(Objective-C) 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.

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <NSString.h>
#import <CkoHttp.h>
#import <CkoStringBuilder.h>
#import <CkoPrivateKey.h>
#import <CkoXmlDSigGen.h>
#import <CkoXmlDSig.h>

// 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..

NSString *url = @"https://www.chilkatsoft.com/exampleData/soapToSign.xml";
CkoHttp *http = [[CkoHttp alloc] init];
CkoStringBuilder *sbSoapXml = [[CkoStringBuilder alloc] init];
BOOL success = [http QuickGetSb: url sbContent: sbSoapXml];
if (success != YES) {
    NSLog(@"%@",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
CkoPrivateKey *ecKey = [[CkoPrivateKey alloc] init];
success = [ecKey LoadPemFile: @"qa_data/ecc/secp256r1-key.pem"];
if (success != YES) {
    NSLog(@"%@",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.
// 

CkoXmlDSigGen *xmlSigGen = [[CkoXmlDSigGen alloc] init];

// 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 != YES) {
    NSLog(@"%@",xmlSigGen.LastErrorText);
    return;
}

// Examine the signed SOAP XML:
NSLog(@"%@",[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:

CkoXmlDSig *verifier = [[CkoXmlDSig alloc] init];

// First load the XML containing the signature(s) to be verified.
success = [verifier LoadSignatureSb: sbSoapXml];
if (success != YES) {
    NSLog(@"%@",verifier.LastErrorText);
    return;
}

BOOL bVerified = [verifier VerifySignature: YES];
if (bVerified != YES) {
    NSLog(@"%@",verifier.LastErrorText);
}

NSLog(@"%@%d",@"Signature verified = ",bVerified);