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 #include "system/filesys.h"
  23 #include "../libcli/security/security.h"
  24 #include "../librpc/gen_ndr/ndr_security.h"
  25 #include "smbd/smbd.h"
  26 #include "source3/smbd/dir.h"
  27
  28 #undef  DBGC_CLASS
  29 #define DBGC_CLASS DBGC_ACLS
  30
  31 /****************************************************************************
  32  Actually emulate the in-kernel access checking for delete access. We need
  33  this to successfully return ACCESS_DENIED on a file open for delete access.
  34 ****************************************************************************/
  35
  36 bool can_delete_file_in_directory(connection_struct *conn,
  37                         struct files_struct *dirfsp,
  38                         const struct smb_filename *smb_fname)
  39 {
  40         struct smb_filename *smb_fname_parent = NULL;
  41         bool ret;
  42         NTSTATUS status;
  43
  44         if (!CAN_WRITE(conn)) {
  45                 return False;
  46         }
  47
  48         if (!lp_acl_check_permissions(SNUM(conn))) {
  49                 /* This option means don't check. */
  50                 return true;
  51         }
  52
  53         if (get_current_uid(conn) == (uid_t)0) {
  54                 /* I'm sorry sir, I didn't know you were root... */
  55                 return true;
  56         }
  57
  58         if (dirfsp != conn->cwd_fsp) {
  59                 smb_fname_parent = dirfsp->fsp_name;
  60         } else {
  61                 struct smb_filename *atname = NULL;
  62                 /*
  63                  * Get a pathref on the parent.
  64                  */
  65                 status = parent_pathref(talloc_tos(),
  66                                         conn->cwd_fsp,
  67                                         smb_fname,
  68                                         &smb_fname_parent,
  69                                         &atname);
  70                 if (!NT_STATUS_IS_OK(status)) {
  71                         return false;
  72                 }
  73         }
  74
  75         SMB_ASSERT(VALID_STAT(smb_fname_parent->st));
  76
  77         /* fast paths first */
  78
  79         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
  80                 ret = false;
  81                 goto out;
  82         }
  83
  84 #ifdef S_ISVTX
  85         /* sticky bit means delete only by owner of file or by root or
  86          * by owner of directory. */
  87         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
  88                 if (!VALID_STAT(smb_fname->st)) {
  89                         /* If the file doesn't already exist then
  90                          * yes we'll be able to delete it. */
  91                         ret = true;
  92                         goto out;
  93                 }
  94
  95                 /*
  96                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
  97                  * for bug #3348. Don't assume owning sticky bit
  98                  * directory means write access allowed.
  99                  * Fail to delete if we're not the owner of the file,
 100                  * or the owner of the directory as we have no possible
 101                  * chance of deleting. Otherwise, go on and check the ACL.
 102                  */
 103                 if ((get_current_uid(conn) !=
 104                         smb_fname_parent->st.st_ex_uid) &&
 105                     (get_current_uid(conn) != smb_fname->st.st_ex_uid)) {
 106                         DEBUG(10,("can_delete_file_in_directory: not "
 107                                   "owner of file %s or directory %s\n",
 108                                   smb_fname_str_dbg(smb_fname),
 109                                   smb_fname_str_dbg(smb_fname_parent)));
 110                         ret = false;
 111                         goto out;
 112                 }
 113         }
 114 #endif
 115
 116         /* now for ACL checks */
 117
 118         /*
 119          * There's two ways to get the permission to delete a file: First by
 120          * having the DELETE bit on the file itself and second if that does
 121          * not help, by the DELETE_CHILD bit on the containing directory.
 122          *
 123          * Here we only check the directory permissions, we will
 124          * check the file DELETE permission separately.
 125          */
 126
 127         ret = NT_STATUS_IS_OK(smbd_check_access_rights_fsp(
 128                                 conn->cwd_fsp,
 129                                 smb_fname_parent->fsp,
 130                                 false,
 131                                 FILE_DELETE_CHILD));
 132  out:
 133         if (smb_fname_parent != dirfsp->fsp_name) {
 134                 TALLOC_FREE(smb_fname_parent);
 135         }
 136         return ret;
 137 }
 138
 139 /****************************************************************************
 140  Userspace check for write access to fsp.
 141 ****************************************************************************/
 142
 143 bool can_write_to_fsp(struct files_struct *fsp)
 144 {
 145         return NT_STATUS_IS_OK(smbd_check_access_rights_fsp(
 146                                                         fsp->conn->cwd_fsp,
 147                                                         fsp,
 148                                                         false,
 149                                                         FILE_WRITE_DATA));
 150 }
 151
 152 /****************************************************************************
 153  Check for an existing default Windows ACL on a directory fsp.
 154 ****************************************************************************/
 155
 156 bool directory_has_default_acl_fsp(struct files_struct *fsp)
 157 {
 158         struct security_descriptor *secdesc = NULL;
 159         unsigned int i;
 160         NTSTATUS status;
 161
 162         status = SMB_VFS_FGET_NT_ACL(metadata_fsp(fsp),
 163                                 SECINFO_DACL,
 164                                 talloc_tos(),
 165                                 &secdesc);
 166
 167         if (!NT_STATUS_IS_OK(status) ||
 168             secdesc == NULL ||
 169             secdesc->dacl == NULL)
 170         {
 171                 TALLOC_FREE(secdesc);
 172                 return false;
 173         }
 174
 175         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 176                 struct security_ace *psa = &secdesc->dacl->aces[i];
 177
 178                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 179                                 SEC_ACE_FLAG_CONTAINER_INHERIT))
 180                 {
 181                         TALLOC_FREE(secdesc);
 182                         return true;
 183                 }
 184         }
 185         TALLOC_FREE(secdesc);
 186         return false;
 187 }
 188
 189 /****************************************************************************
 190  Check if setting delete on close is allowed on this fsp.
 191 ****************************************************************************/
 192
 193 NTSTATUS can_set_delete_on_close(files_struct *fsp, uint32_t dosmode)
 194 {
 195         NTSTATUS status;
 196         /*
 197          * Only allow delete on close for writable files.
 198          */
 199
 200         if ((dosmode & FILE_ATTRIBUTE_READONLY) &&
 201             !lp_delete_readonly(SNUM(fsp->conn))) {
 202                 DEBUG(10,("can_set_delete_on_close: file %s delete on close "
 203                           "flag set but file attribute is readonly.\n",
 204                           fsp_str_dbg(fsp)));
 205                 return NT_STATUS_CANNOT_DELETE;
 206         }
 207
 208         /*
 209          * Only allow delete on close for writable shares.
 210          */
 211
 212         if (!CAN_WRITE(fsp->conn)) {
 213                 DEBUG(10,("can_set_delete_on_close: file %s delete on "
 214                           "close flag set but write access denied on share.\n",
 215                           fsp_str_dbg(fsp)));
 216                 return NT_STATUS_ACCESS_DENIED;
 217         }
 218
 219         /*
 220          * Only allow delete on close for files/directories opened with delete
 221          * intent.
 222          */
 223
 224         status = check_any_access_fsp(fsp, DELETE_ACCESS);
 225         if (!NT_STATUS_IS_OK(status)) {
 226                 DBG_DEBUG("file %s delete on "
 227                           "close flag set but delete access denied.\n",
 228                           fsp_str_dbg(fsp));
 229                 return status;
 230         }
 231
 232         /* Don't allow delete on close for non-empty directories. */
 233         if (fsp->fsp_flags.is_directory) {
 234                 SMB_ASSERT(!fsp_is_alternate_stream(fsp));
 235
 236                 /* Or the root of a share. */
 237                 if (ISDOT(fsp->fsp_name->base_name)) {
 238                         DEBUG(10,("can_set_delete_on_close: can't set delete on "
 239                                   "close for the root of a share.\n"));
 240                         return NT_STATUS_ACCESS_DENIED;
 241                 }
 242
 243                 return can_delete_directory_fsp(fsp);
 244         }
 245
 246         return NT_STATUS_OK;
 247 }