Implements https://tools.ietf.org/html/rfc8555#section-7.3.4 Fixes golang/go#41430 Co-authored-by: James Munnelly <james@munnelly.eu> Change-Id: Icd0337fddbff49e7e79fb9105c2679609f990285 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/269279 Run-TryBot: Katie Hockman <katie@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Trust: Katie Hockman <katie@golang.org> Trust: Roland Shoemaker <roland@golang.org> Reviewed-by: Roland Shoemaker <roland@golang.org>