", __func__, fd, sshbuf_len(conf)); /* * Protocol from reexec master to child: * string configuration */ if ((m = sshbuf_new()) == NULL) fatal("%s: sshbuf_new failed", __func__); if ((r = sshbuf_put_stringb(m, conf)) != 0) fatal("%s: buffer error: %s", __func__, ssh_err(r)); if (ssh_msg_send(fd, 0, m) == -1) fatal("%s: ssh_msg_send failed", __func__); sshbuf_free(m); debug3("%s: done", __func__); } static void recv_rexec_state(int fd, struct sshbuf *conf) { struct sshbuf *m; u_char *cp, ver; size_t len; int r; debug3("%s: entering fd = %d", __func__, fd); if ((m = sshbuf_new()) == NULL) fatal("%s: sshbuf_new failed", __func__); if (ssh_msg_recv(fd, m) == -1) fatal("%s: ssh_msg_recv failed", __func__); if ((r = sshbuf_get_u8(m, &ver)) != 0) fatal("%s: buffer error: %s", __func__, ssh_err(r)); if (ver != 0) fatal("%s: rexec version mismatch", __func__); if ((r = sshbuf_get_string(m, &cp, &len)) != 0) fatal("%s: buffer error: %s", __func__, ssh_err(r)); if (conf != NULL && (r = sshbuf_put(conf, cp, len))) fatal("%s: buffer error: %s", __func__, ssh_err(r)); free(cp); sshbuf_free(m); debug3("%s: done", __func__); } /* Accept a connection from inetd */ static void server_accept_inetd(int *sock_in, int *sock_out) { int fd; if (rexeced_flag) { close(REEXEC_CONFIG_PASS_FD); *sock_in = *sock_out = dup(STDIN_FILENO); } else { *sock_in = dup(STDIN_FILENO); *sock_out = dup(STDOUT_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 ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { dup2(fd, STDIN_FILENO); dup2(fd, STDOUT_FILENO); if (!log_stderr) dup2(fd, STDERR_FILENO); if (fd > (log_stderr ? STDERR_FILENO : STDOUT_FILENO)) close(fd); } debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); } /* * Listen for TCP connections */ static void listen_on_addrs(struct listenaddr *la) { int ret, listen_sock; struct addrinfo *ai; char ntop[NI_MAXHOST], strport[NI_MAXSERV]; for (ai = la->addrs; ai; ai = ai->ai_next) { if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) continue; if (num_listen_socks >= MAX_LISTEN_SOCKS) fatal("Too many listen sockets. " "Enlarge MAX_LISTEN_SOCKS"); if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop), strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { error("getnameinfo failed: %.100s", ssh_gai_strerror(ret)); continue; } /* Create socket for listening. */ listen_sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); if (listen_sock == -1) { /* kernel may not support ipv6 */ verbose("socket: %.100s", strerror(errno)); continue; } if (set_nonblock(listen_sock) == -1) { close(listen_sock); continue; } if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) { verbose("socket: CLOEXEC: %s", strerror(errno)); close(listen_sock); continue; } /* Socket options */ set_reuseaddr(listen_sock); if (la->rdomain != NULL && set_rdomain(listen_sock, la->rdomain) == -1) { close(listen_sock); continue; } debug("Bind to port %s on %s.", strport, ntop); /* Bind the socket to the desired port. */ if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) { error("Bind to port %s on %s failed: %.200s.", strport, ntop, strerror(errno)); close(listen_sock); continue; } listen_socks[num_listen_socks] = listen_sock; num_listen_socks++; /* Start listening on the port. */ if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1) fatal("listen on [%s]:%s: %.100s", ntop, strport, strerror(errno)); logit("Server listening on %s port %s%s%s.", ntop, strport, la->rdomain == NULL ? "" : " rdomain ", la->rdomain == NULL ? "" : la->rdomain); } } static void server_listen(void) { u_int i; for (i = 0; i < options.num_listen_addrs; i++) { listen_on_addrs(&options.listen_addrs[i]); freeaddrinfo(options.listen_addrs[i].addrs); free(options.listen_addrs[i].rdomain); memset(&options.listen_addrs[i], 0, sizeof(options.listen_addrs[i])); } free(options.listen_addrs); options.listen_addrs = NULL; options.num_listen_addrs = 0; if (!num_listen_socks) fatal("Cannot bind any address."); } /* * The main TCP accept loop. Note that, for the non-debug case, returns * from this function are in a forked subprocess. */ static void server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) { fd_set *fdset; int i, j, ret, maxfd; int startups = 0, listening = 0, lameduck = 0; int startup_p[2] = { -1 , -1 }; char c = 0; struct sockaddr_storage from; socklen_t fromlen; pid_t pid; /* setup fd set for accept */ fdset = NULL; maxfd = 0; for (i = 0; i < num_listen_socks; i++) if (listen_socks[i] > maxfd) maxfd = listen_socks[i]; /* pipes connected to unauthenticated childs */ startup_pipes = xcalloc(options.max_startups, sizeof(int)); startup_flags = xcalloc(options.max_startups, sizeof(int)); for (i = 0; i < options.max_startups; i++) startup_pipes[i] = -1; /* * Stay listening for connections until the system crashes or * the daemon is killed with a signal. */ for (;;) { if (received_sighup) { if (!lameduck) { debug("Received SIGHUP; waiting for children"); close_listen_socks(); lameduck = 1; } if (listening <= 0) sighup_restart(); } free(fdset); fdset = xcalloc(howmany(maxfd + 1, NFDBITS), sizeof(fd_mask)); for (i = 0; i < num_listen_socks; i++) FD_SET(listen_socks[i], fdset); for (i = 0; i < options.max_startups; i++) if (startup_pipes[i] != -1) FD_SET(startup_pipes[i], fdset); /* Wait in select until there is a connection. */ ret = select(maxfd+1, fdset, NULL, NULL, NULL); if (ret == -1 && errno != EINTR) error("select: %.100s", strerror(errno)); if (received_sigterm) { logit("Received signal %d; terminating.", (int) received_sigterm); close_listen_socks(); if (options.pid_file != NULL) unlink(options.pid_file); exit(received_sigterm == SIGTERM ? 0 : 255); } if (ret == -1) continue; for (i = 0; i < options.max_startups; i++) { if (startup_pipes[i] == -1 || !FD_ISSET(startup_pipes[i], fdset)) continue; switch (read(startup_pipes[i], &c, sizeof(c))) { case -1: if (errno == EINTR || errno == EAGAIN) continue; if (errno != EPIPE) { error("%s: startup pipe %d (fd=%d): " "read %s", __func__, i, startup_pipes[i], strerror(errno)); } /* FALLTHROUGH */ case 0: /* child exited or completed auth */ close(startup_pipes[i]); startup_pipes[i] = -1; startups--; if (startup_flags[i]) listening--; break; case 1: /* child has finished preliminaries */ if (startup_flags[i]) { listening--; startup_flags[i] = 0; } break; } } for (i = 0; i < num_listen_socks; i++) { if (!FD_ISSET(listen_socks[i], fdset)) continue; fromlen = sizeof(from); *newsock = accept(listen_socks[i], (struct sockaddr *)&from, &fromlen); if (*newsock == -1) { if (errno != EINTR && errno != EWOULDBLOCK && errno != ECONNABORTED) error("accept: %.100s", strerror(errno)); if (errno == EMFILE || errno == ENFILE) usleep(100 * 1000); continue; } if (unset_nonblock(*newsock) == -1) { close(*newsock); continue; } if (drop_connection(startups) == 1) { char *laddr = get_local_ipaddr(*newsock); char *raddr = get_peer_ipaddr(*newsock); verbose("drop connection #%d from [%s]:%d " "on [%s]:%d past MaxStartups", startups, raddr, get_peer_port(*newsock), laddr, get_local_port(*newsock)); free(laddr); free(raddr); close(*newsock); continue; } if (pipe(startup_p) == -1) { close(*newsock); continue; } if (rexec_flag && socketpair(AF_UNIX, SOCK_STREAM, 0, config_s) == -1) { error("reexec socketpair: %s", strerror(errno)); close(*newsock); close(startup_p[0]); close(startup_p[1]); continue; } for (j = 0; j < options.max_startups; j++) if (startup_pipes[j] == -1) { startup_pipes[j] = startup_p[0]; if (maxfd < startup_p[0]) maxfd = startup_p[0]; startups++; startup_flags[j] = 1; break; } /* * Got connection. Fork a child to handle it, unless * we are in debugging mode. */ if (debug_flag) { /* * In debugging mode. Close the listening * socket, and start processing the * connection without forking. */ debug("Server will not fork when running in debugging mode."); close_listen_socks(); *sock_in = *newsock; *sock_out = *newsock; close(startup_p[0]); close(startup_p[1]); startup_pipe = -1; pid = getpid(); if (rexec_flag) { send_rexec_state(config_s[0], cfg); close(config_s[0]); } return; } /* * Normal production daemon. Fork, and have * the child process the connection. The * parent continues listening. */ listening++; if ((pid = fork()) == 0) { /* * Child. Close the listening and * max_startup sockets. Start using * the accepted socket. Reinitialize * logging (since our pid has changed). * We return from this function to handle * the connection. */ startup_pipe = startup_p[1]; close_startup_pipes(); close_listen_socks(); *sock_in = *newsock; *sock_out = *newsock; log_init(__progname, options.log_level, options.log_facility, log_stderr); if (rexec_flag) close(config_s[0]); else { /* * Signal parent that the preliminaries * for this child are complete. For the * re-exec case, this happens after the * child has received the rexec state * from the server. */ (void)atomicio(vwrite, startup_pipe, "\0", 1); } return; } /* Parent. Stay in the loop. */ if (pid == -1) error("fork: %.100s", strerror(errno)); else debug("Forked child %ld.", (long)pid); close(startup_p[1]); if (rexec_flag) { send_rexec_state(config_s[0], cfg); close(config_s[0]); close(config_s[1]); } close(*newsock); } } } /* * 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); } return; } /* 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("%s: set routing domain %d (was %d)", __func__, rtable, ortable); } static void accumulate_host_timing_secret(struct sshbuf *server_cfg, struct sshkey *key) { static struct ssh_digest_ctx *ctx; u_char *hash; size_t len; struct sshbuf *buf; int r; if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL) fatal("%s: ssh_digest_start", __func__); if (key == NULL) { /* finalize */ /* add server config in case we are using agent for host keys */ if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg), sshbuf_len(server_cfg)) != 0) fatal("%s: ssh_digest_update", __func__); len = ssh_digest_bytes(SSH_DIGEST_SHA512); hash = xmalloc(len); if (ssh_digest_final(ctx, hash, len) != 0) fatal("%s: ssh_digest_final", __func__); options.timing_secret = PEEK_U64(hash); freezero(hash, len); ssh_digest_free(ctx); ctx = NULL; return; } if ((buf = sshbuf_new()) == NULL) fatal("%s could not allocate buffer", __func__); if ((r = sshkey_private_serialize(key, buf)) != 0) fatal("sshkey_private_serialize: %s", ssh_err(r)); if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0) fatal("%s: ssh_digest_update", __func__); sshbuf_reset(buf); sshbuf_free(buf); } /* * Main program for the daemon. */ int main(int ac, char **av) { struct ssh *ssh = NULL; extern char *optarg; extern int optind; int r, opt, on = 1, already_daemon, remote_port; int sock_in = -1, sock_out = -1, newsock = -1; const char *remote_ip, *rdomain; char *fp, *line, *laddr, *logfile = NULL; int config_s[2] = { -1 , -1 }; u_int i, j; u_int64_t ibytes, obytes; mode_t new_umask; struct sshkey *key; struct sshkey *pubkey; int keytype; Authctxt *authctxt; struct connection_info *connection_info = NULL; /* Save argv. */ saved_argv = av; rexec_argc = ac; /* 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:46DQRTdeiqrt")) != -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': no_daemon_flag = 1; break; case 'E': logfile = optarg; /* FALLTHROUGH */ case 'e': log_stderr = 1; break; case 'i': inetd_flag = 1; break; case 'r': rexec_flag = 0; break; case 'R': rexeced_flag = 1; inetd_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': test_flag = 1; break; case 'T': test_flag = 2; break; case 'C': connection_info = 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) != 0) exit(1); free(line); break; case '?': default: usage(); break; } } if (rexeced_flag || inetd_flag) rexec_flag = 0; if (!test_flag && rexec_flag && !path_absolute(av[0])) fatal("sshd re-exec requires execution with an absolute path"); if (rexeced_flag) closefrom(REEXEC_MIN_FREE_FD); else closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); #ifdef WITH_OPENSSL OpenSSL_add_all_algorithms(); #endif /* If requested, redirect the logs to the specified logfile. */ if (logfile != NULL) log_redirect_stderr_to(logfile); /* * 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); sensitive_data.have_ssh2_key = 0; /* * If we're not doing an extended test do not silently ignore connection * test params. */ if (test_flag < 2 && connection_info != NULL) fatal("Config test connection parameter (-C) provided without " "test mode (-T)"); /* Fetch our configuration */ if ((cfg = sshbuf_new()) == NULL) fatal("%s: sshbuf_new failed", __func__); if (rexeced_flag) { recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg); if (!debug_flag) { startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); close(REEXEC_STARTUP_PIPE_FD); /* * 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, "\0", 1); } } else if (strcasecmp(config_file_name, "none") != 0) load_server_config(config_file_name, cfg); parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, cfg, NULL); /* Fill in default values for those options not explicitly set. */ fill_default_server_options(&options); /* challenge-response is implemented via keyboard interactive */ if (options.challenge_response_authentication) options.kbd_interactive_authentication = 1; /* 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"); } /* 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, #ifdef WITH_OPENSSL OpenSSL_version(OPENSSL_VERSION) #else "without OpenSSL" #endif ); /* load host keys */ sensitive_data.host_keys = xcalloc(options.num_host_key_files, sizeof(struct sshkey *)); sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, sizeof(struct sshkey *)); 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("Could not connect to agent \"%s\": %s", options.host_key_agent, ssh_err(r)); } for (i = 0; i < options.num_host_key_files; i++) { int ll = options.host_key_file_userprovided[i] ? SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1; if (options.host_key_files[i] == NULL) continue; if ((r = sshkey_load_private(options.host_key_files[i], "", &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) do_log2(ll, "Unable to load host key \"%s\": %s", options.host_key_files[i], ssh_err(r)); if (r == 0 && (r = sshkey_shield_private(key)) != 0) { do_log2(ll, "Unable to shield host key \"%s\": %s", options.host_key_files[i], ssh_err(r)); sshkey_free(key); key = NULL; } if ((r = sshkey_load_public(options.host_key_files[i], &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) do_log2(ll, "Unable to load host key \"%s\": %s", options.host_key_files[i], ssh_err(r)); if (pubkey == NULL && key != NULL) if ((r = sshkey_from_private(key, &pubkey)) != 0) fatal("Could not demote key: \"%s\": %s", options.host_key_files[i], ssh_err(r)); sensitive_data.host_keys[i] = key; sensitive_data.host_pubkeys[i] = pubkey; if (key == NULL && pubkey != NULL && have_agent) { debug("will rely on agent for hostkey %s", options.host_key_files[i]); keytype = pubkey->type; } else if (key != NULL) { keytype = key->type; accumulate_host_timing_secret(cfg, key); } else { do_log2(ll, "Unable to load host key: %s", options.host_key_files[i]); sensitive_data.host_keys[i] = NULL; sensitive_data.host_pubkeys[i] = NULL; continue; } switch (keytype) { case KEY_RSA: case KEY_DSA: case KEY_ECDSA: case KEY_ED25519: case KEY_XMSS: if (have_agent || key != NULL) sensitive_data.have_ssh2_key = 1; break; } if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) fatal("sshkey_fingerprint failed"); debug("%s host key #%d: %s %s", key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp); free(fp); } accumulate_host_timing_secret(cfg, NULL); if (!sensitive_data.have_ssh2_key) { logit("sshd: no hostkeys available -- exiting."); exit(1); } /* * Load certificates. They are stored in an array at identical * indices to the public keys that they relate to. */ sensitive_data.host_certificates = xcalloc(options.num_host_key_files, sizeof(struct sshkey *)); for (i = 0; i < options.num_host_key_files; i++) sensitive_data.host_certificates[i] = NULL; for (i = 0; i < options.num_host_cert_files; i++) { if (options.host_cert_files[i] == NULL) continue; if ((r = sshkey_load_public(options.host_cert_files[i], &key, NULL)) != 0) { error("Could not load host certificate \"%s\": %s", options.host_cert_files[i], ssh_err(r)); continue; } if (!sshkey_is_cert(key)) { error("Certificate file is not a certificate: %s", options.host_cert_files[i]); sshkey_free(key); continue; } /* Find matching private key */ for (j = 0; j < options.num_host_key_files; j++) { if (sshkey_equal_public(key, sensitive_data.host_keys[j])) { sensitive_data.host_certificates[j] = key; break; } } if (j >= options.num_host_key_files) { error("No matching private key for certificate: %s", options.host_cert_files[i]); sshkey_free(key); continue; } sensitive_data.host_certificates[j] = key; debug("host certificate: #%u type %d %s", j, key->type, sshkey_type(key)); } if (use_privsep) { struct stat st; if (getpwnam(SSH_PRIVSEP_USER) == NULL) fatal("Privilege separation user %s does not exist", SSH_PRIVSEP_USER); endpwent(); if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || (S_ISDIR(st.st_mode) == 0)) fatal("Missing privilege separation directory: %s", _PATH_PRIVSEP_CHROOT_DIR); if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) fatal("%s must be owned by root and not group or " "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); } if (test_flag > 1) { /* * If no connection info was provided by -C then use * use a blank one that will cause no predicate to match. */ if (connection_info == NULL) connection_info = get_connection_info(ssh, 0, 0); connection_info->test = 1; parse_server_match_config(&options, connection_info); dump_config(&options); } /* Configuration looks good, so exit if in test mode. */ if (test_flag) exit(0); if (rexec_flag) { if (rexec_argc < 0) fatal("rexec_argc %d < 0", rexec_argc); rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); for (i = 0; i < (u_int)rexec_argc; i++) { debug("rexec_argv[%d]='%s'", i, saved_argv[i]); rexec_argv[i] = saved_argv[i]; } rexec_argv[rexec_argc] = "-R"; rexec_argv[rexec_argc + 1] = NULL; } /* 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 && (!inetd_flag || rexeced_flag)) log_stderr = 1; log_init(__progname, options.log_level, options.log_facility, log_stderr); /* * If not in debugging mode, not started from inetd and not already * daemonized (eg re-exec via SIGHUP), disconnect from the controlling * terminal, and fork. The original process exits. */ already_daemon = daemonized(); if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) { if (daemon(0, 0) == -1) fatal("daemon() failed: %.200s", strerror(errno)); disconnect_controlling_tty(); } /* 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 */ signal(SIGPIPE, SIG_IGN); /* Get a connection, either from inetd or a listening TCP socket */ if (inetd_flag) { server_accept_inetd(&sock_in, &sock_out); } else { server_listen(); signal(SIGHUP, sighup_handler); signal(SIGCHLD, main_sigchld_handler); signal(SIGTERM, sigterm_handler); signal(SIGQUIT, sigterm_handler); /* * Write out the pid file after the sigterm handler * is setup and the listen sockets are bound */ if (options.pid_file != NULL && !debug_flag) { FILE *f = fopen(options.pid_file, "w"); if (f == NULL) { error("Couldn't create pid file \"%s\": %s", options.pid_file, strerror(errno)); } else { fprintf(f, "%ld\n", (long) getpid()); fclose(f); } } /* Accept a connection and return in a forked child */ server_accept_loop(&sock_in, &sock_out, &newsock, config_s); } /* This is the child processing a new connection. */ setproctitle("%s", "[accepted]"); /* * Create a new session and process group since the 4.4BSD * setlogin() affects the entire process group. We don't * want the child to be able to affect the parent. */ if (!debug_flag && !inetd_flag && setsid() == -1) error("setsid: %.100s", strerror(errno)); if (rexec_flag) { int fd; debug("rexec start in %d out %d newsock %d pipe %d sock %d", sock_in, sock_out, newsock, startup_pipe, config_s[0]); dup2(newsock, STDIN_FILENO); dup2(STDIN_FILENO, STDOUT_FILENO); if (startup_pipe == -1) close(REEXEC_STARTUP_PIPE_FD); else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); close(startup_pipe); startup_pipe = REEXEC_STARTUP_PIPE_FD; } dup2(config_s[1], REEXEC_CONFIG_PASS_FD); close(config_s[1]); execv(rexec_argv[0], rexec_argv); /* Reexec has failed, fall back and continue */ error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); log_init(__progname, options.log_level, options.log_facility, log_stderr); /* Clean up fds */ close(REEXEC_CONFIG_PASS_FD); newsock = sock_out = sock_in = dup(STDIN_FILENO); if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { dup2(fd, STDIN_FILENO); dup2(fd, STDOUT_FILENO); if (fd > STDERR_FILENO) close(fd); } debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", sock_in, sock_out, newsock, startup_pipe, config_s[0]); } /* Executed child processes don't need these. */ fcntl(sock_out, F_SETFD, FD_CLOEXEC); fcntl(sock_in, F_SETFD, FD_CLOEXEC); /* * Disable the key regeneration alarm. We will not regenerate the * key since we are no longer in a position to give it to anyone. We * will not restart on SIGHUP since it no longer makes sense. */ alarm(0); signal(SIGALRM, SIG_DFL); signal(SIGHUP, SIG_DFL); signal(SIGTERM, SIG_DFL); signal(SIGQUIT, SIG_DFL); signal(SIGCHLD, SIG_DFL); /* * 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); process_permitopen(ssh, &options); /* 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); 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. */ signal(SIGALRM, grace_alarm_handler); if (!debug_flag) alarm(options.login_grace_time); if (kex_exchange_identification(ssh, -1, options.version_addendum) != 0) cleanup_exit(255); /* error already logged */ 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("%s: sshbuf_new failed", __func__); auth_debug_reset(); if (use_privsep) { if (privsep_preauth(ssh) == 1) goto authenticated; } else if (have_agent) { if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { error("Unable to get agent socket: %s", ssh_err(r)); have_agent = 0; } } /* perform the key exchange */ /* authenticate user and start session */ do_ssh2_kex(ssh); do_authentication2(ssh); /* * If we use privilege separation, the unprivileged child transfers * the current keystate and exits */ if (use_privsep) { mm_send_keystate(ssh, pmonitor); ssh_packet_clear_keys(ssh); exit(0); } authenticated: /* * Cancel the alarm we set to limit the time taken for * authentication. */ alarm(0); signal(SIGALRM, SIG_DFL); authctxt->authenticated = 1; if (startup_pipe != -1) { close(startup_pipe); startup_pipe = -1; } if (options.routing_domain != NULL) set_process_rdomain(ssh, options.routing_domain); /* * In privilege separation, we fork another child and prepare * file descriptor passing. */ if (use_privsep) { 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); verbose("Closing connection to %.500s port %d", remote_ip, remote_port); ssh_packet_close(ssh); if (use_privsep) 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) { int r; if (use_privsep) { if (privkey) { if (mm_sshkey_sign(ssh, privkey, signature, slenp, data, dlen, alg, ssh->compat) < 0) fatal("%s: privkey sign failed", __func__); } else { if (mm_sshkey_sign(ssh, pubkey, signature, slenp, data, dlen, alg, ssh->compat) < 0) fatal("%s: pubkey sign failed", __func__); } } else { if (privkey) { if (sshkey_sign(privkey, signature, slenp, data, dlen, alg, ssh->compat) < 0) fatal("%s: privkey sign failed", __func__); } else { if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slenp, data, dlen, alg, ssh->compat)) != 0) { fatal("%s: agent sign failed: %s", __func__, ssh_err(r)); } } } return 0; } /* SSH2 key exchange */ static void do_ssh2_kex(struct ssh *ssh) { char *myproposal[PROPOSAL_MAX] = { KEX_SERVER }; struct kex *kex; int r; myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal( options.kex_algorithms); myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal( options.ciphers); myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal( options.ciphers); myproposal[PROPOSAL_MAC_ALGS_CTOS] = myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; if (options.compression == COMP_NONE) { myproposal[PROPOSAL_COMP_ALGS_CTOS] = myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; } if (options.rekey_limit || options.rekey_interval) ssh_packet_set_rekey_limits(ssh, options.rekey_limit, options.rekey_interval); myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal( list_hostkey_types()); /* start key exchange */ if ((r = kex_setup(ssh, myproposal)) != 0) fatal("kex_setup: %s", ssh_err(r)); kex = ssh->kex; #ifdef WITH_OPENSSL kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; kex->kex[KEX_ECDH_SHA2] = kex_gen_server; #endif kex->kex[KEX_C25519_SHA256] = kex_gen_server; kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server; kex->load_host_public_key=&get_hostkey_public_by_type; kex->load_host_private_key=&get_hostkey_private_by_type; kex->host_key_index=&get_hostkey_index; kex->sign = sshd_hostkey_sign; ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done); session_id2 = kex->session_id; session_id2_len = kex->session_id_len; #ifdef DEBUG_KEXDH /* send 1st encrypted/maced/compressed message */ packet_start(SSH2_MSG_IGNORE); packet_put_cstring("markus"); packet_send(); packet_write_wait(); #endif debug("KEX done"); } /* server specific fatal cleanup */ void cleanup_exit(int i) { if (the_active_state != NULL && the_authctxt != NULL) { do_cleanup(the_active_state, the_authctxt); if (use_privsep && 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("%s: kill(%d): %s", __func__, pmonitor->m_pid, strerror(errno)); } } _exit(i); }