Use FileHandle for reading base64 secret key from file (#2615)

Fixes process substitution failing to work for providing the private key as file argument (#2605).

common_cli/secret.swift

@@ -45,3 +45,41 @@ func decodePrivateAndPublicKeys(secret: Data) -> (privateKey: Data, publicKey: D
     
     return (privateKey, publicKey)
 }
+
+enum DecodeSecretStringError : LocalizedError {
+    case unableToReadData
+    case unableToDecodeDataAsUTF8String
+    
+    public var errorDescription: String? {
+        switch self {
+        case .unableToReadData:
+            return "Unable to read EdDSA private key data"
+        case .unableToDecodeDataAsUTF8String:
+            return "Unable to read EdDSA private key data as UTF-8 string"
+        }
+    }
+}
+
+// Reads secret base64 string from a file
+func decodeSecretString(filePath: String) throws -> String {
+    let privateKeyString: String
+    if #available(macOS 10.15.4, *) {
+        // Prefer to use FileHandle which supports process substitution:
+        // https://github.com/sparkle-project/Sparkle/issues/2605
+        let fileHandle = try FileHandle(forReadingFrom: URL(fileURLWithPath: filePath))
+        
+        guard let data = try fileHandle.readToEnd() else {
+            throw DecodeSecretStringError.unableToReadData
+        }
+        
+        guard let decodedPrivateKeyString = String(data: data, encoding: .utf8) else {
+            throw DecodeSecretStringError.unableToDecodeDataAsUTF8String
+        }
+        
+        privateKeyString = decodedPrivateKeyString
+    } else {
+        privateKeyString = try String(contentsOf: URL(fileURLWithPath: filePath))
+    }
+    
+    return privateKeyString.trimmingCharacters(in: .whitespacesAndNewlines)
+}

generate_appcast/main.swift

@@ -285,19 +285,22 @@ struct GenerateAppcast: ParsableCommand {
             allowNewPrivateKey = false
         } else if let privateEdKeyPath = privateEdKeyPath {
             do {
-                let privateKeyString: String
                 if privateEdKeyPath == "-" && !FileManager.default.fileExists(atPath: privateEdKeyPath) {
                     if let line = readLine(strippingNewline: true) {
-                        privateKeyString = line
+                        privateEdKeyString = line
                     } else {
                         print("Unable to read EdDSA private key from standard input")
                         throw ExitCode(1)
                     }
                 } else {
-                    privateKeyString = try String(contentsOf: URL(fileURLWithPath: privateEdKeyPath))
+                    do {
+                        privateEdKeyString = try decodeSecretString(filePath: privateEdKeyPath)
+                    } catch {
+                        print(error.localizedDescription)
+                        throw ExitCode(1)
+                    }
                 }
                 
-                privateEdKeyString = privateKeyString
                 allowNewPrivateKey = true
             } catch {
                 print("Unable to load EdDSA private key from", privateEdKeyPath, "\n", error)

generate_keys/main.swift

@@ -235,12 +235,12 @@ struct GenerateKeys: ParsableCommand {
             let secretBase64File = importedPrivateKeyFile
             let secretBase64: String
             do {
-                secretBase64 = try String(contentsOfFile: secretBase64File)
+                secretBase64 = try decodeSecretString(filePath: secretBase64File)
             } catch {
-                failure("Failed to read private-key-file: \(error)")
+                failure("Failed to read private-key-file: \(error.localizedDescription)")
             }
             
-            guard let secret = Data(base64Encoded: secretBase64.trimmingCharacters(in: .whitespacesAndNewlines), options: .init()) else {
+            guard let secret = Data(base64Encoded: secretBase64, options: .init()) else {
                 failure("Failed to decode base64 encoded key data from: \(secretBase64)")
             }
             

sign_update/main.swift

@@ -61,13 +61,13 @@ func findKeys(inFile secretFile: String) throws -> (Data, Data) {
             throw ExitCode(1)
         }
     } else {
-        secretString = try String(contentsOfFile: secretFile)
+        secretString = try decodeSecretString(filePath: secretFile)
     }
     return try findKeys(inString: secretString, allowNewFormat: true)
 }
 
 func findKeys(inString secretBase64String: String, allowNewFormat: Bool) throws -> (Data, Data) {
-    guard let secret = Data(base64Encoded: secretBase64String.trimmingCharacters(in: .whitespacesAndNewlines), options: .init()) else {
+    guard let secret = Data(base64Encoded: secretBase64String, options: .init()) else {
         print("ERROR! Failed to decode base64 encoded key data from: \(secretBase64String)")
         throw ExitCode.failure
     }
@@ -141,7 +141,7 @@ struct SignUpdate: ParsableCommand {
     func run() throws {
         let (priv, pub): (Data, Data)
         
-        if let privateKey = privateKey {
+        if let privateKey = privateKey?.trimmingCharacters(in: .whitespacesAndNewlines) {
             fputs("Warning: The -s option for passing the private EdDSA key is insecure and deprecated. Please see its help usage for more information.\n", stderr)
             
             (priv, pub) = try findKeys(inString: privateKey, allowNewFormat: false)