1 /*
   2  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  23  */
  24 /*
  25  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28 
  29 #include "includes.h"
  30 RCSID("$OpenBSD: auth2-hostbased.c,v 1.2 2002/05/31 11:35:15 markus Exp $");
  31 
  32 #pragma ident   "%Z%%M% %I%     %E% SMI"
  33 
  34 #include "ssh2.h"
  35 #include "xmalloc.h"
  36 #include "packet.h"
  37 #include "buffer.h"
  38 #include "log.h"
  39 #include "servconf.h"
  40 #include "compat.h"
  41 #include "bufaux.h"
  42 #include "auth.h"
  43 
  44 #ifdef USE_PAM
  45 #include "auth-pam.h"
  46 #endif /* USE_PAM */
  47 
  48 #include "key.h"
  49 #include "canohost.h"
  50 #include "pathnames.h"
  51 
  52 /* import */
  53 extern ServerOptions options;
  54 extern u_char *session_id2;
  55 extern int session_id2_len;
  56 
  57 static void
  58 userauth_hostbased(Authctxt *authctxt)
  59 {
  60         Buffer b;
  61         Key *key = NULL;
  62         char *pkalg, *cuser, *chost, *service;
  63         u_char *pkblob, *sig;
  64         u_int alen, blen, slen;
  65         int pktype;
  66         int authenticated = 0;
  67 
  68         if (!authctxt || !authctxt->method)
  69                 fatal("%s: missing context", __func__);
  70 
  71         pkalg = packet_get_string(&alen);
  72         pkblob = packet_get_string(&blen);
  73         chost = packet_get_string(NULL);
  74         cuser = packet_get_string(NULL);
  75         sig = packet_get_string(&slen);
  76 
  77         debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
  78             cuser, chost, pkalg, slen);
  79 #ifdef DEBUG_PK
  80         debug("signature:");
  81         buffer_init(&b);
  82         buffer_append(&b, sig, slen);
  83         buffer_dump(&b);
  84         buffer_free(&b);
  85 #endif
  86         pktype = key_type_from_name(pkalg);
  87         if (pktype == KEY_UNSPEC) {
  88                 /* this is perfectly legal */
  89                 log("userauth_hostbased: unsupported "
  90                     "public key algorithm: %s", pkalg);
  91                 goto done;
  92         }
  93         key = key_from_blob(pkblob, blen);
  94         if (key == NULL) {
  95                 error("userauth_hostbased: cannot decode key: %s", pkalg);
  96                 goto done;
  97         }
  98         if (key->type != pktype) {
  99                 error("userauth_hostbased: type mismatch for decoded key "
 100                     "(received %d, expected %d)", key->type, pktype);
 101                 goto done;
 102         }
 103         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
 104             authctxt->service;
 105         buffer_init(&b);
 106         buffer_put_string(&b, session_id2, session_id2_len);
 107         /* reconstruct packet */
 108         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 109         buffer_put_cstring(&b, authctxt->user);
 110         buffer_put_cstring(&b, service);
 111         buffer_put_cstring(&b, "hostbased");
 112         buffer_put_string(&b, pkalg, alen);
 113         buffer_put_string(&b, pkblob, blen);
 114         buffer_put_cstring(&b, chost);
 115         buffer_put_cstring(&b, cuser);
 116 #ifdef DEBUG_PK
 117         buffer_dump(&b);
 118 #endif
 119         /* test for allowed key and correct signature */
 120         authenticated = 0;
 121         if (hostbased_key_allowed(authctxt->pw, cuser, chost, key) &&
 122             key_verify(key, sig, slen, buffer_ptr(&b), buffer_len(&b)) == 1)
 123                 authenticated = 1;
 124 
 125         buffer_clear(&b);
 126 done:
 127         /*
 128          * XXX TODO: Add config options for specifying users for whom
 129          *           this userauth is insufficient and what userauths
 130          *           may continue.
 131          *
 132          *           NOTE: do_pam_non_initial_userauth() does this for
 133          *                 users with expired passwords.
 134          */
 135 #ifdef USE_PAM
 136         if (authenticated) {
 137                 authctxt->cuser = cuser;
 138                 if (!do_pam_non_initial_userauth(authctxt))
 139                         authenticated = 0;
 140                 /* Make sure nobody else will use this pointer since we are
 141                  * going to free that string. */
 142                 authctxt->cuser = NULL;
 143         }
 144 #endif /* USE_PAM */
 145 
 146         if (authenticated)
 147                 authctxt->method->authenticated = 1;
 148 
 149         debug2("userauth_hostbased: authenticated %d", authenticated);
 150         if (key != NULL)
 151                 key_free(key);
 152         xfree(pkalg);
 153         xfree(pkblob);
 154         xfree(cuser);
 155         xfree(chost);
 156         xfree(sig);
 157         return;
 158 }
 159 
 160 /* return 1 if given hostkey is allowed */
 161 int
 162 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
 163     Key *key)
 164 {
 165         const char *resolvedname, *ipaddr, *lookup;
 166         HostStatus host_status;
 167         int len;
 168 
 169         resolvedname = get_canonical_hostname(options.verify_reverse_mapping);
 170         ipaddr = get_remote_ipaddr();
 171 
 172         debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
 173             chost, resolvedname, ipaddr);
 174 
 175         if (pw == NULL)
 176                 return 0;
 177 
 178         if (options.hostbased_uses_name_from_packet_only) {
 179                 if (auth_rhosts2(pw, cuser, chost, chost) == 0)
 180                         return 0;
 181                 lookup = chost;
 182         } else {
 183                 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
 184                         debug2("stripping trailing dot from chost %s", chost);
 185                         chost[len - 1] = '\0';
 186                 }
 187                 if (strcasecmp(resolvedname, chost) != 0)
 188                         log("userauth_hostbased mismatch: "
 189                             "client sends %s, but we resolve %s to %s",
 190                             chost, ipaddr, resolvedname);
 191                 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
 192                         return 0;
 193                 lookup = resolvedname;
 194         }
 195         debug2("userauth_hostbased: access allowed by auth_rhosts2");
 196 
 197         host_status = check_key_in_hostfiles(pw, key, lookup,
 198             _PATH_SSH_SYSTEM_HOSTFILE,
 199             options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
 200 
 201         /* backward compat if no key has been found. */
 202         if (host_status == HOST_NEW)
 203                 host_status = check_key_in_hostfiles(pw, key, lookup,
 204                     _PATH_SSH_SYSTEM_HOSTFILE2,
 205                     options.ignore_user_known_hosts ? NULL :
 206                     _PATH_SSH_USER_HOSTFILE2);
 207 
 208         return (host_status == HOST_OK);
 209 }
 210 
 211 Authmethod method_hostbased = {
 212         "hostbased",
 213         &options.hostbased_authentication,
 214         userauth_hostbased,
 215         NULL,               /* no abandon function */
 216         NULL, NULL,         /* method data and hist data */
 217         0,                  /* is not initial userauth */
 218         0, 0, 0,            /* counters */
 219         0, 0, 0, 0, 0, 0    /* state */
 220 };