Fixes issue where AltStore revokes its own certificate

Uses embedded certificate from AltServer if possible, but then falls back to asking user to refresh AltStore manually if the certificate used to install AltStore is revoked.

AltStore/Authentication/RefreshAltStoreViewController.swift

@@ -0,0 +1,87 @@
+//
+//  RefreshAltStoreViewController.swift
+//  AltStore
+//
+//  Created by Riley Testut on 10/26/19.
+//  Copyright © 2019 Riley Testut. All rights reserved.
+//
+
+import UIKit
+import AltSign
+
+import Roxas
+
+class RefreshAltStoreViewController: UIViewController
+{
+    var signer: ALTSigner!
+    
+    var completionHandler: ((Result<Void, Error>) -> Void)?
+    
+    @IBOutlet private var placeholderView: RSTPlaceholderView!
+    
+    override func viewDidLoad()
+    {
+        super.viewDidLoad()
+        
+        self.placeholderView.textLabel.isHidden = true
+        
+        self.placeholderView.detailTextLabel.textAlignment = .left
+        self.placeholderView.detailTextLabel.textColor = UIColor.white.withAlphaComponent(0.6)
+        self.placeholderView.detailTextLabel.text = NSLocalizedString("AltStore was unable to use an existing signing certificate, so it had to create a new one. This will cause any apps installed with an existing certificate to expire — including AltStore.\n\nTo prevent AltStore from expiring early, please refresh the app now. AltStore will quit once refreshing is complete.", comment: "")
+    }
+}
+
+private extension RefreshAltStoreViewController
+{
+    @IBAction func refreshAltStore(_ sender: PillButton)
+    {
+        guard let altStore = InstalledApp.fetchAltStore(in: DatabaseManager.shared.viewContext) else { return }
+                
+        func refresh()
+        {
+            sender.isIndicatingActivity = true
+            
+            if let progress = AppManager.shared.refreshProgress(for: altStore) ?? AppManager.shared.installationProgress(for: altStore)
+            {
+                // Cancel pending AltStore refresh so we can start a new one.
+                progress.cancel()
+            }
+            
+            let group = OperationGroup()
+            group.signer = self.signer // Prevent us from trying to authenticate a second time.
+            group.completionHandler = { (result) in
+                if let error = result.error ?? result.value?.values.compactMap({ $0.error }).first
+                {
+                    DispatchQueue.main.async {
+                        sender.progress = nil
+                        sender.isIndicatingActivity = false
+                        
+                        let alertController = UIAlertController(title: NSLocalizedString("Failed to Refresh AltStore", comment: ""), message: error.localizedDescription, preferredStyle: .alert)
+                        alertController.addAction(UIAlertAction(title: NSLocalizedString("Try Again", comment: ""), style: .default, handler: { (action) in
+                            refresh()
+                        }))
+                        alertController.addAction(UIAlertAction(title: NSLocalizedString("Refresh Later", comment: ""), style: .cancel, handler: { (action) in
+                            self.completionHandler?(.failure(error))
+                        }))
+                        
+                        self.present(alertController, animated: true, completion: nil)
+                    }
+                }
+                else
+                {
+                    self.completionHandler?(.success(()))
+                }
+            }
+            
+            _ = AppManager.shared.refresh([altStore], presentingViewController: self, group: group)
+            sender.progress = group.progress
+        }
+        
+        refresh()
+    }
+    
+    @IBAction func cancel(_ sender: UIButton)
+    {
+        self.completionHandler?(.failure(OperationError.cancelled))
+    }
+}