// This method determines the security token that contains the key material that
// the STS should encrypt a session key with in order
// for the service the issued token is intended for to be able to extract that session key
private static SecurityToken DetermineEncryptingToken(RequestSecurityToken rst)
{
// If rst is null, we're toast
if (rst == null)
throw new ArgumentNullException("rst");
// Figure out service URI
Uri uri = DetermineEndpointUri(rst);
string encryptingTokenSubjectName = (uri == null) ? "localhost" : uri.DnsSafeHost;
return GetToken(encryptingTokenSubjectName, StoreName.TrustedPeople, StoreLocation.LocalMachine);
}
private static byte[] GetSessionKey(RequestSecurityToken rst, RequestSecurityTokenResponse rstr)
{
// If rst is null, we're toast
if (rst == null)
throw new ArgumentNullException("rst");
// If rstr is null, we're toast
if (rstr == null)
throw new ArgumentNullException("rstr");
// Figure out the keySize
int keySize = 256;
if (rst.KeySize != 0)
keySize = rst.KeySize;
Console.WriteLine("Proof key size {0}", keySize);
// Figure out whether we're using Combined or Issuer entropy.
byte[] sessionKey = null;
byte[] senderEntropy = GetSenderEntropy(rst);
byte[] issuerEntropy = GetIssuerEntropy(keySize);
if (senderEntropy != null)
{
// Combined entropy
Console.WriteLine("Combined Entropy");
sessionKey = RequestSecurityTokenResponse.ComputeCombinedKey(senderEntropy, issuerEntropy, keySize);
rstr.IssuerEntropy = new BinarySecretSecurityToken ( issuerEntropy );
rstr.ComputeKey = true;
}
else
{
// Issuer-only entropy
Console.WriteLine("Issuer-only entropy");
sessionKey = issuerEntropy;
rstr.RequestedProofToken = new BinarySecretSecurityToken(sessionKey);
}
rstr.KeySize = keySize;
return sessionKey;
}
// The RST message can contain a wsp:AppliesTo which can be used to indicate the service that
// the issued token is intended for. This method extracts the URI for that service, if any such
// Uri is present in the RST. Otherwise it returns null.
private static Uri DetermineEndpointUri(RequestSecurityToken rst)
{
// If rst is null, we're toast
if (rst == null)
throw new ArgumentNullException("rst");
EndpointAddress epr = rst.AppliesTo;
// If AppliesTo is missing or doesn't contain a 2004/08 or
// 2005/10 EPR then the epr local variable will be null in which case we return null.
// Otherwise we return the Uri portion of the EPR.
return epr == null ? null : epr.Uri;
}
private static byte[] GetSenderEntropy(RequestSecurityToken rst)
{
// If rst is null, we're toast
if (rst == null)
throw new ArgumentNullException("rst");
SecurityToken senderEntropyToken = rst.RequestorEntropy;
byte[] senderEntropy = null;
if (senderEntropyToken != null)
{
BinarySecretSecurityToken bsst = senderEntropyToken as BinarySecretSecurityToken;
if (bsst != null)
senderEntropy = bsst.GetKeyBytes();
}
return senderEntropy;
}
private RequestSecurityTokenResponse Issue(RequestSecurityToken rst)
{
// If rst is null, we're toast
if (rst == null)
throw new ArgumentNullException("rst");
// Create an RSTR object
RequestSecurityTokenResponse rstr = new RequestSecurityTokenResponse();
string tokenType = rst.TokenType;
Console.WriteLine("Issue: Request for token type {0}", tokenType);
if (tokenType != null && tokenType != "http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV1.1")
{
throw new NotSupportedException("Unsupported token type " + tokenType);
}
SecurityKey signingKey = issuerToken.SecurityKeys[0];
SecurityKeyIdentifier signingKeyIdentifier = new SecurityKeyIdentifier(issuerToken.CreateKeyIdentifierClause<X509ThumbprintKeyIdentifierClause>());
SecurityKeyIdentifier proofKeyIdentifier = null;
if (rst.IsProofKeyAsymmetric())
{
throw new NotSupportedException("Public key issuance is not supported");
}
// Symmetric proof key
Console.WriteLine("Constructing Symmetric Proof Key");
// Construct session key. This is the symmetric key that the client and the service will share.
// It actually appears twice in the response message; once for the service and
// once for the client. In the former case, it is typically embedded in the issued token,
// in the latter case, it is returned in a wst:RequestedProofToken element.
byte[] sessionKey = GetSessionKey(rst, rstr);
// Get token to use when encrypting key material for the service
SecurityToken encryptingToken = DetermineEncryptingToken(rst);
// Encrypt the session key for the service
GetEncryptedKey(encryptingToken, sessionKey, out proofKeyIdentifier);
// Issued tokens are valid for 12 hours by default
DateTime effectiveTime = DateTime.Now;
DateTime expirationTime = DateTime.Now + new TimeSpan(12, 0, 0);
SecurityToken samlToken = CreateSAMLToken(effectiveTime, expirationTime, signingKey, signingKeyIdentifier, proofKeyIdentifier);
rstr.RequestedSecurityToken = samlToken;
rstr.Context = rst.Context;
rstr.TokenType = tokenType;
SecurityKeyIdentifierClause samlReference = samlToken.CreateKeyIdentifierClause<SamlAssertionKeyIdentifierClause>();
rstr.RequestedAttachedReference = samlReference;
rstr.RequestedUnattachedReference = samlReference;
return rstr;
}
