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 = NULL;
  41         NTSTATUS status;
  42         bool ret;
  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         /* Get the parent directory permission mask and owners. */
  54         if (!parent_dirname(ctx, smb_fname->base_name, &dname, NULL)) {
  55                 return False;
  56         }
  57
  58         status = create_synthetic_smb_fname(ctx, dname, NULL, NULL,
  59                                             &smb_fname_parent);
  60         if (!NT_STATUS_IS_OK(status)) {
  61                 ret = false;
  62                 goto out;
  63         }
  64
  65         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
  66                 ret = false;
  67                 goto out;
  68         }
  69
  70         /* fast paths first */
  71
  72         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
  73                 ret = false;
  74                 goto out;
  75         }
  76         if (get_current_uid(conn) == (uid_t)0) {
  77                 /* I'm sorry sir, I didn't know you were root... */
  78                 ret = true;
  79                 goto out;
  80         }
  81
  82 #ifdef S_ISVTX
  83         /* sticky bit means delete only by owner of file or by root or
  84          * by owner of directory. */
  85         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
  86                 if (!VALID_STAT(smb_fname->st)) {
  87                         /* If the file doesn't already exist then
  88                          * yes we'll be able to delete it. */
  89                         ret = true;
  90                         goto out;
  91                 }
  92
  93                 /*
  94                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
  95                  * for bug #3348. Don't assume owning sticky bit
  96                  * directory means write access allowed.
  97                  * Fail to delete if we're not the owner of the file,
  98                  * or the owner of the directory as we have no possible
  99                  * chance of deleting. Otherwise, go on and check the ACL.
 100                  */
 101                 if ((get_current_uid(conn) !=
 102                         smb_fname_parent->st.st_ex_uid) &&
 103                     (get_current_uid(conn) != smb_fname->st.st_ex_uid)) {
 104                         DEBUG(10,("can_delete_file_in_directory: not "
 105                                   "owner of file %s or directory %s",
 106                                   smb_fname_str_dbg(smb_fname),
 107                                   smb_fname_str_dbg(smb_fname_parent)));
 108                         ret = false;
 109                         goto out;
 110                 }
 111         }
 112 #endif
 113
 114         /* now for ACL checks */
 115
 116         /*
 117          * There's two ways to get the permission to delete a file: First by
 118          * having the DELETE bit on the file itself and second if that does
 119          * not help, by the DELETE_CHILD bit on the containing directory.
 120          *
 121          * Here we only check the directory permissions, we will
 122          * check the file DELETE permission separately.
 123          */
 124
 125         ret = NT_STATUS_IS_OK(smbd_check_access_rights(conn,
 126                                 smb_fname_parent,
 127                                 FILE_DELETE_CHILD));
 128  out:
 129         TALLOC_FREE(dname);
 130         TALLOC_FREE(smb_fname_parent);
 131         return ret;
 132 }
 133
 134 /****************************************************************************
 135  Userspace check for write access.
 136 ****************************************************************************/
 137
 138 bool can_write_to_file(connection_struct *conn,
 139                        const struct smb_filename *smb_fname)
 140 {
 141         return NT_STATUS_IS_OK(smbd_check_access_rights(conn,
 142                                 smb_fname,
 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         /* returns talloced off tos. */
 153         struct security_descriptor *secdesc = NULL;
 154         unsigned int i;
 155         NTSTATUS status = SMB_VFS_GET_NT_ACL(conn, fname,
 156                                 SECINFO_DACL, &secdesc);
 157
 158         if (!NT_STATUS_IS_OK(status) || secdesc == NULL) {
 159                 return false;
 160         }
 161
 162         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 163                 struct security_ace *psa = &secdesc->dacl->aces[i];
 164                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 165                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 166                         TALLOC_FREE(secdesc);
 167                         return true;
 168                 }
 169         }
 170         TALLOC_FREE(secdesc);
 171         return false;
 172 }