Objective-C

Get Public Key from CSR

See more CSR Examples

Demonstrates how to get the public key from a CSR. Objective-C

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

BOOL success = NO;

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

CkoPem *pem = [[CkoPem alloc] init];

// No password is required.  Pass an empty password string..
NSString *noPassword = @"";
success = [pem LoadPemFile: @"qa_data/csr/csr2.pem" password: noPassword];
if (success != YES) {
    NSLog(@"%@",pem.LastErrorText);
    return;
}

NSString *strBase64 = [pem GetEncodedItem: @"csr" itemSubType: @"" encoding: @"base64" index: [NSNumber numberWithInt: 0]];

CkoAsn *asn = [[CkoAsn alloc] init];
success = [asn LoadEncoded: strBase64 encoding: @"base64"];
if (success != YES) {
    NSLog(@"%@",asn.LastErrorText);
    return;
}

// Convert the ASN.1 to XML.
CkoXml *xml = [[CkoXml alloc] init];
success = [xml LoadXml: [asn AsnToXml]];
NSLog(@"%@",[xml GetXml]);
NSLog(@"%@",@"----");

NSString *strModulusHex = [xml GetChildContent: @"bits"];
NSLog(@"%@%@",@"strModulusHex = ",strModulusHex);
NSLog(@"%@",@"----");

// We need the modulus as base64.
CkoBinData *bd = [[CkoBinData alloc] init];
[bd AppendEncoded: strModulusHex encoding: @"hex"];
NSString *modulus64 = [bd GetEncoded: @"base64"];
NSLog(@"%@%@",@"modulus64 = ",modulus64);
NSLog(@"%@",@"----");

// Build the XML for the public key.
CkoXml *xmlPubKey = [[CkoXml alloc] init];
xmlPubKey.Tag = @"RSAPublicKey";
[xmlPubKey UpdateChildContent: @"Modulus" value: modulus64];
// The RSA exponent will always be decimal 65537 (base64 = AQAB)
[xmlPubKey UpdateChildContent: @"Exponent" value: @"AQAB"];

NSLog(@"%@",@"RSA public key as XML:");
NSLog(@"%@",[xmlPubKey GetXml]);
NSLog(@"%@",@"----");

// Load the XML into a Chilkat public key object.
CkoPublicKey *pubkey = [[CkoPublicKey alloc] init];
success = [pubkey LoadFromString: [xmlPubKey GetXml]];
if (success != YES) {
    NSLog(@"%@",pubkey.LastErrorText);
    return;
}

// Show the public key as PEM.
BOOL preferPkcs1 = YES;
NSLog(@"%@",[pubkey GetPem: preferPkcs1]);