(Objective-C) Extract SignatureValue from Signed XML

See more XML Digital Signatures Examples

Demonstrates how to extract the signature value from signed XML.

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#import <NSString.h>
#import <CkoStringBuilder.h>
#import <CkoXml.h>

// This example will work with the following signed XML, which as been reformatted for readability.

// <?xml version="1.0" encoding="utf-8"?>
// <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#rsa-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>C+7FWngU....DJFBcdg==</ds:SignatureValue>
//                 <ds:KeyInfo>
//                     <ds:KeyValue>
//                         <ds:RSAKeyValue>
//                             <ds:Modulus>sXeRhM55P13.....NAcibRw==</ds:Modulus>
//                             <ds:Exponent>AQAB</ds:Exponent>
//                         </ds:RSAKeyValue>
//                     </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>

// -----------------------------------------------------------------------------------------
// There are a number of ways we can get the contents of the  <ds:SignatureValue>...</ds:SignatureValue>

NSString *filePath = @"qa_data/xml_dsig_testing/sample_to_show_how_to_extract_sig.xml";

// If you know there will only be a single SignatureValue in the XML, you don't need to parse XML.
// Just do quick and simple string search..
// For example:
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
BOOL success = [sb LoadFile: filePath charset: @"utf-8"];
if (success == NO) {
    NSLog(@"%@",@"Failed to load file.");
    return;
}

NSString *base64Sig = [sb GetBetween: @"SignatureValue>" endMark: @"</"];
NSLog(@"%@%@",@"base64Sig = ",base64Sig);

// -----------------------------------------------------------------------------------------
// If the XML might contain multiple signatures, but the signatures will always be located in the 
// same place, then you can (beforehand) copy a sample signed XML into Chilkat's online tool
// at Generate Parsing Code from XML
// to get the path to the SignatureValue.  For example, the line of code generated for the SignatureValue
// for the above XML is:
// string ds_SignatureValue = xml.GetChildContent("SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue");

// So you can simply use that path..
CkoXml *xml = [[CkoXml alloc] init];
success = [xml LoadXmlFile: filePath];
// Assume success..

base64Sig = [xml GetChildContent: @"SOAP-ENV:Header|wsse:Security|ds:Signature|ds:SignatureValue"];
NSLog(@"%@%@",@"base64Sig = ",base64Sig);

// -----------------------------------------------------------------------------------------
// Or perhaps you don't know where the signature is located in the XML.
// You can search for the tag..
CkoXml *xSigVal = [xml SearchForTag: xml tag: @"*:SignatureValue"];
if (xml.LastMethodSuccess == YES) {
    NSLog(@"%@%@",@"base64Sig = ",xSigVal.Content);

}
else {
    NSLog(@"%@",@"No SignatureValue found.");
}