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