WIP SPM

Sources/SecretKit/SecureEnclave/SecureEnclave.swift

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+public enum SecureEnclave {}

Sources/SecretKit/SecureEnclave/SecureEnclaveSecret.swift

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+import Foundation
+import Combine
+
+extension SecureEnclave {
+
+    public struct Secret: SecretKit.Secret {
+
+        public let id: Data
+        public let name: String
+        public let algorithm = Algorithm.ellipticCurve
+        public let keySize = 256
+        public let publicKey: Data
+
+    }
+
+}

Sources/SecretKit/SecureEnclave/SecureEnclaveStore.swift

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+import Foundation
+import Security
+import CryptoTokenKit
+import LocalAuthentication
+
+extension SecureEnclave {
+
+    public class Store: SecretStoreModifiable {
+
+        public var isAvailable: Bool {
+            // For some reason, as of build time, CryptoKit.SecureEnclave.isAvailable always returns false
+            // error msg "Received error sending GET UNIQUE DEVICE command"
+            // Verify it with TKTokenWatcher manually.
+            TKTokenWatcher().tokenIDs.contains("com.apple.setoken")
+        }
+        public let id = UUID()
+        public let name = NSLocalizedString("Secure Enclave", comment: "Secure Enclave")
+        @Published public private(set) var secrets: [Secret] = []
+
+        private var persistedAuthenticationContexts: [Secret: PersistentAuthenticationContext] = [:]
+
+        public init() {
+            DistributedNotificationCenter.default().addObserver(forName: .secretStoreUpdated, object: nil, queue: .main) { _ in
+                self.reloadSecrets(notify: false)
+            }
+            loadSecrets()
+        }
+
+        // MARK: Public API
+
+        public func create(name: String, requiresAuthentication: Bool) throws {
+            var accessError: SecurityError?
+            let flags: SecAccessControlCreateFlags
+            if requiresAuthentication {
+                flags = [.privateKeyUsage, .userPresence]
+            } else {
+                flags = .privateKeyUsage
+            }
+            let access =
+                SecAccessControlCreateWithFlags(kCFAllocatorDefault,
+                                                kSecAttrAccessibleWhenUnlockedThisDeviceOnly,
+                                                flags,
+                                                &accessError) as Any
+            if let error = accessError {
+                throw error.takeRetainedValue() as Error
+            }
+
+            let attributes = [
+                kSecAttrLabel: name,
+                kSecAttrKeyType: Constants.keyType,
+                kSecAttrTokenID: kSecAttrTokenIDSecureEnclave,
+                kSecAttrApplicationTag: Constants.keyTag,
+                kSecPrivateKeyAttrs: [
+                    kSecAttrIsPermanent: true,
+                    kSecAttrAccessControl: access
+                ]
+            ] as CFDictionary
+
+            var privateKey: SecKey? = nil
+            var publicKey: SecKey? = nil
+            let status = SecKeyGeneratePair(attributes, &publicKey, &privateKey)
+            guard privateKey != nil, let pk = publicKey else {
+                throw KeychainError(statusCode: status)
+            }
+            try savePublicKey(pk, name: name)
+            reloadSecrets()
+        }
+
+        public func delete(secret: Secret) throws {
+            let deleteAttributes = [
+                kSecClass: kSecClassKey,
+                kSecAttrApplicationLabel: secret.id as CFData
+            ] as CFDictionary
+            let status = SecItemDelete(deleteAttributes)
+            if status != errSecSuccess {
+                throw KeychainError(statusCode: status)
+            }
+            reloadSecrets()
+        }
+
+        public func update(secret: Secret, name: String) throws {
+            let updateQuery = [
+                kSecClass: kSecClassKey,
+                kSecAttrApplicationLabel: secret.id as CFData
+            ] as CFDictionary
+
+            let updatedAttributes = [
+                kSecAttrLabel: name,
+            ] as CFDictionary
+
+            let status = SecItemUpdate(updateQuery, updatedAttributes)
+            if status != errSecSuccess {
+                throw KeychainError(statusCode: status)
+            }
+            reloadSecrets()
+        }
+
+        public func sign(data: Data, with secret: SecretType, for provenance: SigningRequestProvenance) throws -> SignedData {
+            let context: LAContext
+            if let existing = persistedAuthenticationContexts[secret], existing.valid {
+                context = existing.context
+            } else {
+                let newContext = LAContext()
+                newContext.localizedCancelTitle = "Deny"
+                context = newContext
+            }
+            context.localizedReason = "sign a request from \"\(provenance.origin.displayName)\" using secret \"\(secret.name)\""
+            let attributes = [
+                kSecClass: kSecClassKey,
+                kSecAttrKeyClass: kSecAttrKeyClassPrivate,
+                kSecAttrApplicationLabel: secret.id as CFData,
+                kSecAttrKeyType: Constants.keyType,
+                kSecAttrTokenID: kSecAttrTokenIDSecureEnclave,
+                kSecAttrApplicationTag: Constants.keyTag,
+                kSecUseAuthenticationContext: context,
+                kSecReturnRef: true
+                ] as CFDictionary
+            var untyped: CFTypeRef?
+            let status = SecItemCopyMatching(attributes, &untyped)
+            if status != errSecSuccess {
+                throw KeychainError(statusCode: status)
+            }
+            guard let untypedSafe = untyped else {
+                throw KeychainError(statusCode: errSecSuccess)
+            }
+            let key = untypedSafe as! SecKey
+            var signError: SecurityError?
+
+            let signingStartTime = Date()
+            guard let signature = SecKeyCreateSignature(key, .ecdsaSignatureMessageX962SHA256, data as CFData, &signError) else {
+                throw SigningError(error: signError)
+            }
+            let signatureDuration = Date().timeIntervalSince(signingStartTime)
+            // Hack to determine if the user had to authenticate to sign.
+            // Since there's now way to inspect SecAccessControl to determine (afaict).
+            let requiredAuthentication = signatureDuration > Constants.unauthenticatedThreshold
+
+            return SignedData(data: signature as Data, requiredAuthentication: requiredAuthentication)
+        }
+
+        public func persistAuthentication(secret: Secret, forDuration duration: TimeInterval) throws {
+            let newContext = LAContext()
+            newContext.localizedCancelTitle = "Deny"
+
+            let formatter = DateComponentsFormatter()
+            formatter.unitsStyle = .spellOut
+            formatter.allowedUnits = [.hour, .minute, .day]
+
+            if let durationString = formatter.string(from: duration) {
+                newContext.localizedReason = "unlock secret \"\(secret.name)\" for \(durationString)"
+            } else {
+                newContext.localizedReason = "unlock secret \"\(secret.name)\""
+            }
+            newContext.evaluatePolicy(LAPolicy.deviceOwnerAuthentication, localizedReason: newContext.localizedReason) { [weak self] success, _ in
+                guard success else { return }
+                let context = PersistentAuthenticationContext(secret: secret, context: newContext, duration: duration)
+                self?.persistedAuthenticationContexts[secret] = context
+            }
+        }
+
+    }
+
+}
+
+extension SecureEnclave.Store {
+
+    private func reloadSecrets(notify: Bool = true) {
+        secrets.removeAll()
+        loadSecrets()
+        if notify {
+            DistributedNotificationCenter.default().post(name: .secretStoreUpdated, object: nil)
+        }
+    }
+
+    private func loadSecrets() {
+        let attributes = [
+            kSecClass: kSecClassKey,
+            kSecAttrKeyType: SecureEnclave.Constants.keyType,
+            kSecAttrApplicationTag: SecureEnclave.Constants.keyTag,
+            kSecAttrKeyClass: kSecAttrKeyClassPublic,
+            kSecReturnRef: true,
+            kSecMatchLimit: kSecMatchLimitAll,
+            kSecReturnAttributes: true
+            ] as CFDictionary
+        var untyped: CFTypeRef?
+        SecItemCopyMatching(attributes, &untyped)
+        guard let typed = untyped as? [[CFString: Any]] else { return }
+        let wrapped: [SecureEnclave.Secret] = typed.map {
+            let name = $0[kSecAttrLabel] as? String ?? "Unnamed"
+            let id = $0[kSecAttrApplicationLabel] as! Data
+            let publicKeyRef = $0[kSecValueRef] as! SecKey
+            let publicKeyAttributes = SecKeyCopyAttributes(publicKeyRef) as! [CFString: Any]
+            let publicKey = publicKeyAttributes[kSecValueData] as! Data
+            return SecureEnclave.Secret(id: id, name: name, publicKey: publicKey)
+        }
+        secrets.append(contentsOf: wrapped)
+    }
+
+    private func savePublicKey(_ publicKey: SecKey, name: String) throws {
+        let attributes = [
+            kSecClass: kSecClassKey,
+            kSecAttrKeyType: SecureEnclave.Constants.keyType,
+            kSecAttrKeyClass: kSecAttrKeyClassPublic,
+            kSecAttrApplicationTag: SecureEnclave.Constants.keyTag,
+            kSecValueRef: publicKey,
+            kSecAttrIsPermanent: true,
+            kSecReturnData: true,
+            kSecAttrLabel: name
+            ] as CFDictionary
+        let status = SecItemAdd(attributes, nil)
+        if status != errSecSuccess {
+            throw SecureEnclave.KeychainError(statusCode: status)
+        }
+    }
+
+}
+
+extension SecureEnclave {
+
+    public struct KeychainError: Error {
+        public let statusCode: OSStatus
+    }
+
+    public struct SigningError: Error {
+        public let error: SecurityError?
+    }
+
+}
+
+extension SecureEnclave {
+
+    public typealias SecurityError = Unmanaged<CFError>
+
+}
+
+extension SecureEnclave {
+
+    enum Constants {
+        static let keyTag = "com.maxgoedjen.secretive.secureenclave.key".data(using: .utf8)! as CFData
+        static let keyType = kSecAttrKeyTypeECSECPrimeRandom
+        static let unauthenticatedThreshold: TimeInterval = 0.05
+    }
+
+}
+
+extension SecureEnclave {
+
+    private struct PersistentAuthenticationContext {
+
+        let secret: Secret
+        let context: LAContext
+        // Monotonic time instead of Date() to prevent people setting the clock back.
+        let expiration: UInt64
+
+        init(secret: Secret, context: LAContext, duration: TimeInterval) {
+            self.secret = secret
+            self.context = context
+            let durationInNanoSeconds = Measurement(value: duration, unit: UnitDuration.seconds).converted(to: .nanoseconds).value
+            self.expiration = clock_gettime_nsec_np(CLOCK_MONOTONIC) + UInt64(durationInNanoSeconds)
+        }
+
+        var valid: Bool {
+            clock_gettime_nsec_np(CLOCK_MONOTONIC) < expiration
+        }
+    }
+
+}