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