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 | SEC_STD_DELETE;
 116         } else if (security_token_has_privilege(token, SEC_PRIV_RESTORE)) {
 117                 granted |= SEC_STD_DELETE;
 118         }
 119
 120         if (sd->dacl == NULL) {
 121                 return granted & ~denied;
 122         }
 123
 124         for (i = 0;i<sd->dacl->num_aces; i++) {
 125                 struct security_ace *ace = &sd->dacl->aces[i];
 126
 127                 if (ace->flags & SEC_ACE_FLAG_INHERIT_ONLY) {
 128                         continue;
 129                 }
 130
 131                 if (!security_token_has_sid(token, &ace->trustee)) {
 132                         continue;
 133                 }
 134
 135                 switch (ace->type) {
 136                 case SEC_ACE_TYPE_ACCESS_ALLOWED:
 137                         granted |= ace->access_mask;
 138                         break;
 139                 case SEC_ACE_TYPE_ACCESS_DENIED:
 140                 case SEC_ACE_TYPE_ACCESS_DENIED_OBJECT:
 141                         denied |= ace->access_mask;
 142                         break;
 143                 default:        /* Other ACE types not handled/supported */
 144                         break;
 145                 }
 146         }
 147
 148         return granted & ~denied;
 149 }
 150
 151 /*
 152   The main entry point for access checking. If returning ACCESS_DENIED
 153   this function returns the denied bits in the uint32_t pointed
 154   to by the access_granted pointer.
 155 */
 156 NTSTATUS se_access_check(const struct security_descriptor *sd,
 157                           const struct security_token *token,
 158                           uint32_t access_desired,
 159                           uint32_t *access_granted)
 160 {
 161         uint32_t i;
 162         uint32_t bits_remaining;
 163
 164         *access_granted = access_desired;
 165         bits_remaining = access_desired;
 166
 167         /* handle the maximum allowed flag */
 168         if (access_desired & SEC_FLAG_MAXIMUM_ALLOWED) {
 169                 uint32_t orig_access_desired = access_desired;
 170
 171                 access_desired |= access_check_max_allowed(sd, token);
 172                 access_desired &= ~SEC_FLAG_MAXIMUM_ALLOWED;
 173                 *access_granted = access_desired;
 174                 bits_remaining = access_desired & ~SEC_STD_DELETE;
 175
 176                 DEBUG(10,("se_access_check: MAX desired = 0x%x, granted = 0x%x, remaining = 0x%x\n",
 177                         orig_access_desired,
 178                         *access_granted,
 179                         bits_remaining));
 180         }
 181
 182         if (access_desired & SEC_FLAG_SYSTEM_SECURITY) {
 183                 if (security_token_has_privilege(token, SEC_PRIV_SECURITY)) {
 184                         bits_remaining &= ~SEC_FLAG_SYSTEM_SECURITY;
 185                 } else {
 186                         return NT_STATUS_PRIVILEGE_NOT_HELD;
 187                 }
 188         }
 189
 190         /* a NULL dacl allows access */
 191         if ((sd->type & SEC_DESC_DACL_PRESENT) && sd->dacl == NULL) {
 192                 *access_granted = access_desired;
 193                 return NT_STATUS_OK;
 194         }
 195
 196         /* the owner always gets SEC_STD_WRITE_DAC, SEC_STD_READ_CONTROL and SEC_STD_DELETE */
 197         if ((bits_remaining & (SEC_STD_WRITE_DAC|SEC_STD_READ_CONTROL|SEC_STD_DELETE)) &&
 198             security_token_has_sid(token, sd->owner_sid)) {
 199                 bits_remaining &= ~(SEC_STD_WRITE_DAC|SEC_STD_READ_CONTROL|SEC_STD_DELETE);
 200         }
 201         if ((bits_remaining & SEC_STD_DELETE) &&
 202             (security_token_has_privilege(token, SEC_PRIV_RESTORE))) {
 203                 bits_remaining &= ~SEC_STD_DELETE;
 204         }
 205         if ((bits_remaining & SEC_RIGHTS_PRIV_RESTORE) &&
 206             security_token_has_privilege(token, SEC_PRIV_RESTORE)) {
 207                 bits_remaining &= ~(SEC_RIGHTS_PRIV_RESTORE);
 208         }
 209         if ((bits_remaining & SEC_RIGHTS_PRIV_BACKUP) &&
 210             security_token_has_privilege(token, SEC_PRIV_BACKUP)) {
 211                 bits_remaining &= ~(SEC_RIGHTS_PRIV_BACKUP);
 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                         if (bits_remaining & ace->access_mask) {
 237                                 return NT_STATUS_ACCESS_DENIED;
 238                         }
 239                         break;
 240                 default:        /* Other ACE types not handled/supported */
 241                         break;
 242                 }
 243         }
 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 }