How to decode serial number,issuer information etc from certificate present in keychain under iOS?

Question

I am creating an iOS application that can retrieve informations of certificate(.cer) present in keychain.

Reference links: Link1, Link2

Below is the code:

const char *certLabelString = "Certificates";
    CFStringRef certLabel = CFStringCreateWithCString(
                                                      NULL, certLabelString,
                                                      kCFStringEncodingUTF8);

const void *keys[] =   { kSecClass, kSecAttrLabel, kSecReturnAttributes };
    const void *values[] = { kSecClassCertificate, certLabel, kCFBooleanTrue };

CFDictionaryRef dict = CFDictionaryCreate(NULL, keys,
                                              values, 3,
                                              NULL, NULL)
 if ((SecItemCopyMatching(dict, &myCertData)) == errSecSuccess){
            NSLog(@"Certificate found");

            CFDictionaryRef dictCertificateRef = (CFDictionaryRef)myCertData;

            NSDictionary *dictCertificate = (__bridge NSDictionary *)dictCertificateRef;
            NSLog(@"%@",dictCertificate);

        }

Output:

I got the certificates data but I can see serial number or issuer name in encoded form.

Like this: issr = <310b3009 06035504 06130255 53311330 11060355 040a0c0a 4170706c 6520496e 632e312c 302a0603 55040b0c 23417070 6c652057 6f726c64 77696465 20446576 656c6f70 65722052 656c6174 696f6e73 31443042 06035504 030c3b41 70706c65 20576f72 6c647769 64652044 6576656c 6f706572 2052656c 6174696f 6e732043 65727469 66696361 74696f6e 20417574 686f7269 7479>;

Can some one please tell how to decode this information?

Alex Stone · Answer 1 · 2014-10-08T15:35:32.963

I would also be interested in knowing this. So far, poking around the cert, I did the following:

id data = [keychainDictionary objectForKey:@"issr"];

You can then set a breakpoint at this line, and as you step over it, select the "data" variable in the debug window left panel. Select "watch memory of *data", and you will see a bunch of garbage with real strings from that data. I don't know how to proceed from there.

enter image description here

Complete method that gets all keychain items and loads them in the table view:

-(void)loadDataSource
{

    //enumerate all items in keychain http://stackoverflow.com/questions/10966969/enumerate-all-keychain-items-in-my-ios-application
    NSMutableDictionary *query = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                  (__bridge id)kCFBooleanTrue, (__bridge id)kSecReturnAttributes,
                                  (__bridge id)kSecMatchLimitAll, (__bridge id)kSecMatchLimit,
                                  nil];

    NSArray *secItemClasses = [NSArray arrayWithObjects:
                               (__bridge id)kSecClassGenericPassword,
                               (__bridge id)kSecClassInternetPassword,
                               (__bridge id)kSecClassCertificate,
                               (__bridge id)kSecClassKey,
                               (__bridge id)kSecClassIdentity,
                               nil];


    NSMutableArray* results = [NSMutableArray array];

    for(int i = 0; i < (int)secItemClasses.count;i++)
    {
        [results addObject:[NSMutableArray array]];
    }



    for (id secItemClass in secItemClasses) {
        [query setObject:secItemClass forKey:(__bridge id)kSecClass];

        CFTypeRef result = NULL;
        SecItemCopyMatching((__bridge CFDictionaryRef)query, &result);
//        NSLog(@"%@", (__bridge id)result);
        if (result != NULL)
        {
            NSMutableArray* thisSection = results[[secItemClasses indexOfObject:secItemClass]];
            [thisSection addObject:(__bridge id)result];


//            [results addObject:(__bridge id)result];
            CFRelease(result);
        }

        for(NSArray* object in results[[secItemClasses indexOfObject:secItemClass]])
        {
            DLog(@"object is of class: %@",[[object class] description]);

            for (NSDictionary* innerObject in object)
            {
                DLog(@"object is of class: %@",[[innerObject class] description]);


            }




            }

        }

    self.datasource = results;

    [self.tableView reloadData];
}

//this is the description, you can assign it to a text label in a table view cell

-(NSMutableString*)descriptionForObject:(NSDictionary*)object
{
    NSMutableString* string = [[NSMutableString alloc] initWithCapacity:1024];

//    https://developer.apple.com/library/mac/documentation/security/Reference/keychainservices/Reference/reference.html
    //search for kSecAlias for a list of codes

    if(object[@"labl"] != nil)
    {
    [string appendString:[NSString stringWithFormat:@"Label: %@\n",object[@"labl"]]];
    }

    [string appendString:[NSString stringWithFormat:@"Created at: %@\n",object[@"cdat"]]];
    if(object[@"agrp"] != nil)
    {
        [string appendString:[NSString stringWithFormat:@"Belongs to application: %@\n",object[@"agrp"]]];
    }



    for(NSString* key in @[@"issr",@"subj"])
    {
        id data = [object objectForKey:key];


        @try {


            if([data isKindOfClass:[NSData class]]==NO)
            {
                continue;
            }
            NSString* stringAscii = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];


            NSCharacterSet* alphaNumeric = [NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.@"];


            NSCharacterSet *doNotWant = [alphaNumeric invertedSet];
            NSString* cleanedUpString = [[stringAscii componentsSeparatedByCharactersInSet: doNotWant] componentsJoinedByString: @" "];

            if(cleanedUpString.length>0)
            {
                DLog(@" %@ Cleaned up: %@",key,cleanedUpString);

                [string appendString:[NSString stringWithFormat:@" %@ Cleaned up: %@",key,cleanedUpString]];
            }
        }
        @catch (NSException *exception) {

        }
        @finally {

        }
    }


//    [string appendString:[NSString stringWithFormat:@"Complete description:(%@)\n", [object description]]];



    return string;
}

How to decode serial number,issuer information etc from certificate present in keychain under iOS?

1 Answers1