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,
  58                                 dname,
  59                                 NULL,
  60                                 NULL,
  61                                 smb_fname->flags);
  62         if (smb_fname_parent == NULL) {
  63                 ret = false;
  64                 goto out;
  65         }
  66
  67         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
  68                 ret = false;
  69                 goto out;
  70         }
  71
  72         /* fast paths first */
  73
  74         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
  75                 ret = false;
  76                 goto out;
  77         }
  78         if (get_current_uid(conn) == (uid_t)0) {
  79                 /* I'm sorry sir, I didn't know you were root... */
  80                 ret = true;
  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",
 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(conn,
 128                                 smb_fname_parent,
 129                                 false,
 130                                 FILE_DELETE_CHILD));
 131  out:
 132         TALLOC_FREE(dname);
 133         TALLOC_FREE(smb_fname_parent);
 134         return ret;
 135 }
 136
 137 /****************************************************************************
 138  Userspace check for write access.
 139 ****************************************************************************/
 140
 141 bool can_write_to_file(connection_struct *conn,
 142                        const struct smb_filename *smb_fname)
 143 {
 144         return NT_STATUS_IS_OK(smbd_check_access_rights(conn,
 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, const char *fname)
 155 {
 156         struct security_descriptor *secdesc = NULL;
 157         unsigned int i;
 158         NTSTATUS status;
 159         struct smb_filename *smb_fname = synthetic_smb_fname(talloc_tos(),
 160                                                 fname,
 161                                                 NULL,
 162                                                 NULL,
 163                                                 0);
 164
 165         if (smb_fname == NULL) {
 166                 return false;
 167         }
 168
 169         status = SMB_VFS_GET_NT_ACL(conn, smb_fname,
 170                                              SECINFO_DACL, talloc_tos(),
 171                                              &secdesc);
 172
 173         if (!NT_STATUS_IS_OK(status) ||
 174                         secdesc == NULL ||
 175                         secdesc->dacl == NULL) {
 176                 TALLOC_FREE(secdesc);
 177                 return false;
 178         }
 179
 180         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 181                 struct security_ace *psa = &secdesc->dacl->aces[i];
 182                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 183                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 184                         TALLOC_FREE(secdesc);
 185                         return true;
 186                 }
 187         }
 188         TALLOC_FREE(secdesc);
 189         return false;
 190 }
 191
 192 /****************************************************************************
 193  Check if setting delete on close is allowed on this fsp.
 194 ****************************************************************************/
 195
 196 NTSTATUS can_set_delete_on_close(files_struct *fsp, uint32_t dosmode)
 197 {
 198         /*
 199          * Only allow delete on close for writable files.
 200          */
 201
 202         if ((dosmode & FILE_ATTRIBUTE_READONLY) &&
 203             !lp_delete_readonly(SNUM(fsp->conn))) {
 204                 DEBUG(10,("can_set_delete_on_close: file %s delete on close "
 205                           "flag set but file attribute is readonly.\n",
 206                           fsp_str_dbg(fsp)));
 207                 return NT_STATUS_CANNOT_DELETE;
 208         }
 209
 210         /*
 211          * Only allow delete on close for writable shares.
 212          */
 213
 214         if (!CAN_WRITE(fsp->conn)) {
 215                 DEBUG(10,("can_set_delete_on_close: file %s delete on "
 216                           "close flag set but write access denied on share.\n",
 217                           fsp_str_dbg(fsp)));
 218                 return NT_STATUS_ACCESS_DENIED;
 219         }
 220
 221         /*
 222          * Only allow delete on close for files/directories opened with delete
 223          * intent.
 224          */
 225
 226         if (!(fsp->access_mask & DELETE_ACCESS)) {
 227                 DEBUG(10,("can_set_delete_on_close: file %s delete on "
 228                           "close flag set but delete access denied.\n",
 229                           fsp_str_dbg(fsp)));
 230                 return NT_STATUS_ACCESS_DENIED;
 231         }
 232
 233         /* Don't allow delete on close for non-empty directories. */
 234         if (fsp->is_directory) {
 235                 SMB_ASSERT(!is_ntfs_stream_smb_fname(fsp->fsp_name));
 236
 237                 /* Or the root of a share. */
 238                 if (ISDOT(fsp->fsp_name->base_name)) {
 239                         DEBUG(10,("can_set_delete_on_close: can't set delete on "
 240                                   "close for the root of a share.\n"));
 241                         return NT_STATUS_ACCESS_DENIED;
 242                 }
 243
 244                 return can_delete_directory_fsp(fsp);
 245         }
 246
 247         return NT_STATUS_OK;
 248 }