BUG#32111 - Security Breach via DATA/INDEX DIRECORY and RENAME TABLE

RENAME TABLE against a table with DATA/INDEX DIRECTORY overwrites
the file to which the symlink points.

This is security issue, because it is possible to create a table with
some name in some non-system database and set DATA/INDEX DIRECTORY
to mysql system database. Renaming this table to one of mysql system
tables (e.g. user, host) would overwrite the system table.

Return an error when the file to which the symlink points exist.

(This is a copy of changeset 2007/11/06 18:09:33+04:00 svoj@mysql.com
and its merge changesets on the way from 4.0 up to 5.0)


mysql-test/r/symlink.result:
  A test case for BUG#32111, with after merge fix, and using proper variable.
mysql-test/t/symlink.test:
  A test case for BUG#32111, with after merge fix, and using proper variable.
mysys/my_symlink2.c:
  Return an error when the file to which the symlink points exist.

mysql-test/r/symlink.result

@@ -99,6 +99,12 @@ t1	CREATE TABLE `t1` (
   `b` int(11) default NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
+CREATE TABLE t1(a INT)
+DATA DIRECTORY='TEST_DIR/master-data/mysql'
+INDEX DIRECTORY='TEST_DIR/master-data/mysql';
+RENAME TABLE t1 TO user;
+ERROR HY000: Can't create/write to file 'TEST_DIR/master-data/mysql/user.MYI' (Errcode: 17)
+DROP TABLE t1;
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (

mysql-test/t/symlink.test

@@ -124,6 +124,18 @@ enable_query_log;
 show create table t1;
 drop table t1;
 
+#
+# BUG#32111 - Security Breach via DATA/INDEX DIRECORY and RENAME TABLE
+#
+--replace_result $MYSQLTEST_VARDIR TEST_DIR
+eval CREATE TABLE t1(a INT)
+DATA DIRECTORY='$MYSQLTEST_VARDIR/master-data/mysql'
+INDEX DIRECTORY='$MYSQLTEST_VARDIR/master-data/mysql';
+--replace_result $MYSQLTEST_VARDIR TEST_DIR
+--error 1
+RENAME TABLE t1 TO user;
+DROP TABLE t1;
+
 #
 # Test specifying DATA DIRECTORY that is the same as what would normally
 # have been chosen. (Bug #8707)

mysys/my_symlink2.c

@@ -126,6 +126,7 @@ int my_rename_with_symlink(const char *from, const char *to, myf MyFlags)
   int was_symlink= (!my_disable_symlinks &&
 		    !my_readlink(link_name, from, MYF(0)));
   int result=0;
+  int name_is_different;
   DBUG_ENTER("my_rename_with_symlink");
 
   if (!was_symlink)
@@ -134,6 +135,14 @@ int my_rename_with_symlink(const char *from, const char *to, myf MyFlags)
   /* Change filename that symlink pointed to */
   strmov(tmp_name, to);
   fn_same(tmp_name,link_name,1);		/* Copy dir */
+  name_is_different= strcmp(link_name, tmp_name);
+  if (name_is_different && !access(tmp_name, F_OK))
+  {
+    my_errno= EEXIST;
+    if (MyFlags & MY_WME)
+      my_error(EE_CANTCREATEFILE, MYF(0), tmp_name, EEXIST);
+    DBUG_RETURN(1);
+  }
 
   /* Create new symlink */
   if (my_symlink(tmp_name, to, MyFlags))
@@ -145,7 +154,7 @@ int my_rename_with_symlink(const char *from, const char *to, myf MyFlags)
     the same basename and different directories.
    */
 
-  if (strcmp(link_name, tmp_name) && my_rename(link_name, tmp_name, MyFlags))
+  if (name_is_different && my_rename(link_name, tmp_name, MyFlags))
   {
     int save_errno=my_errno;
     my_delete(to, MyFlags);			/* Remove created symlink */