Create an enveloped signature using a RSA key

In this code sample, a XML document ("MyDocument.xml") is loaded and signed with a RSA key.

You can use the sample content provided in XML document (unsigned) for the purpose of testing the code. Copy the content to a file named "MyDocument.xml" in a directory where you test the sample code.

A RSA key ("RSAKey.pem") is used to sign the document. You will need to generate this key. The key can be created with the OpenSSL tool.

openssl genrsa -out RSAKey.pem 2048

The number 2048 is the size of the key in bits.

Copy the file named "RSAKey.pem" to a directory where you test the sample code.

Note: All keys or certificates in PEM or DER format were created with the OpenSSL tool. For information on how the OpenSSL tool works, refer to the OpenSSL documentation.

IMPORT xml

MAIN
  DEFINE doc xml.DomDocument
  DEFINE doc2 xml.DomDocument
  DEFINE root xml.DomNode
  DEFINE node xml.DomNode
  DEFINE signNode xml.DomNode
  DEFINE sig xml.Signature
  DEFINE key xml.CryptoKey
  DEFINE index INTEGER
  # Create DomDocument object
  LET doc = xml.DomDocument.Create()
  # Notice that whitespaces are significant in cryptography, 
  # therefore it is recommended to remove unnecessary ones 
  CALL doc.setFeature("whitespace-in-element-content",FALSE)
  TRY
    # Load document to be signed
    CALL doc.load("MyDocument.xml")
    # Create rsa key
    LET key = xml.CryptoKey.Create("http://www.w3.org/2000/09/xmldsig#rsa-sha1")
    CALL key.loadPEM("RSAKey.pem")
    # Create signature object with the key to use
    LET sig = xml.Signature.Create()
    CALL sig.setKey(key)
    # Set XML node to be signed. In our case, the node with 
    # attribute 'xml:id="code"'
    LET index = sig.createReference("#code",
      "http://www.w3.org/2000/09/xmldsig#sha1")
    # Add enveloped method to not take the XML signature node into account 
    # when computing the entire document.
    CALL sig.appendReferenceTransformation(index,
            "http://www.w3.org/2000/09/xmldsig#enveloped-signature",doc.getDocumentElement())
    # Set canonicalization method on the XML fragment to be signed.
    CALL sig.appendReferenceTransformation(index,
            "http://www.w3.org/2001/10/xml-exc-c14n#")
    # Compute enveloped signature
    CALL sig.compute(doc)
    # Retrieve signature document
    LET doc2=sig.getDocument()
    # Append the signature node to the original document to get 
    # a valid enveloped signature
    # Notice that the enveloped signature can be added anywhere in the 
    # original document
    LET signNode = doc2.getDocumentElement() # Get Signature node
    # Import it into the original document
    LET node = doc.importNode(signNode,true) 
    # Retrieve the original document root node
    LET root = doc.getDocumentElement() 
    # Append the signature node as last child of the original document
    CALL root.appendChild(node) 
    # Save document with enveloped signature back to disk
    CALL doc.setFeature("format-pretty-print",TRUE)
    CALL doc.save("MyDocumentEnvelopedSignature.xml")
  CATCH
    DISPLAY "Unable to create an enveloped signature :",status
  END TRY
END MAIN