public StunMessage AddFingerprint()
{
StunAttribute fingerprint = new StunAttribute();
fingerprint.Type = 0x8028;
byte[] value = new byte[8];
// Type
StuffBuffer(BitConverter.GetBytes((ushort)0x0009), 0, value, 0, 2);
// Length
StuffBuffer(BitConverter.GetBytes(4), 0, value, 2, 2);
// Value
// munge message to remove fingerprint attribute
// CRC32 and ^ with 0x5354554e
// see section 14.7
CRC32 crc = new CRC32();
uint checksum = crc.DoCRC32(buffer);
checksum ^= 0x5354554e;
StuffBuffer(BitConverter.GetBytes(checksum), 0, value, 4, 0);
AppendToBuffer(value);
// return self for fluid style
return(this);
}
public static StunAttribute MappedAddress(IPEndPoint endpoint)
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x0001;
// TODO: need to check endianness of this
byte[] address = endpoint.Address.GetAddressBytes();
attribute.Length = (ushort)(4 + address.Length);
attribute.Value = new byte[attribute.Length];
// set the family based on whether the address is IPv4 or IPv6
if (address.Length == 4)
{
attribute.Value[1] = 1;
}
else
{
attribute.Value[1] = 2;
}
Array.Copy(BitConverter.GetBytes(endpoint.Port), 0, attribute.Value, 2, 2);
Array.Copy(address, 0, attribute.Value, 4, address.Length);
return(attribute);
}
public static StunAttribute Nonce(string nonce)
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x0015;
if (nonce.Length >= 128)
{
throw new InvalidOperationException("Nonce must be fewer than 128 characters");
}
// align length to 32-bit boundary
attribute.Length = (ushort)(nonce.Length + 4);
if (attribute.Length % 4 != 0)
{
attribute.Length = (ushort)(((attribute.Length / 4) + 1) * 4);
}
attribute.Value = new byte[attribute.Length];
byte[] nonceBytes = System.Text.Encoding.UTF8.GetBytes(nonce);
Array.Copy(nonceBytes, 0, attribute.Value, 4, nonceBytes.Length);
// return
return(attribute);
}
public static StunAttribute Username(string username)
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x0006;
// TODO: i'm sure there's some work to do here to comply with OpaqueString profile in RFC8265
byte[] value = System.Text.UTF8Encoding.UTF8.GetBytes(username);
attribute.Length = (ushort)value.Length;
// ensure value is aligned to 32-bit boundary
if (attribute.Length % 4 != 0)
{
attribute.Length = (ushort)(((attribute.Length / 4) + 1) * 4);
}
// allocate
attribute.Value = new byte[attribute.Length];
// copy
Array.Copy(value, attribute.Value, value.Length);
// return
return(attribute);
}
public static StunAttribute MessageIntegritySHA256()
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x001c;
// TODO: work out how to do this based on credential mechanism used
// see section 14.6 of RFC
// return
return(attribute);
}
// TODO: add PASSWORD-ALGORITHMS from section 14.11
// TODO: add enum for MD5 or SHA256 and encode that into the attribute value
public static StunAttribute PasswordAlgorithm()
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x001D;
attribute.Length = 4;
// fixed length - assuming SHA256 and no parameters
attribute.Value = new byte[4];
attribute.Value[1] = 2;
return(attribute);
}
public static StunAttribute MessageIntegrity()
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x0008;
// fixed length because SHA1
attribute.Length = 20;
// TODO: work out how to do this based on credential mechanism used
// see section 14.5 of RFC
// return
return(attribute);
}
public static StunAttribute Userhash(string username, string realm)
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x001e;
// fixed length because SHA256
attribute.Length = 32;
// SHA the "{username}:{realm}"
// TODO: i'm sure there's some work to do here to comply with OpaqueString profile in RFC8265
string combined = $"{username}:{realm}";
attribute.Value = SHA256.Create().ComputeHash(System.Text.Encoding.UTF8.GetBytes(combined));
// return
return(attribute);
}
public static StunAttribute XorMappedAddress(IPEndPoint endpoint, byte[] magicCookie, byte[] transactionId)
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x0020;
// TODO: need to check endianness of this
byte[] address = endpoint.Address.GetAddressBytes();
attribute.Length = (ushort)(4 + address.Length);
attribute.Value = new byte[attribute.Length];
// set the family based on whether the address is IPv4 or IPv6
if (address.Length == 4)
{
attribute.Value[1] = 1;
for (int i = 0; i < 4; i++)
{
address[i] ^= magicCookie[i];
}
}
else
{
attribute.Value[1] = 2;
for (int i = 0; i < 4; i++)
{
address[i] ^= magicCookie[i];
}
for (int i = 4; i < 16; i++)
{
address[i] ^= transactionId[i - 4];
}
}
Array.Copy(BitConverter.GetBytes(endpoint.Port ^ 0x2112), 0, attribute.Value, 2, 2);
Array.Copy(address, 0, attribute.Value, 4, address.Length);
return(attribute);
}
public static StunAttribute ErrorCode(int errorCode, string reason)
{
StunAttribute attribute = new StunAttribute();
attribute.Type = 0x0009;
if (errorCode < 300 || errorCode > 699)
{
throw new InvalidOperationException("Error code must be between 300 and 699");
}
if (reason.Length >= 128)
{
throw new InvalidOperationException("Reason phrase must be fewer than 128 characters");
}
// align length to 32-bit boundary
attribute.Length = (ushort)(reason.Length + 4);
if (attribute.Length % 4 != 0)
{
attribute.Length = (ushort)(((attribute.Length / 4) + 1) * 4);
}
attribute.Value = new byte[attribute.Length];
attribute.Value[0] = 0;
attribute.Value[1] = 0;
attribute.Value[3] = (byte)(errorCode / 100);
attribute.Value[4] = (byte)(errorCode % 100);
byte[] reasonBytes = System.Text.Encoding.UTF8.GetBytes(reason);
Array.Copy(reasonBytes, 0, attribute.Value, 4, reasonBytes.Length);
// return
return(attribute);
}
