(Objective-C) SII Chile - FRMT Signature Computation and Add to XML

Compute the FRMT signature and add to the XML. This is the RSA signature of the SHA-1 digest of the "flattened" DD element.

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

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

// Also see:  Compute the FRMA Signature and Add to XML

CkoXml *xml = [[CkoXml alloc] init];

// Load the unsigned XML that contains the following:

// <DTE version="1.0">
//   <Documento ID="F60T33">
//         <TED version="1.0">
//             <DD>
// 		...
//                 <CAF version="1.0">
//                     <DA>
// 			...
//                     </DA>
//                     <FRMA algoritmo="SHA1withRSA">...</FRMA>
//                 </CAF>
//                 ...
//             </DD>
//             ... The FRMT will be added here in another example ...
//         </TED>
//   </Documento>
// </DTE>

BOOL success = [xml LoadXmlFile: @"qa_data/xml_dsig/sii_cl/test_1.xml"];
if (success == NO) {
    NSLog(@"%@",@"Failed to load initial XML file.");
    return;
}

// Get a reference to the "DD" element
CkoXml *ddXml = [xml FindChild: @"Documento|TED|DD"];
if (xml.LastMethodSuccess == NO) {
    NSLog(@"%@",@"Failed to find DD element");
    return;
}

//  We need to get the "flattened" DD XML where:
//    - No whitespace between elements.
//    - The 5 pre-defined entities are converted.
//    - The text is encoded in the ISO-8859-1 character set (Latin-1), 
CkoStringBuilder *sbFlattened = [[CkoStringBuilder alloc] init];
ddXml.EmitCompact = YES;
ddXml.EmitXmlDecl = NO;
[ddXml GetXmlSb: sbFlattened];

// Compute the SHA-1 message digest of the iso-8859-1 byte representation, 
// and sign it with our RSA private key, getting the result in base64 format.

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [privKey LoadAnyFormatFile: @"qa_data/rsa/rsaPrivKey_pkcs8.pem" password: @""];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

CkoRsa *rsa = [[CkoRsa alloc] init];
[rsa ImportPrivateKeyObj: privKey];

rsa.EncodingMode = @"base64";
rsa.Charset = @"iso-8859-1";
NSString *sig = [rsa SignStringENC: [sbFlattened GetAsString] hashAlg: @"sha1"];

// Add the FRMT signature element to the XML.
[xml UpdateChildContent: @"Documento|TED|FRMT" value: sig];
[xml UpdateAttrAt: @"Documento|TED|FRMT" autoCreate: YES attrName: @"algoritmo" attrValue: @"SHA1withRSA"];

// See what we have:
xml.EmitCompact = NO;
xml.EmitXmlDecl = YES;
NSLog(@"%@",[xml GetXml]);