On 1/27/2015 10:30 AM, James Peach wrote:
On Jan 27, 2015, at 8:18 AM, Susan Hinrichs <shinr...@network-geographics.com>
wrote:
Originally, I was planning on leaving in plugin support for both the SNI
callback and the cert callback. But as I reflect, I question that decision. I
think it adds complexity without giving more power to the plugin writer.
Both callbacks take place at the same point in the handshake. From both
callbacks you can set the certificate. Depending on the version and patch
level, only one of the callbacks will let you pause processing.
Perhaps it is better to support only point for the plugin to callback after the
client hello during the handshake processing? If we did that, ATS could adapt
depending on the linked version of openssl and the plugin would not change.
I'd still add a TS_SSL_CERT_HOOK for clarity, but I'd make it the same value as
TS_SSL_SNI_HOOK.
Why do you need to make this change? What is the compatibility impact?
Well we do need to support the certificate callbacks in openssl 1.0.2,
so we have a means to pause handshake processing to load certificates,
etc in a stock version of openssl.
If openssl 1.0.1 is linked, it would execute the plugin's callback during the
SNI callback. If openssl 1.0.2 is linked, it would execute the plugin's
callback during the certificate callback.
Did openssl 1.0.1 contain your patch? If there is no released version of
openssl that contains the original callback you added, what is is that we need
to support?
My patch was not rolled into open ssl. The only reason to continue to
support it is that we had previously supported it. If you are unable to
move to openssl 1.0.2, then at least you can patch up openssl 1.0.1
(though if you can run with a patched version you can likely upgrade too).
My second idea, would have the least impact upon people who have already
invested effort in writing plugins on the SNI callback.
Judging from your questions, you don't see a reason to support both a
SNI callback and a certificate callback either. Is that right?
What are people's thoughts?
Thanks,
Susan
On 1/27/2015 10:08 AM, Susan Hinrichs wrote:
Hi All,
With 1.0.2 openssl expanded their support of the certificate callback to handle
pausing processing during the SSL handshake negotiation. This replaces the
functionality I added to the SNI callback in my patch for openssl 1.0.1.
With TS-3319, I'm updating the ATS callback logic to support the certificate
callback if you are compiling against openssl 1.0.2.
There is a new hook constant, TS_SSL_CERT_HOOK. If you had a SNI callback that
was pausing the handshake to make decisions about the certificate, you can move
it from the TS_SSL_SNI_HOOK to the TS_SSL_CERT_HOOK.
I'm finishing tidying up TS-3319. It should be ready later today or tomorrow.
Susan
