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 RCSID("$OpenBSD: auth-krb4.c,v 1.22 2001/01/21 19:05:41 markus Exp $");
  27
  28 #ifdef KRB4
  29 #include "ssh.h"
  30 #include "ssh1.h"
  31 #include "packet.h"
  32 #include "xmalloc.h"
  33 #include "log.h"
  34 #include "servconf.h"
  35 #include "auth.h"
  36 #include "radix.h"
  37
  38 char *ticket = NULL;
  39
  40 extern ServerOptions options;
  41
  42 /*
  43  * try krb4 authentication,
  44  * return 1 on success, 0 on failure, -1 if krb4 is not available
  45  */
  46
  47 int
  48 auth_krb4_password(struct passwd * pw, const char *password)
  49 {
  50         AUTH_DAT adata;
  51         KTEXT_ST tkt;
  52         struct hostent *hp;
  53         u_long faddr;
  54         char localhost[MAXHOSTNAMELEN];
  55         char phost[INST_SZ];
  56         char realm[REALM_SZ];
  57         int r;
  58
  59         /*
  60          * Try Kerberos password authentication only for non-root
  61          * users and only if Kerberos is installed.
  62          */
  63         if (pw->pw_uid != 0 && krb_get_lrealm(realm, 1) == KSUCCESS) {
  64
  65                 /* Set up our ticket file. */
  66                 if (!krb4_init(pw->pw_uid)) {
  67                         log("Couldn't initialize Kerberos ticket file for %s!",
  68                             pw->pw_name);
  69                         goto kerberos_auth_failure;
  70                 }
  71                 /* Try to get TGT using our password. */
  72                 r = krb_get_pw_in_tkt((char *) pw->pw_name, "",
  73                     realm, "krbtgt", realm,
  74                     DEFAULT_TKT_LIFE, (char *) password);
  75                 if (r != INTK_OK) {
  76                         packet_send_debug("Kerberos V4 password "
  77                             "authentication for %s failed: %s",
  78                             pw->pw_name, krb_err_txt[r]);
  79                         goto kerberos_auth_failure;
  80                 }
  81                 /* Successful authentication. */
  82                 chown(tkt_string(), pw->pw_uid, pw->pw_gid);
  83
  84                 /*
  85                  * Now that we have a TGT, try to get a local
  86                  * "rcmd" ticket to ensure that we are not talking
  87                  * to a bogus Kerberos server.
  88                  */
  89                 (void) gethostname(localhost, sizeof(localhost));
  90                 (void) strlcpy(phost, (char *) krb_get_phost(localhost),
  91                     INST_SZ);
  92                 r = krb_mk_req(&tkt, KRB4_SERVICE_NAME, phost, realm, 33);
  93
  94                 if (r == KSUCCESS) {
  95                         if (!(hp = gethostbyname(localhost))) {
  96                                 log("Couldn't get local host address!");
  97                                 goto kerberos_auth_failure;
  98                         }
  99                         memmove((void *) &faddr, (void *) hp->h_addr,
 100                             sizeof(faddr));
 101
 102                         /* Verify our "rcmd" ticket. */
 103                         r = krb_rd_req(&tkt, KRB4_SERVICE_NAME, phost,
 104                             faddr, &adata, "");
 105                         if (r == RD_AP_UNDEC) {
 106                                 /*
 107                                  * Probably didn't have a srvtab on
 108                                  * localhost. Disallow login.
 109                                  */
 110                                 log("Kerberos V4 TGT for %s unverifiable, "
 111                                     "no srvtab installed? krb_rd_req: %s",
 112                                     pw->pw_name, krb_err_txt[r]);
 113                                 goto kerberos_auth_failure;
 114                         } else if (r != KSUCCESS) {
 115                                 log("Kerberos V4 %s ticket unverifiable: %s",
 116                                     KRB4_SERVICE_NAME, krb_err_txt[r]);
 117                                 goto kerberos_auth_failure;
 118                         }
 119                 } else if (r == KDC_PR_UNKNOWN) {
 120                         /*
 121                          * Disallow login if no rcmd service exists, and
 122                          * log the error.
 123                          */
 124                         log("Kerberos V4 TGT for %s unverifiable: %s; %s.%s "
 125                             "not registered, or srvtab is wrong?", pw->pw_name,
 126                         krb_err_txt[r], KRB4_SERVICE_NAME, phost);
 127                         goto kerberos_auth_failure;
 128                 } else {
 129                         /*
 130                          * TGT is bad, forget it. Possibly spoofed!
 131                          */
 132                         packet_send_debug("WARNING: Kerberos V4 TGT "
 133                             "possibly spoofed for %s: %s",
 134                             pw->pw_name, krb_err_txt[r]);
 135                         goto kerberos_auth_failure;
 136                 }
 137
 138                 /* Authentication succeeded. */
 139                 return 1;
 140
 141 kerberos_auth_failure:
 142                 krb4_cleanup_proc(NULL);
 143
 144                 if (!options.kerberos_or_local_passwd)
 145                         return 0;
 146         } else {
 147                 /* Logging in as root or no local Kerberos realm. */
 148                 packet_send_debug("Unable to authenticate to Kerberos.");
 149         }
 150         /* Fall back to ordinary passwd authentication. */
 151         return -1;
 152 }
 153
 154 void
 155 krb4_cleanup_proc(void *ignore)
 156 {
 157         debug("krb4_cleanup_proc called");
 158         if (ticket) {
 159                 (void) dest_tkt();
 160                 xfree(ticket);
 161                 ticket = NULL;
 162         }
 163 }
 164
 165 int
 166 krb4_init(uid_t uid)
 167 {
 168         static int cleanup_registered = 0;
 169         const char *tkt_root = TKT_ROOT;
 170         struct stat st;
 171         int fd;
 172
 173         if (!ticket) {
 174                 /* Set unique ticket string manually since we're still root. */
 175                 ticket = xmalloc(MAXPATHLEN);
 176 #ifdef AFS
 177                 if (lstat("/ticket", &st) != -1)
 178                         tkt_root = "/ticket/";
 179 #endif /* AFS */
 180                 snprintf(ticket, MAXPATHLEN, "%s%u_%d", tkt_root, uid, getpid());
 181                 (void) krb_set_tkt_string(ticket);
 182         }
 183         /* Register ticket cleanup in case of fatal error. */
 184         if (!cleanup_registered) {
 185                 fatal_add_cleanup(krb4_cleanup_proc, NULL);
 186                 cleanup_registered = 1;
 187         }
 188         /* Try to create our ticket file. */
 189         if ((fd = mkstemp(ticket)) != -1) {
 190                 close(fd);
 191                 return 1;
 192         }
 193         /* Ticket file exists - make sure user owns it (just passed ticket). */
 194         if (lstat(ticket, &st) != -1) {
 195                 if (st.st_mode == (S_IFREG | S_IRUSR | S_IWUSR) &&
 196                     st.st_uid == uid)
 197                         return 1;
 198         }
 199         /* Failure - cancel cleanup function, leaving bad ticket for inspection. */
 200         log("WARNING: bad ticket file %s", ticket);
 201         fatal_remove_cleanup(krb4_cleanup_proc, NULL);
 202         cleanup_registered = 0;
 203         xfree(ticket);
 204         ticket = NULL;
 205
 206         return 0;
 207 }
 208
 209 int
 210 auth_krb4(const char *server_user, KTEXT auth, char **client)
 211 {
 212         AUTH_DAT adat = {0};
 213         KTEXT_ST reply;
 214         char instance[INST_SZ];
 215         int r, s;
 216         socklen_t slen;
 217         u_int cksum;
 218         Key_schedule schedule;
 219         struct sockaddr_in local, foreign;
 220
 221         s = packet_get_connection_in();
 222
 223         slen = sizeof(local);
 224         memset(&local, 0, sizeof(local));
 225         if (getsockname(s, (struct sockaddr *) & local, &slen) < 0)
 226                 debug("getsockname failed: %.100s", strerror(errno));
 227         slen = sizeof(foreign);
 228         memset(&foreign, 0, sizeof(foreign));
 229         if (getpeername(s, (struct sockaddr *) & foreign, &slen) < 0) {
 230                 debug("getpeername failed: %.100s", strerror(errno));
 231                 fatal_cleanup();
 232         }
 233         instance[0] = '*';
 234         instance[1] = 0;
 235
 236         /* Get the encrypted request, challenge, and session key. */
 237         if ((r = krb_rd_req(auth, KRB4_SERVICE_NAME, instance, 0, &adat, ""))) {
 238                 packet_send_debug("Kerberos V4 krb_rd_req: %.100s", krb_err_txt[r]);
 239                 return 0;
 240         }
 241         des_key_sched((des_cblock *) adat.session, schedule);
 242
 243         *client = xmalloc(MAX_K_NAME_SZ);
 244         (void) snprintf(*client, MAX_K_NAME_SZ, "%s%s%s@%s", adat.pname,
 245             *adat.pinst ? "." : "", adat.pinst, adat.prealm);
 246
 247         /* Check ~/.klogin authorization now. */
 248         if (kuserok(&adat, (char *) server_user) != KSUCCESS) {
 249                 packet_send_debug("Kerberos V4 .klogin authorization failed!");
 250                 log("Kerberos V4 .klogin authorization failed for %s to account %s",
 251                     *client, server_user);
 252                 xfree(*client);
 253                 return 0;
 254         }
 255         /* Increment the checksum, and return it encrypted with the
 256            session key. */
 257         cksum = adat.checksum + 1;
 258         cksum = htonl(cksum);
 259
 260         /* If we can't successfully encrypt the checksum, we send back an
 261            empty message, admitting our failure. */
 262         if ((r = krb_mk_priv((u_char *) & cksum, reply.dat, sizeof(cksum) + 1,
 263             schedule, &adat.session, &local, &foreign)) < 0) {
 264                 packet_send_debug("Kerberos V4 mk_priv: (%d) %s", r, krb_err_txt[r]);
 265                 reply.dat[0] = 0;
 266                 reply.length = 0;
 267         } else
 268                 reply.length = r;
 269
 270         /* Clear session key. */
 271         memset(&adat.session, 0, sizeof(&adat.session));
 272
 273         packet_start(SSH_SMSG_AUTH_KERBEROS_RESPONSE);
 274         packet_put_string((char *) reply.dat, reply.length);
 275         packet_send();
 276         packet_write_wait();
 277         return 1;
 278 }
 279 #endif /* KRB4 */
 280
 281 #ifdef AFS
 282 int
 283 auth_kerberos_tgt(struct passwd *pw, const char *string)
 284 {
 285         CREDENTIALS creds;
 286
 287         if (pw == NULL)
 288                 goto auth_kerberos_tgt_failure;
 289         if (!radix_to_creds(string, &creds)) {
 290                 log("Protocol error decoding Kerberos V4 tgt");
 291                 packet_send_debug("Protocol error decoding Kerberos V4 tgt");
 292                 goto auth_kerberos_tgt_failure;
 293         }
 294         if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
 295                 strlcpy(creds.service, "krbtgt", sizeof creds.service);
 296
 297         if (strcmp(creds.service, "krbtgt")) {
 298                 log("Kerberos V4 tgt (%s%s%s@%s) rejected for %s", creds.pname,
 299                     creds.pinst[0] ? "." : "", creds.pinst, creds.realm,
 300                     pw->pw_name);
 301                 packet_send_debug("Kerberos V4 tgt (%s%s%s@%s) rejected for %s",
 302                     creds.pname, creds.pinst[0] ? "." : "", creds.pinst,
 303                     creds.realm, pw->pw_name);
 304                 goto auth_kerberos_tgt_failure;
 305         }
 306         if (!krb4_init(pw->pw_uid))
 307                 goto auth_kerberos_tgt_failure;
 308
 309         if (in_tkt(creds.pname, creds.pinst) != KSUCCESS)
 310                 goto auth_kerberos_tgt_failure;
 311
 312         if (save_credentials(creds.service, creds.instance, creds.realm,
 313             creds.session, creds.lifetime, creds.kvno,
 314             &creds.ticket_st, creds.issue_date) != KSUCCESS) {
 315                 packet_send_debug("Kerberos V4 tgt refused: couldn't save credentials");
 316                 goto auth_kerberos_tgt_failure;
 317         }
 318         /* Successful authentication, passed all checks. */
 319         chown(tkt_string(), pw->pw_uid, pw->pw_gid);
 320
 321         packet_send_debug("Kerberos V4 tgt accepted (%s.%s@%s, %s%s%s@%s)",
 322             creds.service, creds.instance, creds.realm, creds.pname,
 323             creds.pinst[0] ? "." : "", creds.pinst, creds.realm);
 324         memset(&creds, 0, sizeof(creds));
 325         packet_start(SSH_SMSG_SUCCESS);
 326         packet_send();
 327         packet_write_wait();
 328         return 1;
 329
 330 auth_kerberos_tgt_failure:
 331         krb4_cleanup_proc(NULL);
 332         memset(&creds, 0, sizeof(creds));
 333         packet_start(SSH_SMSG_FAILURE);
 334         packet_send();
 335         packet_write_wait();
 336         return 0;
 337 }
 338
 339 int
 340 auth_afs_token(struct passwd *pw, const char *token_string)
 341 {
 342         CREDENTIALS creds;
 343         uid_t uid;
 344
 345         if (pw == NULL) {
 346                 /* XXX fake protocol error */
 347                 packet_send_debug("Protocol error decoding AFS token");
 348                 packet_start(SSH_SMSG_FAILURE);
 349                 packet_send();
 350                 packet_write_wait();
 351                 return 0;
 352         }
 353         if (!radix_to_creds(token_string, &creds)) {
 354                 log("Protocol error decoding AFS token");
 355                 packet_send_debug("Protocol error decoding AFS token");
 356                 packet_start(SSH_SMSG_FAILURE);
 357                 packet_send();
 358                 packet_write_wait();
 359                 return 0;
 360         }
 361         if (strncmp(creds.service, "", 1) == 0) /* backward compatibility */
 362                 strlcpy(creds.service, "afs", sizeof creds.service);
 363
 364         if (strncmp(creds.pname, "AFS ID ", 7) == 0)
 365                 uid = atoi(creds.pname + 7);
 366         else
 367                 uid = pw->pw_uid;
 368
 369         if (kafs_settoken(creds.realm, uid, &creds)) {
 370                 log("AFS token (%s@%s) rejected for %s", creds.pname, creds.realm,
 371                     pw->pw_name);
 372                 packet_send_debug("AFS token (%s@%s) rejected for %s", creds.pname,
 373                     creds.realm, pw->pw_name);
 374                 memset(&creds, 0, sizeof(creds));
 375                 packet_start(SSH_SMSG_FAILURE);
 376                 packet_send();
 377                 packet_write_wait();
 378                 return 0;
 379         }
 380         packet_send_debug("AFS token accepted (%s@%s, %s@%s)", creds.service,
 381             creds.realm, creds.pname, creds.realm);
 382         memset(&creds, 0, sizeof(creds));
 383         packet_start(SSH_SMSG_SUCCESS);
 384         packet_send();
 385         packet_write_wait();
 386         return 1;
 387 }
 388 #endif /* AFS */