text: /* $OpenBSD: auth2-hostbased.c,v 1.14 2010/08/04 05:42:47 djm Exp $ */
  /*
   * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   *
   * 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"
  
  #include <sys/types.h>
  
  #include <pwd.h>
  #include <string.h>
  #include <stdarg.h>
  
  #include "xmalloc.h"
  #include "ssh2.h"
  #include "packet.h"
  #include "buffer.h"
  #include "log.h"
  #include "servconf.h"
  #include "compat.h"
  #include "key.h"
  #include "hostfile.h"
  #include "auth.h"
  #include "canohost.h"
  #ifdef GSSAPI
  #include "ssh-gss.h"
  #endif
  #include "monitor_wrap.h"
  #include "pathnames.h"
  
  /* import */
  extern ServerOptions options;
  extern u_char *session_id2;
  extern u_int session_id2_len;
  
  static int
  userauth_hostbased(Authctxt *authctxt)
  {
  	Buffer b;
  	Key *key = NULL;
  	char *pkalg, *cuser, *chost, *service;
  	u_char *pkblob, *sig;
  	u_int alen, blen, slen;
  	int pktype;
  	int authenticated = 0;
  
  	if (!authctxt->valid) {
  		debug2("userauth_hostbased: disabled because of invalid user");
  		return 0;
  	}
  	pkalg = packet_get_string(&alen);
  	pkblob = packet_get_string(&blen);
  	chost = packet_get_string(NULL);
  	cuser = packet_get_string(NULL);
  	sig = packet_get_string(&slen);
  
  	debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
  	    cuser, chost, pkalg, slen);
  #ifdef DEBUG_PK
  	debug("signature:");
  	buffer_init(&b);
  	buffer_append(&b, sig, slen);
  	buffer_dump(&b);
  	buffer_free(&b);
  #endif
  	pktype = key_type_from_name(pkalg);
  	if (pktype == KEY_UNSPEC) {
  		/* this is perfectly legal */
  		logit("userauth_hostbased: unsupported "
  		    "public key algorithm: %s", pkalg);
  		goto done;
  	}
  	key = key_from_blob(pkblob, blen);
  	if (key == NULL) {
  		error("userauth_hostbased: cannot decode key: %s", pkalg);
  		goto done;
  	}
  	if (key->type != pktype) {
  		error("userauth_hostbased: type mismatch for decoded key "
  		    "(received %d, expected %d)", key->type, pktype);
  		goto done;
  	}
  	service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
  	    authctxt->service;
  	buffer_init(&b);
  	buffer_put_string(&b, session_id2, session_id2_len);
  	/* reconstruct packet */
  	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
  	buffer_put_cstring(&b, authctxt->user);
  	buffer_put_cstring(&b, service);
  	buffer_put_cstring(&b, "hostbased");
  	buffer_put_string(&b, pkalg, alen);
  	buffer_put_string(&b, pkblob, blen);
  	buffer_put_cstring(&b, chost);
  	buffer_put_cstring(&b, cuser);
  #ifdef DEBUG_PK
  	buffer_dump(&b);
  #endif
  	/* test for allowed key and correct signature */
  	authenticated = 0;
  	if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
  	    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
  			buffer_len(&b))) == 1)
  		authenticated = 1;
  
  	buffer_free(&b);
  done:
  	debug2("userauth_hostbased: authenticated %d", authenticated);
  	if (key != NULL)
  		key_free(key);
  	xfree(pkalg);
  	xfree(pkblob);
  	xfree(cuser);
  	xfree(chost);
  	xfree(sig);
  	return authenticated;
  }
  
  /* return 1 if given hostkey is allowed */
  int
  hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
      Key *key)
  {
  	const char *resolvedname, *ipaddr, *lookup, *reason;
  	HostStatus host_status;
  	int len;
  	char *fp;
  
  	if (auth_key_is_revoked(key))
  		return 0;
  
  	resolvedname = get_canonical_hostname(options.use_dns);
  	ipaddr = get_remote_ipaddr();
  
  	debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
  	    chost, resolvedname, ipaddr);
  
  	if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
  		debug2("stripping trailing dot from chost %s", chost);
  		chost[len - 1] = '\0';
  	}
  
  	if (options.hostbased_uses_name_from_packet_only) {
  		if (auth_rhosts2(pw, cuser, chost, chost) == 0)
  			return 0;
  		lookup = chost;
  	} else {
  		if (strcasecmp(resolvedname, chost) != 0)
  			logit("userauth_hostbased mismatch: "
  			    "client sends %s, but we resolve %s to %s",
  			    chost, ipaddr, resolvedname);
  		if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
  			return 0;
  		lookup = resolvedname;
  	}
  	debug2("userauth_hostbased: access allowed by auth_rhosts2");
  
  	if (key_is_cert(key) && 
  	    key_cert_check_authority(key, 1, 0, lookup, &reason)) {
  		error("%s", reason);
  		auth_debug_add("%s", reason);
  		return 0;
  	}
  
  	host_status = check_key_in_hostfiles(pw, key, lookup,
  	    _PATH_SSH_SYSTEM_HOSTFILE,
  	    options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
  
  	/* backward compat if no key has been found. */
  	if (host_status == HOST_NEW) {
  		host_status = check_key_in_hostfiles(pw, key, lookup,
  		    _PATH_SSH_SYSTEM_HOSTFILE2,
  		    options.ignore_user_known_hosts ? NULL :
  		    _PATH_SSH_USER_HOSTFILE2);
  	}
  
  	if (host_status == HOST_OK) {
  		if (key_is_cert(key)) {
  			fp = key_fingerprint(key->cert->signature_key,
  			    SSH_FP_MD5, SSH_FP_HEX);
  			verbose("Accepted certificate ID \"%s\" signed by "
  			    "%s CA %s from %s@%s", key->cert->key_id,
  			    key_type(key->cert->signature_key), fp,
  			    cuser, lookup);
  		} else {
  			fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
  			verbose("Accepted %s public key %s from %s@%s",
  			    key_type(key), fp, cuser, lookup);
  		}
  		xfree(fp);
  	}
  
  	return (host_status == HOST_OK);
  }
  
  Authmethod method_hostbased = {
  	"hostbased",
  	userauth_hostbased,
  	&options.hostbased_authentication
  };
  