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Curious to see how they handle Chrome on Windows XP advertising sigalg support for SHA-2/ECDSA but not being able to actually validate the certificate. We provi
by prdonahue 10y ago
Curious to see how they handle Chrome on Windows XP advertising sigalg support for SHA-2/ECDSA but not being able to actually validate the certificate. We provided details[1] on the bug to Google and they agreed the behavior was incorrect, but Adam Langley felt that it wasn't worth making the change in BoringSSL:
> The code change in BoringSSL doesn't appear to be worth it. I think removing the cipher suites means that our ClientHello here is not unreasonable and, in the future, it sounds like we'll solve the problem by default by dropping XP support.
So long as nginx is examining the cipher suites in the ClientHello (as well as the TLS 1.2 signature_algorithms extension) to determine if the user agent can support ECDSA, they should be in good shape. That's the subsequent check[2] we ended up implementing.
[1] https://bugs.chromium.org/p/chromium/issues/detail?id=409901 https://bugs.chromium.org/p/chromium/issues/detail?id=409901
[2] https://blog.cloudflare.com/tls-certificate-optimization-technical-details/ https://blog.cloudflare.com/tls-certificate-optimization-tec...
- mtgx 10y agoGoogle stopped supporting Windows XP last month. http://arstechnica.com/gadgets/2016/04/chrome-50-ends-support-for-windows-xp-os-x-10-6-other-old-versions/ http://arstechnica.com/gadgets/2016/04/chrome-50-ends-suppor...
- prdonahue 10y agoRight, but that doesn't immediately remove the millions of XP machines still in use. My question was how nginx handles those inbound connections that falsely claim they can validate SHA-2/ECDSA signatures.
- derefr 10y agoCan't we just put up a bounty for a computer worm that wipes out all the XP machines in the world, and then stop having this conversation? :)
- dottedmag 10y agoX.org bugzilla quip: "with a non-multisync monitor, it would destroy.. the.. monitor.. so- Our job here is to make sure that there are no such monitors left in the world. --Keith Packard, LCA2007"
- Gregordinary 10y agoLooks like that bug was reported for Chrome 37, which is the last version of Chrome to rely on the underlying OS for validating SHA-2 Certificates. Chrome 38+ should be able to validate the cert. "Chrome is capable of supporting SHA-2 certificates as of version 1.0, however through version 37 it is dependent on the operating system. For instance, on Windows Server 2003 without MS13-095 or Windows XP SP2 Chrome will not connect to pages using SHA-2 certs. Applying MS13-095 to Server 2003, or SP3 to Windows XP will allow Chrome to support SHA-2 on these legacy systems. Chrome 38+ can validate SHA-2 certificates independently, even on systems like Server 2003 without MS13-095 applied." Source: https://support.globalsign.com/customer/en/portal/articles/1499561-sha-256-compatibility#1a https://support.globalsign.com/customer/en/portal/articles/1...
- prdonahue 10y agoYou're missing the point. Yes, Google hacked in SHA-2 support into M38[1] but not ECDSA support, which is why them advertising the SHA-2/ECDSA pair is bad. [1] -https://chromium.googlesource.com/chromium/src/+/25e2bc0a95354727342757ba71582bf4de638fe8 https://chromium.googlesource.com/chromium/src/+/25e2bc0a953...
- Gregordinary 10y agoAh, I see what you're saying. Thank you for the clarification.