Directory Traversal in FileDirectives

Date

2016-09-30

Description

On Windows akka-http’s getFromDirectory, getFromBrowseableDirectory, getFromBrowseableDirectories, and listDirectoryContents directives unintentionally allow access to directories and files outside of the specified directory.

All directories and files on the same drive as the specified directory for which the server process has sufficient permissions may be downloaded or browsed. This can be easily exploited by using a specially crafted URI.

For example, a specially crafted request http://localhost:8080/%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5c..%5cwindows/win.ini when handled by one of the affected directives, could expose your win.ini (and potentially any other file) to the attacker.

Impact

Directory traversal attack in case the above vulnerable directives are used.

Affected Versions

OS:

• Only Windows operating systems are affected by this vulnerability.

Versions:

• akka-http-experimental prior to 2.4.11
• spray-routing and spray-routing-shapeless2 prior to 1.3.4

Affected directives:

• getFromDirectory
• getFromBrowseableDirectory
• getFromBrowseableDirectories
• listDirectoryContents

Fixed versions

• akka-http-experimental 2.4.11
• akka-http-experimental 2.0.5 (legacy)
• spray 1.3.4

The fixed versions are binary-compatible with each of the affected versions, please upgrade as soon as you can.

Recommendations

Following best security practices it is furthermore recommended to run the web server process with user credentials with as few permissions as possible to prevent unintended file access.

Furthermore, we suggest using Linux servers and/or containers for hosting Akka HTTP applications, as these OSes receive more scrutiny than any other OS just because of the overwhelming number of installations running on Linux.

Acknowledgements

Many thanks go to @roikonen for reporting the problem, @2beaucoup for providing a fix and @rbudzko and @jypma for providing advice for fixing the problem.