otr: reject private keys with parameters <= 0.

This serves as a basic sanity check and also prevents malformed private
keys from setting P=0 and consuming large amounts of CPU and memory in
the Exp call.

Change-Id: Ife22069b989a7347d8deaaf13030df82ee59e87b
Reviewed-on: https://go-review.googlesource.com/35246
Run-TryBot: Adam Langley <agl@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed