auth/kerberos/gssapi_pac.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    kerberos authorization data (PAC) utility library
   4    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2011
   5    Copyright (C) Simo Sorce 2010.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "includes.h"
  22 #ifdef HAVE_KRB5
  23
  24 #include "auth/kerberos/pac_utils.h"
  25
  26 #if 0
  27 /* FIXME - need proper configure/waf test
  28  * to determine if gss_mech_krb5 and friends
  29  * exist. JRA.
  30  */
  31 /*
  32  * These are not exported by Solaris -lkrb5
  33  * Maybe move to libreplace somewhere?
  34  */
  35 static const gss_OID_desc krb5_gss_oid_array[] = {
  36         /* this is the official, rfc-specified OID */
  37         { 9, "\052\206\110\206\367\022\001\002\002" },
  38         /* this is the pre-RFC mech OID */
  39         { 5, "\053\005\001\005\002" },
  40         /* this is the unofficial, incorrect mech OID emitted by MS */
  41         { 9, "\052\206\110\202\367\022\001\002\002" },
  42         { 0, 0 }
  43 };
  44
  45 const gss_OID_desc * const gss_mech_krb5              = krb5_gss_oid_array+0;
  46 const gss_OID_desc * const gss_mech_krb5_old          = krb5_gss_oid_array+1;
  47 const gss_OID_desc * const gss_mech_krb5_wrong        = krb5_gss_oid_array+2;
  48 #endif
  49
  50 #ifndef GSS_KRB5_INQ_SSPI_SESSION_KEY_OID
  51 #define GSS_KRB5_INQ_SSPI_SESSION_KEY_OID_LENGTH 11
  52 #define GSS_KRB5_INQ_SSPI_SESSION_KEY_OID "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x05\x05"
  53 #endif
  54
  55 gss_OID_desc gse_sesskey_inq_oid = {
  56         GSS_KRB5_INQ_SSPI_SESSION_KEY_OID_LENGTH,
  57         discard_const(GSS_KRB5_INQ_SSPI_SESSION_KEY_OID)
  58 };
  59
  60 #ifndef GSS_KRB5_SESSION_KEY_ENCTYPE_OID
  61 #define GSS_KRB5_SESSION_KEY_ENCTYPE_OID_LENGTH 10
  62 #define GSS_KRB5_SESSION_KEY_ENCTYPE_OID  "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x04"
  63 #endif
  64
  65 gss_OID_desc gse_sesskeytype_oid = {
  66         GSS_KRB5_SESSION_KEY_ENCTYPE_OID_LENGTH,
  67         discard_const(GSS_KRB5_SESSION_KEY_ENCTYPE_OID)
  68 };
  69
  70 /* The Heimdal OID for getting the PAC */
  71 #define EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID_LENGTH 8
  72 /*                                                      EXTRACTION OID             AUTHZ ID */
  73 #define EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID "\x2a\x85\x70\x2b\x0d\x03" "\x81\x00"
  74
  75 NTSTATUS gssapi_obtain_pac_blob(TALLOC_CTX *mem_ctx,
  76                                 gss_ctx_id_t gssapi_context,
  77                                 gss_name_t gss_client_name,
  78                                 DATA_BLOB *pac_blob)
  79 {
  80         NTSTATUS status;
  81         OM_uint32 gss_maj, gss_min;
  82 #ifdef HAVE_GSS_GET_NAME_ATTRIBUTE
  83 /*
  84  * gss_get_name_attribute() in MIT krb5 1.10.0 can return unintialized pac_display_buffer
  85  * and later gss_release_buffer() will crash on attempting to release it.
  86  *
  87  * So always initialize the buffer descriptors.
  88  *
  89  * See following links for more details:
  90  * http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=658514
  91  * http://krbdev.mit.edu/rt/Ticket/Display.html?user=guest&pass=guest&id=7087
  92  */
  93         gss_buffer_desc pac_buffer = {
  94                 .value = NULL,
  95                 .length = 0
  96         };
  97         gss_buffer_desc pac_display_buffer = {
  98                 .value = NULL,
  99                 .length = 0
 100         };
 101         gss_buffer_desc pac_name = {
 102                 .value = discard_const("urn:mspac:"),
 103                 .length = sizeof("urn:mspac:")-1
 104         };
 105         int more = -1;
 106         int authenticated = false;
 107         int complete = false;
 108
 109         gss_maj = gss_get_name_attribute(
 110                 &gss_min, gss_client_name, &pac_name,
 111                 &authenticated, &complete,
 112                 &pac_buffer, &pac_display_buffer, &more);
 113
 114         if (gss_maj != 0) {
 115                 DEBUG(0, ("obtaining PAC via GSSAPI gss_get_name_attribute failed: %s\n",
 116                           gssapi_error_string(mem_ctx, gss_maj, gss_min, gss_mech_krb5)));
 117                 return NT_STATUS_ACCESS_DENIED;
 118         } else if (authenticated && complete) {
 119                 /* The PAC blob is returned directly */
 120                 *pac_blob = data_blob_talloc(mem_ctx, pac_buffer.value,
 121                                             pac_buffer.length);
 122
 123                 if (!pac_blob->data) {
 124                         status = NT_STATUS_NO_MEMORY;
 125                 } else {
 126                         status = NT_STATUS_OK;
 127                 }
 128
 129                 gss_maj = gss_release_buffer(&gss_min, &pac_buffer);
 130                 gss_maj = gss_release_buffer(&gss_min, &pac_display_buffer);
 131                 return status;
 132         } else {
 133                 DEBUG(0, ("obtaining PAC via GSSAPI failed: authenticated: %s, complete: %s, more: %s\n",
 134                           authenticated ? "true" : "false",
 135                           complete ? "true" : "false",
 136                           more ? "true" : "false"));
 137                 return NT_STATUS_ACCESS_DENIED;
 138         }
 139
 140 #elif defined(HAVE_GSS_INQUIRE_SEC_CONTEXT_BY_OID)
 141         gss_OID_desc pac_data_oid = {
 142                 .elements = discard_const(EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID),
 143                 .length = EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID_LENGTH
 144         };
 145
 146         gss_buffer_set_t set = GSS_C_NO_BUFFER_SET;
 147
 148         /* If we didn't have the routine to get a verified, validated
 149          * PAC (supplied only by MIT at the time of writing), then try
 150          * with the Heimdal OID (fetches the PAC directly and always
 151          * validates) */
 152         gss_maj = gss_inquire_sec_context_by_oid(
 153                                 &gss_min, gssapi_context,
 154                                 &pac_data_oid, &set);
 155
 156         /* First check for the error MIT gives for an unknown OID */
 157         if (gss_maj == GSS_S_UNAVAILABLE) {
 158                 DEBUG(1, ("unable to obtain a PAC against this GSSAPI library.  "
 159                           "GSSAPI secured connections are available only with Heimdal or MIT Kerberos >= 1.8\n"));
 160         } else if (gss_maj != 0) {
 161                 DEBUG(2, ("obtaining PAC via GSSAPI gss_inqiure_sec_context_by_oid (Heimdal OID) failed: %s\n",
 162                           gssapi_error_string(mem_ctx, gss_maj, gss_min, gss_mech_krb5)));
 163         } else {
 164                 if (set == GSS_C_NO_BUFFER_SET) {
 165                         DEBUG(0, ("gss_inquire_sec_context_by_oid returned unknown "
 166                                   "data in results.\n"));
 167                         return NT_STATUS_INTERNAL_ERROR;
 168                 }
 169
 170                 /* The PAC blob is returned directly */
 171                 *pac_blob = data_blob_talloc(mem_ctx, set->elements[0].value,
 172                                             set->elements[0].length);
 173                 if (!pac_blob->data) {
 174                         status = NT_STATUS_NO_MEMORY;
 175                 } else {
 176                         status = NT_STATUS_OK;
 177                 }
 178
 179                 gss_maj = gss_release_buffer_set(&gss_min, &set);
 180                 return status;
 181         }
 182 #else
 183         DEBUG(1, ("unable to obtain a PAC against this GSSAPI library.  "
 184                   "GSSAPI secured connections are available only with Heimdal or MIT Kerberos >= 1.8\n"));
 185 #endif
 186         return NT_STATUS_ACCESS_DENIED;
 187 }
 188
 189 NTSTATUS gssapi_get_session_key(TALLOC_CTX *mem_ctx,
 190                                 gss_ctx_id_t gssapi_context,
 191                                 DATA_BLOB *session_key,
 192                                 uint32_t *keytype)
 193 {
 194         OM_uint32 gss_min, gss_maj;
 195         gss_buffer_set_t set = GSS_C_NO_BUFFER_SET;
 196
 197         gss_maj = gss_inquire_sec_context_by_oid(
 198                                 &gss_min, gssapi_context,
 199                                 &gse_sesskey_inq_oid, &set);
 200         if (gss_maj) {
 201                 DEBUG(0, ("gss_inquire_sec_context_by_oid failed [%s]\n",
 202                           gssapi_error_string(mem_ctx, gss_maj, gss_min, gss_mech_krb5)));
 203                 return NT_STATUS_NO_USER_SESSION_KEY;
 204         }
 205
 206         if ((set == GSS_C_NO_BUFFER_SET) ||
 207             (set->count == 0)) {
 208 #ifdef HAVE_GSSKRB5_GET_SUBKEY
 209                 krb5_keyblock *subkey;
 210                 gss_maj = gsskrb5_get_subkey(&gss_min,
 211                                              gssapi_context,
 212                                              &subkey);
 213                 if (gss_maj != 0) {
 214                         DEBUG(1, ("NO session key for this mech\n"));
 215                         return NT_STATUS_NO_USER_SESSION_KEY;
 216                 }
 217                 if (session_key) {
 218                         *session_key = data_blob_talloc(mem_ctx,
 219                                                         KRB5_KEY_DATA(subkey), KRB5_KEY_LENGTH(subkey));
 220                 }
 221                 if (keytype) {
 222                         *keytype = KRB5_KEY_TYPE(subkey);
 223                 }
 224                 krb5_free_keyblock(NULL /* should be krb5_context */, subkey);
 225                 return NT_STATUS_OK;
 226 #else
 227                 DEBUG(0, ("gss_inquire_sec_context_by_oid didn't return any session key (and no alternative method available)\n"));
 228                 return NT_STATUS_NO_USER_SESSION_KEY;
 229 #endif
 230         }
 231
 232         if (session_key) {
 233                 *session_key = data_blob_talloc(mem_ctx, set->elements[0].value,
 234                                                 set->elements[0].length);
 235         }
 236
 237         if (keytype) {
 238                 int diflen, i;
 239                 const uint8_t *p;
 240
 241                 if (set->count < 2) {
 242
 243 #ifdef HAVE_GSSKRB5_GET_SUBKEY
 244                         krb5_keyblock *subkey;
 245                         gss_maj = gsskrb5_get_subkey(&gss_min,
 246                                                      gssapi_context,
 247                                                      &subkey);
 248                         if (gss_maj == 0) {
 249                                 *keytype = KRB5_KEY_TYPE(subkey);
 250                                 krb5_free_keyblock(NULL /* should be krb5_context */, subkey);
 251                         } else
 252 #else
 253                         {
 254                                 *keytype = 0;
 255                         }
 256 #endif
 257                         gss_maj = gss_release_buffer_set(&gss_min, &set);
 258
 259                         return NT_STATUS_OK;
 260
 261                 } else if (memcmp(set->elements[1].value,
 262                                   gse_sesskeytype_oid.elements,
 263                                   gse_sesskeytype_oid.length) != 0) {
 264                         /* Perhaps a non-krb5 session key */
 265                         *keytype = 0;
 266                         gss_maj = gss_release_buffer_set(&gss_min, &set);
 267                         return NT_STATUS_OK;
 268                 }
 269                 p = (const uint8_t *)set->elements[1].value + gse_sesskeytype_oid.length;
 270                 diflen = set->elements[1].length - gse_sesskeytype_oid.length;
 271                 if (diflen <= 0) {
 272                         gss_maj = gss_release_buffer_set(&gss_min, &set);
 273                         return NT_STATUS_INVALID_PARAMETER;
 274                 }
 275                 *keytype = 0;
 276                 for (i = 0; i < diflen; i++) {
 277                         *keytype = (*keytype << 7) | (p[i] & 0x7f);
 278                         if (i + 1 != diflen && (p[i] & 0x80) == 0) {
 279                                 gss_maj = gss_release_buffer_set(&gss_min, &set);
 280                                 return NT_STATUS_INVALID_PARAMETER;
 281                         }
 282                 }
 283         }
 284
 285         gss_maj = gss_release_buffer_set(&gss_min, &set);
 286         return NT_STATUS_OK;
 287 }
 288
 289
 290 char *gssapi_error_string(TALLOC_CTX *mem_ctx,
 291                           OM_uint32 maj_stat, OM_uint32 min_stat,
 292                           const gss_OID mech)
 293 {
 294         OM_uint32 disp_min_stat, disp_maj_stat;
 295         gss_buffer_desc maj_error_message;
 296         gss_buffer_desc min_error_message;
 297         char *maj_error_string, *min_error_string;
 298         OM_uint32 msg_ctx = 0;
 299
 300         char *ret;
 301
 302         maj_error_message.value = NULL;
 303         min_error_message.value = NULL;
 304         maj_error_message.length = 0;
 305         min_error_message.length = 0;
 306
 307         disp_maj_stat = gss_display_status(&disp_min_stat, maj_stat,
 308                                            GSS_C_GSS_CODE, mech,
 309                                            &msg_ctx, &maj_error_message);
 310         if (disp_maj_stat != 0) {
 311                 maj_error_message.value = NULL;
 312                 maj_error_message.length = 0;
 313         }
 314         disp_maj_stat = gss_display_status(&disp_min_stat, min_stat,
 315                                            GSS_C_MECH_CODE, mech,
 316                                            &msg_ctx, &min_error_message);
 317         if (disp_maj_stat != 0) {
 318                 min_error_message.value = NULL;
 319                 min_error_message.length = 0;
 320         }
 321
 322         maj_error_string = talloc_strndup(mem_ctx,
 323                                           (char *)maj_error_message.value,
 324                                           maj_error_message.length);
 325
 326         min_error_string = talloc_strndup(mem_ctx,
 327                                           (char *)min_error_message.value,
 328                                           min_error_message.length);
 329
 330         ret = talloc_asprintf(mem_ctx, "%s: %s",
 331                                 maj_error_string, min_error_string);
 332
 333         talloc_free(maj_error_string);
 334         talloc_free(min_error_string);
 335
 336         gss_release_buffer(&disp_min_stat, &maj_error_message);
 337         gss_release_buffer(&disp_min_stat, &min_error_message);
 338
 339         return ret;
 340 }
 341
 342 #endif /* HAVE_KRB5 */