Guide to CSRF Attack and Defense in PHP

CSRF attack refers to an attack method that achieves malicious requests by forging user authentication information. As a language widely used in web development, PHP is more likely to be the target of CSRF attacks. This article will introduce the basic concepts of CSRF attacks, attack methods and their application scenarios in the PHP language. It will also provide some defense guidelines for CSRF attacks in PHP.

1. Basic concepts of CSRF attacks

The full name of CSRF is Cross-Site Request Forgery. CSRF attack is an attack method that exploits vulnerabilities in web applications to impersonate legitimate users to perform certain malicious behaviors. A CSRF attack is a passive attack. The attacker cannot directly obtain the victim's password or other data. Instead, the attacker achieves the purpose of the attack by tricking the victim into visiting a malicious website or clicking on a malicious link.

2. Implementation methods of CSRF attacks

The implementation methods of CSRF attacks usually include the following:

1. Use image tags and iframe tags to send requests: Attacker Embed malicious code into image tags or iframe tags, and guide the victim to access the embedded malicious code when visiting the attacker's website. When the victim enters the attacker's website, the attacker's code automatically sends a request to the target website.
2. Use form submission to send requests: The attacker tricks the user into submitting the form by forging a form similar to the target website and forging the victim's authentication information in the form. When the victim submits the form, the attacker's malicious code will send the information in the form to the target website, and the forged authentication information will be considered by the target website as a request from a legitimate user.
3. Use Ajax technology to send requests: The attacker forges a GET or POST request by using JavaScript code and sends the request to the target website through Ajax technology. During this process, the attacker will also forge the victim's authentication information.

3. CSRF attack application scenarios in PHP

In PHP development, there are many scenarios that may lead to CSRF attacks. Common ones include the following:

1. Use the get method to submit data in the form: If the application uses the get method to submit data containing sensitive information, a malicious attacker can create a link in the web page to send attack requests.
2. Lack of security identification when submitting in the form: If there is sensitive data that needs to be submitted, a security identification must be added when the form is submitted, such as adding a randomly generated token to the form.
3. There are malicious scripts in the application: If the application contains malicious JavaScript scripts, these scripts may take advantage of the user's browser and allow the user to perform some malicious operations.
4. Insufficient Access Control: If an application lacks access control, an attacker can send requests that need to be protected by access control.

4. Defense Guidelines for CSRF Attacks in PHP

In order to avoid CSRF attacks, some measures must be taken to enhance the security of web applications, including the following points:

1. Randomly generated security identification: Add a randomly generated security identification when submitting the form. This identification can be a token to verify the legality of the form submission.
2. Restrict the source of asynchronous requests: In order to limit the sources of asynchronous requests, you can use Origin Header to limit the sources of asynchronous requests.
3. Standardize data access: It is recommended to encapsulate data access to the management side to standardize data access. This helps applications detect and handle malicious behavior.
4. Strengthen access control: Strengthening access control is very important to reduce CSRF attacks. It is recommended to add access control rules to the application to ensure that only authorized users can perform some sensitive operations, such as changing passwords and user accounts.
5. Confirm identity: Confirming the user's identity is very critical. Encrypted user authentication is recommended to confirm user identity.
6. Encode client-side scripts: Encoding client-side scripts using JavaScript character encoding can effectively prevent attackers from launching attacks from content similar to the