tree efa5f27762239e861f07f88ca7a96a1dafa59d46
parent e15019572b3294e3410a4ee6d4bcbbf76450df31
author David Benjamin <davidben@google.com> 1513456440 -0500
committer CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> 1515017711 +0000

Tighten EC_KEY's association with its group.

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>