Create the Windows data folder with its ACL instead of setting it after

On Windows the console sends Ctrl+C to both processes. The firewall
exited at once with 0xC000013A, handing the prompt back while a .cmd
shim's cmd.exe still asked "Terminate batch job (Y/N)?". It now ignores
Ctrl+C and Ctrl+Break while the manager runs and exits with its code.

A killed firewall also left the manager and its children running. The
firewall now joins a kill-on-close job before spawning, so whatever is
left dies with it.

An argument with a line break, which Rust refuses to pass to a batch
file, now says so instead of "batch file arguments are invalid".

Co-authored-by: Ian Graham Martinez <[email protected]>

core/Cargo.toml

@@ -38,14 +38,17 @@ path = "src/main.rs"
 [[bin]]
 name = "firewall-service"
 path = "src/bin/firewall-service.rs"
+required-features = ["machine-wide"]
 
 [[bin]]
 name = "firewall-tray"
 path = "src/bin/firewall-tray.rs"
+required-features = ["machine-wide"]
 
 [[bin]]
 name = "firewall-uninstall"
 path = "src/bin/firewall-uninstall.rs"
+required-features = ["machine-wide"]
 
 [[example]]
 name = "proxy-test"
@@ -87,6 +90,10 @@ path = "tests/tpm.rs"
 name = "managers"
 path = "tests/managers.rs"
 
+[features]
+# Builds the machine-wide binaries: the Windows service and tray, and the macOS uninstaller.
+machine-wide = []
+
 [dependencies]
 clap = "4.6.6"
 directories = "6.0.0"
@@ -118,7 +125,7 @@ schannel = "0.1.29"
 tokio = { version = "1.53.1", features = ["net"] }
 tracing-appender = "0.2.5"
 tray-icon = { version = "0.26.1", default-features = false }
-windows = { version = "0.62", features = ["Win32_Foundation", "Win32_Security", "Win32_Security_Authorization", "Win32_Security_Cryptography", "Win32_System_Com", "Win32_System_Console", "Win32_System_Environment", "Win32_System_JobObjects", "Win32_System_Threading", "Win32_UI_Shell", "Win32_UI_WindowsAndMessaging"] }
+windows = { version = "0.62", features = ["Win32_Foundation", "Win32_Security", "Win32_Security_Authorization", "Win32_Security_Cryptography", "Win32_Storage_FileSystem", "Win32_System_Com", "Win32_System_Console", "Win32_System_Environment", "Win32_System_JobObjects", "Win32_System_Threading", "Win32_UI_Shell", "Win32_UI_WindowsAndMessaging"] }
 windows-registry = "0.6.1"
 windows-service = "0.8.0"
 

core/src/config/mod.rs

@@ -1,10 +1,10 @@
 use crate::policies::registries::{Registry, BUILT_IN};
 use directories::ProjectDirs;
 use serde::Deserialize;
-use serde_json::{Map, Value};
+use serde_json::{json, Map, Value};
 use std::collections::HashMap;
 use std::io::{Error, ErrorKind};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 pub const DEFAULT_PORT: u16 = 8080;
 
@@ -129,3 +129,31 @@ fn merge(base: &mut Map<String, Value>, top: Map<String, Value>) {
         }
     }
 }
+
+/// Adds an `allow` entry to the file, leaving the rest of it as written.
+pub fn allow(path: &Path, eco: &str, name: &str, version: Option<&str>) -> std::io::Result<()> {
+    let invalid = |e: String| Error::new(ErrorKind::InvalidData, format!("{}: {e}", path.display()));
+    let mut config = match std::fs::read_to_string(path) {
+        Ok(text) => serde_json::from_str(&text).map_err(|e| invalid(e.to_string()))?,
+        Err(e) if e.kind() == ErrorKind::NotFound => json!({}),
+        Err(e) => return Err(e),
+    };
+    if !config.is_object() {
+        return Err(invalid("not an object".into()));
+    }
+    let entry = json!({ "name": name, "version": version });
+    let entries = &mut config["allow"][eco];
+    if entries.is_null() {
+        *entries = Value::Array(Vec::new());
+    }
+    let Some(entries) = entries.as_array_mut() else {
+        return Err(invalid(format!("allow.{eco} is not a list")));
+    };
+    if !entries.contains(&entry) {
+        entries.push(entry);
+    }
+    if let Some(dir) = path.parent() {
+        std::fs::create_dir_all(dir)?;
+    }
+    std::fs::write(path, serde_json::to_string_pretty(&config)?)
+}

core/src/os/macos/mod.rs

@@ -4,7 +4,7 @@ mod uninstall;
 
 pub use uninstall::uninstall;
 
-use crate::config::FirewallConfig;
+use crate::config::{self, FirewallConfig};
 use crate::{blocks, mitm, telemetry};
 use crate::Firewall;
 use rama::bytes::Bytes;
@@ -22,6 +22,7 @@ use rama::net::apple::networkextension::{transparent_proxy_ffi, NwTcpStream, Tcp
 use rama::rt::Executor;
 use rama::telemetry::tracing::apple::oslog::{OsLogLayer, Privacy};
 use rama::{Layer, Service};
+use serde::Deserialize;
 use std::convert::Infallible;
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -59,7 +60,11 @@ impl TransparentProxyHandler for Handler {
         Some(Bytes::from(match message.as_str() {
             "ca" => self.ca.pem.clone(),
             "blocks" => serde_json::to_string(&blocks::take()).expect("blocks serialize"),
-            other => format!("error: unknown message {other}"),
+            other => match other.strip_prefix("allow ").map(allow) {
+                Some(Ok(())) => "ok".to_owned(),
+                Some(Err(error)) => format!("error: {error}"),
+                None => format!("error: unknown message {other}"),
+            },
         }))
     }
 
@@ -118,6 +123,20 @@ fn handler(exec: Executor) -> Result<Handler, BoxError> {
     Ok(Handler { ca, hosts, service })
 }
 
+#[derive(Deserialize)]
+struct AllowRequest {
+    eco: String,
+    name: String,
+    version: Option<String>,
+}
+
+/// Takes effect when the provider restarts, which rebuilds it from the config.
+fn allow(request: &str) -> Result<(), BoxError> {
+    let request: AllowRequest = serde_json::from_str(request)?;
+    config::allow(CONFIG_FILE.as_ref(), &request.eco, &request.name, request.version.as_deref())?;
+    Ok(())
+}
+
 /// stderr is invisible in a system extension, so events go to the unified log:
 /// `log stream --predicate 'subsystem == "com.usestrix.firewall"'`.
 fn init(_config: Option<&TransparentProxyInitConfig>) -> bool {

core/src/os/windows/ca.rs

@@ -11,6 +11,7 @@ use std::time::{SystemTime, UNIX_EPOCH};
 use tracing::warn;
 use windows::Win32::Security::Authorization::{GetNamedSecurityInfoW, SE_FILE_OBJECT};
 use windows::Win32::Security::*;
+use windows::Win32::Storage::FileSystem::CreateDirectoryW;
 use windows_registry::Type;
 
 /// SYSTEM and admins write, users only read, so no one else can plant a CA for node.
@@ -65,25 +66,39 @@ pub fn load_or_create_ca(
     Ok(ca)
 }
 
-/// Created on first use, its owner and ACL reset every time. One a user made first, or a link,
+/// Created on first use with its ACL, which is reset every time. One a user made first, or a link,
 /// is replaced: its owner could grant itself access again, and a link would redirect our writes.
 pub(super) fn secure_data_dir() -> io::Result<PathBuf> {
     let dir = data_dir();
-    match std::fs::symlink_metadata(&dir) {
-        Ok(meta) if meta.file_type().is_symlink() => std::fs::remove_dir(&dir)?,
+    let exists = match std::fs::symlink_metadata(&dir) {
+        Ok(meta) if meta.file_type().is_symlink() => {
+            std::fs::remove_dir(&dir)?;
+            false
+        }
         Ok(_) if !owned_by_admins(&dir)? => {
             warn!(dir = %dir.display(), "replacing a data folder not created by an admin");
-            std::fs::remove_dir_all(&dir)?
+            std::fs::remove_dir_all(&dir)?;
+            false
         }
-        _ => {}
-    }
-    std::fs::create_dir_all(&dir)?;
+        Ok(_) => true,
+        Err(_) => false,
+    };
     let info = OWNER_SECURITY_INFORMATION
         | DACL_SECURITY_INFORMATION
         | PROTECTED_DACL_SECURITY_INFORMATION;
     let path = HSTRING::from(dir.as_path());
     let acl = security_descriptor(DATA_DIR_ACL)?;
-    unsafe { SetFileSecurityW(&path, info, PSECURITY_DESCRIPTOR(acl.0)).ok()? };
+    if exists {
+        unsafe { SetFileSecurityW(&path, info, PSECURITY_DESCRIPTOR(acl.0)).ok()? };
+    } else {
+        let attributes = SECURITY_ATTRIBUTES {
+            nLength: size_of::<SECURITY_ATTRIBUTES>() as u32,
+            lpSecurityDescriptor: acl.0,
+            bInheritHandle: false.into(),
+        };
+        // Never inherits ProgramData's ACL, which lets users add files; fails if it was recreated.
+        unsafe { CreateDirectoryW(&path, Some(&attributes))? };
+    }
     Ok(dir)
 }
 

core/src/os/windows/service.rs

@@ -26,6 +26,7 @@ use std::net::{IpAddr, Ipv4Addr};
 use std::sync::Arc;
 use std::time::Duration;
 use tracing_appender::rolling::{RollingFileAppender, Rotation};
+use windows::Win32::Foundation::ERROR_GEN_FAILURE;
 use windows_service::service::*;
 use windows_service::service_control_handler::{
     self, ServiceControlHandlerResult, ServiceStatusHandle,
@@ -73,8 +74,12 @@ fn run_until_stopped() -> Result<(), BoxError> {
         | ServiceControl::Shutdown
         | ServiceControl::Pause
         | ServiceControl::Continue => {
-            let _ = control_sender.send(control);
-            ServiceControlHandlerResult::NoError
+            // Answered once handled, so a failed pause fails the caller's ControlService.
+            let (reply, handled) = tokio::sync::oneshot::channel();
+            let _ = control_sender.send((control, reply));
+            handled
+                .blocking_recv()
+                .unwrap_or(ServiceControlHandlerResult::NoError)
         }
         ServiceControl::Interrogate => ServiceControlHandlerResult::NoError,
         _ => ServiceControlHandlerResult::NotImplemented,
@@ -89,16 +94,26 @@ fn run_until_stopped() -> Result<(), BoxError> {
             }
         };
         // Only pausing removes our hosts entries; a stop or crash keeps them, failing closed.
-        while let Some(control) = control_receiver.recv().await {
+        while let Some((control, reply)) = control_receiver.recv().await {
             let (hosts, state) = match control {
                 ServiceControl::Pause => (&[][..], ServiceState::Paused),
                 ServiceControl::Continue => (&hosts[..], ServiceState::Running),
                 _ => break,
             };
-            match write_hosts_entries(hosts) {
-                Ok(()) => set_status(&status, state, false)?,
-                Err(error) => tracing::error!(%error, "could not rewrite the hosts file"),
-            }
+            let result = match write_hosts_entries(hosts) {
+                Ok(()) => {
+                    set_status(&status, state, false)?;
+                    ServiceControlHandlerResult::NoError
+                }
+                Err(error) => {
+                    tracing::error!(%error, "could not rewrite the hosts file");
+                    let code = error
+                        .raw_os_error()
+                        .map_or(ERROR_GEN_FAILURE.0, |code| code as u32);
+                    ServiceControlHandlerResult::Other(code)
+                }
+            };
+            let _ = reply.send(result);
         }
         Ok::<_, BoxError>(())
     });
@@ -147,7 +162,7 @@ async fn start_screening(status: &ServiceStatusHandle) -> Result<Vec<&'static st
                 resolver: resolver.clone(),
                 service: service.clone(),
             };
-            let upstream = ConsumeErrLayer::trace_as_debug().into_layer(upstream);
+            let upstream = ConsumeErrLayer::trace_as_warning().into_layer(upstream);
             tokio::spawn(listen_on(address, port, &exec)?.serve(upstream));
         }
     }

core/src/os/windows/tray.rs

@@ -144,7 +144,11 @@ impl Tray {
 }
 
 fn show_error(error: BoxError) {
-    let text = HSTRING::from(error.to_string());
+    let text = match error.source() {
+        Some(source) => format!("{error}: {source}"),
+        None => error.to_string(),
+    };
+    let text = HSTRING::from(text);
     unsafe { MessageBoxW(None, &text, w!("Strix Firewall"), MB_ICONERROR) };
 }
 

core/tests/config.rs

@@ -57,3 +57,18 @@ async fn failing_closed_blocks_what_could_not_be_checked() {
     let blocked = screen(url, &firewall).await.unwrap_or_default();
     assert!(blocked.contains("could not be checked"), "{blocked:?}");
 }
+
+#[test]
+fn allowing_keeps_the_rest_of_the_file() {
+    let path = std::env::temp_dir().join(format!("firewall-allow-{}.json", std::process::id()));
+    std::fs::write(&path, r#"{"fail_open": false}"#).expect("write");
+    for _ in 0..2 {
+        firewall::config::allow(&path, "npm", "left-pad", Some("1.3.0")).expect("allow");
+    }
+    let text = std::fs::read_to_string(&path).expect("read");
+    std::fs::remove_file(&path).ok();
+    let config: FirewallConfig = serde_json::from_str(&text).expect("parses");
+    assert!(!config.fail_open);
+    assert_eq!(config.allow["npm"].len(), 1);
+    assert_eq!(config.allow["npm"][0].version.as_deref(), Some("1.3.0"));
+}

dist-workspace.toml

@@ -7,6 +7,7 @@ ci = "github"
 installers = ["shell", "powershell", "homebrew", "msi"]
 # core/wix/main.wxs is edited to install the service.
 allow-dirty = ["msi"]
+features = ["machine-wide"]
 tap = "usestrix/homebrew-tap"
 publish-jobs = ["homebrew", "./publish-crates"]
 targets = ["aarch64-apple-darwin", "x86_64-apple-darwin", "aarch64-unknown-linux-gnu", "x86_64-unknown-linux-gnu", "x86_64-pc-windows-msvc"]

macos/App/BlockAlerts.swift

@@ -1,4 +1,5 @@
 import AppKit
+import Security
 
 struct BlockedPackage: Codable, Hashable, Identifiable {
     let eco: String
@@ -11,22 +12,46 @@ struct BlockedPackage: Codable, Hashable, Identifiable {
     var label: String { version.map { "\(name) \($0)" } ?? name }
     /// The denylist and OSV only flag packages known to be malicious; the age check only holds back new ones.
     var malicious: Bool { filter != "age" }
+    /// Malware is never allowed, and a new package only by version.
+    var trustable: Bool { !malicious && version != nil }
 }
 
 @MainActor
 enum BlockAlert {
-    static func show(_ package: BlockedPackage) {
+    /// Returns whether the user chose to trust the package.
+    static func show(_ package: BlockedPackage) -> Bool {
         let alert = NSAlert()
         alert.addButton(withTitle: "OK")
         if package.malicious {
             alert.alertStyle = .critical
-            alert.messageText = "Blocked a malicious package"
-            alert.informativeText = "\(package.label) (\(package.eco)) \(package.reason). Do not install it."
+            alert.messageText = "Blocked malware: \(package.label) (\(package.eco))"
+            alert.informativeText = "\(package.label) \(package.reason).\n\n"
+                + "It was not installed. Don't install it from another source. "
+                + "If you didn't expect this package, a dependency may be compromised; tell your security team."
         } else {
             alert.messageText = "Held back a new package"
             alert.informativeText = "\(package.label) (\(package.eco)) \(package.reason)."
+            if package.trustable { alert.addButton(withTitle: "Trust this version") }
         }
         NSApp.activate(ignoringOtherApps: true)
-        alert.runModal()
+        return alert.runModal() == .alertSecondButtonReturn
+    }
+}
+
+enum AdminAuthorization {
+    /// The allowlist applies to every user of the Mac, so changing it takes an admin, as `sudo` would.
+    static func confirm() -> Bool {
+        var authorization: AuthorizationRef?
+        guard AuthorizationCreate(nil, nil, [], &authorization) == errAuthorizationSuccess,
+              let authorization else { return false }
+        defer { AuthorizationFree(authorization, []) }
+        return "system.preferences".withCString { name in
+            var item = AuthorizationItem(name: name, valueLength: 0, value: nil, flags: 0)
+            return withUnsafeMutablePointer(to: &item) { item in
+                var rights = AuthorizationRights(count: 1, items: item)
+                let flags: AuthorizationFlags = [.interactionAllowed, .extendRights]
+                return AuthorizationCopyRights(authorization, &rights, nil, flags, nil) == errAuthorizationSuccess
+            }
+        }
     }
 }

macos/App/FirewallModel.swift

@@ -29,11 +29,13 @@ enum FirewallError: Error, LocalizedError {
     case extensionUnavailable
     case screeningDidNotStart(NEVPNStatus)
     case extensionStopped(String)
+    case extensionRefused(String)
 
     var errorDescription: String? {
         switch self {
         case .extensionUnavailable: return "The extension is not running"
         case let .screeningDidNotStart(status): return "Screening did not start (\(status.label))"
+        case let .extensionRefused(reply): return "The extension replied \(reply)"
         case let .extensionStopped(reason):
             return "The extension stopped: \(reason). Its log: log show --last 5m --predicate 'subsystem BEGINSWITH \"\(FirewallIDs.appBundleID)\"'"
         }
@@ -201,6 +203,28 @@ final class FirewallModel: NSObject, ObservableObject {
         if let url = URL(string: pane) { NSWorkspace.shared.open(url) }
     }
 
+    /// Allowing a version writes it into the extension's config, which a restart then loads.
+    func trust(_ package: BlockedPackage) async {
+        guard package.trustable else { return }
+        guard AdminAuthorization.confirm() else {
+            log("Trust cancelled for \(package.label)")
+            return
+        }
+        do {
+            var request = ["eco": package.eco, "name": package.name]
+            request["version"] = package.version
+            let json = String(decoding: try JSONSerialization.data(withJSONObject: request), as: UTF8.self)
+            let reply = try await providerMessage("allow \(json)")
+            guard reply == "ok" else { throw FirewallError.extensionRefused(reply) }
+            blocked.removeAll { $0 == package }
+            log("Trusted \(package.label) (\(package.eco))")
+        } catch {
+            log("Could not trust \(package.label): \(error.localizedDescription)")
+            return
+        }
+        await restart()
+    }
+
     /// The extension cannot message the app, so the app asks it for blocks.
     private func watchBlocks() async {
         while true {
@@ -208,7 +232,7 @@ final class FirewallModel: NSObject, ObservableObject {
                let packages = try? JSONDecoder().decode([BlockedPackage].self, from: Data(reply.utf8)) {
                 for package in packages where !blocked.contains(package) {
                     blocked.append(package)
-                    BlockAlert.show(package)
+                    if BlockAlert.show(package) { await trust(package) }
                 }
                 blocked = Array(blocked.suffix(10))
             }

macos/App/MenuBarView.swift

@@ -29,6 +29,10 @@ struct MenuBarView: View {
                 if !package.malicious {
                     Menu("Held back \(package.label) (\(package.eco))") {
                         Text(package.reason)
+                        Button("Trust this version") {
+                            Task { await model.trust(package) }
+                        }
+                        .disabled(model.busy || !package.trustable)
                     }
                 } else {
                     Menu("Blocked \(package.label) (\(package.eco))") {

macos/project.yml

@@ -133,7 +133,7 @@ targets:
               arm64|arm64e) triple=aarch64-apple-darwin ;;
               x86_64)       triple=x86_64-apple-darwin ;;
             esac
-            cargo build --bin firewall-uninstall --target $triple $([ "$CONFIGURATION" = Debug ] || echo --release)
+            cargo build --bin firewall-uninstall --features machine-wide --target $triple $([ "$CONFIGURATION" = Debug ] || echo --release)
             bins="$bins target/$triple/$CARGO_PROFILE/firewall-uninstall"
           done
           lipo -create $bins -output "$TARGET_BUILD_DIR/$EXECUTABLE_FOLDER_PATH/firewall-uninstall"