(Objective-C) Get Certificate CRL Distribution Points

Demonstrates how to get a certificate's CRL Distribution Points extension data (assuming it exists). In the vast majority of cases, there will be one CRL Distribution Point.

Note: This example requires Chilkat v9.5.0.76 or greater.

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

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

CkoCert *cert = [[CkoCert alloc] init];

BOOL success = [cert LoadFromFile: @"qa_data/certs/test_haswdt.cer"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// Get the CRL Distribution Points extension, which is at OID 2.5.29.31
NSString *extensionXmlStr = [cert GetExtensionAsXml: @"2.5.29.31"];
if (cert.LastMethodSuccess == NO) {
    NSLog(@"%@",@"Certificate does not have the CDP extension.");
    return;
}

CkoXml *xml = [[CkoXml alloc] init];
[xml LoadXml: extensionXmlStr];

// See what we have..
NSLog(@"%@",[xml GetXml]);

// We should get XML like this:

// <?xml version="1.0" encoding="utf-8" ?>
// <sequence>
//     <sequence>
//         <contextSpecific tag="0" constructed="1">
//             <contextSpecific tag="0" constructed="1">
//                 <contextSpecific tag="6" constructed="0">aHR0cDovL2NybC5jb21vZG9jYS5jb20vQ09NT0RPUlNBQ2xpZW50QXV0aGVudGljYXRpb25hbmRTZWN1
// cmVFbWFpbENBLmNybA==</contextSpecific>
//             </contextSpecific>
//         </contextSpecific>
//     </sequence>
// </sequence>
// 

// Assuming there is one CRL Distribution Point...
CkoStringBuilder *sbDistPoint = [[CkoStringBuilder alloc] init];
success = [xml GetChildContentSb: @"sequence|contextSpecific|contextSpecific|contextSpecific" sb: sbDistPoint];
if (success == YES) {
    [sbDistPoint Decode: @"base64" charset: @"utf-8"];
    NSLog(@"%@%@",@"CRL Distribution Point:  ",[sbDistPoint GetAsString]);
}

// Sample output:
// CRL Distribution Point:  http://crl.comodoca.com/COMODORSAClientAuthenticationandSecureEmailCA.crl