Store SSH keys in the Secure Enclave
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secretive/Sources/Packages/Sources/SmartCardSecretKit/SmartCardStore.swift

178 lines
6.2 KiB

import Foundation
import Security
import CryptoTokenKit
import LocalAuthentication
import SecretKit
// TODO: Might need to split this up into "sub-stores?"
// ie, each token has its own Store.
extension SmartCard {
public class Store: SecretStore {
@Published public var isAvailable: Bool = false
public let id = UUID()
public private(set) var name = NSLocalizedString("Smart Card", comment: "Smart Card")
@Published public private(set) var secrets: [Secret] = []
private let watcher = TKTokenWatcher()
private var tokenID: String?
public init() {
tokenID = watcher.nonSecureEnclaveTokens.first
watcher.setInsertionHandler { string in
guard self.tokenID == nil else { return }
guard !string.contains("setoken") else { return }
self.tokenID = string
self.reloadSecrets()
self.watcher.addRemovalHandler(self.smartcardRemoved, forTokenID: string)
}
if let tokenID = tokenID {
self.isAvailable = true
self.watcher.addRemovalHandler(self.smartcardRemoved, forTokenID: tokenID)
}
loadSecrets()
}
// MARK: Public API
public func create(name: String) throws {
fatalError("Keys must be created on the smart card.")
}
public func delete(secret: Secret) throws {
fatalError("Keys must be deleted on the smart card.")
}
public func sign(data: Data, with secret: SecretType, for provenance: SigningRequestProvenance) throws -> SignedData {
guard let tokenID = tokenID else { fatalError() }
let context = LAContext()
context.localizedReason = "sign a request from \"\(provenance.origin.displayName)\" using secret \"\(secret.name)\""
context.localizedCancelTitle = "Deny"
let attributes = [
kSecClass: kSecClassKey,
kSecAttrKeyClass: kSecAttrKeyClassPrivate,
kSecAttrApplicationLabel: secret.id as CFData,
kSecAttrTokenID: tokenID,
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 signatureAlgorithm: SecKeyAlgorithm
switch (secret.algorithm, secret.keySize) {
case (.ellipticCurve, 256):
signatureAlgorithm = .ecdsaSignatureMessageX962SHA256
case (.ellipticCurve, 384):
signatureAlgorithm = .ecdsaSignatureMessageX962SHA384
default:
fatalError()
}
guard let signature = SecKeyCreateSignature(key, signatureAlgorithm, data as CFData, &signError) else {
throw SigningError(error: signError)
}
return SignedData(data: signature as Data, requiredAuthentication: false)
}
public func persistAuthentication(secret: SmartCard.Secret, forDuration: TimeInterval) throws {
}
}
}
extension SmartCard.Store {
private func smartcardRemoved(for tokenID: String? = nil) {
self.tokenID = nil
reloadSecrets()
}
private func reloadSecrets() {
DispatchQueue.main.async {
self.isAvailable = self.tokenID != nil
self.secrets.removeAll()
self.loadSecrets()
}
}
private func loadSecrets() {
guard let tokenID = tokenID else { return }
let fallbackName = NSLocalizedString("Smart Card", comment: "Smart Card")
if #available(macOS 12.0, *) {
if let driverName = watcher.tokenInfo(forTokenID: tokenID)?.driverName {
name = driverName
} else {
name = fallbackName
}
} else {
// Hack to read name if there's only one smart card
let slotNames = TKSmartCardSlotManager().slotNames
if watcher.nonSecureEnclaveTokens.count == 1 && slotNames.count == 1 {
name = slotNames.first!
} else {
name = fallbackName
}
}
let attributes = [
kSecClass: kSecClassKey,
kSecAttrTokenID: tokenID,
kSecAttrKeyType: kSecAttrKeyTypeEC, // Restrict to EC
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: [SmartCard.Secret] = typed.map {
let name = $0[kSecAttrLabel] as? String ?? "Unnamed"
let tokenID = $0[kSecAttrApplicationLabel] as! Data
let algorithm = Algorithm(secAttr: $0[kSecAttrKeyType] as! NSNumber)
let keySize = $0[kSecAttrKeySizeInBits] as! Int
let publicKeyRef = $0[kSecValueRef] as! SecKey
let publicKeySecRef = SecKeyCopyPublicKey(publicKeyRef)!
let publicKeyAttributes = SecKeyCopyAttributes(publicKeySecRef) as! [CFString: Any]
let publicKey = publicKeyAttributes[kSecValueData] as! Data
return SmartCard.Secret(id: tokenID, name: name, algorithm: algorithm, keySize: keySize, publicKey: publicKey)
}
secrets.append(contentsOf: wrapped)
}
}
extension TKTokenWatcher {
fileprivate var nonSecureEnclaveTokens: [String] {
tokenIDs.filter { !$0.contains("setoken") }
}
}
extension SmartCard {
public struct KeychainError: Error {
public let statusCode: OSStatus
}
public struct SigningError: Error {
public let error: SecurityError?
}
}
extension SmartCard {
public typealias SecurityError = Unmanaged<CFError>
}