Let an admin trust a held-back version of a new package

core/src/blocks.rs

@@ -0,0 +1,36 @@
+use crate::policies::Package;
+use serde::Serialize;
+use std::sync::Mutex;
+
+/// Bounded, so blocks pile up harmlessly while nothing collects them.
+const KEPT: usize = 50;
+
+static RECENT: Mutex<Vec<BlockedPackage>> = Mutex::new(Vec::new());
+
+#[derive(Serialize)]
+pub struct BlockedPackage {
+    pub eco: &'static str,
+    pub name: String,
+    pub version: Option<String>,
+    pub filter: &'static str,
+    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);
+    }
+    recent.push(BlockedPackage {
+        eco,
+        name: pkg.name.clone(),
+        version: pkg.version.clone(),
+        filter,
+        reason: reason.to_owned(),
+    });
+}
+
+/// Hands each block over once.
+pub fn take() -> Vec<BlockedPackage> {
+    std::mem::take(&mut *RECENT.lock().unwrap_or_else(|e| e.into_inner()))
+}

core/src/config/mod.rs

@@ -1,19 +1,17 @@
-use crate::policies::registries::{host_of, BUILT_IN};
+use crate::policies::registries::{Registry, BUILT_IN};
 use directories::ProjectDirs;
-use rama::net::uri::Uri;
 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::num::{NonZeroU16, NonZeroU64};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 pub const DEFAULT_PORT: u16 = 8080;
 
 #[derive(Debug, Deserialize)]
 #[serde(default, deny_unknown_fields)]
 pub struct FirewallConfig {
-    pub port: NonZeroU16,
+    pub port: u16,
     /// Allow a package when a filter could not check it.
     pub fail_open: bool,
     /// 0 turns the age check off.
@@ -22,8 +20,9 @@ pub struct FirewallConfig {
     /// Packages never screened, by ecosystem: `{"npm": [{"name": "left-pad"}]}`.
     pub allow: HashMap<String, Vec<AllowedPackage>>,
     pub telemetry: bool,
-    /// Mirrors laid out like a built-in registry, by its name: `{"npm": ["https://npm.example.com/"]}`.
-    pub registries: HashMap<String, Vec<String>>,
+    /// Not describable in the file yet, so this is always the built-in table.
+    #[serde(skip)]
+    pub registries: Vec<&'static Registry>,
 }
 
 #[derive(Debug, Deserialize)]
@@ -41,19 +40,19 @@ pub struct DenylistSource {
     pub base: String,
     /// Polled for a new commit, which re-fetches every list in use.
     pub revision: String,
-    pub poll_secs: NonZeroU64,
+    pub poll_secs: u64,
 }
 
 impl Default for FirewallConfig {
     fn default() -> Self {
         FirewallConfig {
-            port: NonZeroU16::new(DEFAULT_PORT).unwrap(),
+            port: DEFAULT_PORT,
             fail_open: true,
-            min_age_hours: 0,
+            min_age_hours: 24,
             denylist: DenylistSource::default(),
             allow: HashMap::new(),
             telemetry: true,
-            registries: HashMap::new(),
+            registries: BUILT_IN.to_vec(),
         }
     }
 }
@@ -64,7 +63,7 @@ impl Default for DenylistSource {
             base: "https://raw.githubusercontent.com/usestrix/firewall-blocklist/main".into(),
             revision: "https://api.github.com/repos/usestrix/firewall-blocklist/commits/main"
                 .into(),
-            poll_secs: NonZeroU64::new(10).unwrap(),
+            poll_secs: 10,
         }
     }
 }
@@ -88,8 +87,7 @@ impl FirewallConfig {
             };
             let invalid = |e| Error::new(ErrorKind::InvalidData, format!("{}: {e}", path.display()));
             let layer: Value = serde_json::from_str(&text).map_err(invalid)?;
-            let config = FirewallConfig::deserialize(&layer).map_err(invalid)?;
-            check(&config).map_err(|e| Error::new(ErrorKind::InvalidData, format!("{}: {e}", path.display())))?;
+            FirewallConfig::deserialize(&layer).map_err(invalid)?;
             let Value::Object(layer) = layer else {
                 unreachable!("a config parses only from an object");
             };
@@ -99,7 +97,19 @@ impl FirewallConfig {
     }
 
     pub fn local_url(&self, path: &str) -> String {
-        crate::local_url(self.port.get(), path)
+        crate::local_url(self.port, path)
+    }
+
+    /// Without building a `Firewall`, which needs a runtime.
+    pub fn hosts(&self) -> Vec<&'static str> {
+        let mut hosts: Vec<&'static str> = Vec::new();
+        for registry in &self.registries {
+            let host = registry.host();
+            if !hosts.contains(&host) {
+                hosts.push(host);
+            }
+        }
+        hosts
     }
 }
 
@@ -120,42 +130,30 @@ fn merge(base: &mut Map<String, Value>, top: Map<String, Value>) {
     }
 }
 
-/// What serde's types cannot say.
-fn check(config: &FirewallConfig) -> Result<(), String> {
-    // `Duration::hours` panics past this.
-    if config.min_age_hours > time::Duration::MAX.whole_hours() as u64 {
-        return Err(format!("{} hours is too long", config.min_age_hours));
+/// 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()));
     }
-    for eco in config.allow.keys() {
-        if !BUILT_IN.iter().any(|r| r.eco == eco) {
-            return Err(format!("unknown ecosystem {eco:?} in allow"));
-        }
+    let entry = json!({ "name": name, "version": version });
+    let entries = &mut config["allow"][eco];
+    if entries.is_null() {
+        *entries = Value::Array(Vec::new());
     }
-    for url in [&config.denylist.base, &config.denylist.revision] {
-        if parse_url(url, &["http", "https"]).is_none() {
-            return Err(format!("{url:?} is not an http(s) URL"));
-        }
+    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);
     }
-    for (name, mirrors) in &config.registries {
-        if !BUILT_IN.iter().any(|r| r.name() == name) {
-            return Err(format!("no built-in registry is named {name}"));
-        }
-        if let Some(url) = mirrors.iter().find(|url| !is_mirror(url)) {
-            return Err(format!("{url}: a mirror is an https:// URL ending in /"));
-        }
+    if let Some(dir) = path.parent() {
+        std::fs::create_dir_all(dir)?;
     }
-    Ok(())
-}
-
-/// No port or userinfo, as `host_of` is what gets intercepted.
-fn is_mirror(url: &str) -> bool {
-    let Some(uri) = parse_url(url, &["https"]) else { return false };
-    let bare_host = uri.host_str().is_some_and(|host| host == host_of(url));
-    bare_host && uri.query().is_none() && uri.fragment().is_none() && url.ends_with('/')
-}
-
-fn parse_url(url: &str, schemes: &[&str]) -> Option<Uri> {
-    let uri = Uri::parse(url).ok()?;
-    let has_host = uri.host_str().is_some_and(|host| !host.is_empty());
-    (has_host && schemes.contains(&uri.scheme_str()?)).then_some(uri)
+    std::fs::write(path, serde_json::to_string_pretty(&config)?)
 }

core/src/firewall.rs

@@ -9,7 +9,6 @@ use std::collections::HashMap;
 
 pub struct Firewall {
     pub config: FirewallConfig,
-    registries: Vec<&'static Registry>,
     patterns: HashMap<&'static str, Vec<Regex>>,
     filters: Vec<Box<dyn Filter>>,
 }
@@ -22,19 +21,18 @@ impl Default for Firewall {
 
 impl Firewall {
     pub fn new(config: FirewallConfig) -> Self {
-        let registries = with_mirrors(&config.registries);
         let mut patterns = HashMap::new();
-        for registry in &registries {
+        for registry in &config.registries {
             let compiled = registry.patterns.iter().map(|p| Regex::new(p.re).expect(p.re));
             patterns.insert(registry.prefix, compiled.collect());
         }
-        let ecosystems = registries.iter().map(|r| r.osv_name);
+        let ecosystems = config.registries.iter().map(|r| r.osv_name);
         let denylist = Denylist::new(config.denylist.clone(), ecosystems);
         let mut filters: Vec<Box<dyn Filter>> = vec![Box::new(denylist), Box::new(Osv)];
         if config.min_age_hours > 0 {
             filters.push(Box::new(Age::new(config.min_age_hours)));
         }
-        Firewall { config, registries, patterns, filters }
+        Firewall { config, patterns, filters }
     }
 
     pub fn match_on<'a>(
@@ -42,27 +40,20 @@ impl Firewall {
         url: &'a str,
         key: fn(&Registry) -> &'static str,
     ) -> Option<(&'static Registry, &'a str)> {
-        self.registries.iter().find_map(|r| url.strip_prefix(key(r)).map(|rest| (*r, rest)))
+        self.config.registries.iter().find_map(|r| url.strip_prefix(key(r)).map(|rest| (*r, rest)))
     }
 
     pub fn hosts(&self) -> Vec<&'static str> {
-        let mut hosts: Vec<&'static str> = Vec::new();
-        for registry in &self.registries {
-            let host = registry.host();
-            if !hosts.contains(&host) {
-                hosts.push(host);
-            }
-        }
-        hosts
+        self.config.hosts()
     }
 
     pub fn is_https_url(&self, url: &str) -> bool {
         let host = host_of(url);
-        self.registries.iter().any(|r| r.upstream.starts_with("https://") && r.host() == host)
+        self.config.registries.iter().any(|r| r.upstream.starts_with("https://") && r.host() == host)
     }
 
     pub fn is_index_url(&self, url: &str) -> bool {
-        self.registries.iter().any(|r| r.index && r.host() == host_of(url))
+        self.config.registries.iter().any(|r| r.index && r.host() == host_of(url))
     }
 
     pub fn resolve(&self, registry: &'static Registry, rest: &str) -> Resolved {
@@ -73,15 +64,3 @@ impl Firewall {
         &self.filters
     }
 }
-
-/// The built-ins, then a copy of one per mirror. Leaked, as a `Registry` is `'static` everywhere.
-fn with_mirrors(mirrors: &HashMap<String, Vec<String>>) -> Vec<&'static Registry> {
-    let mut registries = BUILT_IN.to_vec();
-    for built_in in BUILT_IN {
-        for upstream in mirrors.get(built_in.name()).into_iter().flatten() {
-            let upstream = upstream.clone().leak();
-            registries.push(Box::leak(Box::new(Registry { upstream, ..(*built_in).clone() })));
-        }
-    }
-    registries
-}

core/src/lib.rs

@@ -1,4 +1,5 @@
 pub mod aliasing;
+pub mod blocks;
 pub mod config;
 pub mod firewall;
 pub mod http;

core/src/os/macos/mod.rs

@@ -4,8 +4,8 @@ mod uninstall;
 
 pub use uninstall::uninstall;
 
-use crate::config::FirewallConfig;
-use crate::{mitm, telemetry};
+use crate::config::{self, FirewallConfig};
+use crate::{blocks, mitm, telemetry};
 use crate::Firewall;
 use rama::bytes::Bytes;
 use rama::error::BoxError;
@@ -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;
@@ -58,7 +59,12 @@ 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(),
-            other => format!("error: unknown message {other}"),
+            "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}"),
+            },
         }))
     }
 
@@ -117,6 +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/policies/filters/denylist.rs

@@ -143,7 +143,7 @@ pub fn describe(advisories: &[&Advisory]) -> String {
 
 /// A failed fetch leaves the last good list in place; a list that never loaded is retried every tick.
 async fn watch(source: DenylistSource, lists: Arc<Lists>) {
-    let period = Duration::from_secs(source.poll_secs.get());
+    let period = Duration::from_secs(source.poll_secs);
     let mut seen = revision(&source, None).await;
     loop {
         tokio::time::sleep(period).await;

core/src/policies/mod.rs

@@ -69,7 +69,8 @@ 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((_, Verdict::Deny(reason))) => {
+        Some((filter, Verdict::Deny(reason))) => {
+            crate::blocks::record(registry.eco, &pkg, filter, &reason);
             Some(format!("{} {reason}", pkg.label()))
         }
         Some((filter, Verdict::Unknown(e))) if !firewall.config.fail_open => {

core/src/policies/registries/mod.rs

@@ -36,7 +36,7 @@ pub struct Pattern {
 }
 
 /// Requests to the local server match on `prefix`; intercepted URLs match on `upstream`.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub struct Registry {
     pub prefix: &'static str,
     pub eco: &'static str,
@@ -52,7 +52,7 @@ pub struct Registry {
 }
 
 /// A URL to fetch and a JSON pointer to the timestamp in its reply.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub struct Published {
     pub url: &'static str,
     pub pointer: &'static str,
@@ -63,11 +63,6 @@ impl Registry {
     pub fn host(&self) -> &'static str {
         host_of(self.upstream)
     }
-
-    /// What the config file calls it.
-    pub fn name(&self) -> &'static str {
-        self.prefix.trim_matches('/')
-    }
 }
 
 /// The host of an https:// URL, with the path dropped.

core/src/proxy/mod.rs

@@ -15,7 +15,7 @@ use std::sync::Arc;
 use tracing::{info, info_span, warn, Instrument};
 
 pub fn serve(config: FirewallConfig) -> std::io::Result<()> {
-    let bound = std::net::TcpListener::bind(("127.0.0.1", config.port.get()))?;
+    let bound = std::net::TcpListener::bind(("127.0.0.1", config.port))?;
     bound.set_nonblocking(true)?;
     crate::runtime()?.block_on(async move {
         let firewall = Arc::new(Firewall::new(config));

core/tests/config.rs

@@ -7,7 +7,7 @@ use firewall::{Firewall, FirewallConfig};
 fn a_file_only_has_to_set_what_it_changes() {
     let config: FirewallConfig = serde_json::from_str(r#"{"fail_open": false}"#).expect("parses");
     assert!(!config.fail_open);
-    assert_eq!(config.port.get(), firewall::DEFAULT_PORT);
+    assert_eq!(config.port, firewall::DEFAULT_PORT);
 }
 
 #[test]
@@ -15,28 +15,6 @@ fn a_misspelled_setting_is_an_error() {
     assert!(serde_json::from_str::<FirewallConfig>(r#"{"fail-open": false}"#).is_err());
 }
 
-#[test]
-fn nonsense_values_are_errors() {
-    let file = std::env::temp_dir().join(format!("firewall-nonsense-{}.json", std::process::id()));
-    for bad in [
-        r#"{"allow": {"nmp": [{"name": "left-pad"}]}}"#,
-        r#"{"denylist": {"poll_secs": 0}}"#,
-        r#"{"denylist": {"base": "raw.githubusercontent.com/usestrix"}}"#,
-        r#"{"denylist": {"revision": "https://"}}"#,
-        r#"{"port": 0}"#,
-        r#"{"min_age_hours": 18446744073709551615}"#,
-        r#"{"registries": {"npm": ["http://npm.example.com/"]}}"#,
-        r#"{"registries": {"npm": ["https://npm.example.com"]}}"#,
-        r#"{"registries": {"npm": ["https://npm.example.com:8443/"]}}"#,
-        r#"{"registries": {"npm": ["https://[email protected]/"]}}"#,
-        r#"{"registries": {"npm": ["https://npm.example.com/?a=/"]}}"#,
-    ] {
-        std::fs::write(&file, bad).expect("write");
-        assert!(FirewallConfig::load_from(std::slice::from_ref(&file)).is_err(), "{bad}");
-    }
-    std::fs::remove_file(&file).ok();
-}
-
 #[test]
 fn the_config_lives_under_the_config_directory() {
     let path = path().expect("a home directory");
@@ -60,21 +38,6 @@ fn a_later_file_wins_and_allow_lists_add_up() {
     assert_eq!(names, ["a", "b"]);
 }
 
-#[tokio::test]
-async fn a_mirror_is_screened_like_the_registry_it_copies() {
-    let config = r#"{"registries": {"npm": ["https://npm.example.com/"]}}"#;
-    let firewall = Firewall::new(serde_json::from_str(config).expect("parses"));
-    assert!(firewall.hosts().contains(&"npm.example.com"));
-    let url = "https://npm.example.com/left-pad/-/left-pad-1.3.0.tgz";
-    let (registry, rest) = firewall.match_on(url, |r| r.upstream).expect("the mirror");
-    assert_eq!(firewall.resolve(registry, rest).pkg.map(|p| p.label()), Some("[email protected]".into()));
-    let unknown = std::env::temp_dir().join(format!("firewall-mirror-{}.json", std::process::id()));
-    std::fs::write(&unknown, r#"{"registries": {"nmp": ["https://npm.example.com/"]}}"#).expect("write");
-    let loaded = FirewallConfig::load_from(std::slice::from_ref(&unknown));
-    std::fs::remove_file(&unknown).ok();
-    assert!(loaded.is_err());
-}
-
 #[tokio::test]
 async fn an_allowed_version_skips_the_filters() {
     // An unreachable denylist would otherwise leave the package unchecked.
@@ -94,3 +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"));
+}

docs/platforms.md

@@ -1,66 +0,0 @@
-# Platforms
-
-## Requirements
-
-| | Command prefix | Machine-wide |
-|---|---|---|
-| macOS | 13+, Apple silicon or Intel | Apple silicon, or an Intel Mac with a T2 chip |
-| Windows | 10 or 11, x86-64 | A TPM 2.0, and an admin to install |
-| Linux | glibc, x86-64 or arm64 | Not supported |
-
-There are no musl, 32-bit or Windows on Arm builds.
-
-`cargo install strix-firewall` installs only `firewall`. Add `--features machine-wide` for the
-machine-wide binaries, which otherwise come with the macOS app and the Windows MSI.
-
-## What is screened
-
-npm, pnpm, bun, pip, pip3, pipenv, pdm, uv, cargo, go and gem, downloading from:
-
-| Ecosystem | Hosts |
-|---|---|
-| npm | registry.npmjs.org |
-| PyPI | pypi.org, files.pythonhosted.org |
-| crates.io | index.crates.io, static.crates.io, crates.io |
-| RubyGems | rubygems.org |
-| Go | proxy.golang.org |
-
-Machine-wide screening also covers mirrors listed in the config file, under the registry they
-copy (`npm`, `pypi`, `pypi-files`, `cargo/index`, `cargo-dl`, `crates-api`, `gem` or `go`):
-`"registries": {"npm": ["https://npm.example.com/"]}`. A mirror must lay out its paths like that
-registry. `firewall <manager>` still sends managers to the public registries.
-
-## How machine-wide screening works
-
-Traffic to the hosts above is decrypted with a local CA that can only sign for those hosts. Its
-private key never leaves the Secure Enclave (macOS) or the TPM (Windows).
-
-- **macOS:** a system extension, which you approve in System Settings.
-- **Windows:** a service, with a hosts-file entry pointing each registry host at it.
-  - Without a TPM, the service can't start, so the install fails.
-  - Any signed-in user can pause screening from the notification-area icon, until they resume
-    it or the service restarts.
-  - Clients that use an HTTP proxy or their own DNS skip the hosts file and aren't screened.
-    Nor is WSL.
-  - Each client has to trust the CA:
-
-    | Client | Trusts it through |
-    |---|---|
-    | npm, pnpm, bun | `NODE_EXTRA_CA_CERTS`, set to `%ProgramData%\Strix Firewall\ca.pem` |
-    | uv | `UV_SYSTEM_CERTS`, which uses the Windows certificate store |
-    | pip, cargo | The Windows certificate store |
-    | gem, go | Untested |
-
-Tested on Windows 11 and Apple silicon only.
-
-## Changing settings
-
-Machine-wide screening reads an admin-only JSON file when it starts. After editing it, restart
-screening. An invalid file stops screening from starting.
-
-| OS | File | Restart from |
-|---|---|---|
-| macOS | `/Library/Application Support/Firewall/config.json` | The menu bar's Restart |
-| Windows | `%ProgramData%\Strix Firewall\config.json` | The notification-area icon's Restart |
-
-The `firewall` command reads `config.json` from the user's config folder instead.

macos/App/BlockAlerts.swift

@@ -0,0 +1,57 @@
+import AppKit
+import Security
+
+struct BlockedPackage: Codable, Hashable, Identifiable {
+    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" }
+    /// Malware is never allowed, and a new package only by version.
+    var trustable: Bool { !malicious && version != nil }
+}
+
+@MainActor
+enum BlockAlert {
+    /// 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 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)
+        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)\"'"
         }
@@ -51,6 +53,7 @@ final class FirewallModel: NSObject, ObservableObject {
     @Published private(set) var completed = false
     @Published private(set) var removed = false
     @Published private(set) var screening = false
+    @Published private(set) var blocked: [BlockedPackage] = []
 
     private let logger = Logger(subsystem: FirewallIDs.appBundleID, category: "installer")
     private var pendingRequest: (request: OSSystemExtensionRequest, continuation: CheckedContinuation<Void, Error>)?
@@ -72,6 +75,7 @@ final class FirewallModel: NSObject, ObservableObject {
             await refresh()
             if CommandLine.arguments.contains("--install") { await install() }
         }
+        Task { await watchBlocks() }
     }
 
     // MARK: - Flows
@@ -199,6 +203,43 @@ 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 {
+            if screening, let reply = try? await providerMessage("blocks"),
+               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) }
+                }
+                blocked = Array(blocked.suffix(10))
+            }
+            try? await Task.sleep(nanoseconds: 2_000_000_000)
+        }
+    }
+
     private func stage(_ step: ReferenceWritableKeyPath<FirewallModel, StepStatus>,
                        running: String,
                        work: @MainActor () async throws -> String) async -> Bool {

macos/App/MenuBarView.swift

@@ -22,5 +22,24 @@ struct MenuBarView: View {
             Task { await model.restart() }
         }
         .disabled(model.busy)
+
+        if !model.blocked.isEmpty {
+            Divider()
+            ForEach(model.blocked) { package in
+                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))") {
+                        Text("Malicious: \(package.reason)")
+                    }
+                }
+            }
+        }
     }
 }