Refactoring

Notification Service Extension/NotificationService.swift

@@ -1,10 +1,7 @@
 // Copyright © 2020 Metabolist. All rights reserved.
 
-import CryptoKit
-import Keychain
 import Kingfisher
 import Mastodon
-import Secrets
 import ServiceLayer
 import UserNotifications
 
@@ -28,13 +25,13 @@ final class NotificationService: UNNotificationServiceExtension {
 
         guard let bestAttemptContent = bestAttemptContent else { return }
 
-        let pushNotification: PushNotification
+        let parsingService = PushNotificationParsingService(environment: environment)
         let decryptedJSON: Data
         let identityId: Identity.Id
+        let pushNotification: PushNotification
 
         do {
-            (decryptedJSON, identityId) = try Self.extractAndDecrypt(userInfo: request.content.userInfo)
+            (decryptedJSON, identityId) = try parsingService.extractAndDecrypt(userInfo: request.content.userInfo)
-
             pushNotification = try MastodonDecoder().decode(PushNotification.self, from: decryptedJSON)
         } catch {
             contentHandler(bestAttemptContent)
@@ -72,105 +69,7 @@ final class NotificationService: UNNotificationServiceExtension {
     }
 }
 
-enum NotificationServiceError: Error {
-    case userInfoDataAbsent
-    case keychainDataAbsent
-}
-
 private extension NotificationService {
-    static let identityIdUserInfoKey = "i"
-    static let encryptedMessageUserInfoKey = "m"
-    static let saltUserInfoKey = "s"
-    static let serverPublicKeyUserInfoKey = "k"
-    static let keyLength = 16
-    static let nonceLength = 12
-    static let pseudoRandomKeyLength = 32
-    static let paddedByteCount = 2
-    static let curve = "P-256"
-
-    enum HKDFInfo: String {
-        case auth, aesgcm, nonce
-
-        var bytes: [UInt8] {
-            Array("Content-Encoding: \(self)\0".utf8)
-        }
-    }
-
-    static func extractAndDecrypt(userInfo: [AnyHashable: Any]) throws -> (Data, Identity.Id) {
-        guard
-            let identityIdString = userInfo[identityIdUserInfoKey] as? String,
-            let identityId = Identity.Id(uuidString: identityIdString),
-            let encryptedMessageBase64 = (userInfo[encryptedMessageUserInfoKey] as? String)?.URLSafeBase64ToBase64(),
-            let encryptedMessage = Data(base64Encoded: encryptedMessageBase64),
-            let saltBase64 = (userInfo[saltUserInfoKey] as? String)?.URLSafeBase64ToBase64(),
-            let salt = Data(base64Encoded: saltBase64),
-            let serverPublicKeyBase64 = (userInfo[serverPublicKeyUserInfoKey] as? String)?.URLSafeBase64ToBase64(),
-            let serverPublicKeyData = Data(base64Encoded: serverPublicKeyBase64)
-        else { throw NotificationServiceError.userInfoDataAbsent }
-
-        let secretsService = Secrets(identityId: identityId, keychain: LiveKeychain.self)
-
-        guard
-            let auth = try secretsService.getPushAuth(),
-            let pushKey = try secretsService.getPushKey()
-        else { throw NotificationServiceError.keychainDataAbsent }
-
-        return (try decrypt(encryptedMessage: encryptedMessage,
-                           privateKeyData: pushKey,
-                           serverPublicKeyData: serverPublicKeyData,
-                           auth: auth,
-                           salt: salt),
-                identityId)
-    }
-
-    static func decrypt(encryptedMessage: Data,
-                        privateKeyData: Data,
-                        serverPublicKeyData: Data,
-                        auth: Data,
-                        salt: Data) throws -> Data {
-        let privateKey = try P256.KeyAgreement.PrivateKey(x963Representation: privateKeyData)
-        let serverPublicKey = try P256.KeyAgreement.PublicKey(x963Representation: serverPublicKeyData)
-        let sharedSecret = try privateKey.sharedSecretFromKeyAgreement(with: serverPublicKey)
-
-        var keyInfo = HKDFInfo.aesgcm.bytes
-        var nonceInfo = HKDFInfo.nonce.bytes
-        var context = Array(curve.utf8)
-        let publicKeyData = privateKey.publicKey.x963Representation
-
-        context.append(0)
-        context.append(0)
-        context.append(UInt8(publicKeyData.count))
-        context += Array(publicKeyData)
-        context.append(0)
-        context.append(UInt8(serverPublicKeyData.count))
-        context += Array(serverPublicKeyData)
-
-        keyInfo += context
-        nonceInfo += context
-
-        let pseudoRandomKey = sharedSecret.hkdfDerivedSymmetricKey(
-            using: SHA256.self,
-            salt: auth,
-            sharedInfo: HKDFInfo.auth.bytes,
-            outputByteCount: pseudoRandomKeyLength)
-        let key = HKDF<SHA256>.deriveKey(
-            inputKeyMaterial: pseudoRandomKey,
-            salt: salt,
-            info: keyInfo,
-            outputByteCount: keyLength)
-        let nonce = HKDF<SHA256>.deriveKey(
-            inputKeyMaterial: pseudoRandomKey,
-            salt: salt,
-            info: nonceInfo,
-            outputByteCount: nonceLength)
-
-        let sealedBox = try AES.GCM.SealedBox(combined: nonce.withUnsafeBytes(Array.init) + encryptedMessage)
-        let decrypted = try AES.GCM.open(sealedBox, using: key)
-        let unpadded = decrypted.suffix(from: paddedByteCount)
-
-        return Data(unpadded)
-    }
-
     static func addImage(pushNotification: PushNotification,
                          bestAttemptContent: UNMutableNotificationContent,
                          contentHandler: @escaping (UNNotificationContent) -> Void) {
@@ -208,16 +107,3 @@ private extension NotificationService {
         }
     }
 }
-
-extension String {
-    func URLSafeBase64ToBase64() -> String {
-        var base64 = replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/")
-        let countMod4 = count % 4
-
-        if countMod4 != 0 {
-            base64.append(String(repeating: "=", count: 4 - countMod4))
-        }
-
-        return base64
-    }
-}

ServiceLayer/Sources/ServiceLayer/Services/PushNotificationParsingService.swift

@@ -0,0 +1,129 @@
+// Copyright © 2021 Metabolist. All rights reserved.
+
+import CryptoKit
+import Foundation
+import Mastodon
+import Secrets
+
+enum NotificationExtensionServiceError: Error {
+    case userInfoDataAbsent
+    case keychainDataAbsent
+}
+
+public struct PushNotificationParsingService {
+    private let environment: AppEnvironment
+
+    public init(environment: AppEnvironment) {
+        self.environment = environment
+    }
+}
+
+public extension PushNotificationParsingService {
+    func extractAndDecrypt(userInfo: [AnyHashable: Any]) throws -> (Data, Identity.Id) {
+        guard let identityIdString = userInfo[Self.identityIdUserInfoKey] as? String,
+              let identityId = Identity.Id(uuidString: identityIdString),
+              let encryptedMessageBase64 = (userInfo[Self.encryptedMessageUserInfoKey] as? String)?
+                .URLSafeBase64ToBase64(),
+              let encryptedMessage = Data(base64Encoded: encryptedMessageBase64),
+              let saltBase64 = (userInfo[Self.saltUserInfoKey] as? String)?.URLSafeBase64ToBase64(),
+              let salt = Data(base64Encoded: saltBase64),
+              let serverPublicKeyBase64 = (userInfo[Self.serverPublicKeyUserInfoKey] as? String)?
+                .URLSafeBase64ToBase64(),
+              let serverPublicKeyData = Data(base64Encoded: serverPublicKeyBase64)
+        else { throw NotificationExtensionServiceError.userInfoDataAbsent }
+
+        let secrets = Secrets(identityId: identityId, keychain: environment.keychain)
+
+        guard let auth = try secrets.getPushAuth(),
+              let pushKey = try secrets.getPushKey()
+        else { throw NotificationExtensionServiceError.keychainDataAbsent }
+
+        return (try Self.decrypt(encryptedMessage: encryptedMessage,
+                                 privateKeyData: pushKey,
+                                 serverPublicKeyData: serverPublicKeyData,
+                                 auth: auth,
+                                 salt: salt),
+                identityId)
+    }
+}
+
+private extension PushNotificationParsingService {
+    static let identityIdUserInfoKey = "i"
+    static let encryptedMessageUserInfoKey = "m"
+    static let saltUserInfoKey = "s"
+    static let serverPublicKeyUserInfoKey = "k"
+    static let keyLength = 16
+    static let nonceLength = 12
+    static let pseudoRandomKeyLength = 32
+    static let paddedByteCount = 2
+    static let curve = "P-256"
+
+    enum HKDFInfo: String {
+        case auth, aesgcm, nonce
+
+        var bytes: [UInt8] {
+            Array("Content-Encoding: \(self)\0".utf8)
+        }
+    }
+
+    static func decrypt(encryptedMessage: Data,
+                        privateKeyData: Data,
+                        serverPublicKeyData: Data,
+                        auth: Data,
+                        salt: Data) throws -> Data {
+        let privateKey = try P256.KeyAgreement.PrivateKey(x963Representation: privateKeyData)
+        let serverPublicKey = try P256.KeyAgreement.PublicKey(x963Representation: serverPublicKeyData)
+        let sharedSecret = try privateKey.sharedSecretFromKeyAgreement(with: serverPublicKey)
+
+        var keyInfo = HKDFInfo.aesgcm.bytes
+        var nonceInfo = HKDFInfo.nonce.bytes
+        var context = Array(curve.utf8)
+        let publicKeyData = privateKey.publicKey.x963Representation
+
+        context.append(0)
+        context.append(0)
+        context.append(UInt8(publicKeyData.count))
+        context += Array(publicKeyData)
+        context.append(0)
+        context.append(UInt8(serverPublicKeyData.count))
+        context += Array(serverPublicKeyData)
+
+        keyInfo += context
+        nonceInfo += context
+
+        let pseudoRandomKey = sharedSecret.hkdfDerivedSymmetricKey(
+            using: SHA256.self,
+            salt: auth,
+            sharedInfo: HKDFInfo.auth.bytes,
+            outputByteCount: pseudoRandomKeyLength)
+        let key = HKDF<SHA256>.deriveKey(
+            inputKeyMaterial: pseudoRandomKey,
+            salt: salt,
+            info: keyInfo,
+            outputByteCount: keyLength)
+        let nonce = HKDF<SHA256>.deriveKey(
+            inputKeyMaterial: pseudoRandomKey,
+            salt: salt,
+            info: nonceInfo,
+            outputByteCount: nonceLength)
+
+        let sealedBox = try AES.GCM.SealedBox(combined: nonce.withUnsafeBytes(Array.init) + encryptedMessage)
+        let decrypted = try AES.GCM.open(sealedBox, using: key)
+        let unpadded = decrypted.suffix(from: paddedByteCount)
+
+        return Data(unpadded)
+    }
+}
+
+private extension String {
+    func URLSafeBase64ToBase64() -> String {
+        var base64 = replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/")
+        let countMod4 = count % 4
+
+        if countMod4 != 0 {
+            base64.append(String(repeating: "=", count: 4 - countMod4))
+        }
+
+        return base64
+    }
+}