Validate custom TART_HOME and provide a human-friendly error message (#1138)

* Validate custom TART_HOME and provide a human-friendly error message

* Safer way to calculate "descendingURLs"

Sources/tart/Commands/Clone.swift

@@ -45,8 +45,8 @@ struct Clone: AsyncParsableCommand {
   }
 
   func run() async throws {
-    let ociStorage = VMStorageOCI()
-    let localStorage = VMStorageLocal()
+    let ociStorage = try VMStorageOCI()
+    let localStorage = try VMStorageLocal()
 
     if let remoteName = try? RemoteName(sourceName), !ociStorage.exists(remoteName) {
       // Pull the VM in case it's OCI-based and doesn't exist locally yet

Sources/tart/Commands/Import.swift

@@ -17,7 +17,7 @@ struct Import: AsyncParsableCommand {
   }
 
   func run() async throws {
-    let localStorage = VMStorageLocal()
+    let localStorage = try VMStorageLocal()
 
     // Create a temporary VM directory to which we will load the export file
     let tmpVMDir = try VMDirectory.temporary()

Sources/tart/Commands/Prune.swift

@@ -53,9 +53,9 @@ struct Prune: AsyncParsableCommand {
 
     switch entries {
     case "caches":
-      prunableStorages = [VMStorageOCI(), try IPSWCache()]
+      prunableStorages = [try VMStorageOCI(), try IPSWCache()]
     case "vms":
-      prunableStorages = [VMStorageLocal()]
+      prunableStorages = [try VMStorageLocal()]
     default:
       throw ValidationError("unsupported --entries value, please specify either \"caches\" or \"vms\"")
     }
@@ -152,7 +152,7 @@ struct Prune: AsyncParsableCommand {
     let transaction = SentrySDK.startTransaction(name: "Pruning cache", operation: "prune", bindToScope: true)
     defer { transaction.finish() }
 
-    let prunableStorages: [PrunableStorage] = [VMStorageOCI(), try IPSWCache()]
+    let prunableStorages: [PrunableStorage] = [try VMStorageOCI(), try IPSWCache()]
     let prunables: [Prunable] = try prunableStorages
       .flatMap { try $0.prunables() }
       .sorted { try $0.accessDate() < $1.accessDate() }

Sources/tart/Commands/Pull.swift

@@ -35,7 +35,7 @@ struct Pull: AsyncParsableCommand {
   func run() async throws {
     // Be more liberal when accepting local image as argument,
     // see https://github.com/cirruslabs/tart/issues/36
-    if VMStorageLocal().exists(remoteName) {
+    if try VMStorageLocal().exists(remoteName) {
       print("\"\(remoteName)\" is a local image, nothing to pull here!")
 
       return

Sources/tart/Commands/Push.swift

@@ -39,7 +39,7 @@ struct Push: AsyncParsableCommand {
   var populateCache: Bool = false
 
   func run() async throws {
-    let ociStorage = VMStorageOCI()
+    let ociStorage = try VMStorageOCI()
     let localVMDir = try VMStorageHelper.open(localName)
     let lock = try localVMDir.lock()
     if try !lock.trylock() {

Sources/tart/Commands/Rename.swift

@@ -17,7 +17,7 @@ struct Rename: AsyncParsableCommand {
   }
 
   func run() async throws {
-    let localStorage = VMStorageLocal()
+    let localStorage = try VMStorageLocal()
 
     if !localStorage.exists(name) {
       throw ValidationError("failed to rename a non-existent local VM: \(name)")

Sources/tart/Commands/Run.swift

@@ -301,7 +301,7 @@ struct Run: AsyncParsableCommand {
       }
     }
 
-    let localStorage = VMStorageLocal()
+    let localStorage = try VMStorageLocal()
     let vmDir = try localStorage.open(name)
     if try vmDir.state() == .Suspended {
       suspendable = true
@@ -334,7 +334,7 @@ struct Run: AsyncParsableCommand {
 
   @MainActor
   func run() async throws {
-    let localStorage = VMStorageLocal()
+    let localStorage = try VMStorageLocal()
     let vmDir = try localStorage.open(name)
 
     // Validate disk format support

Sources/tart/Config.swift

@@ -9,7 +9,8 @@ struct Config {
     var tartHomeDir: URL
 
     if let customTartHome = ProcessInfo.processInfo.environment["TART_HOME"] {
-      tartHomeDir = URL(fileURLWithPath: customTartHome)
+      tartHomeDir = URL(fileURLWithPath: customTartHome, isDirectory: true)
+      try Self.validateTartHome(url: tartHomeDir)
     } else {
       tartHomeDir = FileManager.default
         .homeDirectoryForCurrentUser
@@ -49,4 +50,24 @@ struct Config {
   static func jsonDecoder() -> JSONDecoder {
     JSONDecoder()
   }
+
+  private static func validateTartHome(url: URL) throws {
+    let urlComponents = url.pathComponents
+
+    let descendingURLs = urlComponents.indices.map { i in
+      URL(fileURLWithPath: urlComponents[0...i].joined(separator: "/"))
+    }
+
+    for descendingURL in descendingURLs {
+      if FileManager.default.fileExists(atPath: descendingURL.path) {
+        continue
+      }
+
+      do {
+        try FileManager.default.createDirectory(at: descendingURL, withIntermediateDirectories: false)
+      } catch {
+        throw RuntimeError.Generic("TART_HOME is invalid: \(descendingURL.path) does not exist, yet we can't create it: \(error.localizedDescription)")
+      }
+    }
+  }
 }

Sources/tart/Root.swift

@@ -92,7 +92,7 @@ struct Root: AsyncParsableCommand {
         do {
           try Config().gc()
         } catch {
-          fputs("Failed to perform garbage collection!\n\(error)\n", stderr)
+          fputs("Failed to perform garbage collection: \(error)\n", stderr)
         }
       }
 

Sources/tart/VMStorageLocal.swift

@@ -1,7 +1,11 @@
 import Foundation
 
 class VMStorageLocal: PrunableStorage {
-  let baseURL: URL = try! Config().tartHomeDir.appendingPathComponent("vms", isDirectory: true)
+  let baseURL: URL
+
+  init() throws {
+    baseURL = try Config().tartHomeDir.appendingPathComponent("vms", isDirectory: true)
+  }
 
   private func vmURL(_ name: String) -> URL {
     baseURL.appendingPathComponent(name, isDirectory: true)

Sources/tart/VMStorageOCI.swift

@@ -3,7 +3,11 @@ import Sentry
 import Retry
 
 class VMStorageOCI: PrunableStorage {
-  let baseURL = try! Config().tartCacheDir.appendingPathComponent("OCIs", isDirectory: true)
+  let baseURL: URL
+
+  init() throws {
+    baseURL = try Config().tartCacheDir.appendingPathComponent("OCIs", isDirectory: true)
+  }
 
   private func vmURL(_ name: RemoteName) -> URL {
     baseURL.appendingRemoteName(name)