lshd.c

/* lshd.c
 *
 * main server program.
 *
 * $Id$ */

/* lsh, an implementation of the ssh protocol
 *
 * Copyright (C) 1998 Niels Mller
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "algorithms.h"
#include "alist.h"
#include "atoms.h"
#include "channel.h"
#include "channel_commands.h"
#include "charset.h"
#include "compress.h"
#include "connection_commands.h"
#include "crypto.h"
#include "daemon.h"
#include "format.h"
#include "io.h"
#include "io_commands.h"
#include "lookup_verifier.h"
#include "randomness.h"
#include "reaper.h"
#include "server.h"
#include "server_authorization.h"
#include "server_keyexchange.h"
#include "server_pty.h"
#include "server_session.h"
#include "sexp.h"
#include "sexp_commands.h"
#include "spki_commands.h"
#include "ssh.h"
#include "tcpforward.h"
#include "tcpforward_commands.h"
#include "tcpforward_commands.h"
#include "server_userauth.h"
#include "version.h"
#include "werror.h"
#include "xalloc.h"

#include "lsh_argp.h"

/* Forward declarations */
struct command_simple options2local;
#define OPTIONS2LOCAL (&options2local.super.super)

static struct command options2keyfile;
#define OPTIONS2KEYFILE (&options2keyfile.super)

struct command_simple options2signature_algorithms;
#define OPTIONS2SIGNATURE_ALGORITHMS \
  (&options2signature_algorithms.super.super)

#include "lshd.c.x"

#include <assert.h>

#include <errno.h>
#include <locale.h>
#include <stdio.h>
#include <string.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif

/* Block size for stdout and stderr buffers */
#define BLOCK_SIZE 32768


/* Option parsing */

const char *argp_program_version
= "lshd-" VERSION ", secsh protocol version " SERVER_PROTOCOL_VERSION;

const char *argp_program_bug_address = BUG_ADDRESS;

#define OPT_NO 0x400
#define OPT_SSH1_FALLBACK 0x200
#define OPT_INTERFACE 0x201

#define OPT_TCPIP_FORWARD 0x202
#define OPT_NO_TCPIP_FORWARD (OPT_TCPIP_FORWARD | OPT_NO)
#define OPT_PTY 0x203
#define OPT_NO_PTY (OPT_PTY | OPT_NO)

#define OPT_DAEMONIC 0x204
#define OPT_NO_DAEMONIC (OPT_DAEMONIC | OPT_NO)
#define OPT_PIDFILE 0x205
#define OPT_NO_PIDFILE (OPT_PIDFILE | OPT_NO)
#define OPT_CORE 0x207

#define OPT_PUBLICKEY 0x208
#define OPT_NO_PUBLICKEY (OPT_PUBLICKEY | OPT_NO)
#define OPT_PASSWORD 0x209
#define OPT_NO_PASSWORD (OPT_PASSWORD | OPT_NO)

#define OPT_ROOT_LOGIN 0x20A
#define OPT_NO_ROOT_LOGIN (OPT_ROOT_LOGIN | OPT_NO)

/* GABA:
   (class
     (name lshd_options)
     (super algorithms_options)
     (vars
       (backend object io_backend)
       (signature_algorithms object alist)
       (style . sexp_argp_state)
       (interface . "char *")
       (port . "char *")
       (hostkey . "char *")
       (local object address_info)

       (with_publickey . int)
       (with_password . int)
       (allow_root . int)

       (with_tcpip_forward . int)
       (with_pty . int)
       
       (userauth_methods object int_list)
       (userauth_algorithms object alist)
       
       (sshd1 object ssh1_fallback)
       (daemonic . int)
       (corefile . int)
       (pid_file . "const char *")
       ; -1 means use pid file iff we're in daemonic mode
       (use_pid_file . int)))
*/

static struct lshd_options *
make_lshd_options(struct io_backend *backend,
		  struct randomness *random,
		  struct alist *algorithms)
{
  NEW(lshd_options, self);

  init_algorithms_options(&self->super, algorithms);

  self->backend = backend;
  self->signature_algorithms
    = make_alist(1,
		 ATOM_DSA, make_dsa_algorithm(random), -1);
  self->style = SEXP_TRANSPORT;
  self->interface = NULL;
  self->port = "ssh";
  /* FIXME: this should perhaps use sysconfdir */  
  self->hostkey = "/etc/lsh_host_key";
  self->local = NULL;

  self->with_publickey = 1;
  self->with_password = 1;
  self->with_tcpip_forward = 1;
  self->with_pty = 1;
  self->allow_root = 0;
  
  self->userauth_methods = NULL;
  self->userauth_algorithms = NULL;
  
  self->sshd1 = NULL;
  self->daemonic = 0;

  /* FIXME: Make the default a configure time option? */
  self->pid_file = "/var/run/lshd.pid";
  self->use_pid_file = -1;
  self->corefile = 0;
  
  return self;
}

/* Port to listen on */
COMMAND_SIMPLE(options2local)
{
  CAST(lshd_options, options, a);
  return &options->local->super;
}

/* alist of signature algorithms */
COMMAND_SIMPLE(options2signature_algorithms)
{
  CAST(lshd_options, options, a);
  return &options->signature_algorithms->super;
}

/* Read server's private key */
static void
do_options2keyfile(struct command *ignored UNUSED,
		   struct lsh_object *a,
		   struct command_continuation *c,
		   struct exception_handler *e)
{
  CAST(lshd_options, options, a);
  
  struct lsh_fd *f;

  f = io_read_file(options->backend, options->hostkey, e);

  if (f)
    COMMAND_RETURN(c, f);
  else
    {
      werror("Failed to open '%z' (errno = %i): %z.\n",
	     options->hostkey, errno, STRERROR(errno));
      EXCEPTION_RAISE(e, make_io_exception(EXC_IO_OPEN_READ, NULL, errno, NULL));
    }
}

static struct command options2keyfile =
STATIC_COMMAND(do_options2keyfile);


static const struct argp_option
main_options[] =
{
  /* Name, key, arg-name, flags, doc, group */
  { "interface", OPT_INTERFACE, "interface", 0,
    "Listen on this network interface", 0 }, 
  { "port", 'p', "Port", 0, "Listen on this port.", 0 },
  { "host-key", 'h', "Key file", 0, "Location of the server's private key.", 0},

#if WITH_SSH1_FALLBACK
  { "ssh1-fallback", OPT_SSH1_FALLBACK, "File name", OPTION_ARG_OPTIONAL,
    "Location of the sshd1 program, for falling back to version 1 of the Secure Shell protocol.", 0 },
#endif /* WITH_SSH1_FALLBACK */

  { "password", OPT_PASSWORD, NULL, 0,
    "Enable password user authentication (default).", 0},
  { "no-password", OPT_NO_PASSWORD, NULL, 0,
    "Disable password user authentication.", 0},

  { "publickey", OPT_PUBLICKEY, NULL, 0,
    "Enable publickey user authentication (default).", 0},
  { "no-publickey", OPT_NO_PUBLICKEY, NULL, 0,
    "Disable publickey user authentication.", 0},

  { "root-login", OPT_ROOT_LOGIN, NULL, 0,
    "Allow root to login.", 0 },
  { "no-root-login", OPT_NO_ROOT_LOGIN, NULL, 0,
    "Don't allow root to login (default).", 0 },
  
#if WITH_TCP_FORWARD
  { "tcp-forward", OPT_TCPIP_FORWARD, NULL, 0, "Enable tcpip forwarding (default).", 0 },
  { "no-tcp-forward", OPT_NO_TCPIP_FORWARD, NULL, 0, "Disable tcpip forwarding.", 0 },
#endif /* WITH_TCP_FORWARD */

#if WITH_PTY_SUPPORT
  { "pty-support", OPT_PTY, NULL, 0, "Enable pty allocation (default).", 0 },
  { "no-pty-support", OPT_NO_PTY, NULL, 0, "Disable pty allocation.", 0 },
#endif /* WITH_PTY_SUPPORT */
  
  { NULL, 0, NULL, 0, "Daemonic behaviour", 0 },
  { "daemonic", OPT_DAEMONIC, NULL, 0, "Run in the background, redirect stdio to /dev/null, and chdir to /.", 0 },
  { "no-daemonic", OPT_NO_DAEMONIC, NULL, 0, "Run in the foreground, with messages to stderr (default).", 0 },
  { "pid-file", OPT_PIDFILE, "file name", 0, "Create a pid file. When running in daemonic mode, "
    "the default is /var/run/lshd.pid.", 0 },
  { "no-pid-file", OPT_NO_PIDFILE, NULL, 0, "Don't use any pid file. Default in non-daemonic mode.", 0 },
  { "enable-core", OPT_CORE, NULL, 0, "Dump core on fatal errors (disabled by default).", 0 },
    
  { NULL, 0, NULL, 0, NULL, 0 }
};

static const struct argp_child
main_argp_children[] =
{
  { &sexp_input_argp, 0, "", 0 },
  { &algorithms_argp, 0, "", 0 },
  { &werror_argp, 0, "", 0 },
  { NULL, 0, NULL, 0}
};

static error_t
main_argp_parser(int key, char *arg, struct argp_state *state)
{
  CAST(lshd_options, self, state->input);
  
  switch(key)
    {
    default:
      return ARGP_ERR_UNKNOWN;
    case ARGP_KEY_INIT:
      state->child_inputs[0] = &self->style;
      state->child_inputs[1] = &self->super;
      state->child_inputs[2] = NULL;
      break;
    case ARGP_KEY_ARG:
      argp_error(state, "Spurious arguments.");
      break;
      
    case ARGP_KEY_END:
      self->local = make_address_info_c(self->interface, self->port);

      if (!self->local)
	argp_error(state, "Invalid interface, port or service, %s:%s'.",
		   self->interface ? self->interface : "ANY",
		   self->port);
      if (self->use_pid_file < 0)
	self->use_pid_file = self->daemonic;

      if (self->with_password || self->with_publickey)
	{
	  int i = 0;
	  struct user_db *db = make_unix_user_db(self->allow_root);
	  
	  self->userauth_methods
	    = alloc_int_list(self->with_password + self->with_publickey);
	  self->userauth_algorithms = make_alist(0, -1);

	  if (self->with_password)
	    {
	      LIST(self->userauth_methods)[i++] = ATOM_PASSWORD;
	      ALIST_SET(self->userauth_algorithms,
			ATOM_PASSWORD, make_userauth_password(db));
	    }
	  if (self->with_publickey)
	    {
	      /* Doesn't use spki */
	      LIST(self->userauth_methods)[i++] = ATOM_PUBLICKEY;
	      ALIST_SET(self->userauth_algorithms,
			ATOM_PUBLICKEY,
			make_userauth_publickey
			(db,
			 make_alist(1,
				    ATOM_SSH_DSS,
				    make_authorization_db(ssh_format("authorized_keys_sha1"),
							  &sha1_algorithm),
				    
				    -1)));
	    }
	}
      else
	argp_error(state, "All user authentication methods disabled.");
      
      break;
      
    case 'p':
      self->port = arg;
      break;

    case 'h':
      self->hostkey = arg;
      break;

    case OPT_INTERFACE:
      self->interface = arg;
      break;

#if WITH_SSH1_FALLBACK
    case OPT_SSH1_FALLBACK:
      self->sshd1 = make_ssh1_fallback(arg ? arg : SSHD1);
      break;
#endif

    case OPT_PASSWORD:
      self->with_password = 1;
      break;
      
    case OPT_NO_PASSWORD:
      self->with_password = 0;
      break;

    case OPT_PUBLICKEY:
      self->with_publickey = 1;
      break;
      
    case OPT_NO_PUBLICKEY:
      self->with_publickey = 0;
      break;

    case OPT_ROOT_LOGIN:
      self->allow_root = 1;
      break;
      
#if WITH_TCP_FORWARD
    case OPT_TCPIP_FORWARD:
      self->with_tcpip_forward = 1;
      break;

    case OPT_NO_TCPIP_FORWARD:
      self->with_tcpip_forward = 0;
      break;
#endif /* WITH_TCP_FORWARD */
      
#if WITH_PTY_SUPPORT
    case OPT_PTY:
      self->with_pty = 1;
      break;
    case OPT_NO_PTY:
      self->with_pty = 0;
      break;
#endif /* WITH_PTY_SUPPORT */
	  
    case OPT_DAEMONIC:
      self->daemonic = 1;
      break;

    case OPT_NO_DAEMONIC:
      self->daemonic = 0;
      break;

    case OPT_PIDFILE:
      self->pid_file = arg;
      self->use_pid_file = 1;
      break;

    case OPT_NO_PIDFILE:
      self->use_pid_file = 0;
      break;

    case OPT_CORE:
      self->corefile = 1;
      break;
    }
  return 0;
}

static const struct argp
main_argp =
{ main_options, main_argp_parser, 
  NULL,
  "Server for the ssh-2 protocol.",
  main_argp_children,
  NULL, NULL
};


/* GABA:
   (expr
     (name lshd_listen)
     (params
       (listen object command)
       (handshake object handshake_info)
       (services object command) )
     (expr (lambda (options)
             (services (connection_handshake
	                    handshake
			    (spki_read_hostkeys (options2signature_algorithms options)
			                        (options2keyfile options))
			    (log_peer (listen (options2local options))))))))
*/

/* Invoked when the client requests the userauth service. */
/* GABA:
   (expr
     (name lshd_services)
     (params 
       (userauth object command))
     (expr
       (lambda (connection)
         ((userauth connection) connection))))
*/

/* Invoked when starting the ssh-connection service */
/* GABA:
   (expr
     (name lshd_connection_service)
     (params
       (login object command)     
       (hooks object object_list))
     (expr
       (lambda (user connection)
         ((progn hooks) (login user
	                       ; We have to initialize the connection
			       ; before logging in.
	                       (init_connection_service connection))))))
*/

static void
do_lshd_default_handler(struct exception_handler *s,
			const struct exception *e)
{
  switch(e->type)
    {
    case EXC_SEXP_SYNTAX:
    case EXC_SPKI_TYPE:
      werror("lshd: %z\n", e->msg);
      exit(EXIT_FAILURE);
    default:
      EXCEPTION_RAISE(s->parent, e);
    }
}

static struct exception_handler *
make_lshd_exception_handler(struct exception_handler *parent,
			    const char *context)
{
  return make_exception_handler(do_lshd_default_handler, parent, context);
}

int main(int argc, char **argv)
{
  struct lshd_options *options;
  
  struct reap *reaper;
  
  struct randomness *r;
  struct alist *algorithms;
  
  /* FIXME: Why not allocate backend statically? */
  NEW(io_backend, backend);
  init_backend(backend);

  /* For filtering messages. Could perhaps also be used when converting
   * strings to and from UTF8. */
  setlocale(LC_CTYPE, "");
  /* FIXME: Choose character set depending on the locale */
  set_local_charset(CHARSET_LATIN1);

  r = make_reasonably_random();
  
  algorithms = many_algorithms(1,
			       ATOM_DIFFIE_HELLMAN_GROUP1_SHA1,
			       make_dh_server(make_dh1(r)),
			       -1);
  
  options = make_lshd_options(backend, r, algorithms);
  
  argp_parse(&main_argp, argc, argv, 0, NULL, options);

  if (!options->corefile && !daemon_disable_core())
    {
      werror("Disabling of core dumps failed.\n");
      return EXIT_FAILURE;
    }
  
  if (options->daemonic)
    {
#if HAVE_SYSLOG
      set_error_syslog("lshd");
#else /* !HAVE_SYSLOG */
      werror("lshd: No syslog. Further messages will be directed to /dev/null.\n");
#endif /* !HAVE_SYSLOG */
    }

  if (options->daemonic)
    switch (daemon_init())
      {
      case 0:
	werror("lshd: Spawning into background failed.\n");
	return EXIT_FAILURE;
      case DAEMON_INETD:
	werror("lshd: spawning from inetd not yet supported.\n");
	return EXIT_FAILURE;
      case DAEMON_INIT:
      case DAEMON_NORMAL:
	break;
      default:
	fatal("Internal error\n");
      }
  
  if (options->use_pid_file && !daemon_pidfile(options->pid_file))
    {
      werror("lshd seems to be running already.\n");
      return EXIT_FAILURE;
    }
  
  reaper = make_reaper();
  
  {
    /* Commands to be invoked on the connection */
    struct object_list *connection_hooks;

    /* Supported channel requests */
    struct alist *supported_channel_requests
      = make_alist(2,
		   ATOM_SHELL, make_shell_handler(backend, reaper),
		   ATOM_EXEC, make_exec_handler(backend, reaper),
		   -1);
    
    
#if WITH_TCP_FORWARD
    if (options->with_tcpip_forward)
      connection_hooks = make_object_list
	(3,
	 make_tcpip_forward_hook(backend),
	 make_install_fix_global_request_handler
	 (ATOM_CANCEL_TCPIP_FORWARD, &tcpip_cancel_forward),
	 make_direct_tcpip_hook(backend),
	 -1);
    else
#endif
      connection_hooks = make_object_list(0, -1);
#if WITH_PTY_SUPPORT
    if (options->with_pty)
      ALIST_SET(supported_channel_requests,
		ATOM_PTY_REQ, make_pty_handler());
#endif /* WITH_PTY_SUPPORT */
    {
      /* FIXME: We should check that we have at least one host key.
       * We should also extract the host-key algorithms for which we have keys,
       * instead of hardcoding ssh-dss below. */
 
      struct lsh_object *o = lshd_listen
	(make_simple_listen(backend, NULL),
	 make_handshake_info(CONNECTION_SERVER,
			     "lsh - a free ssh",
			     NULL,
			     SSH_MAX_PACKET,
			     r,
			     algorithms,
			     make_simple_kexinit(
			       r,
			       make_int_list(1, ATOM_DIFFIE_HELLMAN_GROUP1_SHA1,
					     -1),
			       make_int_list(1, ATOM_SSH_DSS, -1),
			       options->super.crypto_algorithms,
			       options->super.mac_algorithms,
			       options->super.compression_algorithms,
			       make_int_list(0, -1)),
			     options->sshd1),
	 make_offer_service
	 (make_alist
	  (1, ATOM_SSH_USERAUTH,
	   lshd_services(make_userauth_service
			 (options->userauth_methods,
			  options->userauth_algorithms,
			  make_alist(1, ATOM_SSH_CONNECTION,
				     lshd_connection_service
				     (make_server_connection_service(supported_channel_requests),
				      connection_hooks),
				     -1))),
	   -1)));
    
      CAST_SUBTYPE(command, server_listen, o);
    
      COMMAND_CALL(server_listen, options,
		   &discard_continuation,
		   make_report_exception_handler
		   (make_report_exception_info(EXC_IO, EXC_IO, "lshd: "),
		    make_lshd_exception_handler(&default_exception_handler,
						HANDLER_CONTEXT),
		    HANDLER_CONTEXT));
    }
  }
  
  reaper_run(reaper, backend);

  return 0;
}