libcli/security/access_check.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Copyright (C) Andrew Tridgell 2004
   5    Copyright (C) Gerald Carter 2005
   6    Copyright (C) Volker Lendecke 2007
   7    Copyright (C) Jeremy Allison 2008
   8    Copyright (C) Andrew Bartlett 2010
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 3 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  22 */
  23
  24 #include "includes.h"
  25 #include "libcli/security/security.h"
  26
  27 /* Map generic access rights to object specific rights.  This technique is
  28    used to give meaning to assigning read, write, execute and all access to
  29    objects.  Each type of object has its own mapping of generic to object
  30    specific access rights. */
  31
  32 void se_map_generic(uint32_t *access_mask, const struct generic_mapping *mapping)
  33 {
  34         uint32_t old_mask = *access_mask;
  35
  36         if (*access_mask & GENERIC_READ_ACCESS) {
  37                 *access_mask &= ~GENERIC_READ_ACCESS;
  38                 *access_mask |= mapping->generic_read;
  39         }
  40
  41         if (*access_mask & GENERIC_WRITE_ACCESS) {
  42                 *access_mask &= ~GENERIC_WRITE_ACCESS;
  43                 *access_mask |= mapping->generic_write;
  44         }
  45
  46         if (*access_mask & GENERIC_EXECUTE_ACCESS) {
  47                 *access_mask &= ~GENERIC_EXECUTE_ACCESS;
  48                 *access_mask |= mapping->generic_execute;
  49         }
  50
  51         if (*access_mask & GENERIC_ALL_ACCESS) {
  52                 *access_mask &= ~GENERIC_ALL_ACCESS;
  53                 *access_mask |= mapping->generic_all;
  54         }
  55
  56         if (old_mask != *access_mask) {
  57                 DEBUG(10, ("se_map_generic(): mapped mask 0x%08x to 0x%08x\n",
  58                            old_mask, *access_mask));
  59         }
  60 }
  61
  62 /* Map generic access rights to object specific rights for all the ACE's
  63  * in a security_acl.
  64  */
  65
  66 void security_acl_map_generic(struct security_acl *sa,
  67                                 const struct generic_mapping *mapping)
  68 {
  69         unsigned int i;
  70
  71         if (!sa) {
  72                 return;
  73         }
  74
  75         for (i = 0; i < sa->num_aces; i++) {
  76                 se_map_generic(&sa->aces[i].access_mask, mapping);
  77         }
  78 }
  79
  80 /* Map standard access rights to object specific rights.  This technique is
  81    used to give meaning to assigning read, write, execute and all access to
  82    objects.  Each type of object has its own mapping of standard to object
  83    specific access rights. */
  84
  85 void se_map_standard(uint32_t *access_mask, const struct standard_mapping *mapping)
  86 {
  87         uint32_t old_mask = *access_mask;
  88
  89         if (*access_mask & SEC_STD_READ_CONTROL) {
  90                 *access_mask &= ~SEC_STD_READ_CONTROL;
  91                 *access_mask |= mapping->std_read;
  92         }
  93
  94         if (*access_mask & (SEC_STD_DELETE|SEC_STD_WRITE_DAC|SEC_STD_WRITE_OWNER|SEC_STD_SYNCHRONIZE)) {
  95                 *access_mask &= ~(SEC_STD_DELETE|SEC_STD_WRITE_DAC|SEC_STD_WRITE_OWNER|SEC_STD_SYNCHRONIZE);
  96                 *access_mask |= mapping->std_all;
  97         }
  98
  99         if (old_mask != *access_mask) {
 100                 DEBUG(10, ("se_map_standard(): mapped mask 0x%08x to 0x%08x\n",
 101                            old_mask, *access_mask));
 102         }
 103 }
 104
 105 /*
 106   perform a SEC_FLAG_MAXIMUM_ALLOWED access check
 107 */
 108 static uint32_t access_check_max_allowed(const struct security_descriptor *sd,
 109                                         const struct security_token *token)
 110 {
 111         uint32_t denied = 0, granted = 0;
 112         unsigned i;
 113
 114         if (security_token_has_sid(token, sd->owner_sid)) {
 115                 granted |= SEC_STD_WRITE_DAC | SEC_STD_READ_CONTROL;
 116         }
 117
 118         if (sd->dacl == NULL) {
 119                 return granted & ~denied;
 120         }
 121
 122         for (i = 0;i<sd->dacl->num_aces; i++) {
 123                 struct security_ace *ace = &sd->dacl->aces[i];
 124
 125                 if (ace->flags & SEC_ACE_FLAG_INHERIT_ONLY) {
 126                         continue;
 127                 }
 128
 129                 if (!security_token_has_sid(token, &ace->trustee)) {
 130                         continue;
 131                 }
 132
 133                 switch (ace->type) {
 134                 case SEC_ACE_TYPE_ACCESS_ALLOWED:
 135                         granted |= ace->access_mask;
 136                         break;
 137                 case SEC_ACE_TYPE_ACCESS_DENIED:
 138                 case SEC_ACE_TYPE_ACCESS_DENIED_OBJECT:
 139                         denied |= ace->access_mask;
 140                         break;
 141                 default:        /* Other ACE types not handled/supported */
 142                         break;
 143                 }
 144         }
 145
 146         return granted & ~denied;
 147 }
 148
 149 /*
 150   The main entry point for access checking. If returning ACCESS_DENIED
 151   this function returns the denied bits in the uint32_t pointed
 152   to by the access_granted pointer.
 153 */
 154 NTSTATUS se_access_check(const struct security_descriptor *sd,
 155                           const struct security_token *token,
 156                           uint32_t access_desired,
 157                           uint32_t *access_granted)
 158 {
 159         uint32_t i;
 160         uint32_t bits_remaining;
 161         uint32_t explicitly_denied_bits = 0;
 162
 163         *access_granted = access_desired;
 164         bits_remaining = access_desired;
 165
 166         /* handle the maximum allowed flag */
 167         if (access_desired & SEC_FLAG_MAXIMUM_ALLOWED) {
 168                 uint32_t orig_access_desired = access_desired;
 169
 170                 access_desired |= access_check_max_allowed(sd, token);
 171                 access_desired &= ~SEC_FLAG_MAXIMUM_ALLOWED;
 172                 *access_granted = access_desired;
 173                 bits_remaining = access_desired;
 174
 175                 DEBUG(10,("se_access_check: MAX desired = 0x%x, granted = 0x%x, remaining = 0x%x\n",
 176                         orig_access_desired,
 177                         *access_granted,
 178                         bits_remaining));
 179         }
 180
 181         /* s3 had this with #if 0 previously. To be sure the merge
 182            doesn't change any behaviour, we have the above #if check
 183            on _SAMBA_BUILD_. */
 184         if (access_desired & SEC_FLAG_SYSTEM_SECURITY) {
 185                 if (security_token_has_privilege(token, SEC_PRIV_SECURITY)) {
 186                         bits_remaining &= ~SEC_FLAG_SYSTEM_SECURITY;
 187                 } else {
 188                         return NT_STATUS_PRIVILEGE_NOT_HELD;
 189                 }
 190         }
 191
 192         /* the owner always gets SEC_STD_WRITE_DAC and SEC_STD_READ_CONTROL */
 193         if ((bits_remaining & (SEC_STD_WRITE_DAC|SEC_STD_READ_CONTROL)) &&
 194             security_token_has_sid(token, sd->owner_sid)) {
 195                 bits_remaining &= ~(SEC_STD_WRITE_DAC|SEC_STD_READ_CONTROL);
 196         }
 197
 198         /* TODO: remove this, as it is file server specific */
 199         if ((bits_remaining & SEC_RIGHTS_PRIV_RESTORE) &&
 200             security_token_has_privilege(token, SEC_PRIV_RESTORE)) {
 201                 bits_remaining &= ~(SEC_RIGHTS_PRIV_RESTORE);
 202         }
 203         if ((bits_remaining & SEC_RIGHTS_PRIV_BACKUP) &&
 204             security_token_has_privilege(token, SEC_PRIV_BACKUP)) {
 205                 bits_remaining &= ~(SEC_RIGHTS_PRIV_BACKUP);
 206         }
 207
 208         /* a NULL dacl allows access */
 209         if ((sd->type & SEC_DESC_DACL_PRESENT) && sd->dacl == NULL) {
 210                 *access_granted = access_desired;
 211                 return NT_STATUS_OK;
 212         }
 213
 214         if (sd->dacl == NULL) {
 215                 goto done;
 216         }
 217
 218         /* check each ace in turn. */
 219         for (i=0; bits_remaining && i < sd->dacl->num_aces; i++) {
 220                 struct security_ace *ace = &sd->dacl->aces[i];
 221
 222                 if (ace->flags & SEC_ACE_FLAG_INHERIT_ONLY) {
 223                         continue;
 224                 }
 225
 226                 if (!security_token_has_sid(token, &ace->trustee)) {
 227                         continue;
 228                 }
 229
 230                 switch (ace->type) {
 231                 case SEC_ACE_TYPE_ACCESS_ALLOWED:
 232                         bits_remaining &= ~ace->access_mask;
 233                         break;
 234                 case SEC_ACE_TYPE_ACCESS_DENIED:
 235                 case SEC_ACE_TYPE_ACCESS_DENIED_OBJECT:
 236                         explicitly_denied_bits |= (bits_remaining & ace->access_mask);
 237                         break;
 238                 default:        /* Other ACE types not handled/supported */
 239                         break;
 240                 }
 241         }
 242
 243         bits_remaining |= explicitly_denied_bits;
 244
 245 done:
 246         if (bits_remaining != 0) {
 247                 *access_granted = bits_remaining;
 248                 return NT_STATUS_ACCESS_DENIED;
 249         }
 250
 251         return NT_STATUS_OK;
 252 }
 253
 254
 255 static const struct GUID *get_ace_object_type(struct security_ace *ace)
 256 {
 257         struct GUID *type;
 258
 259         if (ace->object.object.flags & SEC_ACE_OBJECT_TYPE_PRESENT)
 260                 type = &ace->object.object.type.type;
 261         else if (ace->object.object.flags & SEC_ACE_INHERITED_OBJECT_TYPE_PRESENT)
 262                 type = &ace->object.object.inherited_type.inherited_type; /* This doesn't look right. Is something wrong with the IDL? */
 263         else
 264                 type = NULL;
 265
 266         return type;
 267
 268 }
 269
 270 /* modified access check for the purposes of DS security
 271  * Lots of code duplication, it will ve united in just one
 272  * function eventually */
 273
 274 NTSTATUS sec_access_check_ds(const struct security_descriptor *sd,
 275                              const struct security_token *token,
 276                              uint32_t access_desired,
 277                              uint32_t *access_granted,
 278                              struct object_tree *tree,
 279                              struct dom_sid *replace_sid)
 280 {
 281         uint32_t i;
 282         uint32_t bits_remaining;
 283         struct object_tree *node;
 284         const struct GUID *type;
 285         struct dom_sid *ps_sid = dom_sid_parse_talloc(NULL, SID_NT_SELF);
 286
 287         *access_granted = access_desired;
 288         bits_remaining = access_desired;
 289
 290         /* handle the maximum allowed flag */
 291         if (access_desired & SEC_FLAG_MAXIMUM_ALLOWED) {
 292                 access_desired |= access_check_max_allowed(sd, token);
 293                 access_desired &= ~SEC_FLAG_MAXIMUM_ALLOWED;
 294                 *access_granted = access_desired;
 295                 bits_remaining = access_desired;
 296         }
 297
 298         if (access_desired & SEC_FLAG_SYSTEM_SECURITY) {
 299                 if (security_token_has_privilege(token, SEC_PRIV_SECURITY)) {
 300                         bits_remaining &= ~SEC_FLAG_SYSTEM_SECURITY;
 301                 } else {
 302                         talloc_free(ps_sid);
 303                         return NT_STATUS_PRIVILEGE_NOT_HELD;
 304                 }
 305         }
 306
 307         /* the owner always gets SEC_STD_WRITE_DAC and SEC_STD_READ_CONTROL */
 308         if ((bits_remaining & (SEC_STD_WRITE_DAC|SEC_STD_READ_CONTROL)) &&
 309             security_token_has_sid(token, sd->owner_sid)) {
 310                 bits_remaining &= ~(SEC_STD_WRITE_DAC|SEC_STD_READ_CONTROL);
 311         }
 312
 313         /* TODO: remove this, as it is file server specific */
 314         if ((bits_remaining & SEC_RIGHTS_PRIV_RESTORE) &&
 315             security_token_has_privilege(token, SEC_PRIV_RESTORE)) {
 316                 bits_remaining &= ~(SEC_RIGHTS_PRIV_RESTORE);
 317         }
 318         if ((bits_remaining & SEC_RIGHTS_PRIV_BACKUP) &&
 319             security_token_has_privilege(token, SEC_PRIV_BACKUP)) {
 320                 bits_remaining &= ~(SEC_RIGHTS_PRIV_BACKUP);
 321         }
 322
 323         /* a NULL dacl allows access */
 324         if ((sd->type & SEC_DESC_DACL_PRESENT) && sd->dacl == NULL) {
 325                 *access_granted = access_desired;
 326                 talloc_free(ps_sid);
 327                 return NT_STATUS_OK;
 328         }
 329
 330         if (sd->dacl == NULL) {
 331                 goto done;
 332         }
 333
 334         /* check each ace in turn. */
 335         for (i=0; bits_remaining && i < sd->dacl->num_aces; i++) {
 336                 struct dom_sid *trustee;
 337                 struct security_ace *ace = &sd->dacl->aces[i];
 338
 339                 if (ace->flags & SEC_ACE_FLAG_INHERIT_ONLY) {
 340                         continue;
 341                 }
 342                 if (dom_sid_equal(&ace->trustee, ps_sid) && replace_sid) {
 343                         trustee = replace_sid;
 344                 }
 345                 else
 346                 {
 347                         trustee = &ace->trustee;
 348                 }
 349                 if (!security_token_has_sid(token, trustee)) {
 350                         continue;
 351                 }
 352
 353                 switch (ace->type) {
 354                 case SEC_ACE_TYPE_ACCESS_ALLOWED:
 355                         if (tree)
 356                                 object_tree_modify_access(tree, ace->access_mask);
 357
 358                         bits_remaining &= ~ace->access_mask;
 359                         break;
 360                 case SEC_ACE_TYPE_ACCESS_DENIED:
 361                         if (bits_remaining & ace->access_mask) {
 362                                 talloc_free(ps_sid);
 363                                 return NT_STATUS_ACCESS_DENIED;
 364                         }
 365                         break;
 366                 case SEC_ACE_TYPE_ACCESS_DENIED_OBJECT:
 367                 case SEC_ACE_TYPE_ACCESS_ALLOWED_OBJECT:
 368                         /* check only in case we have provided a tree,
 369                          * the ACE has an object type and that type
 370                          * is in the tree                           */
 371                         type = get_ace_object_type(ace);
 372
 373                         if (!tree)
 374                                 continue;
 375
 376                         if (!type)
 377                                 node = tree;
 378                         else
 379                                 if (!(node = get_object_tree_by_GUID(tree, type)))
 380                                         continue;
 381
 382                         if (ace->type == SEC_ACE_TYPE_ACCESS_ALLOWED_OBJECT) {
 383                                 object_tree_modify_access(node, ace->access_mask);
 384                                 if (node->remaining_access == 0) {
 385                                         talloc_free(ps_sid);
 386                                         return NT_STATUS_OK;
 387                                 }
 388                         } else {
 389                                 if (node->remaining_access & ace->access_mask){
 390                                         talloc_free(ps_sid);
 391                                         return NT_STATUS_ACCESS_DENIED;
 392                                 }
 393                         }
 394                         break;
 395                 default:        /* Other ACE types not handled/supported */
 396                         break;
 397                 }
 398         }
 399
 400 done:
 401         talloc_free(ps_sid);
 402         if (bits_remaining != 0) {
 403                 return NT_STATUS_ACCESS_DENIED;
 404         }
 405
 406         return NT_STATUS_OK;
 407 }