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