Add RSA max key length test (#2205)

Author: StephenButtolph

staking/large_rsa_key.cert

@@ -0,0 +1,30 @@
+// Copyright (C) 2019-2023, Ava Labs, Inc. All rights reserved.
+// See the file LICENSE for licensing terms.
+
+package staking
+
+import (
+	"testing"
+
+	_ "embed"
+
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	//go:embed large_rsa_key.cert
+	largeRSAKeyCert []byte
+	//go:embed large_rsa_key.sig
+	largeRSAKeySig []byte
+)
+
+func TestCheckSignatureLargePublicKey(t *testing.T) {
+	require := require.New(t)
+
+	cert, err := ParseCertificate(largeRSAKeyCert)
+	require.NoError(err)
+
+	msg := []byte("TODO: put something clever")
+	err = CheckSignature(cert, msg, largeRSAKeySig)
+	require.ErrorIs(err, ErrInvalidRSAPublicKey)
+}