4 ms·

Are you looking at anything beyond the SignatureAlgorithms TLS extension? That is the obvious solution, but I know there are a few browsers that support sha256

by ryan-c 11y ago

Are you looking at anything beyond the SignatureAlgorithms TLS extension? That is the obvious solution, but I know there are a few browsers that support sha256 certificates that don't send that extension.

eastdakota 11y ago
Yes. It's above my pay grade to walk through what we're doing to fingerprint TLS connections. However, we will provide a thorough blog on what we're doing and open source the algorithm we're using.
- ryan-c 11y ago
  "above my pay grade" is an odd phrase to use considering that your profile says you're the CEO, but I'm guessing you mainly mean you're not familiar with the details? I'm pretty sure I know exactly what you're doing, but I'm very interested to see how much of the secret sauce you'll share.
  - eastdakota 11y ago
    Yes, I was being a bit flip. But only a bit. We strive to be a company where engineering drives our priorities. While, a long, long time ago, I wrote a tiny bit of the code that became CloudFlare, there's no way I'd be trusted to do that today. There are engineers on our team whose salaries are far higher than mine. And, in this case, while I've been briefed on what we're doing, I don't feel comfortable enough with the details to comment on them. Thankfully, the people who are should be getting to work in London soon and I've asked that they watch this thread. PS - I have no problem sharing the complete "secret sauce" as the biggest risk here to us is not competition but that CAs after December 31, 2015 won't be allowed to issue SHA1 certificates anymore. The more organizations that can responsibly support SHA1 fallback, regardless of whether they're CloudFlare customers, the more likely it is we can convince the CA/B forum to allow the extension of the issuance of SHA1 certs to responsible parties.
    - ryan-c 11y ago
      I have somewhat mixed feelings regarding SHA1 support. On the one hand, it is useful in some cases to support legacy clients that "can't" upgrade. On the other hand, I don't feel too bad about cutting off clients that are basically a blight on the internet - many of these applications have numerous security issues beyond weak crypto. As far as the CAs and browsers go, I would expect them to push back based on concern of not being able to enforce "you must support SHA256 and can only use SHA1 as a fallback". The browser vendors have the threat of scary SSL error screens, but people often click through those anyway, and habituating people to doing so is bad. Exceptions could be disabled, but that might just push more people to legacy browsers because they "work". I think this is gonna end up being one of those "pick the least bad solution" kind of things.
  - deleted 11y ago
    [deleted]
jgrahamc 11y ago
We actually look at the sigalgs and the cipher suites and have code that understands the behavior of different browsers. For example, Chrome on Windows XP sends ECDSA/SHA256 in its sigalgs, but doesn't actually support ECDSA.
- ryan-c 11y ago
  I figured you'd look at the cipher suites and have a list of fingerprints for ones that needed special handling. I'm pretty surprised that WinXP Chrome falsely claims support for ECDSA... Does the switch to BoringSSL fix that, or no because Chrome's relying on the built in Windows certificate store/validation?

by ryan-c 11y ago

eastdakota 11y ago

Yes. It's above my pay grade to walk through what we're doing to fingerprint TLS connections. However, we will provide a thorough blog on what we're doing and open source the algorithm we're using.

ryan-c 11y ago
"above my pay grade" is an odd phrase to use considering that your profile says you're the CEO, but I'm guessing you mainly mean you're not familiar with the details? I'm pretty sure I know exactly what you're doing, but I'm very interested to see how much of the secret sauce you'll share.
- eastdakota 11y ago
  Yes, I was being a bit flip. But only a bit. We strive to be a company where engineering drives our priorities. While, a long, long time ago, I wrote a tiny bit of the code that became CloudFlare, there's no way I'd be trusted to do that today. There are engineers on our team whose salaries are far higher than mine. And, in this case, while I've been briefed on what we're doing, I don't feel comfortable enough with the details to comment on them. Thankfully, the people who are should be getting to work in London soon and I've asked that they watch this thread. PS - I have no problem sharing the complete "secret sauce" as the biggest risk here to us is not competition but that CAs after December 31, 2015 won't be allowed to issue SHA1 certificates anymore. The more organizations that can responsibly support SHA1 fallback, regardless of whether they're CloudFlare customers, the more likely it is we can convince the CA/B forum to allow the extension of the issuance of SHA1 certs to responsible parties.
  - ryan-c 11y ago
    I have somewhat mixed feelings regarding SHA1 support. On the one hand, it is useful in some cases to support legacy clients that "can't" upgrade. On the other hand, I don't feel too bad about cutting off clients that are basically a blight on the internet - many of these applications have numerous security issues beyond weak crypto. As far as the CAs and browsers go, I would expect them to push back based on concern of not being able to enforce "you must support SHA256 and can only use SHA1 as a fallback". The browser vendors have the threat of scary SSL error screens, but people often click through those anyway, and habituating people to doing so is bad. Exceptions could be disabled, but that might just push more people to legacy browsers because they "work". I think this is gonna end up being one of those "pick the least bad solution" kind of things.
- deleted 11y ago
  [deleted]

jgrahamc 11y ago

We actually look at the sigalgs and the cipher suites and have code that understands the behavior of different browsers. For example, Chrome on Windows XP sends ECDSA/SHA256 in its sigalgs, but doesn't actually support ECDSA.

ryan-c 11y ago
I figured you'd look at the cipher suites and have a list of fingerprints for ones that needed special handling. I'm pretty surprised that WinXP Chrome falsely claims support for ECDSA... Does the switch to BoringSSL fix that, or no because Chrome's relying on the built in Windows certificate store/validation?