<?php
/**
 *
 * SugarCRM Community Edition is a customer relationship management program developed by
 * SugarCRM, Inc. Copyright (C) 2004-2013 SugarCRM Inc.
 *
 * SuiteCRM is an extension to SugarCRM Community Edition developed by SalesAgility Ltd.
 * Copyright (C) 2011 - 2018 SalesAgility Ltd.
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Affero General Public License version 3 as published by the
 * Free Software Foundation with the addition of the following permission added
 * to Section 15 as permitted in Section 7(a): FOR ANY PART OF THE COVERED WORK
 * IN WHICH THE COPYRIGHT IS OWNED BY SUGARCRM, SUGARCRM DISCLAIMS THE WARRANTY
 * OF NON INFRINGEMENT OF THIRD PARTY RIGHTS.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Affero General Public License along with
 * this program; if not, see http://www.gnu.org/licenses or write to the Free
 * Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 *
 * You can contact SugarCRM, Inc. headquarters at 10050 North Wolfe Road,
 * SW2-130, Cupertino, CA 95014, USA. or at email address contact@sugarcrm.com.
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License version 3.
 *
 * In accordance with Section 7(b) of the GNU Affero General Public License version 3,
 * these Appropriate Legal Notices must retain the display of the "Powered by
 * SugarCRM" logo and "Supercharged by SuiteCRM" logo. If the display of the logos is not
 * reasonably feasible for technical reasons, the Appropriate Legal Notices must
 * display the words "Powered by SugarCRM" and "Supercharged by SuiteCRM".
 */


require_once 'include/php-sql-parser.php';

/**
 * SQL Validator class
 * @api
 */
class SugarSQLValidate
{
    /**
     * Parse SQL query WHERE and ORDER BY clauses and validate that nothing bad is happening there
     * @param string $where
     * @param string $order_by
     * @return bool
     */
    public function validateQueryClauses($where, $order_by = '')
    {
        if (empty($where) && empty($order_by)) {
            return true;
        }

        if (empty($where) && !empty($order_by)) {
            $where = "deleted=0";
        }

        $parser = new PHPSQLParser();
        $testquery = "SELECT dummy FROM dummytable WHERE $where";
        $clauses = 3;
        if (!empty($order_by)) {
            $testquery .= " ORDER BY $order_by";
            $clauses++;
        }
        $parsed = $parser->parse($testquery);
        //$GLOBALS['log']->debug("PARSE: ".var_export($parsed, true));

        if (count($parsed) != $clauses) {
            // we assume: SELECT, FROM, WHERE, maybe ORDER
            return false;
        }
        $parts = array_keys($parsed);
        if ($parts[0] != "SELECT" || $parts[1] != "FROM" || $parts[2] != "WHERE") {
            // check the keys to be SELECT, FROM, WHERE
            return false;
        }
        if (!empty($order_by) && $parts[3] != "ORDER") {
            // extra key is ORDER
            return false;
        }
        // verify SELECT didn't change
        if (count($parsed["SELECT"]) != 1 || $parsed["SELECT"][0] !== array('expr_type' => 'colref','alias' => '`dummy`', 'base_expr' => 'dummy', 'sub_tree' => false)) {
            $GLOBALS['log']->debug("validation failed SELECT");
            return false;
        }
        // verify FROM didn't change
        if (count($parsed["FROM"]) != 1 || $parsed["FROM"][0] !== array('table' => 'dummytable', 'alias' => 'dummytable', 'join_type' => 'JOIN', 'ref_type' => '', 'ref_clause' => '', 'base_expr' => false, 'sub_tree' => false)) {
            $GLOBALS['log']->debug("validation failed FROM");
            return false;
        }
        // check WHERE
        if (!$this->validateExpression($parsed["WHERE"], true)) {
            $GLOBALS['log']->debug("validation failed WHERE");
            return false;
        }
        // check ORDER
        if (!empty($order_by) && !$this->validateExpression($parsed["ORDER"])) {
            $GLOBALS['log']->debug("validation failed ORDER");
            return false;
        }
        return true;
    }

    /**
     * Prohibited functions
     * @var array
     */
    protected $bad_functions = array("benchmark", "encode", "sleep",
    "generate_series", "load_file", "sys_eval", "user_name",
    "xp_cmdshell", "sys_exec", "sp_replwritetovarbin");

    /**
     * Validate parsed SQL expression
     * @param array $expr Parsed expression
     * @return bool
     */
    protected function validateExpression($expr, $allow_some_subqueries = false)
    {
        foreach ($expr as $term) {
            if (!is_array($term)) {
                continue;
            }
            // check subtrees
            if (isset($term['expr_type']) &&  $term['expr_type'] == 'subquery') {
                if (!$allow_some_subqueries || !$this->allowedSubquery($term)) {
                    // subqueries are verboten, except for some very special ones
                    $GLOBALS['log']->debug("validation failed subquery");
                    return false;
                }
            } else {
                if (!empty($term['sub_tree']) && !$this->validateExpression($term['sub_tree'], $allow_some_subqueries)) {
                    return false;
                }
            }
            if (isset($term['type']) && $term['type'] == 'expression') {
                continue;
            }
            if ($term['expr_type'] == 'const' || $term['expr_type'] == 'expression') {
                // constants are OK, expressions checked above
                continue;
            }
            if ($term['expr_type'] == 'function') {
                // prohibit some functions
                if (in_array(strtolower($term['base_expr']), $this->bad_functions)) {
                    $GLOBALS['log']->debug("validation failed function");
                    return false;
                }
            }
            if ($term['expr_type'] == 'colref' && !$this->validateColumnName($term['base_expr'])) {
                // check column names
                $GLOBALS['log']->debug("validation failed column name");
                return false;
            }
            if (!empty($term['alias']) && $term['alias'] != $term['base_expr'] && $term['alias'] != "`".$term['base_expr']."`") {
                $GLOBALS['log']->debug("validation failed alias: ".var_export($term, true));
                return false;
            }
        }
        return true;
    }

    /**
     * Tables allowed in subqueries
     * @var array
     */
    protected $subquery_allowed_tables = array(
        'email_addr_bean_rel' => true,
        'email_addresses' => true,
        'emails' => true,
        'emails_beans' => true,
        'emails_text' => true,
        'teams' => true,
        'team_sets_teams' => true);

    /**
     * Allow some subqueries to pass
     * Needed since OPI uses subqueries for email searches... sigh
     * @param array $term term structure of the subquery
     */
    protected function allowedSubquery($term)
    {
        // Must be SELECT ... FROM ... WHERE ...
        if (empty($term['sub_tree']) || empty($term['sub_tree']['SELECT']) || empty($term['sub_tree']['FROM']) || empty($term['sub_tree']['WHERE'])) {
            $GLOBALS['log']->debug("subquery validation failed: missing item");
            return false;
        }

        foreach ($term['sub_tree']['SELECT'] as $select) {
            if ($select['expr_type'] == 'operator' && $select['base_expr'] == '*') {
                continue;
            }
            if ($select['expr_type'] != 'colref') {
                $GLOBALS['log']->debug("subquery validation failed: column: {$select['expr_type']}");
                // allow only columns in select
                return false;
            }
        }

        foreach ($term['sub_tree']['FROM'] as $from) {
            if (empty($this->subquery_allowed_tables[$from['table']])) {
                $GLOBALS['log']->debug("subquery validation failed: table: {$from['table']}");
                // only specific tables are allowed
                return false;
            }
            if (!empty($from['ref_clause']) && !$this->validateQueryClauses($from['ref_clause'])) {
                // validate join condition, if bad, bail out
                $GLOBALS['log']->debug("subquery validation failed: join: {$from['ref_clause']}");
                return false;
            }
        }

        if (!$this->validateExpression($term['sub_tree']['WHERE'])) {
            // validate where clause, no sub-subqueries allowed here
            $GLOBALS['log']->debug("subquery validation failed: where clause");
            return false;
        }

        return true;
    }

    /**
     * validateColumnName
     * This method validates the column name portion of the SQL statement and returns true if it is deemed safe.
     * We check against querying for the user_hash column.
     *
     * @param $name String portion of the column name from SQL
     * @return boolean True if column name is deemed safe, false otherwise
     */
    protected function validateColumnName($name)
    {
        if ($name == ",") {
            return true;
        } // sometimes , gets as column name
        $name = strtolower($name); // case does not matter

        $parts = explode(".", $name);
        if (count($parts) > 2) {
            // too many dots
            return false;
        }

        foreach ($parts as $part) {
            //the user_hash column is forbidden in passed in SQL
            if ($part == "user_hash") {
                return false;
            }

            //Remove leading and trailing ` characters for the part
            if (preg_match('/^[\`](.+?)[\`]$/', $part, $matches)) {
                $part = $matches[1];
            }

            //We added an exception for # symbol (see Bug 50324)
            //This should be removed when Bug 50360 is resolved
            if (preg_match('/[^a-z0-9._#]/', $part)) {
                // bad chars in name
                return false;
            }
        }

        return true;
    }
}