349 lines
18 KiB
Swift
349 lines
18 KiB
Swift
import CryptoSwift
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import PromiseKit
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/// See the "Onion Requests" section of [The Session Whitepaper](https://arxiv.org/pdf/2002.04609.pdf) for more information.
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public enum OnionRequestAPI {
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public static var guardSnodes: Set<Snode> = []
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public static var paths: [Path] = [] // Not a set to ensure we consistently show the same path to the user
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private static var snodePool: Set<Snode> {
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let unreliableSnodes = Set(SnodeAPI.snodeFailureCount.keys)
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return SnodeAPI.snodePool.subtracting(unreliableSnodes)
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}
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// MARK: Settings
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/// The number of snodes (including the guard snode) in a path.
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private static let pathSize: UInt = 3
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public static let pathCount: UInt = 2
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private static var guardSnodeCount: UInt { return pathCount } // One per path
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// MARK: Destination
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internal enum Destination {
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case snode(Snode)
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case server(host: String, x25519PublicKey: String)
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}
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// MARK: Error
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public enum Error : LocalizedError {
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case httpRequestFailedAtDestination(statusCode: UInt, json: JSON)
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case insufficientSnodes
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case invalidURL
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case missingSnodeVersion
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case randomDataGenerationFailed
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case snodePublicKeySetMissing
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case unsupportedSnodeVersion(String)
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public var errorDescription: String? {
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switch self {
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case .httpRequestFailedAtDestination(let statusCode): return "HTTP request failed at destination with status code: \(statusCode)."
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case .insufficientSnodes: return "Couldn't find enough snodes to build a path."
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case .invalidURL: return "Invalid URL"
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case .missingSnodeVersion: return "Missing snode version."
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case .randomDataGenerationFailed: return "Couldn't generate random data."
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case .snodePublicKeySetMissing: return "Missing snode public key set."
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case .unsupportedSnodeVersion(let version): return "Unsupported snode version: \(version)."
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}
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}
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}
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// MARK: Path
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public typealias Path = [Snode]
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// MARK: Onion Building Result
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private typealias OnionBuildingResult = (guardSnode: Snode, finalEncryptionResult: EncryptionResult, destinationSymmetricKey: Data)
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// MARK: Private API
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/// Tests the given snode. The returned promise errors out if the snode is faulty; the promise is fulfilled otherwise.
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private static func testSnode(_ snode: Snode) -> Promise<Void> {
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let (promise, seal) = Promise<Void>.pending()
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DispatchQueue.global(qos: .userInitiated).async {
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let url = "\(snode.address):\(snode.port)/get_stats/v1"
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let timeout: TimeInterval = 3 // Use a shorter timeout for testing
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HTTP.execute(.get, url, timeout: timeout).done2 { rawResponse in
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guard let json = rawResponse as? JSON, let version = json["version"] as? String else { return seal.reject(Error.missingSnodeVersion) }
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if version >= "2.0.0" {
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seal.fulfill(())
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} else {
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print("[Loki] [Onion Request API] Unsupported snode version: \(version).")
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seal.reject(Error.unsupportedSnodeVersion(version))
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}
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}.catch2 { error in
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seal.reject(error)
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}
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}
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return promise
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}
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/// Finds `guardSnodeCount` guard snodes to use for path building. The returned promise errors out with `Error.insufficientSnodes`
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/// if not enough (reliable) snodes are available.
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private static func getGuardSnodes() -> Promise<Set<Snode>> {
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if guardSnodes.count >= guardSnodeCount {
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return Promise<Set<Snode>> { $0.fulfill(guardSnodes) }
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} else {
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print("[Loki] [Onion Request API] Populating guard snode cache.")
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return SnodeAPI.getRandomSnode().then2 { _ -> Promise<Set<Snode>> in // Just used to populate the snode pool
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var unusedSnodes = snodePool // Sync on LokiAPI.workQueue
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guard unusedSnodes.count >= guardSnodeCount else { throw Error.insufficientSnodes }
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func getGuardSnode() -> Promise<Snode> {
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// randomElement() uses the system's default random generator, which is cryptographically secure
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guard let candidate = unusedSnodes.randomElement() else { return Promise<Snode> { $0.reject(Error.insufficientSnodes) } }
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unusedSnodes.remove(candidate) // All used snodes should be unique
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print("[Loki] [Onion Request API] Testing guard snode: \(candidate).")
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// Loop until a reliable guard snode is found
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return testSnode(candidate).map2 { candidate }.recover(on: DispatchQueue.main) { _ in
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withDelay(0.25, completionQueue: SnodeAPI.workQueue) { getGuardSnode() }
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}
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}
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let promises = (0..<guardSnodeCount).map { _ in getGuardSnode() }
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return when(fulfilled: promises).map2 { guardSnodes in
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let guardSnodesAsSet = Set(guardSnodes)
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OnionRequestAPI.guardSnodes = guardSnodesAsSet
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return guardSnodesAsSet
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}
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}
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}
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}
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/// Builds and returns `pathCount` paths. The returned promise errors out with `Error.insufficientSnodes`
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/// if not enough (reliable) snodes are available.
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private static func buildPaths() -> Promise<[Path]> {
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print("[Loki] [Onion Request API] Building onion request paths.")
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DispatchQueue.main.async {
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NotificationCenter.default.post(name: .buildingPaths, object: nil)
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}
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return SnodeAPI.getRandomSnode().then2 { _ -> Promise<[Path]> in // Just used to populate the snode pool
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return getGuardSnodes().map2 { guardSnodes -> [Path] in
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var unusedSnodes = snodePool.subtracting(guardSnodes)
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let pathSnodeCount = guardSnodeCount * pathSize - guardSnodeCount
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guard unusedSnodes.count >= pathSnodeCount else { throw Error.insufficientSnodes }
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// Don't test path snodes as this would reveal the user's IP to them
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return guardSnodes.map { guardSnode in
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let result = [ guardSnode ] + (0..<(pathSize - 1)).map { _ in
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// randomElement() uses the system's default random generator, which is cryptographically secure
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let pathSnode = unusedSnodes.randomElement()! // Safe because of the pathSnodeCount check above
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unusedSnodes.remove(pathSnode) // All used snodes should be unique
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return pathSnode
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}
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print("[Loki] [Onion Request API] Built new onion request path: \(result.prettifiedDescription).")
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return result
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}
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}.map2 { paths in
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OnionRequestAPI.paths = paths
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try! Storage.writeSync { transaction in
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print("[Loki] Persisting onion request paths to database.")
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OWSPrimaryStorage.shared().setOnionRequestPaths(paths, in: transaction)
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}
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DispatchQueue.main.async {
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NotificationCenter.default.post(name: .pathsBuilt, object: nil)
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}
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return paths
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}
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}
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}
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/// Returns a `Path` to be used for building an onion request. Builds new paths as needed.
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///
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/// - Note: Exposed for testing purposes.
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private static func getPath(excluding snode: Snode?) -> Promise<Path> {
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guard pathSize >= 1 else { preconditionFailure("Can't build path of size zero.") }
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if paths.count < pathCount {
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let storage = OWSPrimaryStorage.shared()
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storage.dbReadConnection.read { transaction in
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paths = storage.getOnionRequestPaths(in: transaction)
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if paths.count >= pathCount {
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guardSnodes.formUnion([ paths[0][0], paths[1][0] ])
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}
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}
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}
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// randomElement() uses the system's default random generator, which is cryptographically secure
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if paths.count >= pathCount {
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return Promise<Path> { seal in
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if let snode = snode {
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seal.fulfill(paths.filter { !$0.contains(snode) }.randomElement()!)
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} else {
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seal.fulfill(paths.randomElement()!)
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}
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}
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} else {
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return buildPaths().map2 { paths in
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if let snode = snode {
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return paths.filter { !$0.contains(snode) }.randomElement()!
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} else {
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return paths.randomElement()!
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}
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}
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}
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}
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private static func dropAllPaths() {
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paths.removeAll()
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try! Storage.writeSync { transaction in
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OWSPrimaryStorage.shared().clearOnionRequestPaths(in: transaction)
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}
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}
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private static func dropGuardSnode(_ snode: Snode) {
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guardSnodes = guardSnodes.filter { $0 != snode }
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}
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/// Builds an onion around `payload` and returns the result.
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private static func buildOnion(around payload: JSON, targetedAt destination: Destination) -> Promise<OnionBuildingResult> {
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var guardSnode: Snode!
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var targetSnodeSymmetricKey: Data! // Needed by invoke(_:on:with:) to decrypt the response sent back by the destination
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var encryptionResult: EncryptionResult!
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var snodeToExclude: Snode?
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if case .snode(let snode) = destination { snodeToExclude = snode }
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return getPath(excluding: snodeToExclude).then2 { path -> Promise<EncryptionResult> in
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guardSnode = path.first!
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// Encrypt in reverse order, i.e. the destination first
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return encrypt(payload, for: destination).then2 { r -> Promise<EncryptionResult> in
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targetSnodeSymmetricKey = r.symmetricKey
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// Recursively encrypt the layers of the onion (again in reverse order)
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encryptionResult = r
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var path = path
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var rhs = destination
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func addLayer() -> Promise<EncryptionResult> {
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if path.isEmpty {
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return Promise<EncryptionResult> { $0.fulfill(encryptionResult) }
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} else {
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let lhs = Destination.snode(path.removeLast())
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return OnionRequestAPI.encryptHop(from: lhs, to: rhs, using: encryptionResult).then2 { r -> Promise<EncryptionResult> in
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encryptionResult = r
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rhs = lhs
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return addLayer()
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}
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}
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}
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return addLayer()
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}
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}.map2 { _ in (guardSnode, encryptionResult, targetSnodeSymmetricKey) }
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}
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// MARK: Internal API
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/// Sends an onion request to `snode`. Builds new paths as needed.
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internal static func sendOnionRequest(to snode: Snode, invoking method: Snode.Method, with parameters: JSON, associatedWith publicKey: String) -> Promise<JSON> {
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let payload: JSON = [ "method" : method.rawValue, "params" : parameters ]
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return sendOnionRequest(with: payload, to: Destination.snode(snode)).recover2 { error -> Promise<JSON> in
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guard case OnionRequestAPI.Error.httpRequestFailedAtDestination(let statusCode, let json) = error else { throw error }
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throw SnodeAPI.handleError(withStatusCode: statusCode, json: json, forSnode: snode, associatedWith: publicKey) ?? error
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}
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}
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/// Sends an onion request to `server`. Builds new paths as needed.
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internal static func sendOnionRequest(_ request: NSURLRequest, to server: String, using x25519PublicKey: String, isJSONRequired: Bool = true) -> Promise<JSON> {
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let rawHeaders = request.allHTTPHeaderFields ?? [:]
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var headers: JSON = rawHeaders.mapValues { value in
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switch value.lowercased() {
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case "true": return true
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case "false": return false
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default: return value
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}
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}
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guard let url = request.url?.absoluteString, let host = request.url?.host else { return Promise(error: Error.invalidURL) }
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var endpoint = ""
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if server.count < url.count {
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guard let serverEndIndex = url.range(of: server)?.upperBound else { return Promise(error: Error.invalidURL) }
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let endpointStartIndex = url.index(after: serverEndIndex)
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endpoint = String(url[endpointStartIndex..<url.endIndex])
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}
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let parametersAsString: String
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if let tsRequest = request as? TSRequest {
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headers["Content-Type"] = "application/json"
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let tsRequestParameters = tsRequest.parameters
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if !tsRequestParameters.isEmpty {
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guard let parameters = try? JSONSerialization.data(withJSONObject: tsRequestParameters, options: [ .fragmentsAllowed ]) else {
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return Promise(error: HTTP.Error.invalidJSON)
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}
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parametersAsString = String(bytes: parameters, encoding: .utf8) ?? "null"
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} else {
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parametersAsString = "null"
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}
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} else {
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headers["Content-Type"] = request.allHTTPHeaderFields!["Content-Type"]
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if let parametersAsInputStream = request.httpBodyStream, let parameters = try? Data(from: parametersAsInputStream) {
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parametersAsString = "{ \"fileUpload\" : \"\(String(data: parameters.base64EncodedData(), encoding: .utf8) ?? "null")\" }"
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} else {
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parametersAsString = "null"
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}
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}
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let payload: JSON = [
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"body" : parametersAsString,
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"endpoint": endpoint,
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"method" : request.httpMethod,
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"headers" : headers
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]
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let destination = Destination.server(host: host, x25519PublicKey: x25519PublicKey)
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return sendOnionRequest(with: payload, to: destination, isJSONRequired: isJSONRequired).recover2 { error -> Promise<JSON> in
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print("[Loki] [Onion Request API] Couldn't reach server: \(url) due to error: \(error).")
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throw error
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}
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}
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internal static func sendOnionRequest(with payload: JSON, to destination: Destination, isJSONRequired: Bool = true) -> Promise<JSON> {
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let (promise, seal) = Promise<JSON>.pending()
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var guardSnode: Snode!
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SnodeAPI.workQueue.async { // Avoid race conditions on `guardSnodes` and `paths`
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buildOnion(around: payload, targetedAt: destination).done2 { intermediate in
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guardSnode = intermediate.guardSnode
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let url = "\(guardSnode.address):\(guardSnode.port)/onion_req"
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let finalEncryptionResult = intermediate.finalEncryptionResult
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let onion = finalEncryptionResult.ciphertext
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let requestSizeLimit = Double(FileServerAPI.maxFileSize) / FileServerAPI.fileSizeORMultiplier
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if case Destination.server = destination, Double(onion.count) > 0.75 * requestSizeLimit {
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print("[Loki] Approaching request size limit: ~\(onion.count) bytes.")
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}
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let parameters: JSON = [
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"ciphertext" : onion.base64EncodedString(),
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"ephemeral_key" : finalEncryptionResult.ephemeralPublicKey.toHexString()
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]
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let destinationSymmetricKey = intermediate.destinationSymmetricKey
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HTTP.execute(.post, url, parameters: parameters).done2 { rawResponse in
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guard let json = rawResponse as? JSON, let base64EncodedIVAndCiphertext = json["result"] as? String,
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let ivAndCiphertext = Data(base64Encoded: base64EncodedIVAndCiphertext), ivAndCiphertext.count >= ivSize else { return seal.reject(HTTP.Error.invalidJSON) }
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let iv = ivAndCiphertext[0..<Int(ivSize)]
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let ciphertext = ivAndCiphertext[Int(ivSize)...]
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do {
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let gcm = GCM(iv: iv.bytes, tagLength: Int(gcmTagSize), mode: .combined)
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let aes = try AES(key: destinationSymmetricKey.bytes, blockMode: gcm, padding: .noPadding)
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let data = Data(try aes.decrypt(ciphertext.bytes))
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guard let json = try JSONSerialization.jsonObject(with: data, options: [ .fragmentsAllowed ]) as? JSON,
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let statusCode = json["status"] as? Int else { return seal.reject(HTTP.Error.invalidJSON) }
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if statusCode == 406 { // Clock out of sync
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print("[Loki] The user's clock is out of sync with the service node network.")
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seal.reject(SnodeAPI.SnodeAPIError.clockOutOfSync)
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} else if let bodyAsString = json["body"] as? String {
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let body: JSON
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if !isJSONRequired {
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body = [ "result" : bodyAsString ]
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} else {
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guard let bodyAsData = bodyAsString.data(using: .utf8),
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let b = try JSONSerialization.jsonObject(with: bodyAsData, options: [ .fragmentsAllowed ]) as? JSON else { return seal.reject(HTTP.Error.invalidJSON) }
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body = b
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}
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guard 200...299 ~= statusCode else { return seal.reject(Error.httpRequestFailedAtDestination(statusCode: UInt(statusCode), json: body)) }
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seal.fulfill(body)
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} else {
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guard 200...299 ~= statusCode else { return seal.reject(Error.httpRequestFailedAtDestination(statusCode: UInt(statusCode), json: json)) }
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seal.fulfill(json)
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}
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} catch {
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seal.reject(error)
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}
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}.catch2 { error in
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seal.reject(error)
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}
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}.catch2 { error in
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seal.reject(error)
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}
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}
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promise.catch2 { error in // Must be invoked on LokiAPI.workQueue
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guard case HTTP.Error.httpRequestFailed(_, _) = error else { return }
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dropAllPaths() // A snode in the path is bad; retry with a different path
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dropGuardSnode(guardSnode)
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}
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return promise
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}
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}
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