XXE in ImportFromSMathStudio.java

[prodigysml]

The Issue

An XML External Entity attack is a type of attack against an application that parses XML input. This attack occurs when XML input containing a reference to an external entity is processed by a weakly configured XML parser. This attack may lead to the disclosure of confidential data, denial of service, server side request forgery, port scanning from the perspective of the machine where the parser is located, and other system impacts.

Where the Issue Occurred

The following code snippets display the usage of DocumentBuilderFactory without securely disabling entities:

microMathematics/app/src/main/java/com/mkulesh/micromath/io/ImportFromSMathStudio.java

Line 179 in 1b8a59e

final Document doc = builder.parse(stream);

[mkulesh]

Dear @prodigysml, thanks for submitting this issue. I studied https://www.owasp.org/index.php/XML_External_Entity_(XXE)_Prevention_Cheat_Sheet and found, that only setExpandEntityReferences(false) is possible for Android DocumentBuilderFactory. All other recommendations from above mentioned link produce some exceptions. Therefore, I only added setExpandEntityReferences(false) for the DocumentBuilderFactory. I hope, the problem is solved. Are you agree with this solution?

[mkulesh]

Fixed and released in 2.17.3