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Comment by varenc | Hacker News Reader

Side note: This wouldn't get around cert-pinning? Even if a new trusted CA is installed on the system, an app implementing cert pinning still wouldn't trust this new CA. Seems that could be a wise move for Facebook's rivals that want to limit snooping.

Edit: on 2nd thought even if Facebook can't decrypt a particular app's traffic, just knowing how many requests it makes, how large they are, and how often, could still provide some useful insights into an app's usage.

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If the app is hard coded it shouldn't trust another cert. Note though that browsers, like Chrome, ignore cert pinning if the cert chains up to a locally trusted CA. So the answer is more "It Depends".

> Chrome does not perform pin validation when the certificate chain chains up to a private trust anchor. A key result of this policy is that private trust anchors can be used to proxy (or MITM) connections, even to pinned sites. “Data loss prevention” appliances, firewalls, content filters, and malware can use this feature to defeat the protections of key pinning.

http://www.chromium.org/Home/chromium-security/security-faq#...

EDIT: Spaced on the fact this is a phone app. While Chrome on Windows ignores certificate pins, I'm unsure if this also applies to Android / iOS root stores as well.

So what DOES pinning protect against? Certs generated by state actors with access to CA’s?

That, and (more commonly) CAs mis-issuing certificates to malicious actors due to bugs or weak internal controls.

You can enforce certificate pinning in your own native app. You can even go as far as not trusting the hookable (on a JBen device) system libraries and link in your own OpenSSL or something similar.

I was under the impression Chrome was dropping HPKP support (it was deprecated in 2017), so I imagine this would be across all products - desktop and mobile.

Chrome is dropping support for dynamic HPKP pins (pins that sites can add via headers) but not for static pins (Google domains etc.)

Source: https://bugs.chromium.org/p/chromium/issues/detail?id=779166

> OK, we're looking at removing dynamic PKP in M69. Static PKP will remain until further notice (we have no active plans to remove it right now).

AFAIK, yes. You would have to modify the application itself to disable certificate pinning.

you have root. Might be inconvenient but hardly impossible to modify files to drop your own pinned cert in other binaries.

As I've mentioned elsewhere in other threads, this app doesn't actually obtain root access (that is, it's not a jailbreak); the article/title is confusing a "root certificate" with "root access".

I know Uber and a few other apps certificate pin, since running a mitm proxy myself made Uber non-functional.

You can fix that with https://www.frida.re/

Is it possible to set this up to work like charles proxy?

Yeah, the idea is to remove pinning with frida and then your proxy will see all the traffic. There's some sample scripts here, and if you google around you'll find one for iOS: https://codeshare.frida.re/

Jailbreak required, of course.

Not without access to a jailbroken device.

You are correct!

Many apps do not do pinning currently.

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