crypto/external/bsd/openssh/dist/auth2-pubkey.c

   1 /*      $NetBSD$        */
   2 /* $OpenBSD: auth2-pubkey.c,v 1.19 2008/07/03 21:46:58 otto Exp $ */
   3 /*
   4  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28 __RCSID("$NetBSD: auth2-pubkey.c,v 1.7 2009/02/16 20:53:54 christos Exp $");
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31
  32 #include <fcntl.h>
  33 #include <pwd.h>
  34 #include <stdio.h>
  35 #include <stdarg.h>
  36 #include <unistd.h>
  37
  38 #include "xmalloc.h"
  39 #include "ssh.h"
  40 #include "ssh2.h"
  41 #include "packet.h"
  42 #include "buffer.h"
  43 #include "log.h"
  44 #include "servconf.h"
  45 #include "compat.h"
  46 #include "key.h"
  47 #include "hostfile.h"
  48 #include "auth.h"
  49 #include "pathnames.h"
  50 #include "uidswap.h"
  51 #include "auth-options.h"
  52 #include "canohost.h"
  53 #ifdef GSSAPI
  54 #include "ssh-gss.h"
  55 #endif
  56 #include "monitor_wrap.h"
  57 #include "misc.h"
  58
  59 /* import */
  60 extern ServerOptions options;
  61 extern u_char *session_id2;
  62 extern u_int session_id2_len;
  63
  64 static int
  65 userauth_pubkey(Authctxt *authctxt)
  66 {
  67         Buffer b;
  68         Key *key = NULL;
  69         char *pkalg;
  70         u_char *pkblob, *sig;
  71         u_int alen, blen, slen;
  72         int have_sig, pktype;
  73         int authenticated = 0;
  74
  75         if (!authctxt->valid) {
  76                 debug2("userauth_pubkey: disabled because of invalid user");
  77                 return 0;
  78         }
  79         have_sig = packet_get_char();
  80         if (datafellows & SSH_BUG_PKAUTH) {
  81                 debug2("userauth_pubkey: SSH_BUG_PKAUTH");
  82                 /* no explicit pkalg given */
  83                 pkblob = packet_get_string(&blen);
  84                 buffer_init(&b);
  85                 buffer_append(&b, pkblob, blen);
  86                 /* so we have to extract the pkalg from the pkblob */
  87                 pkalg = buffer_get_string(&b, &alen);
  88                 buffer_free(&b);
  89         } else {
  90                 pkalg = packet_get_string(&alen);
  91                 pkblob = packet_get_string(&blen);
  92         }
  93         pktype = key_type_from_name(pkalg);
  94         if (pktype == KEY_UNSPEC) {
  95                 /* this is perfectly legal */
  96                 logit("userauth_pubkey: unsupported public key algorithm: %s",
  97                     pkalg);
  98                 goto done;
  99         }
 100         key = key_from_blob(pkblob, blen);
 101         if (key == NULL) {
 102                 error("userauth_pubkey: cannot decode key: %s", pkalg);
 103                 goto done;
 104         }
 105         if (key->type != pktype) {
 106                 error("userauth_pubkey: type mismatch for decoded key "
 107                     "(received %d, expected %d)", key->type, pktype);
 108                 goto done;
 109         }
 110         if (have_sig) {
 111                 sig = packet_get_string(&slen);
 112                 packet_check_eom();
 113                 buffer_init(&b);
 114                 if (datafellows & SSH_OLD_SESSIONID) {
 115                         buffer_append(&b, session_id2, session_id2_len);
 116                 } else {
 117                         buffer_put_string(&b, session_id2, session_id2_len);
 118                 }
 119                 /* reconstruct packet */
 120                 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 121                 buffer_put_cstring(&b, authctxt->user);
 122                 buffer_put_cstring(&b,
 123                     datafellows & SSH_BUG_PKSERVICE ?
 124                     "ssh-userauth" :
 125                     authctxt->service);
 126                 if (datafellows & SSH_BUG_PKAUTH) {
 127                         buffer_put_char(&b, have_sig);
 128                 } else {
 129                         buffer_put_cstring(&b, "publickey");
 130                         buffer_put_char(&b, have_sig);
 131                         buffer_put_cstring(&b, pkalg);
 132                 }
 133                 buffer_put_string(&b, pkblob, blen);
 134 #ifdef DEBUG_PK
 135                 buffer_dump(&b);
 136 #endif
 137                 /* test for correct signature */
 138                 authenticated = 0;
 139                 if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
 140                     PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
 141                     buffer_len(&b))) == 1)
 142                         authenticated = 1;
 143                 buffer_free(&b);
 144                 xfree(sig);
 145         } else {
 146                 debug("test whether pkalg/pkblob are acceptable");
 147                 packet_check_eom();
 148
 149                 /* XXX fake reply and always send PK_OK ? */
 150                 /*
 151                  * XXX this allows testing whether a user is allowed
 152                  * to login: if you happen to have a valid pubkey this
 153                  * message is sent. the message is NEVER sent at all
 154                  * if a user is not allowed to login. is this an
 155                  * issue? -markus
 156                  */
 157                 if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
 158                         packet_start(SSH2_MSG_USERAUTH_PK_OK);
 159                         packet_put_string(pkalg, alen);
 160                         packet_put_string(pkblob, blen);
 161                         packet_send();
 162                         packet_write_wait();
 163                         authctxt->postponed = 1;
 164                 }
 165         }
 166         if (authenticated != 1)
 167                 auth_clear_options();
 168 done:
 169         debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
 170         if (key != NULL)
 171                 key_free(key);
 172         xfree(pkalg);
 173         xfree(pkblob);
 174         return authenticated;
 175 }
 176
 177 /* return 1 if user allows given key */
 178 static int
 179 user_key_allowed2(struct passwd *pw, Key *key, char *file)
 180 {
 181         char line[SSH_MAX_PUBKEY_BYTES];
 182         int found_key = 0;
 183         FILE *f;
 184         u_long linenum = 0;
 185         Key *found;
 186         char *fp;
 187
 188         /* Temporarily use the user's uid. */
 189         temporarily_use_uid(pw);
 190
 191         debug("trying public key file %s", file);
 192         f = auth_openkeyfile(file, pw, options.strict_modes);
 193
 194         if (!f) {
 195                 restore_uid();
 196                 return 0;
 197         }
 198
 199         found_key = 0;
 200         found = key_new(key->type);
 201
 202         while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
 203                 char *cp, *key_options = NULL;
 204
 205                 /* Skip leading whitespace, empty and comment lines. */
 206                 for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 207                         ;
 208                 if (!*cp || *cp == '\n' || *cp == '#')
 209                         continue;
 210
 211                 if (key_read(found, &cp) != 1) {
 212                         /* no key?  check if there are options for this key */
 213                         int quoted = 0;
 214                         debug2("user_key_allowed: check options: '%s'", cp);
 215                         key_options = cp;
 216                         for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
 217                                 if (*cp == '\\' && cp[1] == '"')
 218                                         cp++;   /* Skip both */
 219                                 else if (*cp == '"')
 220                                         quoted = !quoted;
 221                         }
 222                         /* Skip remaining whitespace. */
 223                         for (; *cp == ' ' || *cp == '\t'; cp++)
 224                                 ;
 225                         if (key_read(found, &cp) != 1) {
 226                                 debug2("user_key_allowed: advance: '%s'", cp);
 227                                 /* still no key?  advance to next line*/
 228                                 continue;
 229                         }
 230                 }
 231                 if (key_equal(found, key) &&
 232                     auth_parse_options(pw, key_options, file, linenum) == 1) {
 233                         found_key = 1;
 234                         debug("matching key found: file %s, line %lu",
 235                             file, linenum);
 236                         fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
 237                         verbose("Found matching %s key: %s",
 238                             key_type(found), fp);
 239                         xfree(fp);
 240                         break;
 241                 }
 242         }
 243         restore_uid();
 244         fclose(f);
 245         key_free(found);
 246         if (!found_key)
 247                 debug2("key not found");
 248         return found_key;
 249 }
 250
 251 /* check whether given key is in .ssh/authorized_keys* */
 252 int
 253 user_key_allowed(struct passwd *pw, Key *key)
 254 {
 255         int success;
 256         char *file;
 257
 258         file = authorized_keys_file(pw);
 259         success = user_key_allowed2(pw, key, file);
 260         xfree(file);
 261         if (success)
 262                 return success;
 263
 264         /* try suffix "2" for backward compat, too */
 265         file = authorized_keys_file2(pw);
 266         success = user_key_allowed2(pw, key, file);
 267         xfree(file);
 268         return success;
 269 }
 270
 271 Authmethod method_pubkey = {
 272         "publickey",
 273         userauth_pubkey,
 274         &options.pubkey_authentication
 275 };