How to share keychain data between iOS application

Question

I am describing a problem for which it took me quite some time to learn the answer.

The "GenericKeychain" example is a good start at providing a wrapper for sharing keychain data between applications when using the accessGroup in the init.

However, implementing this in my app yielded an obscure error code (which took forever to locate) -25243, which means: No access control.

I ran Apple's example app (GenericKeychain) on my iPad only to get the same error. Huh?

Does Apple's documentation fail to deliver on what is necessary to accomplish this?

Answer 1

Actually it's not hard to do. Please follow the steps.

App1:

1. Open your App's target Capabilities and enable KeyChain Sharing.
2. Add a identifier. (eg : com.example.sharedaccess)
3. Add "UICKeyChainStore" to your project.
4. Be sure you have a team id added to your App1 project.
5. Add Security.framework to your App1 project.

6. And add these codes to somewhere you need.

   [UICKeyChainStore setString:@"someValue" forKey:@"someKey" service:@"someService"];
   

App2:

• Open your App's target Capabilities and enable KeyChain Sharing.
• Add a identifier. (eg : com.example.sharedaccess)
• Add "UICKeyChainStore" to your project.
• Be sure you have a team id added to your App2 project.
• Add Security.framework to your App2 project.

• And add these codes to somewhere you need.

  NSString *string = [UICKeyChainStore stringForKey:@"someKey" service:@"someService"];
  

• Your TeamIDs should be same for both projects.

• I tried these steps on a real iPhone device.
• I also tried these steps with Automatic and iOs Development provisioning profile.
• My apps' bundle identifiers were like that : com.example.app1, com.example.app2.

Answer 2

After some (a lot of) digging throughout the web, I found the answer. The access Group that you use when constructing your KeychainItemWrapper class must ALSO be specified in each of your application's Entitlements.plist file in the "keychain-access-groups" section.

It seems almost obvious now that I see "keychain-access-groups". However, I had no idea to even look there. Hope this helps others.