[gnutls-devel] Speedup idea...

[Nikos Mavrogiannopoulos]

Hi Tim,
 During handshake you must have a certificate credentials structure set or the handshake will fail as you say. It may be empty though,  it doesn't need to have ca certificates set. You can load these prior to calling the certificate verify peers function. 

This violates the rule that the credentials must be read only after being set on a session, but on client side they are only used during verification. An alternative approach is to verify the peers certificates using a trust list.

Btw out of curiosity,  have you tested the same operation in fedora which uses the p11kit trust module instead of files?


On 2 August 2016 16:47:54 CEST, Tim Ruehsen <tim.ruehsen at gmx.de> wrote:
>Hi Nikos, hi list.
>
>Right after gnutls_init() the wget/wget2 code loads the certificate
>list - all 
>available certs. That currently are 172 CA certs on Debian Sid right
>now.
>
>This takes 15-20ms here (i3, 3.1GHz), when the files are already
>cached.
>
>With session resumption (or False Start) and TCP Fast Open I just have
>1xRTT 
>tradeoff for TLS handshake. With slightly less than 33ms RTT that let's
>me 
>theoretically fetch a file via HTTPS in ~66ms. But I have this damn
>load-them- 
>all-CA (gnutls_certificate_set_x509_system_trust()) taking another
>15ms, so I 
>am at ~81ms for fetching a file. This is quite a big portion of the
>overall 
>download time - having lower RTT makes this relation even worse.
>
>My quick solution was (I thought it could work), why not load the certs
>during 
>the handshake. Right after the first write(), when the handshake waits
>for the 
>server answer, I have 33ms of time that I can use for loading.
>
>But then... in ciphersuites.c/_gnutls_remove_unwanted_ciphersuites(),
>you 
>"unload" all ciphersuites not needed by the certs, resulting in an
>error if no 
>certs are loaded (because having 0 ciphersuites for client hello).
>
>But everything works like a charm (I really have just 66ms total time)
>when I 
>remove these lines from
>ciphersuites.c/_gnutls_remove_unwanted_ciphersuites():
>
>		if (!session->internals.premaster_set &&
>		    _gnutls_get_kx_cred(session, kx) == NULL) {
>			continue;
>		}
>
>I guess, all cipher suites known by GnuTLS (or set via priorities) are
>offered 
>by the client hello !?
>
>What can we/I do to make the above scenario 'officially' work ?
>Wouldn't it be good to offer all cipher suites set by
>gnutls_priority_set() ?
>AFAIR, OpenSSL do not need certs to be loaded before client hello...
>but I 
>might be wrong.
>
>Regards, Tim
>
>
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-- 
Sent fron my mobile. Please excuse my brevity.