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