Support Docker Helpers (#205)

Fixes #167

Sources/tart/Commands/Login.swift

@@ -45,7 +45,7 @@ struct Login: AsyncParsableCommand {
 
       do {
         let registry = try Registry(host: host, namespace: "", insecure: insecure,
-          credentialsProvider: credentialsProvider)
+          credentialsProviders: [credentialsProvider])
         try await registry.ping()
       } catch {
         print("invalid credentials: \(error)")

Sources/tart/Credentials/HelperProgramCredentialsProvider.swift

@@ -0,0 +1,63 @@
+import Foundation
+
+class HelperProgramCredentialsProvider: CredentialsProvider {
+  func retrieve(host: String) throws -> (String, String)? {
+    let dockerConfigURL = FileManager.default.homeDirectoryForCurrentUser.appendingPathComponent(".docker").appendingPathComponent("config.json")
+    if !FileManager.default.fileExists(atPath: dockerConfigURL.path) {
+      return nil
+    }
+    let config = try JSONDecoder().decode(DockerConfig.self, from: Data(contentsOf: dockerConfigURL))
+
+    if let helperProgram = config.credHelpers[host] {
+      return try executeHelper(binaryName: "docker-credential-\(helperProgram)", host: host)
+    }
+
+    return nil
+  }
+
+  private func executeHelper(binaryName: String, host: String) throws -> (String, String)? {
+    guard let executableURL = resolveBinaryPath(binaryName) else {
+      throw CredentialsProviderError.Failed(message: "\(binaryName) not found in PATH")
+    }
+
+    let process = Process.init()
+    process.executableURL = executableURL
+    process.arguments = ["get"]
+
+    let outPipe = Pipe()
+    let inPipe = Pipe()
+
+    process.standardOutput = outPipe
+    process.standardError = outPipe
+    process.standardInput = inPipe
+
+    process.launch()
+
+    inPipe.fileHandleForWriting.write("\(host)\n".data(using: .utf8)!)
+    inPipe.fileHandleForWriting.closeFile()
+
+    process.waitUntilExit()
+
+    if !(process.terminationReason == .exit && process.terminationStatus == 0) {
+      throw CredentialsProviderError.Failed(message: "Docker helper failed!")
+    }
+
+    let getOutput = try JSONDecoder().decode(
+      DockerGetOutput.self, from: outPipe.fileHandleForReading.readDataToEndOfFile()
+    )
+    return (getOutput.Username, getOutput.Secret)
+  }
+
+  func store(host: String, user: String, password: String) throws {
+    throw CredentialsProviderError.Failed(message: "Docker helpers don't support storing!")
+  }
+}
+
+struct DockerConfig: Codable {
+  var credHelpers: Dictionary<String, String> = Dictionary()
+}
+
+struct DockerGetOutput: Codable {
+  var Username: String
+  var Secret: String
+}

Sources/tart/OCI/Registry.swift

@@ -88,29 +88,29 @@ class Registry {
 
   let baseURL: URL
   let namespace: String
-  let credentialsProvider: CredentialsProvider
+  let credentialsProviders: [CredentialsProvider]
 
   var currentAuthToken: Authentication? = nil
 
   init(urlComponents: URLComponents,
        namespace: String,
-       credentialsProvider: CredentialsProvider = KeychainCredentialsProvider()
+       credentialsProviders: [CredentialsProvider] = [HelperProgramCredentialsProvider(), KeychainCredentialsProvider()]
   ) throws {
     baseURL = urlComponents.url!
     self.namespace = namespace
-    self.credentialsProvider = credentialsProvider
+    self.credentialsProviders = credentialsProviders
   }
 
   convenience init(
     host: String,
     namespace: String,
     insecure: Bool = false,
-    credentialsProvider: CredentialsProvider = KeychainCredentialsProvider()
+    credentialsProviders: [CredentialsProvider] = [HelperProgramCredentialsProvider(), KeychainCredentialsProvider()]
   ) throws {
     let proto = insecure ? "http" : "https"
     let baseURLComponents = URLComponents(string: proto + "://" + host + "/v2/")!
 
-    try self.init(urlComponents: baseURLComponents, namespace: namespace, credentialsProvider: credentialsProvider)
+    try self.init(urlComponents: baseURLComponents, namespace: namespace, credentialsProviders: credentialsProviders)
   }
 
   func ping() async throws {
@@ -303,7 +303,7 @@ class Registry {
     let wwwAuthenticate = try WWWAuthenticate(rawHeaderValue: wwwAuthenticateRaw)
 
     if wwwAuthenticate.scheme == "Basic" {
-      if let (user, password) = try credentialsProvider.retrieve(host: baseURL.host!) {
+      if let (user, password) = try lookupCredentials(host: baseURL.host!) {
         currentAuthToken = BasicAuthentication(user: user, password: password)
       }
 
@@ -340,7 +340,7 @@ class Registry {
 
     var headers: Dictionary<String, String> = Dictionary()
 
-    if let (user, password) = try credentialsProvider.retrieve(host: baseURL.host!) {
+    if let (user, password) = try lookupCredentials(host: baseURL.host!) {
       let encodedCredentials = "\(user):\(password)".data(using: .utf8)?.base64EncodedString()
       headers["Authorization"] = "Basic \(encodedCredentials!)"
     }
@@ -356,6 +356,15 @@ class Registry {
     currentAuthToken = try TokenResponse.parse(fromData: bodyData)
   }
 
+  private func lookupCredentials(host: String) throws -> (String, String)? {
+    for provider in credentialsProviders {
+      if let (user, password) = try provider.retrieve(host: host) {
+        return (user, password)
+      }
+    }
+    return nil
+  }
+
   private func authAwareRequest(request: HTTPClientRequest) async throws -> HTTPClientResponse {
     var request = request
 

Sources/tart/Softnet.swift

@@ -12,7 +12,7 @@ class Softnet {
   init(vmMACAddress: String) throws {
     let binaryName = "softnet"
 
-    guard let executableURL = Self.resolveBinaryPath(binaryName) else {
+    guard let executableURL = resolveBinaryPath(binaryName) else {
       throw SoftnetError.InitializationFailed(why: "\(binaryName) not found in PATH")
     }
 
@@ -43,23 +43,6 @@ class Softnet {
     process.waitUntilExit()
   }
 
-  private static func resolveBinaryPath(_ name: String) -> URL? {
-    guard let path = ProcessInfo.processInfo.environment["PATH"] else {
-      return nil
-    }
-
-    for pathComponent in path.split(separator: ":") {
-      let url = URL(fileURLWithPath: String(pathComponent))
-              .appendingPathComponent(name, isDirectory: false)
-
-      if FileManager.default.fileExists(atPath: url.path) {
-        return url
-      }
-    }
-
-    return nil
-  }
-
   private func setSocketBuffers(_ fd: Int32, _ sizeBytes: Int) throws {
     var option_value = sizeBytes
     let option_len = socklen_t(MemoryLayout<Int>.size)

Sources/tart/Utils.swift

@@ -5,3 +5,20 @@ extension Collection {
     indices.contains(index) ? self[index] : nil
   }
 }
+
+func resolveBinaryPath(_ name: String) -> URL? {
+  guard let path = ProcessInfo.processInfo.environment["PATH"] else {
+    return nil
+  }
+
+  for pathComponent in path.split(separator: ":") {
+    let url = URL(fileURLWithPath: String(pathComponent))
+            .appendingPathComponent(name, isDirectory: false)
+
+    if FileManager.default.fileExists(atPath: url.path) {
+      return url
+    }
+  }
+
+  return nil
+}