Bug#50373 --secure-file-priv=""

The server variable opt_secure_file_priv wasn't
normalized properly and caused the operations
LOAD DATA INFILE .. INTO TABLE ..
and
SELECT load_file(..)
to do different interpretations of the 
--secure-file-priv option.

The patch moves code to the server initialization
routines so that the path always is normalized
once and only once.

It was also intended that setting the option
to an empty string should be equal to 
lifting all previously set restrictions. This
is also fixed by this patch.

mysql-test/suite/sys_vars/r/secure_file_priv.result

+#
+# Bug50373 --secure-file-priv=""
+#
+CREATE TABLE t1 (c1 VARCHAR(50));
+INSERT INTO t1 VALUES ("one"),("two"),("three"),("four"),("five");
+SHOW VARIABLES LIKE 'secure_file_priv';
+Variable_name	Value
+secure_file_priv	
+c1
+one
+two
+three
+four
+five
+loaded_file
+one
+two
+three
+four
+five
+
+DROP TABLE t1;

mysql-test/suite/sys_vars/t/secure_file_priv-master.opt

+--secure_file_priv=''

mysql-test/suite/sys_vars/t/secure_file_priv.test

+--echo #
+--echo # Bug50373 --secure-file-priv=""
+--echo #
+CREATE TABLE t1 (c1 VARCHAR(50));
+INSERT INTO t1 VALUES ("one"),("two"),("three"),("four"),("five");
+SHOW VARIABLES LIKE 'secure_file_priv';
+--disable_query_log
+# Atempt to create a file where we normally aren't allowed to create one.
+# Doing this in a portable manner is difficult but we should be able to
+# count on the depth of the directory hierarchy used. Three steps up from
+# the datadir is the 'mysql_test' directory.
+--let $PROTECTED_FILE=`SELECT concat(@@datadir,'/../../../bug50373.txt')`;
+--eval SELECT * FROM t1 INTO OUTFILE '$PROTECTED_FILE';
+DELETE FROM t1;
+--eval LOAD DATA INFILE '$PROTECTED_FILE' INTO TABLE t1;
+SELECT * FROM t1;
+--eval SELECT load_file('$PROTECTED_FILE') AS loaded_file;
+--enable_query_log
+remove_file $PROTECTED_FILE;
+DROP TABLE t1;
+

sql/mysqld.cc

@@ -8818,10 +8818,25 @@ static int fix_paths(void)
    */
   if (opt_secure_file_priv)
   {
-    convert_dirname(buff, opt_secure_file_priv, NullS);
-    my_free(opt_secure_file_priv, MYF(0));
-    opt_secure_file_priv= my_strdup(buff, MYF(MY_FAE));
+    if (*opt_secure_file_priv == 0)
+    {
+      opt_secure_file_priv= 0;
+    }
+    else
+    {
+      convert_dirname(buff, opt_secure_file_priv, NullS);
+      char *secure_file_real_path= (char *)my_malloc(FN_REFLEN, MYF(MY_FAE));
+      if (secure_file_real_path == 0 ||
+          my_realpath(secure_file_real_path, opt_secure_file_priv, 0))
+      {
+        sql_print_warning("Failed to normalize the argument for --secure-file-priv.");
+        return 1;
+      }
+      my_free(opt_secure_file_priv, MYF(0));
+      opt_secure_file_priv= secure_file_real_path;
+    }
   }
+  
   return 0;
 }
 

sql/sql_load.cc

@@ -350,9 +350,7 @@ int mysql_load(THD *thd,sql_exchange *ex,TABLE_LIST *table_list,
       }
       else if (opt_secure_file_priv)
       {
-        char secure_file_real_path[FN_REFLEN];
-        (void) my_realpath(secure_file_real_path, opt_secure_file_priv, 0);
-        if (strncmp(secure_file_real_path, name, strlen(secure_file_real_path)))
+        if (strncmp(opt_secure_file_priv, name, strlen(opt_secure_file_priv)))
         {
           /* Read only allowed from within dir specified by secure_file_priv */
           my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--secure-file-priv");