Replace PointGFp::check_invaraints, which would either return silently

or throw an exception, with PointGFp::on_the_curve, which returns a bool.

Update callers.

This showed several cases where check_invaraints was being called
multiple times, for instance when decoding a point with OS2ECP,
check_invaraints was called; many callers of OS2ECP would then call
check_invaraints again on the same object.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/pubkey/ecdh/ecdh.cpp b/src/pubkey/ecdh/ecdh.cpp
index bf8a57b3b..8d13e7f65 100644
--- a/src/pubkey/ecdh/ecdh.cpp
+++ b/src/pubkey/ecdh/ecdh.cpp
@@ -24,7 +24,9 @@ SecureVector<byte> ECDH_KA_Operation::agree(const byte w[], u32bit w_len)
    PointGFp point = OS2ECP(w, w_len, curve);
 
    PointGFp S = (cofactor * point) * l_times_priv;
-   S.check_invariants();
+
+   if(!S.on_the_curve())
+      throw Internal_Error("ECDH: Agreed value was not on the curve");
 
    return BigInt::encode_1363(S.get_affine_x(),
                               curve.get_p().bytes());