public static async Task <ServerHelloInfo> PeekServerHello(CustomBufferedStream serverStream)
{
//detects the HTTPS ClientHello message as it is described in the following url:
//https://stackoverflow.com/questions/3897883/how-to-detect-an-incoming-ssl-https-handshake-ssl-wire-format
int recordType = await serverStream.PeekByteAsync(0);
if (recordType == -1)
{
return(null);
}
if ((recordType & 0x80) == 0x80)
{
//SSL 2
// not tested. SSL2 is deprecated
var peekStream = new CustomBufferedPeekStream(serverStream, 1);
// length value + minimum length
if (!await peekStream.EnsureBufferLength(39))
{
return(null);
}
int length = ((recordType & 0x7f) << 8) + peekStream.ReadByte();
if (length < 38)
{
// Message body too short.
return(null);
}
if (peekStream.ReadByte() != 0x04)
{
// should be ServerHello
return(null);
}
int majorVersion = peekStream.ReadByte();
int minorVersion = peekStream.ReadByte();
// 32 bytes random + 1 byte sessionId + 2 bytes cipherSuite
if (!await peekStream.EnsureBufferLength(35))
{
return(null);
}
byte[] random = peekStream.ReadBytes(32);
byte[] sessionId = peekStream.ReadBytes(1);
int cipherSuite = peekStream.ReadInt16();
var serverHelloInfo = new ServerHelloInfo
{
HandshakeVersion = 2,
MajorVersion = majorVersion,
MinorVersion = minorVersion,
Random = random,
SessionId = sessionId,
CipherSuite = cipherSuite,
ServerHelloLength = peekStream.Position,
};
return(serverHelloInfo);
}
else if (recordType == 0x16)
{
var peekStream = new CustomBufferedPeekStream(serverStream, 1);
//should contain at least 43 bytes
// 2 version + 2 length + 1 type + 3 length(?) + 2 version + 32 random + 1 sessionid length
if (!await peekStream.EnsureBufferLength(43))
{
return(null);
}
//SSL 3.0 or TLS 1.0, 1.1 and 1.2
int majorVersion = peekStream.ReadByte();
int minorVersion = peekStream.ReadByte();
int length = peekStream.ReadInt16();
if (peekStream.ReadByte() != 0x02)
{
// should be ServerHello
return(null);
}
length = peekStream.ReadInt24();
majorVersion = peekStream.ReadByte();
minorVersion = peekStream.ReadByte();
byte[] random = peekStream.ReadBytes(32);
length = peekStream.ReadByte();
// sessionid + cipherSuite + compressionMethod
if (!await peekStream.EnsureBufferLength(length + 2 + 1))
{
return(null);
}
byte[] sessionId = peekStream.ReadBytes(length);
int cipherSuite = peekStream.ReadInt16();
byte compressionMethod = peekStream.ReadByte();
int extenstionsStartPosition = peekStream.Position;
var extensions = await ReadExtensions(majorVersion, minorVersion, peekStream);
//var rawBytes = new CustomBufferedPeekStream(serverStream).ReadBytes(peekStream.Position);
var serverHelloInfo = new ServerHelloInfo
{
HandshakeVersion = 3,
MajorVersion = majorVersion,
MinorVersion = minorVersion,
Random = random,
SessionId = sessionId,
CipherSuite = cipherSuite,
CompressionMethod = compressionMethod,
ServerHelloLength = peekStream.Position,
EntensionsStartPosition = extenstionsStartPosition,
Extensions = extensions,
};
return(serverHelloInfo);
}
return(null);
}
public static async Task <ClientHelloInfo> PeekClientHello(CustomBufferedStream clientStream)
{
//detects the HTTPS ClientHello message as it is described in the following url:
//https://stackoverflow.com/questions/3897883/how-to-detect-an-incoming-ssl-https-handshake-ssl-wire-format
int recordType = await clientStream.PeekByteAsync(0);
if (recordType == -1)
{
return(null);
}
if ((recordType & 0x80) == 0x80)
{
//SSL 2
var peekStream = new CustomBufferedPeekStream(clientStream, 1);
// length value + minimum length
if (!await peekStream.EnsureBufferLength(10))
{
return(null);
}
int length = ((recordType & 0x7f) << 8) + peekStream.ReadByte();
if (length < 9)
{
// Message body too short.
return(null);
}
if (peekStream.ReadByte() != 0x01)
{
// should be ClientHello
return(null);
}
int majorVersion = peekStream.ReadByte();
int minorVersion = peekStream.ReadByte();
int ciphersCount = peekStream.ReadInt16() / 3;
int sessionIdLength = peekStream.ReadInt16();
int randomLength = peekStream.ReadInt16();
if (!await peekStream.EnsureBufferLength(ciphersCount * 3 + sessionIdLength + randomLength))
{
return(null);
}
int[] ciphers = new int[ciphersCount];
for (int i = 0; i < ciphers.Length; i++)
{
ciphers[i] = (peekStream.ReadByte() << 16) + (peekStream.ReadByte() << 8) + peekStream.ReadByte();
}
byte[] sessionId = peekStream.ReadBytes(sessionIdLength);
byte[] random = peekStream.ReadBytes(randomLength);
var clientHelloInfo = new ClientHelloInfo
{
HandshakeVersion = 2,
MajorVersion = majorVersion,
MinorVersion = minorVersion,
Random = random,
SessionId = sessionId,
Ciphers = ciphers,
ClientHelloLength = peekStream.Position,
};
return(clientHelloInfo);
}
else if (recordType == 0x16)
{
var peekStream = new CustomBufferedPeekStream(clientStream, 1);
//should contain at least 43 bytes
// 2 version + 2 length + 1 type + 3 length(?) + 2 version + 32 random + 1 sessionid length
if (!await peekStream.EnsureBufferLength(43))
{
return(null);
}
//SSL 3.0 or TLS 1.0, 1.1 and 1.2
int majorVersion = peekStream.ReadByte();
int minorVersion = peekStream.ReadByte();
int length = peekStream.ReadInt16();
if (peekStream.ReadByte() != 0x01)
{
// should be ClientHello
return(null);
}
length = peekStream.ReadInt24();
majorVersion = peekStream.ReadByte();
minorVersion = peekStream.ReadByte();
byte[] random = peekStream.ReadBytes(32);
length = peekStream.ReadByte();
// sessionid + 2 ciphersData length
if (!await peekStream.EnsureBufferLength(length + 2))
{
return(null);
}
byte[] sessionId = peekStream.ReadBytes(length);
length = peekStream.ReadInt16();
// ciphersData + compressionData length
if (!await peekStream.EnsureBufferLength(length + 1))
{
return(null);
}
byte[] ciphersData = peekStream.ReadBytes(length);
int[] ciphers = new int[ciphersData.Length / 2];
for (int i = 0; i < ciphers.Length; i++)
{
ciphers[i] = (ciphersData[2 * i] << 8) + ciphersData[2 * i + 1];
}
length = peekStream.ReadByte();
if (length < 1)
{
return(null);
}
// compressionData
if (!await peekStream.EnsureBufferLength(length))
{
return(null);
}
byte[] compressionData = peekStream.ReadBytes(length);
int extenstionsStartPosition = peekStream.Position;
var extensions = await ReadExtensions(majorVersion, minorVersion, peekStream);
var clientHelloInfo = new ClientHelloInfo
{
HandshakeVersion = 3,
MajorVersion = majorVersion,
MinorVersion = minorVersion,
Random = random,
SessionId = sessionId,
Ciphers = ciphers,
CompressionData = compressionData,
ClientHelloLength = peekStream.Position,
EntensionsStartPosition = extenstionsStartPosition,
Extensions = extensions,
};
return(clientHelloInfo);
}
return(null);
}
private static async Task <Dictionary <string, SslExtension> > ReadExtensions(int majorVersion, int minorVersion, CustomBufferedPeekStream peekStream)
{
Dictionary <string, SslExtension> extensions = null;
if (majorVersion > 3 || majorVersion == 3 && minorVersion >= 1)
{
if (await peekStream.EnsureBufferLength(2))
{
int extensionsLength = peekStream.ReadInt16();
if (await peekStream.EnsureBufferLength(extensionsLength))
{
extensions = new Dictionary <string, SslExtension>();
int idx = 0;
while (extensionsLength > 3)
{
int id = peekStream.ReadInt16();
int length = peekStream.ReadInt16();
byte[] data = peekStream.ReadBytes(length);
var extension = SslExtensions.GetExtension(id, data, idx++);
extensions[extension.Name] = extension;
extensionsLength -= 4 + length;
}
}
}
}
return(extensions);
}
private static async Task <List <SslExtension> > ReadExtensions(int majorVersion, int minorVersion, CustomBufferedPeekStream peekStream)
{
List <SslExtension> extensions = null;
if (majorVersion > 3 || majorVersion == 3 && minorVersion >= 1)
{
if (await peekStream.EnsureBufferLength(2))
{
int extensionsLength = peekStream.ReadInt16();
if (await peekStream.EnsureBufferLength(extensionsLength))
{
extensions = new List <SslExtension>();
while (extensionsLength > 3)
{
int id = peekStream.ReadInt16();
int length = peekStream.ReadInt16();
byte[] data = peekStream.ReadBytes(length);
extensions.Add(SslExtensions.GetExtension(id, data));
extensionsLength -= 4 + length;
}
}
}
}
return(extensions);
}
