webappsec

Here's a potentially easier to read (doesn't require JavaScript) document explaining WebSign: https://www.cyph.com/websign It's a really smart idea, although it did have some odd edge cases, and required you to trust that they really were throwing away the keys as promised. There is some talk in the W3C of extending the SRI standard to let a website declare that all (or just certain) included resources have been signed by an (offline) PGP key: https://github.com/w3c/webappsec/issues/449 so we might one day reach a point where running a webapp at least has the small security guarantee that a TOFU policy gives you. If this could be combined with versioned releases of webapps, and the signature appearing in something like a Binary Transparency log, then the security guarantee could actually be quite meaningful: https://wiki.mozilla.org/Secu

Attackers could otherwise verify that resources on private networks or retrievable only with the victim's cookies have certain content. See, e.g., <https://github.com/w3c/webappsec/issues/418> for some broader discussion.

These problems are really hairy. Thankfully, all the privacy issues are only one-bit leakages (and there are TONS of one-bit leakages in web browsers), but the CSP bypass with SRI attack is really cool. One thing that I've found incredibly disappointing about SRI is that it requires CORS. There's some more information here: https://github.com/w3c/webappsec/issues/418 but it essentially means that you can't SRI-pin content on a sketchy/untrustworthy CDN without them putting in work to enable CORS (which, if they're sketchy and untrustworthy, they probably won't do). The attack that the authors lay out for SRI requiring CORS is legitimate, but incredibly silly - a site could use SRI as an oracle to check the hash value of cross-domain content. You could theoretically use this to brute force secrets on pages, but this is kind of silly becaus