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by TZubiri 483 days ago
Question.

I've noticed a lot of websites import from other sites, instead of local.

<script src="scriptscdn.com/libv1.3">

I almost never see a hash in there. Is this as dangerous as it looks, why don't people just use a hash?

2 comments

1. Yes

2. Because that requires you to know how to find the hash and add it.

Truthfully the burden should be on the third party that's serving the script (where did you copy that HTML in the first place?) but they aren't incentivizes to have other sites use a hash.

Well, to be honest, the browsers could super easily solve that. In dev mode, just issue a warning "loaded script that has hash X but isn't statically defined. This is a huge security risk. Read more here" and that's it. Then you can just add the script, run the site, check the logs and add the hash, done.
You can define a CSP header to only exec 3rd Party scripts with known hashes
But that doesn't make it easy to integrate a new script from an author who doesn't provide the hash already.
Vendor your dependencies. It’s better for you as a maintainer anyway, since caching only works[0] with first party domains with any reliability.

And once you vendor your dependencies you can calculate the hash yourself

[0]: there are caveats to this

How would third party distribution like a cdn affect hashing?

I think https and integrity hashes address two very orthogonal attack vectors.

But you can .. get the hash yourself?

wget url; sha256 file

Of course you can. But when it comes to security, one thing is very important in practice: making the secure way of doing things as easy as possible.

So, why did you not actually post the correct shell script? Apparently that would have been more effort to get right and ensure is correct right? And also work for every OS. And there you have it: if someone first has to figure out which script to run, some percentage will give up here. And that's my point: the browser should make it as easy as possible to avoid that from happening.

Cool. Now your site will break if the upstream pushes a fix while you're on vacation.
> In dev mode, just issue a warning "loaded script that has hash X but isn't statically defined.

How does the browser know which files to warn you about? What about scripts that are generated dynamically and have no static hash? There's plenty of reasons why you wouldn't want this.

It just warns about all embedded non-same-origin scripts that don't have a hash.

> What about scripts that are generated dynamically and have no static hash?

Well, then the warning is still valid because this is a security risk. I guess it'd be fine to be able to suppress the warning explicitly in those cases.

> There's plenty of reasons why you wouldn't want this.

For example? Honestly curious where you would not want a warning by default.

I wish popular browsers would get together and release an update that says:

- After version X we are displaying a prominent popup if a script isn't loaded with a hash

- After version Y we blocking scripts loaded without hashes

They could solve this problem in a year or so, and if devs are too lazy to specify a hash when loading scripts then their site will break.

Literally every website that uses JSONP will stop working if that happened. This would break the web in fundamental ways. If we're going to break the web in fundamental ways, resource integrity is hardly among the things that I'd be interested in changing.
Why would people choose JSONP over CORS?

There are security risks with JSONP (a hack to bypass same-origin policy), and the successor (CORS) has been around since 2009, so phasing it out may be a good thing.

https://dev.to/benregenspan/the-state-of-jsonp-and-jsonp-vul...

Good. JSONP requests to a domain you don't control are a security nightmare.
I don't think it's just laziness. There's use cases where the libraries are designed to be updated automatically.

Also some of the tracking scripts I don't think are strictly static content, maybe their strategy to fingerprint browser involves sending different shit to different users.

If you are the one serving the website, then you are the one generating the hash. If you want to serve different stuff then you could dynamically generate the hash for that different stuff rather than hard code it statically.

Specifying a script hash says that you as the owner of that site agree to load the content only if it matches the hash. Presumably you trust the content enough to serve it to your users.

Yes it is. Hashes must absolutely be used in that case.
It should just not be done at all. But the main browser vendor loves tracking so they won't forbid this.
Are you saying Chrome should block all script includes that don't have hashes? That'll break tons of sites. See "Don't break the web"[1].

Disclosure: I work at Google, but not on Chrome.

[1] https://flbrack.com/posts/2023-02-15-dont-break-the-web/

Also expired certificates break a lot of websites… should we disable checking?
Certificate expiration isn't an unanticipated regression. You know when you get a certificate when it will expire.
I don't mean to be pedantic, but not always--see the recent DigiCert delayed revocation issues. I will admit it is rare though and more often than not, you (should) know when your certs are going to expire.
Those websites set up the expiring certificate themselves.
Maybe, but just from a security point of view it's totally fine.
Getting tracked is less secure than not getting tracked.
Getting hacked is less secure than getting tracked.
Very clever. But getting tracked doesn't in any way protect you from getting hacked. It just exposes you to more risks, including getting hacked.
Fair enough.