If len_der != len_der_lax
, then we may read uninitialized memory here:
https://github.com/bitcoin-core/secp256k1/blob/912680ed8675bbf9c74c4c112ca3c41d27a295d7/src/tests.c#L4318
This should probably be handled similar to https://github.com/bitcoin-core/secp256k1/blob/912680ed8675bbf9c74c4c112ca3c41d27a295d7/src/tests.c#L4302
Same issues further below for the OpenSSL roundtrip.
Loosely related to #532 but I agree that #532 is not a good idea.