(C# UWP/WinRT) Decrypt a SAML Response

Demonstrates how to decrypt a SAML response.

Note: This example requires Chilkat v9.5.0.76 or greater.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  This example decrypts this SAML response:

//  <?xml version="1.0" encoding="UTF-8" ?>
//  <saml2p:Response Destination="https://deskflow-asp2.com/ubc/ubcdfe.dll/cwlacs" ID="_e4585eaeedbcaf7c24dff7f1ee2499f5" IssueInstant="2018-10-11T17:46:20.727Z" Version="2.0" xmlns:saml2p="urn:oasis:names:tc:SAML:2.0:protocol">
//      <saml2:Issuer xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">https://authentication.stg.id.ubc.ca</saml2:Issuer>
//      <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
//          <ds:SignedInfo>
//              <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
//              <ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"/>
//              <ds:Reference URI="#_e4585eaeedbcaf7c24dff7f1ee2499f5">
//                  <ds:Transforms>
//                      <ds:Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
//                      <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/>
//                  </ds:Transforms>
//                  <ds:DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
//                  <ds:DigestValue>1ui22tqFyYEOoWI19CMwz4n+ynxNjLDGdTeRMdi60EU=</ds:DigestValue>
//              </ds:Reference>
//          </ds:SignedInfo>
//          <ds:SignatureValue>ROg7FXV6vsp8socVhdo76/i7cRHGGKIveAiScKdujZT0QrHVqIvvbZ/RnwvEMJ9H9i/kJFAQA171
//  		Eo2kDjSdvNFQ/YcKaJUwMtAwT05yVatGV42RZKEf7ME+vpcCTR1LWZdrhat1FWCg1MNQwNWB0EL5
//  		fEP2a4jAcSTB8tFbjTAHsv7IWC39E5RVv99mACYXLa7iGZLtORANZxgYu5qQgmH6pUkI6Z1cpmf+
//  		m9mIjKM6LF0EvLfWOBWL6udZ+GsHPOLjVTJg+1S0xb9FQCYDVW1QhbjSS0icKHKTNNbrsaxllVDY
//  		m4q27YQjRh+XxugPgvsZ61Pxlto8Jbg+6jUlMQ==</ds:SignatureValue>
//          <ds:KeyInfo>
//              <ds:X509Data>
//                  <ds:X509Certificate>MIIDTTCCAjWgAwIBAgIVAJccYyIV6wly8XyddumpgnHMJ2JLMA0GCSqGSIb3DQEBCwUAMCcxJTAj
//  			BgNVBAMMHGF1dGhlbnRpY2F0aW9uLnN0Zy5pZC51YmMuY2EwHhcNMTcwMzAxMTk1NDM0WhcNMzcw
//  			...
//  			xUuh6HuHKIwQqHBz7udxbH3Zbb6jXGDJjiDHt1LRJ8xbVisFIcDlIwsGQQi0HeEJfx4P</ds:X509Certificate>
//              </ds:X509Data>
//          </ds:KeyInfo>
//      </ds:Signature>
//      <saml2p:Status>
//          <saml2p:StatusCode Value="urn:oasis:names:tc:SAML:2.0:status:Success"/>
//      </saml2p:Status>
//      <saml2:EncryptedAssertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion">
//          <xenc:EncryptedData Id="_314d80b9cf02d8eda8d686a6ffd626cf" Type="http://www.w3.org/2001/04/xmlenc#Element" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
//              <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes128-cbc" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#"/>
//              <ds:KeyInfo xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
//                  <xenc:EncryptedKey Id="_d7b6da6fb59a627ebb4a96928441ab79" Recipient="https://ubcdfe.deskflow-asp2.com" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
//                      <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
//                          <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" xmlns:ds="http://www.w3.org/2000/09/xmldsig#"/>
//                      </xenc:EncryptionMethod>
//                      <ds:KeyInfo>
//                          <ds:X509Data>
//                              <ds:X509Certificate>MIICuzCCAiQCCQD3bpigRnKMSzANBgkqhkiG9w0BAQsFADCBoTELMAkGA1UEBhMCQ0ExEDAOBgNV
//  				BAgMB09udGFyaW8xEDAOBgNVBAcMB1Rvcm9udG8xJjAkBgNVBAoMHVRhY3RpY2FsIEJ1c2luZXNz
//  				...
//  				kVRcHd1UK3q7G8FoykWjdQz/0EoMTfEZ+Md56mLOe48eMUZV2ONZuL1kDCEKw1UwkaDQI4Pf8pzx
//  				82b9rgw9wBDtvu5eFPlUGEGIBw==</ds:X509Certificate>
//                          </ds:X509Data>
//                      </ds:KeyInfo>
//                      <xenc:CipherData xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
//                          <xenc:CipherValue>BNHfUOpgdPE5BgpN2VIZIDthMAv1rxk91qVnWyCZOG9bmUKChJtTUqMpndot7VJwYuyKFshkAdnT
//  				D79KGdlSA1xHKcVeZXXzDWglqSyYjzhDCsyOhPaI4HelMFgCLwyFz89uEpUpqlvfl8ol3Am/XnzQ
//  				Vp7V7oS76hocjUI51Qs=</xenc:CipherValue>
//                      </xenc:CipherData>
//                  </xenc:EncryptedKey>
//              </ds:KeyInfo>
//              <xenc:CipherData xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
//                  <xenc:CipherValue>R6l7tmbnXrOfBgB8lA3KnwLYsLH5ZO5omQ7Hp5K05atzw2o55xmCXVMYhNneFxMtxUh6raEyHeZX
//  			PTZNgWrvdqc4GYND/R7MhRrJzk9OAq1WyoOXwbtRpwNDwWA4N2IuprPQJbvjVxaw/PesZMZwZqlp
//  			...
//  			zm9zAxahyu8Ooe8M4r3HN2cY0JxxxkZtDiulbnyA+rRtXfBRJtangvFQ4iFAnzM/Yg9hMyW9jcu0
//  			S7FzuRB9ONMxi+nh0IFWgqp+</xenc:CipherValue>
//              </xenc:CipherData>
//          </xenc:EncryptedData>
//      </saml2:EncryptedAssertion>
//  </saml2p:Response>

//  The sample encrypted SAML response and RSA private key are available online:
Chilkat.Http http = new Chilkat.Http();
Chilkat.StringBuilder sbSamlResponse = new Chilkat.StringBuilder();
Chilkat.StringBuilder sbPrivateKeyPem = new Chilkat.StringBuilder();
bool success = await http.QuickGetSbAsync("https://chilkatdownload.com/data/samlresponse.xml",sbSamlResponse);
if (success == true) {
    success = await http.QuickGetSbAsync("https://chilkatdownload.com/data/samlresponse_privkey.pem",sbPrivateKeyPem);
}

if (success != true) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

Chilkat.Xml xml = new Chilkat.Xml();
xml.LoadSb(sbSamlResponse,true);

//  Load the RSA private key..
Chilkat.PrivateKey privkey = new Chilkat.PrivateKey();
success = privkey.LoadPem(sbPrivateKeyPem.GetAsString());
if (success != true) {
    Debug.WriteLine(privkey.LastErrorText);
    return;
}

//  Prepare an RSA object w/ the private key...
Chilkat.Rsa rsa = new Chilkat.Rsa();
success = rsa.ImportPrivateKeyObj(privkey);
if (success != true) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

//  RSA will be used to decrypt the xenc:EncryptedKey
//  The bytes to be decrypted are in xenc:CipherValue (in base64 format)
string encryptedAesKey = xml.GetChildContent("saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:CipherData|xenc:CipherValue");
if (xml.LastMethodSuccess != true) {
    Debug.WriteLine("Encrypted AES key not found.");
    return;
}

Debug.WriteLine("Encrypted AES key (base64) = " + encryptedAesKey);

Chilkat.BinData bdAesKey = new Chilkat.BinData();
bdAesKey.AppendEncoded(encryptedAesKey,"base64");

Chilkat.StringBuilder sbRsaAlg = new Chilkat.StringBuilder();
sbRsaAlg.Append(xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:EncryptionMethod|(Algorithm)"));
Debug.WriteLine("sbRsaAlg contains: " + sbRsaAlg.GetAsString());
if (sbRsaAlg.Contains("rsa-oaep",true) == true) {
    rsa.OaepPadding = true;
}

//  Note: The DecryptBd method is introduced in Chilkat v9.5.0.76
success = rsa.DecryptBd(bdAesKey,true);
if (success != true) {
    Debug.WriteLine(rsa.LastErrorText);
    return;
}

Debug.WriteLine("Decrypted AES key (hex) = " + bdAesKey.GetEncoded("hex"));

//  Get the encrypted XML (in base64) to be decrypted w/ the AES key.
string encrypted64 = xml.GetChildContent("saml2:EncryptedAssertion|xenc:EncryptedData|xenc:CipherData|xenc:CipherValue");
if (xml.LastMethodSuccess != true) {
    Debug.WriteLine("Encrypted data not found.");
    return;
}

Chilkat.BinData bdEncrypted = new Chilkat.BinData();
bdEncrypted.AppendEncoded(encrypted64,"base64");

//  Get the symmetric algorithm:  "http://www.w3.org/2001/04/xmlenc#aes128-cbc"
//  and set the symmetric decrypt properties.
Chilkat.Crypt2 crypt = new Chilkat.Crypt2();
Chilkat.StringBuilder sbAlg = new Chilkat.StringBuilder();
sbAlg.Append(xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|xenc:EncryptionMethod|(Algorithm)"));
if (sbAlg.Contains("aes128-cbc",true) == true) {
    crypt.CryptAlgorithm = "aes";
    crypt.KeyLength = 128;
    crypt.CipherMode = "cbc";
    //  The 1st 16 bytes of the encrypted data are the AES IV.
    crypt.SetEncodedIV(bdEncrypted.GetEncodedChunk(0,16,"hex"),"hex");
    bdEncrypted.RemoveChunk(0,16);
}

//  Other algorithms, key lengths, etc, can be supported by checking for different Algorithm attribute values..

crypt.SetEncodedKey(bdAesKey.GetEncoded("hex"),"hex");

//  AES decrypt...
success = crypt.DecryptBd(bdEncrypted);
if (success != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

//  Get the decrypted XML
string decryptedXml = bdEncrypted.GetString("utf-8");
Debug.WriteLine("Decrypted XML:");
Debug.WriteLine(decryptedXml);

//  The decrypted XML looks like this:

//  <saml2:Assertion xmlns:saml2="urn:oasis:names:tc:SAML:2.0:assertion" ID="_226e565c548db7986d165d7d969b48b4" IssueInstant="2018-10-11T17:46:20.727Z" Version="2.0">
//  ...
//  ...
//  ...
//  </saml2:Assertion>

Chilkat.Xml xmlAssertion = new Chilkat.Xml();
xmlAssertion.LoadXml(decryptedXml);

//  Replace the saml2:EncryptedAssertion XML subtree with the saml2:Assertion XML.
Chilkat.Xml xmlEncryptedAssertion = xml.FindChild("saml2:EncryptedAssertion");
xmlEncryptedAssertion.SwapTree(xmlAssertion);

//  The decrypted XML assertion has now replaced the encrypted XML assertion.
//  Examine the fully decrypted XML document:
Debug.WriteLine("Full XML SAML document with decrypted assertion:");
Debug.WriteLine(xml.GetXml());