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File: [local] / src / usr.bin / ssh / sshconnect.c (download)

Revision 1.219, Fri Feb 26 20:29:54 2010 UTC (14 years, 3 months ago) by djm
Branch: MAIN
Changes since 1.218: +65 -13 lines

Add support for certificate key types for users and hosts.

OpenSSH certificate key types are not X.509 certificates, but a much
simpler format that encodes a public key, identity information and
some validity constraints and signs it with a CA key. CA keys are
regular SSH keys. This certificate style avoids the attack surface
of X.509 certificates and is very easy to deploy.

Certified host keys allow automatic acceptance of new host keys
when a CA certificate is marked as trusted in ~/.ssh/known_hosts.
see VERIFYING HOST KEYS in ssh(1) for details.

Certified user keys allow authentication of users when the signing
CA key is marked as trusted in authorized_keys. See "AUTHORIZED_KEYS
FILE FORMAT" in sshd(8) for details.

Certificates are minted using ssh-keygen(1), documentation is in
the "CERTIFICATES" section of that manpage.

Documentation on the format of certificates is in the file
PROTOCOL.certkeys

feedback and ok markus@

/* $OpenBSD: sshconnect.c,v 1.219 2010/02/26 20:29:54 djm 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 <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/time.h>

#include <netinet/in.h>

#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <paths.h>
#include <signal.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "xmalloc.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 "roaming.h"
#include "ssh2.h"
#include "version.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);

	/* 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));
		return -1;
	}
	fcntl(sock, F_SETFD, FD_CLOEXEC);

	/* 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);

	return 0;
}

/*
 * Waits for the server identification string, and sends our own
 * identification string.
 */
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;
	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 = roaming_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 (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");
	if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf))
	    != strlen(buf))
		fatal("write: %.100s", strerror(errno));
	client_version_string = xstrdup(buf);
	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;
	}
}

static int
check_host_cert(const char *host, const Key *host_key)
{
	const char *reason;

	if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
		error("%s", reason);
		return 0;
	}
	if (buffer_len(&host_key->cert->constraints) != 0) {
		error("Certificate for %s contains unsupported constraint(s)",
		    host);
		return 0;
	}
	return 1;
}

/*
 * 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, *raw_key = NULL;
	const char *type;
	char *ip = NULL, *host = NULL;
	char hostline[1000], *hostp, *fp, *ra;
	HostStatus host_status;
	HostStatus ip_status;
	int r, want_cert, local = 0, host_ip_differ = 0;
	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;
		break;
	case AF_INET6:
		local = IN6_IS_ADDR_LOOPBACK(
		    &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
		break;
	default:
		local = 0;
		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, hostaddr->sa_len, 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);
	}

 retry:
	want_cert = key_is_cert(host_key);
	type = key_type(host_key);

	/*
	 * 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(key_is_cert(host_key) ? KEY_UNSPEC : 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, looking for a certificate, or the hostname was an ip
	 * address to begin with.
	 */
	if (!want_cert && 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 %s.",
		    host, type, want_cert ? "certificate" : "key");
		debug("Found %s in %s:%d",
		    want_cert ? "certificate" : "key", host_file, host_line);
		if (want_cert && !check_host_cert(hostname, host_key))
			goto fail;
		if (options.check_host_ip && ip_status == HOST_NEW) {
			if (readonly || want_cert)
				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 || want_cert)
			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 (want_cert) {
			/*
			 * This is only a debug() since it is valid to have
			 * CAs with wildcard DNS matches that don't match
			 * all hosts that one might visit.
			 */
			debug("Host certificate authority does not "
			    "match %s in %s:%d", CA_MARKER,
			    host_file, host_line);
			goto fail;
		}
		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 wishes 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:
	if (want_cert) {
		/*
		 * No matching certificate. Downgrade cert to raw key and
		 * search normally.
		 */
		debug("No matching CA found. Retry with plain key");
		raw_key = key_from_private(host_key);
		if (key_drop_cert(raw_key) != 0)
			fatal("Couldn't drop certificate");
		host_key = raw_key;
		goto retry;
	}
	if (raw_key != NULL)
		key_free(raw_key);
	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;

	/* XXX certs are not yet supported for DNS */
	if (!key_is_cert(host_key) && 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);

	/* 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));
}