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Chrome does do pinning, but ignores pins when the cert parent is a privately installed cert (because this is a "feature" used by many enterprises). """ Chrome

by semenko 12y ago

Chrome does do pinning, but ignores pins when the cert parent is a privately installed cert (because this is a "feature" used by many enterprises). """ 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. """ See: http://www.chromium.org/Home/chromium-security/security-faq#TOC-How-does-key-pinning-interact-with-local-proxies-and-filters- http://www.chromium.org/Home/chromium-security/security-faq#...

kinofcain 12y ago
And the rationale: "We deem this acceptable because the proxy or MITM can only be effective if the client machine has already been configured to trust the proxy’s issuing certificate" I think that's fair, or at least it has traditionally been a fair assumption for most users. The issue here is that your hardware vendor has compromised your machine, so that is no longer a fair assumption.
- MichaelGG 12y ago
  Well continue the process. Suppose Chrome did flag such things. That'd break a lot of "legitimate" use cases, and someone would implement a workaround. For instance, they could just patch the Chrome binaries to disable the warnings or change the pinning logic. Insert their own certs into the pin list. Without something like Intel SGX, you or Google can't totally win. Of course, Chrome could give some indication like a lock+eyeball or something, and hope the interception vendors are too lazy to bother modifying the code. They could also only disable warnings if the machine is connected to a domain or other management system.
- cesarb 12y ago
  There's another issue with ignoring cert pining with user-added root certificates: if you add a root certificate that's missing on your client machine (for instance CAcert or your national CA like ICP-Brasil), the CA you added can bypass pining, even though it shouldn't be able to. On Mozilla, you can configure it to never bypass pining (security.cert_pinning.enforcement_level set to 2, see https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinning https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinn... ); I don't know how to do it on Chrome.
sitkack 12y ago
TIL Google is ok if you get backdoored by your boss.
- vpeters25 12y ago
  The company I work for has a strict policy of no direct outbound connections from the corporate network. This is to prevent (or just make harder) for compromised machines from "phoning home". This has the unfortunate side effect that all internet traffic must go through a proxy, they have to MiTM SSL traffic. I just use my smartphone's data for any personal internet browsing.
  - skuhn 12y ago
    Well you don't have to MITM SSL in order to proxy it, it can be done in other ways. They probably choose to do so in order to see the details of the request.
    - vpeters25 12y ago
      Correct, the firewall intercepts all traffic looking for potential compromises and blocks it. Given all these corporations getting hacked, such measures seem necessary.
      - lmm 12y ago
        Conclusion does not follow from premise. Once an attacker's code is running on machines that have access to sensitive data, you've already lost - there's no way to prevent it smuggling the data out in legitimate-looking requests. The right way is to stop the bad stuff getting in in the first place.
        ent 12y ago
        Not all attacks are perfect. It's true that an attacker can potentially do anything once in control of machines with sensitive data, but it doesn't mean that all hope is lost. If an intrusion detection system catches some x% of potential threats, it can easily be worth it.
TheLoneWolfling 12y ago
Because that's not exploitable or anything.
osivertsson 12y ago
Thank for bringing this to my attention. I guess I should look into the Chromium source to disable this MITM "feature"... I'm really too busy so if anyone else does this I'd much appreciate a patch.

by semenko 12y ago

kinofcain 12y ago

And the rationale: "We deem this acceptable because the proxy or MITM can only be effective if the client machine has already been configured to trust the proxy’s issuing certificate" I think that's fair, or at least it has traditionally been a fair assumption for most users. The issue here is that your hardware vendor has compromised your machine, so that is no longer a fair assumption.

MichaelGG 12y ago
Well continue the process. Suppose Chrome did flag such things. That'd break a lot of "legitimate" use cases, and someone would implement a workaround. For instance, they could just patch the Chrome binaries to disable the warnings or change the pinning logic. Insert their own certs into the pin list. Without something like Intel SGX, you or Google can't totally win. Of course, Chrome could give some indication like a lock+eyeball or something, and hope the interception vendors are too lazy to bother modifying the code. They could also only disable warnings if the machine is connected to a domain or other management system.
cesarb 12y ago
There's another issue with ignoring cert pining with user-added root certificates: if you add a root certificate that's missing on your client machine (for instance CAcert or your national CA like ICP-Brasil), the CA you added can bypass pining, even though it shouldn't be able to. On Mozilla, you can configure it to never bypass pining (security.cert_pinning.enforcement_level set to 2, see https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinning https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinn... ); I don't know how to do it on Chrome.

sitkack 12y ago

TIL Google is ok if you get backdoored by your boss.

vpeters25 12y ago
The company I work for has a strict policy of no direct outbound connections from the corporate network. This is to prevent (or just make harder) for compromised machines from "phoning home". This has the unfortunate side effect that all internet traffic must go through a proxy, they have to MiTM SSL traffic. I just use my smartphone's data for any personal internet browsing.
- skuhn 12y ago
  Well you don't have to MITM SSL in order to proxy it, it can be done in other ways. They probably choose to do so in order to see the details of the request.
  - vpeters25 12y ago
    Correct, the firewall intercepts all traffic looking for potential compromises and blocks it. Given all these corporations getting hacked, such measures seem necessary.
    - lmm 12y ago
      Conclusion does not follow from premise. Once an attacker's code is running on machines that have access to sensitive data, you've already lost - there's no way to prevent it smuggling the data out in legitimate-looking requests. The right way is to stop the bad stuff getting in in the first place.
      - ent 12y ago
        Not all attacks are perfect. It's true that an attacker can potentially do anything once in control of machines with sensitive data, but it doesn't mean that all hope is lost. If an intrusion detection system catches some x% of potential threats, it can easily be worth it.

TheLoneWolfling 12y ago

Because that's not exploitable or anything.

osivertsson 12y ago

Thank for bringing this to my attention. I guess I should look into the Chromium source to disable this MITM "feature"... I'm really too busy so if anyone else does this I'd much appreciate a patch.