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
  23 #undef  DBGC_CLASS
  24 #define DBGC_CLASS DBGC_ACLS
  25
  26 /**
  27  * Security descriptor / NT Token level access check function.
  28  */
  29 bool can_access_file_acl(struct connection_struct *conn,
  30                          const struct smb_filename *smb_fname,
  31                          uint32_t access_mask)
  32 {
  33         NTSTATUS status;
  34         uint32_t access_granted;
  35         struct security_descriptor *secdesc = NULL;
  36         char *fname = NULL;
  37         bool ret;
  38
  39         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
  40                 /* I'm sorry sir, I didn't know you were root... */
  41                 return true;
  42         }
  43
  44         status = get_full_smb_filename(talloc_tos(), smb_fname, &fname);
  45         if (!NT_STATUS_IS_OK(status)) {
  46                 ret = false;
  47                 goto out;
  48         }
  49
  50         status = SMB_VFS_GET_NT_ACL(conn, fname,
  51                                     (OWNER_SECURITY_INFORMATION |
  52                                      GROUP_SECURITY_INFORMATION |
  53                                      DACL_SECURITY_INFORMATION),
  54                                     &secdesc);
  55         if (!NT_STATUS_IS_OK(status)) {
  56                 DEBUG(5, ("Could not get acl: %s\n", nt_errstr(status)));
  57                 ret = false;
  58                 goto out;
  59         }
  60
  61         status = se_access_check(secdesc, conn->server_info->ptok,
  62                                  access_mask, &access_granted);
  63         ret = NT_STATUS_IS_OK(status);
  64  out:
  65         TALLOC_FREE(fname);
  66         TALLOC_FREE(secdesc);
  67         return ret;
  68 }
  69
  70 /****************************************************************************
  71  Actually emulate the in-kernel access checking for delete access. We need
  72  this to successfully return ACCESS_DENIED on a file open for delete access.
  73 ****************************************************************************/
  74
  75 bool can_delete_file_in_directory(connection_struct *conn,
  76                                   struct smb_filename *smb_fname)
  77 {
  78         TALLOC_CTX *ctx = talloc_tos();
  79         char *dname = NULL;
  80         struct smb_filename *smb_fname_parent = NULL;
  81         NTSTATUS status;
  82         bool ret;
  83
  84         if (!CAN_WRITE(conn)) {
  85                 return False;
  86         }
  87
  88         /* Get the parent directory permission mask and owners. */
  89         if (!parent_dirname(ctx, smb_fname->base_name, &dname, NULL)) {
  90                 return False;
  91         }
  92
  93         status = create_synthetic_smb_fname(ctx, dname, NULL, NULL,
  94                                             &smb_fname_parent);
  95         if (!NT_STATUS_IS_OK(status)) {
  96                 ret = false;
  97                 goto out;
  98         }
  99
 100         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
 101                 ret = false;
 102                 goto out;
 103         }
 104
 105         /* fast paths first */
 106
 107         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
 108                 ret = false;
 109                 goto out;
 110         }
 111         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
 112                 /* I'm sorry sir, I didn't know you were root... */
 113                 ret = true;
 114                 goto out;
 115         }
 116
 117 #ifdef S_ISVTX
 118         /* sticky bit means delete only by owner of file or by root or
 119          * by owner of directory. */
 120         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
 121                 if(SMB_VFS_STAT(conn, smb_fname) != 0) {
 122                         if (errno == ENOENT) {
 123                                 /* If the file doesn't already exist then
 124                                  * yes we'll be able to delete it. */
 125                                 ret = true;
 126                                 goto out;
 127                         }
 128                         DEBUG(10,("can_delete_file_in_directory: can't "
 129                                   "stat file %s (%s)",
 130                                   smb_fname_str_dbg(smb_fname),
 131                                   strerror(errno) ));
 132                         ret = false;
 133                         goto out;
 134                 }
 135
 136                 /*
 137                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 138                  * for bug #3348. Don't assume owning sticky bit
 139                  * directory means write access allowed.
 140                  * Fail to delete if we're not the owner of the file,
 141                  * or the owner of the directory as we have no possible
 142                  * chance of deleting. Otherwise, go on and check the ACL.
 143                  */
 144                 if ((conn->server_info->utok.uid !=
 145                         smb_fname_parent->st.st_ex_uid) &&
 146                     (conn->server_info->utok.uid != smb_fname->st.st_ex_uid)) {
 147                         DEBUG(10,("can_delete_file_in_directory: not "
 148                                   "owner of file %s or directory %s",
 149                                   smb_fname_str_dbg(smb_fname),
 150                                   smb_fname_str_dbg(smb_fname_parent)));
 151                         ret = false;
 152                         goto out;
 153                 }
 154         }
 155 #endif
 156
 157         /* now for ACL checks */
 158
 159         /*
 160          * There's two ways to get the permission to delete a file: First by
 161          * having the DELETE bit on the file itself and second if that does
 162          * not help, by the DELETE_CHILD bit on the containing directory.
 163          *
 164          * Here we only check the directory permissions, we will
 165          * check the file DELETE permission separately.
 166          */
 167
 168         ret = can_access_file_acl(conn, smb_fname_parent, FILE_DELETE_CHILD);
 169  out:
 170         TALLOC_FREE(dname);
 171         TALLOC_FREE(smb_fname_parent);
 172         return ret;
 173 }
 174
 175 /****************************************************************************
 176  Actually emulate the in-kernel access checking for read/write access. We need
 177  this to successfully check for ability to write for dos filetimes.
 178  Note this doesn't take into account share write permissions.
 179 ****************************************************************************/
 180
 181 bool can_access_file_data(connection_struct *conn,
 182                           const struct smb_filename *smb_fname,
 183                           uint32 access_mask)
 184 {
 185         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 186                 return False;
 187         }
 188         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 189
 190         /* some fast paths first */
 191
 192         DEBUG(10,("can_access_file_data: requesting 0x%x on file %s\n",
 193                   (unsigned int)access_mask, smb_fname_str_dbg(smb_fname)));
 194
 195         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
 196                 /* I'm sorry sir, I didn't know you were root... */
 197                 return True;
 198         }
 199
 200         SMB_ASSERT(VALID_STAT(smb_fname->st));
 201
 202         /* Check primary owner access. */
 203         if (conn->server_info->utok.uid == smb_fname->st.st_ex_uid) {
 204                 switch (access_mask) {
 205                         case FILE_READ_DATA:
 206                                 return (smb_fname->st.st_ex_mode & S_IRUSR) ?
 207                                     True : False;
 208
 209                         case FILE_WRITE_DATA:
 210                                 return (smb_fname->st.st_ex_mode & S_IWUSR) ?
 211                                     True : False;
 212
 213                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 214
 215                                 if ((smb_fname->st.st_ex_mode &
 216                                         (S_IWUSR|S_IRUSR)) ==
 217                                     (S_IWUSR|S_IRUSR)) {
 218                                         return True;
 219                                 } else {
 220                                         return False;
 221                                 }
 222                 }
 223         }
 224
 225         /* now for ACL checks */
 226
 227         return can_access_file_acl(conn, smb_fname, access_mask);
 228 }
 229
 230 /****************************************************************************
 231  Userspace check for write access.
 232  Note this doesn't take into account share write permissions.
 233 ****************************************************************************/
 234
 235 bool can_write_to_file(connection_struct *conn,
 236                        const struct smb_filename *smb_fname)
 237 {
 238         return can_access_file_data(conn, smb_fname, FILE_WRITE_DATA);
 239 }
 240
 241 /****************************************************************************
 242  Check for an existing default Windows ACL on a directory.
 243 ****************************************************************************/
 244
 245 bool directory_has_default_acl(connection_struct *conn, const char *fname)
 246 {
 247         /* returns talloced off tos. */
 248         struct security_descriptor *secdesc = NULL;
 249         unsigned int i;
 250         NTSTATUS status = SMB_VFS_GET_NT_ACL(conn, fname,
 251                                 DACL_SECURITY_INFORMATION, &secdesc);
 252
 253         if (!NT_STATUS_IS_OK(status) || secdesc == NULL) {
 254                 return false;
 255         }
 256
 257         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 258                 struct security_ace *psa = &secdesc->dacl->aces[i];
 259                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 260                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 261                         TALLOC_FREE(secdesc);
 262                         return true;
 263                 }
 264         }
 265         TALLOC_FREE(secdesc);
 266         return false;
 267 }