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         size_t secdesc_size;
  45
  46         if (!VALID_STAT(*psbuf)) {
  47                 if (SMB_VFS_STAT(conn, fname, psbuf) != 0) {
  48                         return map_nt_error_from_unix(errno);
  49                 }
  50         }
  51
  52         /* fake a files_struct ptr: */
  53
  54         status = open_file_stat(conn, NULL, fname, psbuf, &fsp);
  55         /* Perhaps it is a directory */
  56         if (NT_STATUS_EQUAL(status, NT_STATUS_FILE_IS_A_DIRECTORY)) {
  57                 status = open_directory(conn, NULL, fname, psbuf,
  58                                         READ_CONTROL_ACCESS,
  59                                         FILE_SHARE_READ|FILE_SHARE_WRITE,
  60                                         FILE_OPEN,
  61                                         0,
  62                                         FILE_ATTRIBUTE_DIRECTORY,
  63                                         NULL, &fsp);
  64         }
  65         if (!NT_STATUS_IS_OK(status)) {
  66                 DEBUG(3, ("Unable to open file %s: %s\n", fname,
  67                           nt_errstr(status)));
  68                 return status;
  69         }
  70
  71         secdesc_size = SMB_VFS_GET_NT_ACL(fsp, fname,
  72                                           (OWNER_SECURITY_INFORMATION |
  73                                            GROUP_SECURITY_INFORMATION |
  74                                            DACL_SECURITY_INFORMATION),
  75                                           &secdesc);
  76         if (secdesc_size == 0) {
  77                 DEBUG(5, ("Unable to get NT ACL for file %s\n", fname));
  78                 return NT_STATUS_ACCESS_DENIED;
  79         }
  80
  81         *psd = talloc_move(mem_ctx, &secdesc);
  82         close_file(fsp, NORMAL_CLOSE);
  83         return NT_STATUS_OK;
  84 }
  85
  86 static bool can_access_file_acl(struct connection_struct *conn,
  87                                 const char * fname, SMB_STRUCT_STAT *psbuf,
  88                                 uint32_t access_mask)
  89 {
  90         bool result;
  91         NTSTATUS status;
  92         uint32_t access_granted;
  93         struct security_descriptor *secdesc = NULL;
  94
  95         status = conn_get_nt_acl(talloc_tos(), conn, fname, psbuf, &secdesc);
  96         if (!NT_STATUS_IS_OK(status)) {
  97                 DEBUG(5, ("Could not get acl: %s\n", nt_errstr(status)));
  98                 return false;
  99         }
 100
 101         result = se_access_check(secdesc, current_user.nt_user_token,
 102                                  access_mask, &access_granted, &status);
 103         TALLOC_FREE(secdesc);
 104         return result;
 105 }
 106
 107 /****************************************************************************
 108  Actually emulate the in-kernel access checking for delete access. We need
 109  this to successfully return ACCESS_DENIED on a file open for delete access.
 110 ****************************************************************************/
 111
 112 bool can_delete_file_in_directory(connection_struct *conn, const char *fname)
 113 {
 114         SMB_STRUCT_STAT sbuf;
 115         TALLOC_CTX *ctx = talloc_tos();
 116         char *dname = NULL;
 117
 118         if (!CAN_WRITE(conn)) {
 119                 return False;
 120         }
 121
 122         /* Get the parent directory permission mask and owners. */
 123         if (!parent_dirname_talloc(ctx,
 124                                 fname,
 125                                 &dname,
 126                                 NULL)) {
 127                 return False;
 128         }
 129         if(SMB_VFS_STAT(conn, dname, &sbuf) != 0) {
 130                 return False;
 131         }
 132
 133         /* fast paths first */
 134
 135         if (!S_ISDIR(sbuf.st_mode)) {
 136                 return False;
 137         }
 138         if (current_user.ut.uid == 0 || conn->admin_user) {
 139                 /* I'm sorry sir, I didn't know you were root... */
 140                 return True;
 141         }
 142
 143         /* Check primary owner write access. */
 144         if (current_user.ut.uid == sbuf.st_uid) {
 145                 return (sbuf.st_mode & S_IWUSR) ? True : False;
 146         }
 147
 148 #ifdef S_ISVTX
 149         /* sticky bit means delete only by owner or root. */
 150         if (sbuf.st_mode & S_ISVTX) {
 151                 SMB_STRUCT_STAT sbuf_file;
 152                 if(SMB_VFS_STAT(conn, fname, &sbuf_file) != 0) {
 153                         if (errno == ENOENT) {
 154                                 /* If the file doesn't already exist then
 155                                  * yes we'll be able to delete it. */
 156                                 return True;
 157                         }
 158                         return False;
 159                 }
 160                 /*
 161                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 162                  * for bug #3348. Don't assume owning sticky bit
 163                  * directory means write access allowed.
 164                  */
 165                 if (current_user.ut.uid != sbuf_file.st_uid) {
 166                         return False;
 167                 }
 168         }
 169 #endif
 170
 171         /* now for ACL checks */
 172
 173         return can_access_file_acl(conn, dname, &sbuf, FILE_WRITE_DATA);
 174 }
 175
 176 /****************************************************************************
 177  Actually emulate the in-kernel access checking for read/write access. We need
 178  this to successfully check for ability to write for dos filetimes.
 179  Note this doesn't take into account share write permissions.
 180 ****************************************************************************/
 181
 182 bool can_access_file(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf, uint32 access_mask)
 183 {
 184         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 185                 return False;
 186         }
 187         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 188
 189         /* some fast paths first */
 190
 191         DEBUG(10,("can_access_file: requesting 0x%x on file %s\n",
 192                 (unsigned int)access_mask, fname ));
 193
 194         if (current_user.ut.uid == 0 || conn->admin_user) {
 195                 /* I'm sorry sir, I didn't know you were root... */
 196                 return True;
 197         }
 198
 199         if (!VALID_STAT(*psbuf)) {
 200                 /* Get the file permission mask and owners. */
 201                 if(SMB_VFS_STAT(conn, fname, psbuf) != 0) {
 202                         return False;
 203                 }
 204         }
 205
 206         /* Check primary owner access. */
 207         if (current_user.ut.uid == psbuf->st_uid) {
 208                 switch (access_mask) {
 209                         case FILE_READ_DATA:
 210                                 return (psbuf->st_mode & S_IRUSR) ? True : False;
 211
 212                         case FILE_WRITE_DATA:
 213                                 return (psbuf->st_mode & S_IWUSR) ? True : False;
 214
 215                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 216
 217                                 if ((psbuf->st_mode & (S_IWUSR|S_IRUSR)) == (S_IWUSR|S_IRUSR)) {
 218                                         return True;
 219                                 } else {
 220                                         return False;
 221                                 }
 222                 }
 223         }
 224
 225         /* now for ACL checks */
 226
 227         return can_access_file_acl(conn, fname, psbuf, access_mask);
 228 }
 229
 230 /****************************************************************************
 231  Userspace check for write access.
 232  Note this doesn't take into account share write permissions.
 233 ****************************************************************************/
 234
 235 bool can_write_to_file(connection_struct *conn, const char *fname, SMB_STRUCT_STAT *psbuf)
 236 {
 237         return can_access_file(conn, fname, psbuf, FILE_WRITE_DATA);
 238 }
 239