File size: 12,772 Bytes
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import DeviceCheck
import Foundation
import StoreKit
enum PushRelayError: LocalizedError {
case relayBaseURLMissing
case relayMisconfigured(String)
case invalidResponse(String)
case requestFailed(status: Int, message: String)
case unsupportedAppAttest
case missingReceipt
var errorDescription: String? {
switch self {
case .relayBaseURLMissing:
"Push relay base URL missing"
case let .relayMisconfigured(message):
message
case let .invalidResponse(message):
message
case let .requestFailed(status, message):
"Push relay request failed (\(status)): \(message)"
case .unsupportedAppAttest:
"App Attest unavailable on this device"
case .missingReceipt:
"App Store receipt missing after refresh"
}
}
}
private struct PushRelayChallengeResponse: Decodable {
var challengeId: String
var challenge: String
var expiresAtMs: Int64
}
private struct PushRelayRegisterSignedPayload: Encodable {
var challengeId: String
var installationId: String
var bundleId: String
var environment: String
var distribution: String
var gateway: PushRelayGatewayIdentity
var appVersion: String
var apnsToken: String
}
private struct PushRelayAppAttestPayload: Encodable {
var keyId: String
var attestationObject: String?
var assertion: String
var clientDataHash: String
var signedPayloadBase64: String
}
private struct PushRelayReceiptPayload: Encodable {
var base64: String
}
private struct PushRelayRegisterRequest: Encodable {
var challengeId: String
var installationId: String
var bundleId: String
var environment: String
var distribution: String
var gateway: PushRelayGatewayIdentity
var appVersion: String
var apnsToken: String
var appAttest: PushRelayAppAttestPayload
var receipt: PushRelayReceiptPayload
}
struct PushRelayRegisterResponse: Decodable {
var relayHandle: String
var sendGrant: String
var expiresAtMs: Int64?
var tokenSuffix: String?
var status: String
}
private struct RelayErrorResponse: Decodable {
var error: String?
var message: String?
var reason: String?
}
private final class PushRelayReceiptRefreshCoordinator: NSObject, SKRequestDelegate {
private var continuation: CheckedContinuation<Void, Error>?
private var activeRequest: SKReceiptRefreshRequest?
func refresh() async throws {
try await withCheckedThrowingContinuation { continuation in
self.continuation = continuation
let request = SKReceiptRefreshRequest()
self.activeRequest = request
request.delegate = self
request.start()
}
}
func requestDidFinish(_ request: SKRequest) {
self.continuation?.resume(returning: ())
self.continuation = nil
self.activeRequest = nil
}
func request(_ request: SKRequest, didFailWithError error: Error) {
self.continuation?.resume(throwing: error)
self.continuation = nil
self.activeRequest = nil
}
}
private struct PushRelayAppAttestProof {
var keyId: String
var attestationObject: String?
var assertion: String
var clientDataHash: String
var signedPayloadBase64: String
}
private final class PushRelayAppAttestService {
func createProof(challenge: String, signedPayload: Data) async throws -> PushRelayAppAttestProof {
let service = DCAppAttestService.shared
guard service.isSupported else {
throw PushRelayError.unsupportedAppAttest
}
let keyID = try await self.loadOrCreateKeyID(using: service)
let attestationObject = try await self.attestKeyIfNeeded(
service: service,
keyID: keyID,
challenge: challenge)
let signedPayloadHash = Data(SHA256.hash(data: signedPayload))
let assertion = try await self.generateAssertion(
service: service,
keyID: keyID,
signedPayloadHash: signedPayloadHash)
return PushRelayAppAttestProof(
keyId: keyID,
attestationObject: attestationObject,
assertion: assertion.base64EncodedString(),
clientDataHash: Self.base64URL(signedPayloadHash),
signedPayloadBase64: signedPayload.base64EncodedString())
}
private func loadOrCreateKeyID(using service: DCAppAttestService) async throws -> String {
if let existing = PushRelayRegistrationStore.loadAppAttestKeyID(), !existing.isEmpty {
return existing
}
let keyID = try await service.generateKey()
_ = PushRelayRegistrationStore.saveAppAttestKeyID(keyID)
return keyID
}
private func attestKeyIfNeeded(
service: DCAppAttestService,
keyID: String,
challenge: String)
async throws -> String? {
if PushRelayRegistrationStore.loadAttestedKeyID() == keyID {
return nil
}
let challengeData = Data(challenge.utf8)
let clientDataHash = Data(SHA256.hash(data: challengeData))
let attestation = try await service.attestKey(keyID, clientDataHash: clientDataHash)
// Apple treats App Attest key attestation as a one-time operation. Save the
// attested marker immediately so later receipt/network failures do not cause a
// permanently broken re-attestation loop on the same key.
_ = PushRelayRegistrationStore.saveAttestedKeyID(keyID)
return attestation.base64EncodedString()
}
private func generateAssertion(
service: DCAppAttestService,
keyID: String,
signedPayloadHash: Data)
async throws -> Data {
do {
return try await service.generateAssertion(keyID, clientDataHash: signedPayloadHash)
} catch {
_ = PushRelayRegistrationStore.clearAppAttestKeyID()
_ = PushRelayRegistrationStore.clearAttestedKeyID()
throw error
}
}
private static func base64URL(_ data: Data) -> String {
data.base64EncodedString()
.replacingOccurrences(of: "+", with: "-")
.replacingOccurrences(of: "/", with: "_")
.replacingOccurrences(of: "=", with: "")
}
}
private final class PushRelayReceiptProvider {
func loadReceiptBase64() async throws -> String {
if let receipt = self.readReceiptData() {
return receipt.base64EncodedString()
}
let refreshCoordinator = PushRelayReceiptRefreshCoordinator()
try await refreshCoordinator.refresh()
if let refreshed = self.readReceiptData() {
return refreshed.base64EncodedString()
}
throw PushRelayError.missingReceipt
}
private func readReceiptData() -> Data? {
guard let url = Bundle.main.appStoreReceiptURL else { return nil }
guard let data = try? Data(contentsOf: url), !data.isEmpty else { return nil }
return data
}
}
// The client is constructed once and used behind PushRegistrationManager actor isolation.
final class PushRelayClient: @unchecked Sendable {
private let baseURL: URL
private let session: URLSession
private let jsonDecoder = JSONDecoder()
private let jsonEncoder = JSONEncoder()
private let appAttest = PushRelayAppAttestService()
private let receiptProvider = PushRelayReceiptProvider()
init(baseURL: URL, session: URLSession = .shared) {
self.baseURL = baseURL
self.session = session
}
var normalizedBaseURLString: String {
Self.normalizeBaseURLString(self.baseURL)
}
func register(
installationId: String,
bundleId: String,
appVersion: String,
environment: PushAPNsEnvironment,
distribution: PushDistributionMode,
apnsTokenHex: String,
gatewayIdentity: PushRelayGatewayIdentity)
async throws -> PushRelayRegisterResponse {
let challenge = try await self.fetchChallenge()
let signedPayload = PushRelayRegisterSignedPayload(
challengeId: challenge.challengeId,
installationId: installationId,
bundleId: bundleId,
environment: environment.rawValue,
distribution: distribution.rawValue,
gateway: gatewayIdentity,
appVersion: appVersion,
apnsToken: apnsTokenHex)
let signedPayloadData = try self.jsonEncoder.encode(signedPayload)
let appAttest = try await self.appAttest.createProof(
challenge: challenge.challenge,
signedPayload: signedPayloadData)
let receiptBase64 = try await self.receiptProvider.loadReceiptBase64()
let requestBody = PushRelayRegisterRequest(
challengeId: signedPayload.challengeId,
installationId: signedPayload.installationId,
bundleId: signedPayload.bundleId,
environment: signedPayload.environment,
distribution: signedPayload.distribution,
gateway: signedPayload.gateway,
appVersion: signedPayload.appVersion,
apnsToken: signedPayload.apnsToken,
appAttest: PushRelayAppAttestPayload(
keyId: appAttest.keyId,
attestationObject: appAttest.attestationObject,
assertion: appAttest.assertion,
clientDataHash: appAttest.clientDataHash,
signedPayloadBase64: appAttest.signedPayloadBase64),
receipt: PushRelayReceiptPayload(base64: receiptBase64))
let endpoint = self.baseURL.appending(path: "v1/push/register")
var request = URLRequest(url: endpoint)
request.httpMethod = "POST"
request.timeoutInterval = 20
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = try self.jsonEncoder.encode(requestBody)
let (data, response) = try await self.session.data(for: request)
let status = Self.statusCode(from: response)
guard (200..<300).contains(status) else {
if status == 401 {
// If the relay rejects registration, drop local App Attest state so the next
// attempt re-attests instead of getting stuck without an attestation object.
_ = PushRelayRegistrationStore.clearAppAttestKeyID()
_ = PushRelayRegistrationStore.clearAttestedKeyID()
}
throw PushRelayError.requestFailed(
status: status,
message: Self.decodeErrorMessage(data: data))
}
let decoded = try self.decode(PushRelayRegisterResponse.self, from: data)
return decoded
}
private func fetchChallenge() async throws -> PushRelayChallengeResponse {
let endpoint = self.baseURL.appending(path: "v1/push/challenge")
var request = URLRequest(url: endpoint)
request.httpMethod = "POST"
request.timeoutInterval = 10
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
request.httpBody = Data("{}".utf8)
let (data, response) = try await self.session.data(for: request)
let status = Self.statusCode(from: response)
guard (200..<300).contains(status) else {
throw PushRelayError.requestFailed(
status: status,
message: Self.decodeErrorMessage(data: data))
}
return try self.decode(PushRelayChallengeResponse.self, from: data)
}
private func decode<T: Decodable>(_ type: T.Type, from data: Data) throws -> T {
do {
return try self.jsonDecoder.decode(type, from: data)
} catch {
throw PushRelayError.invalidResponse(error.localizedDescription)
}
}
private static func statusCode(from response: URLResponse) -> Int {
(response as? HTTPURLResponse)?.statusCode ?? 0
}
private static func normalizeBaseURLString(_ url: URL) -> String {
var absolute = url.absoluteString
while absolute.hasSuffix("/") {
absolute.removeLast()
}
return absolute
}
private static func decodeErrorMessage(data: Data) -> String {
if let decoded = try? JSONDecoder().decode(RelayErrorResponse.self, from: data) {
let message = decoded.message ?? decoded.reason ?? decoded.error ?? ""
if !message.isEmpty {
return message
}
}
let raw = String(data: data, encoding: .utf8)?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
return raw.isEmpty ? "unknown relay error" : raw
}
}
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