crypto/openssh-5/auth2-hostbased.c

   1 /* $OpenBSD: auth2-hostbased.c,v 1.11 2006/08/03 03:34:41 deraadt Exp $ */
   2 /*
   3  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "includes.h"
  27
  28 #include <sys/types.h>
  29
  30 #include <pwd.h>
  31 #include <string.h>
  32 #include <stdarg.h>
  33
  34 #include "xmalloc.h"
  35 #include "ssh2.h"
  36 #include "packet.h"
  37 #include "buffer.h"
  38 #include "log.h"
  39 #include "servconf.h"
  40 #include "compat.h"
  41 #include "key.h"
  42 #include "hostfile.h"
  43 #include "authfile.h"
  44 #include "auth.h"
  45 #include "canohost.h"
  46 #ifdef GSSAPI
  47 #include "ssh-gss.h"
  48 #endif
  49 #include "monitor_wrap.h"
  50 #include "pathnames.h"
  51
  52 /* import */
  53 extern ServerOptions options;
  54 extern u_char *session_id2;
  55 extern u_int session_id2_len;
  56
  57 static int
  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->valid) {
  69                 debug2("userauth_hostbased: disabled because of invalid user");
  70                 return 0;
  71         }
  72         pkalg = packet_get_string(&alen);
  73         pkblob = packet_get_string(&blen);
  74         chost = packet_get_string(NULL);
  75         cuser = packet_get_string(NULL);
  76         sig = packet_get_string(&slen);
  77
  78         debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
  79             cuser, chost, pkalg, slen);
  80 #ifdef DEBUG_PK
  81         debug("signature:");
  82         buffer_init(&b);
  83         buffer_append(&b, sig, slen);
  84         buffer_dump(&b);
  85         buffer_free(&b);
  86 #endif
  87         pktype = key_type_from_name(pkalg);
  88         if (pktype == KEY_UNSPEC) {
  89                 /* this is perfectly legal */
  90                 logit("userauth_hostbased: unsupported "
  91                     "public key algorithm: %s", pkalg);
  92                 goto done;
  93         }
  94         key = key_from_blob(pkblob, blen);
  95         if (key == NULL) {
  96                 error("userauth_hostbased: cannot decode key: %s", pkalg);
  97                 goto done;
  98         }
  99         if (key->type != pktype) {
 100                 error("userauth_hostbased: type mismatch for decoded key "
 101                     "(received %d, expected %d)", key->type, pktype);
 102                 goto done;
 103         }
 104         service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
 105             authctxt->service;
 106         buffer_init(&b);
 107         buffer_put_string(&b, session_id2, session_id2_len);
 108         /* reconstruct packet */
 109         buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 110         buffer_put_cstring(&b, authctxt->user);
 111         buffer_put_cstring(&b, service);
 112         buffer_put_cstring(&b, "hostbased");
 113         buffer_put_string(&b, pkalg, alen);
 114         buffer_put_string(&b, pkblob, blen);
 115         buffer_put_cstring(&b, chost);
 116         buffer_put_cstring(&b, cuser);
 117 #ifdef DEBUG_PK
 118         buffer_dump(&b);
 119 #endif
 120         /* test for allowed key and correct signature */
 121         authenticated = 0;
 122         if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
 123             PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
 124                         buffer_len(&b))) == 1)
 125                 authenticated = 1;
 126
 127         buffer_free(&b);
 128 done:
 129         debug2("userauth_hostbased: authenticated %d", authenticated);
 130         if (key != NULL)
 131                 key_free(key);
 132         xfree(pkalg);
 133         xfree(pkblob);
 134         xfree(cuser);
 135         xfree(chost);
 136         xfree(sig);
 137         return authenticated;
 138 }
 139
 140 /* return 1 if given hostkey is allowed */
 141 int
 142 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
 143     Key *key)
 144 {
 145         char *fp;
 146         const char *resolvedname, *ipaddr, *lookup;
 147         HostStatus host_status;
 148         int len;
 149
 150         if (blacklisted_key(key)) {
 151                 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 152                 if (options.permit_blacklisted_keys)
 153                         logit("Public key %s blacklisted (see "
 154                             "ssh-vulnkey(1)); continuing anyway", fp);
 155                 else
 156                         logit("Public key %s blacklisted (see "
 157                             "ssh-vulnkey(1))", fp);
 158                 xfree(fp);
 159                 if (!options.permit_blacklisted_keys)
 160                         return 0;
 161         }
 162
 163         resolvedname = get_canonical_hostname(options.use_dns);
 164         ipaddr = get_remote_ipaddr();
 165
 166         debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
 167             chost, resolvedname, ipaddr);
 168
 169         if (options.hostbased_uses_name_from_packet_only) {
 170                 if (auth_rhosts2(pw, cuser, chost, chost) == 0)
 171                         return 0;
 172                 lookup = chost;
 173         } else {
 174                 if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
 175                         debug2("stripping trailing dot from chost %s", chost);
 176                         chost[len - 1] = '\0';
 177                 }
 178                 if (strcasecmp(resolvedname, chost) != 0)
 179                         logit("userauth_hostbased mismatch: "
 180                             "client sends %s, but we resolve %s to %s",
 181                             chost, ipaddr, resolvedname);
 182                 if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
 183                         return 0;
 184                 lookup = resolvedname;
 185         }
 186         debug2("userauth_hostbased: access allowed by auth_rhosts2");
 187
 188         host_status = check_key_in_hostfiles(pw, key, lookup,
 189             _PATH_SSH_SYSTEM_HOSTFILE,
 190             options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);
 191
 192         /* backward compat if no key has been found. */
 193         if (host_status == HOST_NEW)
 194                 host_status = check_key_in_hostfiles(pw, key, lookup,
 195                     _PATH_SSH_SYSTEM_HOSTFILE2,
 196                     options.ignore_user_known_hosts ? NULL :
 197                     _PATH_SSH_USER_HOSTFILE2);
 198
 199         return (host_status == HOST_OK);
 200 }
 201
 202 Authmethod method_hostbased = {
 203         "hostbased",
 204         userauth_hostbased,
 205         &options.hostbased_authentication
 206 };