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
  23 #undef DBGC_CLASS
  24 #define DBGC_CLASS DBGC_AUTH
  25
  26 #ifdef HAVE_KRB5
  27
  28 #include "auth/kerberos/pac_utils.h"
  29
  30 #if 0
  31 /* FIXME - need proper configure/waf test
  32  * to determine if gss_mech_krb5 and friends
  33  * exist. JRA.
  34  */
  35 /*
  36  * These are not exported by Solaris -lkrb5
  37  * Maybe move to libreplace somewhere?
  38  */
  39 static const gss_OID_desc krb5_gss_oid_array[] = {
  40         /* this is the official, rfc-specified OID */
  41         { 9, "\052\206\110\206\367\022\001\002\002" },
  42         /* this is the pre-RFC mech OID */
  43         { 5, "\053\005\001\005\002" },
  44         /* this is the unofficial, incorrect mech OID emitted by MS */
  45         { 9, "\052\206\110\202\367\022\001\002\002" },
  46         { 0, 0 }
  47 };
  48
  49 const gss_OID_desc * const gss_mech_krb5              = krb5_gss_oid_array+0;
  50 const gss_OID_desc * const gss_mech_krb5_old          = krb5_gss_oid_array+1;
  51 const gss_OID_desc * const gss_mech_krb5_wrong        = krb5_gss_oid_array+2;
  52 #endif
  53
  54 #ifndef GSS_KRB5_INQ_SSPI_SESSION_KEY_OID
  55 #define GSS_KRB5_INQ_SSPI_SESSION_KEY_OID_LENGTH 11
  56 #define GSS_KRB5_INQ_SSPI_SESSION_KEY_OID "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x05\x05"
  57 #endif
  58
  59 gss_OID_desc gse_sesskey_inq_oid = {
  60         GSS_KRB5_INQ_SSPI_SESSION_KEY_OID_LENGTH,
  61         discard_const(GSS_KRB5_INQ_SSPI_SESSION_KEY_OID)
  62 };
  63
  64 #ifndef GSS_KRB5_SESSION_KEY_ENCTYPE_OID
  65 #define GSS_KRB5_SESSION_KEY_ENCTYPE_OID_LENGTH 10
  66 #define GSS_KRB5_SESSION_KEY_ENCTYPE_OID  "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x04"
  67 #endif
  68
  69 gss_OID_desc gse_sesskeytype_oid = {
  70         GSS_KRB5_SESSION_KEY_ENCTYPE_OID_LENGTH,
  71         discard_const(GSS_KRB5_SESSION_KEY_ENCTYPE_OID)
  72 };
  73
  74 /* The Heimdal OID for getting the PAC */
  75 #define EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID_LENGTH 8
  76 /*                                                      EXTRACTION OID             AUTHZ ID */
  77 #define EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID "\x2a\x85\x70\x2b\x0d\x03" "\x81\x00"
  78
  79 NTSTATUS gssapi_obtain_pac_blob(TALLOC_CTX *mem_ctx,
  80                                 gss_ctx_id_t gssapi_context,
  81                                 gss_name_t gss_client_name,
  82                                 DATA_BLOB *pac_blob)
  83 {
  84         NTSTATUS status;
  85         OM_uint32 gss_maj, gss_min;
  86 #ifdef HAVE_GSS_GET_NAME_ATTRIBUTE
  87 /*
  88  * gss_get_name_attribute() in MIT krb5 1.10.0 can return uninitialized pac_display_buffer
  89  * and later gss_release_buffer() will crash on attempting to release it.
  90  *
  91  * So always initialize the buffer descriptors.
  92  *
  93  * See following links for more details:
  94  * http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=658514
  95  * http://krbdev.mit.edu/rt/Ticket/Display.html?user=guest&pass=guest&id=7087
  96  */
  97         gss_buffer_desc pac_buffer = {
  98                 .value = NULL,
  99                 .length = 0
 100         };
 101         gss_buffer_desc pac_display_buffer = {
 102                 .value = NULL,
 103                 .length = 0
 104         };
 105         gss_buffer_desc pac_name = {
 106                 .value = discard_const("urn:mspac:"),
 107                 .length = sizeof("urn:mspac:")-1
 108         };
 109         int more = -1;
 110         int authenticated = false;
 111         int complete = false;
 112
 113         gss_maj = gss_get_name_attribute(
 114                 &gss_min, gss_client_name, &pac_name,
 115                 &authenticated, &complete,
 116                 &pac_buffer, &pac_display_buffer, &more);
 117
 118         if (gss_maj != 0) {
 119                 gss_OID oid = discard_const(gss_mech_krb5);
 120                 DBG_NOTICE("obtaining PAC via GSSAPI gss_get_name_attribute "
 121                            "failed: %s\n", gssapi_error_string(mem_ctx,
 122                                                                gss_maj, gss_min,
 123                                                                oid));
 124                 return NT_STATUS_ACCESS_DENIED;
 125         } else if (authenticated && complete) {
 126                 /* The PAC blob is returned directly */
 127                 *pac_blob = data_blob_talloc(mem_ctx, pac_buffer.value,
 128                                             pac_buffer.length);
 129
 130                 if (!pac_blob->data) {
 131                         status = NT_STATUS_NO_MEMORY;
 132                 } else {
 133                         status = NT_STATUS_OK;
 134                 }
 135
 136                 gss_release_buffer(&gss_min, &pac_buffer);
 137                 gss_release_buffer(&gss_min, &pac_display_buffer);
 138                 return status;
 139         } else {
 140                 DEBUG(0, ("obtaining PAC via GSSAPI failed: authenticated: %s, complete: %s, more: %s\n",
 141                           authenticated ? "true" : "false",
 142                           complete ? "true" : "false",
 143                           more ? "true" : "false"));
 144                 return NT_STATUS_ACCESS_DENIED;
 145         }
 146
 147 #elif defined(HAVE_GSS_INQUIRE_SEC_CONTEXT_BY_OID)
 148         gss_OID_desc pac_data_oid = {
 149                 .elements = discard_const(EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID),
 150                 .length = EXTRACT_PAC_AUTHZ_DATA_FROM_SEC_CONTEXT_OID_LENGTH
 151         };
 152
 153         gss_buffer_set_t set = GSS_C_NO_BUFFER_SET;
 154
 155         /* If we didn't have the routine to get a verified, validated
 156          * PAC (supplied only by MIT at the time of writing), then try
 157          * with the Heimdal OID (fetches the PAC directly and always
 158          * validates) */
 159         gss_maj = gss_inquire_sec_context_by_oid(
 160                                 &gss_min, gssapi_context,
 161                                 &pac_data_oid, &set);
 162
 163         /* First check for the error MIT gives for an unknown OID */
 164         if (gss_maj == GSS_S_UNAVAILABLE) {
 165                 DEBUG(1, ("unable to obtain a PAC against this GSSAPI library.  "
 166                           "GSSAPI secured connections are available only with Heimdal or MIT Kerberos >= 1.8\n"));
 167         } else if (gss_maj != 0) {
 168                 DEBUG(2, ("obtaining PAC via GSSAPI gss_inquire_sec_context_by_oid (Heimdal OID) failed: %s\n",
 169                           gssapi_error_string(mem_ctx, gss_maj, gss_min, gss_mech_krb5)));
 170         } else {
 171                 if (set == GSS_C_NO_BUFFER_SET) {
 172                         DEBUG(0, ("gss_inquire_sec_context_by_oid returned unknown "
 173                                   "data in results.\n"));
 174                         return NT_STATUS_INTERNAL_ERROR;
 175                 }
 176
 177                 /* The PAC blob is returned directly */
 178                 *pac_blob = data_blob_talloc(mem_ctx, set->elements[0].value,
 179                                             set->elements[0].length);
 180                 if (!pac_blob->data) {
 181                         status = NT_STATUS_NO_MEMORY;
 182                 } else {
 183                         status = NT_STATUS_OK;
 184                 }
 185
 186                 gss_maj = gss_release_buffer_set(&gss_min, &set);
 187                 return status;
 188         }
 189 #else
 190         DEBUG(1, ("unable to obtain a PAC against this GSSAPI library.  "
 191                   "GSSAPI secured connections are available only with Heimdal or MIT Kerberos >= 1.8\n"));
 192 #endif
 193         return NT_STATUS_ACCESS_DENIED;
 194 }
 195
 196 NTSTATUS gssapi_get_session_key(TALLOC_CTX *mem_ctx,
 197                                 gss_ctx_id_t gssapi_context,
 198                                 DATA_BLOB *session_key,
 199                                 uint32_t *keytype)
 200 {
 201         OM_uint32 gss_min, gss_maj;
 202         gss_buffer_set_t set = GSS_C_NO_BUFFER_SET;
 203
 204         gss_maj = gss_inquire_sec_context_by_oid(
 205                                 &gss_min, gssapi_context,
 206                                 &gse_sesskey_inq_oid, &set);
 207         if (gss_maj) {
 208                 DEBUG(0, ("gss_inquire_sec_context_by_oid failed [%s]\n",
 209                           gssapi_error_string(mem_ctx,
 210                                               gss_maj,
 211                                               gss_min,
 212                                               discard_const_p(struct gss_OID_desc_struct,
 213                                                               gss_mech_krb5))));
 214                 return NT_STATUS_NO_USER_SESSION_KEY;
 215         }
 216
 217         if ((set == GSS_C_NO_BUFFER_SET) ||
 218             (set->count == 0)) {
 219 #ifdef HAVE_GSSKRB5_GET_SUBKEY
 220                 krb5_keyblock *subkey;
 221                 gss_maj = gsskrb5_get_subkey(&gss_min,
 222                                              gssapi_context,
 223                                              &subkey);
 224                 if (gss_maj != 0) {
 225                         DEBUG(1, ("NO session key for this mech\n"));
 226                         return NT_STATUS_NO_USER_SESSION_KEY;
 227                 }
 228                 if (session_key) {
 229                         *session_key = data_blob_talloc(mem_ctx,
 230                                                         KRB5_KEY_DATA(subkey), KRB5_KEY_LENGTH(subkey));
 231                 }
 232                 if (keytype) {
 233                         *keytype = KRB5_KEY_TYPE(subkey);
 234                 }
 235                 krb5_free_keyblock(NULL /* should be krb5_context */, subkey);
 236                 return NT_STATUS_OK;
 237 #else
 238                 DEBUG(0, ("gss_inquire_sec_context_by_oid didn't return any session key (and no alternative method available)\n"));
 239                 return NT_STATUS_NO_USER_SESSION_KEY;
 240 #endif
 241         }
 242
 243         if (session_key) {
 244                 *session_key = data_blob_talloc(mem_ctx, set->elements[0].value,
 245                                                 set->elements[0].length);
 246         }
 247
 248         if (keytype) {
 249                 int diflen, i;
 250                 const uint8_t *p;
 251
 252                 *keytype = 0;
 253                 if (set->count < 2) {
 254
 255 #ifdef HAVE_GSSKRB5_GET_SUBKEY
 256                         krb5_keyblock *subkey;
 257                         gss_maj = gsskrb5_get_subkey(&gss_min,
 258                                                      gssapi_context,
 259                                                      &subkey);
 260                         if (gss_maj == 0) {
 261                                 *keytype = KRB5_KEY_TYPE(subkey);
 262                                 krb5_free_keyblock(NULL /* should be krb5_context */, subkey);
 263                         }
 264 #endif
 265                         gss_release_buffer_set(&gss_min, &set);
 266
 267                         return NT_STATUS_OK;
 268
 269                 } else if (memcmp(set->elements[1].value,
 270                                   gse_sesskeytype_oid.elements,
 271                                   gse_sesskeytype_oid.length) != 0) {
 272                         /* Perhaps a non-krb5 session key */
 273                         gss_release_buffer_set(&gss_min, &set);
 274                         return NT_STATUS_OK;
 275                 }
 276                 p = (const uint8_t *)set->elements[1].value + gse_sesskeytype_oid.length;
 277                 diflen = set->elements[1].length - gse_sesskeytype_oid.length;
 278                 if (diflen <= 0) {
 279                         gss_release_buffer_set(&gss_min, &set);
 280                         return NT_STATUS_INVALID_PARAMETER;
 281                 }
 282                 for (i = 0; i < diflen; i++) {
 283                         *keytype = (*keytype << 7) | (p[i] & 0x7f);
 284                         if (i + 1 != diflen && (p[i] & 0x80) == 0) {
 285                                 gss_release_buffer_set(&gss_min, &set);
 286                                 return NT_STATUS_INVALID_PARAMETER;
 287                         }
 288                 }
 289         }
 290
 291         gss_release_buffer_set(&gss_min, &set);
 292         return NT_STATUS_OK;
 293 }
 294
 295
 296 char *gssapi_error_string(TALLOC_CTX *mem_ctx,
 297                           OM_uint32 maj_stat, OM_uint32 min_stat,
 298                           const gss_OID mech)
 299 {
 300         OM_uint32 disp_min_stat, disp_maj_stat;
 301         gss_buffer_desc maj_error_message;
 302         gss_buffer_desc min_error_message;
 303         char *maj_error_string, *min_error_string;
 304         OM_uint32 msg_ctx = 0;
 305
 306         char *ret;
 307
 308         maj_error_message.value = NULL;
 309         min_error_message.value = NULL;
 310         maj_error_message.length = 0;
 311         min_error_message.length = 0;
 312
 313         disp_maj_stat = gss_display_status(&disp_min_stat, maj_stat,
 314                                            GSS_C_GSS_CODE, mech,
 315                                            &msg_ctx, &maj_error_message);
 316         if (disp_maj_stat != 0) {
 317                 maj_error_message.value = NULL;
 318                 maj_error_message.length = 0;
 319         }
 320         disp_maj_stat = gss_display_status(&disp_min_stat, min_stat,
 321                                            GSS_C_MECH_CODE, mech,
 322                                            &msg_ctx, &min_error_message);
 323         if (disp_maj_stat != 0) {
 324                 min_error_message.value = NULL;
 325                 min_error_message.length = 0;
 326         }
 327
 328         maj_error_string = talloc_strndup(mem_ctx,
 329                                           (char *)maj_error_message.value,
 330                                           maj_error_message.length);
 331
 332         min_error_string = talloc_strndup(mem_ctx,
 333                                           (char *)min_error_message.value,
 334                                           min_error_message.length);
 335
 336         ret = talloc_asprintf(mem_ctx, "%s: %s",
 337                                 maj_error_string, min_error_string);
 338
 339         talloc_free(maj_error_string);
 340         talloc_free(min_error_string);
 341
 342         gss_release_buffer(&disp_min_stat, &maj_error_message);
 343         gss_release_buffer(&disp_min_stat, &min_error_message);
 344
 345         return ret;
 346 }
 347
 348 #endif /* HAVE_KRB5 */