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                 DBG_NOTICE("obtaining PAC via GSSAPI gss_get_name_attribute "
 116                            "failed: %s\n", gssapi_error_string(mem_ctx,
 117                                                                gss_maj, gss_min,
 118                                                                gss_mech_krb5));
 119                 return NT_STATUS_ACCESS_DENIED;
 120         } else if (authenticated && complete) {
 121                 /* The PAC blob is returned directly */
 122                 *pac_blob = data_blob_talloc(mem_ctx, pac_buffer.value,
 123                                             pac_buffer.length);
 124
 125                 if (!pac_blob->data) {
 126                         status = NT_STATUS_NO_MEMORY;
 127                 } else {
 128                         status = NT_STATUS_OK;
 129                 }
 130
 131                 gss_maj = gss_release_buffer(&gss_min, &pac_buffer);
 132                 gss_maj = gss_release_buffer(&gss_min, &pac_display_buffer);
 133                 return status;
 134         } else {
 135                 DEBUG(0, ("obtaining PAC via GSSAPI failed: authenticated: %s, complete: %s, more: %s\n",
 136                           authenticated ? "true" : "false",
 137                           complete ? "true" : "false",
 138                           more ? "true" : "false"));
 139                 return NT_STATUS_ACCESS_DENIED;
 140         }
 141
 142 #elif defined(HAVE_GSS_INQUIRE_SEC_CONTEXT_BY_OID)
 143         gss_OID_desc pac_data_oid = {
 144                 .elements = discard_const(EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID),
 145                 .length = EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID_LENGTH
 146         };
 147
 148         gss_buffer_set_t set = GSS_C_NO_BUFFER_SET;
 149
 150         /* If we didn't have the routine to get a verified, validated
 151          * PAC (supplied only by MIT at the time of writing), then try
 152          * with the Heimdal OID (fetches the PAC directly and always
 153          * validates) */
 154         gss_maj = gss_inquire_sec_context_by_oid(
 155                                 &gss_min, gssapi_context,
 156                                 &pac_data_oid, &set);
 157
 158         /* First check for the error MIT gives for an unknown OID */
 159         if (gss_maj == GSS_S_UNAVAILABLE) {
 160                 DEBUG(1, ("unable to obtain a PAC against this GSSAPI library.  "
 161                           "GSSAPI secured connections are available only with Heimdal or MIT Kerberos >= 1.8\n"));
 162         } else if (gss_maj != 0) {
 163                 DEBUG(2, ("obtaining PAC via GSSAPI gss_inqiure_sec_context_by_oid (Heimdal OID) failed: %s\n",
 164                           gssapi_error_string(mem_ctx, gss_maj, gss_min, gss_mech_krb5)));
 165         } else {
 166                 if (set == GSS_C_NO_BUFFER_SET) {
 167                         DEBUG(0, ("gss_inquire_sec_context_by_oid returned unknown "
 168                                   "data in results.\n"));
 169                         return NT_STATUS_INTERNAL_ERROR;
 170                 }
 171
 172                 /* The PAC blob is returned directly */
 173                 *pac_blob = data_blob_talloc(mem_ctx, set->elements[0].value,
 174                                             set->elements[0].length);
 175                 if (!pac_blob->data) {
 176                         status = NT_STATUS_NO_MEMORY;
 177                 } else {
 178                         status = NT_STATUS_OK;
 179                 }
 180
 181                 gss_maj = gss_release_buffer_set(&gss_min, &set);
 182                 return status;
 183         }
 184 #else
 185         DEBUG(1, ("unable to obtain a PAC against this GSSAPI library.  "
 186                   "GSSAPI secured connections are available only with Heimdal or MIT Kerberos >= 1.8\n"));
 187 #endif
 188         return NT_STATUS_ACCESS_DENIED;
 189 }
 190
 191 NTSTATUS gssapi_get_session_key(TALLOC_CTX *mem_ctx,
 192                                 gss_ctx_id_t gssapi_context,
 193                                 DATA_BLOB *session_key,
 194                                 uint32_t *keytype)
 195 {
 196         OM_uint32 gss_min, gss_maj;
 197         gss_buffer_set_t set = GSS_C_NO_BUFFER_SET;
 198
 199         gss_maj = gss_inquire_sec_context_by_oid(
 200                                 &gss_min, gssapi_context,
 201                                 &gse_sesskey_inq_oid, &set);
 202         if (gss_maj) {
 203                 DEBUG(0, ("gss_inquire_sec_context_by_oid failed [%s]\n",
 204                           gssapi_error_string(mem_ctx,
 205                                               gss_maj,
 206                                               gss_min,
 207                                               discard_const_p(struct gss_OID_desc_struct,
 208                                                               gss_mech_krb5))));
 209                 return NT_STATUS_NO_USER_SESSION_KEY;
 210         }
 211
 212         if ((set == GSS_C_NO_BUFFER_SET) ||
 213             (set->count == 0)) {
 214 #ifdef HAVE_GSSKRB5_GET_SUBKEY
 215                 krb5_keyblock *subkey;
 216                 gss_maj = gsskrb5_get_subkey(&gss_min,
 217                                              gssapi_context,
 218                                              &subkey);
 219                 if (gss_maj != 0) {
 220                         DEBUG(1, ("NO session key for this mech\n"));
 221                         return NT_STATUS_NO_USER_SESSION_KEY;
 222                 }
 223                 if (session_key) {
 224                         *session_key = data_blob_talloc(mem_ctx,
 225                                                         KRB5_KEY_DATA(subkey), KRB5_KEY_LENGTH(subkey));
 226                 }
 227                 if (keytype) {
 228                         *keytype = KRB5_KEY_TYPE(subkey);
 229                 }
 230                 krb5_free_keyblock(NULL /* should be krb5_context */, subkey);
 231                 return NT_STATUS_OK;
 232 #else
 233                 DEBUG(0, ("gss_inquire_sec_context_by_oid didn't return any session key (and no alternative method available)\n"));
 234                 return NT_STATUS_NO_USER_SESSION_KEY;
 235 #endif
 236         }
 237
 238         if (session_key) {
 239                 *session_key = data_blob_talloc(mem_ctx, set->elements[0].value,
 240                                                 set->elements[0].length);
 241         }
 242
 243         if (keytype) {
 244                 int diflen, i;
 245                 const uint8_t *p;
 246
 247                 *keytype = 0;
 248                 if (set->count < 2) {
 249
 250 #ifdef HAVE_GSSKRB5_GET_SUBKEY
 251                         krb5_keyblock *subkey;
 252                         gss_maj = gsskrb5_get_subkey(&gss_min,
 253                                                      gssapi_context,
 254                                                      &subkey);
 255                         if (gss_maj == 0) {
 256                                 *keytype = KRB5_KEY_TYPE(subkey);
 257                                 krb5_free_keyblock(NULL /* should be krb5_context */, subkey);
 258                         }
 259 #endif
 260                         gss_maj = gss_release_buffer_set(&gss_min, &set);
 261
 262                         return NT_STATUS_OK;
 263
 264                 } else if (memcmp(set->elements[1].value,
 265                                   gse_sesskeytype_oid.elements,
 266                                   gse_sesskeytype_oid.length) != 0) {
 267                         /* Perhaps a non-krb5 session key */
 268                         gss_maj = gss_release_buffer_set(&gss_min, &set);
 269                         return NT_STATUS_OK;
 270                 }
 271                 p = (const uint8_t *)set->elements[1].value + gse_sesskeytype_oid.length;
 272                 diflen = set->elements[1].length - gse_sesskeytype_oid.length;
 273                 if (diflen <= 0) {
 274                         gss_maj = gss_release_buffer_set(&gss_min, &set);
 275                         return NT_STATUS_INVALID_PARAMETER;
 276                 }
 277                 for (i = 0; i < diflen; i++) {
 278                         *keytype = (*keytype << 7) | (p[i] & 0x7f);
 279                         if (i + 1 != diflen && (p[i] & 0x80) == 0) {
 280                                 gss_maj = gss_release_buffer_set(&gss_min, &set);
 281                                 return NT_STATUS_INVALID_PARAMETER;
 282                         }
 283                 }
 284         }
 285
 286         gss_maj = gss_release_buffer_set(&gss_min, &set);
 287         return NT_STATUS_OK;
 288 }
 289
 290
 291 char *gssapi_error_string(TALLOC_CTX *mem_ctx,
 292                           OM_uint32 maj_stat, OM_uint32 min_stat,
 293                           const gss_OID mech)
 294 {
 295         OM_uint32 disp_min_stat, disp_maj_stat;
 296         gss_buffer_desc maj_error_message;
 297         gss_buffer_desc min_error_message;
 298         char *maj_error_string, *min_error_string;
 299         OM_uint32 msg_ctx = 0;
 300
 301         char *ret;
 302
 303         maj_error_message.value = NULL;
 304         min_error_message.value = NULL;
 305         maj_error_message.length = 0;
 306         min_error_message.length = 0;
 307
 308         disp_maj_stat = gss_display_status(&disp_min_stat, maj_stat,
 309                                            GSS_C_GSS_CODE, mech,
 310                                            &msg_ctx, &maj_error_message);
 311         if (disp_maj_stat != 0) {
 312                 maj_error_message.value = NULL;
 313                 maj_error_message.length = 0;
 314         }
 315         disp_maj_stat = gss_display_status(&disp_min_stat, min_stat,
 316                                            GSS_C_MECH_CODE, mech,
 317                                            &msg_ctx, &min_error_message);
 318         if (disp_maj_stat != 0) {
 319                 min_error_message.value = NULL;
 320                 min_error_message.length = 0;
 321         }
 322
 323         maj_error_string = talloc_strndup(mem_ctx,
 324                                           (char *)maj_error_message.value,
 325                                           maj_error_message.length);
 326
 327         min_error_string = talloc_strndup(mem_ctx,
 328                                           (char *)min_error_message.value,
 329                                           min_error_message.length);
 330
 331         ret = talloc_asprintf(mem_ctx, "%s: %s",
 332                                 maj_error_string, min_error_string);
 333
 334         talloc_free(maj_error_string);
 335         talloc_free(min_error_string);
 336
 337         gss_release_buffer(&disp_min_stat, &maj_error_message);
 338         gss_release_buffer(&disp_min_stat, &min_error_message);
 339
 340         return ret;
 341 }
 342
 343 #endif /* HAVE_KRB5 */