var ext pkix.Extension
	if !der.ReadASN1ObjectIdentifier(&ext.Id) {
		return ext, errors.New("x509: malformed extension OID field")
	}
	if der.PeekASN1Tag(cryptobyte_asn1.BOOLEAN) {
		if !der.ReadASN1Boolean(&ext.Critical) {
			return ext, errors.New("x509: malformed extension critical field")
		}
	}
	var val cryptobyte.String
	if !der.ReadASN1(&val, cryptobyte_asn1.OCTET_STRING) {