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 (get_current_uid(conn) == (uid_t)0) {
  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, get_current_nttok(conn),
  55                                  access_mask, &access_granted);
  56         ret = NT_STATUS_IS_OK(status);
  57
  58         if (DEBUGLEVEL >= 10) {
  59                 DEBUG(10,("can_access_file_acl for file %s "
  60                         "access_mask 0x%x, access_granted 0x%x "
  61                         "access %s\n",
  62                         smb_fname_str_dbg(smb_fname),
  63                         (unsigned int)access_mask,
  64                         (unsigned int)access_granted,
  65                         ret ? "ALLOWED" : "DENIED" ));
  66                 NDR_PRINT_DEBUG(security_descriptor, secdesc);
  67         }
  68  out:
  69         TALLOC_FREE(secdesc);
  70         return ret;
  71 }
  72
  73 /****************************************************************************
  74  Actually emulate the in-kernel access checking for delete access. We need
  75  this to successfully return ACCESS_DENIED on a file open for delete access.
  76 ****************************************************************************/
  77
  78 bool can_delete_file_in_directory(connection_struct *conn,
  79                                   struct smb_filename *smb_fname)
  80 {
  81         TALLOC_CTX *ctx = talloc_tos();
  82         char *dname = NULL;
  83         struct smb_filename *smb_fname_parent = NULL;
  84         NTSTATUS status;
  85         bool ret;
  86
  87         if (!CAN_WRITE(conn)) {
  88                 return False;
  89         }
  90
  91         /* Get the parent directory permission mask and owners. */
  92         if (!parent_dirname(ctx, smb_fname->base_name, &dname, NULL)) {
  93                 return False;
  94         }
  95
  96         status = create_synthetic_smb_fname(ctx, dname, NULL, NULL,
  97                                             &smb_fname_parent);
  98         if (!NT_STATUS_IS_OK(status)) {
  99                 ret = false;
 100                 goto out;
 101         }
 102
 103         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
 104                 ret = false;
 105                 goto out;
 106         }
 107
 108         /* fast paths first */
 109
 110         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
 111                 ret = false;
 112                 goto out;
 113         }
 114         if (get_current_uid(conn) == (uid_t)0) {
 115                 /* I'm sorry sir, I didn't know you were root... */
 116                 ret = true;
 117                 goto out;
 118         }
 119
 120 #ifdef S_ISVTX
 121         /* sticky bit means delete only by owner of file or by root or
 122          * by owner of directory. */
 123         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
 124                 if(SMB_VFS_STAT(conn, smb_fname) != 0) {
 125                         if (errno == ENOENT) {
 126                                 /* If the file doesn't already exist then
 127                                  * yes we'll be able to delete it. */
 128                                 ret = true;
 129                                 goto out;
 130                         }
 131                         DEBUG(10,("can_delete_file_in_directory: can't "
 132                                   "stat file %s (%s)",
 133                                   smb_fname_str_dbg(smb_fname),
 134                                   strerror(errno) ));
 135                         ret = false;
 136                         goto out;
 137                 }
 138
 139                 /*
 140                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 141                  * for bug #3348. Don't assume owning sticky bit
 142                  * directory means write access allowed.
 143                  * Fail to delete if we're not the owner of the file,
 144                  * or the owner of the directory as we have no possible
 145                  * chance of deleting. Otherwise, go on and check the ACL.
 146                  */
 147                 if ((get_current_uid(conn) !=
 148                         smb_fname_parent->st.st_ex_uid) &&
 149                     (get_current_uid(conn) != smb_fname->st.st_ex_uid)) {
 150                         DEBUG(10,("can_delete_file_in_directory: not "
 151                                   "owner of file %s or directory %s",
 152                                   smb_fname_str_dbg(smb_fname),
 153                                   smb_fname_str_dbg(smb_fname_parent)));
 154                         ret = false;
 155                         goto out;
 156                 }
 157         }
 158 #endif
 159
 160         /* now for ACL checks */
 161
 162         /*
 163          * There's two ways to get the permission to delete a file: First by
 164          * having the DELETE bit on the file itself and second if that does
 165          * not help, by the DELETE_CHILD bit on the containing directory.
 166          *
 167          * Here we only check the directory permissions, we will
 168          * check the file DELETE permission separately.
 169          */
 170
 171         ret = can_access_file_acl(conn, smb_fname_parent, FILE_DELETE_CHILD);
 172  out:
 173         TALLOC_FREE(dname);
 174         TALLOC_FREE(smb_fname_parent);
 175         return ret;
 176 }
 177
 178 /****************************************************************************
 179  Actually emulate the in-kernel access checking for read/write access. We need
 180  this to successfully check for ability to write for dos filetimes.
 181  Note this doesn't take into account share write permissions.
 182 ****************************************************************************/
 183
 184 bool can_access_file_data(connection_struct *conn,
 185                           const struct smb_filename *smb_fname,
 186                           uint32 access_mask)
 187 {
 188         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 189                 return False;
 190         }
 191         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 192
 193         /* some fast paths first */
 194
 195         DEBUG(10,("can_access_file_data: requesting 0x%x on file %s\n",
 196                   (unsigned int)access_mask, smb_fname_str_dbg(smb_fname)));
 197
 198         if (get_current_uid(conn) == (uid_t)0) {
 199                 /* I'm sorry sir, I didn't know you were root... */
 200                 return True;
 201         }
 202
 203         SMB_ASSERT(VALID_STAT(smb_fname->st));
 204
 205         /* Check primary owner access. */
 206         if (get_current_uid(conn) == smb_fname->st.st_ex_uid) {
 207                 switch (access_mask) {
 208                         case FILE_READ_DATA:
 209                                 return (smb_fname->st.st_ex_mode & S_IRUSR) ?
 210                                     True : False;
 211
 212                         case FILE_WRITE_DATA:
 213                                 return (smb_fname->st.st_ex_mode & S_IWUSR) ?
 214                                     True : False;
 215
 216                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 217
 218                                 if ((smb_fname->st.st_ex_mode &
 219                                         (S_IWUSR|S_IRUSR)) ==
 220                                     (S_IWUSR|S_IRUSR)) {
 221                                         return True;
 222                                 } else {
 223                                         return False;
 224                                 }
 225                 }
 226         }
 227
 228         /* now for ACL checks */
 229
 230         return can_access_file_acl(conn, smb_fname, access_mask);
 231 }
 232
 233 /****************************************************************************
 234  Userspace check for write access.
 235  Note this doesn't take into account share write permissions.
 236 ****************************************************************************/
 237
 238 bool can_write_to_file(connection_struct *conn,
 239                        const struct smb_filename *smb_fname)
 240 {
 241         return can_access_file_data(conn, smb_fname, FILE_WRITE_DATA);
 242 }
 243
 244 /****************************************************************************
 245  Check for an existing default Windows ACL on a directory.
 246 ****************************************************************************/
 247
 248 bool directory_has_default_acl(connection_struct *conn, const char *fname)
 249 {
 250         /* returns talloced off tos. */
 251         struct security_descriptor *secdesc = NULL;
 252         unsigned int i;
 253         NTSTATUS status = SMB_VFS_GET_NT_ACL(conn, fname,
 254                                 DACL_SECURITY_INFORMATION, &secdesc);
 255
 256         if (!NT_STATUS_IS_OK(status) || secdesc == NULL) {
 257                 return false;
 258         }
 259
 260         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 261                 struct security_ace *psa = &secdesc->dacl->aces[i];
 262                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 263                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 264                         TALLOC_FREE(secdesc);
 265                         return true;
 266                 }
 267         }
 268         TALLOC_FREE(secdesc);
 269         return false;
 270 }