/// <summary>
/// Generates a PlayReady Header for the provided key ID.
/// </summary>
public static byte[] GenerateRightsManagementHeader(this HelpersContainerClasses.PlayReady container, Guid keyId)
{
var kidString = Convert.ToBase64String(keyId.ToByteArray());
// Plain text manipulation here to keep things simple. Some common issues include:
// 1) The first element must be EXACTLY as written here. Including small things like order of attributes.
// 2) There must be no extra whitespace anywhere.
var xml = $"<WRMHEADER xmlns=\"http://schemas.microsoft.com/DRM/2007/03/PlayReadyHeader\" version=\"4.0.0.0\"><DATA><PROTECTINFO><KEYLEN>16</KEYLEN><ALGID>AESCTR</ALGID></PROTECTINFO><KID>{kidString}</KID></DATA></WRMHEADER>";
var xmlBytes = Encoding.Unicode.GetBytes(xml);
using (var buffer = new MemoryStream())
{
using (var writer = new BinaryWriter(buffer))
{
// Size (32)
// RecordCount (16)
// RecordType (16)
// RecordLength (16)
// Data (xml)
writer.Write(xmlBytes.Length + 4 + 2 + 2 + 2); // Length.
writer.Write((ushort)1); // Record count.
writer.Write((ushort)1); // Record type (RM header).
writer.Write((ushort)xmlBytes.Length); // Record length.
writer.Write(xmlBytes);
}
return(buffer.ToArray());
}
}
public static Guid GetKeyIdFromRightsManagementHeader(this HelpersContainerClasses.PlayReady container, string rmHeader)
{
Helpers.Argument.ValidateIsNotNullOrWhitespace(rmHeader, nameof(rmHeader));
var document = XDocument.Parse(rmHeader);
var kidElement = document.Root
.Element(XName.Get("DATA", PlayReadyConstants.RightsManagementHeaderNamespace))
?.Element(XName.Get("KID", PlayReadyConstants.RightsManagementHeaderNamespace));
if (kidElement == null)
{
throw new ArgumentException("Rights Management header does not contain the KID element.", nameof(rmHeader));
}
var kidString = kidElement.Value;
return(new Guid(Convert.FromBase64String(kidString)));
}
public static Guid GetKeyIdFromPlayReadyHeader(this HelpersContainerClasses.PlayReady container, byte[] playReadyHeader)
{
Helpers.Argument.ValidateIsNotNullOrEmpty(playReadyHeader, nameof(playReadyHeader));
using (var reader = new BinaryReader(new MemoryStream(playReadyHeader)))
{
var headerLength = reader.ReadUInt32();
if (headerLength != playReadyHeader.Length)
{
throw new ArgumentException("PlayReady header does not have the expected size.");
}
var recordCount = reader.ReadUInt16();
for (int recordIndex = 0; recordIndex < recordCount; recordIndex++)
{
var recordType = reader.ReadUInt16();
var recordLength = reader.ReadUInt16();
// 1 is the Rights Management header.
if (recordType != 1)
{
reader.BaseStream.Position += recordLength;
continue;
}
var rmHeaderBytes = reader.ReadBytesAndVerify(recordLength);
var rmHeader = Encoding.Unicode.GetString(rmHeaderBytes);
return(Helpers.PlayReady.GetKeyIdFromRightsManagementHeader(rmHeader));
}
}
throw new ArgumentException("PlayReady header does not contain a rights management header.");
}
