crypto: use rand.IsDefaultReader instead of comparing to boring.RandReader
Several crypto functions accepting a rand parameter skip calling
boringcrypto when the rand is not boring.RandReader.
The new crypto/internal/rand package currently defines its own Reader
that wraps boring.RandReader. That will unintentionally bypass
boringcrypto when used with the aforementioned functions.
Fixes #76672
Change-Id: Ie0c1345530c734a23815f9593590b5d32604f54d
Reviewed-on: https://go-review.googlesource.com/c/go/+/726220 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Filippo Valsorda <filippo@golang.org> Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>