Exploit: How to Easily Abuse Target Sites via PHP Error Messages

With the development of the Internet, website security issues have attracted increasing attention. Attack methods are constantly evolving, and exploiting vulnerabilities has become one of attackers’ favorite methods. Among them, the method of abusing the target site through PHP error messages is relatively common. This article discusses this issue and shows how attackers can exploit the vulnerabilities to easily compromise target sites.

1. The harm of error information leakage

1. Security vulnerability exposure

Many developers will use PHP debugging tools or output functions during the development process , such as phpinfo(), var_dump(), etc., when these functions are exposed to the public network, all configuration information and variable values ​​related to PHP in the server will be output, posing a serious threat to server security.

2. SQL injection

Through the error message, the attacker can obtain the errors generated when accessing the database and thus learn the database-related information. Combined with other information collection methods, you can master important information such as the complete structure of the database, administrator account, password, etc., and easily carry out SQL injection attacks.

3. Leakage of sensitive information

Due to improper program development, when an error occurs, the error message may contain sensitive information, such as username, password, key, etc. After an attacker obtains this information, he or she can easily attack the site and cause irreparable damage.

2. Reasons for error information leakage

1. Enable error_reporting in php.ini

If error_reporting is enabled in PHP, the PHP program will be output error message.

Find the following line in the php.ini configuration file:

error_reporting = E_ALL

Change it to:

error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT

can turn off error message prompts to ensure site security.

2. Calling function location

If you use the debug function or output function in the PHP code, or use functions such as echo and print, or directly call certain variables and attributes in the PHP script , specific error information will be output to the screen. At this time, the attacker can use this information to carry out attacks.

3. Server configuration error

When the server configuration is improper, you can directly view the php.ini file or user configuration file, so that the vulnerability will be exposed and the attacker can easily obtain Server information.

3. How attackers exploit misinformation vulnerabilities

Attackers can use web information collection, directory blasting, privilege escalation and other techniques, combined with the information exposed by misinformation vulnerabilities, to construct a Malicious injection of code transfers the malicious code to the server for execution, and then achieves the purpose of controlling the server, carrying out attacks and destroying the normal business of the website.

In fact, this attack method is very subtle. There is no need for the attacker to use brute force attacks to try to obtain all sensitive server and business information in a short time, because the time required to obtain the information will be very long. On the contrary, attackers can use misinformation vulnerabilities to obtain the required information for free and quickly, and at the same time implant malicious code on the server, which will pose a huge threat to website security.

4. How to prevent error message vulnerabilities

1. Configure php.ini

Turn off error_reporting in php.ini and limit phpinfo output information.

2. Delete unnecessary debugging functions

Unnecessary debugging functions should be deleted as much as possible, such as var_dump(), print_r() and other output functions. You can add judgment statements, only in Output under the given IP.

3. Permission control

Set permissions reasonably to limit access to files or directories that may be invaded.

4. Log monitoring

Conduct log monitoring for common attack methods, and detect and handle abnormal requests in a timely manner.

5. Update programs and components

Update programs and components in a timely manner, install firewalls, and deal with possible vulnerabilities in a timely manner.

In summary, easily abusing a target site through PHP error messages is a very dangerous attack method. In order to protect website security, developers and administrators should consciously update programs and components regularly, while strengthening log monitoring and security auditing to avoid security breaches. At the same time, end users should also be educated to avoid over-reliance on the convenience of the platform and effectively strengthen the cultivation of network security awareness.

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