MySql SQL injection attack: how to prevent and solve

MySQL is a commonly used relational database. Although it has high security characteristics, it also faces the threat of SQL injection attacks all the time. SQL injection attacks are a common attack method. Hackers will construct malicious SQL query statements to bypass the authentication and authorization of the application, and then obtain or destroy the data in the database. Below, we will introduce SQL injection attacks and how to prevent and resolve such attacks.

The principle of SQL injection attack
The most basic principle of SQL injection attack is to achieve the purpose of attack by injecting special SQL statements into the input data. Through malicious SQL query statements, hackers can bypass the application The security verification mechanism of the program can obtain or destroy the data in the database. For example, a simple SELECT query statement can be tampered with by a hacker into the following statement:

SELECT * from user WHERE username = 'admin' OR 1 = 1;

This query will return all user information, not just administrator information, because the condition of OR 1 = 1 will return all Qualifying records.

SQL injection attacks can be divided into three main types:

1. Error-based injection attacks

Error-based injection attacks refer to hackers passing After injecting malicious SQL statements into the database, an error occurs in the system and sensitive information is obtained.

For example, if a hacker enters the following content in the input box:

' or 1 = 1; SELECT * from users;

and the application does not filter and validate user input, then the input will be converted into the following SQL statement :

SELECT * from users WHERE password = '' or 1 = 1; SELECT * from users;

This SQL statement will cause errors, but the statements before this query statement have been executed, and the hacker can obtain all user information.

2. Time-based blind injection attack

A time-based blind injection attack means that the hacker injects a query statement into the database and sets a waiting time. If the query is successful, Then a hacker can read the value of this time and obtain sensitive information.

For example, if a hacker enters the following content in the input box:

' or if(now()=sleep(5),1,0); --

This statement means that if the current time is equal to 5 seconds, then the statement will wait forever, otherwise it will immediately return. If the response time received by the hacker is 5 seconds, then the query is successful, and this time can also provide the hacker with a lot of useful information.

3. Injection attack based on federated query

Injection attack based on federated query means that the hacker injects a query statement into the input box and executes the query statement. Merge the returned data with the original data in the application to obtain more sensitive information.

For example, if a hacker enters the following content in the input box:

' UNION SELECT TABLE_NAME FROM information_schema.tables WHERE TABLE_SCHEMA = 'database_name' --

This statement means that the hacker will first execute the SELECT query statement to query the table name in the information_schema database. If the query is successful, the hacker can obtain all table names in the system, and these table names may contain sensitive information.

How to prevent and resolve SQL injection attacks
SQL injection attacks are very dangerous, but if we take some measures, we can effectively prevent and resolve such attacks.

1. Use prepared statements and parameterized queries

Using prepared statements and parameterized queries is a good way to protect against SQL injection attacks. Most major programming languages ​​can prevent SQL injection attacks through prepared statements and parameterized queries.

Precompiled statements work by separating SQL statements and application code before executing SQL query statements, thereby reducing some potential attack points at runtime.

Parameterized query uses a method similar to prepared statements to inject query parameters and data. Parameterized queries separate the query parameters from the application code and use the program's own syntax to ensure that there is no direct connection between the input and query values.

2. Filtering and validating all user input

Filtering and validating all user input is an effective way to prevent SQL injection attacks. Data validation and filtering should be performed when checking user input to prevent malicious SQL queries from entering the application.

For example, filtering and validating the data type, length and range of user input, etc., can reduce the success rate of injection. Filtering user input for special characters is also a useful approach.

3. Minimize database access rights

Minimizing database access rights can prevent hackers from obtaining sensitive information and modifying data in the database through SQL injection attacks.

For example, separate read-only users and editable users to limit their permissions to access the database. At the same time, you can also prohibit access to sensitive databases and tables, or access the database anonymously.

4. Do not disclose sensitive information in error messages

When an application error occurs, sensitive information should not be disclosed in error messages.

For example, do not reveal sensitive information such as database schema, table structure, query statements, etc. in the error message. This information may be used by hackers to further attack your application.

Summary
SQL injection attack is a dangerous attack method, but as long as we take some measures and pay attention to program security during the development process, we can effectively prevent and solve this attack. The best approach is to use parameterized queries, filter and validate incoming data, minimize database access, and not reveal sensitive information in error messages. Only in this way can we keep our databases secure and protect our users' information.

The above is the detailed content of MySql SQL injection attack: how to prevent and solve. For more information, please follow other related articles on the PHP Chinese website!