(Go) Decrypt a SAML Response

Demonstrates how to decrypt a SAML response.

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

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    // 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 := chilkat.NewHttp()
    sbSamlResponse := chilkat.NewStringBuilder()
    sbPrivateKeyPem := chilkat.NewStringBuilder()
    success := http.QuickGetSb("https://chilkatdownload.com/data/samlresponse.xml",sbSamlResponse)
    if success == true {
        success = http.QuickGetSb("https://chilkatdownload.com/data/samlresponse_privkey.pem",sbPrivateKeyPem)
    }

    if success != true {
        fmt.Println(http.LastErrorText())
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        return
    }

    xml := chilkat.NewXml()
    xml.LoadSb(sbSamlResponse,true)

    // Load the RSA private key..
    privkey := chilkat.NewPrivateKey()
    success = privkey.LoadPem(*sbPrivateKeyPem.GetAsString())
    if success != true {
        fmt.Println(privkey.LastErrorText())
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        xml.DisposeXml()
        privkey.DisposePrivateKey()
        return
    }

    // Prepare an RSA object w/ the private key...
    rsa := chilkat.NewRsa()
    success = rsa.ImportPrivateKeyObj(privkey)
    if success != true {
        fmt.Println(rsa.LastErrorText())
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        xml.DisposeXml()
        privkey.DisposePrivateKey()
        rsa.DisposeRsa()
        return
    }

    // 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 {
        fmt.Println("Encrypted AES key not found.")
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        xml.DisposeXml()
        privkey.DisposePrivateKey()
        rsa.DisposeRsa()
        return
    }

    fmt.Println("Encrypted AES key (base64) = ", *encryptedAesKey)

    bdAesKey := chilkat.NewBinData()
    bdAesKey.AppendEncoded(*encryptedAesKey,"base64")

    sbRsaAlg := chilkat.NewStringBuilder()
    sbRsaAlg.Append(*xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|ds:KeyInfo|xenc:EncryptedKey|xenc:EncryptionMethod|(Algorithm)"))
    fmt.Println("sbRsaAlg contains: ", *sbRsaAlg.GetAsString())
    if sbRsaAlg.Contains("rsa-oaep",true) == true {
        rsa.SetOaepPadding(true)
    }

    // Note: The DecryptBd method is introduced in Chilkat v9.5.0.76
    success = rsa.DecryptBd(bdAesKey,true)
    if success != true {
        fmt.Println(rsa.LastErrorText())
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        xml.DisposeXml()
        privkey.DisposePrivateKey()
        rsa.DisposeRsa()
        bdAesKey.DisposeBinData()
        sbRsaAlg.DisposeStringBuilder()
        return
    }

    fmt.Println("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 {
        fmt.Println("Encrypted data not found.")
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        xml.DisposeXml()
        privkey.DisposePrivateKey()
        rsa.DisposeRsa()
        bdAesKey.DisposeBinData()
        sbRsaAlg.DisposeStringBuilder()
        return
    }

    bdEncrypted := chilkat.NewBinData()
    bdEncrypted.AppendEncoded(*encrypted64,"base64")

    // Get the symmetric algorithm:  "http://www.w3.org/2001/04/xmlenc#aes128-cbc"
    // and set the symmetric decrypt properties.
    crypt := chilkat.NewCrypt2()
    sbAlg := chilkat.NewStringBuilder()
    sbAlg.Append(*xml.ChilkatPath("saml2:EncryptedAssertion|xenc:EncryptedData|xenc:EncryptionMethod|(Algorithm)"))
    if sbAlg.Contains("aes128-cbc",true) == true {
        crypt.SetCryptAlgorithm("aes")
        crypt.SetKeyLength(128)
        crypt.SetCipherMode("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 {
        fmt.Println(crypt.LastErrorText())
        http.DisposeHttp()
        sbSamlResponse.DisposeStringBuilder()
        sbPrivateKeyPem.DisposeStringBuilder()
        xml.DisposeXml()
        privkey.DisposePrivateKey()
        rsa.DisposeRsa()
        bdAesKey.DisposeBinData()
        sbRsaAlg.DisposeStringBuilder()
        bdEncrypted.DisposeBinData()
        crypt.DisposeCrypt2()
        sbAlg.DisposeStringBuilder()
        return
    }

    // Get the decrypted XML
    decryptedXml := bdEncrypted.GetString("utf-8")
    fmt.Println("Decrypted XML:")
    fmt.Println(*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 := chilkat.NewXml()
    xmlAssertion.LoadXml(*decryptedXml)

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

    // The decrypted XML assertion has now replaced the encrypted XML assertion.
    // Examine the fully decrypted XML document:
    fmt.Println("Full XML SAML document with decrypted assertion:")
    fmt.Println(*xml.GetXml())

    http.DisposeHttp()
    sbSamlResponse.DisposeStringBuilder()
    sbPrivateKeyPem.DisposeStringBuilder()
    xml.DisposeXml()
    privkey.DisposePrivateKey()
    rsa.DisposeRsa()
    bdAesKey.DisposeBinData()
    sbRsaAlg.DisposeStringBuilder()
    bdEncrypted.DisposeBinData()
    crypt.DisposeCrypt2()
    sbAlg.DisposeStringBuilder()
    xmlAssertion.DisposeXml()