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         TALLOC_CTX *ctx = talloc_tos();
  40         struct smb_filename *smb_fname_parent = NULL;
  41         bool ret;
  42
  43         SMB_ASSERT(dirfsp == conn->cwd_fsp);
  44
  45         if (!CAN_WRITE(conn)) {
  46                 return False;
  47         }
  48
  49         if (!lp_acl_check_permissions(SNUM(conn))) {
  50                 /* This option means don't check. */
  51                 return true;
  52         }
  53
  54         /* Get the parent directory permission mask and owners. */
  55         ret = parent_smb_fname(ctx, smb_fname, &smb_fname_parent, NULL);
  56         if (ret != true) {
  57                 return false;
  58         }
  59
  60         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
  61                 ret = false;
  62                 goto out;
  63         }
  64
  65         /* fast paths first */
  66
  67         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
  68                 ret = false;
  69                 goto out;
  70         }
  71         if (get_current_uid(conn) == (uid_t)0) {
  72                 /* I'm sorry sir, I didn't know you were root... */
  73                 ret = true;
  74                 goto out;
  75         }
  76
  77 #ifdef S_ISVTX
  78         /* sticky bit means delete only by owner of file or by root or
  79          * by owner of directory. */
  80         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
  81                 if (!VALID_STAT(smb_fname->st)) {
  82                         /* If the file doesn't already exist then
  83                          * yes we'll be able to delete it. */
  84                         ret = true;
  85                         goto out;
  86                 }
  87
  88                 /*
  89                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
  90                  * for bug #3348. Don't assume owning sticky bit
  91                  * directory means write access allowed.
  92                  * Fail to delete if we're not the owner of the file,
  93                  * or the owner of the directory as we have no possible
  94                  * chance of deleting. Otherwise, go on and check the ACL.
  95                  */
  96                 if ((get_current_uid(conn) !=
  97                         smb_fname_parent->st.st_ex_uid) &&
  98                     (get_current_uid(conn) != smb_fname->st.st_ex_uid)) {
  99                         DEBUG(10,("can_delete_file_in_directory: not "
 100                                   "owner of file %s or directory %s",
 101                                   smb_fname_str_dbg(smb_fname),
 102                                   smb_fname_str_dbg(smb_fname_parent)));
 103                         ret = false;
 104                         goto out;
 105                 }
 106         }
 107 #endif
 108
 109         /* now for ACL checks */
 110
 111         /*
 112          * There's two ways to get the permission to delete a file: First by
 113          * having the DELETE bit on the file itself and second if that does
 114          * not help, by the DELETE_CHILD bit on the containing directory.
 115          *
 116          * Here we only check the directory permissions, we will
 117          * check the file DELETE permission separately.
 118          */
 119
 120         /*
 121          * NB. When dirfsp != conn->cwd_fsp, we must
 122          * change smb_fname_parent to be "." for the name here.
 123          */
 124         ret = NT_STATUS_IS_OK(smbd_check_access_rights(conn,
 125                                 dirfsp,
 126                                 smb_fname_parent,
 127                                 false,
 128                                 FILE_DELETE_CHILD));
 129  out:
 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                         struct files_struct *dirfsp,
 140                         const struct smb_filename *smb_fname)
 141 {
 142         SMB_ASSERT(dirfsp == conn->cwd_fsp);
 143         return NT_STATUS_IS_OK(smbd_check_access_rights(conn,
 144                                 dirfsp,
 145                                 smb_fname,
 146                                 false,
 147                                 FILE_WRITE_DATA));
 148 }
 149
 150 /****************************************************************************
 151  Check for an existing default Windows ACL on a directory.
 152 ****************************************************************************/
 153
 154 bool directory_has_default_acl(connection_struct *conn,
 155                 struct files_struct *dirfsp,
 156                 struct smb_filename *smb_fname)
 157 {
 158         struct security_descriptor *secdesc = NULL;
 159         unsigned int i;
 160         NTSTATUS status;
 161
 162         status = SMB_VFS_GET_NT_ACL_AT(conn,
 163                                 dirfsp,
 164                                 smb_fname,
 165                                 SECINFO_DACL,
 166                                 talloc_tos(),
 167                                 &secdesc);
 168
 169         if (!NT_STATUS_IS_OK(status) ||
 170                         secdesc == NULL ||
 171                         secdesc->dacl == NULL) {
 172                 TALLOC_FREE(secdesc);
 173                 return false;
 174         }
 175
 176         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 177                 struct security_ace *psa = &secdesc->dacl->aces[i];
 178                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 179                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 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(!is_ntfs_stream_smb_fname(fsp->fsp_name));
 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 }