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> You can't support Windows XP users who use IE anymore with HTTPs. Sure you can. Just ask a CA that has an old root trusted by XP but no longer trusted by mod
by jvehent 10y ago
> You can't support Windows XP users who use IE anymore with HTTPs.
Sure you can. Just ask a CA that has an old root trusted by XP but no longer trusted by modern browsers, and they'll issue a SHA-1 cert for you without risking to get kicked out of the truststores.
- Negitivefrags 10y agoAnd what about all the modern browsers you also need to support?
- agwa 10y agoYou serve them a SHA-2 certificate. (In TLSv1.2 the client's supported hash algorithms are included in the handshake. Clients that don't support TLSv1.2 are probably fine with SHA-1. You can also use heuristics based on the ciphersuite to determine whether a client should get a SHA-1 certificate or not.)
- pfg 10y agoIt's possible to determine whether a client supports certificates using SHA-2 by analyzing the ClientHello and use that to switch between a SHA-1 and SHA-2 certificate. CloudFlare[1] and some of the bigger sites like Facebook have done this. [1]: https://blog.cloudflare.com/sha-1-deprecation-no-browser-left-behind/ https://blog.cloudflare.com/sha-1-deprecation-no-browser-lef...
- prdonahue 10y agoAnd here's the technical detail of how we do it: https://blog.cloudflare.com/tls-certificate-optimization-technical-details/ https://blog.cloudflare.com/tls-certificate-optimization-tec....
- Negitivefrags 10y agoIs there actually an open source implementation of this though? I've looked, but never found one, though that was quite some time ago. Perhaps things have changed. This approach is beyond the ability of most to implement for themselves if they don't have support from their webserver for it.
- jvehent 10y agoYou can do it with HAProxy by checking for SNI and falling back to a SHA1 cert when the extension is absent. https://jve.linuxwall.info/blog/index.php?post/2015/10/04/SHA1/SHA256-certificate-switching-with-HAProxy https://jve.linuxwall.info/blog/index.php?post/2015/10/04/SH...
- agwa 10y agoA recent combination of Apache and OpenSSL has support for certificate switching based on key algorithm. You can serve an ECDSA+SHA2 certificate to clients that support ECDSA, and an RSA+SHA1 certificate to clients that don't. I'm pretty sure that all clients that reject SHA1 support ECDSA, so this should work.
- 0x0 10y agoWell I guess you just discovered WoSign's next business plan! Haha
- sep27throw 10y agoOK, I'll bite: which CA, specifically, will do this? I'd sure like to keep communicating with XP after my current SHA1 cert expires this December.