MarshalCBOR should fail with a signature >=SignatureMaxLength, which will fail to decode

[wadealexc]

UnmarshalCBOR limits payload to 200 bytes (SigType plus Data), but MarshalCBOR will serialize a signature that would fail to decode for this reason.

go-state-types/crypto/signature.go

Lines 76 to 78 in 7cab7f0

	if l > SignatureMaxLength {
	return fmt.Errorf("string too long")
	}