Merge nucleic/vivid-glass-urchin-xoym into main

Sources/RunnerHost/LocalNetworkPermission.swift

@@ -50,6 +50,8 @@ public enum LocalNetworkPermission {
         case probeProducedNoReport
         /// A subnet argument is not an IPv4 address or CIDR block.
         case invalidSubnet(String)
+        /// A child process could not be started or waited on.
+        case spawnFailed(command: String, code: Int32)
 
         public var description: String {
             switch self {
@@ -74,6 +76,8 @@ public enum LocalNetworkPermission {
                     entries it cannot parse, which would leave the allowlist looking configured \
                     while granting nothing.
                     """
+            case .spawnFailed(let command, let code):
+                return "could not run \(command): \(String(cString: strerror(code))) (\(code))"
             }
         }
     }
@@ -117,27 +121,15 @@ public enum LocalNetworkPermission {
 
         let commands = LocalNetworkPolicy.writeCommandLines(subnets: subnets)
 
-        for arguments in LocalNetworkPolicy.writeArguments(subnets: subnets) {
+        for (index, arguments) in LocalNetworkPolicy.writeArguments(subnets: subnets).enumerated() {
             let sudoArguments = (allowPasswordPrompt ? [] : ["-n"]) + ["/usr/bin/defaults"] + arguments
 
-            let process = Process()
-            process.executableURL = URL(fileURLWithPath: "/usr/bin/sudo")
-            process.arguments = sudoArguments
-            // Stdio is deliberately inherited rather than piped. sudo reads the
-            // password from /dev/tty and would work either way, but its prompt
-            // and any "not in the sudoers file" complaint belong in front of
-            // the operator, not captured and paraphrased.
-            try process.run()
-            process.waitUntilExit()
-
-            guard process.terminationStatus == 0 else {
-                let index = LocalNetworkPolicy.writeArguments(subnets: subnets)
-                    .firstIndex(of: arguments) ?? 0
+            let exitCode = try runInForeground("/usr/bin/sudo", sudoArguments)
+            guard exitCode == 0 else {
                 if !allowPasswordPrompt {
                     throw PermissionError.needsPassword(commands: commands)
                 }
-                throw PermissionError.writeFailed(
-                    command: commands[index], exitCode: process.terminationStatus)
+                throw PermissionError.writeFailed(command: commands[index], exitCode: exitCode)
             }
         }
 
@@ -147,11 +139,54 @@ public enum LocalNetworkPermission {
     /// Reboots the host. Only ever called from an explicit confirmation — the
     /// allowlist is read at boot, so nothing else makes it take effect.
     public static func reboot() throws {
-        let process = Process()
-        process.executableURL = URL(fileURLWithPath: "/usr/bin/sudo")
-        process.arguments = ["/sbin/shutdown", "-r", "now"]
-        try process.run()
-        process.waitUntilExit()
+        _ = try runInForeground("/usr/bin/sudo", ["/sbin/shutdown", "-r", "now"])
+    }
+
+    /// Runs a command with this process's stdio *and its process group*, and
+    /// returns its exit status.
+    ///
+    /// The process group is the whole reason this is not `Foundation.Process`.
+    /// `Process` starts the child as its own process-group leader, so for the
+    /// controlling terminal the child is a *background* job — and the terminal
+    /// driver defends itself against those. `sudo`'s `tcsetattr` to turn echo
+    /// off raises `SIGTTOU` and fails, so the password is typed in the clear;
+    /// its read of the tty raises `SIGTTIN`, so Return never reaches `sudo` and
+    /// the line editor just echoes a newline. Both symptoms, one cause.
+    ///
+    /// `posix_spawn` with no `POSIX_SPAWN_SETPGROUP` leaves the child in our
+    /// process group, which is the terminal's foreground group, so `sudo` gets
+    /// the terminal it expects. Stdio is inherited for the same reason it
+    /// always was: the prompt and any "not in the sudoers file" complaint
+    /// belong in front of the operator, not captured and paraphrased.
+    private static func runInForeground(_ executable: String, _ arguments: [String]) throws -> Int32
+    {
+        var argv: [UnsafeMutablePointer<CChar>?] = ([executable] + arguments).map { strdup($0) }
+        argv.append(nil)
+        var envp: [UnsafeMutablePointer<CChar>?] = ProcessInfo.processInfo.environment.map {
+            strdup("\($0.key)=\($0.value)")
+        }
+        envp.append(nil)
+        defer {
+            for pointer in argv { free(pointer) }
+            for pointer in envp { free(pointer) }
+        }
+
+        var pid: pid_t = 0
+        let spawned = posix_spawn(&pid, executable, nil, nil, argv, envp)
+        guard spawned == 0 else {
+            throw PermissionError.spawnFailed(command: executable, code: spawned)
+        }
+
+        var status: Int32 = 0
+        while waitpid(pid, &status, 0) < 0 {
+            guard errno == EINTR else {
+                throw PermissionError.spawnFailed(command: executable, code: errno)
+            }
+        }
+
+        // WIFEXITED and friends are C macros, so Swift does not import them.
+        let terminatingSignal = status & 0x7F
+        return terminatingSignal == 0 ? (status >> 8) & 0xFF : 128 + terminatingSignal
     }
 
     // MARK: - Interactive: the system prompt