FlowSafe

FlowSafe: Information Flow Security for the Browser

The central idea is to improve the default browser security model, which is "stuck" since 1995 at the Same-Origin Policy with its underlying and conflicting DOM access control and JavaScript object-capability security layers.

We aim to do this without breaking the web, and indeed with measurable improvements to safety property enforcement and security policy expressiveness.

Goals

• Improve default cross-site script integrity (ads, analytics)
• Systematically enforce the Same-Origin Policy and better security policies by pervasive mediation
• Reduce existing "caps", DOM, and JavaScript engine patch-work / leaky reference monitor code
• Guarantee termination-insensitive non-interference for better confidentiality
• Explore timing and termination channel mitigations

To-do

Implement dynamic-only, fail-stop "no sensitive upgrade" or better, information flow security for JS, the DOM, and other parts of the browser. See this paper on part of the work.

1. Add JSTrustLabel to the JS API, a union of JSPrincipals (trust labels replace principals)
2. Have shapes imply trust labels so that distinct origins get different shapes for standard objects, equivalent property list patterns, etc.
3. Extend JSExtendedClass to delegate typeof so we can build LabeledPrimitiveValue wrappers for primitives
   1. Also need to rebox results of all primitive operators, e.g. -x for x = new LabeledPrimitiveValue(42) should be a LabeledPrimitiveValue instance, not the number -42
4. JSScript has a JSTrustLabel
5. Interpreter pc has a JSTrustLabel
6. Variable objects (even those optimized away) have a JSTrustLabel
7. Add policy JS API that allows custom assignment, control flow branching, and input/output policy decision points -- does this mean SSA in one pass?
8. Add shell functions for testing and write tests
9. DOM, other host objects have trust labels
10. Exceptions, etc.
11. Declassify primitive TBD, defer for now

--Brendan 01:36, 31 October 2009 (UTC)

References

Efficient Purely-Dynamic Information Flow Analysis (PLAS '09)