Does the preparedStatement avoid SQL injection?

Question

I have read and tried to inject vulnerable sql queries to my application. It is not safe enough. I am simply using the Statement Connection for database validations and other insertion operations.

Is the preparedStatements safe? and moreover will there be any problem with this statement too?

Solution 1

Using string concatenation for constructing your query from arbitrary input will not make PreparedStatement safe. Take a look at this example:

preparedStatement = "SELECT * FROM users WHERE name = '" + userName + "';";

If somebody puts

' or '1'='1

as userName, your PreparedStatement will be vulnerable to SQL injection, since that query will be executed on database as

SELECT * FROM users WHERE name = '' OR '1'='1';

So, if you use

preparedStatement = "SELECT * FROM users WHERE name = ?";
preparedStatement.setString(1, userName);

you will be safe.

Some of this code taken from this Wikipedia article.

Solution 2

The prepared statement, if used properly, does protect against SQL injection. But please post a code example to your question, so we can see if you are using it properly.

Solution 3

Well simply using PreparedStatement doesn't make you safe. You have to use parameters in your SQL query which is possible with PreparedStatement. Look here for more information.

Solution 4

The PreparedStatement alone does not help you if you are still concatenating Strings.

For instance, one rogue attacker can still do the following:

• call a sleep function so that all your database connections will be busy, therefore making your application unavailable
• extracting sensitive data from the DB
• bypassing the user authentication

And it's not just SQL that can b affected. Even JPQL can be compromised if you are not using bind parameters.

Bottom line, you should never use string concatenation when building SQL statements. Use a dedicated API for that purpose:

• JPA Criteria API
• jOOQ

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Comments

[Mohamed Saligh]

Does the setString make any difference? what it actually does? Even thats going to substitute the string inplace. What different it makes?

[darioo]

@Mohamed: it makes a difference. The query "SELECT * FROM users WHERE name = ?" will be sent to the database where it's compiled and then userName from setString will be substituted. If the database sees an illegal value, it will throw an error. So, ' or '1'='1 will be treated as a whole string, and not as a statement involving operators or and =. The database will see it as a string with value "' or '1'='1".