(Objective-C) Get Certificate Authority Information Access

Demonstrates how to get a certificate's Authority Information Access extension data (if it exists).

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 Authority Information Access extension, which is at OID 1.3.6.1.5.5.7.1.1
NSString *extensionXmlStr = [cert GetExtensionAsXml: @"1.3.6.1.5.5.7.1.1"];
if (cert.LastMethodSuccess == NO) {
    NSLog(@"%@",@"Certificate does not have the AuthInfoAccess 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>
//         <oid>1.3.6.1.5.5.7.48.2</oid>
//         <contextSpecific tag="6" constructed="0">aHR0cDovL2NydC5jb21vZG9jYS5jb20vQ09NT0RPUlNBQ2xpZW50QXV0aGVudGljYXRpb25hbmRTZWN1
// cmVFbWFpbENBLmNydA==</contextSpecific>
//     </sequence>
//     <sequence>
//         <oid>1.3.6.1.5.5.7.48.1</oid>
//         <contextSpecific tag="6" constructed="0">aHR0cDovL29jc3AuY29tb2RvY2EuY29t</contextSpecific>
//     </sequence>
// </sequence>

// Typically, a certificate AIA(Authority Information access) contains 2 parts:
// 
//     On-line Certificate Status Protocol (1.3.6.1.5.5.7.48.1)
//     Certification Authority Issuer (1.3.6.1.5.5.7.48.2)
// 
// The base64 content for each OID (in this case) is just a string.  
// The data can be accessed and decoded like this:

CkoStringBuilder *sbOcsp = [[CkoStringBuilder alloc] init];
success = [xml GetChildContentSb: @"/C/oid,1.3.6.1.5.5.7.48.1|++" sb: sbOcsp];
if (success == YES) {
    [sbOcsp Decode: @"base64" charset: @"utf-8"];
    NSLog(@"%@%@",@"1.3.6.1.5.5.7.48.1:  ",[sbOcsp GetAsString]);
}

CkoStringBuilder *sbIssuer = [[CkoStringBuilder alloc] init];
success = [xml GetChildContentSb: @"/C/oid,1.3.6.1.5.5.7.48.2|++" sb: sbIssuer];
if (success == YES) {
    [sbIssuer Decode: @"base64" charset: @"utf-8"];
    NSLog(@"%@%@",@"1.3.6.1.5.5.7.48.2:  ",[sbIssuer GetAsString]);
}

// The output looks like this:

// 1.3.6.1.5.5.7.48.1:  http://ocsp.comodoca.com
// 1.3.6.1.5.5.7.48.2:  http://crt.comodoca.com/COMODORSAClientAuthenticationandSecureEmailCA.crt

// -------------------------------------------------------------------------------
// Note: The Chilkat path passed to GetChildContentSb is composed of two commands:
// The first command is "/C/oid,1.3.6.1.5.5.7.48.1".   It says "traverse the XML tree from the caller
// node and stop at the 1st node having tag = "oid" and content = "1.3.6.1.5.5.7.48.1".
// The "|" char separates the 1st command from the 2nd.
// The 2nd command is "++" and says "move to the next sibling".