(Objective-C) Combine Timestamp Reply and Content File into a TimeStampData

Demonstrates how to combine a timestamp reply (RFC 3161) with a data file (any type of file) to create a TimeStampData structure (RFC 5544).

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#import <CkoBinData.h>
#import <CkoAsn.h>
#import <CkoXml.h>
#import <NSString.h>

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

// Also see this example:
// Send a TimeStamp Request to a TimeStamp Authority and get the Response

// Load a timestamp reply file
CkoBinData *bdTsr = [[CkoBinData alloc] init];
BOOL success = [bdTsr LoadFile: @"qa_data/tsd/sample.tsr"];
if (success != YES) {
    NSLog(@"%@",@"Failed to load timestamp reply file.");
    return;
}

// Load the tsr into an ASN.1 object.
CkoAsn *asnTsr = [[CkoAsn alloc] init];
success = [asnTsr LoadEncoded: [bdTsr GetEncoded: @"base64"] encoding: @"base64"];
if (success != YES) {
    NSLog(@"%@",asnTsr.LastErrorText);
    return;
}

// Get the timestamp reply as XML.
CkoXml *xmlTsr = [[CkoXml alloc] init];
[xmlTsr LoadXml: [asnTsr AsnToXml]];

// The timestamp reply XML begins like this:
// We'll want to remove the 1st "sequence" subtree.

//     <?xml version="1.0" encoding="utf-8"?>
//     <sequence>
//         <sequence>       <---- Remove this sub-tree.
//             <int>00</int>
//             <sequence>
//                 <utf8>Operation Okay</utf8>
//             </sequence>
//         </sequence>
//         <sequence>   
//             <oid>1.2.840.113549.1.7.2</oid>
//             <contextSpecific tag="0" constructed="1">
//             ...

// Remove the 1st sub-tree..
[xmlTsr RemoveChildByIndex: [NSNumber numberWithInt: 0]];

// In this example, the data file we're combining with the timestamp into a timestampData is a .p7m.
// However, it can be any type of file (text or binary), it doesn't matter..
CkoBinData *bdContent = [[CkoBinData alloc] init];
success = [bdContent LoadFile: @"qa_data/tsd/sample.p7m"];
if (success != YES) {
    NSLog(@"%@",@"Failed to load content file.");
    return;
}

// Begin building the TimeStampData.  
// We'll build as XML and then convert to ASN.1
CkoXml *xml = [[CkoXml alloc] init];
xml.Tag = @"sequence";
[xml UpdateChildContent: @"oid" value: @"1.2.840.113549.1.9.16.1.31"];
[xml UpdateAttrAt: @"contextSpecific" autoCreate: YES attrName: @"tag" attrValue: @"0"];
[xml UpdateAttrAt: @"contextSpecific" autoCreate: YES attrName: @"constructed" attrValue: @"1"];
[xml UpdateChildContent: @"contextSpecific|sequence|int" value: @"01"];
[xml UpdateChildContent: @"contextSpecific|sequence|octets" value: [bdContent GetEncoded: @"base64"]];
[xml UpdateAttrAt: @"contextSpecific|sequence|contextSpecific" autoCreate: YES attrName: @"tag" attrValue: @"0"];
[xml UpdateAttrAt: @"contextSpecific|sequence|contextSpecific" autoCreate: YES attrName: @"constructed" attrValue: @"1"];

CkoXml *xContext = [xml GetChildWithTag: @"contextSpecific|sequence|contextSpecific"];
[xContext AddChildTree: xmlTsr];

// Convert the XML to ASN.1
CkoAsn *tsd = [[CkoAsn alloc] init];
[tsd LoadAsnXml: [xml GetXml]];

// Write the timestamped data to a file.
success = [tsd WriteBinaryDer: @"qa_output/sample.tsd"];

// Alternatively, get the tsd ASN.1 as base64..
NSString *tsdBase64 = [tsd GetEncodedDer: @"base64_mime"];
NSLog(@"%@",tsdBase64);