crypto/internal/fips: handle the one possible PCT failure
Since ECDSA private keys are irredeemably malleable, an application
could construct one where the public key doesn't match the private key.
They'd be very much on their own, but crashing the program feels a bit
harsh.
Add this one to the list of issues caused by exposing the ECDSA (and
RSA) key values as big.Ints.
For #69536
Change-Id: Iaa65c73d7145e74f860ca097fa9641448442fbf9
Reviewed-on: https://go-review.googlesource.com/c/go/+/628855
Auto-Submit: Filippo Valsorda <filippo@golang.org> Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>