246 lines
8.7 KiB
C#
246 lines
8.7 KiB
C#
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namespace Unosquare.Swan.Networking.Ldap
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{
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using System.IO;
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/// <summary>
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/// This class provides LBER encoding routines for ASN.1 Types. LBER is a
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/// subset of BER as described in the following taken from 5.1 of RFC 2251:
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/// 5.1. Mapping Onto BER-based Transport Services
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/// The protocol elements of Ldap are encoded for exchange using the
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/// Basic Encoding Rules (BER) [11] of ASN.1 [3]. However, due to the
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/// high overhead involved in using certain elements of the BER, the
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/// following additional restrictions are placed on BER-encodings of Ldap
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/// protocol elements:
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/// <li>(1) Only the definite form of length encoding will be used.</li>
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/// <li>(2) OCTET STRING values will be encoded in the primitive form only.</li><li>
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/// (3) If the value of a BOOLEAN type is true, the encoding MUST have
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/// its contents octets set to hex "FF".
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/// </li><li>
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/// (4) If a value of a type is its default value, it MUST be absent.
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/// Only some BOOLEAN and INTEGER types have default values in this
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/// protocol definition.
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/// These restrictions do not apply to ASN.1 types encapsulated inside of
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/// OCTET STRING values, such as attribute values, unless otherwise
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/// noted.
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/// </li>
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/// [3] ITU-T Rec. X.680, "Abstract Syntax Notation One (ASN.1) -
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/// Specification of Basic Notation", 1994.
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/// [11] ITU-T Rec. X.690, "Specification of ASN.1 encoding rules: Basic,
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/// Canonical, and Distinguished Encoding Rules", 1994.
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/// </summary>
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internal static class LberEncoder
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{
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/// <summary>
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/// BER Encode an Asn1Boolean directly into the specified output stream.
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/// </summary>
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/// <param name="b">The Asn1Boolean object to encode.</param>
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/// <param name="stream">The stream.</param>
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public static void Encode(Asn1Boolean b, Stream stream)
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{
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Encode(b.GetIdentifier(), stream);
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stream.WriteByte(0x01);
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stream.WriteByte((byte) (b.BooleanValue() ? 0xff : 0x00));
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}
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/// <summary>
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/// Encode an Asn1Numeric directly into the specified outputstream.
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/// Use a two's complement representation in the fewest number of octets
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/// possible.
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/// Can be used to encode INTEGER and ENUMERATED values.
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/// </summary>
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/// <param name="n">The Asn1Numeric object to encode.</param>
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/// <param name="stream">The stream.</param>
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public static void Encode(Asn1Numeric n, Stream stream)
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{
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var octets = new sbyte[8];
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sbyte len;
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var longValue = n.LongValue();
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long endValue = longValue < 0 ? -1 : 0;
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var endSign = endValue & 0x80;
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for (len = 0; len == 0 || longValue != endValue || (octets[len - 1] & 0x80) != endSign; len++)
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{
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octets[len] = (sbyte)(longValue & 0xFF);
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longValue >>= 8;
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}
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Encode(n.GetIdentifier(), stream);
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stream.WriteByte((byte)len);
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for (var i = len - 1; i >= 0; i--)
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{
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stream.WriteByte((byte) octets[i]);
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}
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}
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/// <summary>
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/// Encode an Asn1OctetString directly into the specified outputstream.
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/// </summary>
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/// <param name="os">The Asn1OctetString object to encode.</param>
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/// <param name="stream">The stream.</param>
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public static void Encode(Asn1OctetString os, Stream stream)
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{
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Encode(os.GetIdentifier(), stream);
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EncodeLength(os.ByteValue().Length, stream);
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var tempSbyteArray = os.ByteValue();
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stream.Write(tempSbyteArray.ToByteArray(), 0, tempSbyteArray.Length);
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}
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public static void Encode(Asn1Object obj, Stream stream)
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{
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switch (obj)
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{
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case Asn1Boolean b:
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Encode(b, stream);
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break;
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case Asn1Numeric n:
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Encode(n, stream);
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break;
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case Asn1Null n:
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Encode(n.GetIdentifier(), stream);
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stream.WriteByte(0x00); // Length (with no Content)
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break;
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case Asn1OctetString n:
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Encode(n, stream);
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break;
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case Asn1Structured n:
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Encode(n, stream);
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break;
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case Asn1Tagged n:
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Encode(n, stream);
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break;
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case Asn1Choice n:
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Encode(n.ChoiceValue, stream);
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break;
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default:
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throw new InvalidDataException();
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}
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}
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/// <summary>
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/// Encode an Asn1Structured into the specified outputstream. This method
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/// can be used to encode SET, SET_OF, SEQUENCE, SEQUENCE_OF.
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/// </summary>
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/// <param name="c">The Asn1Structured object to encode.</param>
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/// <param name="stream">The stream.</param>
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public static void Encode(Asn1Structured c, Stream stream)
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{
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Encode(c.GetIdentifier(), stream);
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var arrayValue = c.ToArray();
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using (var output = new MemoryStream())
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{
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foreach (var obj in arrayValue)
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{
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Encode(obj, output);
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}
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EncodeLength((int) output.Length, stream);
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var tempSbyteArray = output.ToArray();
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stream.Write(tempSbyteArray, 0, tempSbyteArray.Length);
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}
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}
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/// <summary>
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/// Encode an Asn1Tagged directly into the specified outputstream.
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/// </summary>
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/// <param name="t">The Asn1Tagged object to encode.</param>
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/// <param name="stream">The stream.</param>
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public static void Encode(Asn1Tagged t, Stream stream)
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{
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if (!t.Explicit)
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{
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Encode(t.TaggedValue, stream);
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return;
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}
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Encode(t.GetIdentifier(), stream);
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// determine the encoded length of the base type.
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using (var encodedContent = new MemoryStream())
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{
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Encode(t.TaggedValue, encodedContent);
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EncodeLength((int) encodedContent.Length, stream);
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var tempSbyteArray = encodedContent.ToArray().ToSByteArray();
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stream.Write(tempSbyteArray.ToByteArray(), 0, tempSbyteArray.Length);
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}
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}
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/// <summary>
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/// Encode an Asn1Identifier directly into the specified outputstream.
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/// </summary>
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/// <param name="id">The Asn1Identifier object to encode.</param>
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/// <param name="stream">The stream.</param>
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public static void Encode(Asn1Identifier id, Stream stream)
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{
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var c = (int) id.Asn1Class;
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var t = id.Tag;
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var ccf = (sbyte)((c << 6) | (id.Constructed ? 0x20 : 0));
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if (t < 30)
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{
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stream.WriteByte((byte)(ccf | t));
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}
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else
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{
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stream.WriteByte((byte)(ccf | 0x1F));
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EncodeTagInteger(t, stream);
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}
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}
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/// <summary>
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/// Encodes the length.
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/// </summary>
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/// <param name="length">The length.</param>
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/// <param name="stream">The stream.</param>
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private static void EncodeLength(int length, Stream stream)
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{
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if (length < 0x80)
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{
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stream.WriteByte((byte)length);
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}
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else
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{
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var octets = new sbyte[4]; // 4 bytes sufficient for 32 bit int.
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sbyte n;
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for (n = 0; length != 0; n++)
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{
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octets[n] = (sbyte)(length & 0xFF);
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length >>= 8;
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}
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stream.WriteByte((byte)(0x80 | n));
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for (var i = n - 1; i >= 0; i--)
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stream.WriteByte((byte)octets[i]);
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}
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}
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/// <summary>
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/// Encodes the provided tag into the stream.
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/// </summary>
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/// <param name="val">The value.</param>
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/// <param name="stream">The stream.</param>
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private static void EncodeTagInteger(int val, Stream stream)
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{
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var octets = new sbyte[5];
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int n;
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for (n = 0; val != 0; n++)
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{
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octets[n] = (sbyte)(val & 0x7F);
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val = val >> 7;
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}
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for (var i = n - 1; i > 0; i--)
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{
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stream.WriteByte((byte)(octets[i] | 0x80));
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}
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stream.WriteByte((byte)octets[0]);
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}
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}
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}
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