Side-channel Attack Affecting org.apache.tapestry:tapestry-core package, versions [5.4.0,5.4.5)


0.0
medium
  • Attack Complexity

    High

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  • snyk-id

    SNYK-JAVA-ORGAPACHETAPESTRY-467117

  • published

    16 Sep 2019

  • disclosed

    21 Apr 2019

  • credit

    David Tomaschik

How to fix?

Upgrade org.apache.tapestry:tapestry-core to version 5.4.5 or higher.

Overview

org.apache.tapestry:tapestry-core is a Tapestry Core package for Apache Tapestry.

Affected versions of this package are vulnerable to Side-channel Attack. It is possible to conduct a side channel timing attack during the comparison of HMAC signatures by package due to the usage of String.equals() This could lead to remote code execution if an attacker is able to determine the correct signature for their payload. The comparison should be done with a constant time algorithm instead.

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

  • Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

  • Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys