(PowerShell) Decrypt a SAML Response

Demonstrates how to decrypt a SAML response.

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

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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:
$http = New-Object Chilkat.Http
$sbSamlResponse = New-Object Chilkat.StringBuilder
$sbPrivateKeyPem = New-Object Chilkat.StringBuilder
$success = $http.QuickGetSb("https://chilkatdownload.com/data/samlresponse.xml",$sbSamlResponse)
if ($success -eq $true) {
    $success = $http.QuickGetSb("https://chilkatdownload.com/data/samlresponse_privkey.pem",$sbPrivateKeyPem)
}

if ($success -ne $true) {
    $($http.LastErrorText)
    exit
}

$xml = New-Object Chilkat.Xml
$xml.LoadSb($sbSamlResponse,$true)

# Load the RSA private key..
$privkey = New-Object Chilkat.PrivateKey
$success = $privkey.LoadPem($sbPrivateKeyPem.GetAsString())
if ($success -ne $true) {
    $($privkey.LastErrorText)
    exit
}

# Prepare an RSA object w/ the private key...
$rsa = New-Object Chilkat.Rsa
$success = $rsa.ImportPrivateKeyObj($privkey)
if ($success -ne $true) {
    $($rsa.LastErrorText)
    exit
}

# 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 -ne $true) {
    $("Encrypted AES key not found.")
    exit
}

$("Encrypted AES key (base64) = " + $encryptedAesKey)

$bdAesKey = New-Object Chilkat.BinData
$bdAesKey.AppendEncoded($encryptedAesKey,"base64")

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

# Note: The DecryptBd method is introduced in Chilkat v9.5.0.76
$success = $rsa.DecryptBd($bdAesKey,$true)
if ($success -ne $true) {
    $($rsa.LastErrorText)
    exit
}

$("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 -ne $true) {
    $("Encrypted data not found.")
    exit
}

$bdEncrypted = New-Object 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.
$crypt = New-Object Chilkat.Crypt2
$sbAlg = New-Object Chilkat.StringBuilder
$sbAlg.Append($xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|xenc:EncryptionMethod|(Algorithm)"))
if ($sbAlg.Contains("aes128-cbc",$true) -eq $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 -ne $true) {
    $($crypt.LastErrorText)
    exit
}

# Get the decrypted XML
$decryptedXml = $bdEncrypted.GetString("utf-8")
$("Decrypted XML:")
$($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>

$xmlAssertion = New-Object Chilkat.Xml
$xmlAssertion.LoadXml($decryptedXml)

# Replace the saml2:EncryptedAssertion XML subtree with the saml2:Assertion 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:
$("Full XML SAML document with decrypted assertion:")
$($xml.GetXml())