// default value.
	if (len(params.Hash.Parameters.FullBytes) != 0 && !bytes.Equal(params.Hash.Parameters.FullBytes, asn1.NullBytes)) ||
		!params.MGF.Algorithm.Equal(oidMGF1) ||
		!mgf1HashFunc.Algorithm.Equal(params.Hash.Algorithm) ||
		(len(mgf1HashFunc.Parameters.FullBytes) != 0 && !bytes.Equal(mgf1HashFunc.Parameters.FullBytes, asn1.NullBytes)) ||
		params.TrailerField != 1 {
		return UnknownSignatureAlgorithm
	}

	switch {
	case oid.Equal(oidPublicKeyRSA):
		// RSA public keys must have a NULL in the parameters.
		// See RFC 3279, Section 2.3.1.
		if !bytes.Equal(params.FullBytes, asn1.NullBytes) {
			return nil, errors.New("x509: RSA key missing NULL parameters")
		}

		p := &pkcs1PublicKey{N: new(big.Int)}
		if !der.ReadASN1(&der, cryptobyte_asn1.SEQUENCE) {

			return bytesEncoder(nil), nil
		}
	}

	if v.Type() == rawValueType {
		rv := v.Interface().(RawValue)
		if len(rv.FullBytes) != 0 {
			return bytesEncoder(rv.FullBytes), nil
		}

		t := new(taggedEncoder)

		t.tag = bytesEncoder(appendTagAndLength(t.scratch[:0], tagAndLength{rv.Class, rv.Tag, len(rv.Bytes), rv.IsCompound}))

		{"Flag", Type, 0},
		{"Marshal", Func, 0},
		{"MarshalWithParams", Func, 10},
		{"NullBytes", Var, 9},
		{"NullRawValue", Var, 9},
		{"ObjectIdentifier", Type, 0},
		{"RawContent", Type, 0},
		{"RawValue", Type, 0},
		{"RawValue.Bytes", Field, 0},
		{"RawValue.Class", Field, 0},
		{"RawValue.FullBytes", Field, 0},
		{"RawValue.IsCompound", Field, 0},
		{"RawValue.Tag", Field, 0},

		if !detail.isRSAPSS {
			continue
		}
		generated := generateParams(detail.hash)
		if !bytes.Equal(detail.params.FullBytes, generated) {
			t.Errorf("hardcoded parameters for %s didn't match generated parameters: got (generated) %x, wanted (hardcoded) %x", detail.hash, generated, detail.params.FullBytes)
		}
	}
}

func TestUnknownExtKey(t *testing.T) {
	const errorContains = "unknown extended key usage"