text: /* $OpenBSD: sshconnect.c,v 1.212 2008/10/14 18:11:33 stevesk Exp $ */
  /*
   * Author: Tatu Ylonen <ylo@cs.hut.fi>
   * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   *                    All rights reserved
   * Code to connect to a remote host, and to perform the client side of the
   * login (authentication) dialog.
   *
   * 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".
   */
  
  #include "includes.h"
  
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <sys/stat.h>
  #include <sys/socket.h>
  #ifdef HAVE_SYS_TIME_H
  # include <sys/time.h>
  #endif
  
  #include <netinet/in.h>
  #include <arpa/inet.h>
  
  #include <ctype.h>
  #include <errno.h>
  #include <netdb.h>
  #ifdef HAVE_PATHS_H
  #include <paths.h>
  #endif
  #include <pwd.h>
  #include <stdarg.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <unistd.h>
  
  #include "xmalloc.h"
  #include "key.h"
  #include "hostfile.h"
  #include "ssh.h"
  #include "rsa.h"
  #include "buffer.h"
  #include "packet.h"
  #include "uidswap.h"
  #include "compat.h"
  #include "key.h"
  #include "sshconnect.h"
  #include "hostfile.h"
  #include "log.h"
  #include "readconf.h"
  #include "atomicio.h"
  #include "misc.h"
  #include "dns.h"
  #include "version.h"
  #include "obfuscate.h"
  
  char *client_version_string = NULL;
  char *server_version_string = NULL;
  
  static int matching_host_key_dns = 0;
  
  /* import */
  extern Options options;
  extern char *__progname;
  extern uid_t original_real_uid;
  extern uid_t original_effective_uid;
  extern pid_t proxy_command_pid;
  
  static int show_other_keys(const char *, Key *);
  static void warn_changed_key(Key *);
  
  /*
   * Connect to the given ssh server using a proxy command.
   */
  static int
  ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
  {
  	char *command_string, *tmp;
  	int pin[2], pout[2];
  	pid_t pid;
  	char *shell, strport[NI_MAXSERV];
  
  	if ((shell = getenv("SHELL")) == NULL)
  		shell = _PATH_BSHELL;
  
  	/* Convert the port number into a string. */
  	snprintf(strport, sizeof strport, "%hu", port);
  
  	/*
  	 * Build the final command string in the buffer by making the
  	 * appropriate substitutions to the given proxy command.
  	 *
  	 * Use "exec" to avoid "sh -c" processes on some platforms
  	 * (e.g. Solaris)
  	 */
  	xasprintf(&tmp, "exec %s", proxy_command);
  	command_string = percent_expand(tmp, "h", host,
  	    "p", strport, (char *)NULL);
  	xfree(tmp);
  
  	/* Create pipes for communicating with the proxy. */
  	if (pipe(pin) < 0 || pipe(pout) < 0)
  		fatal("Could not create pipes to communicate with the proxy: %.100s",
  		    strerror(errno));
  
  	debug("Executing proxy command: %.500s", command_string);
  
  	/* Fork and execute the proxy command. */
  	if ((pid = fork()) == 0) {
  		char *argv[10];
  
  		/* Child.  Permanently give up superuser privileges. */
  		permanently_drop_suid(original_real_uid);
  
  		/* Redirect stdin and stdout. */
  		close(pin[1]);
  		if (pin[0] != 0) {
  			if (dup2(pin[0], 0) < 0)
  				perror("dup2 stdin");
  			close(pin[0]);
  		}
  		close(pout[0]);
  		if (dup2(pout[1], 1) < 0)
  			perror("dup2 stdout");
  		/* Cannot be 1 because pin allocated two descriptors. */
  		close(pout[1]);
  
  		/* Stderr is left as it is so that error messages get
  		   printed on the user's terminal. */
  		argv[0] = shell;
  		argv[1] = "-c";
  		argv[2] = command_string;
  		argv[3] = NULL;
  
  		/* Execute the proxy command.  Note that we gave up any
  		   extra privileges above. */
  		execv(argv[0], argv);
  		perror(argv[0]);
  		exit(1);
  	}
  	/* Parent. */
  	if (pid < 0)
  		fatal("fork failed: %.100s", strerror(errno));
  	else
  		proxy_command_pid = pid; /* save pid to clean up later */
  
  	/* Close child side of the descriptors. */
  	close(pin[0]);
  	close(pout[1]);
  
  	/* Free the command name. */
  	xfree(command_string);
  
  	/* Set the connection file descriptors. */
  	packet_set_connection(pout[0], pin[1]);
  	packet_set_timeout(options.server_alive_interval,
  	    options.server_alive_count_max);
  
  	if(options.obfuscate_handshake) {
     		if(options.obfuscate_keyword)
        			obfuscate_set_keyword(options.obfuscate_keyword);
  		packet_enable_obfuscation();
  	}
  
  	/* Indicate OK return */
  	return 0;
  }
  
  /*
   * Creates a (possibly privileged) socket for use as the ssh connection.
   */
  static int
  ssh_create_socket(int privileged, struct addrinfo *ai)
  {
  	int sock, gaierr;
  	struct addrinfo hints, *res;
  
  	/*
  	 * If we are running as root and want to connect to a privileged
  	 * port, bind our own socket to a privileged port.
  	 */
  	if (privileged) {
  		int p = IPPORT_RESERVED - 1;
  		PRIV_START;
  		sock = rresvport_af(&p, ai->ai_family);
  		PRIV_END;
  		if (sock < 0)
  			error("rresvport: af=%d %.100s", ai->ai_family,
  			    strerror(errno));
  		else
  			debug("Allocated local port %d.", p);
  		return sock;
  	}
  	sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
  	if (sock < 0)
  		error("socket: %.100s", strerror(errno));
  
  	/* Bind the socket to an alternative local IP address */
  	if (options.bind_address == NULL)
  		return sock;
  
  	memset(&hints, 0, sizeof(hints));
  	hints.ai_family = ai->ai_family;
  	hints.ai_socktype = ai->ai_socktype;
  	hints.ai_protocol = ai->ai_protocol;
  	hints.ai_flags = AI_PASSIVE;
  	gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
  	if (gaierr) {
  		error("getaddrinfo: %s: %s", options.bind_address,
  		    ssh_gai_strerror(gaierr));
  		close(sock);
  		return -1;
  	}
  	if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
  		error("bind: %s: %s", options.bind_address, strerror(errno));
  		close(sock);
  		freeaddrinfo(res);
  		return -1;
  	}
  	freeaddrinfo(res);
  	return sock;
  }
  
  static int
  timeout_connect(int sockfd, const struct sockaddr *serv_addr,
      socklen_t addrlen, int *timeoutp)
  {
  	fd_set *fdset;
  	struct timeval tv, t_start;
  	socklen_t optlen;
  	int optval, rc, result = -1;
  
  	gettimeofday(&t_start, NULL);
  
  	if (*timeoutp <= 0) {
  		result = connect(sockfd, serv_addr, addrlen);
  		goto done;
  	}
  
  	set_nonblock(sockfd);
  	rc = connect(sockfd, serv_addr, addrlen);
  	if (rc == 0) {
  		unset_nonblock(sockfd);
  		result = 0;
  		goto done;
  	}
  	if (errno != EINPROGRESS) {
  		result = -1;
  		goto done;
  	}
  
  	fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
  	    sizeof(fd_mask));
  	FD_SET(sockfd, fdset);
  	ms_to_timeval(&tv, *timeoutp);
  
  	for (;;) {
  		rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
  		if (rc != -1 || errno != EINTR)
  			break;
  	}
  
  	switch (rc) {
  	case 0:
  		/* Timed out */
  		errno = ETIMEDOUT;
  		break;
  	case -1:
  		/* Select error */
  		debug("select: %s", strerror(errno));
  		break;
  	case 1:
  		/* Completed or failed */
  		optval = 0;
  		optlen = sizeof(optval);
  		if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
  		    &optlen) == -1) {
  			debug("getsockopt: %s", strerror(errno));
  			break;
  		}
  		if (optval != 0) {
  			errno = optval;
  			break;
  		}
  		result = 0;
  		unset_nonblock(sockfd);
  		break;
  	default:
  		/* Should not occur */
  		fatal("Bogus return (%d) from select()", rc);
  	}
  
  	xfree(fdset);
  
   done:
   	if (result == 0 && *timeoutp > 0) {
  		ms_subtract_diff(&t_start, timeoutp);
  		if (*timeoutp <= 0) {
  			errno = ETIMEDOUT;
  			result = -1;
  		}
  	}
  
  	return (result);
  }
  
  /*
   * Opens a TCP/IP connection to the remote server on the given host.
   * The address of the remote host will be returned in hostaddr.
   * If port is 0, the default port will be used.  If needpriv is true,
   * a privileged port will be allocated to make the connection.
   * This requires super-user privileges if needpriv is true.
   * Connection_attempts specifies the maximum number of tries (one per
   * second).  If proxy_command is non-NULL, it specifies the command (with %h
   * and %p substituted for host and port, respectively) to use to contact
   * the daemon.
   */
  int
  ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
      u_short port, int family, int connection_attempts, int *timeout_ms,
      int want_keepalive, int needpriv, const char *proxy_command)
  {
  	int gaierr;
  	int on = 1;
  	int sock = -1, attempt;
  	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
  	struct addrinfo hints, *ai, *aitop;
  
  	debug2("ssh_connect: needpriv %d", needpriv);
  
  	/* If a proxy command is given, connect using it. */
  	if (proxy_command != NULL)
  		return ssh_proxy_connect(host, port, proxy_command);
  
  	/* No proxy command. */
  
  	memset(&hints, 0, sizeof(hints));
  	hints.ai_family = family;
  	hints.ai_socktype = SOCK_STREAM;
  	snprintf(strport, sizeof strport, "%u", port);
  	if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
  		fatal("%s: Could not resolve hostname %.100s: %s", __progname,
  		    host, ssh_gai_strerror(gaierr));
  
  	for (attempt = 0; attempt < connection_attempts; attempt++) {
  		if (attempt > 0) {
  			/* Sleep a moment before retrying. */
  			sleep(1);
  			debug("Trying again...");
  		}
  		/*
  		 * Loop through addresses for this host, and try each one in
  		 * sequence until the connection succeeds.
  		 */
  		for (ai = aitop; ai; ai = ai->ai_next) {
  			if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
  				continue;
  			if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
  			    ntop, sizeof(ntop), strport, sizeof(strport),
  			    NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
  				error("ssh_connect: getnameinfo failed");
  				continue;
  			}
  			debug("Connecting to %.200s [%.100s] port %s.",
  				host, ntop, strport);
  
  			/* Create a socket for connecting. */
  			sock = ssh_create_socket(needpriv, ai);
  			if (sock < 0)
  				/* Any error is already output */
  				continue;
  
  			if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
  			    timeout_ms) >= 0) {
  				/* Successful connection. */
  				memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
  				break;
  			} else {
  				debug("connect to address %s port %s: %s",
  				    ntop, strport, strerror(errno));
  				close(sock);
  				sock = -1;
  			}
  		}
  		if (sock != -1)
  			break;	/* Successful connection. */
  	}
  
  	freeaddrinfo(aitop);
  
  	/* Return failure if we didn't get a successful connection. */
  	if (sock == -1) {
  		error("ssh: connect to host %s port %s: %s",
  		    host, strport, strerror(errno));
  		return (-1);
  	}
  
  	debug("Connection established.");
  
  	/* Set SO_KEEPALIVE if requested. */
  	if (want_keepalive &&
  	    setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
  	    sizeof(on)) < 0)
  		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
  
  	/* Set the connection. */
  	packet_set_connection(sock, sock);
  	packet_set_timeout(options.server_alive_interval,
  	    options.server_alive_count_max);
  	if(options.obfuscate_handshake) {
  		if(options.obfuscate_keyword)
  			obfuscate_set_keyword(options.obfuscate_keyword);
  		packet_enable_obfuscation();
  	}
  
  	return 0;
  }
  
  /*
   * Waits for the server identification string, and sends our own
   * identification string.
   */
  static void
  ssh_exchange_identification(int timeout_ms)
  {
  	char buf[256], remote_version[256];	/* must be same size! */
  	int remote_major, remote_minor, mismatch;
  	int connection_in = packet_get_connection_in();
  	int connection_out = packet_get_connection_out();
  	int minor1 = PROTOCOL_MINOR_1;
  	u_int i, n;
  	size_t len;
  	u_int sendlen;
  	int fdsetsz, remaining, rc;
  	struct timeval t_start, t_remaining;
  	fd_set *fdset;
  
  	fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
  	fdset = xcalloc(1, fdsetsz);
  
  	/* Read other side's version identification. */
  	remaining = timeout_ms;
  	for (n = 0;;) {
  		for (i = 0; i < sizeof(buf) - 1; i++) {
  			if (timeout_ms > 0) {
  				gettimeofday(&t_start, NULL);
  				ms_to_timeval(&t_remaining, remaining);
  				FD_SET(connection_in, fdset);
  				rc = select(connection_in + 1, fdset, NULL,
  				    fdset, &t_remaining);
  				ms_subtract_diff(&t_start, &remaining);
  				if (rc == 0 || remaining <= 0)
  					fatal("Connection timed out during "
  					    "banner exchange");
  				if (rc == -1) {
  					if (errno == EINTR)
  						continue;
  					fatal("ssh_exchange_identification: "
  					    "select: %s", strerror(errno));
  				}
  			}
  
  			len = atomicio(read, connection_in, &buf[i], 1);
  
  			if (len != 1 && errno == EPIPE)
  				fatal("ssh_exchange_identification: "
  				    "Connection closed by remote host");
  			else if (len != 1)
  				fatal("ssh_exchange_identification: "
  				    "read: %.100s", strerror(errno));
  			if(options.obfuscate_handshake)
  				obfuscate_input(&buf[i], 1);
  			if (buf[i] == '\r') {
  				buf[i] = '\n';
  				buf[i + 1] = 0;
  				continue;		/**XXX wait for \n */
  			}
  			if (buf[i] == '\n') {
  				buf[i + 1] = 0;
  				break;
  			}
  			if (++n > 65536)
  				fatal("ssh_exchange_identification: "
  				    "No banner received");
  		}
  		buf[sizeof(buf) - 1] = 0;
  		if (strncmp(buf, "SSH-", 4) == 0)
  			break;
  		debug("ssh_exchange_identification: %s", buf);
  	}
  	server_version_string = xstrdup(buf);
  	xfree(fdset);
  
  	/*
  	 * Check that the versions match.  In future this might accept
  	 * several versions and set appropriate flags to handle them.
  	 */
  	if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
  	    &remote_major, &remote_minor, remote_version) != 3)
  		fatal("Bad remote protocol version identification: '%.100s'", buf);
  	debug("Remote protocol version %d.%d, remote software version %.100s",
  	    remote_major, remote_minor, remote_version);
  
  	compat_datafellows(remote_version);
  	mismatch = 0;
  
  	switch (remote_major) {
  	case 1:
  		if (remote_minor == 99 &&
  		    (options.protocol & SSH_PROTO_2) &&
  		    !(options.protocol & SSH_PROTO_1_PREFERRED)) {
  			enable_compat20();
  			break;
  		}
  		if (!(options.protocol & SSH_PROTO_1)) {
  			mismatch = 1;
  			break;
  		}
  		if (remote_minor < 3) {
  			fatal("Remote machine has too old SSH software version.");
  		} else if (remote_minor == 3 || remote_minor == 4) {
  			/* We speak 1.3, too. */
  			enable_compat13();
  			minor1 = 3;
  			if (options.forward_agent) {
  				logit("Agent forwarding disabled for protocol 1.3");
  				options.forward_agent = 0;
  			}
  		}
  		break;
  	case 2:
  		if (options.protocol & SSH_PROTO_2) {
  			enable_compat20();
  			break;
  		}
  		/* FALLTHROUGH */
  	default:
  		mismatch = 1;
  		break;
  	}
  	if (mismatch)
  		fatal("Protocol major versions differ: %d vs. %d",
  		    (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
  		    remote_major);
  	/* Send our own protocol version identification. */
  	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
  	    compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
  	    compat20 ? PROTOCOL_MINOR_2 : minor1,
  	    SSH_VERSION, compat20 ? "\r\n" : "\n");
  	client_version_string = xstrdup(buf);
  	sendlen = strlen(buf);
  	if(options.obfuscate_handshake)
  		obfuscate_output(buf, sendlen);
  	if (atomicio(vwrite, connection_out, buf, sendlen) != sendlen)
  		fatal("write: %.100s", strerror(errno));
  	chop(client_version_string);
  	chop(server_version_string);
  	debug("Local version string %.100s", client_version_string);
  }
  
  /* defaults to 'no' */
  static int
  confirm(const char *prompt)
  {
  	const char *msg, *again = "Please type 'yes' or 'no': ";
  	char *p;
  	int ret = -1;
  
  	if (options.batch_mode)
  		return 0;
  	for (msg = prompt;;msg = again) {
  		p = read_passphrase(msg, RP_ECHO);
  		if (p == NULL ||
  		    (p[0] == '\0') || (p[0] == '\n') ||
  		    strncasecmp(p, "no", 2) == 0)
  			ret = 0;
  		if (p && strncasecmp(p, "yes", 3) == 0)
  			ret = 1;
  		if (p)
  			xfree(p);
  		if (ret != -1)
  			return ret;
  	}
  }
  
  /*
   * check whether the supplied host key is valid, return -1 if the key
   * is not valid. the user_hostfile will not be updated if 'readonly' is true.
   */
  #define RDRW	0
  #define RDONLY	1
  #define ROQUIET	2
  static int
  check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
      Key *host_key, int readonly, const char *user_hostfile,
      const char *system_hostfile)
  {
  	Key *file_key;
  	const char *type = key_type(host_key);
  	char *ip = NULL, *host = NULL;
  	char hostline[1000], *hostp, *fp, *ra;
  	HostStatus host_status;
  	HostStatus ip_status;
  	int r, local = 0, host_ip_differ = 0;
  	int salen;
  	char ntop[NI_MAXHOST];
  	char msg[1024];
  	int len, host_line, ip_line, cancelled_forwarding = 0;
  	const char *host_file = NULL, *ip_file = NULL;
  
  	/*
  	 * Force accepting of the host key for loopback/localhost. The
  	 * problem is that if the home directory is NFS-mounted to multiple
  	 * machines, localhost will refer to a different machine in each of
  	 * them, and the user will get bogus HOST_CHANGED warnings.  This
  	 * essentially disables host authentication for localhost; however,
  	 * this is probably not a real problem.
  	 */
  	/**  hostaddr == 0! */
  	switch (hostaddr->sa_family) {
  	case AF_INET:
  		local = (ntohl(((struct sockaddr_in *)hostaddr)->
  		    sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
  		salen = sizeof(struct sockaddr_in);
  		break;
  	case AF_INET6:
  		local = IN6_IS_ADDR_LOOPBACK(
  		    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
  		salen = sizeof(struct sockaddr_in6);
  		break;
  	default:
  		local = 0;
  		salen = sizeof(struct sockaddr_storage);
  		break;
  	}
  	if (options.no_host_authentication_for_localhost == 1 && local &&
  	    options.host_key_alias == NULL) {
  		debug("Forcing accepting of host key for "
  		    "loopback/localhost.");
  		return 0;
  	}
  
  	/*
  	 * We don't have the remote ip-address for connections
  	 * using a proxy command
  	 */
  	if (options.proxy_command == NULL) {
  		if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
  		    NULL, 0, NI_NUMERICHOST) != 0)
  			fatal("check_host_key: getnameinfo failed");
  		ip = put_host_port(ntop, port);
  	} else {
  		ip = xstrdup("<no hostip for proxy command>");
  	}
  
  	/*
  	 * Turn off check_host_ip if the connection is to localhost, via proxy
  	 * command or if we don't have a hostname to compare with
  	 */
  	if (options.check_host_ip && (local ||
  	    strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
  		options.check_host_ip = 0;
  
  	/*
  	 * Allow the user to record the key under a different name or
  	 * differentiate a non-standard port.  This is useful for ssh
  	 * tunneling over forwarded connections or if you run multiple
  	 * sshd's on different ports on the same machine.
  	 */
  	if (options.host_key_alias != NULL) {
  		host = xstrdup(options.host_key_alias);
  		debug("using hostkeyalias: %s", host);
  	} else {
  		host = put_host_port(hostname, port);
  	}
  
  	/*
  	 * Store the host key from the known host file in here so that we can
  	 * compare it with the key for the IP address.
  	 */
  	file_key = key_new(host_key->type);
  
  	/*
  	 * Check if the host key is present in the user's list of known
  	 * hosts or in the systemwide list.
  	 */
  	host_file = user_hostfile;
  	host_status = check_host_in_hostfile(host_file, host, host_key,
  	    file_key, &host_line);
  	if (host_status == HOST_NEW) {
  		host_file = system_hostfile;
  		host_status = check_host_in_hostfile(host_file, host, host_key,
  		    file_key, &host_line);
  	}
  	/*
  	 * Also perform check for the ip address, skip the check if we are
  	 * localhost or the hostname was an ip address to begin with
  	 */
  	if (options.check_host_ip) {
  		Key *ip_key = key_new(host_key->type);
  
  		ip_file = user_hostfile;
  		ip_status = check_host_in_hostfile(ip_file, ip, host_key,
  		    ip_key, &ip_line);
  		if (ip_status == HOST_NEW) {
  			ip_file = system_hostfile;
  			ip_status = check_host_in_hostfile(ip_file, ip,
  			    host_key, ip_key, &ip_line);
  		}
  		if (host_status == HOST_CHANGED &&
  		    (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
  			host_ip_differ = 1;
  
  		key_free(ip_key);
  	} else
  		ip_status = host_status;
  
  	key_free(file_key);
  
  	switch (host_status) {
  	case HOST_OK:
  		/* The host is known and the key matches. */
  		debug("Host '%.200s' is known and matches the %s host key.",
  		    host, type);
  		debug("Found key in %s:%d", host_file, host_line);
  		if (options.check_host_ip && ip_status == HOST_NEW) {
  			if (readonly)
  				logit("%s host key for IP address "
  				    "'%.128s' not in list of known hosts.",
  				    type, ip);
  			else if (!add_host_to_hostfile(user_hostfile, ip,
  			    host_key, options.hash_known_hosts))
  				logit("Failed to add the %s host key for IP "
  				    "address '%.128s' to the list of known "
  				    "hosts (%.30s).", type, ip, user_hostfile);
  			else
  				logit("Warning: Permanently added the %s host "
  				    "key for IP address '%.128s' to the list "
  				    "of known hosts.", type, ip);
  		} else if (options.visual_host_key) {
  			fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
  			ra = key_fingerprint(host_key, SSH_FP_MD5,
  			    SSH_FP_RANDOMART);
  			logit("Host key fingerprint is %s\n%s\n", fp, ra);
  			xfree(ra);
  			xfree(fp);
  		}
  		break;
  	case HOST_NEW:
  		if (options.host_key_alias == NULL && port != 0 &&
  		    port != SSH_DEFAULT_PORT) {
  			debug("checking without port identifier");
  			if (check_host_key(hostname, hostaddr, 0, host_key,
  			    ROQUIET, user_hostfile, system_hostfile) == 0) {
  				debug("found matching key w/out port");
  				break;
  			}
  		}
  		if (readonly)
  			goto fail;
  		/* The host is new. */
  		if (options.strict_host_key_checking == 1) {
  			/*
  			 * User has requested strict host key checking.  We
  			 * will not add the host key automatically.  The only
  			 * alternative left is to abort.
  			 */
  			error("No %s host key is known for %.200s and you "
  			    "have requested strict checking.", type, host);
  			goto fail;
  		} else if (options.strict_host_key_checking == 2) {
  			char msg1[1024], msg2[1024];
  
  			if (show_other_keys(host, host_key))
  				snprintf(msg1, sizeof(msg1),
  				    "\nbut keys of different type are already"
  				    " known for this host.");
  			else
  				snprintf(msg1, sizeof(msg1), ".");
  			/* The default */
  			fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
  			ra = key_fingerprint(host_key, SSH_FP_MD5,
  			    SSH_FP_RANDOMART);
  			msg2[0] = '\0';
  			if (options.verify_host_key_dns) {
  				if (matching_host_key_dns)
  					snprintf(msg2, sizeof(msg2),
  					    "Matching host key fingerprint"
  					    " found in DNS.\n");
  				else
  					snprintf(msg2, sizeof(msg2),
  					    "No matching host key fingerprint"
  					    " found in DNS.\n");
  			}
  			snprintf(msg, sizeof(msg),
  			    "The authenticity of host '%.200s (%s)' can't be "
  			    "established%s\n"
  			    "%s key fingerprint is %s.%s%s\n%s"
  			    "Are you sure you want to continue connecting "
  			    "(yes/no)? ",
  			    host, ip, msg1, type, fp,
  			    options.visual_host_key ? "\n" : "",
  			    options.visual_host_key ? ra : "",
  			    msg2);
  			xfree(ra);
  			xfree(fp);
  			if (!confirm(msg))
  				goto fail;
  		}
  		/*
  		 * If not in strict mode, add the key automatically to the
  		 * local known_hosts file.
  		 */
  		if (options.check_host_ip && ip_status == HOST_NEW) {
  			snprintf(hostline, sizeof(hostline), "%s,%s",
  			    host, ip);
  			hostp = hostline;
  			if (options.hash_known_hosts) {
  				/* Add hash of host and IP separately */
  				r = add_host_to_hostfile(user_hostfile, host,
  				    host_key, options.hash_known_hosts) &&
  				    add_host_to_hostfile(user_hostfile, ip,
  				    host_key, options.hash_known_hosts);
  			} else {
  				/* Add unhashed "host,ip" */
  				r = add_host_to_hostfile(user_hostfile,
  				    hostline, host_key,
  				    options.hash_known_hosts);
  			}
  		} else {
  			r = add_host_to_hostfile(user_hostfile, host, host_key,
  			    options.hash_known_hosts);
  			hostp = host;
  		}
  
  		if (!r)
  			logit("Failed to add the host to the list of known "
  			    "hosts (%.500s).", user_hostfile);
  		else
  			logit("Warning: Permanently added '%.200s' (%s) to the "
  			    "list of known hosts.", hostp, type);
  		break;
  	case HOST_CHANGED:
  		if (readonly == ROQUIET)
  			goto fail;
  		if (options.check_host_ip && host_ip_differ) {
  			char *key_msg;
  			if (ip_status == HOST_NEW)
  				key_msg = "is unknown";
  			else if (ip_status == HOST_OK)
  				key_msg = "is unchanged";
  			else
  				key_msg = "has a different value";
  			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
  			error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
  			error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
  			error("The %s host key for %s has changed,", type, host);
  			error("and the key for the corresponding IP address %s", ip);
  			error("%s. This could either mean that", key_msg);
  			error("DNS SPOOFING is happening or the IP address for the host");
  			error("and its host key have changed at the same time.");
  			if (ip_status != HOST_NEW)
  				error("Offending key for IP in %s:%d", ip_file, ip_line);
  		}
  		/* The host key has changed. */
  		warn_changed_key(host_key);
  		error("Add correct host key in %.100s to get rid of this message.",
  		    user_hostfile);
  		error("Offending key in %s:%d", host_file, host_line);
  
  		/*
  		 * If strict host key checking is in use, the user will have
  		 * to edit the key manually and we can only abort.
  		 */
  		if (options.strict_host_key_checking) {
  			error("%s host key for %.200s has changed and you have "
  			    "requested strict checking.", type, host);
  			goto fail;
  		}
  
  		/*
  		 * If strict host key checking has not been requested, allow
  		 * the connection but without MITM-able authentication or
  		 * forwarding.
  		 */
  		if (options.password_authentication) {
  			error("Password authentication is disabled to avoid "
  			    "man-in-the-middle attacks.");
  			options.password_authentication = 0;
  			cancelled_forwarding = 1;
  		}
  		if (options.kbd_interactive_authentication) {
  			error("Keyboard-interactive authentication is disabled"
  			    " to avoid man-in-the-middle attacks.");
  			options.kbd_interactive_authentication = 0;
  			options.challenge_response_authentication = 0;
  			cancelled_forwarding = 1;
  		}
  		if (options.challenge_response_authentication) {
  			error("Challenge/response authentication is disabled"
  			    " to avoid man-in-the-middle attacks.");
  			options.challenge_response_authentication = 0;
  			cancelled_forwarding = 1;
  		}
  		if (options.forward_agent) {
  			error("Agent forwarding is disabled to avoid "
  			    "man-in-the-middle attacks.");
  			options.forward_agent = 0;
  			cancelled_forwarding = 1;
  		}
  		if (options.forward_x11) {
  			error("X11 forwarding is disabled to avoid "
  			    "man-in-the-middle attacks.");
  			options.forward_x11 = 0;
  			cancelled_forwarding = 1;
  		}
  		if (options.num_local_forwards > 0 ||
  		    options.num_remote_forwards > 0) {
  			error("Port forwarding is disabled to avoid "
  			    "man-in-the-middle attacks.");
  			options.num_local_forwards =
  			    options.num_remote_forwards = 0;
  			cancelled_forwarding = 1;
  		}
  		if (options.tun_open != SSH_TUNMODE_NO) {
  			error("Tunnel forwarding is disabled to avoid "
  			    "man-in-the-middle attacks.");
  			options.tun_open = SSH_TUNMODE_NO;
  			cancelled_forwarding = 1;
  		}
  		if (options.exit_on_forward_failure && cancelled_forwarding)
  			fatal("Error: forwarding disabled due to host key "
  			    "check failure");
  		
  		/*
  		 * XXX Should permit the user to change to use the new id.
  		 * This could be done by converting the host key to an
  		 * identifying sentence, tell that the host identifies itself
  		 * by that sentence, and ask the user if he/she whishes to
  		 * accept the authentication.
  		 */
  		break;
  	case HOST_FOUND:
  		fatal("internal error");
  		break;
  	}
  
  	if (options.check_host_ip && host_status != HOST_CHANGED &&
  	    ip_status == HOST_CHANGED) {
  		snprintf(msg, sizeof(msg),
  		    "Warning: the %s host key for '%.200s' "
  		    "differs from the key for the IP address '%.128s'"
  		    "\nOffending key for IP in %s:%d",
  		    type, host, ip, ip_file, ip_line);
  		if (host_status == HOST_OK) {
  			len = strlen(msg);
  			snprintf(msg + len, sizeof(msg) - len,
  			    "\nMatching host key in %s:%d",
  			    host_file, host_line);
  		}
  		if (options.strict_host_key_checking == 1) {
  			logit("%s", msg);
  			error("Exiting, you have requested strict checking.");
  			goto fail;
  		} else if (options.strict_host_key_checking == 2) {
  			strlcat(msg, "\nAre you sure you want "
  			    "to continue connecting (yes/no)? ", sizeof(msg));
  			if (!confirm(msg))
  				goto fail;
  		} else {
  			logit("%s", msg);
  		}
  	}
  
  	xfree(ip);
  	xfree(host);
  	return 0;
  
  fail:
  	xfree(ip);
  	xfree(host);
  	return -1;
  }
  
  /* returns 0 if key verifies or -1 if key does NOT verify */
  int
  verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
  {
  	struct stat st;
  	int flags = 0;
  
  	if (options.verify_host_key_dns &&
  	    verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
  
  		if (flags & DNS_VERIFY_FOUND) {
  
  			if (options.verify_host_key_dns == 1 &&
  			    flags & DNS_VERIFY_MATCH &&
  			    flags & DNS_VERIFY_SECURE)
  				return 0;
  
  			if (flags & DNS_VERIFY_MATCH) {
  				matching_host_key_dns = 1;
  			} else {
  				warn_changed_key(host_key);
  				error("Update the SSHFP RR in DNS with the new "
  				    "host key to get rid of this message.");
  			}
  		}
  	}
  
  	/* return ok if the key can be found in an old keyfile */
  	if (stat(options.system_hostfile2, &st) == 0 ||
  	    stat(options.user_hostfile2, &st) == 0) {
  		if (check_host_key(host, hostaddr, options.port, host_key,
  		    RDONLY, options.user_hostfile2,
  		    options.system_hostfile2) == 0)
  			return 0;
  	}
  	return check_host_key(host, hostaddr, options.port, host_key,
  	    RDRW, options.user_hostfile, options.system_hostfile);
  }
  
  /*
   * Starts a dialog with the server, and authenticates the current user on the
   * server.  This does not need any extra privileges.  The basic connection
   * to the server must already have been established before this is called.
   * If login fails, this function prints an error and never returns.
   * This function does not require super-user privileges.
   */
  void
  ssh_login(Sensitive *sensitive, const char *orighost,
      struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
  {
  	char *host, *cp;
  	char *server_user, *local_user;
  
  	local_user = xstrdup(pw->pw_name);
  	server_user = options.user ? options.user : local_user;
  
  	/* Convert the user-supplied hostname into all lowercase. */
  	host = xstrdup(orighost);
  	for (cp = host; *cp; cp++)
  		if (isupper(*cp))
  			*cp = (char)tolower(*cp);
  
  	if(options.obfuscate_handshake)
  		obfuscate_send_seed(packet_get_connection_out());
  
  	/* Exchange protocol version identification strings with the server. */
  	ssh_exchange_identification(timeout_ms);
  
  	/* Put the connection into non-blocking mode. */
  	packet_set_nonblocking();
  
  	/* key exchange */
  	/* authenticate user */
  	if (compat20) {
  		ssh_kex2(host, hostaddr);
  		ssh_userauth2(local_user, server_user, host, sensitive);
  	} else {
  		ssh_kex(host, hostaddr);
  		ssh_userauth1(local_user, server_user, host, sensitive);
  	}
  	xfree(local_user);
  }
  
  void
  ssh_put_password(char *password)
  {
  	int size;
  	char *padded;
  
  	if (datafellows & SSH_BUG_PASSWORDPAD) {
  		packet_put_cstring(password);
  		return;
  	}
  	size = roundup(strlen(password) + 1, 32);
  	padded = xcalloc(1, size);
  	strlcpy(padded, password, size);
  	packet_put_string(padded, size);
  	memset(padded, 0, size);
  	xfree(padded);
  }
  
  static int
  show_key_from_file(const char *file, const char *host, int keytype)
  {
  	Key *found;
  	char *fp, *ra;
  	int line, ret;
  
  	found = key_new(keytype);
  	if ((ret = lookup_key_in_hostfile_by_type(file, host,
  	    keytype, found, &line))) {
  		fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
  		ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART);
  		logit("WARNING: %s key found for host %s\n"
  		    "in %s:%d\n"
  		    "%s key fingerprint %s.\n%s\n",
  		    key_type(found), host, file, line,
  		    key_type(found), fp, ra);
  		xfree(ra);
  		xfree(fp);
  	}
  	key_free(found);
  	return (ret);
  }
  
  /* print all known host keys for a given host, but skip keys of given type */
  static int
  show_other_keys(const char *host, Key *key)
  {
  	int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
  	int i, found = 0;
  
  	for (i = 0; type[i] != -1; i++) {
  		if (type[i] == key->type)
  			continue;
  		if (type[i] != KEY_RSA1 &&
  		    show_key_from_file(options.user_hostfile2, host, type[i])) {
  			found = 1;
  			continue;
  		}
  		if (type[i] != KEY_RSA1 &&
  		    show_key_from_file(options.system_hostfile2, host, type[i])) {
  			found = 1;
  			continue;
  		}
  		if (show_key_from_file(options.user_hostfile, host, type[i])) {
  			found = 1;
  			continue;
  		}
  		if (show_key_from_file(options.system_hostfile, host, type[i])) {
  			found = 1;
  			continue;
  		}
  		debug2("no key of type %d for host %s", type[i], host);
  	}
  	return (found);
  }
  
  static void
  warn_changed_key(Key *host_key)
  {
  	char *fp;
  	const char *type = key_type(host_key);
  
  	fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
  
  	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
  	error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
  	error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
  	error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
  	error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
  	error("It is also possible that the %s host key has just been changed.", type);
  	error("The fingerprint for the %s key sent by the remote host is\n%s.",
  	    type, fp);
  	error("Please contact your system administrator.");
  
  	xfree(fp);
  }
  
  /*
   * Execute a local command
   */
  int
  ssh_local_cmd(const char *args)
  {
  	char *shell;
  	pid_t pid;
  	int status;
  
  	if (!options.permit_local_command ||
  	    args == NULL || !*args)
  		return (1);
  
  	if ((shell = getenv("SHELL")) == NULL)
  		shell = _PATH_BSHELL;
  
  	pid = fork();
  	if (pid == 0) {
  		debug3("Executing %s -c \"%s\"", shell, args);
  		execl(shell, shell, "-c", args, (char *)NULL);
  		error("Couldn't execute %s -c \"%s\": %s",
  		    shell, args, strerror(errno));
  		_exit(1);
  	} else if (pid == -1)
  		fatal("fork failed: %.100s", strerror(errno));
  	while (waitpid(pid, &status, 0) == -1)
  		if (errno != EINTR)
  			fatal("Couldn't wait for child: %s", strerror(errno));
  
  	if (!WIFEXITED(status))
  		return (1);
  
  	return (WEXITSTATUS(status));
  }
  