/// <summary>
/// ClientHello を待ち受け、ALPN データを取得
/// </summary>
/// <param name="stream"></param>
/// <param name="protocolNames"></param>
/// <returns></returns>
public static bool TryGetClientAlpn(this ReadBufferedNetworkStream stream, out IReadOnlyList <string> protocolNames)
{
// ちゃんと Parse してから処理すれば良いんだけど、ALPN 取りたいだけなので雑……
protocolNames = Array.Empty <string>();
try
{
var recordIndex = 0;
var recordData = new List <byte>();
ClientHello clientHello = null;
while (recordData.Count < (clientHello != null ? clientHello.Length + 4 : int.MaxValue))
{
stream.FillBuffer(recordIndex + 5);
var record = new TlsRecord
{
ContentType = stream[recordIndex++]
};
if (record.ContentType != 0x16)
{
return(false); // not Handshake Record
}
record.MajorVersion = stream[recordIndex++];
record.MinorVersion = stream[recordIndex++];
record.Length = stream.ReadBufferUInt16(recordIndex);
recordIndex += 2;
stream.FillBuffer(recordIndex + record.Length);
recordData.AddRange(stream.ReadBufferBytes(recordIndex, record.Length));
if (clientHello == null && 3 <= recordData.Count)
{
if (recordData[0] != 0x01)
{
return(false); // not Client Hello
}
clientHello = new ClientHello
{
Length = recordData.ToUInt24(1)
};
}
}
clientHello.MajorVersion = recordData[4];
clientHello.MinorVersion = recordData[5];
if (clientHello.MajorVersion != 3 || clientHello.MinorVersion < 1)
{
return(false); // less than TLS 1.0 (SSL 3.1)
}
clientHello.SessionIDLength = recordData[38];
clientHello.CipherSuitesLength = recordData.ToUInt16(39 + clientHello.SessionIDLength);
clientHello.CompressionMethodsLength = recordData[41 + clientHello.SessionIDLength + clientHello.CipherSuitesLength];
var extensionsStartIndex = 43 + clientHello.SessionIDLength + clientHello.CipherSuitesLength;
if (clientHello.Length + 4 <= extensionsStartIndex - 2)
{
return(false); // no Extensions
}
clientHello.ExtensionsLength = recordData.ToUInt16(extensionsStartIndex - 2);
var extensionsIndex = extensionsStartIndex;
while (extensionsIndex < extensionsStartIndex + clientHello.ExtensionsLength)
{
var type = recordData.ToUInt16(extensionsIndex);
extensionsIndex += 2;
var length = recordData.ToUInt16(extensionsIndex);
extensionsIndex += 2;
var data = recordData.Skip(extensionsIndex).Take(length).ToArray();
extensionsIndex += length;
if (type != 16)
{
continue;
}
var names = new List <string>();
var alpnIndex = 2; // ALPN Extension Length 何のためにあるの……
while (alpnIndex < length)
{
var nameLength = data[alpnIndex++];
var nameBytes = new byte[nameLength];
Buffer.BlockCopy(data, alpnIndex, nameBytes, 0, nameLength);
names.Add(Encoding.ASCII.GetString(nameBytes));
alpnIndex += nameLength;
}
protocolNames = names.ToArray();
return(true);
}
}
catch
{
return(false);
}
return(false);
}
/// <summary>
/// 現在のバッファー内容が TLS (SSL 3.0 以降)かどうか。
/// </summary>
/// <param name="stream"></param>
/// <returns></returns>
public static bool IsTls(this ReadBufferedNetworkStream stream)
{
// SSL 2.0 はサポートしない
return(0 < stream.BufferedLength &&
stream[0] == 0x16);
}