(PureBasic) Create XML Digital Signature using a DSA Key

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

This example requires Chilkat v9.5.0.69 or greater.

Chilkat PureBasic Module Download

Chilkat PureBasic Module

IncludeFile "CkXmlDSigGen.pb"
IncludeFile "CkHttp.pb"
IncludeFile "CkStringBuilder.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkXmlDSig.pb"

Procedure ChilkatExample()

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

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

    ; <?xml version="1.0" encoding="UTF-8" standalone="no"?>
    ; <Envelope>
    ;   <Header>
    ;     <Security>
    ;     </Security>
    ;   </Header>
    ;   <Body Id="abc">
    ;     <z:FooBar xmlns:z="https://www.example-code.com"/>
    ;   </Body>
    ; </Envelope>

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

    url.s = "https://www.chilkatsoft.com/exampleData/xmlToSign.xml"
    http.i = CkHttp::ckCreate()
    If http.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    sbXml.i = CkStringBuilder::ckCreate()
    If sbXml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success.i = CkHttp::ckQuickGetSb(http,url,sbXml)
    If success <> 1
        Debug CkHttp::ckLastErrorText(http)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        ProcedureReturn
    EndIf

    ; This example uses a DSA private key for signing.  
    ; There are many ways of getting an DSA private key using Chilkat.  This example
    ; will load it from an encrypted PEM file.

    ; In case you would like to use it, I put the DSA private key PEM file here:
    ; https://www.chilkatsoft.com/exampleData/dsa1024_secret.zip
    ; The password is "secret".
    dsaKey.i = CkPrivateKey::ckCreate()
    If dsaKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkPrivateKey::ckLoadEncryptedPemFile(dsaKey,"qa_data/dsa/dsa1024_secret.pem","secret")
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(dsaKey)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        CkPrivateKey::ckDispose(dsaKey)
        ProcedureReturn
    EndIf

    ; To create the XML digital signature (i.e. embed the signature within
    ; the XML), first specify what is desired, 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.
    ; 

    xmlSigGen.i = CkXmlDSigGen::ckCreate()
    If xmlSigGen.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; In this example, we're going to put the signature within the Security element.
    ; To specify the location, set the SigLocation property to the XML path to this element,
    ; using vertical bar characters to separate tags.
    CkXmlDSigGen::setCkSigLocation(xmlSigGen, "Envelope|Header|Security")

    ; An XML digital signature contains one or more references.  These can be references to the parts
    ; of the XML document to be signed (a same document reference), or can be external references.
    ; This example will add a single same-document reference.  We'll add a reference to the XML fragment
    ; at Body, which is indicated by providing the value of the "ID" attribute (where "ID" is case
    ; insensitive).  In this case, we specify "abc" because Body has an Id="abc".
    ; This causes the <Body> ... </Body> XML fragment to be signed.
    ; 
    ; 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 SHA1 and Exclusive XML Canonicalization.
    CkXmlDSigGen::ckAddSameDocRef(xmlSigGen,"abc","sha1","EXCL_C14N","","")

    ; Provide the DSA key to be used for signing:
    CkXmlDSigGen::ckSetPrivateKey(xmlSigGen,dsaKey)

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

    ; Note: Each Reference has it's own specified algorithms for XML canonicalization and hashing,
    ; and the actual signature part (the SignedInfo) has it's own hash/canonicalization algorithm.
    ; They may or may not be the same.  In this example, we use Exclusive XML Canonicalization and SHA1 throughout.

    ; The default SignedInfoDigestMethod is sha256, which is a good choice.  This example will
    ; change it to sha1.
    CkXmlDSigGen::setCkSignedInfoDigestMethod(xmlSigGen, "sha1")

    ; OK, everything's specified, so let's create the XML digital signature:
    ; This in-place signs the XML.  If successful, sbXml will contain the 
    ; XML with the digital signature at the specified location.
    success = CkXmlDSigGen::ckCreateXmlDSigSb(xmlSigGen,sbXml)
    If success <> 1
        Debug CkXmlDSigGen::ckLastErrorText(xmlSigGen)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        CkPrivateKey::ckDispose(dsaKey)
        CkXmlDSigGen::ckDispose(xmlSigGen)
        ProcedureReturn
    EndIf

    ; Examine the signed XML:
    Debug CkStringBuilder::ckGetAsString(sbXml)

    ; Below is the signed XML that is produced.
    ; 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"?>
    ; <Envelope>
    ;   <Header>
    ;     <Security>
    ;     <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/2000/09/xmldsig#dsa-sha1"/><ds:Reference URI="#abc"><ds:Transforms><ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"/></ds:Transforms><ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/><ds:DigestValue>77X3L6odxTBow1W1dIiqZW1foow=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>Ci/KiAqoQLvNyK94n8TJwdJ6dVpIIy8tJg+9s8utmB92cW8lTd+U7g==</ds:SignatureValue><ds:KeyInfo><ds:KeyValue><ds:DSAKeyValue><ds:P>AN+Af9FvnqYl84Own8m/MHza9vVFEbpySOiWyeIM8diDjaES9i+UykaX9BGc0oaRJHtrHhe+gboMBGHfP+gYcgbqzeyVCi2kHghRD/TK7uI4jN8Yv8tfM6AO0QrDFfxFq4IV+qTZbSoCkbWaopQ+kEOY6B4btFxJ1YuE48mExMZ3</ds:P><ds:Q>AOCv5pwf4kvMW37Yzt0iH6URKOlD</ds:Q><ds:G>FO3eoDcpuU9Z25OQGFtC+M2ifczcKyRkFwTauGR3mIw0wePPiu3Ocr7A81SA8GQ9x3hWO5jyP//jL3jxYy8fgBg2RXwiic3nwT2rZfu50g6tPUpz1stKz/+Mxjulo6XuaMSOWwjU021IxVMzxQ1/L8QiwiIrwxvfQOaMY8HJgvw=</ds:G><ds:Y>JJmZQvWtrZ+Nb2YV47SfGAave8uOIedGlmg+CseoqKZC2aFcWM6kR0giUwQx834dhxQScRhqzxFxQPk/x+5hyG8LQbXW+BELmT1BiyodobYUAet4rSIt4EU4KU0iYw1drpcWT1jqI07l5xNi28heYSfSF5Odv2qwXxVKDSEeEkM=</ds:Y></ds:DSAKeyValue></ds:KeyValue></ds:KeyInfo></ds:Signature></Security>
    ;   </Header>
    ;   <Body Id="abc">
    ;     <z:FooBar xmlns:z="https://www.example-code.com"/>
    ;   </Body>
    ; </Envelope>

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

    verifier.i = CkXmlDSig::ckCreate()
    If verifier.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; First load the XML containing the signature(s) to be verified.
    success = CkXmlDSig::ckLoadSignatureSb(verifier,sbXml)
    If success <> 1
        Debug CkXmlDSig::ckLastErrorText(verifier)
        CkHttp::ckDispose(http)
        CkStringBuilder::ckDispose(sbXml)
        CkPrivateKey::ckDispose(dsaKey)
        CkXmlDSigGen::ckDispose(xmlSigGen)
        CkXmlDSig::ckDispose(verifier)
        ProcedureReturn
    EndIf

    bVerified.i = CkXmlDSig::ckVerifySignature(verifier,1)
    If bVerified <> 1
        Debug CkXmlDSig::ckLastErrorText(verifier)
    EndIf

    Debug "Signature verified = " + Str(bVerified)


    CkHttp::ckDispose(http)
    CkStringBuilder::ckDispose(sbXml)
    CkPrivateKey::ckDispose(dsaKey)
    CkXmlDSigGen::ckDispose(xmlSigGen)
    CkXmlDSig::ckDispose(verifier)


    ProcedureReturn
EndProcedure