ASN.1 DER (Abstract Syntax Notation One, Distinguished Encoding Rules): Java parsing library

ASN.1 (Abstract Syntax Notation One) DER (Distinguished Encoding Rules) is a standard-backed serialization scheme used in many different use-cases. Particularly popular usage scenarios are X.509 certificates and some telecommunication / networking protocols.

DER is self-describing encoding scheme which allows representation of simple, atomic data elements, such as strings and numbers, and complex objects, such as sequences of other elements.

DER is a subset of BER (Basic Encoding Rules), with an emphasis on being non-ambiguous: there's always exactly one canonical way to encode a data structure defined in terms of ASN.1 using DER.

This spec allows full parsing of format syntax, but to understand the semantics, one would typically require a dictionary of Object Identifiers (OIDs), to match OID bodies against some human-readable list of constants. OIDs are covered by many different standards, so typically it's simpler to use a pre-compiled list of them, such as:

  • https://www.cs.auckland.ac.nz/~pgut001/dumpasn1.cfg
  • http://oid-info.com/
  • https://www.alvestrand.no/objectid/top.html

File extension

der

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of ASN.1 DER (Abstract Syntax Notation One, Distinguished Encoding Rules) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Java generated by Kaitai Struct depends on the Java runtime library. You have to install it before you can parse data.

The Java runtime library is published in the Maven Central Repository. Refer to the artifact page for instructions how to add it into your project with the build tool that you use.

Code

Parse a local file and get structure in memory:

Asn1Der data = Asn1Der.fromFile("path/to/local/file.der");

Or parse structure from a byte array:

byte[] someArray = new byte[] { ... };
Asn1Der data = new Asn1Der(new ByteBufferKaitaiStream(someArray));

After that, one can get various attributes from the structure by invoking getter methods like:

data.typeTag() // => get type tag

Java source code to parse ASN.1 DER (Abstract Syntax Notation One, Distinguished Encoding Rules)

Asn1Der.java

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

import io.kaitai.struct.ByteBufferKaitaiStream;
import io.kaitai.struct.KaitaiStruct;
import io.kaitai.struct.KaitaiStream;
import java.io.IOException;
import java.util.Map;
import java.util.HashMap;
import java.util.ArrayList;
import java.nio.charset.Charset;


/**
 * ASN.1 (Abstract Syntax Notation One) DER (Distinguished Encoding
 * Rules) is a standard-backed serialization scheme used in many
 * different use-cases. Particularly popular usage scenarios are X.509
 * certificates and some telecommunication / networking protocols.
 * 
 * DER is self-describing encoding scheme which allows representation
 * of simple, atomic data elements, such as strings and numbers, and
 * complex objects, such as sequences of other elements.
 * 
 * DER is a subset of BER (Basic Encoding Rules), with an emphasis on
 * being non-ambiguous: there's always exactly one canonical way to
 * encode a data structure defined in terms of ASN.1 using DER.
 * 
 * This spec allows full parsing of format syntax, but to understand
 * the semantics, one would typically require a dictionary of Object
 * Identifiers (OIDs), to match OID bodies against some human-readable
 * list of constants. OIDs are covered by many different standards,
 * so typically it's simpler to use a pre-compiled list of them, such
 * as:
 * 
 * * https://www.cs.auckland.ac.nz/~pgut001/dumpasn1.cfg
 * * http://oid-info.com/
 * * https://www.alvestrand.no/objectid/top.html
 * @see <a href="https://www.itu.int/rec/T-REC-X.690-201508-I/en">Source</a>
 */
public class Asn1Der extends KaitaiStruct {
    public static Asn1Der fromFile(String fileName) throws IOException {
        return new Asn1Der(new ByteBufferKaitaiStream(fileName));
    }

    public enum TypeTag {
        END_OF_CONTENT(0),
        BOOLEAN(1),
        INTEGER(2),
        BIT_STRING(3),
        OCTET_STRING(4),
        NULL_VALUE(5),
        OBJECT_ID(6),
        OBJECT_DESCRIPTOR(7),
        EXTERNAL(8),
        REAL(9),
        ENUMERATED(10),
        EMBEDDED_PDV(11),
        UTF8STRING(12),
        RELATIVE_OID(13),
        SEQUENCE_10(16),
        PRINTABLE_STRING(19),
        IA5STRING(22),
        SEQUENCE_30(48),
        SET(49);

        private final long id;
        TypeTag(long id) { this.id = id; }
        public long id() { return id; }
        private static final Map<Long, TypeTag> byId = new HashMap<Long, TypeTag>(19);
        static {
            for (TypeTag e : TypeTag.values())
                byId.put(e.id(), e);
        }
        public static TypeTag byId(long id) { return byId.get(id); }
    }

    public Asn1Der(KaitaiStream _io) {
        this(_io, null, null);
    }

    public Asn1Der(KaitaiStream _io, KaitaiStruct _parent) {
        this(_io, _parent, null);
    }

    public Asn1Der(KaitaiStream _io, KaitaiStruct _parent, Asn1Der _root) {
        super(_io);
        this._parent = _parent;
        this._root = _root == null ? this : _root;
        _read();
    }
    private void _read() {
        this.typeTag = TypeTag.byId(this._io.readU1());
        this.len = new LenEncoded(this._io, this, _root);
        {
            TypeTag on = typeTag();
            if (on != null) {
                switch (typeTag()) {
                case PRINTABLE_STRING: {
                    this._raw_body = this._io.readBytes(len().result());
                    KaitaiStream _io__raw_body = new ByteBufferKaitaiStream(_raw_body);
                    this.body = new BodyPrintableString(_io__raw_body, this, _root);
                    break;
                }
                case SEQUENCE_10: {
                    this._raw_body = this._io.readBytes(len().result());
                    KaitaiStream _io__raw_body = new ByteBufferKaitaiStream(_raw_body);
                    this.body = new BodySequence(_io__raw_body, this, _root);
                    break;
                }
                case SET: {
                    this._raw_body = this._io.readBytes(len().result());
                    KaitaiStream _io__raw_body = new ByteBufferKaitaiStream(_raw_body);
                    this.body = new BodySequence(_io__raw_body, this, _root);
                    break;
                }
                case SEQUENCE_30: {
                    this._raw_body = this._io.readBytes(len().result());
                    KaitaiStream _io__raw_body = new ByteBufferKaitaiStream(_raw_body);
                    this.body = new BodySequence(_io__raw_body, this, _root);
                    break;
                }
                case UTF8STRING: {
                    this._raw_body = this._io.readBytes(len().result());
                    KaitaiStream _io__raw_body = new ByteBufferKaitaiStream(_raw_body);
                    this.body = new BodyUtf8string(_io__raw_body, this, _root);
                    break;
                }
                case OBJECT_ID: {
                    this._raw_body = this._io.readBytes(len().result());
                    KaitaiStream _io__raw_body = new ByteBufferKaitaiStream(_raw_body);
                    this.body = new BodyObjectId(_io__raw_body, this, _root);
                    break;
                }
                default: {
                    this.body = this._io.readBytes(len().result());
                    break;
                }
                }
            } else {
                this.body = this._io.readBytes(len().result());
            }
        }
    }
    public static class BodySequence extends KaitaiStruct {
        public static BodySequence fromFile(String fileName) throws IOException {
            return new BodySequence(new ByteBufferKaitaiStream(fileName));
        }

        public BodySequence(KaitaiStream _io) {
            this(_io, null, null);
        }

        public BodySequence(KaitaiStream _io, Asn1Der _parent) {
            this(_io, _parent, null);
        }

        public BodySequence(KaitaiStream _io, Asn1Der _parent, Asn1Der _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.entries = new ArrayList<Asn1Der>();
            {
                int i = 0;
                while (!this._io.isEof()) {
                    this.entries.add(new Asn1Der(this._io));
                    i++;
                }
            }
        }
        private ArrayList<Asn1Der> entries;
        private Asn1Der _root;
        private Asn1Der _parent;
        public ArrayList<Asn1Der> entries() { return entries; }
        public Asn1Der _root() { return _root; }
        public Asn1Der _parent() { return _parent; }
    }
    public static class BodyUtf8string extends KaitaiStruct {
        public static BodyUtf8string fromFile(String fileName) throws IOException {
            return new BodyUtf8string(new ByteBufferKaitaiStream(fileName));
        }

        public BodyUtf8string(KaitaiStream _io) {
            this(_io, null, null);
        }

        public BodyUtf8string(KaitaiStream _io, Asn1Der _parent) {
            this(_io, _parent, null);
        }

        public BodyUtf8string(KaitaiStream _io, Asn1Der _parent, Asn1Der _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.str = new String(this._io.readBytesFull(), Charset.forName("UTF-8"));
        }
        private String str;
        private Asn1Der _root;
        private Asn1Der _parent;
        public String str() { return str; }
        public Asn1Der _root() { return _root; }
        public Asn1Der _parent() { return _parent; }
    }

    /**
     * @see <a href="https://docs.microsoft.com/en-us/windows/desktop/SecCertEnroll/about-object-identifier">Source</a>
     */
    public static class BodyObjectId extends KaitaiStruct {
        public static BodyObjectId fromFile(String fileName) throws IOException {
            return new BodyObjectId(new ByteBufferKaitaiStream(fileName));
        }

        public BodyObjectId(KaitaiStream _io) {
            this(_io, null, null);
        }

        public BodyObjectId(KaitaiStream _io, Asn1Der _parent) {
            this(_io, _parent, null);
        }

        public BodyObjectId(KaitaiStream _io, Asn1Der _parent, Asn1Der _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.firstAndSecond = this._io.readU1();
            this.rest = this._io.readBytesFull();
        }
        private Integer first;
        public Integer first() {
            if (this.first != null)
                return this.first;
            int _tmp = (int) ((firstAndSecond() / 40));
            this.first = _tmp;
            return this.first;
        }
        private Integer second;
        public Integer second() {
            if (this.second != null)
                return this.second;
            int _tmp = (int) (KaitaiStream.mod(firstAndSecond(), 40));
            this.second = _tmp;
            return this.second;
        }
        private int firstAndSecond;
        private byte[] rest;
        private Asn1Der _root;
        private Asn1Der _parent;
        public int firstAndSecond() { return firstAndSecond; }
        public byte[] rest() { return rest; }
        public Asn1Der _root() { return _root; }
        public Asn1Der _parent() { return _parent; }
    }
    public static class LenEncoded extends KaitaiStruct {
        public static LenEncoded fromFile(String fileName) throws IOException {
            return new LenEncoded(new ByteBufferKaitaiStream(fileName));
        }

        public LenEncoded(KaitaiStream _io) {
            this(_io, null, null);
        }

        public LenEncoded(KaitaiStream _io, Asn1Der _parent) {
            this(_io, _parent, null);
        }

        public LenEncoded(KaitaiStream _io, Asn1Der _parent, Asn1Der _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.b1 = this._io.readU1();
            if (b1() == 130) {
                this.int2 = this._io.readU2be();
            }
            if (b1() == 129) {
                this.int1 = this._io.readU1();
            }
        }
        private Integer result;
        public Integer result() {
            if (this.result != null)
                return this.result;
            int _tmp = (int) ((b1() == 129 ? int1() : (b1() == 130 ? int2() : b1())));
            this.result = _tmp;
            return this.result;
        }
        private int b1;
        private Integer int2;
        private Integer int1;
        private Asn1Der _root;
        private Asn1Der _parent;
        public int b1() { return b1; }
        public Integer int2() { return int2; }
        public Integer int1() { return int1; }
        public Asn1Der _root() { return _root; }
        public Asn1Der _parent() { return _parent; }
    }
    public static class BodyPrintableString extends KaitaiStruct {
        public static BodyPrintableString fromFile(String fileName) throws IOException {
            return new BodyPrintableString(new ByteBufferKaitaiStream(fileName));
        }

        public BodyPrintableString(KaitaiStream _io) {
            this(_io, null, null);
        }

        public BodyPrintableString(KaitaiStream _io, Asn1Der _parent) {
            this(_io, _parent, null);
        }

        public BodyPrintableString(KaitaiStream _io, Asn1Der _parent, Asn1Der _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.str = new String(this._io.readBytesFull(), Charset.forName("ASCII"));
        }
        private String str;
        private Asn1Der _root;
        private Asn1Der _parent;
        public String str() { return str; }
        public Asn1Der _root() { return _root; }
        public Asn1Der _parent() { return _parent; }
    }
    private TypeTag typeTag;
    private LenEncoded len;
    private Object body;
    private Asn1Der _root;
    private KaitaiStruct _parent;
    private byte[] _raw_body;
    public TypeTag typeTag() { return typeTag; }
    public LenEncoded len() { return len; }
    public Object body() { return body; }
    public Asn1Der _root() { return _root; }
    public KaitaiStruct _parent() { return _parent; }
    public byte[] _raw_body() { return _raw_body; }
}