This is to simplify
https://boringssl-review.googlesource.com/c/boringssl/+/24445/.
Setting or changing an EC_KEY's group after the public or private keys
have been configured is quite awkward w.r.t. consistency checks. It
becomes additionally messy if we mean to store private keys as
EC_SCALARs (and avoid the BIGNUM timing leak), whose size is
curve-dependent.
Instead, require that callers configure the group before setting either
half of the keypair. Additionally, reject EC_KEY_set_group calls that
change the group. This will simplify clearing one more BIGNUM timing
leak.
Update-Note: This will break code which sets the group and key in a
weird order. I checked calls of EC_KEY_new and confirmed they all
set the group first. If I missed any, let me know.
Change-Id: Ie89f90a318b31b6b98f71138e5ff3de5323bc9a6
Reviewed-on: https://boringssl-review.googlesource.com/24425
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
5bcaa113e2