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 #include "system/filesys.h"
  23 #include "../libcli/security/security.h"
  24 #include "../librpc/gen_ndr/ndr_security.h"
  25 #include "smbd/smbd.h"
  26
  27 #undef  DBGC_CLASS
  28 #define DBGC_CLASS DBGC_ACLS
  29
  30 /**
  31  * Security descriptor / NT Token level access check function.
  32  */
  33 bool can_access_file_acl(struct connection_struct *conn,
  34                          const struct smb_filename *smb_fname,
  35                          uint32_t access_mask)
  36 {
  37         NTSTATUS status;
  38         uint32_t access_granted;
  39         struct security_descriptor *secdesc = NULL;
  40         bool ret;
  41
  42         if (get_current_uid(conn) == (uid_t)0) {
  43                 /* I'm sorry sir, I didn't know you were root... */
  44                 return true;
  45         }
  46
  47         status = SMB_VFS_GET_NT_ACL(conn, smb_fname->base_name,
  48                                     (SECINFO_OWNER |
  49                                      SECINFO_GROUP |
  50                                      SECINFO_DACL),
  51                                     &secdesc);
  52         if (!NT_STATUS_IS_OK(status)) {
  53                 DEBUG(5, ("Could not get acl: %s\n", nt_errstr(status)));
  54                 ret = false;
  55                 goto out;
  56         }
  57
  58         status = se_access_check(secdesc, get_current_nttok(conn),
  59                                  access_mask, &access_granted);
  60         ret = NT_STATUS_IS_OK(status);
  61
  62         if (DEBUGLEVEL >= 10) {
  63                 DEBUG(10,("can_access_file_acl for file %s "
  64                         "access_mask 0x%x, access_granted 0x%x "
  65                         "access %s\n",
  66                         smb_fname_str_dbg(smb_fname),
  67                         (unsigned int)access_mask,
  68                         (unsigned int)access_granted,
  69                         ret ? "ALLOWED" : "DENIED" ));
  70                 NDR_PRINT_DEBUG(security_descriptor, secdesc);
  71         }
  72  out:
  73         TALLOC_FREE(secdesc);
  74         return ret;
  75 }
  76
  77 /****************************************************************************
  78  Actually emulate the in-kernel access checking for delete access. We need
  79  this to successfully return ACCESS_DENIED on a file open for delete access.
  80 ****************************************************************************/
  81
  82 bool can_delete_file_in_directory(connection_struct *conn,
  83                                   struct smb_filename *smb_fname)
  84 {
  85         TALLOC_CTX *ctx = talloc_tos();
  86         char *dname = NULL;
  87         struct smb_filename *smb_fname_parent = NULL;
  88         NTSTATUS status;
  89         bool ret;
  90
  91         if (!CAN_WRITE(conn)) {
  92                 return False;
  93         }
  94
  95         if (!lp_acl_check_permissions(SNUM(conn))) {
  96                 /* This option means don't check. */
  97                 return true;
  98         }
  99
 100         /* Get the parent directory permission mask and owners. */
 101         if (!parent_dirname(ctx, smb_fname->base_name, &dname, NULL)) {
 102                 return False;
 103         }
 104
 105         status = create_synthetic_smb_fname(ctx, dname, NULL, NULL,
 106                                             &smb_fname_parent);
 107         if (!NT_STATUS_IS_OK(status)) {
 108                 ret = false;
 109                 goto out;
 110         }
 111
 112         if(SMB_VFS_STAT(conn, smb_fname_parent) != 0) {
 113                 ret = false;
 114                 goto out;
 115         }
 116
 117         /* fast paths first */
 118
 119         if (!S_ISDIR(smb_fname_parent->st.st_ex_mode)) {
 120                 ret = false;
 121                 goto out;
 122         }
 123         if (get_current_uid(conn) == (uid_t)0) {
 124                 /* I'm sorry sir, I didn't know you were root... */
 125                 ret = true;
 126                 goto out;
 127         }
 128
 129 #ifdef S_ISVTX
 130         /* sticky bit means delete only by owner of file or by root or
 131          * by owner of directory. */
 132         if (smb_fname_parent->st.st_ex_mode & S_ISVTX) {
 133                 if(SMB_VFS_STAT(conn, smb_fname) != 0) {
 134                         if (errno == ENOENT) {
 135                                 /* If the file doesn't already exist then
 136                                  * yes we'll be able to delete it. */
 137                                 ret = true;
 138                                 goto out;
 139                         }
 140                         DEBUG(10,("can_delete_file_in_directory: can't "
 141                                   "stat file %s (%s)",
 142                                   smb_fname_str_dbg(smb_fname),
 143                                   strerror(errno) ));
 144                         ret = false;
 145                         goto out;
 146                 }
 147
 148                 /*
 149                  * Patch from SATOH Fumiyasu <fumiyas@miraclelinux.com>
 150                  * for bug #3348. Don't assume owning sticky bit
 151                  * directory means write access allowed.
 152                  * Fail to delete if we're not the owner of the file,
 153                  * or the owner of the directory as we have no possible
 154                  * chance of deleting. Otherwise, go on and check the ACL.
 155                  */
 156                 if ((get_current_uid(conn) !=
 157                         smb_fname_parent->st.st_ex_uid) &&
 158                     (get_current_uid(conn) != smb_fname->st.st_ex_uid)) {
 159                         DEBUG(10,("can_delete_file_in_directory: not "
 160                                   "owner of file %s or directory %s",
 161                                   smb_fname_str_dbg(smb_fname),
 162                                   smb_fname_str_dbg(smb_fname_parent)));
 163                         ret = false;
 164                         goto out;
 165                 }
 166         }
 167 #endif
 168
 169         /* now for ACL checks */
 170
 171         /*
 172          * There's two ways to get the permission to delete a file: First by
 173          * having the DELETE bit on the file itself and second if that does
 174          * not help, by the DELETE_CHILD bit on the containing directory.
 175          *
 176          * Here we only check the directory permissions, we will
 177          * check the file DELETE permission separately.
 178          */
 179
 180         ret = can_access_file_acl(conn, smb_fname_parent, FILE_DELETE_CHILD);
 181  out:
 182         TALLOC_FREE(dname);
 183         TALLOC_FREE(smb_fname_parent);
 184         return ret;
 185 }
 186
 187 /****************************************************************************
 188  Actually emulate the in-kernel access checking for read/write access. We need
 189  this to successfully check for ability to write for dos filetimes.
 190  Note this doesn't take into account share write permissions.
 191 ****************************************************************************/
 192
 193 bool can_access_file_data(connection_struct *conn,
 194                           const struct smb_filename *smb_fname,
 195                           uint32 access_mask)
 196 {
 197         if (!(access_mask & (FILE_READ_DATA|FILE_WRITE_DATA))) {
 198                 return False;
 199         }
 200         access_mask &= (FILE_READ_DATA|FILE_WRITE_DATA);
 201
 202         /* some fast paths first */
 203
 204         DEBUG(10,("can_access_file_data: requesting 0x%x on file %s\n",
 205                   (unsigned int)access_mask, smb_fname_str_dbg(smb_fname)));
 206
 207         if (get_current_uid(conn) == (uid_t)0) {
 208                 /* I'm sorry sir, I didn't know you were root... */
 209                 return True;
 210         }
 211
 212         SMB_ASSERT(VALID_STAT(smb_fname->st));
 213
 214         /* Check primary owner access. */
 215         if (get_current_uid(conn) == smb_fname->st.st_ex_uid) {
 216                 switch (access_mask) {
 217                         case FILE_READ_DATA:
 218                                 return (smb_fname->st.st_ex_mode & S_IRUSR) ?
 219                                     True : False;
 220
 221                         case FILE_WRITE_DATA:
 222                                 return (smb_fname->st.st_ex_mode & S_IWUSR) ?
 223                                     True : False;
 224
 225                         default: /* FILE_READ_DATA|FILE_WRITE_DATA */
 226
 227                                 if ((smb_fname->st.st_ex_mode &
 228                                         (S_IWUSR|S_IRUSR)) ==
 229                                     (S_IWUSR|S_IRUSR)) {
 230                                         return True;
 231                                 } else {
 232                                         return False;
 233                                 }
 234                 }
 235         }
 236
 237         /* now for ACL checks */
 238
 239         return can_access_file_acl(conn, smb_fname, access_mask);
 240 }
 241
 242 /****************************************************************************
 243  Userspace check for write access.
 244  Note this doesn't take into account share write permissions.
 245 ****************************************************************************/
 246
 247 bool can_write_to_file(connection_struct *conn,
 248                        const struct smb_filename *smb_fname)
 249 {
 250         return can_access_file_data(conn, smb_fname, FILE_WRITE_DATA);
 251 }
 252
 253 /****************************************************************************
 254  Check for an existing default Windows ACL on a directory.
 255 ****************************************************************************/
 256
 257 bool directory_has_default_acl(connection_struct *conn, const char *fname)
 258 {
 259         /* returns talloced off tos. */
 260         struct security_descriptor *secdesc = NULL;
 261         unsigned int i;
 262         NTSTATUS status = SMB_VFS_GET_NT_ACL(conn, fname,
 263                                 SECINFO_DACL, &secdesc);
 264
 265         if (!NT_STATUS_IS_OK(status) || secdesc == NULL) {
 266                 return false;
 267         }
 268
 269         for (i = 0; i < secdesc->dacl->num_aces; i++) {
 270                 struct security_ace *psa = &secdesc->dacl->aces[i];
 271                 if (psa->flags & (SEC_ACE_FLAG_OBJECT_INHERIT|
 272                                 SEC_ACE_FLAG_CONTAINER_INHERIT)) {
 273                         TALLOC_FREE(secdesc);
 274                         return true;
 275                 }
 276         }
 277         TALLOC_FREE(secdesc);
 278         return false;
 279 }