using System.Security.Cryptography;
using System.Text;
namespace NewLife.Security;
/// <summary>抽象语法标记。ASN.1是一种 ISO/ITU-T 标准，描述了一种对数据进行表示、编码、传输和解码的数据格式。</summary>
public class Asn1
{
#region 属性
/// <summary>标签</summary>
public Asn1Tags Tag { get; set; }
/// <summary>长度</summary>
public Int32 Length { get; set; }
/// <summary>数值</summary>
public Object? Value { get; set; }
#endregion
#region 构造
/// <summary>已重载。</summary>
/// <returns></returns>
public override String ToString()
{
switch (Tag)
{
case Asn1Tags.Boolean:
break;
case Asn1Tags.Integer: return "#" + (Value as Byte[]).ToHex(0, 32);
case Asn1Tags.BitString:
case Asn1Tags.OctetString: return (Value as Byte[]).ToHex(0, 32);
case Asn1Tags.Null: return "Null";
case Asn1Tags.ObjectIdentifier:
if (Value is Oid oid) return oid.FriendlyName + " " + oid.Value;
break;
case Asn1Tags.Sequence:
if (Value is Asn1[] arr) return arr.Join();
break;
}
return $"{Tag} {Value}";
}
#endregion
#region 方法
/// <summary>获取OID</summary>
/// <returns></returns>
public Oid[] GetOids()
{
if (Value is Oid oid) return [oid];
var list = new List<Oid>();
if (Value is Asn1[] arr)
{
foreach (var item in arr)
{
var ds = item.GetOids();
if (ds != null && ds.Length > 0) list.AddRange(ds);
}
}
return list.ToArray();
}
#endregion
#region 读取
/// <summary>读取</summary>
/// <param name="data"></param>
/// <returns></returns>
public static Asn1? Read(Byte[] data) => Read(new BinaryReader(new MemoryStream(data)));
/// <summary>读取</summary>
/// <param name="stream"></param>
/// <returns></returns>
public static Asn1? Read(Stream stream) => Read(new BinaryReader(stream));
/// <summary>读取对象</summary>
/// <param name="reader"></param>
/// <returns></returns>
public static Asn1? Read(BinaryReader reader)
{
var len = ReadTLV(reader, out var tag);
if (len < 0) return null;
var asn = new Asn1 { Length = len };
var tagNo = tag & 0x1F;
//if (tagNo == 0x1F) tagNo = reader.BaseStream.ReadEncodedInt();
// isConstructed
asn.Tag = (Asn1Tags)tagNo;
if ((tag & (Byte)Asn1Tags.Constructed) != 0)
{
switch (asn.Tag)
{
case Asn1Tags.OctetString:
break;
case Asn1Tags.External:
break;
case Asn1Tags.Sequence:
var reader2 = new BinaryReader(new MemoryStream(reader.ReadBytes(len)));
var list = new List<Asn1>();
while (true)
{
var obj = Read(reader2);
if (obj == null) break;
list.Add(obj);
}
asn.Value = list.ToArray();
return asn;
case Asn1Tags.Set:
break;
}
}
// 基础类型
var buf = reader.ReadBytes(len);
asn.Value = buf;
switch (asn.Tag)
{
case Asn1Tags.Boolean:
break;
case Asn1Tags.Integer:
asn.Value = buf;
break;
case Asn1Tags.BitString:
if (buf.Length > 0 && buf[0] == 0) buf = buf.ReadBytes(1, buf.Length - 1);
asn.Value = buf;
break;
case Asn1Tags.OctetString:
asn.Value = buf;
break;
case Asn1Tags.Null:
break;
case Asn1Tags.ObjectIdentifier:
//asn.Value = reader.ReadBytes(len);
asn.Value = new Oid(MakeOidStringFromBytes(buf));
break;
case Asn1Tags.External:
break;
case Asn1Tags.Enumerated:
break;
//case Asn1Tags.Sequence:
// break;
//case Asn1Tags.SequenceOf:
// break;
case Asn1Tags.Set:
break;
//case Asn1Tags.SetOf:
// break;
case Asn1Tags.NumericString:
break;
case Asn1Tags.PrintableString:
break;
case Asn1Tags.T61String:
break;
case Asn1Tags.VideotexString:
break;
case Asn1Tags.IA5String:
break;
case Asn1Tags.UtcTime:
break;
case Asn1Tags.GeneralizedTime:
break;
case Asn1Tags.GraphicString:
break;
case Asn1Tags.VisibleString:
break;
case Asn1Tags.GeneralString:
break;
case Asn1Tags.UniversalString:
break;
case Asn1Tags.BmpString:
break;
case Asn1Tags.Utf8String:
break;
case Asn1Tags.Constructed:
break;
case Asn1Tags.Application:
break;
case Asn1Tags.Tagged:
break;
default:
break;
}
return asn;
}
/// <summary>获取字节数组</summary>
/// <param name="trimZero"></param>
/// <returns></returns>
public Byte[]? GetByteArray(Boolean trimZero = false)
{
var buf = Value as Byte[];
if (buf != null && trimZero && buf[0] == 0) buf = buf.ReadBytes(1, buf.Length - 1);
return buf;
}
#endregion
#region 辅助
/// <summary>读取TLV，Tag+Length+Value</summary>
/// <param name="reader">读取器</param>
/// <param name="tag"></param>
/// <returns>返回长度，数据流指针移到Value第一个字节</returns>
private static Int32 ReadTLV(BinaryReader reader, out Byte tag)
{
tag = 0;
var v = reader.BaseStream.ReadByte();
if (v < 0) return v;
tag = (Byte)v;
var len = (Int32)reader.ReadByte();
if (len == 0x81)
len = reader.ReadByte();
else if (len == 0x82)
len = reader.ReadBytes(2).ToUInt16(0, false);
else if (len == 0x84)
len = (Int32)reader.ReadBytes(4).ToUInt32(0, false);
return len;
}
/// <summary>读取TLV，Tag+Length+Value</summary>
/// <param name="reader">读取器</param>
/// <param name="trimZero">是否剔除头部的0x00</param>
/// <returns></returns>
private static Byte[] ReadTLV(BinaryReader reader, Boolean trimZero = true)
{
var len = ReadTLV(reader, out _);
//Debug.Assert(tag == 0x02);
//if (offset > 0) reader.BaseStream.Seek(1, SeekOrigin.Current);
if (trimZero && reader.PeekChar() == 0) { reader.ReadByte(); len--; }
return reader.ReadBytes(len);
}
private const Int64 LONG_LIMIT = (Int64.MaxValue >> 7) - 0x7f;
private static String MakeOidStringFromBytes(Byte[] bytes)
{
var objId = new StringBuilder();
Int64 value = 0;
//BigInteger bigValue;
var first = true;
for (var i = 0; i != bytes.Length; i++)
{
Int32 b = bytes[i];
if (value <= LONG_LIMIT)
{
value += (b & 0x7f);
if ((b & 0x80) == 0) // end of number reached
{
if (first)
{
if (value < 40)
{
objId.Append('0');
}
else if (value < 80)
{
objId.Append('1');
value -= 40;
}
else
{
objId.Append('2');
value -= 80;
}
first = false;
}
objId.Append('.');
objId.Append(value);
value = 0;
}
else
{
value <<= 7;
}
}
//else
//{
// if (bigValue == null)
// {
// bigValue = BigInteger.ValueOf(value);
// }
// bigValue = bigValue.Or(BigInteger.ValueOf(b & 0x7f));
// if ((b & 0x80) == 0)
// {
// if (first)
// {
// objId.Append('2');
// bigValue = bigValue.Subtract(BigInteger.ValueOf(80));
// first = false;
// }
// objId.Append('.');
// objId.Append(bigValue);
// bigValue = null;
// value = 0;
// }
// else
// {
// bigValue = bigValue.ShiftLeft(7);
// }
//}
}
return objId.ToString();
}
#endregion
}
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