(Objective-C) Get Certificate Distinguished Name in .NET Format

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Certificate distinguished names (DN's), in the real world, can be constructed in various ways. Some systems expect certain ways of doing things. This example demonstrates how to get a DN (or SimpleName) exactly as .NET would return it.

This example requires Chilkat v9.5.0.96.

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

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

BOOL success = [cert LoadFromFile: @"qa_data/certs/testCert.cer"];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// In 99% of all cases, Chilkat already returns the Distinguished Name in the identical format as .NET.
// 
// In most cases, (internal to the certificate) the ASN.1 for the certificate's Subject 
// contains a sesquence of OIDs and values, where each OID is the single item in a SET.
// For example:

// SEQUENCE (3 elem)
//       SET (1 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.6 countryName (X.520 DN component)
//           PrintableString FR
//       SET (1 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.12 title (X.520 DN component)
//           UTF8String Mdecin
//       SET (3 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.42 givenName (X.520 DN component)
//           UTF8String ALAIN
//       SET (3 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.4 surname (X.520 DN component)
//           UTF8String DUBOIS RPPS
//       SET (3 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.3 commonName (X.520 DN component)
//           UTF8String 389900098933

// If we look at the DN, we get this:
NSString *subjectDN = cert.SubjectDN;
NSLog(@"%@",subjectDN);

// Chilkat produces this:
// C=FR, Title=Mdecin, G=ALAIN, SN=DUBOIS RPPS, CN=389900098933

// However, if the certificate's internal ASN.1 groups several items in a single SET,
// such as shown below, Microsoft .NET will produce a DN like this:
// G=ALAIN + SN=DUBOIS RPPS + CN=389900098933, T=Mdecin, C=FR

// Notice how the items in the SET are grouped with " + ".
// Also notice the order is reverse, and "T" is used instead of using "Title.
// These are all variations of how a DN might be formatted.
// In practice, there is no correct way because what is needed depends on what is
// required as input to whatever is receiving the DN.

// SEQUENCE (3 elem)
//       SET (1 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.6 countryName (X.520 DN component)
//           PrintableString FR
//       SET (1 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.12 title (X.520 DN component)
//           UTF8String Mdecin
//       SET (3 elem)
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.42 givenName (X.520 DN component)
//           UTF8String ALAIN
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.4 surname (X.520 DN component)
//           UTF8String DUBOIS RPPS
//         SEQUENCE (2 elem)
//           OBJECT IDENTIFIER 2.5.4.3 commonName (X.520 DN component)
//           UTF8String 389900098933

// To ensure Chilkat produces the same DN format as .NET, you can specify
// the keyword "DotNetSimpleName" in the UncommonOptions.
// For example:

cert.UncommonOptions = @"DotNetSimpleName";

// If the above option is used (which was added in Chilkat v9.5.0.96), then Chilkat
// will produce the DN in the same format as .NET

subjectDN = cert.SubjectDN;
NSLog(@"%@",subjectDN);

// Now Chilkat produces this:
// G=ALAIN + SN=DUBOIS RPPS + CN=389900098933, T=Mdecin, C=FR