IABSD.fr/src/usr.bin/ssh/ssh.c

Branch : - branch - master - tag -

• Show log

  Commit

• Author : dtucker
  Date : 2020-07-17 03:43:42
  Hash : 6e617869
  Message : Add a '%k' TOKEN that expands to the effective HostKey of the destination. This allows, eg, keeping host keys in individual files using "UserKnownHostsFile ~/.ssh/known_hosts.d/%k". bz#1654, ok djm@, jmc@ (man page bits)

• usr.bin/ssh/ssh.c

• /* $OpenBSD: ssh.c,v 1.533 2020/07/17 03:43:42 dtucker Exp $ */
  /*
   * Author: Tatu Ylonen <ylo@cs.hut.fi>
   * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   *                    All rights reserved
   * Ssh client program.  This program can be used to log into a remote machine.
   * The software supports strong authentication, encryption, and forwarding
   * of X11, TCP/IP, and authentication 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".
   *
   * Copyright (c) 1999 Niels Provos.  All rights reserved.
   * Copyright (c) 2000, 2001, 2002, 2003 Markus Friedl.  All rights reserved.
   *
   * Modified to work with SSLeay by Niels Provos <provos@citi.umich.edu>
   * in Canada (German citizen).
   *
   * 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 <sys/types.h>
  #include <sys/ioctl.h>
  #include <sys/queue.h>
  #include <sys/resource.h>
  #include <sys/socket.h>
  #include <sys/stat.h>
  #include <sys/time.h>
  #include <sys/wait.h>
  
  #include <ctype.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <netdb.h>
  #include <paths.h>
  #include <pwd.h>
  #include <signal.h>
  #include <stddef.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <stdarg.h>
  #include <unistd.h>
  #include <limits.h>
  #include <locale.h>
  
  #ifdef WITH_OPENSSL
  #include <openssl/evp.h>
  #include <openssl/err.h>
  #endif
  
  #include "xmalloc.h"
  #include "ssh.h"
  #include "ssh2.h"
  #include "canohost.h"
  #include "compat.h"
  #include "cipher.h"
  #include "packet.h"
  #include "sshbuf.h"
  #include "channels.h"
  #include "sshkey.h"
  #include "authfd.h"
  #include "authfile.h"
  #include "pathnames.h"
  #include "dispatch.h"
  #include "clientloop.h"
  #include "log.h"
  #include "misc.h"
  #include "readconf.h"
  #include "sshconnect.h"
  #include "kex.h"
  #include "mac.h"
  #include "sshpty.h"
  #include "match.h"
  #include "msg.h"
  #include "version.h"
  #include "ssherr.h"
  #include "myproposal.h"
  
  #ifdef ENABLE_PKCS11
  #include "ssh-pkcs11.h"
  #endif
  
  extern char *__progname;
  
  /* Flag indicating whether debug mode is on.  May be set on the command line. */
  int debug_flag = 0;
  
  /* Flag indicating whether a tty should be requested */
  int tty_flag = 0;
  
  /* don't exec a shell */
  int no_shell_flag = 0;
  
  /*
   * Flag indicating that nothing should be read from stdin.  This can be set
   * on the command line.
   */
  int stdin_null_flag = 0;
  
  /*
   * Flag indicating that the current process should be backgrounded and
   * a new mux-client launched in the foreground for ControlPersist.
   */
  int need_controlpersist_detach = 0;
  
  /* Copies of flags for ControlPersist foreground mux-client */
  int ostdin_null_flag, ono_shell_flag, otty_flag, orequest_tty;
  
  /*
   * Flag indicating that ssh should fork after authentication.  This is useful
   * so that the passphrase can be entered manually, and then ssh goes to the
   * background.
   */
  int fork_after_authentication_flag = 0;
  
  /*
   * General data structure for command line options and options configurable
   * in configuration files.  See readconf.h.
   */
  Options options;
  
  /* optional user configfile */
  char *config = NULL;
  
  /*
   * Name of the host we are connecting to.  This is the name given on the
   * command line, or the Hostname specified for the user-supplied name in a
   * configuration file.
   */
  char *host;
  
  /*
   * A config can specify a path to forward, overriding SSH_AUTH_SOCK. If this is
   * not NULL, forward the socket at this path instead.
   */
  char *forward_agent_sock_path = NULL;
  
  /* Various strings used to to percent_expand() arguments */
  static char thishost[NI_MAXHOST], shorthost[NI_MAXHOST], portstr[NI_MAXSERV];
  static char uidstr[32], *host_arg, *conn_hash_hex;
  static const char *keyalias;
  
  /* socket address the host resolves to */
  struct sockaddr_storage hostaddr;
  
  /* Private host keys. */
  Sensitive sensitive_data;
  
  /* command to be executed */
  struct sshbuf *command;
  
  /* Should we execute a command or invoke a subsystem? */
  int subsystem_flag = 0;
  
  /* # of replies received for global requests */
  static int forward_confirms_pending = -1;
  
  /* mux.c */
  extern int muxserver_sock;
  extern u_int muxclient_command;
  
  /* Prints a help message to the user.  This function never returns. */
  
  static void
  usage(void)
  {
  	fprintf(stderr,
  "usage: ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface]\n"
  "           [-b bind_address] [-c cipher_spec] [-D [bind_address:]port]\n"
  "           [-E log_file] [-e escape_char] [-F configfile] [-I pkcs11]\n"
  "           [-i identity_file] [-J [user@]host[:port]] [-L address]\n"
  "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
  "           [-Q query_option] [-R address] [-S ctl_path] [-W host:port]\n"
  "           [-w local_tun[:remote_tun]] destination [command]\n"
  	);
  	exit(255);
  }
  
  static int ssh_session2(struct ssh *, struct passwd *);
  static void load_public_identity_files(struct passwd *);
  static void main_sigchld_handler(int);
  
  /* ~/ expand a list of paths. NB. assumes path[n] is heap-allocated. */
  static void
  tilde_expand_paths(char **paths, u_int num_paths)
  {
  	u_int i;
  	char *cp;
  
  	for (i = 0; i < num_paths; i++) {
  		cp = tilde_expand_filename(paths[i], getuid());
  		free(paths[i]);
  		paths[i] = cp;
  	}
  }
  
  #define DEFAULT_CLIENT_PERCENT_EXPAND_ARGS \
      "C", conn_hash_hex, \
      "L", shorthost, \
      "i", uidstr, \
      "k", keyalias, \
      "l", thishost, \
      "n", host_arg, \
      "p", portstr
  
  /*
   * Expands the set of percent_expand options used by the majority of keywords
   * in the client that support percent expansion.
   * Caller must free returned string.
   */
  static char *
  default_client_percent_expand(const char *str, const char *homedir,
      const char *remhost, const char *remuser, const char *locuser)
  {
  	return percent_expand(str,
  	    /* values from statics above */
  	    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
  	    /* values from arguments */
  	    "d", homedir,
  	    "h", remhost,
  	    "r", remuser,
  	    "u", locuser,
  	    (char *)NULL);
  }
  
  /*
   * Expands the set of percent_expand options used by the majority of keywords
   * AND perform environment variable substitution.
   * Caller must free returned string.
   */
  static char *
  default_client_percent_dollar_expand(const char *str, const char *homedir,
      const char *remhost, const char *remuser, const char *locuser)
  {
  	char *ret;
  
  	ret = percent_dollar_expand(str,
  	    /* values from statics above */
  	    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
  	    /* values from arguments */
  	    "d", homedir,
  	    "h", remhost,
  	    "r", remuser,
  	    "u", locuser,
  	    (char *)NULL);
  	if (ret == NULL)
  		fatal("invalid environment variable expansion");
  	return ret;
  }
  
  /*
   * Attempt to resolve a host name / port to a set of addresses and
   * optionally return any CNAMEs encountered along the way.
   * Returns NULL on failure.
   * NB. this function must operate with a options having undefined members.
   */
  static struct addrinfo *
  resolve_host(const char *name, int port, int logerr, char *cname, size_t clen)
  {
  	char strport[NI_MAXSERV];
  	struct addrinfo hints, *res;
  	int gaierr;
  	LogLevel loglevel = SYSLOG_LEVEL_DEBUG1;
  
  	if (port <= 0)
  		port = default_ssh_port();
  	if (cname != NULL)
  		*cname = '\0';
  
  	snprintf(strport, sizeof strport, "%d", port);
  	memset(&hints, 0, sizeof(hints));
  	hints.ai_family = options.address_family == -1 ?
  	    AF_UNSPEC : options.address_family;
  	hints.ai_socktype = SOCK_STREAM;
  	if (cname != NULL)
  		hints.ai_flags = AI_CANONNAME;
  	if ((gaierr = getaddrinfo(name, strport, &hints, &res)) != 0) {
  		if (logerr || (gaierr != EAI_NONAME && gaierr != EAI_NODATA))
  			loglevel = SYSLOG_LEVEL_ERROR;
  		do_log2(loglevel, "%s: Could not resolve hostname %.100s: %s",
  		    __progname, name, ssh_gai_strerror(gaierr));
  		return NULL;
  	}
  	if (cname != NULL && res->ai_canonname != NULL) {
  		if (strlcpy(cname, res->ai_canonname, clen) >= clen) {
  			error("%s: host \"%s\" cname \"%s\" too long (max %lu)",
  			    __func__, name,  res->ai_canonname, (u_long)clen);
  			if (clen > 0)
  				*cname = '\0';
  		}
  	}
  	return res;
  }
  
  /* Returns non-zero if name can only be an address and not a hostname */
  static int
  is_addr_fast(const char *name)
  {
  	return (strchr(name, '%') != NULL || strchr(name, ':') != NULL ||
  	    strspn(name, "0123456789.") == strlen(name));
  }
  
  /* Returns non-zero if name represents a valid, single address */
  static int
  is_addr(const char *name)
  {
  	char strport[NI_MAXSERV];
  	struct addrinfo hints, *res;
  
  	if (is_addr_fast(name))
  		return 1;
  
  	snprintf(strport, sizeof strport, "%u", default_ssh_port());
  	memset(&hints, 0, sizeof(hints));
  	hints.ai_family = options.address_family == -1 ?
  	    AF_UNSPEC : options.address_family;
  	hints.ai_socktype = SOCK_STREAM;
  	hints.ai_flags = AI_NUMERICHOST|AI_NUMERICSERV;
  	if (getaddrinfo(name, strport, &hints, &res) != 0)
  		return 0;
  	if (res == NULL || res->ai_next != NULL) {
  		freeaddrinfo(res);
  		return 0;
  	}
  	freeaddrinfo(res);
  	return 1;
  }
  
  /*
   * Attempt to resolve a numeric host address / port to a single address.
   * Returns a canonical address string.
   * Returns NULL on failure.
   * NB. this function must operate with a options having undefined members.
   */
  static struct addrinfo *
  resolve_addr(const char *name, int port, char *caddr, size_t clen)
  {
  	char addr[NI_MAXHOST], strport[NI_MAXSERV];
  	struct addrinfo hints, *res;
  	int gaierr;
  
  	if (port <= 0)
  		port = default_ssh_port();
  	snprintf(strport, sizeof strport, "%u", port);
  	memset(&hints, 0, sizeof(hints));
  	hints.ai_family = options.address_family == -1 ?
  	    AF_UNSPEC : options.address_family;
  	hints.ai_socktype = SOCK_STREAM;
  	hints.ai_flags = AI_NUMERICHOST|AI_NUMERICSERV;
  	if ((gaierr = getaddrinfo(name, strport, &hints, &res)) != 0) {
  		debug2("%s: could not resolve name %.100s as address: %s",
  		    __func__, name, ssh_gai_strerror(gaierr));
  		return NULL;
  	}
  	if (res == NULL) {
  		debug("%s: getaddrinfo %.100s returned no addresses",
  		 __func__, name);
  		return NULL;
  	}
  	if (res->ai_next != NULL) {
  		debug("%s: getaddrinfo %.100s returned multiple addresses",
  		    __func__, name);
  		goto fail;
  	}
  	if ((gaierr = getnameinfo(res->ai_addr, res->ai_addrlen,
  	    addr, sizeof(addr), NULL, 0, NI_NUMERICHOST)) != 0) {
  		debug("%s: Could not format address for name %.100s: %s",
  		    __func__, name, ssh_gai_strerror(gaierr));
  		goto fail;
  	}
  	if (strlcpy(caddr, addr, clen) >= clen) {
  		error("%s: host \"%s\" addr \"%s\" too long (max %lu)",
  		    __func__, name,  addr, (u_long)clen);
  		if (clen > 0)
  			*caddr = '\0';
   fail:
  		freeaddrinfo(res);
  		return NULL;
  	}
  	return res;
  }
  
  /*
   * Check whether the cname is a permitted replacement for the hostname
   * and perform the replacement if it is.
   * NB. this function must operate with a options having undefined members.
   */
  static int
  check_follow_cname(int direct, char **namep, const char *cname)
  {
  	int i;
  	struct allowed_cname *rule;
  
  	if (*cname == '\0' || options.num_permitted_cnames == 0 ||
  	    strcmp(*namep, cname) == 0)
  		return 0;
  	if (options.canonicalize_hostname == SSH_CANONICALISE_NO)
  		return 0;
  	/*
  	 * Don't attempt to canonicalize names that will be interpreted by
  	 * a proxy or jump host unless the user specifically requests so.
  	 */
  	if (!direct &&
  	    options.canonicalize_hostname != SSH_CANONICALISE_ALWAYS)
  		return 0;
  	debug3("%s: check \"%s\" CNAME \"%s\"", __func__, *namep, cname);
  	for (i = 0; i < options.num_permitted_cnames; i++) {
  		rule = options.permitted_cnames + i;
  		if (match_pattern_list(*namep, rule->source_list, 1) != 1 ||
  		    match_pattern_list(cname, rule->target_list, 1) != 1)
  			continue;
  		verbose("Canonicalized DNS aliased hostname "
  		    "\"%s\" => \"%s\"", *namep, cname);
  		free(*namep);
  		*namep = xstrdup(cname);
  		return 1;
  	}
  	return 0;
  }
  
  /*
   * Attempt to resolve the supplied hostname after applying the user's
   * canonicalization rules. Returns the address list for the host or NULL
   * if no name was found after canonicalization.
   * NB. this function must operate with a options having undefined members.
   */
  static struct addrinfo *
  resolve_canonicalize(char **hostp, int port)
  {
  	int i, direct, ndots;
  	char *cp, *fullhost, newname[NI_MAXHOST];
  	struct addrinfo *addrs;
  
  	/*
  	 * Attempt to canonicalise addresses, regardless of
  	 * whether hostname canonicalisation was requested
  	 */
  	if ((addrs = resolve_addr(*hostp, port,
  	    newname, sizeof(newname))) != NULL) {
  		debug2("%s: hostname %.100s is address", __func__, *hostp);
  		if (strcasecmp(*hostp, newname) != 0) {
  			debug2("%s: canonicalised address \"%s\" => \"%s\"",
  			    __func__, *hostp, newname);
  			free(*hostp);
  			*hostp = xstrdup(newname);
  		}
  		return addrs;
  	}
  
  	/*
  	 * If this looks like an address but didn't parse as one, it might
  	 * be an address with an invalid interface scope. Skip further
  	 * attempts at canonicalisation.
  	 */
  	if (is_addr_fast(*hostp)) {
  		debug("%s: hostname %.100s is an unrecognised address",
  		    __func__, *hostp);
  		return NULL;
  	}
  
  	if (options.canonicalize_hostname == SSH_CANONICALISE_NO)
  		return NULL;
  
  	/*
  	 * Don't attempt to canonicalize names that will be interpreted by
  	 * a proxy unless the user specifically requests so.
  	 */
  	direct = option_clear_or_none(options.proxy_command) &&
  	    options.jump_host == NULL;
  	if (!direct &&
  	    options.canonicalize_hostname != SSH_CANONICALISE_ALWAYS)
  		return NULL;
  
  	/* If domain name is anchored, then resolve it now */
  	if ((*hostp)[strlen(*hostp) - 1] == '.') {
  		debug3("%s: name is fully qualified", __func__);
  		fullhost = xstrdup(*hostp);
  		if ((addrs = resolve_host(fullhost, port, 0,
  		    newname, sizeof(newname))) != NULL)
  			goto found;
  		free(fullhost);
  		goto notfound;
  	}
  
  	/* Don't apply canonicalization to sufficiently-qualified hostnames */
  	ndots = 0;
  	for (cp = *hostp; *cp != '\0'; cp++) {
  		if (*cp == '.')
  			ndots++;
  	}
  	if (ndots > options.canonicalize_max_dots) {
  		debug3("%s: not canonicalizing hostname \"%s\" (max dots %d)",
  		    __func__, *hostp, options.canonicalize_max_dots);
  		return NULL;
  	}
  	/* Attempt each supplied suffix */
  	for (i = 0; i < options.num_canonical_domains; i++) {
  		xasprintf(&fullhost, "%s.%s.", *hostp,
  		    options.canonical_domains[i]);
  		debug3("%s: attempting \"%s\" => \"%s\"", __func__,
  		    *hostp, fullhost);
  		if ((addrs = resolve_host(fullhost, port, 0,
  		    newname, sizeof(newname))) == NULL) {
  			free(fullhost);
  			continue;
  		}
   found:
  		/* Remove trailing '.' */
  		fullhost[strlen(fullhost) - 1] = '\0';
  		/* Follow CNAME if requested */
  		if (!check_follow_cname(direct, &fullhost, newname)) {
  			debug("Canonicalized hostname \"%s\" => \"%s\"",
  			    *hostp, fullhost);
  		}
  		free(*hostp);
  		*hostp = fullhost;
  		return addrs;
  	}
   notfound:
  	if (!options.canonicalize_fallback_local)
  		fatal("%s: Could not resolve host \"%s\"", __progname, *hostp);
  	debug2("%s: host %s not found in any suffix", __func__, *hostp);
  	return NULL;
  }
  
  /*
   * Check the result of hostkey loading, ignoring some errors and
   * fatal()ing for others.
   */
  static void
  check_load(int r, const char *path, const char *message)
  {
  	switch (r) {
  	case 0:
  		break;
  	case SSH_ERR_INTERNAL_ERROR:
  	case SSH_ERR_ALLOC_FAIL:
  		fatal("load %s \"%s\": %s", message, path, ssh_err(r));
  	case SSH_ERR_SYSTEM_ERROR:
  		/* Ignore missing files */
  		if (errno == ENOENT)
  			break;
  		/* FALLTHROUGH */
  	default:
  		error("load %s \"%s\": %s", message, path, ssh_err(r));
  		break;
  	}
  }
  
  /*
   * Read per-user configuration file.  Ignore the system wide config
   * file if the user specifies a config file on the command line.
   */
  static void
  process_config_files(const char *host_name, struct passwd *pw, int final_pass,
      int *want_final_pass)
  {
  	char buf[PATH_MAX];
  	int r;
  
  	if (config != NULL) {
  		if (strcasecmp(config, "none") != 0 &&
  		    !read_config_file(config, pw, host, host_name, &options,
  		    SSHCONF_USERCONF | (final_pass ? SSHCONF_FINAL : 0),
  		    want_final_pass))
  			fatal("Can't open user config file %.100s: "
  			    "%.100s", config, strerror(errno));
  	} else {
  		r = snprintf(buf, sizeof buf, "%s/%s", pw->pw_dir,
  		    _PATH_SSH_USER_CONFFILE);
  		if (r > 0 && (size_t)r < sizeof(buf))
  			(void)read_config_file(buf, pw, host, host_name,
  			    &options, SSHCONF_CHECKPERM | SSHCONF_USERCONF |
  			    (final_pass ? SSHCONF_FINAL : 0), want_final_pass);
  
  		/* Read systemwide configuration file after user config. */
  		(void)read_config_file(_PATH_HOST_CONFIG_FILE, pw,
  		    host, host_name, &options,
  		    final_pass ? SSHCONF_FINAL : 0, want_final_pass);
  	}
  }
  
  /* Rewrite the port number in an addrinfo list of addresses */
  static void
  set_addrinfo_port(struct addrinfo *addrs, int port)
  {
  	struct addrinfo *addr;
  
  	for (addr = addrs; addr != NULL; addr = addr->ai_next) {
  		switch (addr->ai_family) {
  		case AF_INET:
  			((struct sockaddr_in *)addr->ai_addr)->
  			    sin_port = htons(port);
  			break;
  		case AF_INET6:
  			((struct sockaddr_in6 *)addr->ai_addr)->
  			    sin6_port = htons(port);
  			break;
  		}
  	}
  }
  
  /*
   * Main program for the ssh client.
   */
  int
  main(int ac, char **av)
  {
  	struct ssh *ssh = NULL;
  	int i, r, opt, exit_status, use_syslog, direct, timeout_ms;
  	int was_addr, config_test = 0, opt_terminated = 0, want_final_pass = 0;
  	char *p, *cp, *line, *argv0, *logfile;
  	char cname[NI_MAXHOST];
  	struct stat st;
  	struct passwd *pw;
  	extern int optind, optreset;
  	extern char *optarg;
  	struct Forward fwd;
  	struct addrinfo *addrs = NULL;
  	size_t n, len;
  	u_int j;
  
  	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
  	sanitise_stdfd();
  
  	/*
  	 * Discard other fds that are hanging around. These can cause problem
  	 * with backgrounded ssh processes started by ControlPersist.
  	 */
  	closefrom(STDERR_FILENO + 1);
  
  	if (getuid() != geteuid())
  		fatal("ssh setuid not supported.");
  	if (getgid() != getegid())
  		fatal("ssh setgid not supported.");
  
  	/* Get user data. */
  	pw = getpwuid(getuid());
  	if (!pw) {
  		logit("No user exists for uid %lu", (u_long)getuid());
  		exit(255);
  	}
  	/* Take a copy of the returned structure. */
  	pw = pwcopy(pw);
  
  	/*
  	 * Set our umask to something reasonable, as some files are created
  	 * with the default umask.  This will make them world-readable but
  	 * writable only by the owner, which is ok for all files for which we
  	 * don't set the modes explicitly.
  	 */
  	umask(022);
  
  	setlocale(LC_CTYPE, "");
  
  	/*
  	 * Initialize option structure to indicate that no values have been
  	 * set.
  	 */
  	initialize_options(&options);
  
  	/*
  	 * Prepare main ssh transport/connection structures
  	 */
  	if ((ssh = ssh_alloc_session_state()) == NULL)
  		fatal("Couldn't allocate session state");
  	channel_init_channels(ssh);
  
  	/* Parse command-line arguments. */
  	host = NULL;
  	use_syslog = 0;
  	logfile = NULL;
  	argv0 = av[0];
  
   again:
  	while ((opt = getopt(ac, av, "1246ab:c:e:fgi:kl:m:no:p:qstvx"
  	    "AB:CD:E:F:GI:J:KL:MNO:PQ:R:S:TVw:W:XYy")) != -1) {
  		switch (opt) {
  		case '1':
  			fatal("SSH protocol v.1 is no longer supported");
  			break;
  		case '2':
  			/* Ignored */
  			break;
  		case '4':
  			options.address_family = AF_INET;
  			break;
  		case '6':
  			options.address_family = AF_INET6;
  			break;
  		case 'n':
  			stdin_null_flag = 1;
  			break;
  		case 'f':
  			fork_after_authentication_flag = 1;
  			stdin_null_flag = 1;
  			break;
  		case 'x':
  			options.forward_x11 = 0;
  			break;
  		case 'X':
  			options.forward_x11 = 1;
  			break;
  		case 'y':
  			use_syslog = 1;
  			break;
  		case 'E':
  			logfile = optarg;
  			break;
  		case 'G':
  			config_test = 1;
  			break;
  		case 'Y':
  			options.forward_x11 = 1;
  			options.forward_x11_trusted = 1;
  			break;
  		case 'g':
  			options.fwd_opts.gateway_ports = 1;
  			break;
  		case 'O':
  			if (options.stdio_forward_host != NULL)
  				fatal("Cannot specify multiplexing "
  				    "command with -W");
  			else if (muxclient_command != 0)
  				fatal("Multiplexing command already specified");
  			if (strcmp(optarg, "check") == 0)
  				muxclient_command = SSHMUX_COMMAND_ALIVE_CHECK;
  			else if (strcmp(optarg, "forward") == 0)
  				muxclient_command = SSHMUX_COMMAND_FORWARD;
  			else if (strcmp(optarg, "exit") == 0)
  				muxclient_command = SSHMUX_COMMAND_TERMINATE;
  			else if (strcmp(optarg, "stop") == 0)
  				muxclient_command = SSHMUX_COMMAND_STOP;
  			else if (strcmp(optarg, "cancel") == 0)
  				muxclient_command = SSHMUX_COMMAND_CANCEL_FWD;
  			else if (strcmp(optarg, "proxy") == 0)
  				muxclient_command = SSHMUX_COMMAND_PROXY;
  			else
  				fatal("Invalid multiplex command.");
  			break;
  		case 'P':	/* deprecated */
  			break;
  		case 'Q':
  			cp = NULL;
  			if (strcmp(optarg, "cipher") == 0 ||
  			    strcasecmp(optarg, "Ciphers") == 0)
  				cp = cipher_alg_list('\n', 0);
  			else if (strcmp(optarg, "cipher-auth") == 0)
  				cp = cipher_alg_list('\n', 1);
  			else if (strcmp(optarg, "mac") == 0 ||
  			    strcasecmp(optarg, "MACs") == 0)
  				cp = mac_alg_list('\n');
  			else if (strcmp(optarg, "kex") == 0 ||
  			    strcasecmp(optarg, "KexAlgorithms") == 0)
  				cp = kex_alg_list('\n');
  			else if (strcmp(optarg, "key") == 0)
  				cp = sshkey_alg_list(0, 0, 0, '\n');
  			else if (strcmp(optarg, "key-cert") == 0)
  				cp = sshkey_alg_list(1, 0, 0, '\n');
  			else if (strcmp(optarg, "key-plain") == 0)
  				cp = sshkey_alg_list(0, 1, 0, '\n');
  			else if (strcmp(optarg, "key-sig") == 0 ||
  			    strcasecmp(optarg, "PubkeyAcceptedKeyTypes") == 0 ||
  			    strcasecmp(optarg, "HostKeyAlgorithms") == 0 ||
  			    strcasecmp(optarg, "HostbasedKeyTypes") == 0 ||
  			    strcasecmp(optarg, "HostbasedAcceptedKeyTypes") == 0)
  				cp = sshkey_alg_list(0, 0, 1, '\n');
  			else if (strcmp(optarg, "sig") == 0)
  				cp = sshkey_alg_list(0, 1, 1, '\n');
  			else if (strcmp(optarg, "protocol-version") == 0)
  				cp = xstrdup("2");
  			else if (strcmp(optarg, "compression") == 0) {
  				cp = xstrdup(compression_alg_list(0));
  				len = strlen(cp);
  				for (n = 0; n < len; n++)
  					if (cp[n] == ',')
  						cp[n] = '\n';
  			} else if (strcmp(optarg, "help") == 0) {
  				cp = xstrdup(
  				    "cipher\ncipher-auth\ncompression\nkex\n"
  				    "key\nkey-cert\nkey-plain\nkey-sig\nmac\n"
  				    "protocol-version\nsig");
  			}
  			if (cp == NULL)
  				fatal("Unsupported query \"%s\"", optarg);
  			printf("%s\n", cp);
  			free(cp);
  			exit(0);
  			break;
  		case 'a':
  			options.forward_agent = 0;
  			break;
  		case 'A':
  			options.forward_agent = 1;
  			break;
  		case 'k':
  			options.gss_deleg_creds = 0;
  			break;
  		case 'K':
  			options.gss_authentication = 1;
  			options.gss_deleg_creds = 1;
  			break;
  		case 'i':
  			p = tilde_expand_filename(optarg, getuid());
  			if (stat(p, &st) == -1)
  				fprintf(stderr, "Warning: Identity file %s "
  				    "not accessible: %s.\n", p,
  				    strerror(errno));
  			else
  				add_identity_file(&options, NULL, p, 1);
  			free(p);
  			break;
  		case 'I':
  #ifdef ENABLE_PKCS11
  			free(options.pkcs11_provider);
  			options.pkcs11_provider = xstrdup(optarg);
  #else
  			fprintf(stderr, "no support for PKCS#11.\n");
  #endif
  			break;
  		case 'J':
  			if (options.jump_host != NULL) {
  				fatal("Only a single -J option is permitted "
  				    "(use commas to separate multiple "
  				    "jump hops)");
  			}
  			if (options.proxy_command != NULL)
  				fatal("Cannot specify -J with ProxyCommand");
  			if (parse_jump(optarg, &options, 1) == -1)
  				fatal("Invalid -J argument");
  			options.proxy_command = xstrdup("none");
  			break;
  		case 't':
  			if (options.request_tty == REQUEST_TTY_YES)
  				options.request_tty = REQUEST_TTY_FORCE;
  			else
  				options.request_tty = REQUEST_TTY_YES;
  			break;
  		case 'v':
  			if (debug_flag == 0) {
  				debug_flag = 1;
  				options.log_level = SYSLOG_LEVEL_DEBUG1;
  			} else {
  				if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
  					debug_flag++;
  					options.log_level++;
  				}
  			}
  			break;
  		case 'V':
  			fprintf(stderr, "%s, %s\n",
  			    SSH_VERSION,
  #ifdef WITH_OPENSSL
  			    OpenSSL_version(OPENSSL_VERSION)
  #else
  			    "without OpenSSL"
  #endif
  			);
  			if (opt == 'V')
  				exit(0);
  			break;
  		case 'w':
  			if (options.tun_open == -1)
  				options.tun_open = SSH_TUNMODE_DEFAULT;
  			options.tun_local = a2tun(optarg, &options.tun_remote);
  			if (options.tun_local == SSH_TUNID_ERR) {
  				fprintf(stderr,
  				    "Bad tun device '%s'\n", optarg);
  				exit(255);
  			}
  			break;
  		case 'W':
  			if (options.stdio_forward_host != NULL)
  				fatal("stdio forward already specified");
  			if (muxclient_command != 0)
  				fatal("Cannot specify stdio forward with -O");
  			if (parse_forward(&fwd, optarg, 1, 0)) {
  				options.stdio_forward_host = fwd.listen_host;
  				options.stdio_forward_port = fwd.listen_port;
  				free(fwd.connect_host);
  			} else {
  				fprintf(stderr,
  				    "Bad stdio forwarding specification '%s'\n",
  				    optarg);
  				exit(255);
  			}
  			options.request_tty = REQUEST_TTY_NO;
  			no_shell_flag = 1;
  			break;
  		case 'q':
  			options.log_level = SYSLOG_LEVEL_QUIET;
  			break;
  		case 'e':
  			if (optarg[0] == '^' && optarg[2] == 0 &&
  			    (u_char) optarg[1] >= 64 &&
  			    (u_char) optarg[1] < 128)
  				options.escape_char = (u_char) optarg[1] & 31;
  			else if (strlen(optarg) == 1)
  				options.escape_char = (u_char) optarg[0];
  			else if (strcmp(optarg, "none") == 0)
  				options.escape_char = SSH_ESCAPECHAR_NONE;
  			else {
  				fprintf(stderr, "Bad escape character '%s'.\n",
  				    optarg);
  				exit(255);
  			}
  			break;
  		case 'c':
  			if (!ciphers_valid(*optarg == '+' || *optarg == '^' ?
  			    optarg + 1 : optarg)) {
  				fprintf(stderr, "Unknown cipher type '%s'\n",
  				    optarg);
  				exit(255);
  			}
  			free(options.ciphers);
  			options.ciphers = xstrdup(optarg);
  			break;
  		case 'm':
  			if (mac_valid(optarg)) {
  				free(options.macs);
  				options.macs = xstrdup(optarg);
  			} else {
  				fprintf(stderr, "Unknown mac type '%s'\n",
  				    optarg);
  				exit(255);
  			}
  			break;
  		case 'M':
  			if (options.control_master == SSHCTL_MASTER_YES)
  				options.control_master = SSHCTL_MASTER_ASK;
  			else
  				options.control_master = SSHCTL_MASTER_YES;
  			break;
  		case 'p':
  			if (options.port == -1) {
  				options.port = a2port(optarg);
  				if (options.port <= 0) {
  					fprintf(stderr, "Bad port '%s'\n",
  					    optarg);
  					exit(255);
  				}
  			}
  			break;
  		case 'l':
  			if (options.user == NULL)
  				options.user = optarg;
  			break;
  
  		case 'L':
  			if (parse_forward(&fwd, optarg, 0, 0))
  				add_local_forward(&options, &fwd);
  			else {
  				fprintf(stderr,
  				    "Bad local forwarding specification '%s'\n",
  				    optarg);
  				exit(255);
  			}
  			break;
  
  		case 'R':
  			if (parse_forward(&fwd, optarg, 0, 1) ||
  			    parse_forward(&fwd, optarg, 1, 1)) {
  				add_remote_forward(&options, &fwd);
  			} else {
  				fprintf(stderr,
  				    "Bad remote forwarding specification "
  				    "'%s'\n", optarg);
  				exit(255);
  			}
  			break;
  
  		case 'D':
  			if (parse_forward(&fwd, optarg, 1, 0)) {
  				add_local_forward(&options, &fwd);
  			} else {
  				fprintf(stderr,
  				    "Bad dynamic forwarding specification "
  				    "'%s'\n", optarg);
  				exit(255);
  			}
  			break;
  
  		case 'C':
  #ifdef WITH_ZLIB
  			options.compression = 1;
  #else
  			error("Compression not supported, disabling.");
  #endif
  			break;
  		case 'N':
  			no_shell_flag = 1;
  			options.request_tty = REQUEST_TTY_NO;
  			break;
  		case 'T':
  			options.request_tty = REQUEST_TTY_NO;
  			break;
  		case 'o':
  			line = xstrdup(optarg);
  			if (process_config_line(&options, pw,
  			    host ? host : "", host ? host : "", line,
  			    "command-line", 0, NULL, SSHCONF_USERCONF) != 0)
  				exit(255);
  			free(line);
  			break;
  		case 's':
  			subsystem_flag = 1;
  			break;
  		case 'S':
  			free(options.control_path);
  			options.control_path = xstrdup(optarg);
  			break;
  		case 'b':
  			options.bind_address = optarg;
  			break;
  		case 'B':
  			options.bind_interface = optarg;
  			break;
  		case 'F':
  			config = optarg;
  			break;
  		default:
  			usage();
  		}
  	}
  
  	if (optind > 1 && strcmp(av[optind - 1], "--") == 0)
  		opt_terminated = 1;
  
  	ac -= optind;
  	av += optind;
  
  	if (ac > 0 && !host) {
  		int tport;
  		char *tuser;
  		switch (parse_ssh_uri(*av, &tuser, &host, &tport)) {
  		case -1:
  			usage();
  			break;
  		case 0:
  			if (options.user == NULL) {
  				options.user = tuser;
  				tuser = NULL;
  			}
  			free(tuser);
  			if (options.port == -1 && tport != -1)
  				options.port = tport;
  			break;
  		default:
  			p = xstrdup(*av);
  			cp = strrchr(p, '@');
  			if (cp != NULL) {
  				if (cp == p)
  					usage();
  				if (options.user == NULL) {
  					options.user = p;
  					p = NULL;
  				}
  				*cp++ = '\0';
  				host = xstrdup(cp);
  				free(p);
  			} else
  				host = p;
  			break;
  		}
  		if (ac > 1 && !opt_terminated) {
  			optind = optreset = 1;
  			goto again;
  		}
  		ac--, av++;
  	}
  
  	/* Check that we got a host name. */
  	if (!host)
  		usage();
  
  	host_arg = xstrdup(host);
  
  #ifdef WITH_OPENSSL
  	OpenSSL_add_all_algorithms();
  	ERR_load_crypto_strings();
  #endif
  
  	/* Initialize the command to execute on remote host. */
  	if ((command = sshbuf_new()) == NULL)
  		fatal("sshbuf_new failed");
  
  	/*
  	 * Save the command to execute on the remote host in a buffer. There
  	 * is no limit on the length of the command, except by the maximum
  	 * packet size.  Also sets the tty flag if there is no command.
  	 */
  	if (!ac) {
  		/* No command specified - execute shell on a tty. */
  		if (subsystem_flag) {
  			fprintf(stderr,
  			    "You must specify a subsystem to invoke.\n");
  			usage();
  		}
  	} else {
  		/* A command has been specified.  Store it into the buffer. */
  		for (i = 0; i < ac; i++) {
  			if ((r = sshbuf_putf(command, "%s%s",
  			    i ? " " : "", av[i])) != 0)
  				fatal("%s: buffer error: %s",
  				    __func__, ssh_err(r));
  		}
  	}
  
  	/*
  	 * Initialize "log" output.  Since we are the client all output
  	 * goes to stderr unless otherwise specified by -y or -E.
  	 */
  	if (use_syslog && logfile != NULL)
  		fatal("Can't specify both -y and -E");
  	if (logfile != NULL)
  		log_redirect_stderr_to(logfile);
  	log_init(argv0,
  	    options.log_level == SYSLOG_LEVEL_NOT_SET ?
  	    SYSLOG_LEVEL_INFO : options.log_level,
  	    options.log_facility == SYSLOG_FACILITY_NOT_SET ?
  	    SYSLOG_FACILITY_USER : options.log_facility,
  	    !use_syslog);
  
  	if (debug_flag)
  		logit("%s, %s", SSH_VERSION,
  #ifdef WITH_OPENSSL
  		    OpenSSL_version(OPENSSL_VERSION)
  #else
  		    "without OpenSSL"
  #endif
  		);
  
  	/* Parse the configuration files */
  	process_config_files(host_arg, pw, 0, &want_final_pass);
  	if (want_final_pass)
  		debug("configuration requests final Match pass");
  
  	/* Hostname canonicalisation needs a few options filled. */
  	fill_default_options_for_canonicalization(&options);
  
  	/* If the user has replaced the hostname then take it into use now */
  	if (options.hostname != NULL) {
  		/* NB. Please keep in sync with readconf.c:match_cfg_line() */
  		cp = percent_expand(options.hostname,
  		    "h", host, (char *)NULL);
  		free(host);
  		host = cp;
  		free(options.hostname);
  		options.hostname = xstrdup(host);
  	}
  
  	/* Don't lowercase addresses, they will be explicitly canonicalised */
  	if ((was_addr = is_addr(host)) == 0)
  		lowercase(host);
  
  	/*
  	 * Try to canonicalize if requested by configuration or the
  	 * hostname is an address.
  	 */
  	if (options.canonicalize_hostname != SSH_CANONICALISE_NO || was_addr)
  		addrs = resolve_canonicalize(&host, options.port);
  
  	/*
  	 * If CanonicalizePermittedCNAMEs have been specified but
  	 * other canonicalization did not happen (by not being requested
  	 * or by failing with fallback) then the hostname may still be changed
  	 * as a result of CNAME following.
  	 *
  	 * Try to resolve the bare hostname name using the system resolver's
  	 * usual search rules and then apply the CNAME follow rules.
  	 *
  	 * Skip the lookup if a ProxyCommand is being used unless the user
  	 * has specifically requested canonicalisation for this case via
  	 * CanonicalizeHostname=always
  	 */
  	direct = option_clear_or_none(options.proxy_command) &&
  	    options.jump_host == NULL;
  	if (addrs == NULL && options.num_permitted_cnames != 0 && (direct ||
  	    options.canonicalize_hostname == SSH_CANONICALISE_ALWAYS)) {
  		if ((addrs = resolve_host(host, options.port,
  		    direct, cname, sizeof(cname))) == NULL) {
  			/* Don't fatal proxied host names not in the DNS */
  			if (direct)
  				cleanup_exit(255); /* logged in resolve_host */
  		} else
  			check_follow_cname(direct, &host, cname);
  	}
  
  	/*
  	 * If canonicalisation is enabled then re-parse the configuration
  	 * files as new stanzas may match.
  	 */
  	if (options.canonicalize_hostname != 0 && !want_final_pass) {
  		debug("hostname canonicalisation enabled, "
  		    "will re-parse configuration");
  		want_final_pass = 1;
  	}
  
  	if (want_final_pass) {
  		debug("re-parsing configuration");
  		free(options.hostname);
  		options.hostname = xstrdup(host);
  		process_config_files(host_arg, pw, 1, NULL);
  		/*
  		 * Address resolution happens early with canonicalisation
  		 * enabled and the port number may have changed since, so
  		 * reset it in address list
  		 */
  		if (addrs != NULL && options.port > 0)
  			set_addrinfo_port(addrs, options.port);
  	}
  
  	/* Fill configuration defaults. */
  	fill_default_options(&options);
  
  	/*
  	 * If ProxyJump option specified, then construct a ProxyCommand now.
  	 */
  	if (options.jump_host != NULL) {
  		char port_s[8];
  		const char *sshbin = argv0;
  		int port = options.port, jumpport = options.jump_port;
  
  		if (port <= 0)
  			port = default_ssh_port();
  		if (jumpport <= 0)
  			jumpport = default_ssh_port();
  		if (strcmp(options.jump_host, host) == 0 && port == jumpport)
  			fatal("jumphost loop via %s", options.jump_host);
  
  		/*
  		 * Try to use SSH indicated by argv[0], but fall back to
  		 * "ssh" if it appears unavailable.
  		 */
  		if (strchr(argv0, '/') != NULL && access(argv0, X_OK) != 0)
  			sshbin = "ssh";
  
  		/* Consistency check */
  		if (options.proxy_command != NULL)
  			fatal("inconsistent options: ProxyCommand+ProxyJump");
  		/* Never use FD passing for ProxyJump */
  		options.proxy_use_fdpass = 0;
  		snprintf(port_s, sizeof(port_s), "%d", options.jump_port);
  		xasprintf(&options.proxy_command,
  		    "%s%s%s%s%s%s%s%s%s%s%.*s -W '[%%h]:%%p' %s",
  		    sshbin,
  		    /* Optional "-l user" argument if jump_user set */
  		    options.jump_user == NULL ? "" : " -l ",
  		    options.jump_user == NULL ? "" : options.jump_user,
  		    /* Optional "-p port" argument if jump_port set */
  		    options.jump_port <= 0 ? "" : " -p ",
  		    options.jump_port <= 0 ? "" : port_s,
  		    /* Optional additional jump hosts ",..." */
  		    options.jump_extra == NULL ? "" : " -J ",
  		    options.jump_extra == NULL ? "" : options.jump_extra,
  		    /* Optional "-F" argumment if -F specified */
  		    config == NULL ? "" : " -F ",
  		    config == NULL ? "" : config,
  		    /* Optional "-v" arguments if -v set */
  		    debug_flag ? " -" : "",
  		    debug_flag, "vvv",
  		    /* Mandatory hostname */
  		    options.jump_host);
  		debug("Setting implicit ProxyCommand from ProxyJump: %s",
  		    options.proxy_command);
  	}
  
  	if (options.port == 0)
  		options.port = default_ssh_port();
  	channel_set_af(ssh, options.address_family);
  
  	/* Tidy and check options */
  	if (options.host_key_alias != NULL)
  		lowercase(options.host_key_alias);
  	if (options.proxy_command != NULL &&
  	    strcmp(options.proxy_command, "-") == 0 &&
  	    options.proxy_use_fdpass)
  		fatal("ProxyCommand=- and ProxyUseFDPass are incompatible");
  	if (options.update_hostkeys == SSH_UPDATE_HOSTKEYS_ASK) {
  		if (options.control_persist && options.control_path != NULL) {
  			debug("UpdateHostKeys=ask is incompatible with "
  			    "ControlPersist; disabling");
  			options.update_hostkeys = 0;
  		} else if (sshbuf_len(command) != 0 ||
  		    options.remote_command != NULL ||
  		    options.request_tty == REQUEST_TTY_NO) {
  			debug("UpdateHostKeys=ask is incompatible with "
  			    "remote command execution; disabling");
  			options.update_hostkeys = 0;
  		} else if (options.log_level < SYSLOG_LEVEL_INFO) {
  			/* no point logging anything; user won't see it */
  			options.update_hostkeys = 0;
  		}
  	}
  	if (options.connection_attempts <= 0)
  		fatal("Invalid number of ConnectionAttempts");
  
  	if (sshbuf_len(command) != 0 && options.remote_command != NULL)
  		fatal("Cannot execute command-line and remote command.");
  
  	/* Cannot fork to background if no command. */
  	if (fork_after_authentication_flag && sshbuf_len(command) == 0 &&
  	    options.remote_command == NULL && !no_shell_flag)
  		fatal("Cannot fork into background without a command "
  		    "to execute.");
  
  	/* reinit */
  	log_init(argv0, options.log_level, options.log_facility, !use_syslog);
  
  	if (options.request_tty == REQUEST_TTY_YES ||
  	    options.request_tty == REQUEST_TTY_FORCE)
  		tty_flag = 1;
  
  	/* Allocate a tty by default if no command specified. */
  	if (sshbuf_len(command) == 0 && options.remote_command == NULL)
  		tty_flag = options.request_tty != REQUEST_TTY_NO;
  
  	/* Force no tty */
  	if (options.request_tty == REQUEST_TTY_NO ||
  	    (muxclient_command && muxclient_command != SSHMUX_COMMAND_PROXY))
  		tty_flag = 0;
  	/* Do not allocate a tty if stdin is not a tty. */
  	if ((!isatty(fileno(stdin)) || stdin_null_flag) &&
  	    options.request_tty != REQUEST_TTY_FORCE) {
  		if (tty_flag)
  			logit("Pseudo-terminal will not be allocated because "
  			    "stdin is not a terminal.");
  		tty_flag = 0;
  	}
  
  	if (options.user == NULL)
  		options.user = xstrdup(pw->pw_name);
  
  	/* Set up strings used to percent_expand() arguments */
  	if (gethostname(thishost, sizeof(thishost)) == -1)
  		fatal("gethostname: %s", strerror(errno));
  	strlcpy(shorthost, thishost, sizeof(shorthost));
  	shorthost[strcspn(thishost, ".")] = '\0';
  	snprintf(portstr, sizeof(portstr), "%d", options.port);
  	snprintf(uidstr, sizeof(uidstr), "%llu",
  	    (unsigned long long)pw->pw_uid);
  	keyalias = options.host_key_alias ? options.host_key_alias : host_arg;
  
  	conn_hash_hex = ssh_connection_hash(thishost, host, portstr,
  	    options.user);
  
  	/*
  	 * Expand tokens in arguments. NB. LocalCommand is expanded later,
  	 * after port-forwarding is set up, so it may pick up any local
  	 * tunnel interface name allocated.
  	 */
  	if (options.remote_command != NULL) {
  		debug3("expanding RemoteCommand: %s", options.remote_command);
  		cp = options.remote_command;
  		options.remote_command = default_client_percent_expand(cp,
  		    pw->pw_dir, host, options.user, pw->pw_name);
  		debug3("expanded RemoteCommand: %s", options.remote_command);
  		free(cp);
  		if ((r = sshbuf_put(command, options.remote_command,
  		    strlen(options.remote_command))) != 0)
  			fatal("%s: buffer error: %s", __func__, ssh_err(r));
  	}
  
  	if (options.control_path != NULL) {
  		cp = tilde_expand_filename(options.control_path, getuid());
  		free(options.control_path);
  		options.control_path = default_client_percent_dollar_expand(cp,
  		    pw->pw_dir, host, options.user, pw->pw_name);
  		free(cp);
  	}
  
  	if (options.identity_agent != NULL) {
  		p = tilde_expand_filename(options.identity_agent, getuid());
  		cp = default_client_percent_dollar_expand(p,
  		    pw->pw_dir, host, options.user, pw->pw_name);
  		free(p);
  		free(options.identity_agent);
  		options.identity_agent = cp;
  	}
  
  	if (options.forward_agent_sock_path != NULL) {
  		p = tilde_expand_filename(options.forward_agent_sock_path,
  		    getuid());
  		cp = default_client_percent_dollar_expand(p,
  		    pw->pw_dir, host, options.user, pw->pw_name);
  		free(p);
  		free(options.forward_agent_sock_path);
  		options.forward_agent_sock_path = cp;
  	}
  
  	for (j = 0; j < options.num_user_hostfiles; j++) {
  		if (options.user_hostfiles[j] != NULL) {
  			cp = tilde_expand_filename(options.user_hostfiles[j],
  			    getuid());
  			p = default_client_percent_dollar_expand(cp,
  			    pw->pw_dir, host, options.user, pw->pw_name);
  			if (strcmp(options.user_hostfiles[j], p) != 0)
  				debug3("expanded UserKnownHostsFile '%s' -> "
  				    "'%s'", options.user_hostfiles[j], p);
  			free(options.user_hostfiles[j]);
  			free(cp);
  			options.user_hostfiles[j] = p;
  		}
  	}
  
  	for (i = 0; i < options.num_local_forwards; i++) {
  		if (options.local_forwards[i].listen_path != NULL) {
  			cp = options.local_forwards[i].listen_path;
  			p = options.local_forwards[i].listen_path =
  			    default_client_percent_expand(cp,
  			    pw->pw_dir, host, options.user, pw->pw_name);
  			if (strcmp(cp, p) != 0)
  				debug3("expanded LocalForward listen path "
  				    "'%s' -> '%s'", cp, p);
  			free(cp);
  		}
  		if (options.local_forwards[i].connect_path != NULL) {
  			cp = options.local_forwards[i].connect_path;
  			p = options.local_forwards[i].connect_path =
  			    default_client_percent_expand(cp,
  			    pw->pw_dir, host, options.user, pw->pw_name);
  			if (strcmp(cp, p) != 0)
  				debug3("expanded LocalForward connect path "
  				    "'%s' -> '%s'", cp, p);
  			free(cp);
  		}
  	}
  
  	for (i = 0; i < options.num_remote_forwards; i++) {
  		if (options.remote_forwards[i].listen_path != NULL) {
  			cp = options.remote_forwards[i].listen_path;
  			p = options.remote_forwards[i].listen_path =
  			    default_client_percent_expand(cp,
  			    pw->pw_dir, host, options.user, pw->pw_name);
  			if (strcmp(cp, p) != 0)
  				debug3("expanded RemoteForward listen path "
  				    "'%s' -> '%s'", cp, p);
  			free(cp);
  		}
  		if (options.remote_forwards[i].connect_path != NULL) {
  			cp = options.remote_forwards[i].connect_path;
  			p = options.remote_forwards[i].connect_path =
  			    default_client_percent_expand(cp,
  			    pw->pw_dir, host, options.user, pw->pw_name);
  			if (strcmp(cp, p) != 0)
  				debug3("expanded RemoteForward connect path "
  				    "'%s' -> '%s'", cp, p);
  			free(cp);
  		}
  	}
  
  	if (config_test) {
  		dump_client_config(&options, host);
  		exit(0);
  	}
  
  	/* Expand SecurityKeyProvider if it refers to an environment variable */
  	if (options.sk_provider != NULL && *options.sk_provider == '$' &&
  	    strlen(options.sk_provider) > 1) {
  		if ((cp = getenv(options.sk_provider + 1)) == NULL) {
  			debug("Authenticator provider %s did not resolve; "
  			    "disabling", options.sk_provider);
  			free(options.sk_provider);
  			options.sk_provider = NULL;
  		} else {
  			debug2("resolved SecurityKeyProvider %s => %s",
  			    options.sk_provider, cp);
  			free(options.sk_provider);
  			options.sk_provider = xstrdup(cp);
  		}
  	}
  
  	if (muxclient_command != 0 && options.control_path == NULL)
  		fatal("No ControlPath specified for \"-O\" command");
  	if (options.control_path != NULL) {
  		int sock;
  		if ((sock = muxclient(options.control_path)) >= 0) {
  			ssh_packet_set_connection(ssh, sock, sock);
  			ssh_packet_set_mux(ssh);
  			goto skip_connect;
  		}
  	}
  
  	/*
  	 * If hostname canonicalisation was not enabled, then we may not
  	 * have yet resolved the hostname. Do so now.
  	 */
  	if (addrs == NULL && options.proxy_command == NULL) {
  		debug2("resolving \"%s\" port %d", host, options.port);
  		if ((addrs = resolve_host(host, options.port, 1,
  		    cname, sizeof(cname))) == NULL)
  			cleanup_exit(255); /* resolve_host logs the error */
  	}
  
  	timeout_ms = options.connection_timeout * 1000;
  
  	/* Open a connection to the remote host. */
  	if (ssh_connect(ssh, host, host_arg, addrs, &hostaddr, options.port,
  	    options.address_family, options.connection_attempts,
  	    &timeout_ms, options.tcp_keep_alive) != 0)
  		exit(255);
  
  	if (addrs != NULL)
  		freeaddrinfo(addrs);
  
  	ssh_packet_set_timeout(ssh, options.server_alive_interval,
  	    options.server_alive_count_max);
  
  	if (timeout_ms > 0)
  		debug3("timeout: %d ms remain after connect", timeout_ms);
  
  	/*
  	 * If we successfully made the connection and we have hostbased auth
  	 * enabled, load the public keys so we can later use the ssh-keysign
  	 * helper to sign challenges.
  	 */
  	sensitive_data.nkeys = 0;
  	sensitive_data.keys = NULL;
  	if (options.hostbased_authentication) {
  		sensitive_data.nkeys = 10;
  		sensitive_data.keys = xcalloc(sensitive_data.nkeys,
  		    sizeof(struct sshkey));
  
  		/* XXX check errors? */
  #define L_PUBKEY(p,o) do { \
  	if ((o) >= sensitive_data.nkeys) \
  		fatal("%s pubkey out of array bounds", __func__); \
  	check_load(sshkey_load_public(p, &(sensitive_data.keys[o]), NULL), \
  	    p, "pubkey"); \
  } while (0)
  #define L_CERT(p,o) do { \
  	if ((o) >= sensitive_data.nkeys) \
  		fatal("%s cert out of array bounds", __func__); \
  	check_load(sshkey_load_cert(p, &(sensitive_data.keys[o])), p, "cert"); \
  } while (0)
  
  		if (options.hostbased_authentication == 1) {
  			L_CERT(_PATH_HOST_ECDSA_KEY_FILE, 0);
  			L_CERT(_PATH_HOST_ED25519_KEY_FILE, 1);
  			L_CERT(_PATH_HOST_RSA_KEY_FILE, 2);
  			L_CERT(_PATH_HOST_DSA_KEY_FILE, 3);
  			L_PUBKEY(_PATH_HOST_ECDSA_KEY_FILE, 4);
  			L_PUBKEY(_PATH_HOST_ED25519_KEY_FILE, 5);
  			L_PUBKEY(_PATH_HOST_RSA_KEY_FILE, 6);
  			L_PUBKEY(_PATH_HOST_DSA_KEY_FILE, 7);
  			L_CERT(_PATH_HOST_XMSS_KEY_FILE, 8);
  			L_PUBKEY(_PATH_HOST_XMSS_KEY_FILE, 9);
  		}
  	}
  
  	/* load options.identity_files */
  	load_public_identity_files(pw);
  
  	/* optionally set the SSH_AUTHSOCKET_ENV_NAME variable */
  	if (options.identity_agent &&
  	    strcmp(options.identity_agent, SSH_AUTHSOCKET_ENV_NAME) != 0) {
  		if (strcmp(options.identity_agent, "none") == 0) {
  			unsetenv(SSH_AUTHSOCKET_ENV_NAME);
  		} else {
  			cp = options.identity_agent;
  			/* legacy (limited) format */
  			if (cp[0] == '$' && cp[1] != '{') {
  				if (!valid_env_name(cp + 1)) {
  					fatal("Invalid IdentityAgent "
  					    "environment variable name %s", cp);
  				}
  				if ((p = getenv(cp + 1)) == NULL)
  					unsetenv(SSH_AUTHSOCKET_ENV_NAME);
  				else
  					setenv(SSH_AUTHSOCKET_ENV_NAME, p, 1);
  			} else {
  				/* identity_agent specifies a path directly */
  				setenv(SSH_AUTHSOCKET_ENV_NAME, cp, 1);
  			}
  		}
  	}
  
  	if (options.forward_agent && options.forward_agent_sock_path != NULL) {
  		cp = options.forward_agent_sock_path;
  		if (cp[0] == '$') {
  			if (!valid_env_name(cp + 1)) {
  				fatal("Invalid ForwardAgent environment variable name %s", cp);
  			}
  			if ((p = getenv(cp + 1)) != NULL)
  				forward_agent_sock_path = p;
  			else
  				options.forward_agent = 0;
  			free(cp);
  		} else {
  			forward_agent_sock_path = cp;
  		}
  	}
  
  	/* Expand ~ in known host file names. */
  	tilde_expand_paths(options.system_hostfiles,
  	    options.num_system_hostfiles);
  	tilde_expand_paths(options.user_hostfiles, options.num_user_hostfiles);
  
  	ssh_signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
  	ssh_signal(SIGCHLD, main_sigchld_handler);
  
  	/* Log into the remote system.  Never returns if the login fails. */
  	ssh_login(ssh, &sensitive_data, host, (struct sockaddr *)&hostaddr,
  	    options.port, pw, timeout_ms);
  
  	if (ssh_packet_connection_is_on_socket(ssh)) {
  		verbose("Authenticated to %s ([%s]:%d).", host,
  		    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
  	} else {
  		verbose("Authenticated to %s (via proxy).", host);
  	}
  
  	/* We no longer need the private host keys.  Clear them now. */
  	if (sensitive_data.nkeys != 0) {
  		for (i = 0; i < sensitive_data.nkeys; i++) {
  			if (sensitive_data.keys[i] != NULL) {
  				/* Destroys contents safely */
  				debug3("clear hostkey %d", i);
  				sshkey_free(sensitive_data.keys[i]);
  				sensitive_data.keys[i] = NULL;
  			}
  		}
  		free(sensitive_data.keys);
  	}
  	for (i = 0; i < options.num_identity_files; i++) {
  		free(options.identity_files[i]);
  		options.identity_files[i] = NULL;
  		if (options.identity_keys[i]) {
  			sshkey_free(options.identity_keys[i]);
  			options.identity_keys[i] = NULL;
  		}
  	}
  	for (i = 0; i < options.num_certificate_files; i++) {
  		free(options.certificate_files[i]);
  		options.certificate_files[i] = NULL;
  	}
  
   skip_connect:
  	exit_status = ssh_session2(ssh, pw);
  	ssh_packet_close(ssh);
  
  	if (options.control_path != NULL && muxserver_sock != -1)
  		unlink(options.control_path);
  
  	/* Kill ProxyCommand if it is running. */
  	ssh_kill_proxy_command();
  
  	return exit_status;
  }
  
  static void
  control_persist_detach(void)
  {
  	pid_t pid;
  	int devnull, keep_stderr;
  
  	debug("%s: backgrounding master process", __func__);
  
  	/*
  	 * master (current process) into the background, and make the
  	 * foreground process a client of the backgrounded master.
  	 */
  	switch ((pid = fork())) {
  	case -1:
  		fatal("%s: fork: %s", __func__, strerror(errno));
  	case 0:
  		/* Child: master process continues mainloop */
  		break;
  	default:
  		/* Parent: set up mux client to connect to backgrounded master */
  		debug2("%s: background process is %ld", __func__, (long)pid);
  		stdin_null_flag = ostdin_null_flag;
  		options.request_tty = orequest_tty;
  		tty_flag = otty_flag;
  		close(muxserver_sock);
  		muxserver_sock = -1;
  		options.control_master = SSHCTL_MASTER_NO;
  		muxclient(options.control_path);
  		/* muxclient() doesn't return on success. */
  		fatal("Failed to connect to new control master");
  	}
  	if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
  		error("%s: open(\"/dev/null\"): %s", __func__,
  		    strerror(errno));
  	} else {
  		keep_stderr = log_is_on_stderr() && debug_flag;
  		if (dup2(devnull, STDIN_FILENO) == -1 ||
  		    dup2(devnull, STDOUT_FILENO) == -1 ||
  		    (!keep_stderr && dup2(devnull, STDERR_FILENO) == -1))
  			error("%s: dup2: %s", __func__, strerror(errno));
  		if (devnull > STDERR_FILENO)
  			close(devnull);
  	}
  	daemon(1, 1);
  	setproctitle("%s [mux]", options.control_path);
  }
  
  /* Do fork() after authentication. Used by "ssh -f" */
  static void
  fork_postauth(void)
  {
  	if (need_controlpersist_detach)
  		control_persist_detach();
  	debug("forking to background");
  	fork_after_authentication_flag = 0;
  	if (daemon(1, 1) == -1)
  		fatal("daemon() failed: %.200s", strerror(errno));
  }
  
  static void
  forwarding_success(void)
  {
  	if (forward_confirms_pending == -1)
  		return;
  	if (--forward_confirms_pending == 0) {
  		debug("%s: all expected forwarding replies received", __func__);
  		if (fork_after_authentication_flag)
  			fork_postauth();
  	} else {
  		debug2("%s: %d expected forwarding replies remaining",
  		    __func__, forward_confirms_pending);
  	}
  }
  
  /* Callback for remote forward global requests */
  static void
  ssh_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt)
  {
  	struct Forward *rfwd = (struct Forward *)ctxt;
  	u_int port;
  	int r;
  
  	/* XXX verbose() on failure? */
  	debug("remote forward %s for: listen %s%s%d, connect %s:%d",
  	    type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
  	    rfwd->listen_path ? rfwd->listen_path :
  	    rfwd->listen_host ? rfwd->listen_host : "",
  	    (rfwd->listen_path || rfwd->listen_host) ? ":" : "",
  	    rfwd->listen_port, rfwd->connect_path ? rfwd->connect_path :
  	    rfwd->connect_host, rfwd->connect_port);
  	if (rfwd->listen_path == NULL && rfwd->listen_port == 0) {
  		if (type == SSH2_MSG_REQUEST_SUCCESS) {
  			if ((r = sshpkt_get_u32(ssh, &port)) != 0)
  				fatal("%s: %s", __func__, ssh_err(r));
  			if (port > 65535) {
  				error("Invalid allocated port %u for remote "
  				    "forward to %s:%d", port,
  				    rfwd->connect_host, rfwd->connect_port);
  				/* Ensure failure processing runs below */
  				type = SSH2_MSG_REQUEST_FAILURE;
  				channel_update_permission(ssh,
  				    rfwd->handle, -1);
  			} else {
  				rfwd->allocated_port = (int)port;
  				logit("Allocated port %u for remote "
  				    "forward to %s:%d",
  				    rfwd->allocated_port, rfwd->connect_host,
  				    rfwd->connect_port);
  				channel_update_permission(ssh,
  				    rfwd->handle, rfwd->allocated_port);
  			}
  		} else {
  			channel_update_permission(ssh, rfwd->handle, -1);
  		}
  	}
  
  	if (type == SSH2_MSG_REQUEST_FAILURE) {
  		if (options.exit_on_forward_failure) {
  			if (rfwd->listen_path != NULL)
  				fatal("Error: remote port forwarding failed "
  				    "for listen path %s", rfwd->listen_path);
  			else
  				fatal("Error: remote port forwarding failed "
  				    "for listen port %d", rfwd->listen_port);
  		} else {
  			if (rfwd->listen_path != NULL)
  				logit("Warning: remote port forwarding failed "
  				    "for listen path %s", rfwd->listen_path);
  			else
  				logit("Warning: remote port forwarding failed "
  				    "for listen port %d", rfwd->listen_port);
  		}
  	}
  	forwarding_success();
  }
  
  static void
  client_cleanup_stdio_fwd(struct ssh *ssh, int id, void *arg)
  {
  	debug("stdio forwarding: done");
  	cleanup_exit(0);
  }
  
  static void
  ssh_stdio_confirm(struct ssh *ssh, int id, int success, void *arg)
  {
  	if (!success)
  		fatal("stdio forwarding failed");
  }
  
  static void
  ssh_tun_confirm(struct ssh *ssh, int id, int success, void *arg)
  {
  	if (!success) {
  		error("Tunnel forwarding failed");
  		if (options.exit_on_forward_failure)
  			cleanup_exit(255);
  	}
  
  	debug("%s: tunnel forward established, id=%d", __func__, id);
  	forwarding_success();
  }
  
  static void
  ssh_init_stdio_forwarding(struct ssh *ssh)
  {
  	Channel *c;
  	int in, out;
  
  	if (options.stdio_forward_host == NULL)
  		return;
  
  	debug3("%s: %s:%d", __func__, options.stdio_forward_host,
  	    options.stdio_forward_port);
  
  	if ((in = dup(STDIN_FILENO)) == -1 ||
  	    (out = dup(STDOUT_FILENO)) == -1)
  		fatal("channel_connect_stdio_fwd: dup() in/out failed");
  	if ((c = channel_connect_stdio_fwd(ssh, options.stdio_forward_host,
  	    options.stdio_forward_port, in, out)) == NULL)
  		fatal("%s: channel_connect_stdio_fwd failed", __func__);
  	channel_register_cleanup(ssh, c->self, client_cleanup_stdio_fwd, 0);
  	channel_register_open_confirm(ssh, c->self, ssh_stdio_confirm, NULL);
  }
  
  static void
  ssh_init_forwarding(struct ssh *ssh, char **ifname)
  {
  	int success = 0;
  	int i;
  
  	if (options.exit_on_forward_failure)
  		forward_confirms_pending = 0; /* track pending requests */
  	/* Initiate local TCP/IP port forwardings. */
  	for (i = 0; i < options.num_local_forwards; i++) {
  		debug("Local connections to %.200s:%d forwarded to remote "
  		    "address %.200s:%d",
  		    (options.local_forwards[i].listen_path != NULL) ?
  		    options.local_forwards[i].listen_path :
  		    (options.local_forwards[i].listen_host == NULL) ?
  		    (options.fwd_opts.gateway_ports ? "*" : "LOCALHOST") :
  		    options.local_forwards[i].listen_host,
  		    options.local_forwards[i].listen_port,
  		    (options.local_forwards[i].connect_path != NULL) ?
  		    options.local_forwards[i].connect_path :
  		    options.local_forwards[i].connect_host,
  		    options.local_forwards[i].connect_port);
  		success += channel_setup_local_fwd_listener(ssh,
  		    &options.local_forwards[i], &options.fwd_opts);
  	}
  	if (i > 0 && success != i && options.exit_on_forward_failure)
  		fatal("Could not request local forwarding.");
  	if (i > 0 && success == 0)
  		error("Could not request local forwarding.");
  
  	/* Initiate remote TCP/IP port forwardings. */
  	for (i = 0; i < options.num_remote_forwards; i++) {
  		debug("Remote connections from %.200s:%d forwarded to "
  		    "local address %.200s:%d",
  		    (options.remote_forwards[i].listen_path != NULL) ?
  		    options.remote_forwards[i].listen_path :
  		    (options.remote_forwards[i].listen_host == NULL) ?
  		    "LOCALHOST" : options.remote_forwards[i].listen_host,
  		    options.remote_forwards[i].listen_port,
  		    (options.remote_forwards[i].connect_path != NULL) ?
  		    options.remote_forwards[i].connect_path :
  		    options.remote_forwards[i].connect_host,
  		    options.remote_forwards[i].connect_port);
  		if ((options.remote_forwards[i].handle =
  		    channel_request_remote_forwarding(ssh,
  		    &options.remote_forwards[i])) >= 0) {
  			client_register_global_confirm(
  			    ssh_confirm_remote_forward,
  			    &options.remote_forwards[i]);
  			forward_confirms_pending++;
  		} else if (options.exit_on_forward_failure)
  			fatal("Could not request remote forwarding.");
  		else
  			logit("Warning: Could not request remote forwarding.");
  	}
  
  	/* Initiate tunnel forwarding. */
  	if (options.tun_open != SSH_TUNMODE_NO) {
  		if ((*ifname = client_request_tun_fwd(ssh,
  		    options.tun_open, options.tun_local,
  		    options.tun_remote, ssh_tun_confirm, NULL)) != NULL)
  			forward_confirms_pending++;
  		else if (options.exit_on_forward_failure)
  			fatal("Could not request tunnel forwarding.");
  		else
  			error("Could not request tunnel forwarding.");
  	}
  	if (forward_confirms_pending > 0) {
  		debug("%s: expecting replies for %d forwards", __func__,
  		    forward_confirms_pending);
  	}
  }
  
  static void
  check_agent_present(void)
  {
  	int r;
  
  	if (options.forward_agent) {
  		/* Clear agent forwarding if we don't have an agent. */
  		if ((r = ssh_get_authentication_socket(NULL)) != 0) {
  			options.forward_agent = 0;
  			if (r != SSH_ERR_AGENT_NOT_PRESENT)
  				debug("ssh_get_authentication_socket: %s",
  				    ssh_err(r));
  		}
  	}
  }
  
  static void
  ssh_session2_setup(struct ssh *ssh, int id, int success, void *arg)
  {
  	extern char **environ;
  	const char *display;
  	int r, interactive = tty_flag;
  	char *proto = NULL, *data = NULL;
  
  	if (!success)
  		return; /* No need for error message, channels code sens one */
  
  	display = getenv("DISPLAY");
  	if (display == NULL && options.forward_x11)
  		debug("X11 forwarding requested but DISPLAY not set");
  	if (options.forward_x11 && client_x11_get_proto(ssh, display,
  	    options.xauth_location, options.forward_x11_trusted,
  	    options.forward_x11_timeout, &proto, &data) == 0) {
  		/* Request forwarding with authentication spoofing. */
  		debug("Requesting X11 forwarding with authentication "
  		    "spoofing.");
  		x11_request_forwarding_with_spoofing(ssh, id, display, proto,
  		    data, 1);
  		client_expect_confirm(ssh, id, "X11 forwarding", CONFIRM_WARN);
  		/* XXX exit_on_forward_failure */
  		interactive = 1;
  	}
  
  	check_agent_present();
  	if (options.forward_agent) {
  		debug("Requesting authentication agent forwarding.");
  		channel_request_start(ssh, id, "auth-agent-req@openssh.com", 0);
  		if ((r = sshpkt_send(ssh)) != 0)
  			fatal("%s: %s", __func__, ssh_err(r));
  	}
  
  	/* Tell the packet module whether this is an interactive session. */
  	ssh_packet_set_interactive(ssh, interactive,
  	    options.ip_qos_interactive, options.ip_qos_bulk);
  
  	client_session2_setup(ssh, id, tty_flag, subsystem_flag, getenv("TERM"),
  	    NULL, fileno(stdin), command, environ);
  }
  
  /* open new channel for a session */
  static int
  ssh_session2_open(struct ssh *ssh)
  {
  	Channel *c;
  	int window, packetmax, in, out, err;
  
  	if (stdin_null_flag) {
  		in = open(_PATH_DEVNULL, O_RDONLY);
  	} else {
  		in = dup(STDIN_FILENO);
  	}
  	out = dup(STDOUT_FILENO);
  	err = dup(STDERR_FILENO);
  
  	if (in == -1 || out == -1 || err == -1)
  		fatal("dup() in/out/err failed");
  
  	/* enable nonblocking unless tty */
  	if (!isatty(in))
  		set_nonblock(in);
  	if (!isatty(out))
  		set_nonblock(out);
  	if (!isatty(err))
  		set_nonblock(err);
  
  	window = CHAN_SES_WINDOW_DEFAULT;
  	packetmax = CHAN_SES_PACKET_DEFAULT;
  	if (tty_flag) {
  		window >>= 1;
  		packetmax >>= 1;
  	}
  	c = channel_new(ssh,
  	    "session", SSH_CHANNEL_OPENING, in, out, err,
  	    window, packetmax, CHAN_EXTENDED_WRITE,
  	    "client-session", /*nonblock*/0);
  
  	debug3("%s: channel_new: %d", __func__, c->self);
  
  	channel_send_open(ssh, c->self);
  	if (!no_shell_flag)
  		channel_register_open_confirm(ssh, c->self,
  		    ssh_session2_setup, NULL);
  
  	return c->self;
  }
  
  static int
  ssh_session2(struct ssh *ssh, struct passwd *pw)
  {
  	int r, devnull, id = -1;
  	char *cp, *tun_fwd_ifname = NULL;
  
  	/* XXX should be pre-session */
  	if (!options.control_persist)
  		ssh_init_stdio_forwarding(ssh);
  
  	ssh_init_forwarding(ssh, &tun_fwd_ifname);
  
  	if (options.local_command != NULL) {
  		debug3("expanding LocalCommand: %s", options.local_command);
  		cp = options.local_command;
  		options.local_command = percent_expand(cp,
  		    DEFAULT_CLIENT_PERCENT_EXPAND_ARGS,
  		    "d", pw->pw_dir,
  		    "h", host,
  		    "r", options.user,
  		    "u", pw->pw_name,
  		    "T", tun_fwd_ifname == NULL ? "NONE" : tun_fwd_ifname,
  		    (char *)NULL);
  		debug3("expanded LocalCommand: %s", options.local_command);
  		free(cp);
  	}
  
  	/* Start listening for multiplex clients */
  	if (!ssh_packet_get_mux(ssh))
  		muxserver_listen(ssh);
  
  	/*
  	 * If we are in control persist mode and have a working mux listen
  	 * socket, then prepare to background ourselves and have a foreground
  	 * client attach as a control client.
  	 * NB. we must save copies of the flags that we override for
  	 * the backgrounding, since we defer attachment of the client until
  	 * after the connection is fully established (in particular,
  	 * async rfwd replies have been received for ExitOnForwardFailure).
  	 */
  	if (options.control_persist && muxserver_sock != -1) {
  		ostdin_null_flag = stdin_null_flag;
  		ono_shell_flag = no_shell_flag;
  		orequest_tty = options.request_tty;
  		otty_flag = tty_flag;
  		stdin_null_flag = 1;
  		no_shell_flag = 1;
  		tty_flag = 0;
  		if (!fork_after_authentication_flag)
  			need_controlpersist_detach = 1;
  		fork_after_authentication_flag = 1;
  	}
  	/*
  	 * ControlPersist mux listen socket setup failed, attempt the
  	 * stdio forward setup that we skipped earlier.
  	 */
  	if (options.control_persist && muxserver_sock == -1)
  		ssh_init_stdio_forwarding(ssh);
  
  	if (!no_shell_flag)
  		id = ssh_session2_open(ssh);
  	else {
  		ssh_packet_set_interactive(ssh,
  		    options.control_master == SSHCTL_MASTER_NO,
  		    options.ip_qos_interactive, options.ip_qos_bulk);
  	}
  
  	/* If we don't expect to open a new session, then disallow it */
  	if (options.control_master == SSHCTL_MASTER_NO &&
  	    (datafellows & SSH_NEW_OPENSSH)) {
  		debug("Requesting no-more-sessions@openssh.com");
  		if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
  		    (r = sshpkt_put_cstring(ssh,
  		    "no-more-sessions@openssh.com")) != 0 ||
  		    (r = sshpkt_put_u8(ssh, 0)) != 0 ||
  		    (r = sshpkt_send(ssh)) != 0)
  			fatal("%s: %s", __func__, ssh_err(r));
  	}
  
  	/* Execute a local command */
  	if (options.local_command != NULL &&
  	    options.permit_local_command)
  		ssh_local_cmd(options.local_command);
  
  	/*
  	 * stdout is now owned by the session channel; clobber it here
  	 * so future channel closes are propagated to the local fd.
  	 * NB. this can only happen after LocalCommand has completed,
  	 * as it may want to write to stdout.
  	 */
  	if (!need_controlpersist_detach) {
  		if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1)
  			error("%s: open %s: %s", __func__,
  			    _PATH_DEVNULL, strerror(errno));
  		if (dup2(devnull, STDOUT_FILENO) == -1)
  			fatal("%s: dup2() stdout failed", __func__);
  		if (devnull > STDERR_FILENO)
  			close(devnull);
  	}
  
  	/*
  	 * If requested and we are not interested in replies to remote
  	 * forwarding requests, then let ssh continue in the background.
  	 */
  	if (fork_after_authentication_flag) {
  		if (options.exit_on_forward_failure &&
  		    options.num_remote_forwards > 0) {
  			debug("deferring postauth fork until remote forward "
  			    "confirmation received");
  		} else
  			fork_postauth();
  	}
  
  	return client_loop(ssh, tty_flag, tty_flag ?
  	    options.escape_char : SSH_ESCAPECHAR_NONE, id);
  }
  
  /* Loads all IdentityFile and CertificateFile keys */
  static void
  load_public_identity_files(struct passwd *pw)
  {
  	char *filename, *cp;
  	struct sshkey *public;
  	int i;
  	u_int n_ids, n_certs;
  	char *identity_files[SSH_MAX_IDENTITY_FILES];
  	struct sshkey *identity_keys[SSH_MAX_IDENTITY_FILES];
  	int identity_file_userprovided[SSH_MAX_IDENTITY_FILES];
  	char *certificate_files[SSH_MAX_CERTIFICATE_FILES];
  	struct sshkey *certificates[SSH_MAX_CERTIFICATE_FILES];
  	int certificate_file_userprovided[SSH_MAX_CERTIFICATE_FILES];
  #ifdef ENABLE_PKCS11
  	struct sshkey **keys = NULL;
  	char **comments = NULL;
  	int nkeys;
  #endif /* PKCS11 */
  
  	n_ids = n_certs = 0;
  	memset(identity_files, 0, sizeof(identity_files));
  	memset(identity_keys, 0, sizeof(identity_keys));
  	memset(identity_file_userprovided, 0,
  	    sizeof(identity_file_userprovided));
  	memset(certificate_files, 0, sizeof(certificate_files));
  	memset(certificates, 0, sizeof(certificates));
  	memset(certificate_file_userprovided, 0,
  	    sizeof(certificate_file_userprovided));
  
  #ifdef ENABLE_PKCS11
  	if (options.pkcs11_provider != NULL &&
  	    options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
  	    (pkcs11_init(!options.batch_mode) == 0) &&
  	    (nkeys = pkcs11_add_provider(options.pkcs11_provider, NULL,
  	    &keys, &comments)) > 0) {
  		for (i = 0; i < nkeys; i++) {
  			if (n_ids >= SSH_MAX_IDENTITY_FILES) {
  				sshkey_free(keys[i]);
  				free(comments[i]);
  				continue;
  			}
  			identity_keys[n_ids] = keys[i];
  			identity_files[n_ids] = comments[i]; /* transferred */
  			n_ids++;
  		}
  		free(keys);
  		free(comments);
  	}
  #endif /* ENABLE_PKCS11 */
  	for (i = 0; i < options.num_identity_files; i++) {
  		if (n_ids >= SSH_MAX_IDENTITY_FILES ||
  		    strcasecmp(options.identity_files[i], "none") == 0) {
  			free(options.identity_files[i]);
  			options.identity_files[i] = NULL;
  			continue;
  		}
  		cp = tilde_expand_filename(options.identity_files[i], getuid());
  		filename = default_client_percent_dollar_expand(cp,
  		    pw->pw_dir, host, options.user, pw->pw_name);
  		free(cp);
  		check_load(sshkey_load_public(filename, &public, NULL),
  		    filename, "pubkey");
  		debug("identity file %s type %d", filename,
  		    public ? public->type : -1);
  		free(options.identity_files[i]);
  		identity_files[n_ids] = filename;
  		identity_keys[n_ids] = public;
  		identity_file_userprovided[n_ids] =
  		    options.identity_file_userprovided[i];
  		if (++n_ids >= SSH_MAX_IDENTITY_FILES)
  			continue;
  
  		/*
  		 * If no certificates have been explicitly listed then try
  		 * to add the default certificate variant too.
  		 */
  		if (options.num_certificate_files != 0)
  			continue;
  		xasprintf(&cp, "%s-cert", filename);
  		check_load(sshkey_load_public(cp, &public, NULL),
  		    filename, "pubkey");
  		debug("identity file %s type %d", cp,
  		    public ? public->type : -1);
  		if (public == NULL) {
  			free(cp);
  			continue;
  		}
  		if (!sshkey_is_cert(public)) {
  			debug("%s: key %s type %s is not a certificate",
  			    __func__, cp, sshkey_type(public));
  			sshkey_free(public);
  			free(cp);
  			continue;
  		}
  		/* NB. leave filename pointing to private key */
  		identity_files[n_ids] = xstrdup(filename);
  		identity_keys[n_ids] = public;
  		identity_file_userprovided[n_ids] =
  		    options.identity_file_userprovided[i];
  		n_ids++;
  	}
  
  	if (options.num_certificate_files > SSH_MAX_CERTIFICATE_FILES)
  		fatal("%s: too many certificates", __func__);
  	for (i = 0; i < options.num_certificate_files; i++) {
  		cp = tilde_expand_filename(options.certificate_files[i],
  		    getuid());
  		filename = default_client_percent_dollar_expand(cp,
  		    pw->pw_dir, host, options.user, pw->pw_name);
  		free(cp);
  
  		check_load(sshkey_load_public(filename, &public, NULL),
  		    filename, "certificate");
  		debug("certificate file %s type %d", filename,
  		    public ? public->type : -1);
  		free(options.certificate_files[i]);
  		options.certificate_files[i] = NULL;
  		if (public == NULL) {
  			free(filename);
  			continue;
  		}
  		if (!sshkey_is_cert(public)) {
  			debug("%s: key %s type %s is not a certificate",
  			    __func__, filename, sshkey_type(public));
  			sshkey_free(public);
  			free(filename);
  			continue;
  		}
  		certificate_files[n_certs] = filename;
  		certificates[n_certs] = public;
  		certificate_file_userprovided[n_certs] =
  		    options.certificate_file_userprovided[i];
  		++n_certs;
  	}
  
  	options.num_identity_files = n_ids;
  	memcpy(options.identity_files, identity_files, sizeof(identity_files));
  	memcpy(options.identity_keys, identity_keys, sizeof(identity_keys));
  	memcpy(options.identity_file_userprovided,
  	    identity_file_userprovided, sizeof(identity_file_userprovided));
  
  	options.num_certificate_files = n_certs;
  	memcpy(options.certificate_files,
  	    certificate_files, sizeof(certificate_files));
  	memcpy(options.certificates, certificates, sizeof(certificates));
  	memcpy(options.certificate_file_userprovided,
  	    certificate_file_userprovided,
  	    sizeof(certificate_file_userprovided));
  }
  
  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;
  }