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 char * fname,
  31                                 uint32_t access_mask)
  32 {
  33         NTSTATUS status;
  34         uint32_t access_granted;
  35         struct security_descriptor *secdesc = NULL;
  36
  37         status = SMB_VFS_GET_NT_ACL(conn, fname,
  38                                     (OWNER_SECURITY_INFORMATION |
  39                                      GROUP_SECURITY_INFORMATION |
  40                                      DACL_SECURITY_INFORMATION),
  41                                     &secdesc);
  42         if (!NT_STATUS_IS_OK(status)) {
  43                 DEBUG(5, ("Could not get acl: %s\n", nt_errstr(status)));
  44                 return false;
  45         }
  46
  47         status = se_access_check(secdesc, conn->server_info->ptok,
  48                                  access_mask, &access_granted);
  49         TALLOC_FREE(secdesc);
  50         return NT_STATUS_IS_OK(status);
  51 }
  52
  53 /****************************************************************************
  54  Actually emulate the in-kernel access checking for delete access. We need
  55  this to successfully return ACCESS_DENIED on a file open for delete access.
  56 ****************************************************************************/
  57
  58 bool can_delete_file_in_directory(connection_struct *conn, const char *fname)
  59 {
  60         SMB_STRUCT_STAT sbuf;
  61         TALLOC_CTX *ctx = talloc_tos();
  62         char *dname = NULL;
  63
  64         if (!CAN_WRITE(conn)) {
  65                 return False;
  66         }
  67
  68         /* Get the parent directory permission mask and owners. */
  69         if (!parent_dirname(ctx, fname, &dname, NULL)) {
  70                 return False;
  71         }
  72         if(SMB_VFS_STAT(conn, dname, &sbuf) != 0) {
  73                 return False;
  74         }
  75
  76         /* fast paths first */
  77
  78         if (!S_ISDIR(sbuf.st_mode)) {
  79                 return False;
  80         }
  81         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
  82                 /* I'm sorry sir, I didn't know you were root... */
  83                 return True;
  84         }
  85
  86 #ifdef S_ISVTX
  87         /* sticky bit means delete only by owner or root. */
  88         if (sbuf.st_mode & S_ISVTX) {
  89                 SMB_STRUCT_STAT sbuf_file;
  90                 if(SMB_VFS_STAT(conn, fname, &sbuf_file) != 0) {
  91                         if (errno == ENOENT) {
  92                                 /* If the file doesn't already exist then
  93                                  * yes we'll be able to delete it. */
  94                                 return True;
  95                         }
  96                         return False;
  97                 }
  98                 /*
  99                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 100                  * for bug #3348. Don't assume owning sticky bit
 101                  * directory means write access allowed.
 102                  */
 103                 if (conn->server_info->utok.uid != sbuf_file.st_uid) {
 104                         return False;
 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         return can_access_file_acl(conn, dname, FILE_DELETE_CHILD);
 121 }
 122
 123 /****************************************************************************
 124  Actually emulate the in-kernel access checking for read/write access. We need
 125  this to successfully check for ability to write for dos filetimes.
 126  Note this doesn't take into account share write permissions.
 127 ****************************************************************************/
 128
 129 bool can_access_file_data(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf, uint32 access_mask)
 130 {
 131         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 132                 return False;
 133         }
 134         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 135
 136         /* some fast paths first */
 137
 138         DEBUG(10,("can_access_file_data: requesting 0x%x on file %s\n",
 139                 (unsigned int)access_mask, fname ));
 140
 141         if (conn->server_info->utok.uid == 0 || conn->admin_user) {
 142                 /* I'm sorry sir, I didn't know you were root... */
 143                 return True;
 144         }
 145
 146         if (!VALID_STAT(*psbuf)) {
 147                 /* Get the file permission mask and owners. */
 148                 if(SMB_VFS_STAT(conn, fname, psbuf) != 0) {
 149                         return False;
 150                 }
 151         }
 152
 153         /* Check primary owner access. */
 154         if (conn->server_info->utok.uid == psbuf->st_uid) {
 155                 switch (access_mask) {
 156                         case FILE_READ_DATA:
 157                                 return (psbuf->st_mode & S_IRUSR) ? True : False;
 158
 159                         case FILE_WRITE_DATA:
 160                                 return (psbuf->st_mode & S_IWUSR) ? True : False;
 161
 162                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 163
 164                                 if ((psbuf->st_mode & (S_IWUSR|S_IRUSR)) == (S_IWUSR|S_IRUSR)) {
 165                                         return True;
 166                                 } else {
 167                                         return False;
 168                                 }
 169                 }
 170         }
 171
 172         /* now for ACL checks */
 173
 174         return can_access_file_acl(conn, fname, access_mask);
 175 }
 176
 177 /****************************************************************************
 178  Userspace check for write access.
 179  Note this doesn't take into account share write permissions.
 180 ****************************************************************************/
 181
 182 bool can_write_to_file(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf)
 183 {
 184         return can_access_file_data(conn, fname, psbuf, FILE_WRITE_DATA);
 185 }
 186
 187 /****************************************************************************
 188  Check for an existing default Windows ACL on a directory.
 189 ****************************************************************************/
 190
 191 bool directory_has_default_acl(connection_struct *conn, const char *fname)
 192 {
 193         /* returns talloced off tos. */
 194         struct security_descriptor *secdesc = NULL;
 195         unsigned int i;
 196         NTSTATUS status = SMB_VFS_GET_NT_ACL(conn, fname,
 197                                 DACL_SECURITY_INFORMATION, &secdesc);
 198
 199         if (!NT_STATUS_IS_OK(status) || secdesc == NULL) {
 200                 return false;
 201         }
 202
 203         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 204                 struct security_ace *psa = &secdesc->dacl->aces[i];
 205                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 206                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 207                         TALLOC_FREE(secdesc);
 208                         return true;
 209                 }
 210         }
 211         TALLOC_FREE(secdesc);
 212         return false;
 213 }