(Excel) Decrypt a SAML Response

Demonstrates how to decrypt a SAML response.

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

Download Excel Class Modules Chilkat Excel Class Modules

'  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:
Dim http As Chilkat.Http
Set http = Chilkat.NewHttp
Dim sbSamlResponse As Chilkat.StringBuilder
Set sbSamlResponse = Chilkat.NewStringBuilder
Dim sbPrivateKeyPem As Chilkat.StringBuilder
Set sbPrivateKeyPem = Chilkat.NewStringBuilder

success = http.QuickGetSb("https://chilkatdownload.com/data/samlresponse.xml",sbSamlResponse)
If (success = True) Then
    success = http.QuickGetSb("https://chilkatdownload.com/data/samlresponse_privkey.pem",sbPrivateKeyPem)
End If

If (success <> True) Then
    Debug.Print http.LastErrorText
    Exit Sub
End If

Dim xml As Chilkat.Xml
Set xml = Chilkat.NewXml
success = xml.LoadSb(sbSamlResponse,True)

'  Load the RSA private key..
Dim privkey As Chilkat.PrivateKey
Set privkey = Chilkat.NewPrivateKey
success = privkey.LoadPem(sbPrivateKeyPem.GetAsString())
If (success <> True) Then
    Debug.Print privkey.LastErrorText
    Exit Sub
End If

'  Prepare an RSA object w/ the private key...
Dim rsa As Chilkat.Rsa
Set rsa = Chilkat.NewRsa
success = rsa.ImportPrivateKeyObj(privkey)
If (success <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

'  RSA will be used to decrypt the xenc:EncryptedKey
'  The bytes to be decrypted are in xenc:CipherValue (in base64 format)

encryptedAesKey = xml.GetChildContent("saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:CipherData|xenc:CipherValue")
If (xml.LastMethodSuccess <> True) Then
    Debug.Print "Encrypted AES key not found."
    Exit Sub
End If

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

Dim bdAesKey As Chilkat.BinData
Set bdAesKey = Chilkat.NewBinData
success = bdAesKey.AppendEncoded(encryptedAesKey,"base64")

Dim sbRsaAlg As Chilkat.StringBuilder
Set sbRsaAlg = Chilkat.NewStringBuilder
success = sbRsaAlg.Append(xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:EncryptionMethod|(Algorithm)"))
Debug.Print "sbRsaAlg contains: "; sbRsaAlg.GetAsString()
If (sbRsaAlg.Contains("rsa-oaep",True) = True) Then
    rsa.OaepPadding = True
End If

'  Note: The DecryptBd method is introduced in Chilkat v9.5.0.76
success = rsa.DecryptBd(bdAesKey,True)
If (success <> True) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

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

'  Get the encrypted XML (in base64) to be decrypted w/ the AES key.

encrypted64 = xml.GetChildContent("saml2:EncryptedAssertion|xenc:EncryptedData|xenc:CipherData|xenc:CipherValue")
If (xml.LastMethodSuccess <> True) Then
    Debug.Print "Encrypted data not found."
    Exit Sub
End If

Dim bdEncrypted As Chilkat.BinData
Set bdEncrypted = Chilkat.NewBinData
success = bdEncrypted.AppendEncoded(encrypted64,"base64")

'  Get the symmetric algorithm:  "http://www.w3.org/2001/04/xmlenc#aes128-cbc"
'  and set the symmetric decrypt properties.
Dim crypt As Chilkat.Crypt2
Set crypt = Chilkat.NewCrypt2
Dim sbAlg As Chilkat.StringBuilder
Set sbAlg = Chilkat.NewStringBuilder
success = sbAlg.Append(xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|xenc:EncryptionMethod|(Algorithm)"))
If (sbAlg.Contains("aes128-cbc",True) = True) Then
    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"
    success = bdEncrypted.RemoveChunk(0,16)
End If

'  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) Then
    Debug.Print crypt.LastErrorText
    Exit Sub
End If

'  Get the decrypted XML

decryptedXml = bdEncrypted.GetString("utf-8")
Debug.Print "Decrypted XML:"
Debug.Print 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>

Dim xmlAssertion As Chilkat.Xml
Set xmlAssertion = Chilkat.NewXml
success = xmlAssertion.LoadXml(decryptedXml)

'  Replace the saml2:EncryptedAssertion XML subtree with the saml2:Assertion XML.

Set xmlEncryptedAssertion = xml.FindChild("saml2:EncryptedAssertion")
success = xmlEncryptedAssertion.SwapTree(xmlAssertion)

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