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 /****************************************************************************
  29  Helper function that gets a security descriptor by connection and
  30  file name.
  31  NOTE: This is transitional, in the sense that SMB_VFS_GET_NT_ACL really
  32  should *not* get a files_struct pointer but a connection_struct ptr
  33  (automatic by the vfs handle) and the file name and _use_ that!
  34 ****************************************************************************/
  35 static NTSTATUS conn_get_nt_acl(TALLOC_CTX *mem_ctx,
  36                                 struct connection_struct *conn,
  37                                 const char *fname,
  38                                 SMB_STRUCT_STAT *psbuf,
  39                                 struct security_descriptor **psd)
  40 {
  41         NTSTATUS status;
  42         struct files_struct *fsp = NULL;
  43         struct security_descriptor *secdesc = NULL;
  44
  45         if (!VALID_STAT(*psbuf)) {
  46                 if (SMB_VFS_STAT(conn, fname, psbuf) != 0) {
  47                         return map_nt_error_from_unix(errno);
  48                 }
  49         }
  50
  51         /* fake a files_struct ptr: */
  52
  53         if (S_ISDIR(psbuf->st_mode)) {
  54                 status = open_directory(conn, NULL, fname, psbuf,
  55                                         READ_CONTROL_ACCESS,
  56                                         FILE_SHARE_READ|FILE_SHARE_WRITE,
  57                                         FILE_OPEN,
  58                                         0,
  59                                         FILE_ATTRIBUTE_DIRECTORY,
  60                                         NULL, &fsp);
  61         }
  62         else {
  63                 status = open_file_stat(conn, NULL, fname, psbuf, &fsp);
  64         }
  65
  66         if (!NT_STATUS_IS_OK(status)) {
  67                 DEBUG(3, ("Unable to open file %s: %s\n", fname,
  68                           nt_errstr(status)));
  69                 return status;
  70         }
  71
  72         status = SMB_VFS_GET_NT_ACL(fsp, fname,
  73                                     (OWNER_SECURITY_INFORMATION |
  74                                      GROUP_SECURITY_INFORMATION |
  75                                      DACL_SECURITY_INFORMATION),
  76                                     &secdesc);
  77         if (!NT_STATUS_IS_OK(status)) {
  78                 DEBUG(5, ("Unable to get NT ACL for file %s\n", fname));
  79                 goto done;
  80         }
  81
  82         *psd = talloc_move(mem_ctx, &secdesc);
  83
  84 done:
  85         close_file(fsp, NORMAL_CLOSE);
  86         return status;
  87 }
  88
  89 static bool can_access_file_acl(struct connection_struct *conn,
  90                                 const char * fname, SMB_STRUCT_STAT *psbuf,
  91                                 uint32_t access_mask)
  92 {
  93         bool result;
  94         NTSTATUS status;
  95         uint32_t access_granted;
  96         struct security_descriptor *secdesc = NULL;
  97
  98         status = conn_get_nt_acl(talloc_tos(), conn, fname, psbuf, &secdesc);
  99         if (!NT_STATUS_IS_OK(status)) {
 100                 DEBUG(5, ("Could not get acl: %s\n", nt_errstr(status)));
 101                 return false;
 102         }
 103
 104         result = se_access_check(secdesc, current_user.nt_user_token,
 105                                  access_mask, &access_granted, &status);
 106         TALLOC_FREE(secdesc);
 107         return result;
 108 }
 109
 110 /****************************************************************************
 111  Actually emulate the in-kernel access checking for delete access. We need
 112  this to successfully return ACCESS_DENIED on a file open for delete access.
 113 ****************************************************************************/
 114
 115 bool can_delete_file_in_directory(connection_struct *conn, const char *fname)
 116 {
 117         SMB_STRUCT_STAT sbuf;
 118         TALLOC_CTX *ctx = talloc_tos();
 119         char *dname = NULL;
 120
 121         if (!CAN_WRITE(conn)) {
 122                 return False;
 123         }
 124
 125         /* Get the parent directory permission mask and owners. */
 126         if (!parent_dirname_talloc(ctx,
 127                                 fname,
 128                                 &dname,
 129                                 NULL)) {
 130                 return False;
 131         }
 132         if(SMB_VFS_STAT(conn, dname, &sbuf) != 0) {
 133                 return False;
 134         }
 135
 136         /* fast paths first */
 137
 138         if (!S_ISDIR(sbuf.st_mode)) {
 139                 return False;
 140         }
 141         if (current_user.ut.uid == 0 || conn->admin_user) {
 142                 /* I'm sorry sir, I didn't know you were root... */
 143                 return True;
 144         }
 145
 146         /* Check primary owner write access. */
 147         if (current_user.ut.uid == sbuf.st_uid) {
 148                 return (sbuf.st_mode & S_IWUSR) ? True : False;
 149         }
 150
 151 #ifdef S_ISVTX
 152         /* sticky bit means delete only by owner or root. */
 153         if (sbuf.st_mode & S_ISVTX) {
 154                 SMB_STRUCT_STAT sbuf_file;
 155                 if(SMB_VFS_STAT(conn, fname, &sbuf_file) != 0) {
 156                         if (errno == ENOENT) {
 157                                 /* If the file doesn't already exist then
 158                                  * yes we'll be able to delete it. */
 159                                 return True;
 160                         }
 161                         return False;
 162                 }
 163                 /*
 164                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 165                  * for bug #3348. Don't assume owning sticky bit
 166                  * directory means write access allowed.
 167                  */
 168                 if (current_user.ut.uid != sbuf_file.st_uid) {
 169                         return False;
 170                 }
 171         }
 172 #endif
 173
 174         /* now for ACL checks */
 175
 176         return can_access_file_acl(conn, dname, &sbuf, FILE_WRITE_DATA);
 177 }
 178
 179 /****************************************************************************
 180  Actually emulate the in-kernel access checking for read/write access. We need
 181  this to successfully check for ability to write for dos filetimes.
 182  Note this doesn't take into account share write permissions.
 183 ****************************************************************************/
 184
 185 bool can_access_file(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf, uint32 access_mask)
 186 {
 187         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 188                 return False;
 189         }
 190         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 191
 192         /* some fast paths first */
 193
 194         DEBUG(10,("can_access_file: requesting 0x%x on file %s\n",
 195                 (unsigned int)access_mask, fname ));
 196
 197         if (current_user.ut.uid == 0 || conn->admin_user) {
 198                 /* I'm sorry sir, I didn't know you were root... */
 199                 return True;
 200         }
 201
 202         if (!VALID_STAT(*psbuf)) {
 203                 /* Get the file permission mask and owners. */
 204                 if(SMB_VFS_STAT(conn, fname, psbuf) != 0) {
 205                         return False;
 206                 }
 207         }
 208
 209         /* Check primary owner access. */
 210         if (current_user.ut.uid == psbuf->st_uid) {
 211                 switch (access_mask) {
 212                         case FILE_READ_DATA:
 213                                 return (psbuf->st_mode & S_IRUSR) ? True : False;
 214
 215                         case FILE_WRITE_DATA:
 216                                 return (psbuf->st_mode & S_IWUSR) ? True : False;
 217
 218                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 219
 220                                 if ((psbuf->st_mode & (S_IWUSR|S_IRUSR)) == (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, fname, psbuf, 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, const char *fname, SMB_STRUCT_STAT *psbuf)
 239 {
 240         return can_access_file(conn, fname, psbuf, FILE_WRITE_DATA);
 241 }
 242