crypto/tls: support dynamic NameToCertificate mapping in addition to static map for dynamic SNI certificate generation

[gopherbot]

by ox.to.a.cart:

tls.Config includes a NameToCertificate map that allows tls servers to specify
certificates to use for specific SNI names.  I am building an HTTP proxy that
man-in-the-middle's connections, and it needs to be able to dynamically generate
certificates for any SNI name that comes in.  Pregenerating the certificates is an
intractable problem since I would have to generate certificates for all known and even
possible server names in the world.

I've patched Go to allow the inclusion of an optional CertificateForName function on
tls.Config that, if present, provides a hook for the server to generate certificates on
the fly for a given SNI name.

The changeset in question is here:

https://code.google.com/r/oxtoacart-gomitm/source/detail?r=a696a331eda198996f567018c54d3551adf8d1de&;name=release-branch.go1.2

I use it in gomitm, which is here:

https://github.com/oxtoacart/gomitm/blob/master/mitm.go

[ianlancetaylor]

Comment 1:

If you have a specific patch to propose, please follow the procedure described in
http://golang.org/doc/contribute.html.  Thanks.

Labels changed: added repo-main.

[rsc]

Comment 2:

Labels changed: added release-none.

Status changed to Accepted.

[gopherbot]

Comment 3 by [email protected]:

Happy to see this accepted!  There's a code review that's ready to go for this (pending
any recent changes in 1.3), I'm just waiting on 1.3 to be released before I resubmit.
https://golang.org/cl/81260045/

[stevvooe]

Comment 4:

Go 1.3 is out. It would be great if you could resubmit your review!

[gopherbot]

Comment 5 by [email protected]:

An enhancement for this has been submitted:
https://code.google.com/p/go/source/detail?r=957bd50e2b82

[agl]

Comment 6:

Status changed to Fixed.