source/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 extern struct current_user current_user;
  24
  25 #undef  DBGC_CLASS
  26 #define DBGC_CLASS DBGC_ACLS
  27
  28 static bool can_access_file_acl(struct connection_struct *conn,
  29                                 const char * fname, SMB_STRUCT_STAT *psbuf,
  30                                 uint32_t access_mask)
  31 {
  32         bool result;
  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         result = se_access_check(secdesc, current_user.nt_user_token,
  48                                  access_mask, &access_granted, &status);
  49         TALLOC_FREE(secdesc);
  50         return result;
  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_talloc(ctx,
  70                                 fname,
  71                                 &dname,
  72                                 NULL)) {
  73                 return False;
  74         }
  75         if(SMB_VFS_STAT(conn, dname, &sbuf) != 0) {
  76                 return False;
  77         }
  78
  79         /* fast paths first */
  80
  81         if (!S_ISDIR(sbuf.st_mode)) {
  82                 return False;
  83         }
  84         if (current_user.ut.uid == 0 || conn->admin_user) {
  85                 /* I'm sorry sir, I didn't know you were root... */
  86                 return True;
  87         }
  88
  89         /* Check primary owner write access. */
  90         if (current_user.ut.uid == sbuf.st_uid) {
  91                 return (sbuf.st_mode & S_IWUSR) ? True : False;
  92         }
  93
  94 #ifdef S_ISVTX
  95         /* sticky bit means delete only by owner or root. */
  96         if (sbuf.st_mode & S_ISVTX) {
  97                 SMB_STRUCT_STAT sbuf_file;
  98                 if(SMB_VFS_STAT(conn, fname, &sbuf_file) != 0) {
  99                         if (errno == ENOENT) {
 100                                 /* If the file doesn't already exist then
 101                                  * yes we'll be able to delete it. */
 102                                 return True;
 103                         }
 104                         return False;
 105                 }
 106                 /*
 107                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 108                  * for bug #3348. Don't assume owning sticky bit
 109                  * directory means write access allowed.
 110                  */
 111                 if (current_user.ut.uid != sbuf_file.st_uid) {
 112                         return False;
 113                 }
 114         }
 115 #endif
 116
 117         /* now for ACL checks */
 118
 119         return can_access_file_acl(conn, dname, &sbuf, FILE_WRITE_DATA);
 120 }
 121
 122 /****************************************************************************
 123  Actually emulate the in-kernel access checking for read/write access. We need
 124  this to successfully check for ability to write for dos filetimes.
 125  Note this doesn't take into account share write permissions.
 126 ****************************************************************************/
 127
 128 bool can_access_file(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf, uint32 access_mask)
 129 {
 130         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 131                 return False;
 132         }
 133         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 134
 135         /* some fast paths first */
 136
 137         DEBUG(10,("can_access_file: requesting 0x%x on file %s\n",
 138                 (unsigned int)access_mask, fname ));
 139
 140         if (current_user.ut.uid == 0 || conn->admin_user) {
 141                 /* I'm sorry sir, I didn't know you were root... */
 142                 return True;
 143         }
 144
 145         if (!VALID_STAT(*psbuf)) {
 146                 /* Get the file permission mask and owners. */
 147                 if(SMB_VFS_STAT(conn, fname, psbuf) != 0) {
 148                         return False;
 149                 }
 150         }
 151
 152         /* Check primary owner access. */
 153         if (current_user.ut.uid == psbuf->st_uid) {
 154                 switch (access_mask) {
 155                         case FILE_READ_DATA:
 156                                 return (psbuf->st_mode & S_IRUSR) ? True : False;
 157
 158                         case FILE_WRITE_DATA:
 159                                 return (psbuf->st_mode & S_IWUSR) ? True : False;
 160
 161                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 162
 163                                 if ((psbuf->st_mode & (S_IWUSR|S_IRUSR)) == (S_IWUSR|S_IRUSR)) {
 164                                         return True;
 165                                 } else {
 166                                         return False;
 167                                 }
 168                 }
 169         }
 170
 171         /* now for ACL checks */
 172
 173         return can_access_file_acl(conn, fname, psbuf, access_mask);
 174 }
 175
 176 /****************************************************************************
 177  Userspace check for write access.
 178  Note this doesn't take into account share write permissions.
 179 ****************************************************************************/
 180
 181 bool can_write_to_file(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf)
 182 {
 183         return can_access_file(conn, fname, psbuf, FILE_WRITE_DATA);
 184 }
 185