IPhone app with SSL client certs

Question

I'm building an iphone app that needs to access a web service over https using client certificates. If I put the client cert (in pkcs12 format) in the app bundle, I'm able to load it into the app and make the https call (largely thanks to stackoverflow.com).

However, I need a way to distribute the app without any certs and leave it to the user to provide his own certificate. I thought I would just do that by instructing the user to import the certificate in iphone's profiles (settings->general->profiles), which is what you get by opening a .p12 file in Mail.app and then I would access that item in my app. I would expect that the certificates in profiles are available through the keychain API, but I guess I'm wrong on that.

1) Is there a way to access a certificate that I've already loaded in iphone's profile in my app?

2) What other options I have for loading a user specified certificate in my app? The only thing I can come up with is providing some interface where the user can give an URL to his .p12 cerificate, which I can then load into the app's keychain for later use, but thats not exactly user-friednly. I'm looking for something that would allow the user to put the cert on phone (email it to himself) and then load it in my app.

Answer 1

I've tried with this:

NSString *thePath = [[NSBundle mainBundle] pathForResource:@"certificate" ofType:@"p12"]; 
NSData *PKCS12Data = [[NSData alloc] initWithContentsOfFile:thePath]; 
CFDataRef inPKCS12Data = (CFDataRef)PKCS12Data; 
CFStringRef password = CFSTR("pass"); 
const void *keys[] = { kSecImportExportPassphrase }; 
const void *values[] = { password }; 
CFDictionaryRef optionsDictionary = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL); 
CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL); 
SecPKCS12Import(inPKCS12Data, optionsDictionary, &items); 

inPKCS12Data is correct but items is empty. What is happening?

Answer 2

I've done this for a recent app by making the documents folder for the app accessible via itunes. Our users are then instructed to drag their generated key (in a p12 format file) into the documents panel for our app in iTunes. When the app is started, it checks for the existence of the p12 file and, if it exists, imports the file into the keychain.

It's not the simplest procedure, but it is the most secure because you don't have a private key file being sent around via email.