SQL injection parsing in PHP

I. Types of injection attacks
There may be many different types of attack motives, but at first glance there seems to be more types. This is very real-if a malicious user discovers a way to execute multiple queries. We'll discuss this in more detail later in this article.
Such as
If your script is executing a SELECT directive, an attacker could force the display of each row in a table-by injecting a condition such as "1=1" into the WHERE clause, as shown below (where the injected portion is shown in bold):
SELECT * FROM wines WHERE variety = ' Lagrein ' OR 1=1; '

As we discussed earlier, this may be useful information in itself, as it reveals the general structure of the table (which is not achievable by a common record) and potentially displays records containing confidential information.
An update directive can potentially have a more immediate threat. By placing other attributes in the SET clause, an attacker can modify any field in the record that is currently being updated, such as the following example (where the injected portion is shown in bold):
UPDATE Wines SET type= ' red ', ' vintage ' = ' 9999 ' WHERE variety = ' Lagrein '

By adding a constant condition such as 1=1 to the WHERE clause of an update instruction, the scope of the modification can be extended to each record, such as the following example (where the injected portion is shown in bold):
UPDATE Wines SET type= ' red ', ' vintage ' = ' 9999 WHERE variety = ' Lagrein ' OR 1=1; '

The most dangerous instructions could be delete-. This is not difficult to imagine. The injection technique is the same as we have seen-extending the scope of the affected record by modifying the WHERE clause, such as the following example (where the injected portion is shown in bold):
DELETE from wines WHERE variety = ' Lagrein ' OR 1=1; '

Two, multiple query injection
Multiple query injections will exacerbate the potential damage that an attacker might cause-by allowing multiple destructive instructions to be included in a single query. When using a MySQL database, an attacker could easily do this by inserting an unexpected terminator into the query-an injected quotation mark (single or double quotation marks) marks the end of the desired variable, and then terminates the instruction with a semicolon. Now, an additional attack instruction may be added to the end of the original instruction that is now terminated. The final destructive query might look like the following:

SELECT * FROM wines WHERE variety = 'lagrein';GRANTALLON *.* TO'BadGuy@%' IDENTIFIED BY'gotcha';

This injection creates a new user Badguy and gives it network privileges (with all the privileges on all tables), and an "ominous" password is added to this simple SELECT statement. If you follow our recommendations in previous articles-strictly restricting the privileges of the process user, this should not work because the Web server daemon no longer has the grant privilege that you withdrew. But in theory, such an attack could give badguy free power to do whatever it does to your database.

As to whether such a multi-query will be processed by the MySQL server, the conclusion is not unique. Some of these reasons may be due to different versions of MySQL, but most of this is due to the way multiple queries exist. The MySQL monitoring program completely allows such a query. A common MySQL gui-phpmyadmin that copies all of the previous content before the final query, and only does so.
However, most of the multiple queries in an injection context are managed by PHP's MySQL extension. Fortunately, by default, it is not allowed to execute multiple instructions in a single query; Attempting to execute two instructions (such as the one shown above) will simply lead to failure-no errors are set and no output information is generated. In this case, although PHP is simply "behaving" to implement its default behavior, it does protect you from most simple injection attacks. The new mysqli extension in the
PHP5 (reference http://php.net/mysqli), like MySQL, does not inherently support multiple queries, but it provides a mysqli_multi_query () function to support you in implementing multiple queries-if you really want to do this.
However, the sqlite-and PHP5 bindings to the embeddable SQL database engine (reference http://sqlite.org/and http://php.net/sqlite) are more frightening and attract a lot of attention from users because of their ease of use. In some cases, SQLite allows such a multi-directive query by default, because the database can optimize batch queries, especially for very efficient batch INSERT statement processing. However, if the result of the query is used by your script (for example, in the case of retrieving records using a SELECT statement), the Sqlite_query () function does not allow multiple queries to be executed. Third, Invision Power BOARD SQL injection Vulnerability
Invision Power BOARD is a well-known forum system. May 6, 2005, a SQL injection vulnerability was found in the login code. The
was discovered by James Bercegay of Gulftech Security.
This login query looks like this:

$DB->query("SELECT * FROM ibf_members WHERE id=$mid AND password='$pid'"

Where the member ID variable m i d and port order I D change volume

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