Page MenuHomePhabricator

Disable XML entity loader by default in libphutil
ClosedPublic

Authored by epriestley on Jan 23 2014, 9:32 PM.
Tags
None
Referenced Files
Unknown Object (File)
Wed, May 28, 7:14 PM
Unknown Object (File)
Sun, May 25, 9:32 PM
Unknown Object (File)
Sat, May 24, 3:16 PM
Unknown Object (File)
Tue, May 20, 4:44 PM
Unknown Object (File)
Mon, May 19, 2:11 PM
Unknown Object (File)
Apr 26 2025, 9:50 AM
Unknown Object (File)
Apr 20 2025, 9:16 AM
Unknown Object (File)
Apr 20 2025, 8:01 AM
Subscribers

Details

Summary

See https://www.facebook.com/BugBounty/posts/778897822124446 and http://www.ubercomp.com/posts/2014-01-16_facebook_remote_code_execution.

By default, SimpleXMLElement will pretty much just run whatever code you want when handed a specially crafted document. We currently load XML only from trusted (S3, EC2, git/svn/hg) or local sources (unit test runners) so there are no concrete vulnerabilities in Phabricator, but this behavior is incredibly dangerous, surprising, and highly undesirable.

Test Plan

There's an example of a document which does bad things on http://www.php.net/manual/en/function.libxml-disable-entity-loader.php. I verified that SimpleXMLElement reads /etc/passwd when handed this document, then applied the fix. It no longer reads arbitrary files off disk.

Diff Detail

Lint
Lint Skipped
Unit
Tests Skipped