Summary:
Via HackerOne. Chrome (at least) interprets backslashes like forward slashes, so a redirect to "/\evil.com" is the same as a redirect to "//evil.com".
- Reject local URIs with backslashes (we never generate these).
- Fully-qualify all "Location:" redirects.
- Require external redirects to be marked explicitly.
Test Plan:
- Expanded existing test coverage.
- Verified that neither Diffusion nor Phriction can generate URIs with backslashes (they are escaped in Diffusion, and removed by slugging in Phriction).
- Logged in with Facebook (OAuth2 submits a form to the external site, and isn't affected) and Twitter (OAuth1 redirects, and is affected).
- Went through some local redirects (login, save-an-object).
- Verified file still work.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Differential Revision: https://secure.phabricator.com/D10291
