source3/smbd/file_access.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Check access to files based on security descriptors.
   4    Copyright (C) Jeremy Allison 2005-2006.
   5    Copyright (C) Michael Adam 2007.
   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_ACLS
  25
  26 /**
  27  * Security descriptor / NT Token level access check function.
  28  */
  29 bool can_access_file_acl(struct connection_struct *conn,
  30                          const struct smb_filename *smb_fname,
  31                          uint32_t access_mask)
  32 {
  33         NTSTATUS status;
  34         uint32_t access_granted;
  35         struct security_descriptor *secdesc = NULL;
  36         bool ret;
  37
  38         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
  39                 /* I'm sorry sir, I didn't know you were root... */
  40                 return true;
  41         }
  42
  43         if (access_mask == DELETE_ACCESS &&
  44                         VALID_STAT(smb_fname->st) &&
  45                         S_ISLNK(smb_fname->st.st_ex_mode)) {
  46                 /* We can always delete a symlink. */
  47                 return true;
  48         }
  49
  50         status = SMB_VFS_GET_NT_ACL(conn, smb_fname->base_name,
  51                                     (OWNER_SECURITY_INFORMATION |
  52                                      GROUP_SECURITY_INFORMATION |
  53                                      DACL_SECURITY_INFORMATION),
  54                                     &secdesc);
  55         if (!NT_STATUS_IS_OK(status)) {
  56                 DEBUG(5, ("Could not get acl: %s\n", nt_errstr(status)));
  57                 ret = false;
  58                 goto out;
  59         }
  60
  61         status = se_access_check(secdesc, conn->server_info->ptok,
  62                                  access_mask, &access_granted);
  63         ret = NT_STATUS_IS_OK(status);
  64  out:
  65         TALLOC_FREE(secdesc);
  66         return ret;
  67 }
  68
  69 /****************************************************************************
  70  Actually emulate the in-kernel access checking for delete access. We need
  71  this to successfully return ACCESS_DENIED on a file open for delete access.
  72 ****************************************************************************/
  73
  74 bool can_delete_file_in_directory(connection_struct *conn,
  75                                   struct smb_filename *smb_fname)
  76 {
  77         TALLOC_CTX *ctx = talloc_tos();
  78         char *dname = NULL;
  79         struct smb_filename *smb_fname_parent = NULL;
  80         NTSTATUS status;
  81         bool ret;
  82
  83         if (!CAN_WRITE(conn)) {
  84                 return False;
  85         }
  86
  87         if (!lp_acl_check_permissions(SNUM(conn))) {
  88                 /* This option means don't check. */
  89                 return true;
  90         }
  91
  92         /* Get the parent directory permission mask and owners. */
  93         if (!parent_dirname(ctx, smb_fname->base_name, &dname, NULL)) {
  94                 return False;
  95         }
  96
  97         status = create_synthetic_smb_fname(ctx, dname, NULL, NULL,
  98                                             &smb_fname_parent);
  99         if (!NT_STATUS_IS_OK(status)) {
 100                 ret = false;
 101                 goto out;
 102         }
 103
 104         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
 105                 ret = false;
 106                 goto out;
 107         }
 108
 109         /* fast paths first */
 110
 111         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
 112                 ret = false;
 113                 goto out;
 114         }
 115         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
 116                 /* I'm sorry sir, I didn't know you were root... */
 117                 ret = true;
 118                 goto out;
 119         }
 120
 121 #ifdef S_ISVTX
 122         /* sticky bit means delete only by owner of file or by root or
 123          * by owner of directory. */
 124         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
 125                 if (!VALID_STAT(smb_fname->st)) {
 126                         /* If the file doesn't already exist then
 127                          * yes we'll be able to delete it. */
 128                         ret = true;
 129                         goto out;
 130                 }
 131
 132                 /*
 133                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 134                  * for bug #3348. Don't assume owning sticky bit
 135                  * directory means write access allowed.
 136                  * Fail to delete if we're not the owner of the file,
 137                  * or the owner of the directory as we have no possible
 138                  * chance of deleting. Otherwise, go on and check the ACL.
 139                  */
 140                 if ((conn->server_info->utok.uid !=
 141                         smb_fname_parent->st.st_ex_uid) &&
 142                     (conn->server_info->utok.uid != smb_fname->st.st_ex_uid)) {
 143                         DEBUG(10,("can_delete_file_in_directory: not "
 144                                   "owner of file %s or directory %s",
 145                                   smb_fname_str_dbg(smb_fname),
 146                                   smb_fname_str_dbg(smb_fname_parent)));
 147                         ret = false;
 148                         goto out;
 149                 }
 150         }
 151 #endif
 152
 153         /* now for ACL checks */
 154
 155         /*
 156          * There's two ways to get the permission to delete a file: First by
 157          * having the DELETE bit on the file itself and second if that does
 158          * not help, by the DELETE_CHILD bit on the containing directory.
 159          *
 160          * Here we only check the directory permissions, we will
 161          * check the file DELETE permission separately.
 162          */
 163
 164         ret = can_access_file_acl(conn, smb_fname_parent, FILE_DELETE_CHILD);
 165  out:
 166         TALLOC_FREE(dname);
 167         TALLOC_FREE(smb_fname_parent);
 168         return ret;
 169 }
 170
 171 /****************************************************************************
 172  Actually emulate the in-kernel access checking for read/write access. We need
 173  this to successfully check for ability to write for dos filetimes.
 174  Note this doesn't take into account share write permissions.
 175 ****************************************************************************/
 176
 177 bool can_access_file_data(connection_struct *conn,
 178                           const struct smb_filename *smb_fname,
 179                           uint32 access_mask)
 180 {
 181         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 182                 return False;
 183         }
 184         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 185
 186         /* some fast paths first */
 187
 188         DEBUG(10,("can_access_file_data: requesting 0x%x on file %s\n",
 189                   (unsigned int)access_mask, smb_fname_str_dbg(smb_fname)));
 190
 191         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
 192                 /* I'm sorry sir, I didn't know you were root... */
 193                 return True;
 194         }
 195
 196         SMB_ASSERT(VALID_STAT(smb_fname->st));
 197
 198         /* Check primary owner access. */
 199         if (conn->server_info->utok.uid == smb_fname->st.st_ex_uid) {
 200                 switch (access_mask) {
 201                         case FILE_READ_DATA:
 202                                 return (smb_fname->st.st_ex_mode & S_IRUSR) ?
 203                                     True : False;
 204
 205                         case FILE_WRITE_DATA:
 206                                 return (smb_fname->st.st_ex_mode & S_IWUSR) ?
 207                                     True : False;
 208
 209                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 210
 211                                 if ((smb_fname->st.st_ex_mode &
 212                                         (S_IWUSR|S_IRUSR)) ==
 213                                     (S_IWUSR|S_IRUSR)) {
 214                                         return True;
 215                                 } else {
 216                                         return False;
 217                                 }
 218                 }
 219         }
 220
 221         /* now for ACL checks */
 222
 223         return can_access_file_acl(conn, smb_fname, access_mask);
 224 }
 225
 226 /****************************************************************************
 227  Userspace check for write access.
 228  Note this doesn't take into account share write permissions.
 229 ****************************************************************************/
 230
 231 bool can_write_to_file(connection_struct *conn,
 232                        const struct smb_filename *smb_fname)
 233 {
 234         return can_access_file_data(conn, smb_fname, FILE_WRITE_DATA);
 235 }
 236
 237 /****************************************************************************
 238  Check for an existing default Windows ACL on a directory.
 239 ****************************************************************************/
 240
 241 bool directory_has_default_acl(connection_struct *conn, const char *fname)
 242 {
 243         /* returns talloced off tos. */
 244         struct security_descriptor *secdesc = NULL;
 245         unsigned int i;
 246         NTSTATUS status = SMB_VFS_GET_NT_ACL(conn, fname,
 247                                 DACL_SECURITY_INFORMATION, &secdesc);
 248
 249         if (!NT_STATUS_IS_OK(status) || secdesc == NULL) {
 250                 return false;
 251         }
 252
 253         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 254                 struct security_ace *psa = &secdesc->dacl->aces[i];
 255                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 256                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 257                         TALLOC_FREE(secdesc);
 258                         return true;
 259                 }
 260         }
 261         TALLOC_FREE(secdesc);
 262         return false;
 263 }