.

Sources/AgentRequestParser/main.swift

@@ -6,17 +6,37 @@ private let logger = Logger(subsystem: "com.maxgoedjen.secretive.secretagent.Age
 
 func handleRequest(_ request: XPCListener.IncomingSessionRequest) -> XPCListener.IncomingSessionRequest.Decision {
     logger.log("Parser received inbound request")
-    return request.accept { message in
+    return request.accept { xpcDictionary in
+        xpcDictionary.handoffReply(to: .global(qos: .userInteractive)) {
             logger.log("Parser accepted inbound request")
             do {
-            let result = try SSHAgentInputParser().parse(data: message)
+                let parser = SSHAgentInputParser()
+                let result = try parser.parse(data: xpcDictionary.decode(as: Data.self))
                 logger.log("Parser parsed message as type \(result.debugDescription)")
-            return result
-        } catch {
+                xpcDictionary.reply(result)
+            } catch let error as SSHAgentInputParser.AgentParsingError {
                 logger.error("Parser failed with error \(error)")
-            return nil
+                xpcDictionary.reply(error)
+            } catch {
+                // This should never actually happen because SSHAgentInputParser is a typed thrower, but the type system doesn't seem to know that across framework boundaries?
+                logger.error("Parser failed with unknown error \(error)")
             }
         }
+    }
+}
+
+public struct WrappedError<Wrapped: Codable & Error>: Codable {
+
+    public struct DescriptionOnlyError: Error, Codable {
+        let localizedDescription: String
+    }
+
+    public let wrapped: Wrapped
+
+    public init(_ error: Wrapped) {
+       wrapped = error
+    }
+
 }
 
 do {

Sources/Packages/Sources/SecretAgentKit/Agent.swift

@@ -45,6 +45,8 @@ extension Agent {
                 response.append(SSHAgent.Response.agentSignResponse.data)
                 response.append(try await sign(data: context.dataToSign, keyBlob: context.keyBlob, provenance: provenance))
                 logger.debug("Agent returned \(SSHAgent.Response.agentSignResponse.debugDescription)")
+            case .unknown(let value):
+                logger.error("Agent received unknown request of type \(value).")
             default:
                 logger.debug("Agent received valid request of type \(request.debugDescription), but not currently supported.")
                 throw UnhandledRequestError()

Sources/Packages/Sources/SecretAgentKit/OpenSSHReader.swift

@@ -7,25 +7,25 @@ final class OpenSSHReader {
 
     /// Initialize the reader with an OpenSSH data payload.
     /// - Parameter data: The data to read.
-    public init(data: Data) {
+    init(data: Data) {
         remaining = Data(data)
     }
 
     /// Reads the next chunk of data from the playload.
     /// - Returns: The next chunk of data.
-    public func readNextChunk(convertEndianness: Bool = true) throws -> Data {
+    func readNextChunk(convertEndianness: Bool = true) throws(OpenSSHReaderError) -> Data {
         let littleEndianLength = try readNextBytes(as: UInt32.self)
         let length = convertEndianness ? Int(littleEndianLength.bigEndian) : Int(littleEndianLength)
-        guard remaining.count >= length else { throw EndOfData() }
+        guard remaining.count >= length else { throw .beyondBounds }
         let dataRange = 0..<length
         let ret = Data(remaining[dataRange])
         remaining.removeSubrange(dataRange)
         return ret
     }
 
-    public func readNextBytes<T>(as: T.Type) throws -> T {
+    func readNextBytes<T>(as: T.Type) throws(OpenSSHReaderError) -> T {
         let size = MemoryLayout<T>.size
-        guard remaining.count >= size else { throw EndOfData() }
+        guard remaining.count >= size else { throw .beyondBounds }
         let lengthRange = 0..<size
         let lengthChunk = remaining[lengthRange]
         remaining.removeSubrange(lengthRange)
@@ -33,10 +33,12 @@ final class OpenSSHReader {
     }
 
 
-    public func readNextChunkAsString() throws -> String {
+    func readNextChunkAsString() throws -> String {
         try String(decoding: readNextChunk(), as: UTF8.self)
     }
 
-    public struct EndOfData: Error {}
-
+}
+
+public enum OpenSSHReaderError: Error, Codable {
+    case beyondBounds
 }

Sources/Packages/Sources/SecretAgentKit/SSHAgentInputParser.swift

@@ -16,10 +16,10 @@ public struct SSHAgentInputParser: SSHAgentInputParserProtocol {
         
     }
 
-    public func parse(data: Data) throws -> SSHAgent.Request {
+    public func parse(data: Data) throws(AgentParsingError) -> SSHAgent.Request {
         logger.debug("Parsing new data")
         guard data.count > 4 else {
-            throw InvalidDataProvidedError()
+            throw .invalidData
         }
         let specifiedLength = (data[0..<4].bytes.unsafeLoad(as: UInt32.self).bigEndian) + 4
         let rawRequestInt = data[4]
@@ -29,7 +29,11 @@ public struct SSHAgentInputParser: SSHAgentInputParserProtocol {
         case SSHAgent.Request.requestIdentities.protocolID:
             return .requestIdentities
         case SSHAgent.Request.signRequest(.empty).protocolID:
+            do {
                 return .signRequest(try signatureRequestContext(from: body))
+            } catch {
+                throw .openSSHReader(error)
+            }
         case SSHAgent.Request.addIdentity.protocolID:
             return .addIdentity
         case SSHAgent.Request.removeIdentity.protocolID:
@@ -59,7 +63,7 @@ public struct SSHAgentInputParser: SSHAgentInputParserProtocol {
 
 extension SSHAgentInputParser {
 
-    func signatureRequestContext(from data: Data) throws -> SSHAgent.Request.SignatureRequestContext {
+    func signatureRequestContext(from data: Data) throws(OpenSSHReaderError) -> SSHAgent.Request.SignatureRequestContext {
         let reader = OpenSSHReader(data: data)
         let rawKeyBlob = try reader.readNextChunk()
         let keyBlob = certificatePublicKeyBlob(from: rawKeyBlob) ?? rawKeyBlob
@@ -95,8 +99,11 @@ extension SSHAgentInputParser {
 
 extension SSHAgentInputParser {
 
-    struct AgentUnknownRequestError: Error {}
-    struct AgentUnhandledRequestError: Error {}
-    struct InvalidDataProvidedError: Error {}
+    public enum AgentParsingError: Error, Codable {
+        case unknownRequest
+        case unhandledRequest
+        case invalidData
+        case openSSHReader(OpenSSHReaderError)
+    }
 
 }

Sources/SecretAgent/AppDelegate.swift

@@ -35,13 +35,6 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         logger.debug("SecretAgent finished launching")
         Task {
             let inputParser = try XPCAgentInputParser()
-            Task {
-                try? await Task.sleep(for: .seconds(1))
-                var len = (5 as UInt32).littleEndian
-                var raw = SSHAgent.Request.requestIdentities.protocolID
-                let data = Data(bytes: &len, count: MemoryLayout<UInt32>.size) + Data(bytes: &raw, count: MemoryLayout<UInt8>.size)
-                print(try? await inputParser.parse(data: data))
-            }
             for await session in socketController.sessions {
                 Task {
                     do {

Sources/SecretAgent/XPCInputParser.swift

@@ -1,6 +1,7 @@
 import Foundation
 import SecretAgentKit
 
+/// Delegates all agent input parsing to an XPC service which wraps OpenSSH
 public final class XPCAgentInputParser: SSHAgentInputParserProtocol {
 
     private let session: XPCSession
@@ -8,11 +9,15 @@ public final class XPCAgentInputParser: SSHAgentInputParserProtocol {
 
     public init() throws {
         if #available(macOS 26.0, *) {
-            session = try XPCSession(xpcService: "com.maxgoedjen.Secretive.AgentRequestParser", targetQueue: queue, options: .inactive, requirement: .isFromSameTeam())
+            session = try XPCSession(xpcService: "com.maxgoedjen.Secretive.AgentRequestParser", targetQueue: queue, requirement: .isFromSameTeam())
         } else {
-            session = try XPCSession(xpcService: "com.maxgoedjen.Secretive.AgentRequestParser", targetQueue: queue, options: .inactive)
+            session = try XPCSession(xpcService: "com.maxgoedjen.Secretive.AgentRequestParser", targetQueue: queue)
+        }
+        Task {
+            // Warm up the XPC endpoint.
+            _ = try? await parse(data: Data())
+
         }
-        try session.activate()
     }
 
     public func parse(data: Data) async throws -> SSHAgent.Request {
@@ -21,10 +26,12 @@ public final class XPCAgentInputParser: SSHAgentInputParserProtocol {
                 try session.send(data) { result in
                     switch result {
                     case .success(let result):
-                        do {
-                            continuation.resume(returning: try result.decode(as: SSHAgent.Request.self))
-                        } catch {
+                        if let result = try? result.decode(as: SSHAgent.Request.self) {
+                            continuation.resume(returning: result)
+                        } else if let error = try? result.decode(as: SSHAgentInputParser.AgentParsingError.self) {
                             continuation.resume(throwing: error)
+                        } else {
+                            continuation.resume(throwing: UnknownMessageError())
                         }
                     case .failure(let error):
                         continuation.resume(throwing: error)
@@ -40,4 +47,6 @@ public final class XPCAgentInputParser: SSHAgentInputParserProtocol {
         session.cancel(reason: "Done")
     }
 
+    struct UnknownMessageError: Error {}
+
 }