auth-krb4.c

   1 /*
   2  * Copyright (c) 1999 Dug Song.  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 #include "includes.h"
  26 #include "packet.h"
  27 #include "xmalloc.h"
  28 #include "ssh.h"
  29 #include "servconf.h"
  30
  31 RCSID("$OpenBSD: auth-krb4.c,v 1.18 2000/09/07 20:27:49 deraadt Exp $");
  32
  33 #ifdef KRB4
  34 char *ticket = NULL;
  35
  36 extern ServerOptions options;
  37
  38 /*
  39  * try krb4 authentication,
  40  * return 1 on success, 0 on failure, -1 if krb4 is not available
  41  */
  42
  43 int
  44 auth_krb4_password(struct passwd * pw, const char *password)
  45 {
  46         AUTH_DAT adata;
  47         KTEXT_ST tkt;
  48         struct hostent *hp;
  49         unsigned long faddr;
  50         char localhost[MAXHOSTNAMELEN];
  51         char phost[INST_SZ];
  52         char realm[REALM_SZ];
  53         int r;
  54
  55         /*
  56          * Try Kerberos password authentication only for non-root
  57          * users and only if Kerberos is installed.
  58          */
  59         if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
  60
  61                 /* Set up our ticket file. */
  62                 if (!krb4_init(pw->pw_uid)) {
  63                         log("Couldn't initialize Kerberos ticket file for %s!",
  64                             pw->pw_name);
  65                         goto kerberos_auth_failure;
  66                 }
  67                 /* Try to get TGT using our password. */
  68                 r = krb_get_pw_in_tkt((char *) pw->pw_name, "",
  69                     realm, "krbtgt", realm,
  70                     DEFAULT_TKT_LIFE, (char *) password);
  71                 if (r != INTK_OK) {
  72                         packet_send_debug("Kerberos V4 password "
  73                             "authentication for %s failed: %s",
  74                             pw->pw_name, krb_err_txt[r]);
  75                         goto kerberos_auth_failure;
  76                 }
  77                 /* Successful authentication. */
  78                 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
  79
  80                 /*
  81                  * Now that we have a TGT, try to get a local
  82                  * "rcmd" ticket to ensure that we are not talking
  83                  * to a bogus Kerberos server.
  84                  */
  85                 (void) gethostname(localhost, sizeof(localhost));
  86                 (void) strlcpy(phost, (char *) krb_get_phost(localhost),
  87                     INST_SZ);
  88                 r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
  89
  90                 if (r == KSUCCESS) {
  91                         if (!(hp = gethostbyname(localhost))) {
  92                                 log("Couldn't get local host address!");
  93                                 goto kerberos_auth_failure;
  94                         }
  95                         memmove((void *) &faddr, (void *) hp->h_addr,
  96                             sizeof(faddr));
  97
  98                         /* Verify our "rcmd" ticket. */
  99                         r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
 100                             faddr, &adata, "");
 101                         if (r == RD_AP_UNDEC) {
 102                                 /*
 103                                  * Probably didn't have a srvtab on
 104                                  * localhost. Disallow login.
 105                                  */
 106                                 log("Kerberos V4 TGT for %s unverifiable, "
 107                                     "no srvtab installed? krb_rd_req: %s",
 108                                     pw->pw_name, krb_err_txt[r]);
 109                                 goto kerberos_auth_failure;
 110                         } else if (r != KSUCCESS) {
 111                                 log("Kerberos V4 %s ticket unverifiable: %s",
 112                                     KRB4_SERVICE_NAME, krb_err_txt[r]);
 113                                 goto kerberos_auth_failure;
 114                         }
 115                 } else if (r == KDC_PR_UNKNOWN) {
 116                         /*
 117                          * Disallow login if no rcmd service exists, and
 118                          * log the error.
 119                          */
 120                         log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
 121                             "not registered, or srvtab is wrong?", pw->pw_name,
 122                         krb_err_txt[r], KRB4_SERVICE_NAME, phost);
 123                         goto kerberos_auth_failure;
 124                 } else {
 125                         /*
 126                          * TGT is bad, forget it. Possibly spoofed!
 127                          */
 128                         packet_send_debug("WARNING: Kerberos V4 TGT "
 129                             "possibly spoofed for %s: %s",
 130                             pw->pw_name, krb_err_txt[r]);
 131                         goto kerberos_auth_failure;
 132                 }
 133
 134                 /* Authentication succeeded. */
 135                 return 1;
 136
 137 kerberos_auth_failure:
 138                 krb4_cleanup_proc(NULL);
 139
 140                 if (!options.kerberos_or_local_passwd)
 141                         return 0;
 142         } else {
 143                 /* Logging in as root or no local Kerberos realm. */
 144                 packet_send_debug("Unable to authenticate to Kerberos.");
 145         }
 146         /* Fall back to ordinary passwd authentication. */
 147         return -1;
 148 }
 149
 150 void
 151 krb4_cleanup_proc(void *ignore)
 152 {
 153         debug("krb4_cleanup_proc called");
 154         if (ticket) {
 155                 (void) dest_tkt();
 156                 xfree(ticket);
 157                 ticket = NULL;
 158         }
 159 }
 160
 161 int
 162 krb4_init(uid_t uid)
 163 {
 164         static int cleanup_registered = 0;
 165         const char *tkt_root = TKT_ROOT;
 166         struct stat st;
 167         int fd;
 168
 169         if (!ticket) {
 170                 /* Set unique ticket string manually since we're still root. */
 171                 ticket = xmalloc(MAXPATHLEN);
 172 #ifdef AFS
 173                 if (lstat("/ticket", &st) != -1)
 174                         tkt_root = "/ticket/";
 175 #endif /* AFS */
 176                 snprintf(ticket, MAXPATHLEN, "%s%u_%d", tkt_root, uid, getpid());
 177                 (void) krb_set_tkt_string(ticket);
 178         }
 179         /* Register ticket cleanup in case of fatal error. */
 180         if (!cleanup_registered) {
 181                 fatal_add_cleanup(krb4_cleanup_proc, NULL);
 182                 cleanup_registered = 1;
 183         }
 184         /* Try to create our ticket file. */
 185         if ((fd = mkstemp(ticket)) != -1) {
 186                 close(fd);
 187                 return 1;
 188         }
 189         /* Ticket file exists - make sure user owns it (just passed ticket). */
 190         if (lstat(ticket, &st) != -1) {
 191                 if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
 192                     st.st_uid == uid)
 193                         return 1;
 194         }
 195         /* Failure - cancel cleanup function, leaving bad ticket for inspection. */
 196         log("WARNING: bad ticket file %s", ticket);
 197         fatal_remove_cleanup(krb4_cleanup_proc, NULL);
 198         cleanup_registered = 0;
 199         xfree(ticket);
 200         ticket = NULL;
 201
 202         return 0;
 203 }
 204
 205 int
 206 auth_krb4(const char *server_user, KTEXT auth, char **client)
 207 {
 208         AUTH_DAT adat = {0};
 209         KTEXT_ST reply;
 210         char instance[INST_SZ];
 211         int r, s;
 212         socklen_t slen;
 213         u_int cksum;
 214         Key_schedule schedule;
 215         struct sockaddr_in local, foreign;
 216
 217         s = packet_get_connection_in();
 218
 219         slen = sizeof(local);
 220         memset(&local, 0, sizeof(local));
 221         if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
 222                 debug("getsockname failed: %.100s", strerror(errno));
 223         slen = sizeof(foreign);
 224         memset(&foreign, 0, sizeof(foreign));
 225         if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
 226                 debug("getpeername failed: %.100s", strerror(errno));
 227                 fatal_cleanup();
 228         }
 229         instance[0] = '*';
 230         instance[1] = 0;
 231
 232         /* Get the encrypted request, challenge, and session key. */
 233         if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, ""))) {
 234                 packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
 235                 return 0;
 236         }
 237         des_key_sched((des_cblock *) adat.session, schedule);
 238
 239         *client = xmalloc(MAX_K_NAME_SZ);
 240         (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
 241             *adat.pinst ? "." : "", adat.pinst, adat.prealm);
 242
 243         /* Check ~/.klogin authorization now. */
 244         if (kuserok(&adat, (char *) server_user) != KSUCCESS) {
 245                 packet_send_debug("Kerberos V4 .klogin authorization failed!");
 246                 log("Kerberos V4 .klogin authorization failed for %s to account %s",
 247                     *client, server_user);
 248                 xfree(*client);
 249                 return 0;
 250         }
 251         /* Increment the checksum, and return it encrypted with the
 252            session key. */
 253         cksum = adat.checksum + 1;
 254         cksum = htonl(cksum);
 255
 256         /* If we can't successfully encrypt the checksum, we send back an
 257            empty message, admitting our failure. */
 258         if ((r = krb_mk_priv((u_char *) & cksum, reply.dat, sizeof(cksum) + 1,
 259             schedule, &adat.session, &local, &foreign)) < 0) {
 260                 packet_send_debug("Kerberos V4 mk_priv: (%d) %s", r, krb_err_txt[r]);
 261                 reply.dat[0] = 0;
 262                 reply.length = 0;
 263         } else
 264                 reply.length = r;
 265
 266         /* Clear session key. */
 267         memset(&adat.session, 0, sizeof(&adat.session));
 268
 269         packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
 270         packet_put_string((char *) reply.dat, reply.length);
 271         packet_send();
 272         packet_write_wait();
 273         return 1;
 274 }
 275 #endif /* KRB4 */
 276
 277 #ifdef AFS
 278 int
 279 auth_kerberos_tgt(struct passwd *pw, const char *string)
 280 {
 281         CREDENTIALS creds;
 282
 283         if (!radix_to_creds(string, &creds)) {
 284                 log("Protocol error decoding Kerberos V4 tgt");
 285                 packet_send_debug("Protocol error decoding Kerberos V4 tgt");
 286                 goto auth_kerberos_tgt_failure;
 287         }
 288         if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
 289                 strlcpy(creds.service, "krbtgt", sizeof creds.service);
 290
 291         if (strcmp(creds.service, "krbtgt")) {
 292                 log("Kerberos V4 tgt (%s%s%s@%s) rejected for %s", creds.pname,
 293                     creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
 294                     pw->pw_name);
 295                 packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
 296                     creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
 297                     creds.realm, pw->pw_name);
 298                 goto auth_kerberos_tgt_failure;
 299         }
 300         if (!krb4_init(pw->pw_uid))
 301                 goto auth_kerberos_tgt_failure;
 302
 303         if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
 304                 goto auth_kerberos_tgt_failure;
 305
 306         if (save_credentials(creds.service, creds.instance, creds.realm,
 307             creds.session, creds.lifetime, creds.kvno,
 308             &creds.ticket_st, creds.issue_date) != KSUCCESS) {
 309                 packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
 310                 goto auth_kerberos_tgt_failure;
 311         }
 312         /* Successful authentication, passed all checks. */
 313         chown(tkt_string(), pw->pw_uid, pw->pw_gid);
 314
 315         packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
 316             creds.service, creds.instance, creds.realm, creds.pname,
 317             creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
 318         memset(&creds, 0, sizeof(creds));
 319         packet_start(SSH_SMSG_SUCCESS);
 320         packet_send();
 321         packet_write_wait();
 322         return 1;
 323
 324 auth_kerberos_tgt_failure:
 325         krb4_cleanup_proc(NULL);
 326         memset(&creds, 0, sizeof(creds));
 327         packet_start(SSH_SMSG_FAILURE);
 328         packet_send();
 329         packet_write_wait();
 330         return 0;
 331 }
 332
 333 int
 334 auth_afs_token(struct passwd *pw, const char *token_string)
 335 {
 336         CREDENTIALS creds;
 337         uid_t uid = pw->pw_uid;
 338
 339         if (!radix_to_creds(token_string, &creds)) {
 340                 log("Protocol error decoding AFS token");
 341                 packet_send_debug("Protocol error decoding AFS token");
 342                 packet_start(SSH_SMSG_FAILURE);
 343                 packet_send();
 344                 packet_write_wait();
 345                 return 0;
 346         }
 347         if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
 348                 strlcpy(creds.service, "afs", sizeof creds.service);
 349
 350         if (strncmp(creds.pname, "AFS ID ", 7) == 0)
 351                 uid = atoi(creds.pname + 7);
 352
 353         if (kafs_settoken(creds.realm, uid, &creds)) {
 354                 log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
 355                     pw->pw_name);
 356                 packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
 357                     creds.realm, pw->pw_name);
 358                 memset(&creds, 0, sizeof(creds));
 359                 packet_start(SSH_SMSG_FAILURE);
 360                 packet_send();
 361                 packet_write_wait();
 362                 return 0;
 363         }
 364         packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
 365             creds.realm, creds.pname, creds.realm);
 366         memset(&creds, 0, sizeof(creds));
 367         packet_start(SSH_SMSG_SUCCESS);
 368         packet_send();
 369         packet_write_wait();
 370         return 1;
 371 }
 372 #endif /* AFS */