(Swift 2) Create XML Digital Signature using a ECDSA Key

Demonstrates how to create an XML digital signature using a ECDSA key.

This example requires Chilkat v9.5.0.69 or greater.

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

    // The SOAP XML to be signed in this example contains the following:

    // <?xml version="1.0" encoding="UTF-8" standalone="no" ?>
    // <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
    //     <SOAP-ENV:Header>
    //         <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" SOAP-ENV:mustUnderstand="1"></wsse:Security>
    //     </SOAP-ENV:Header>
    //     <SOAP-ENV:Body xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12" SOAP-SEC:id="Body">
    //         <z:FooBar xmlns:z="http://example.com" />
    //     </SOAP-ENV:Body>
    // </SOAP-ENV:Envelope>
    // 

    // The above XML is available at https://www.chilkatsoft.com/exampleData/soapToSign.xml
    // Fetch the XML and then sign it..

    var url: String? = "https://www.chilkatsoft.com/exampleData/soapToSign.xml"
    let http = CkoHttp()
    let sbSoapXml = CkoStringBuilder()
    var success: Bool = http.QuickGetSb(url, sbContent: sbSoapXml)
    if success != true {
        print("\(http.LastErrorText)")
        return
    }

    // This example uses an ECDSA private key for signing.  
    // There are many ways to load an ECDSA private key using Chilkat.  This example
    // will load from an unencrypted PEM file.

    // For your convenience, Chilkat put this sample ECDSA PEM here:  https://www.chilkatsoft.com/exampleData/secp256r1-key.zip
    let ecKey = CkoPrivateKey()
    success = ecKey.LoadPemFile("qa_data/ecc/secp256r1-key.pem")
    if success != true {
        print("\(ecKey.LastErrorText)")
        return
    }

    // To create the XML digital signature (i.e. embed the signature within
    // the SOAP XML), we specify what is desired, and then call the method to 
    // create the XML signature.
    // 
    // For example, the application must provide the following:
    //     - Where to put the signature.
    //     - What to sign.
    //     - The algorithms to be used.
    //     - The key to be used for signing.
    // 

    let xmlSigGen = CkoXmlDSigGen()

    // In this example, the Signature will be placed within the wsse:Security element.
    // To specify the location, set the SigLocation property to the XML path to this element,
    // using vertical bar characters to separate tags.
    xmlSigGen.SigLocation = "SOAP-ENV:Envelope|SOAP-ENV:Header|wsse:Security"

    // An XML digital signature contains one or more references.  A given reference
    // can be a same-document reference (to an XML fragment), or an external reference.
    // This example will add a single same-document reference.  We'll add a reference to the XML fragment
    // at SOAP-ENV:Body, which is indicated by providing the value of the "Id" attribute (where "Id" is case
    // insensitive).  For each same-document reference, we must also indicate the hash algorithm and XML canonicalization
    // algorithm to be used.  For this example we'll choose SHA-256 and Exclusive XML Canonicalization.
    xmlSigGen.AddSameDocRef("Body", digestMethod: "sha256", canonMethod: "EXCL_C14N", prefixList: "", refType: "")

    // Let's provide the ECDSA key to be used for signing:
    xmlSigGen.SetPrivateKey(ecKey)

    // We're leaving the following properties at their default values:
    // 
    //    - SigNamespacePrefix (default is "ds")
    //    - SignedInfoCanonAlg  (default is EXCL_C14N)
    //    - SignedInfoDigestMethod (default is sha256)
    //    - KeyInfoType (default is "KeyValue", where the ECDSA public key is included in the Signature)

    // Note: Each Reference specifies its own algorithms for XML canonicalization and hashing.
    // The SignedInfo part also has specified hash and canonicalization algorithms, which may be different
    // than the algorithms used in the References.
    // In this example, we use Exclusive XML Canonicalization and SHA-256 throughout.

    // Finally, we're going to set one property that's optional, but commonly used.
    // It's the SignedInfoPrefixList.  In this case, we're using Exclusive Canonicalization, and the signature
    // will be placed in a location within the XML document where namespace prefixes are used in the ancestors.
    // Specifically, the "wsse" and "SOAP-ENV" namespace prefixes are used.
    xmlSigGen.SignedInfoPrefixList = "wsse SOAP-ENV"

    // OK, everything's specified, so let's create the XML digital signature:
    // This in-place signs the XML.  If successful, sbSoapXml will contain the 
    // XML with the digital signature at the specified location.
    success = xmlSigGen.CreateXmlDSigSb(sbSoapXml)
    if success != true {
        print("\(xmlSigGen.LastErrorText)")
        return
    }

    // Examine the signed SOAP XML:
    print("\(sbSoapXml.GetAsString())")

    // This is the signed SOAP XML.
    // Chilkat emits the Signature in compact form on a single line.  Whitespace in XML signatures
    // matters.  Chilkat's opinion is that writing the Signature without whitespace minimizes the chance
    // for problems with whatever software might be verifying the signature.

    // <?xml version="1.0" encoding="UTF-8" standalone="no" ?>
    // <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
    //     <SOAP-ENV:Header>
    //         <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" SOAP-ENV:mustUnderstand="1"><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#"><InclusiveNamespaces xmlns="http://www.w3.org/2001/10/xml-exc-c14n#" PrefixList="wsse SOAP-ENV"/></ds:CanonicalizationMethod><ds:SignatureMethod Algorithm="http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256"/><ds:Reference URI="#Body"><ds:Transforms><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>OwgHPZNfDkXnZsjpfzXqAcT3RV3HzmTsEy2bP44FJ0M=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>jmPSGgtirHSjjcs/o0NIDwwvy4aFBCEosSN+XP5NLVuGpRYnS2EM7mItiw6TKmESAoJYV23ZN4pZ9BFRKSvZqw==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:ECKeyValue xmlns="http://www.w3.org/2009/xmldsig11#"><ds:NamedCurve URI="urn:oid:1.2.840.10045.3.1.7" /><ds:PublicKey>BOVKaiLPKEDChhkA64UEBOXTv/VFHnhrUPN+bXqCvEl7rroAYpH5tKzbiGTtMSlp4JO9Pxg44zeX7EoWDvOrpD0=</ds:PublicKey></ds:ECKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></wsse:Security>
    //     </SOAP-ENV:Header>
    //     <SOAP-ENV:Body xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12" SOAP-SEC:id="Body">
    //         <z:FooBar xmlns:z="http://example.com" />
    //     </SOAP-ENV:Body>
    // </SOAP-ENV:Envelope>

    // The above signed XML contains the ECDSA public key in the ECKeyValue fragment (within the ds:KeyInfo).
    // The signature can easily be verified like this:

    let verifier = CkoXmlDSig()

    // First load the XML containing the signature(s) to be verified.
    success = verifier.LoadSignatureSb(sbSoapXml)
    if success != true {
        print("\(verifier.LastErrorText)")
        return
    }

    var bVerified: Bool = verifier.VerifySignature(true)
    if bVerified != true {
        print("\(verifier.LastErrorText)")
    }

    print("Signature verified = \(bVerified)")

}