PHP

Create XML Digital Signature using a DSA Key

See more XML Digital Signatures Examples

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

This example requires Chilkat v9.5.0.69 or greater.

Chilkat2 PHP

<?php

use Chilkat2\Http;
use Chilkat2\PrivateKey;
use Chilkat2\StringBuilder;
use Chilkat2\XmlDSig;
use Chilkat2\XmlDSigGen;

// 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 = 'https://www.chilkatsoft.com/exampleData/xmlToSign.xml';
$http = new Http();
$sbXml = new StringBuilder();
try {
    $http->QuickGetSb($url, $sbXml);

    // 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 = new PrivateKey();
    $dsaKey->LoadEncryptedPemFile('qa_data/dsa/dsa1024_secret.pem', 'secret');

    // 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 = new XmlDSigGen();

    // 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.
    $xmlSigGen->SigLocation = '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.
    $xmlSigGen->AddSameDocRef('abc', 'sha1', 'EXCL_C14N', '', '');

    // Provide the DSA key to be used for signing:
    $xmlSigGen->SetPrivateKey($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.
    $xmlSigGen->SignedInfoDigestMethod = '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.
    $xmlSigGen->CreateXmlDSigSb($sbXml);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Examine the signed XML:
echo $sbXml->GetAsString(), "\n";

// 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 = new XmlDSig();

// First load the XML containing the signature(s) to be verified.
try {
    $verifier->LoadSignatureSb($sbXml);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

try {
    $verifier->VerifySignature(true);
    $bVerified = true;
} catch (\Chilkat2\Exception $e) {
    $bVerified = false;
}
if (!$bVerified) {
    echo $verifier->LastErrorText, "\n";
}

echo 'Signature verified = ', ($bVerified ? 'true' : 'false'), "\n";