Make the links in the Windows block popups clickable (#75)

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

core/Cargo.lock

@@ -711,6 +711,20 @@ version = "1.18.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "252afb9ae5eaa683babdc6a068b3f5726eb19e05070c731f9b2a23a7c3e8ed34"
 
+[[package]]
+name = "embed-resource"
+version = "3.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6168487b5e7eb2673e6efe1200b1848016e436a6ca0b8031bf04bd9d493a249f"
+dependencies = [
+ "cc",
+ "memchr",
+ "rustc_version",
+ "toml",
+ "vswhom",
+ "winreg",
+]
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.42"
@@ -3243,6 +3257,15 @@ dependencies = [
  "zmij",
 ]
 
+[[package]]
+name = "serde_spanned"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e7523beb55eece201a2356bee0bbca0d1ab466c14c07703b2e0ee6d42cb0c2c"
+dependencies = [
+ "serde_core",
+]
+
 [[package]]
 name = "sha1"
 version = "0.11.0"
@@ -3375,6 +3398,7 @@ dependencies = [
  "clap",
  "core-foundation 0.10.1",
  "directories",
+ "embed-resource",
  "muda",
  "percent-encoding",
  "png",
@@ -3671,10 +3695,25 @@ dependencies = [
 ]
 
 [[package]]
-name = "toml_datetime"
-version = "1.1.1+spec-1.1.0"
+name = "toml"
+version = "1.1.8+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3165f65f62e28e0115a00b2ebdd37eb6f3b641855f9d636d3cd4103767159ad7"
+checksum = "20489e00e4d8741d6be680764cc12e270655e375a20d1011e844a9c3379e678d"
+dependencies = [
+ "indexmap",
+ "serde_core",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_parser",
+ "toml_writer",
+ "winnow",
+]
+
+[[package]]
+name = "toml_datetime"
+version = "1.1.2+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b86d767906c6c42421dcba507eb9d203e779497710a47782a224bb871653053"
 dependencies = [
  "serde_core",
 ]
@@ -3693,13 +3732,19 @@ dependencies = [
 
 [[package]]
 name = "toml_parser"
-version = "1.1.3+spec-1.1.0"
+version = "1.1.5+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d38ac1cf9b95face32296c0a3ede1fdc270627c9d9c02a7274dd6d960dc4d56"
+checksum = "baa693a8032d7e1cada7d0041e96126df243179ff061456783ac7f12bda4744c"
 dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "toml_writer"
+version = "1.1.3+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06bdbd8cfc056b8d2e2e85f29b56a3bdbecb527cef81eb39e3e7b98af4652770"
+
 [[package]]
 name = "tower-layer"
 version = "0.3.3"
@@ -3909,6 +3954,26 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "vswhom"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be979b7f07507105799e854203b470ff7c78a1639e330a58f183b5fea574608b"
+dependencies = [
+ "libc",
+ "vswhom-sys",
+]
+
+[[package]]
+name = "vswhom-sys"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb067e4cbd1ff067d1df46c9194b5de0e98efd2810bbc95c5d5e5f25a3231150"
+dependencies = [
+ "cc",
+ "libc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"
@@ -4284,6 +4349,16 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "winreg"
+version = "0.56.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d6f32a0ff4a9f6f01231eb2059cc85479330739333e0e58cadf03b6af2cca10"
+dependencies = [
+ "cfg-if",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "wit-bindgen"
 version = "0.57.1"

core/Cargo.toml

@@ -90,6 +90,10 @@ path = "tests/tpm.rs"
 name = "managers"
 path = "tests/managers.rs"
 
+[[test]]
+name = "blocks"
+path = "tests/blocks.rs"
+
 [features]
 # Builds the machine-wide binaries: the Windows service and tray, and the macOS uninstaller.
 machine-wide = []
@@ -125,7 +129,7 @@ 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_Storage_FileSystem", "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_LibraryLoader", "Win32_System_Pipes", "Win32_System_Registry", "Win32_System_Threading", "Win32_UI_Controls", "Win32_UI_Shell", "Win32_UI_WindowsAndMessaging"] }
 windows-registry = "0.6.1"
 windows-service = "0.8.0"
 
@@ -135,3 +139,7 @@ tokio = { version = "1.53.1", features = ["macros", "rt-multi-thread"] }
 [profile.dist]
 inherits = "release"
 lto = "thin"
+
+# Only on Windows hosts, where the tray and service are built.
+[target.'cfg(windows)'.build-dependencies]
+embed-resource = "3.0.12"

core/build.rs

@@ -0,0 +1,16 @@
+//! The tray's task dialogs exist only in version 6 of the common controls, which takes a manifest.
+//! Both machine-wide binaries also get the Strix icon.
+fn main() {
+    println!("cargo:rerun-if-changed=src/bin/firewall-tray.manifest");
+    let msvc = std::env::var("CARGO_CFG_TARGET_ENV").as_deref() == Ok("msvc");
+    if msvc && std::env::var_os("CARGO_FEATURE_MACHINE_WIDE").is_some() {
+        let manifest = concat!(env!("CARGO_MANIFEST_DIR"), "/src/bin/firewall-tray.manifest");
+        println!("cargo:rustc-link-arg-bin=firewall-tray=/MANIFEST:EMBED");
+        println!("cargo:rustc-link-arg-bin=firewall-tray=/MANIFESTINPUT:{manifest}");
+        #[cfg(windows)]
+        embed_resource::compile_for("src/bin/firewall.rc", ["firewall-tray", "firewall-service"], embed_resource::NONE)
+            // Fails the build, rather than ship without the icon.
+            .manifest_required()
+            .unwrap();
+    }
+}

core/src/bin/firewall-tray.manifest

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+  <dependency>
+    <dependentAssembly>
+      <assemblyIdentity type="win32" name="Microsoft.Windows.Common-Controls" version="6.0.0.0"
+        processorArchitecture="*" publicKeyToken="6595b64144ccf1df" language="*"/>
+    </dependentAssembly>
+  </dependency>
+</assembly>

core/src/bin/firewall.rc

@@ -0,0 +1,2 @@
+// The icon Explorer, UAC and the tray's popups show.
+1 ICON "strix.ico"

core/src/blocks.rs

@@ -1,14 +1,25 @@
+use crate::config::{self, AllowedPackage};
 use crate::policies::Package;
+use crate::Firewall;
+use rama::error::BoxError;
 use serde::Serialize;
+use std::path::Path;
 use std::sync::Mutex;
+use std::time::{Duration, Instant};
+use tokio::sync::watch;
 
-/// Bounded, so blocks pile up harmlessly while nothing collects them.
+/// So blocks can't pile up while no app collects them.
 const KEPT: usize = 50;
+/// Under pip's, pipenv's and pdm's 15 s read timeout, the shortest of the supported managers.
+const HOLD: Duration = Duration::from_secs(10);
+/// Only hold while an app is asking for blocks, so someone can answer.
+const WATCHED: Duration = Duration::from_secs(2);
+/// For a minute, so the rest of that install can fetch it too.
+const ONCE: Duration = Duration::from_secs(60);
 
-static RECENT: Mutex<Vec<BlockedPackage>> = Mutex::new(Vec::new());
-
-#[derive(Serialize)]
+#[derive(Clone, Serialize)]
 pub struct BlockedPackage {
+    pub id: u64,
     pub eco: &'static str,
     pub name: String,
     pub version: Option<String>,
@@ -16,21 +27,125 @@ pub struct BlockedPackage {
     pub reason: String,
 }
 
-pub fn record(eco: &'static str, pkg: &Package, filter: &'static str, reason: &str) {
-    let mut recent = RECENT.lock().unwrap_or_else(|e| e.into_inner());
-    if recent.len() == KEPT {
-        recent.remove(0);
+struct Blocks {
+    last_id: u64,
+    unsent: Vec<BlockedPackage>,
+    /// Age holds, the only blocks that can be allowed, each with what wakes its waiting downloads.
+    held: Vec<(BlockedPackage, watch::Sender<bool>)>,
+    polled: Option<Instant>,
+}
+
+static BLOCKS: Mutex<Blocks> =
+    Mutex::new(Blocks { last_id: 0, unsent: Vec::new(), held: Vec::new(), polled: None });
+
+/// Records a block and holds a new package's download for up to `HOLD`. Returns whether it was allowed.
+pub async fn block(eco: &'static str, pkg: &Package, filter: &'static str, reason: &str) -> bool {
+    let Some(mut answer) = record(eco, pkg, filter, reason) else {
+        return false;
+    };
+    let allowed = tokio::time::timeout(HOLD, answer.wait_for(|allowed| *allowed)).await;
+    matches!(allowed, Ok(Ok(_)))
+}
+
+/// The app's requests: `blocks`, `allow <id>` or `allow-once <id>`.
+/// An allow replies `late` if the download had stopped waiting.
+pub fn answer(firewall: &Firewall, config: &Path, request: &str) -> String {
+    if request == "blocks" {
+        return serde_json::to_string(&take()).expect("blocks serialize");
     }
-    recent.push(BlockedPackage {
+    let result = match request.split_once(' ').map(|(verb, id)| (verb, id.parse())) {
+        Some(("allow", Ok(id))) => trust(firewall, config, id),
+        Some(("allow-once", Ok(id))) => allow_once(firewall, id),
+        _ => Err(format!("unknown message {request}").into()),
+    };
+    match result {
+        Ok(true) => "ok".to_owned(),
+        Ok(false) => "late".to_owned(),
+        Err(error) => format!("error: {error}"),
+    }
+}
+
+/// Hands each block over once.
+fn take() -> Vec<BlockedPackage> {
+    let mut blocks = lock();
+    blocks.polled = Some(Instant::now());
+    std::mem::take(&mut blocks.unsent)
+}
+
+fn record(
+    eco: &'static str,
+    pkg: &Package,
+    filter: &'static str,
+    reason: &str,
+) -> Option<watch::Receiver<bool>> {
+    let mut blocks = lock();
+    let watched = blocks.polled.is_some_and(|polled| polled.elapsed() < WATCHED);
+    let holds = filter == "age" && watched;
+    // A repeat fetch of a held package waits on the same answer.
+    let waiting = blocks.held.iter().find(|(held, wake)| {
+        wake.receiver_count() > 0 && held.eco == eco && held.name == pkg.name && held.version == pkg.version
+    });
+    if let (true, Some((_, wake))) = (holds, waiting) {
+        return Some(wake.subscribe());
+    }
+    blocks.last_id += 1;
+    let block = BlockedPackage {
+        id: blocks.last_id,
         eco,
         name: pkg.name.clone(),
         version: pkg.version.clone(),
         filter,
         reason: reason.to_owned(),
-    });
+    };
+    push(&mut blocks.unsent, block.clone());
+    if filter != "age" {
+        return None;
+    }
+    let (wake, allowed) = watch::channel(false);
+    push(&mut blocks.held, (block, wake));
+    holds.then_some(allowed)
 }
 
-/// Hands each block over once.
-pub fn take() -> Vec<BlockedPackage> {
-    std::mem::take(&mut *RECENT.lock().unwrap_or_else(|e| e.into_inner()))
+/// Also saved to the config, so it survives a restart.
+fn trust(firewall: &Firewall, config: &Path, id: u64) -> Result<bool, BoxError> {
+    let block = held(id)?;
+    let version = block.version.ok_or("only a version can be trusted")?;
+    config::allow(config, block.eco, &block.name, &version)?;
+    let package = AllowedPackage { name: block.name, version: Some(version) };
+    firewall.lift_age_check(block.eco, package, None);
+    Ok(release(id))
+}
+
+fn allow_once(firewall: &Firewall, id: u64) -> Result<bool, BoxError> {
+    let block = held(id)?;
+    let package = AllowedPackage { name: block.name, version: block.version };
+    firewall.lift_age_check(block.eco, package, Some(Instant::now() + ONCE));
+    Ok(release(id))
+}
+
+fn held(id: u64) -> Result<BlockedPackage, BoxError> {
+    let blocks = lock();
+    let held = blocks.held.iter().find(|(held, _)| held.id == id);
+    Ok(held.ok_or(format!("no new package was held back as {id}"))?.0.clone())
+}
+
+/// Returns whether a download was still waiting.
+fn release(id: u64) -> bool {
+    let blocks = lock();
+    let Some((_, wake)) = blocks.held.iter().find(|(held, _)| held.id == id) else {
+        return false;
+    };
+    wake.send_replace(true);
+    wake.receiver_count() > 0
+}
+
+fn push<T>(list: &mut Vec<T>, item: T) {
+    if list.len() == KEPT {
+        list.remove(0);
+    }
+    list.push(item);
+}
+
+fn lock() -> std::sync::MutexGuard<'static, Blocks> {
+    BLOCKS.lock().unwrap_or_else(|e| e.into_inner())
 }

core/src/config/mod.rs

@@ -121,7 +121,7 @@ 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<()> {
+pub fn allow(path: &Path, eco: &str, name: &str, version: &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()))?,

core/src/firewall.rs

@@ -1,4 +1,4 @@
-use crate::config::FirewallConfig;
+use crate::config::{AllowedPackage, FirewallConfig};
 use crate::policies::filters::age::Age;
 use crate::policies::filters::denylist::Denylist;
 use crate::policies::filters::osv::Osv;
@@ -6,12 +6,16 @@ use crate::policies::filters::Filter;
 use crate::policies::registries::*;
 use regex::Regex;
 use std::collections::HashMap;
+use std::sync::Mutex;
+use std::time::Instant;
 
 pub struct Firewall {
     pub config: FirewallConfig,
     registries: Vec<&'static Registry>,
     patterns: HashMap<&'static str, Vec<Regex>>,
     filters: Vec<Box<dyn Filter>>,
+    /// Each lift expires at its time, or lasts until the firewall stops. Never saved.
+    age_lifted: Mutex<Vec<(String, AllowedPackage, Option<Instant>)>>,
 }
 
 impl Default for Firewall {
@@ -34,7 +38,7 @@ impl Firewall {
         if config.min_age_hours > 0 {
             filters.push(Box::new(Age::new(config.min_age_hours)));
         }
-        Firewall { config, registries, patterns, filters }
+        Firewall { config, registries, patterns, filters, age_lifted: Mutex::default() }
     }
 
     pub fn match_on<'a>(
@@ -72,6 +76,19 @@ impl Firewall {
     pub fn filters(&self) -> &[Box<dyn Filter>] {
         &self.filters
     }
+
+    pub fn lift_age_check(&self, eco: &str, package: AllowedPackage, until: Option<Instant>) {
+        let mut lifted = self.age_lifted.lock().unwrap_or_else(|e| e.into_inner());
+        lifted.retain(|(_, _, until)| until.is_none_or(|until| until > Instant::now()));
+        lifted.push((eco.to_owned(), package, until));
+    }
+
+    pub fn age_check_lifted(&self, eco: &str, matches: impl Fn(&AllowedPackage) -> bool) -> bool {
+        let lifted = self.age_lifted.lock().unwrap_or_else(|e| e.into_inner());
+        lifted.iter().any(|(e, package, until)| {
+            e == eco && until.is_none_or(|until| until > Instant::now()) && matches(package)
+        })
+    }
 }
 
 /// The built-ins, then a copy of one per mirror. Leaked, as a `Registry` is `'static` everywhere.

core/src/os/macos/mod.rs

@@ -4,7 +4,7 @@ mod uninstall;
 
 pub use uninstall::uninstall;
 
-use crate::config::{self, FirewallConfig};
+use crate::config::FirewallConfig;
 use crate::{blocks, mitm, telemetry};
 use crate::Firewall;
 use rama::bytes::Bytes;
@@ -22,7 +22,6 @@ 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;
@@ -40,6 +39,7 @@ const CONFIG_FILE: &str = "/Library/Application Support/Firewall/config.json";
 struct Handler {
     ca: Arc<mitm::CertificateAuthority>,
     hosts: Vec<&'static str>,
+    firewall: Arc<Firewall>,
     service: mitm::MitmService,
 }
 
@@ -59,12 +59,7 @@ impl TransparentProxyHandler for Handler {
         let message = String::from_utf8_lossy(&message).into_owned();
         Some(Bytes::from(match message.as_str() {
             "ca" => self.ca.pem.clone(),
-            "blocks" => serde_json::to_string(&blocks::take()).expect("blocks serialize"),
-            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}"),
-            },
+            other => blocks::answer(&self.firewall, CONFIG_FILE.as_ref(), other),
         }))
     }
 
@@ -119,22 +114,8 @@ fn handler(exec: Executor) -> Result<Handler, BoxError> {
     let signer: mitm::CaSigner = Arc::new(key);
     let ca = install::certificate_authority(&hosts, &*signer);
     let ca = Arc::new(ca.inspect_err(|_| telemetry::error("ca"))?);
-    let service = mitm::mitm_service(firewall, &ca, signer, None, exec);
-    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(())
+    let service = mitm::mitm_service(firewall.clone(), &ca, signer, None, exec);
+    Ok(Handler { ca, hosts, firewall, service })
 }
 
 /// stderr is invisible in a system extension, so events go to the unified log:

core/src/os/windows/mod.rs

@@ -2,6 +2,7 @@
 //! LocalSystem service screens it as the macOS extension does.
 
 mod ca;
+mod pipe;
 mod service;
 mod tpm;
 mod tray;

core/src/os/windows/pipe.rs

@@ -0,0 +1,102 @@
+//! How the tray asks the service what it blocked, and allows a new package, as the macOS app
+//! messages its extension.
+
+use super::{config_file, security_descriptor};
+use crate::{blocks, Firewall};
+use rama::error::BoxError;
+use std::os::windows::io::AsRawHandle;
+use std::sync::Arc;
+use std::time::Duration;
+use tokio::io::{AsyncBufReadExt, AsyncReadExt, AsyncWriteExt, BufReader};
+use tokio::net::windows::named_pipe::{NamedPipeServer, ServerOptions};
+use windows::core::{Owned, PWSTR};
+use windows::Win32::Foundation::HANDLE;
+use windows::Win32::Security::*;
+use windows::Win32::System::Pipes::{GetNamedPipeClientProcessId, ImpersonateNamedPipeClient};
+use windows::Win32::System::Threading::*;
+
+pub(super) const PIPE: &str = r"\\.\pipe\StrixFirewall";
+/// Signed-in users can connect, as the tray runs as them.
+const PIPE_ACL: &str = "D:P(A;;GA;;;SY)(A;;GA;;;BA)(A;;GRGW;;;IU)";
+
+pub(super) async fn serve(firewall: Arc<Firewall>) -> Result<(), BoxError> {
+    let mut server = create(true)?;
+    loop {
+        server.connect().await?;
+        let client = std::mem::replace(&mut server, create(false)?);
+        let firewall = Arc::clone(&firewall);
+        tokio::spawn(async move {
+            if let Err(error) = answer(client, &firewall).await {
+                tracing::debug!(%error, "could not answer the tray");
+            }
+        });
+    }
+}
+
+fn create(first: bool) -> Result<NamedPipeServer, BoxError> {
+    let acl = security_descriptor(PIPE_ACL)?;
+    let mut attributes = SECURITY_ATTRIBUTES {
+        nLength: size_of::<SECURITY_ATTRIBUTES>() as u32,
+        lpSecurityDescriptor: acl.0,
+        bInheritHandle: false.into(),
+    };
+    let attributes = (&raw mut attributes).cast();
+    let mut options = ServerOptions::new();
+    // Fails if anyone else made the pipe first.
+    options.first_pipe_instance(first);
+    Ok(unsafe { options.create_with_security_attributes_raw(PIPE, attributes)? })
+}
+
+/// A line each way.
+async fn answer(client: NamedPipeServer, firewall: &Firewall) -> Result<(), BoxError> {
+    let mut client = BufReader::new(client);
+    let mut request = String::new();
+    (&mut client)
+        .take(64 * 1024)
+        .read_line(&mut request)
+        .await?;
+    let request = request.trim_end();
+    // Only the app can message the macOS extension; here any program could connect.
+    let reply = if !client_is_tray(client.get_ref())? {
+        "error: only the tray can ask".to_owned()
+    } else if request.starts_with("allow ") && !client_is_admin(client.get_ref())? {
+        "error: trusting a package takes an administrator".to_owned()
+    } else {
+        blocks::answer(firewall, &config_file(), request)
+    };
+    client.write_all(format!("{reply}\n").as_bytes()).await?;
+    // Closing before the tray hangs up could discard the reply.
+    let _ = tokio::time::timeout(Duration::from_secs(5), client.read(&mut [0])).await;
+    Ok(())
+}
+
+fn client_is_tray(client: &NamedPipeServer) -> Result<bool, BoxError> {
+    let mut id = 0;
+    unsafe { GetNamedPipeClientProcessId(HANDLE(client.as_raw_handle()), &mut id)? };
+    let process = unsafe { Owned::new(OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, false, id)?) };
+    let mut path = [0u16; 1024];
+    let mut len = path.len() as u32;
+    let flags = PROCESS_NAME_WIN32;
+    unsafe { QueryFullProcessImageNameW(*process, flags, PWSTR(path.as_mut_ptr()), &mut len)? };
+    let path = String::from_utf16(&path[..len as usize])?;
+    let tray = std::env::current_exe()?.with_file_name("firewall-tray.exe");
+    // Windows paths ignore case.
+    Ok(path.to_lowercase() == tray.to_string_lossy().to_lowercase())
+}
+
+/// Elevated, as only an elevated token has the Administrators group enabled.
+fn client_is_admin(client: &NamedPipeServer) -> windows::core::Result<bool> {
+    let mut sid = [0u32; SECURITY_MAX_SID_SIZE as usize / 4];
+    let admins = PSID(sid.as_mut_ptr().cast());
+    let mut size = SECURITY_MAX_SID_SIZE;
+    unsafe { CreateWellKnownSid(WinBuiltinAdministratorsSid, None, Some(admins), &mut size)? };
+    unsafe { ImpersonateNamedPipeClient(HANDLE(client.as_raw_handle()))? };
+    let mut member = false.into();
+    let checked = unsafe { CheckTokenMembership(None, admins, &mut member) };
+    // Carrying on as the client would be worse than stopping.
+    if unsafe { RevertToSelf() }.is_err() {
+        std::process::abort();
+    }
+    checked?;
+    Ok(member.as_bool())
+}

core/src/os/windows/service.rs

@@ -1,6 +1,8 @@
 use super::ca::{load_or_create_ca, secure_data_dir};
 use super::tpm::CaKey;
-use super::{config_file, loopback_addresses, write_hosts_entries, CRL_ADDRESS, SERVICE_NAME};
+use super::{
+    config_file, loopback_addresses, pipe, write_hosts_entries, CRL_ADDRESS, SERVICE_NAME,
+};
 use crate::config::FirewallConfig;
 use crate::http::{reply, text};
 use crate::{mitm, telemetry, Firewall};
@@ -153,6 +155,13 @@ async fn start_screening(status: &ServiceStatusHandle) -> Result<Vec<&'static st
     let crl = HttpServer::auto(exec.clone()).service(crl);
     tokio::spawn(listen_on(CRL_ADDRESS, 80, &exec)?.serve(crl));
 
+    let tray_firewall = Arc::clone(&firewall);
+    tokio::spawn(async move {
+        if let Err(error) = pipe::serve(tray_firewall).await {
+            tracing::error!(%error, "the tray cannot reach the service");
+        }
+    });
+
     let service = mitm::mitm_service(firewall, &ca, signer, Some(crl_url), exec.clone());
     for (address, host) in loopback_addresses(&hosts) {
         for port in [80, 443] {

core/src/os/windows/tray.rs

@@ -1,27 +1,53 @@
 //! The notification-area icon, started at sign-in as the menu bar app is on macOS.
 
+use super::pipe::PIPE;
 use super::*;
-use muda::{Menu, MenuEvent, MenuItem, PredefinedMenuItem};
-use std::io::Cursor;
+use muda::{IsMenuItem, Menu, MenuEvent, MenuItem, PredefinedMenuItem, Submenu};
+use serde::Deserialize;
+use std::io::{BufRead, BufReader, Cursor, Write};
+use std::os::windows::io::AsRawHandle;
+use std::sync::mpsc::{channel, Receiver, Sender};
 use std::time::Duration;
 use tray_icon::{Icon, MouseButtonState, TrayIcon, TrayIconBuilder, TrayIconEvent};
-use windows::core::{w, PCWSTR};
+use windows::core::{w, HRESULT, PCWSTR};
 use windows::Win32::Foundation::*;
-use windows::Win32::System::Threading::CreateMutexW;
+use windows::Win32::System::LibraryLoader::GetModuleHandleW;
+use windows::Win32::System::Pipes::GetNamedPipeServerProcessId;
+use windows::Win32::System::Threading::*;
+use windows::Win32::UI::Controls::*;
 use windows::Win32::UI::Shell::*;
 use windows::Win32::UI::WindowsAndMessaging::*;
 use windows_registry::CURRENT_USER;
-use windows_service::service::{Service, ServiceAccess, ServiceState};
+use windows_service::service::{Service, ServiceAccess, ServiceState, ServiceStatus};
 use windows_service::service_manager::{ServiceManager, ServiceManagerAccess};
 
 const MENU_PAUSE: &str = "pause";
 const MENU_RESTART: &str = "restart";
 const MENU_LOG: &str = "log";
 const MENU_QUIT: &str = "quit";
+/// Also the service's requests, and `allow` the elevated `firewall-tray` command.
+const ALLOW: &str = "allow";
+const ALLOW_ONCE: &str = "allow-once";
 const LOGO: &[u8] = include_bytes!("tray.png");
+/// Where blocked packages are listed, below Open logs.
+const BLOCKED_AT: usize = 5;
+const BLOCKED_KEPT: usize = 10;
 
 /// Runs until Quit, once per session.
 pub fn run() -> Result<(), BoxError> {
+    let args: Vec<String> = std::env::args().skip(1).collect();
+    if let [verb, id, label @ ..] = &args[..] {
+        if verb == ALLOW {
+            // Run by `run_elevated`, so the service can tell an admin asked.
+            let trusted = ask_service(&format!("{ALLOW} {id}"))
+                .and_then(|reply| answered(&format!("Trusted {}", label.join(" ")), &reply));
+            if let Err(error) = trusted {
+                show_error(error);
+                std::process::exit(1);
+            }
+            return Ok(());
+        }
+    }
     // Held until we exit.
     let _mutex = unsafe { CreateMutexW(None, false, w!(r"Local\StrixFirewallTray"))? };
     if unsafe { GetLastError() } == ERROR_ALREADY_EXISTS {
@@ -29,6 +55,7 @@ pub fn run() -> Result<(), BoxError> {
     }
     let status = MenuItem::new("", false, None);
     let pause = MenuItem::with_id(MENU_PAUSE, "", false, None);
+    let blocked_separator = PredefinedMenuItem::separator();
     let menu = Menu::with_items(&[
         &status,
         &PredefinedMenuItem::separator(),
@@ -39,7 +66,9 @@ pub fn run() -> Result<(), BoxError> {
         &MenuItem::with_id(MENU_QUIT, "Quit", true, None),
     ])?;
     let (logo, logo_size) = logo_mask()?;
-    let icon = TrayIconBuilder::new().with_menu(Box::new(menu)).build()?;
+    let icon = TrayIconBuilder::new()
+        .with_menu(Box::new(menu.clone()))
+        .build()?;
     let window = HWND(icon.window_handle());
     let mut tray = Tray {
         icon,
@@ -49,9 +78,14 @@ pub fn run() -> Result<(), BoxError> {
         status,
         pause,
         state: None,
+        menu,
+        blocked_separator,
+        blocked: Vec::new(),
+        allowed: channel(),
     };
     tray.update();
-    unsafe { SetTimer(None, 0, 2000, None) };
+    // The service holds a new package's download only while it is asked this often.
+    unsafe { SetTimer(None, 0, 500, None) };
     let mut message = MSG::default();
     while unsafe { GetMessageW(&mut message, None, 0, 0) }.0 > 0 {
         unsafe { DispatchMessageW(&message) };
@@ -62,6 +96,7 @@ pub fn run() -> Result<(), BoxError> {
         // Ours, not the icon window's own hover timer.
         if message.message == WM_TIMER && message.hwnd.is_invalid() {
             tray.update();
+            tray.collect_blocks();
         }
         while let Ok(event) = TrayIconEvent::receiver().try_recv() {
             // The menu opens on release, so this keeps it current.
@@ -94,11 +129,47 @@ struct Tray {
     pause: MenuItem,
     /// As the menu last showed it.
     state: Option<ServiceState>,
+    menu: Menu,
+    blocked_separator: PredefinedMenuItem,
+    /// The most recent, as the menu lists them.
+    blocked: Vec<BlockedPackage>,
+    /// Allowed from another thread, so no longer listed.
+    allowed: (Sender<BlockedPackage>, Receiver<BlockedPackage>),
+}
+
+#[derive(Clone, PartialEq, Deserialize)]
+struct BlockedPackage {
+    id: u64,
+    eco: String,
+    name: String,
+    version: Option<String>,
+    filter: String,
+    reason: String,
+}
+
+impl BlockedPackage {
+    fn label(&self) -> String {
+        match &self.version {
+            Some(version) => format!("{} {version} ({})", self.name, self.eco),
+            None => format!("{} ({})", self.name, self.eco),
+        }
+    }
+
+    /// The denylist and OSV only flag packages known to be malicious; the age check only holds
+    /// back new ones.
+    fn malicious(&self) -> bool {
+        self.filter != "age"
+    }
+
+    /// Malware is never allowed, and a new package only by version.
+    fn trustable(&self) -> bool {
+        !self.malicious() && self.version.is_some()
+    }
 }
 
 impl Tray {
     fn update(&mut self) {
-        self.state = service_state();
+        self.state = service_status().map(|status| status.current_state);
         let screening = self.state == Some(ServiceState::Running);
         let light = light_taskbar();
         if self.drawn != Some((light, screening)) {
@@ -117,7 +188,88 @@ impl Tray {
         self.pause.set_enabled(self.state.is_some());
     }
 
+    /// The service hands each block over once, so whichever tray asks first shows it.
+    fn collect_blocks(&mut self) {
+        let allowed: Vec<_> = self.allowed.1.try_iter().collect();
+        if !allowed.is_empty() {
+            self.blocked.retain(|blocked| !allowed.contains(blocked));
+            self.list_blocked();
+        }
+        if self.state != Some(ServiceState::Running) {
+            return;
+        }
+        let Ok(reply) = ask_service("blocks") else {
+            return;
+        };
+        let Ok(packages) = serde_json::from_str::<Vec<BlockedPackage>>(&reply) else {
+            return;
+        };
+        let mut new = Vec::new();
+        for package in packages {
+            if !self.blocked.contains(&package) {
+                self.blocked.push(package.clone());
+                new.push(package);
+            }
+        }
+        if new.is_empty() {
+            return;
+        }
+        let excess = self.blocked.len().saturating_sub(BLOCKED_KEPT);
+        self.blocked.drain(..excess);
+        self.list_blocked();
+        // Off the UI thread, so the menu keeps working while they are open.
+        let allowed = self.allowed.0.clone();
+        std::thread::spawn(move || {
+            for package in new {
+                if let Some(trust) = alert(&package) {
+                    allow(package, trust, &allowed);
+                }
+            }
+        });
+    }
+
+    fn list_blocked(&self) {
+        while self.menu.items().len() > BLOCKED_AT + 2 {
+            self.menu.remove_at(BLOCKED_AT);
+        }
+        let _ = self.menu.insert(&self.blocked_separator, BLOCKED_AT);
+        for (i, package) in self.blocked.iter().enumerate() {
+            let verb = if package.malicious() {
+                "Blocked"
+            } else {
+                "Held back"
+            };
+            let reason = if package.malicious() {
+                format!("Malicious: {}", package.reason)
+            } else {
+                package.reason.clone()
+            };
+            let reason = MenuItem::new(reason, false, None);
+            let trustable = package.trustable();
+            let once = MenuItem::with_id(format!("{ALLOW_ONCE}:{i}"), "Allow Once", trustable, None);
+            let always = MenuItem::with_id(format!("{ALLOW}:{i}"), "Trust this version", trustable, None);
+            let items: &[&dyn IsMenuItem] = if package.malicious() {
+                &[&reason]
+            } else {
+                &[&reason, &once, &always]
+            };
+            let label = format!("{verb} {}", package.label());
+            if let Ok(item) = Submenu::with_items(label, true, items) {
+                let _ = self.menu.insert(&item, BLOCKED_AT + 1 + i);
+            }
+        }
+    }
+
     fn on_menu(&self, id: &str) {
+        if let Some((verb @ (ALLOW | ALLOW_ONCE), i)) = id.split_once(':') {
+            let trust = verb == ALLOW;
+            let package = i.parse().ok().and_then(|i: usize| self.blocked.get(i));
+            if let Some(package) = package.cloned() {
+                let allowed = self.allowed.0.clone();
+                std::thread::spawn(move || allow(package, trust, &allowed));
+            }
+            return;
+        }
         let state = self.state;
         let screening = state == Some(ServiceState::Running);
         let action: fn() -> Result<(), BoxError> = match id {
@@ -143,6 +295,169 @@ impl Tray {
     }
 }
 
+const ALLOW_ONCE_BUTTON: i32 = 100;
+const TRUST_BUTTON: i32 = 101;
+/// `firewall.rc`'s icon, embedded by `build.rs`.
+const STRIX_ICON: PCWSTR = PCWSTR(1 as _);
+
+/// `Some(true)` if the user chose to trust it, `Some(false)` to allow it once.
+/// A task dialog, as a message box can't have both buttons.
+fn alert(package: &BlockedPackage) -> Option<bool> {
+    let text = format!("{} {}.", package.label(), package.reason);
+    let (title, text, icon) = if package.malicious() {
+        let title = format!("Blocked malware: {}", package.label());
+        let text = text
+            + "\n\nIt 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.";
+        (title, text, TD_ERROR_ICON)
+    } else {
+        ("Held back a new package".to_owned(), text, STRIX_ICON)
+    };
+    let button = |id, text| TASKDIALOG_BUTTON { nButtonID: id, pszButtonText: text };
+    let allow = [button(ALLOW_ONCE_BUTTON, w!("Allow Once")), button(TRUST_BUTTON, w!("Trust this version"))];
+    let buttons: &[_] = if package.trustable() { &allow } else { &[] };
+    let (title, text) = (HSTRING::from(title), HSTRING::from(linked(&text)));
+    let dialog = TASKDIALOGCONFIG {
+        cbSize: size_of::<TASKDIALOGCONFIG>() as u32,
+        dwFlags: TDF_ENABLE_HYPERLINKS,
+        // Where `STRIX_ICON` is loaded from; the `TD_` icons are Windows'.
+        hInstance: unsafe { GetModuleHandleW(None) }.ok()?.into(),
+        dwCommonButtons: TDCBF_CLOSE_BUTTON,
+        pszWindowTitle: w!("Strix Firewall"),
+        Anonymous1: TASKDIALOGCONFIG_0 { pszMainIcon: icon },
+        pszMainInstruction: PCWSTR(title.as_ptr()),
+        pszContent: PCWSTR(text.as_ptr()),
+        cButtons: buttons.len() as u32,
+        pButtons: buttons.as_ptr(),
+        pfCallback: Some(on_dialog),
+        ..Default::default()
+    };
+    let mut chosen = 0;
+    unsafe { TaskDialogIndirect(&dialog, Some(&raw mut chosen), None, None) }.ok()?;
+    match chosen {
+        ALLOW_ONCE_BUTTON => Some(false),
+        TRUST_BUTTON => Some(true),
+        _ => None,
+    }
+}
+
+/// Asks for the foreground, as `MB_SETFOREGROUND` did; Windows may still leave it behind.
+/// Opens the links `linked` made, in the browser.
+unsafe extern "system" fn on_dialog(
+    window: HWND,
+    event: TASKDIALOG_NOTIFICATIONS,
+    _: WPARAM,
+    link: LPARAM,
+    _: isize,
+) -> HRESULT {
+    if event == TDN_CREATED {
+        let _ = unsafe { SetForegroundWindow(window) };
+    } else if event == TDN_HYPERLINK_CLICKED {
+        let link = PCWSTR(link.0 as *const u16);
+        // Only web pages, whatever a block's reason contains.
+        let web = unsafe { link.to_string() }
+            .is_ok_and(|link| link.starts_with("https://") || link.starts_with("http://"));
+        if web {
+            let none = PCWSTR::null();
+            unsafe { ShellExecuteW(None, w!("open"), link, none, none, SW_SHOWNORMAL) };
+        }
+    }
+    S_OK
+}
+
+/// A task dialog's markup for the text, with each URL a link.
+fn linked(text: &str) -> String {
+    let mut marked = String::new();
+    let mut rest = text;
+    while let Some(start) = ["https://", "http://"].iter().filter_map(|scheme| rest.find(scheme)).min() {
+        let end = rest[start..].find(|c: char| c.is_whitespace() || c == ',' || c == ')');
+        let url = rest[start..end.map_or(rest.len(), |end| start + end)].trim_end_matches('.');
+        marked += &rest[..start];
+        marked += &format!("<a href=\"{url}\">{url}</a>");
+        rest = &rest[start + url.len()..];
+    }
+    marked + rest
+}
+
+/// Trusting writes the config for every user, so it goes through a UAC prompt.
+/// The elevated process shows its own errors and late replies.
+fn allow(package: BlockedPackage, trust: bool, allowed: &Sender<BlockedPackage>) {
+    let allowed_it = if trust {
+        run_elevated(&[ALLOW, &package.id.to_string(), &package.label()])
+            .map(|code| code == Some(0))
+    } else {
+        let title = format!("Allowed {} for the next minute", package.label());
+        ask_service(&format!("{ALLOW_ONCE} {}", package.id))
+            .and_then(|reply| answered(&title, &reply))
+            .map(|()| true)
+    };
+    match allowed_it {
+        Ok(true) => {
+            let _ = allowed.send(package);
+        }
+        Ok(false) => {}
+        Err(error) => show_error(error),
+    }
+}
+
+/// Tells the user, under `title`, when the install had already stopped waiting.
+fn answered(title: &str, reply: &str) -> Result<(), BoxError> {
+    match reply {
+        "ok" => Ok(()),
+        "late" => {
+            let text = "The install had already stopped waiting for it. Run it again to finish.";
+            let (title, text) = (HSTRING::from(title), HSTRING::from(text));
+            unsafe { MessageBoxW(None, &text, &title, MB_ICONINFORMATION | MB_SETFOREGROUND) };
+            Ok(())
+        }
+        other => Err(other.into()),
+    }
+}
+
+/// This program as an admin, waiting for its exit code; `None` if the user said no.
+fn run_elevated(args: &[&str]) -> Result<Option<u32>, BoxError> {
+    let exe = HSTRING::from(std::env::current_exe()?.as_path());
+    let parameters = HSTRING::from(args.join(" "));
+    let mut info = SHELLEXECUTEINFOW {
+        cbSize: size_of::<SHELLEXECUTEINFOW>() as u32,
+        fMask: SEE_MASK_NOCLOSEPROCESS,
+        lpVerb: w!("runas"),
+        lpFile: PCWSTR(exe.as_ptr()),
+        lpParameters: PCWSTR(parameters.as_ptr()),
+        nShow: SW_HIDE.0,
+        ..Default::default()
+    };
+    if let Err(error) = unsafe { ShellExecuteExW(&mut info) } {
+        if error.code() == ERROR_CANCELLED.to_hresult() {
+            return Ok(None);
+        }
+        return Err(error.into());
+    }
+    let process = unsafe { Owned::new(info.hProcess) };
+    unsafe { WaitForSingleObject(*process, INFINITE) };
+    let mut code = 1;
+    unsafe { GetExitCodeProcess(*process, &mut code)? };
+    Ok(Some(code))
+}
+
+/// One request per connection, as the service answers.
+fn ask_service(request: &str) -> Result<String, BoxError> {
+    let mut pipe = std::fs::OpenOptions::new()
+        .read(true)
+        .write(true)
+        .open(PIPE)?;
+    // Any program can create the pipe if it gets there before the service.
+    let mut server = 0;
+    unsafe { GetNamedPipeServerProcessId(HANDLE(pipe.as_raw_handle()), &mut server)? };
+    if service_status().and_then(|status| status.process_id) != Some(server) {
+        return Err("Another program is posing as the firewall service.".into());
+    }
+    pipe.write_all(format!("{request}\n").as_bytes())?;
+    let mut reply = String::new();
+    BufReader::new(pipe).read_line(&mut reply)?;
+    Ok(reply.trim_end().to_owned())
+}
+
 fn show_error(error: BoxError) {
     let text = match error.source() {
         Some(source) => format!("{error}: {source}"),
@@ -153,13 +468,13 @@ fn show_error(error: BoxError) {
 }
 
 /// `None` when the service is not installed.
-fn service_state() -> Option<ServiceState> {
+fn service_status() -> Option<ServiceStatus> {
     let manager =
         ServiceManager::local_computer(None::<&str>, ServiceManagerAccess::CONNECT).ok()?;
     let service = manager
         .open_service(SERVICE_NAME, ServiceAccess::QUERY_STATUS)
         .ok()?;
-    Some(service.query_status().ok()?.current_state)
+    service.query_status().ok()
 }
 
 fn light_taskbar() -> bool {
@@ -167,7 +482,8 @@ fn light_taskbar() -> bool {
     let Ok(key) = CURRENT_USER.open(personalize) else {
         return false;
     };
-    key.get_u32("SystemUsesLightTheme").is_ok_and(|light| light == 1)
+    key.get_u32("SystemUsesLightTheme")
+        .is_ok_and(|light| light == 1)
 }
 
 fn status_text(state: Option<ServiceState>) -> &'static str {

core/src/policies/filters/mod.rs

@@ -3,6 +3,7 @@ pub mod denylist;
 pub mod osv;
 
 use super::registries::{Package, Registry};
+use crate::config::AllowedPackage;
 use crate::Firewall;
 use std::future::Future;
 use std::pin::Pin;
@@ -31,10 +32,11 @@ pub async fn consult(
     registry: &'static Registry,
     pkg: &Package,
 ) -> Option<(&'static str, Verdict)> {
-    let allowed = allowed(firewall, registry, pkg);
+    let lifted = allowed(firewall, registry, pkg)
+        || firewall.age_check_lifted(registry.eco, |entry| matches(registry, pkg, entry));
     let mut unsure = None;
     for filter in firewall.filters() {
-        if allowed && filter.name() == "age" {
+        if lifted && filter.name() == "age" {
             continue;
         }
         match filter.check(registry, pkg).await {
@@ -51,13 +53,15 @@ fn allowed(firewall: &Firewall, registry: &Registry, pkg: &Package) -> bool {
     let Some(entries) = firewall.config.allow.get(registry.eco) else {
         return false;
     };
-    entries.iter().any(|entry| {
-        let name_matches = match registry.normalize {
-            Some(normalize) => normalize(&entry.name) == pkg.name,
-            None => entry.name == pkg.name,
-        };
-        // Go writes a leading v that the parsed version drops, and PEP 440 ignores one.
-        let version = entry.version.as_deref().map(|v| v.strip_prefix('v').unwrap_or(v));
-        name_matches && (version.is_none() || version == pkg.version.as_deref())
-    })
+    entries.iter().any(|entry| matches(registry, pkg, entry))
+}
+
+fn matches(registry: &Registry, pkg: &Package, entry: &AllowedPackage) -> bool {
+    let name_matches = match registry.normalize {
+        Some(normalize) => normalize(&entry.name) == pkg.name,
+        None => entry.name == pkg.name,
+    };
+    // Go writes a leading v that the parsed version drops, and PEP 440 ignores one.
+    let version = entry.version.as_deref().map(|v| v.strip_prefix('v').unwrap_or(v));
+    name_matches && (version.is_none() || version == pkg.version.as_deref())
 }

core/src/policies/mod.rs

@@ -70,7 +70,10 @@ pub async fn screen(url: &str, firewall: &Firewall) -> Option<String> {
     info!(eco = registry.eco, pkg = %pkg.label(), %url, "screening");
     match consult(firewall, registry, &pkg).await {
         Some((filter, Verdict::Deny(reason))) => {
-            crate::blocks::record(registry.eco, &pkg, filter, &reason);
+            if crate::blocks::block(registry.eco, &pkg, filter, &reason).await {
+                info!(eco = registry.eco, pkg = %pkg.label(), "allowed while held");
+                return None;
+            }
             Some(format!("{} {reason}", pkg.label()))
         }
         Some((filter, Verdict::Unknown(e))) if !firewall.config.fail_open => {

core/tests/blocks.rs

@@ -0,0 +1,27 @@
+use firewall::blocks::{answer, block};
+use firewall::policies::Package;
+use firewall::Firewall;
+use std::path::Path;
+use std::time::Duration;
+
+#[tokio::test]
+async fn allowing_once_releases_the_held_download() {
+    let firewall = Firewall::default();
+    let config = Path::new("/nonexistent/config.json");
+    let pkg = Package { name: "left-pad".into(), version: Some("1.3.0".into()) };
+    assert!(!block("npm", &pkg, "age", "is new").await, "held while nothing was asking");
+    answer(&firewall, config, "blocks");
+
+    let held = tokio::spawn(async move { block("npm", &pkg, "age", "is new").await });
+    let id = loop {
+        let blocks: serde_json::Value = serde_json::from_str(&answer(&firewall, config, "blocks")).unwrap();
+        if let Some(id) = blocks[0]["id"].as_u64() {
+            break id;
+        }
+        tokio::time::sleep(Duration::from_millis(10)).await;
+    };
+    assert_eq!(answer(&firewall, config, &format!("allow-once {id}")), "ok");
+    assert!(held.await.unwrap(), "the waiting download goes through");
+    assert!(firewall.age_check_lifted("npm", |p| p.name == "left-pad"), "and the rest of the install");
+    assert!(!block("npm", &Package { name: "evil".into(), version: None }, "denylist", "is malware").await);
+}

core/tests/config.rs

@@ -1,4 +1,4 @@
-use firewall::config::path;
+use firewall::config::{path, AllowedPackage};
 use firewall::policies::filters::consult;
 use firewall::policies::{screen, Package};
 use firewall::{Firewall, FirewallConfig};
@@ -95,12 +95,23 @@ async fn failing_closed_blocks_what_could_not_be_checked() {
     assert!(blocked.contains("could not be checked"), "{blocked:?}");
 }
 
+#[tokio::test]
+async fn lifting_the_age_check_still_checks_for_malware() {
+    let config = r#"{"denylist": {"base": "http://127.0.0.1:1"}}"#;
+    let firewall = Firewall::new(serde_json::from_str(config).expect("parses"));
+    let (registry, _) = firewall.match_on("/go/golang.org/x/net/@v/list", |r| r.prefix).expect("go");
+    let pkg = Package { name: "golang.org/x/net".into(), version: Some("0.20.0".into()) };
+    firewall.lift_age_check("go", AllowedPackage { name: pkg.name.clone(), version: None }, None);
+    let (filter, _) = consult(&firewall, registry, &pkg).await.expect("the denylist still runs");
+    assert_eq!(filter, "denylist");
+}
+
 #[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");
+        firewall::config::allow(&path, "npm", "left-pad", "1.3.0").expect("allow");
     }
     let text = std::fs::read_to_string(&path).expect("read");
     std::fs::remove_file(&path).ok();

macos/App/BlockAlerts.swift

@@ -2,13 +2,13 @@ import AppKit
 import Security
 
 struct BlockedPackage: Codable, Hashable, Identifiable {
+    let id: UInt64
     let eco: String
     let name: String
     let version: String?
     let filter: String
     let reason: String
 
-    var id: String { "\(eco)/\(name)@\(version ?? "")" }
     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" }
@@ -16,25 +16,61 @@ struct BlockedPackage: Codable, Hashable, Identifiable {
     var trustable: Bool { !malicious && version != nil }
 }
 
+enum Allowance {
+    /// For a minute, so the rest of that install can fetch it too.
+    case once
+    case always
+}
+
 @MainActor
 enum BlockAlert {
-    /// Returns whether the user chose to trust the package.
-    static func show(_ package: BlockedPackage) -> Bool {
+    static func show(_ package: BlockedPackage) -> Allowance? {
         let alert = NSAlert()
         alert.addButton(withTitle: "OK")
         if package.malicious {
             alert.alertStyle = .critical
             alert.messageText = "Blocked malware: \(package.label) (\(package.eco))"
-            alert.informativeText = "\(package.label) \(package.reason).\n\n"
+            setText(alert, "\(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."
+                + "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") }
+            setText(alert, "\(package.label) (\(package.eco)) \(package.reason).")
+            if package.trustable {
+                alert.addButton(withTitle: "Allow Once")
+                alert.addButton(withTitle: "Trust this version")
+            }
         }
         NSApp.activate(ignoringOtherApps: true)
-        return alert.runModal() == .alertSecondButtonReturn
+        switch alert.runModal() {
+        case .alertSecondButtonReturn: return .once
+        case .alertThirdButtonReturn: return .always
+        default: return nil
+        }
+    }
+
+    static func late(_ package: BlockedPackage, _ allowance: Allowance) {
+        let alert = NSAlert()
+        alert.messageText = allowance == .once ? "Allowed \(package.label) for the next minute" : "Trusted \(package.label)"
+        alert.informativeText = "The install had already stopped waiting for it. Run it again to finish."
+        NSApp.activate(ignoringOtherApps: true)
+        alert.runModal()
+    }
+
+    /// An alert's own text is plain, so this text goes in a selectable field, where its links open on click.
+    private static func setText(_ alert: NSAlert, _ text: String) {
+        let linked = NSMutableAttributedString(string: text, attributes: [.font: NSFont.systemFont(ofSize: NSFont.smallSystemFontSize)])
+        let detector = try! NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
+        for match in detector.matches(in: text, range: NSRange(text.startIndex..., in: text)) {
+            if let url = match.url { linked.addAttribute(.link, value: url, range: match.range) }
+        }
+        let field = NSTextField(wrappingLabelWithString: "")
+        field.allowsEditingTextAttributes = true
+        field.isSelectable = true
+        field.attributedStringValue = linked
+        field.preferredMaxLayoutWidth = 300
+        field.frame.size = field.fittingSize
+        alert.accessoryView = field
     }
 }
 

macos/App/FirewallModel.swift

@@ -203,26 +203,22 @@ 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 {
+    /// Trusting changes the config for every user, so it takes an admin.
+    func allow(_ package: BlockedPackage, _ allowance: Allowance) async {
         guard package.trustable else { return }
-        guard AdminAuthorization.confirm() else {
+        if allowance == .always, !AdminAuthorization.confirm() {
             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) }
+            let reply = try await providerMessage("\(allowance == .once ? "allow-once" : "allow") \(package.id)")
+            guard reply == "ok" || reply == "late" else { throw FirewallError.extensionRefused(reply) }
             blocked.removeAll { $0 == package }
-            log("Trusted \(package.label) (\(package.eco))")
+            log("Allowed \(package.label) (\(package.eco)) \(allowance)")
+            if reply == "late" { BlockAlert.late(package, allowance) }
         } catch {
-            log("Could not trust \(package.label): \(error.localizedDescription)")
-            return
+            log("Could not allow \(package.label): \(error.localizedDescription)")
         }
-        await restart()
     }
 
     /// The extension cannot message the app, so the app asks it for blocks.
@@ -232,11 +228,11 @@ 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)
-                    if BlockAlert.show(package) { await trust(package) }
+                    if let allowance = BlockAlert.show(package) { await allow(package, allowance) }
                 }
                 blocked = Array(blocked.suffix(10))
             }
-            try? await Task.sleep(nanoseconds: 2_000_000_000)
+            try? await Task.sleep(nanoseconds: 500_000_000)
         }
     }
 

macos/App/MenuBarView.swift

@@ -29,8 +29,12 @@ struct MenuBarView: View {
                 if !package.malicious {
                     Menu("Held back \(package.label) (\(package.eco))") {
                         Text(package.reason)
+                        Button("Allow Once") {
+                            Task { await model.allow(package, .once) }
+                        }
+                        .disabled(model.busy || !package.trustable)
                         Button("Trust this version") {
-                            Task { await model.trust(package) }
+                            Task { await model.allow(package, .always) }
                         }
                         .disabled(model.busy || !package.trustable)
                     }