src/modules/rlm_krb5/rlm_krb5.c

   1 /*
   2  *   This program is free software; you can redistribute it and/or modify
   3  *   it under the terms of the GNU General Public License as published by
   4  *   the Free Software Foundation; either version 2 of the License, or
   5  *   (at your option) any later version.
   6  *
   7  *   This program is distributed in the hope that it will be useful,
   8  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *   GNU General Public License for more details.
  11  *
  12  *   You should have received a copy of the GNU General Public License
  13  *   along with this program; if not, write to the Free Software
  14  *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  15  */
  16
  17 /**
  18  * $Id$
  19  * @file rlm_krb5.c
  20  * @brief Authenticate users, retrieving their TGT from a Kerberos V5 TDC.
  21  *
  22  * @copyright 2000,2006,2012-2013  The FreeRADIUS server project
  23  * @copyright 2013  Arran Cudbard-Bell <a.cudbardb@freeradius.org>
  24  * @copyright 2000  Nathan Neulinger <nneul@umr.edu>
  25  * @copyright 2000  Alan DeKok <aland@ox.org>
  26  */
  27 #include        <freeradius-devel/ident.h>
  28 RCSID("$Id$")
  29
  30 #include        <freeradius-devel/radiusd.h>
  31 #include        <freeradius-devel/modules.h>
  32 #include        <freeradius-devel/rad_assert.h>
  33
  34 /* krb5 includes */
  35 #include <krb5.h>
  36 #include <com_err.h>
  37
  38 #define SERVICE_NAME_LEN 64         //!< Maximum length of a service name.
  39
  40 /** Instance configuration for rlm_krb5
  41  *
  42  * Holds the configuration and preparsed data for a instance of rlm_krb5.
  43  */
  44 typedef struct rlm_krb5_t {
  45         const char *xlat_name;      //!< This module's instance name.
  46         const char *keytabname;     //!< The keytab to resolve the service in.
  47         const char *service_princ;  //!< The service name provided by the
  48                                     //!< config parser.
  49
  50         char *hostname;             //!< The hostname component of
  51                                     //!< service_princ, or NULL.
  52         char *service;              //!< The service component of
  53                                     //!< service_princ, or NULL.
  54
  55         krb5_context *context;      //!< The kerberos context (cloned once per
  56                                     //!< request).
  57
  58 #ifndef HEIMDAL_KRB5
  59         krb5_get_init_creds_opt *gic_options;    //!< Options to pass to the
  60                                                  //!< get_initial_credentials.
  61                                                  //!< function.
  62         krb5_verify_init_creds_opt *vic_options; //!< Options to pass to the
  63                                                  //!< validate_initial_creds
  64                                                  //!< function.
  65
  66         krb5_principal server;      //!< A structure representing the parsed
  67                                     //!< service_princ.
  68 #endif
  69
  70 } rlm_krb5_t;
  71
  72 static const CONF_PARSER module_config[] = {
  73         { "keytab", PW_TYPE_STRING_PTR,
  74           offsetof(rlm_krb5_t,keytabname), NULL, NULL },
  75         { "service_principal", PW_TYPE_STRING_PTR,
  76           offsetof(rlm_krb5_t,service_princ), NULL, NULL },
  77         { NULL, -1, 0, NULL, NULL }
  78 };
  79
  80 static int krb5_detach(void *instance)
  81 {
  82         rlm_krb5_t *inst = instance;
  83
  84 #ifndef HEIMDAL_KRB5
  85         free(inst->vic_options);
  86
  87         if (inst->gic_options) {
  88                 krb5_get_init_creds_opt_free(*(inst->context),
  89                                              inst->gic_options);
  90         }
  91 #endif
  92
  93         /* Don't free hostname, it's just a pointer into service_princ */
  94         free(inst->service);
  95
  96         if (inst->context) {
  97                 krb5_free_context(*(inst->context));
  98         }
  99
 100         free(instance);
 101
 102         return 0;
 103 }
 104
 105 static int krb5_instantiate(CONF_SECTION *conf, void **instance)
 106 {
 107         rlm_krb5_t *inst;
 108         krb5_error_code ret;
 109
 110         krb5_context *context;
 111         char *princ_name;
 112
 113 #ifndef HEIMDAL_KRB5
 114         radlog(L_ERR, "rlm_krb5 (*): Using MIT Kerberos library");
 115 #else
 116         radlog(L_ERR, "rlm_krb5 (*): Using Heimdal Kerberos library");
 117 #endif
 118         /*
 119          *      @todo Update configure script to call krb5_is_thread_safe,
 120          *      this should really be a warning.
 121          */
 122         if (!krb5_is_thread_safe()) {
 123                 radlog(L_ERR, "rlm_krb5 (*): krb5 library is not threadsafe, "
 124                        "please recompile it with thread support enabled");
 125
 126                 return -1;
 127         }
 128
 129         *instance = inst = talloc_zero(conf, rlm_krb5_t);
 130         if (cf_section_parse(conf, inst, module_config) < 0) {
 131                 return -1;
 132         }
 133
 134         inst->xlat_name = cf_section_name2(conf);
 135         if (!inst->xlat_name) {
 136                 inst->xlat_name = cf_section_name1(conf);
 137         }
 138
 139         context = inst->context = rad_calloc(sizeof(*context));
 140         ret = krb5_init_context(context);
 141         if (ret) {
 142                 radlog(L_ERR, "rlm_krb5 (%s): Context initialisation "
 143                        "failed: %s", inst->xlat_name, error_message(ret));
 144
 145                 goto error;
 146         } else {
 147                 radlog(L_DBG, "rlm_krb5 (%s): Context initialised "
 148                        "successfully", inst->xlat_name);
 149         }
 150
 151         /*
 152          *      Split service principal into service and host components
 153          *      they're needed to build the server principal in MIT,
 154          *      and to set the validation service in Heimdal.
 155          */
 156         if (inst->service_princ) {
 157                 size_t len;
 158                 /* Service principal appears to contain a host component */
 159                 inst->hostname = strchr(inst->service_princ, '/');
 160                 if (inst->hostname) {
 161                         len = (inst->hostname - inst->service_princ);
 162                         inst->hostname++;
 163                 } else {
 164                         len = SERVICE_NAME_LEN;
 165                 }
 166
 167                 if (len) {
 168                         inst->service = rad_malloc(len + 1);
 169                         strlcpy(inst->service, inst->service_princ, len);
 170                 }
 171         }
 172
 173 #ifndef HEIMDAL_KRB5
 174         /*
 175          *      Convert the service principal string to a krb5 principal.
 176          */
 177         ret = krb5_sname_to_principal(*context, inst->hostname,
 178                                       inst->service, KRB5_NT_SRV_HST,
 179                                       &(inst->server));
 180         if (ret) {
 181                 radlog(L_ERR, "rlm_krb5 (%s): Failed parsing service "
 182                        "principal: %s", inst->xlat_name, error_message(ret));
 183
 184                 goto error;
 185         }
 186
 187         ret = krb5_unparse_name(*context, inst->server, &princ_name);
 188         if (ret) {
 189                 /* Uh? */
 190                 radlog(L_ERR, "rlm_krb5 (%s): Failed constructing service "
 191                        "principal string: %s", inst->xlat_name,
 192                        error_message(ret));
 193
 194                 goto error;
 195         }
 196
 197         /*
 198          *      Not necessarily the same as the config item
 199          */
 200         radlog(L_DBG, "rlm_krb5 (%s): Using service principal \"%s\"",
 201                inst->xlat_name, princ_name);
 202
 203         krb5_free_unparsed_name(*context, princ_name);
 204
 205         /*
 206          *      Setup options for getting credentials and verifying them
 207          */
 208
 209         /* For some reason the 'init' version of this function is deprecated */
 210         ret = krb5_get_init_creds_opt_alloc(*context, &(inst->gic_options));
 211         if (ret) {
 212                 radlog(L_ERR, "rlm_krb5 (%s): Couldn't allocated inital "
 213                        "credential options: %s", inst->xlat_name,
 214                        error_message(ret));
 215
 216                 goto error;
 217         }
 218
 219         inst->vic_options = rad_calloc(sizeof(*(inst->vic_options)));
 220         if (!inst->vic_options) goto error;
 221
 222         krb5_verify_init_creds_opt_init(inst->vic_options);
 223         krb5_verify_init_creds_opt_set_ap_req_nofail(inst->vic_options,
 224                                                      TRUE);
 225
 226 #else
 227         if (inst->hostname) {
 228                 radlog(L_DBG, "rlm_krb5 (%s): Ignoring hostname component of "
 229                        "service principal \"%s\", not needed/supported by "
 230                        "Heimdal", inst->xlat_name, hostname);
 231         }
 232 #endif
 233
 234         return 0;
 235
 236         error:
 237         krb5_detach(inst);
 238         return -1;
 239 }
 240
 241 static rlm_rcode_t krb5_parse_user(rlm_krb5_t *inst, REQUEST *request,
 242                                    krb5_principal *client)
 243 {
 244         krb5_error_code ret;
 245         char *princ_name;
 246
 247         /*
 248          *      We can only authenticate user requests which HAVE
 249          *      a User-Name attribute.
 250          */
 251         if (!request->username) {
 252                 RDEBUG("Attribute \"User-Name\" is required for "
 253                        "authentication");
 254
 255                 return RLM_MODULE_INVALID;
 256         }
 257
 258         /*
 259          *      We can only authenticate user requests which HAVE
 260          *      a User-Password attribute.
 261          */
 262         if (!request->password) {
 263                 RDEBUG("Attribute \"User-Password\" is required for "
 264                        "authentication");
 265
 266                 return RLM_MODULE_INVALID;
 267         }
 268
 269         /*
 270          *      Ensure that we're being passed a plain-text password,
 271          *      and not anything else.
 272          */
 273         if (request->password->da->attr != PW_USER_PASSWORD) {
 274                 RDEBUG("Attribute \"User-Password\" is required for "
 275                        "authentication.  Cannot use \"%s\".",
 276                        request->password->da->name);
 277
 278                 return RLM_MODULE_INVALID;
 279         }
 280
 281         ret = krb5_parse_name(*(inst->context), request->username->vp_strvalue,
 282                               client);
 283         if (ret) {
 284                 RDEBUG("Failed parsing username as principal: %s",
 285                        error_message(ret));
 286
 287                 return RLM_MODULE_FAIL;
 288         }
 289
 290         krb5_unparse_name(*(inst->context), *client, &princ_name);
 291         RDEBUG("Using client principal \"%s\"", princ_name);
 292         krb5_free_unparsed_name(*(inst->context), princ_name);
 293
 294         return RLM_MODULE_OK;
 295 }
 296
 297 #ifndef HEIMDAL_KRB5
 298
 299 /*
 300  *  Validate userid/passwd (MIT)
 301  */
 302 static rlm_rcode_t krb5_auth(void *instance, REQUEST *request)
 303 {
 304         rlm_krb5_t *inst = instance;
 305         rlm_rcode_t rcode;
 306         krb5_error_code ret;
 307
 308         krb5_principal client;
 309         krb5_creds init_creds;
 310         krb5_keytab keytab;
 311         krb5_context *context = NULL;
 312
 313         /*
 314          *      All the snippets on threadsafety say that individual threads
 315          *      must each use their own copy of context.
 316          *
 317          *      As we don't have any per thread instantiation, we either have
 318          *      to clone inst->context on every request, or use the connection
 319          *      API.
 320          *
 321          *      @todo Use the connection API (3.0 only).
 322          */
 323         ret = krb5_copy_context(*(inst->context), context);
 324         if (ret) {
 325                 radlog(L_ERR, "rlm_krb5 (%s): Error cloning krb5 context: %s",
 326                        inst->xlat_name, error_message(ret));
 327
 328                 return RLM_MODULE_FAIL;
 329         }
 330
 331         /*
 332          *      Check we have all the required VPs, and convert the username
 333          *      into a principal.
 334          */
 335         rcode = krb5_parse_user(inst, request, &client);
 336         if (rcode != RLM_MODULE_OK) goto cleanup;
 337
 338         /*
 339          *      Retrieve the TGT from the TGS/KDC and check we can decrypt it.
 340          */
 341         memset(&init_creds, 0, sizeof(init_creds));
 342         ret = krb5_get_init_creds_password(*context, &init_creds, client,
 343                                            request->password->vp_strvalue,
 344                                            NULL, NULL, 0, NULL,
 345                                            inst->gic_options);
 346         if (ret) {
 347                 error:
 348                 switch (ret) {
 349                 case KRB5_LIBOS_BADPWDMATCH:
 350                 case KRB5KRB_AP_ERR_BAD_INTEGRITY:
 351                         RDEBUG("Provided password was incorrect: %s",
 352                                error_message(ret));
 353                         rcode = RLM_MODULE_REJECT;
 354                         break;
 355
 356                 case KRB5KDC_ERR_KEY_EXP:
 357                 case KRB5KDC_ERR_CLIENT_REVOKED:
 358                 case KRB5KDC_ERR_SERVICE_REVOKED:
 359                         RDEBUG("Account has been locked out: %s",
 360                                error_message(ret));
 361                         rcode = RLM_MODULE_USERLOCK;
 362                         break;
 363
 364                 case KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN:
 365                         RDEBUG("User not found: %s", error_message(ret));
 366                         rcode = RLM_MODULE_NOTFOUND;
 367                         break;
 368
 369                 default:
 370                         radlog(L_ERR, "rlm_krb5 (%s): Failed getting/verifying "
 371                                "credentials: %s", inst->xlat_name,
 372                                error_message(ret));
 373                         rcode = RLM_MODULE_FAIL;
 374                         break;
 375                 }
 376
 377                 goto cleanup;
 378         }
 379
 380         RDEBUG("Successfully retrieved and decrypted TGT");
 381
 382         memset(&keytab, 0, sizeof(keytab));
 383         ret = inst->keytabname ?
 384                 krb5_kt_resolve(*context, inst->keytabname, &keytab) :
 385                 krb5_kt_default(*context, &keytab);
 386         if (ret) {
 387                 radlog(L_ERR, "rlm_krb5 (%s): Resolving keytab failed: %s",
 388                        inst->xlat_name, error_message(ret));
 389
 390                 goto cleanup;
 391         }
 392
 393         ret = krb5_verify_init_creds(*context, &init_creds, inst->server,
 394                                      keytab, NULL, inst->vic_options);
 395         if (ret) goto error;
 396
 397         cleanup:
 398
 399         if (context) {
 400                 krb5_free_cred_contents(*context, &init_creds);
 401                 krb5_free_context(*context);
 402                 krb5_kt_close(*context, keytab);
 403         }
 404
 405         return rcode;
 406 }
 407
 408 #else
 409
 410 /*
 411  *      Validate user/pass (Heimdal)
 412  */
 413 static rlm_rcode_t krb5_auth(void *instance, REQUEST *request)
 414 {
 415         rlm_krb5_t *inst = instance;
 416         rlm_rcode_t rcode;
 417
 418         krb5_error_code ret;
 419
 420         krb5_principal client;
 421         krb5_ccache ccache;
 422         krb5_keytab keytab;
 423         krb5_verify_opt options;
 424         krb5_context *context = NULL;
 425
 426         /*
 427          *      See above in MIT krb5_auth
 428          */
 429         ret = krb5_copy_context(*(inst->context), context);
 430         if (ret) {
 431                 radlog(L_ERR, "rlm_krb5 (%s): Error cloning krb5 context: %s",
 432                        inst->xlat_name, error_message(ret));
 433
 434                 return RLM_MODULE_FAIL;
 435         }
 436
 437         /*
 438          *      Setup krb5_verify_user options
 439          *
 440          *      Not entirely sure this is necessary, but as we use context
 441          *      to get the cache handle, we probably do have to do this with
 442          *      the cloned context.
 443          */
 444         krb5_cc_default(*context, &ccache);
 445
 446         krb5_verify_opt_init(&options);
 447         krb5_verify_opt_set_ccache(&options, ccache);
 448
 449         memset(&keytab, 0, sizeof(keytab));
 450         ret = inst->keytabname ?
 451                 krb5_kt_resolve(*context, inst->keytabname, &keytab) :
 452                 krb5_kt_default(*context, &keytab);
 453         if (ret) {
 454                 radlog(L_ERR, "rlm_krb5 (%s): Resolving keytab failed: %s",
 455                        inst->xlat_name, error_message(ret));
 456
 457                 goto cleanup;
 458         }
 459
 460         krb5_verify_opt_set_keytab(&options, keytab);
 461         krb5_verify_opt_set_secure(&options, TRUE);
 462
 463         if (inst->service) {
 464                 krb5_verify_opt_set_service(&options, inst->service);
 465         }
 466
 467         rcode = krb5_parse_user(inst, request, &client);
 468         if (rcode != RLM_MODULE_OK) goto cleanup;
 469
 470         /*
 471          *      Verify the user, using the options we set in instantiate
 472          */
 473         ret = krb5_verify_user_opt(*context, client,
 474                                    request->password->vp_strvalue,
 475                                    &options);
 476         if (ret) {
 477                 switch (ret) {
 478                 case KRB5_LIBOS_BADPWDMATCH:
 479                 case KRB5KRB_AP_ERR_BAD_INTEGRITY:
 480                         RDEBUG("Provided password was incorrect: %s",
 481                                error_message(ret));
 482                         rcode = RLM_MODULE_REJECT;
 483
 484                         break;
 485                 case KRB5KDC_ERR_KEY_EXP:
 486                 case KRB5KDC_ERR_CLIENT_REVOKED:
 487                 case KRB5KDC_ERR_SERVICE_REVOKED:
 488                         RDEBUG("Account has been locked out: %s",
 489                                error_message(ret));
 490                         rcode = RLM_MODULE_USERLOCK;
 491
 492                         break;
 493                 case KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN:
 494                         RDEBUG("User not found: %s", error_message(ret));
 495                         rcode = RLM_MODULE_NOTFOUND;
 496
 497                 default:
 498                         radlog(L_ERR, "rlm_krb5 (%s): Verifying user failed: "
 499                                "%s", inst->xlat_name, error_message(ret));
 500                         rcode = RLM_MODULE_FAIL;
 501
 502                         break;
 503                 }
 504
 505                 goto cleanup;
 506         }
 507
 508         cleanup:
 509
 510         krb5_free_context(*context);
 511         krb5_kt_close(*context, keytab);
 512
 513         return rcode;
 514 }
 515
 516 #endif /* HEIMDAL_KRB5 */
 517
 518 module_t rlm_krb5 = {
 519         RLM_MODULE_INIT,
 520         "Kerberos",
 521         RLM_TYPE_THREAD_SAFE | RLM_TYPE_CHECK_CONFIG_SAFE | RLM_TYPE_HUP_SAFE,
 522         krb5_instantiate,               /* instantiation */
 523         krb5_detach,                    /* detach */
 524         {
 525                 krb5_auth,              /* authenticate */
 526                 NULL,                   /* authorize */
 527                 NULL,                   /* pre-accounting */
 528                 NULL,                   /* accounting */
 529                 NULL,                   /* checksimul */
 530                 NULL,                   /* pre-proxy */
 531                 NULL,                   /* post-proxy */
 532                 NULL                    /* post-auth */
 533         },
 534 };