ssh.c

OpenSSL Source code for SFTP, SSH, and many others

/*
 * Author: Tatu Ylonen <[e-mail]>
 * Copyright (c) 1995 Tatu Ylonen <[e-mail]>, 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 Markus Friedl.  All rights reserved.
 *
 * Modified to work with SSL by Niels Provos <[e-mail]>
 * 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 "includes.h"
RCSID("$OpenBSD: ssh.c,v 1.179 2002/06/12 01:09:52 markus Exp $");

#include <openssl/evp.h>
#include <openssl/err.h>

#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "compat.h"
#include "cipher.h"
#include "xmalloc.h"
#include "packet.h"
#include "buffer.h"
#include "channels.h"
#include "key.h"
#include "authfd.h"
#include "authfile.h"
#include "pathnames.h"
#include "clientloop.h"
#include "log.h"
#include "readconf.h"
#include "sshconnect.h"
#include "tildexpand.h"
#include "dispatch.h"
#include "misc.h"
#include "kex.h"
#include "mac.h"
#include "sshtty.h"

#ifdef SMARTCARD
#include "scard.h"
#endif

#ifdef HAVE___PROGNAME
extern char *__progname;
#else
char *__progname;
#endif

/* Flag indicating whether IPv4 or IPv6.  This can be set on the command line.
   Default value is AF_UNSPEC means both IPv4 and IPv6. */
#ifdef IPV4_DEFAULT
int IPv4or6 = AF_INET;
#else
int IPv4or6 = AF_UNSPEC;
#endif

/* Flag indicating whether debug mode is on.  This can be set on the command line. */
int debug_flag = 0;

/* Flag indicating whether a tty should be allocated */
int tty_flag = 0;
int no_tty_flag = 0;
int force_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 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;

/* socket address the host resolves to */
struct sockaddr_storage hostaddr;

/* Private host keys. */
Sensitive sensitive_data;

/* Original real UID. */
uid_t original_real_uid;
uid_t original_effective_uid;

/* command to be executed */
Buffer command;

/* Should we execute a command or invoke a subsystem? */
int subsystem_flag = 0;

/* # of replies received for global requests */
static int client_global_request_id = 0;

/* Prints a help message to the user.  This function never returns. */

static void
usage(void)
{
	fprintf(stderr, "Usage: %s [options] host [command]\n", __progname);
	fprintf(stderr, "Options:\n");
	fprintf(stderr, "  -l user     Log in using this user name.\n");
	fprintf(stderr, "  -n          Redirect input from " _PATH_DEVNULL ".\n");
	fprintf(stderr, "  -F config   Config file (default: ~/%s).\n",
	     _PATH_SSH_USER_CONFFILE);
	fprintf(stderr, "  -A          Enable authentication agent forwarding.\n");
	fprintf(stderr, "  -a          Disable authentication agent forwarding (default).\n");
#ifdef AFS
	fprintf(stderr, "  -k          Disable Kerberos ticket and AFS token forwarding.\n");
#endif				/* AFS */
	fprintf(stderr, "  -X          Enable X11 connection forwarding.\n");
	fprintf(stderr, "  -x          Disable X11 connection forwarding (default).\n");
	fprintf(stderr, "  -i file     Identity for public key authentication "
	    "(default: ~/.ssh/identity)\n");
#ifdef SMARTCARD
	fprintf(stderr, "  -I reader   Set smartcard reader.\n");
#endif
	fprintf(stderr, "  -t          Tty; allocate a tty even if command is given.\n");
	fprintf(stderr, "  -T          Do not allocate a tty.\n");
	fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
	fprintf(stderr, "              Multiple -v increases verbosity.\n");
	fprintf(stderr, "  -V          Display version number only.\n");
	fprintf(stderr, "  -P          Don't allocate a privileged port.\n");
	fprintf(stderr, "  -q          Quiet; don't display any warning messages.\n");
	fprintf(stderr, "  -f          Fork into background after authentication.\n");
	fprintf(stderr, "  -e char     Set escape character; ``none'' = disable (default: ~).\n");

	fprintf(stderr, "  -c cipher   Select encryption algorithm\n");
	fprintf(stderr, "  -m macs     Specify MAC algorithms for protocol version 2.\n");
	fprintf(stderr, "  -p port     Connect to this port.  Server must be on the same port.\n");
	fprintf(stderr, "  -L listen-port:host:port   Forward local port to remote address\n");
	fprintf(stderr, "  -R listen-port:host:port   Forward remote port to local address\n");
	fprintf(stderr, "              These cause %s to listen for connections on a port, and\n", __progname);
	fprintf(stderr, "              forward them to the other side by connecting to host:port.\n");
	fprintf(stderr, "  -D port     Enable dynamic application-level port forwarding.\n");
	fprintf(stderr, "  -C          Enable compression.\n");
	fprintf(stderr, "  -N          Do not execute a shell or command.\n");
	fprintf(stderr, "  -g          Allow remote hosts to connect to forwarded ports.\n");
	fprintf(stderr, "  -1          Force protocol version 1.\n");
	fprintf(stderr, "  -2          Force protocol version 2.\n");
	fprintf(stderr, "  -4          Use IPv4 only.\n");
	fprintf(stderr, "  -6          Use IPv6 only.\n");
	fprintf(stderr, "  -o 'option' Process the option as if it was read from a configuration file.\n");
	fprintf(stderr, "  -s          Invoke command (mandatory) as SSH2 subsystem.\n");
	fprintf(stderr, "  -b addr     Local IP address.\n");
	exit(1);
}

static int ssh_session(void);
static int ssh_session2(void);
static void load_public_identity_files(void);

/*
 * Main program for the ssh client.
 */
int
main(int ac, char **av)
{
	int i, opt, exit_status;
	u_short fwd_port, fwd_host_port;
	char sfwd_port[6], sfwd_host_port[6];
	char *p, *cp, buf[256];
	struct stat st;
	struct passwd *pw;
	int dummy;
	extern int optind, optreset;
	extern char *optarg;

	__progname = get_progname(av[0]);
	init_rng();

	/*
	 * Save the original real uid.  It will be needed later (uid-swapping
	 * may clobber the real uid).
	 */
	original_real_uid = getuid();
	original_effective_uid = geteuid();

#ifdef HAVE_SETRLIMIT
	/* If we are installed setuid root be careful to not drop core. */
	if (original_real_uid != original_effective_uid) {
		struct rlimit rlim;
		rlim.rlim_cur = rlim.rlim_max = 0;
		if (setrlimit(RLIMIT_CORE, &rlim) < 0)
			fatal("setrlimit failed: %.100s", strerror(errno));
	}
#endif
	/* Get user data. */
	pw = getpwuid(original_real_uid);
	if (!pw) {
		log("You don't exist, go away!");
		exit(1);
	}
	/* Take a copy of the returned structure. */
	pw = pwcopy(pw);

	/*
	 * Use uid-swapping to give up root privileges for the duration of
	 * option processing.  We will re-instantiate the rights when we are
	 * ready to create the privileged port, and will permanently drop
	 * them when the port has been created (actually, when the connection
	 * has been made, as we may need to create the port several times).
	 */
	PRIV_END;

	/*
	 * 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);

	/* Initialize option structure to indicate that no values have been set. */
	initialize_options(&options);

	/* Parse command-line arguments. */
	host = NULL;

again:
	while ((opt = getopt(ac, av,
	    "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:NPR:TVX")) != -1) {
		switch (opt) {
		case '1':
			options.protocol = SSH_PROTO_1;
			break;
		case '2':
			options.protocol = SSH_PROTO_2;
			break;
		case '4':
			IPv4or6 = AF_INET;
			break;
		case '6':
			IPv4or6 = 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 'g':
			options.gateway_ports = 1;
			break;
		case 'P':
			options.use_privileged_port = 0;
			break;
		case 'a':
			options.forward_agent = 0;
			break;
		case 'A':
			options.forward_agent = 1;
			break;
#ifdef AFS
		case 'k':
			options.kerberos_tgt_passing = 0;
			options.afs_token_passing = 0;
			break;
#endif
		case 'i':
			if (stat(optarg, &st) < 0) {
				fprintf(stderr, "Warning: Identity file %s "
				    "does not exist.\n", optarg);
				break;
			}
			if (options.num_identity_files >=
			    SSH_MAX_IDENTITY_FILES)
				fatal("Too many identity files specified "
				    "(max %d)", SSH_MAX_IDENTITY_FILES);
			options.identity_files[options.num_identity_files++] =
			    xstrdup(optarg);
			break;
		case 'I':
#ifdef SMARTCARD
			options.smartcard_device = xstrdup(optarg);
#else
			fprintf(stderr, "no support for smartcards.\n");
#endif
			break;
		case 't':
			if (tty_flag)
				force_tty_flag = 1;
			tty_flag = 1;
			break;
		case 'v':
			if (0 == debug_flag) {
				debug_flag = 1;
				options.log_level = SYSLOG_LEVEL_DEBUG1;
			} else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
				options.log_level++;
				break;
			} else
				fatal("Too high debugging level.");
			/* fallthrough */
		case 'V':
			fprintf(stderr,
			    "%s, SSH protocols %d.%d/%d.%d, OpenSSL 0x%8.8lx\n",
			    SSH_VERSION,
			    PROTOCOL_MAJOR_1, PROTOCOL_MINOR_1,
			    PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2,
			    SSLeay());
			if (opt == 'V')
				exit(0);
			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(1);
			}
			break;
		case 'c':
			if (ciphers_valid(optarg)) {
				/* SSH2 only */
				options.ciphers = xstrdup(optarg);
				options.cipher = SSH_CIPHER_ILLEGAL;
			} else {
				/* SSH1 only */
				options.cipher = cipher_number(optarg);
				if (options.cipher == -1) {
					fprintf(stderr,
					    "Unknown cipher type '%s'\n",
					    optarg);