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