Add first-time education sheet for Key Transparency

Signal/Images.xcassets/safety-numbers/Contents.json

@@ -0,0 +1,6 @@
+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Signal/Images.xcassets/safety-numbers/safety-number-verification.imageset/Contents.json

@@ -0,0 +1,12 @@
+{
+  "images" : [
+    {
+      "filename" : "safety-number-verification.pdf",
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Signal/src/ViewControllers/DebugUI/DebugUIPrompts.swift

@@ -19,6 +19,11 @@ class DebugUIPrompts: DebugUIPage {
         var items = [OWSTableItem]()
 
         items += [
+            OWSTableItem(title: "Reenable KT first-time education", actionBlock: {
+                db.write { tx in
+                    KeyTransparencyManager.setHasShownFirstTimeEducation(false, tx: tx)
+                }
+            }),
 
             OWSTableItem(title: "Reenable disabled inactive linked device reminder megaphones", actionBlock: {
                 db.write { tx in

Signal/translations/en.lproj/Localizable.strings

@@ -7609,6 +7609,12 @@
 /* Title for a button while automatic key verification is ongoing. */
 "SAFETY_NUMBERS_AUTOMATIC_VERIFICATION_BUTTON_VERIFYING" = "Verifying Encryption…";
 
+/* Body for a sheet introducing Key Transparency. */
+"SAFETY_NUMBERS_AUTOMATIC_VERIFICATION_EDUCATION_SHEET_BODY" = "For contacts you’re connected to by phone number, Signal can automatically confirm whether the connection is secure using a process called key transparency. For added security, you can still verify connections manually using a QR code or number.";
+
+/* Title for a sheet introducing Key Transparency. */
+"SAFETY_NUMBERS_AUTOMATIC_VERIFICATION_EDUCATION_SHEET_TITLE" = "Signal can now automatically verify encryption";
+
 /* Body for a sheet explaining that encryption auto-verification did not succeed. Embeds {{ 1: the contact's name }}. */
 "SAFETY_NUMBERS_AUTOMATIC_VERIFICATION_FAILURE_SHEET_BODY_FORMAT" = "Signal can no longer automatically verify the encryption for this chat. This is likely because %1$@ changed their phone number. Verify end-to-end encryption manually by comparing the numbers on the previous screen or scanning the code on their device.";
 

SignalServiceKit/KeyTransparency/KeyTransparencyManager.swift

@@ -10,6 +10,25 @@ public final class KeyTransparencyManager {
     private static let logger = PrefixedLogger(prefix: "[KT]")
     private var logger: PrefixedLogger { Self.logger }
 
+    private static let kvStore = NewKeyValueStore(collection: "KeyTransparencyManager")
+    private var kvStore: NewKeyValueStore { Self.kvStore }
+
+    /// Keys for `kvStore`.
+    /// - Important
+    /// If you're adding a new key here, consider whether it should be wiped
+    /// when Key Transparency is disabled. See: `setIsEnabled`.
+    private enum KVStoreKeys {
+        /// Keys to a `Bool` representing whether or not KT is enabled.
+        static let isEnabled = "isEnabled"
+        /// Keys to a `SelfCheckState`'s raw value.
+        static let selfCheckState = "selfCheckState"
+        /// Keys to a `Bool` representing whether or not we should show
+        /// first-time education about KT.
+        static let shouldShowFirstTimeEducation = "shouldShowFirstTimeEducation"
+        /// Keys to an opaque LibSignalClient blob.
+        static let distinguishedTreeHead = "distinguishedTreeHead"
+    }
+
     private let chatConnectionManager: ChatConnectionManager
     private let dateProvider: DateProvider
     private let db: DB
@@ -253,20 +272,17 @@ public final class KeyTransparencyManager {
         case failedRepeatedlyAndWarned = 4
     }
 
-    private static let selfCheckKVStore = NewKeyValueStore(collection: "KT.SelfCheck")
-    private static let selfCheckKVStoreKey = "state"
-
     private static func selfCheckState(tx: DBReadTransaction) -> SelfCheckState? {
-        return selfCheckKVStore.fetchValue(
+        return kvStore.fetchValue(
             Int64.self,
-            forKey: selfCheckKVStoreKey,
+            forKey: KVStoreKeys.selfCheckState,
             tx: tx,
         )
         .map { SelfCheckState(rawValue: $0)! }
     }
 
     private static func setSelfCheckState(_ state: SelfCheckState, tx: DBWriteTransaction) {
-        selfCheckKVStore.writeValue(state.rawValue, forKey: selfCheckKVStoreKey, tx: tx)
+        kvStore.writeValue(state.rawValue, forKey: KVStoreKeys.selfCheckState, tx: tx)
     }
 
     public static func shouldWarnSelfCheckFailed(tx: DBReadTransaction) -> Bool {
@@ -504,43 +520,47 @@ public final class KeyTransparencyManager {
 
     // MARK: - Opt-out
 
-    private static let isEnabledKVStore = NewKeyValueStore(collection: "KT.IsEnabled")
-    private static let isEnabledKVStoreKey = "isEnabled"
-
     public static func isEnabled(tx: DBReadTransaction) -> Bool {
         guard BuildFlags.KeyTransparency.enabled else {
             return false
         }
 
-        return isEnabledKVStore.fetchValue(Bool.self, forKey: isEnabledKVStoreKey, tx: tx) ?? true
+        return kvStore.fetchValue(Bool.self, forKey: KVStoreKeys.isEnabled, tx: tx) ?? true
     }
 
     public static func setIsEnabled(_ isEnabled: Bool, tx: DBWriteTransaction) {
         logger.info("\(isEnabled)")
 
-        isEnabledKVStore.writeValue(isEnabled, forKey: isEnabledKVStoreKey, tx: tx)
+        kvStore.writeValue(isEnabled, forKey: KVStoreKeys.isEnabled, tx: tx)
 
         if !isEnabled {
-            selfCheckKVStore.removeAll(tx: tx)
+            kvStore.removeValue(forKey: KVStoreKeys.distinguishedTreeHead, tx: tx)
+            kvStore.removeValue(forKey: KVStoreKeys.selfCheckState, tx: tx)
             selfCheckCronStore.setMostRecentDate(.distantPast, jitter: 0, tx: tx)
-            distinguishedTreeKVStore.removeAll(tx: tx)
             failIfThrows {
                 try KeyTransparencyRecord.deleteAll(tx.database)
             }
         }
     }
 
+    // MARK: - First-time education
+
+    public static func shouldShowFirstTimeEducation(tx: DBReadTransaction) -> Bool {
+        return kvStore.fetchValue(Bool.self, forKey: KVStoreKeys.shouldShowFirstTimeEducation, tx: tx) ?? true
+    }
+
+    public static func setHasShownFirstTimeEducation(_ value: Bool, tx: DBWriteTransaction) {
+        kvStore.writeValue(value, forKey: KVStoreKeys.shouldShowFirstTimeEducation, tx: tx)
+    }
+
     // MARK: -
 
-    private static let distinguishedTreeKVStore = NewKeyValueStore(collection: "KT.DistinguishedTree")
-    private static let distinguishedTreeKVStoreKey = "head"
-
     fileprivate static func getLastDistinguishedTreeHead(tx: DBReadTransaction) -> Data? {
-        return distinguishedTreeKVStore.fetchValue(Data.self, forKey: distinguishedTreeKVStoreKey, tx: tx)
+        return kvStore.fetchValue(Data.self, forKey: KVStoreKeys.distinguishedTreeHead, tx: tx)
     }
 
     fileprivate static func setLastDistinguishedTreeHead(_ blob: Data, tx: DBWriteTransaction) {
-        distinguishedTreeKVStore.writeValue(blob, forKey: distinguishedTreeKVStoreKey, tx: tx)
+        kvStore.writeValue(blob, forKey: KVStoreKeys.distinguishedTreeHead, tx: tx)
     }
 
     fileprivate static func getKeyTransparencyRecord(

SignalUI/SafetyNumbers/FingerprintViewController.swift

@@ -32,12 +32,14 @@ public class FingerprintViewController: OWSViewController, OWSNavigationChildCon
 
         let fingerprintResult: FingerprintResult?
         let keyTransparencyState: KeyTransparencyState?
+        let keyTransparencyShouldShowEducation: Bool
         (
             fingerprintResult,
             keyTransparencyState,
+            keyTransparencyShouldShowEducation,
         ) = db.read { tx in
             guard let theirAci else {
-                return (nil, nil)
+                return (nil, nil, false)
             }
 
             let theirAddress = SignalServiceAddress(theirAci)
@@ -50,7 +52,7 @@ public class FingerprintViewController: OWSViewController, OWSNavigationChildCon
                 let localIdentifiers = tsAccountManager.localIdentifiers(tx: tx),
                 let myAciIdentityKey = identityManager.identityKeyPair(for: .aci, tx: tx)?.keyPair.identityKey
             else {
-                return (nil, nil)
+                return (nil, nil, false)
             }
 
             let keyTransparencyIsEnabled = KeyTransparencyManager.isEnabled(tx: tx)
@@ -59,6 +61,7 @@ public class FingerprintViewController: OWSViewController, OWSNavigationChildCon
                 localIdentifiers: localIdentifiers,
                 tx: tx,
             )
+            let keyTransparencyShouldShowEducation = KeyTransparencyManager.shouldShowFirstTimeEducation(tx: tx)
 
             return (
                 FingerprintResult(
@@ -78,6 +81,7 @@ public class FingerprintViewController: OWSViewController, OWSNavigationChildCon
                     checkParams: keyTransparencyCheckParams,
                     viewInitialState: keyTransparencyCheckParams == nil ? .unableToVerify : .readyToVerify,
                 ),
+                keyTransparencyShouldShowEducation,
             )
         }
 
@@ -112,7 +116,19 @@ public class FingerprintViewController: OWSViewController, OWSNavigationChildCon
             ),
         )
         let navigationController = OWSNavigationController(rootViewController: fingerprintViewController)
-        viewController.present(navigationController, animated: true)
+
+        if keyTransparencyShouldShowEducation {
+            let educationSheet = KeyTransparencyFirstTimeEducationHeroSheet {
+                db.write { tx in
+                    KeyTransparencyManager.setHasShownFirstTimeEducation(true, tx: tx)
+                }
+
+                viewController.present(navigationController, animated: true)
+            }
+            viewController.present(educationSheet, animated: true)
+        } else {
+            viewController.present(navigationController, animated: true)
+        }
     }
 
     // MARK: -
@@ -846,6 +862,32 @@ private final class KeyTransparencyFailureHeroSheet: HeroSheetViewController {
 
 // MARK: -
 
+private final class KeyTransparencyFirstTimeEducationHeroSheet: HeroSheetViewController {
+    init(onContinue: @MainActor @escaping () -> Void) {
+        super.init(
+            hero: .image(UIImage(named: "safety-number-verification")!),
+            title: OWSLocalizedString(
+                "SAFETY_NUMBERS_AUTOMATIC_VERIFICATION_EDUCATION_SHEET_TITLE",
+                comment: "Title for a sheet introducing Key Transparency.",
+            ),
+            body: OWSLocalizedString(
+                "SAFETY_NUMBERS_AUTOMATIC_VERIFICATION_EDUCATION_SHEET_BODY",
+                comment: "Body for a sheet introducing Key Transparency.",
+            ),
+            primaryButton: HeroSheetViewController.Button(
+                title: CommonStrings.continueButton,
+                action: { sheet in
+                    sheet.dismiss(animated: true) {
+                        onContinue()
+                    }
+                },
+            ),
+        )
+    }
+}
+
+// MARK: -
+
 #if DEBUG
 
 private extension IdentityKey {