Re: Verified Javascript for WebAppSec re-chartering?

Thanks, Harry.

On Wed, Sep 24, 2014 at 3:41 PM, Ben Laurie <> wrote:

> > This would seem to disable an entire class of applications are then
> > not really suitable for the Web, i.e. those applications where the
> > server may not be trusted. In that case, it seems that having some
> > third party verification of Javascript code would be useful. This may
> > also be useful for Web applications where the server is trusted but
> > may be insecure. It seems Sub-resource integrity is headed in this
> > direction, but we can also imagine other ways this may be tackled that
> > involve some third party verification of Javascript.

SRI verifies that the code sent by a server is the code that the document
into which that code is loaded expected to receive. It doesn't do anything
to ensure that those expectations match the users'.

I think there's probably some value to a code-signing extension to SRI
(that is, verification of a signature's providence rather than verification
of a file's contents), but it's not clear to me how that would address the
threat model posited here. If you don't trust the server, and you don't
trust the author, what good does it do you to know that the code you
received is the code the author intended you to receive?

Could you point me to a more detailed description of the actual proposal?

> I believe Ben Laurie noted that in his STRINT submission some
> > CertTrans-like mechanism could even be used [2]. Without this, we see
> > developments like Chrome's e2e email extension as browser extension
> > rather than being done natively in the browser.
> Extensions are also updated automatically, so I don't see how this
> helps, particularly.
> That said, a CT-like mechanism could help with all of these cases.

I totally agree with the benefit of a CT-like mechanism for extensions, and
I guess I could get behind a CT-like mechanism for particular code snippets
(though there's a huge difference in scope between compiling a list of all
the certs ever vs all the code snippets ever).


Mike West <>
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Received on Wednesday, 24 September 2014 14:09:18 UTC