Install machine-wide screening on Windows with an MSI

The MSI installs both binaries, registers and starts the service with a DACL that lets interactive users start, stop and pause it, restarts it on failure, and sets NODE_EXTRA_CA_CERTS and UV_SYSTEM_CERTS. Removing it runs `firewall-service.exe uninstall` once the service is deleted, which clears the hosts entries and removes the CA, its TPM key and the data folder but the config.
Move the macOS uninstall out of the CLI into its own binary (#56 )
2026-11-09 05:19:35 -10:00 · 2026-10-22 15:23:40 -04:00 · 2026-10-22 15:19:16 -04:00 · 2026-10-22 14:49:36 -04:00 · 2026-10-22 10:53:51 -04:00 · 2026-10-21 20:07:55 -04:00
20 changed files with 1305 additions and 37 deletions
@@ -172,6 +172,17 @@ dependencies = [
 "pin-project-lite",
 ]

+[[package]]
+name = "async-trait"
+version = "0.1.92"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82f6aeea286b8eb4dd3431a1be1b59d290ace00f5bfd8e2a159bc2a05e2c1667"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 3.0.6",
+]
+
 [[package]]
 name = "asynk-strim"
 version = "0.1.5"
@@ -456,6 +467,16 @@ dependencies = [
 "unicode-xid",
 ]

+[[package]]
+name = "core-foundation"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91e195e091a93c46f7102ec7818a2aa394e1e1771c3ab4825963fa03e45afb8f"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.10.1"
@@ -496,6 +517,12 @@ dependencies = [
 "cfg-if",
 ]

+[[package]]
+name = "critical-section"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "790eea4361631c5e7d22598ecd5723ff611904e3344ce8720784c93e3d83d40b"
+
 [[package]]
 name = "crossbeam-channel"
 version = "0.5.17"
@@ -997,6 +1024,78 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"

+[[package]]
+name = "hickory-net"
+version = "0.26.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c480823ed7c2c5d0f09c41020cb6b7c28029ce60ec42dc942158dcf22f8e0a4d"
+dependencies = [
+ "async-trait",
+ "cfg-if",
+ "data-encoding",
+ "futures-channel",
+ "futures-io",
+ "futures-util",
+ "hickory-proto",
+ "idna",
+ "ipnet",
+ "jni",
+ "rand",
+ "thiserror",
+ "tinyvec",
+ "tokio",
+ "tracing",
+ "url",
+]
+
+[[package]]
+name = "hickory-proto"
+version = "0.26.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "12b92608f679a6fa515dd1d15c1ff89443026e391200a2c840c7afcba482893d"
+dependencies = [
+ "data-encoding",
+ "idna",
+ "ipnet",
+ "jni",
+ "once_cell",
+ "prefix-trie",
+ "rand",
+ "ring",
+ "serde",
+ "thiserror",
+ "tinyvec",
+ "tracing",
+ "url",
+]
+
+[[package]]
+name = "hickory-resolver"
+version = "0.26.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f3da5255c95d5a716857d54b5b8f4e8d67c3484d3beaaaae2ce25063b3ba981"
+dependencies = [
+ "cfg-if",
+ "futures-util",
+ "hickory-net",
+ "hickory-proto",
+ "ipconfig",
+ "ipnet",
+ "jni",
+ "moka",
+ "ndk-context",
+ "once_cell",
+ "parking_lot",
+ "rand",
+ "resolv-conf",
+ "serde",
+ "smallvec",
+ "system-configuration",
+ "thiserror",
+ "tokio",
+ "tracing",
+]
+
 [[package]]
 name = "http"
 version = "1.5.0"
@@ -1158,6 +1257,19 @@ dependencies = [
 "hashbrown 0.17.1",
 ]

+[[package]]
+name = "ipconfig"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d40460c0ce33d6ce4b0630ad68ff63d6661961c48b6dba35e5a4d81cfb48222"
+dependencies = [
+ "socket2",
+ "widestring",
+ "windows-registry",
+ "windows-result",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "ipnet"
 version = "2.12.2"
@@ -1644,6 +1756,10 @@ name = "once_cell"
 version = "1.21.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9f7c3e4beb33f85d45ae3e3a1792185706c8e16d043238c593331cc7cd313b50"
+dependencies = [
+ "critical-section",
+ "portable-atomic",
+]

 [[package]]
 name = "once_cell_polyfill"
@@ -1778,6 +1894,17 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"

+[[package]]
+name = "prefix-trie"
+version = "0.8.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4cf6e3177f0684016a5c209b00882e15f8bdd3f3bb48f0491df10cd102d0c6e7"
+dependencies = [
+ "either",
+ "ipnet",
+ "num-traits",
+]
+
 [[package]]
 name = "prettyplease"
 version = "0.2.37"
@@ -2121,6 +2248,7 @@ dependencies = [
 "arc-swap",
 "base64",
 "bindgen",
+ "hickory-resolver",
 "libc",
 "moka",
 "parking_lot",
@@ -2419,7 +2547,7 @@ dependencies = [
 "base64",
 "bitflags 2.13.2",
 "const_format",
- "core-foundation",
+ "core-foundation 0.10.1",
 "csv",
 "idna",
 "ipnet",
@@ -2751,6 +2879,12 @@ version = "0.8.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d6f6ff9a378485b298a5286656da665ba74413d36db0979633275d2e708145d4"

+[[package]]
+name = "resolv-conf"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e061d1b48cb8d38042de4ae0a7a6401009d6143dc80d2e2d6f31f0bdd6470c7"
+
 [[package]]
 name = "ring"
 version = "0.17.14"
@@ -2886,7 +3020,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b7f4bc775c73d9a02cde8bf7b2ec4c9d12743edf609006c7facc23998404cd1d"
 dependencies = [
 "bitflags 2.13.2",
- "core-foundation",
+ "core-foundation 0.10.1",
 "core-foundation-sys",
 "libc",
 "security-framework-sys",
@@ -3094,13 +3228,14 @@ name = "strix-firewall"
 version = "0.1.0"
 dependencies = [
 "clap",
- "core-foundation",
+ "core-foundation 0.10.1",
 "directories",
 "percent-encoding",
 "rama",
 "rand",
 "rcgen",
 "regex",
+ "schannel",
 "security-framework",
 "security-framework-sys",
 "semver",
@@ -3109,8 +3244,12 @@ dependencies = [
 "time",
 "tokio",
 "tracing",
+ "tracing-appender",
 "tracing-subscriber",
 "which",
+ "windows",
+ "windows-registry",
+ "windows-service",
 ]

 [[package]]
@@ -3181,6 +3320,27 @@ dependencies = [
 "syn 3.0.6",
 ]

+[[package]]
+name = "system-configuration"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a13f3d0daba03132c0aa9767f98351b3488edc2c100cda2d2ec2b04f3d8d3c8b"
+dependencies = [
+ "bitflags 2.13.2",
+ "core-foundation 0.9.4",
+ "system-configuration-sys",
+]
+
+[[package]]
+name = "system-configuration-sys"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e1d1b10ced5ca923a1fcb8d03e96b8d3268065d724548c0211415ff6ac6bac4"
+dependencies = [
+ "core-foundation-sys",
+ "libc",
+]
+
 [[package]]
 name = "tagptr"
 version = "0.2.0"
@@ -3269,6 +3429,12 @@ dependencies = [
 "zerovec",
 ]

+[[package]]
+name = "tinyvec"
+version = "1.13.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd3ca314f692efd6c868f8408f53fe444634a845f96c028b97d35f6a1f79f0ee"
+
 [[package]]
 name = "tokio"
 version = "1.53.1"
@@ -3522,6 +3688,19 @@ version = "0.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ecb6da28b8a351d773b68d5825ac39017e680750f980f3a1a85cd8dd28a47c1"

+[[package]]
+name = "url"
+version = "2.5.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ff67a8a4397373c3ef660812acab3268222035010ab8680ec4215f38ba3d0eed"
+dependencies = [
+ "form_urlencoded",
+ "idna",
+ "percent-encoding",
+ "serde",
+ "serde_derive",
+]
+
 [[package]]
 name = "utf8_iter"
 version = "1.0.4"
@@ -3669,6 +3848,12 @@ dependencies = [
 "libc",
 ]

+[[package]]
+name = "widestring"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72069c3113ab32ab29e5584db3c6ec55d416895e60715417b5b883a357c3e471"
+
 [[package]]
 name = "wildcard"
 version = "0.3.0"
@@ -3709,12 +3894,100 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"

+[[package]]
+name = "windows"
+version = "0.62.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "527fadee13e0c05939a6a05d5bd6eec6cd2e3dbd648b9f8e447c6518133d8580"
+dependencies = [
+ "windows-collections",
+ "windows-core",
+ "windows-future",
+ "windows-numerics",
+]
+
+[[package]]
+name = "windows-collections"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23b2d95af1a8a14a3c7367e1ed4fc9c20e0a26e79551b1454d72583c97cc6610"
+dependencies = [
+ "windows-core",
+]
+
+[[package]]
+name = "windows-core"
+version = "0.62.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8e83a14d34d0623b51dce9581199302a221863196a1dde71a7663a4c2be9deb"
+dependencies = [
+ "windows-implement",
+ "windows-interface",
+ "windows-link",
+ "windows-result",
+ "windows-strings",
+]
+
+[[package]]
+name = "windows-future"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1d6f90251fe18a279739e78025bd6ddc52a7e22f921070ccdc67dde84c605cb"
+dependencies = [
+ "windows-core",
+ "windows-link",
+ "windows-threading",
+]
+
+[[package]]
+name = "windows-implement"
+version = "0.60.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "053e2e040ab57b9dc951b72c264860db7eb3b0200ba345b4e4c3b14f67855ddf"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
+[[package]]
+name = "windows-interface"
+version = "0.59.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3f316c4a2570ba26bbec722032c4099d8c8bc095efccdc15688708623367e358"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.119",
+]
+
 [[package]]
 name = "windows-link"
 version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f0805222e57f7521d6a62e36fa9163bc891acd422f971defe97d64e70d0a4fe5"

+[[package]]
+name = "windows-numerics"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e2e40844ac143cdb44aead537bbf727de9b044e107a0f1220392177d15b0f26"
+dependencies = [
+ "windows-core",
+ "windows-link",
+]
+
+[[package]]
+name = "windows-registry"
+version = "0.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "02752bf7fbdcce7f2a27a742f798510f3e5ad88dbe84871e5168e2120c3d5720"
+dependencies = [
+ "windows-link",
+ "windows-result",
+ "windows-strings",
+]
+
 [[package]]
 name = "windows-result"
 version = "0.4.1"
@@ -3724,6 +3997,26 @@ dependencies = [
 "windows-link",
 ]

+[[package]]
+name = "windows-service"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "857224b3b211c6f3616921f081ee54721ee3ad2ace2fac6a6337e032f7b4dcf2"
+dependencies = [
+ "bitflags 2.13.2",
+ "widestring",
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "windows-strings"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7837d08f69c77cf6b07689544538e017c1bfcf57e34b4c0ff58e6c2cd3b37091"
+dependencies = [
+ "windows-link",
+]
+
 [[package]]
 name = "windows-sys"
 version = "0.52.0"
@@ -3758,6 +4051,15 @@ dependencies = [
 "windows_x86_64_msvc",
 ]

+[[package]]
+name = "windows-threading"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3949bd5b99cafdf1c7ca86b43ca564028dfe27d66958f2470940f73d86d75b37"
+dependencies = [
+ "windows-link",
+]
+
 [[package]]
 name = "windows_aarch64_gnullvm"
 version = "0.52.6"
@@ -3,6 +3,7 @@ name = "strix-firewall"
 version = "0.1.0"
 edition = "2021"
 license = "Apache-2.0"
+authors = ["Strix"]
 description = "Screens package downloads for known malware before they reach your machine"
 repository = "https://github.com/usestrix/firewall"
 homepage = "https://github.com/usestrix/firewall"
@@ -10,6 +11,20 @@ homepage = "https://github.com/usestrix/firewall"
 # as an integration test; new tests/*.rs need an explicit [[test]] entry.
 autotests = false

+# Only Windows ships the service.
+[package.metadata.dist.binaries]
+x86_64-pc-windows-msvc = ["firewall", "firewall-service"]
+aarch64-apple-darwin = ["firewall"]
+x86_64-apple-darwin = ["firewall"]
+aarch64-unknown-linux-gnu = ["firewall"]
+x86_64-unknown-linux-gnu = ["firewall"]
+
+[package.metadata.wix]
+upgrade-guid = "D944C2F6-BF55-4B21-A60E-1BBDB1A66293"
+path-guid = "033B1050-23D0-4F5A-A0D3-F4757B4B67E0"
+license = false
+eula = false
+
 [lib]
 name = "firewall"
 # The macOS extension links a staticlib, built on demand:
@@ -20,6 +35,14 @@ crate-type = ["lib"]
 name = "firewall"
 path = "src/main.rs"

+[[bin]]
+name = "firewall-service"
+path = "src/bin/firewall-service.rs"
+
+[[bin]]
+name = "firewall-uninstall"
+path = "src/bin/firewall-uninstall.rs"
+
 [[example]]
 name = "proxy-test"
 path = "tests/proxy-test/main.rs"
@@ -52,6 +75,10 @@ path = "tests/age.rs"
 name = "mitm"
 path = "tests/mitm.rs"

+[[test]]
+name = "tpm"
+path = "tests/tpm.rs"
+
 [[test]]
 name = "managers"
 path = "tests/managers.rs"
@@ -79,6 +106,23 @@ rama = { version = "0.4.0", features = ["net-apple-networkextension"] }
 security-framework = "3.7.0"
 security-framework-sys = "2.17.0"

+[target.'cfg(windows)'.dependencies]
+rama = { version = "0.4.0", features = ["dns-hickory"] }
+schannel = "0.1.29"
+tokio = { version = "1.53.1", features = ["net"] }
+tracing-appender = "0.2.5"
+windows = { version = "0.62", features = [
+    "Win32_Foundation",
+    "Win32_Security",
+    "Win32_Security_Authorization",
+    "Win32_Security_Cryptography",
+    "Win32_System_Com",
+    "Win32_System_Environment",
+    "Win32_UI_Shell",
+] }
+windows-registry = "0.6.1"
+windows-service = "0.8.0"
+
 [dev-dependencies]
 tokio = { version = "1.53.1", features = ["macros", "rt-multi-thread"] }

@@ -0,0 +1,26 @@
+//! Started by the Windows service manager. It logs to a file, having no console.
+
+#[cfg(windows)]
+fn main() {
+    // Run by the MSI as it removes the firewall.
+    if std::env::args().nth(1).as_deref() == Some("uninstall") {
+        firewall::init_logging("info");
+        if let Err(e) = firewall::os::windows::uninstall() {
+            fail("uninstall", &format!("could not uninstall: {e}"))
+        }
+    } else if let Err(e) = firewall::os::windows::run_service() {
+        fail("service", &format!("could not run the service: {e}"))
+    }
+}
+
+#[cfg(windows)]
+fn fail(kind: &'static str, message: &str) -> ! {
+    tracing::error!("{message}");
+    firewall::telemetry::error(kind);
+    firewall::telemetry::flush();
+    std::process::exit(1)
+}
+
+/// The service is Windows-only.
+#[cfg(not(windows))]
+fn main() {}
@@ -0,0 +1,16 @@
+//! Run as root by the macOS app's uninstall.
+
+#[cfg(target_os = "macos")]
+fn main() {
+    firewall::init_logging("info");
+    if let Err(e) = firewall::os::macos::uninstall() {
+        tracing::error!("could not uninstall: {e}");
+        firewall::telemetry::error("uninstall");
+        firewall::telemetry::flush();
+        std::process::exit(1)
+    }
+}
+
+/// Only macOS installs anything system-wide.
+#[cfg(not(target_os = "macos"))]
+fn main() {}
@@ -12,10 +12,6 @@ fn main() {
        firewall::init_logging("info");
        serve()
    }
-    if matches.subcommand_matches("uninstall").is_some() {
-        firewall::init_logging("info");
-        uninstall()
-    }
    let mut command = matches.get_many::<String>("COMMAND").unwrap().cloned();
    let program = command.next().unwrap();
    firewall::init_logging("warn");
@@ -44,8 +40,6 @@ fn options() -> Command {
            Command::new("serve")
                .about("Serve a local registry for package managers configured to use it"),
        )
-        // Run as root by the macOS app's uninstall.
-        .subcommand(Command::new("uninstall").hide(true))
        .arg(
            Arg::new("COMMAND")
                .help("A command to run with its package downloads screened")
@@ -76,13 +70,6 @@ fn serve() -> ! {
    }
 }

-fn uninstall() -> ! {
-    match firewall::os::uninstall() {
-        Ok(()) => exit(0),
-        Err(e) => fail("uninstall", &format!("could not uninstall: {e}")),
-    }
-}
-
 fn run(invocation: Invocation) -> ! {
    telemetry::set_mode("wrapper");
    let command = &invocation.program;
@@ -8,7 +8,7 @@ use rcgen::{
 use std::sync::Arc;
 use time::{Duration, OffsetDateTime};

-/// Held in the Secure Enclave on macOS, in memory elsewhere.
+/// Held in the Secure Enclave on macOS, the TPM on Windows, in memory elsewhere.
 pub type CaSigner = Arc<dyn SigningKey + Send + Sync>;

 pub struct CertificateAuthority {
@@ -61,12 +61,14 @@ pub fn crl(hosts: &[&str], signer: &dyn SigningKey) -> Result<Vec<u8>, BoxError>
 }

 pub const COMMON_NAME: &str = "Strix Firewall";
+/// With `COMMON_NAME`, how a trust store entry is recognized as ours.
+pub const ORGANIZATION: &str = "Strix";

 /// Also used by the issuer, whose issuer name must match the CA's subject.
 pub fn params(hosts: &[&str]) -> CertificateParams {
    let mut name = DistinguishedName::new();
    name.push(DnType::CommonName, COMMON_NAME);
-    name.push(DnType::OrganizationName, "Strix");
+    name.push(DnType::OrganizationName, ORGANIZATION);

    let mut params = CertificateParams::default();
    params.distinguished_name = name;
@@ -3,7 +3,7 @@ mod issuer;
 mod route;
 mod screen;

-pub use ca::{crl, CaSigner, CertificateAuthority, COMMON_NAME};
+pub use ca::{crl, CaSigner, CertificateAuthority, COMMON_NAME, ORGANIZATION};

 use crate::Firewall;
 use issuer::ConstrainedCertIssuer;
@@ -1,16 +1,14 @@
 #[cfg(target_os = "macos")]
 pub mod macos;
+#[cfg(windows)]
+pub mod windows;

 #[cfg(target_os = "macos")]
-pub use macos::{system_config, uninstall};
+pub use macos::system_config;
+#[cfg(windows)]
+pub use windows::system_config;

-/// Elsewhere nothing is installed system-wide.
-#[cfg(not(target_os = "macos"))]
-pub fn uninstall() -> Result<(), rama::error::BoxError> {
-    Ok(())
-}
-
-#[cfg(not(target_os = "macos"))]
+#[cfg(not(any(target_os = "macos", windows)))]
 pub fn system_config() -> Option<std::path::PathBuf> {
    None
 }
@@ -0,0 +1,135 @@
+use super::*;
+use crate::mitm::{CertificateAuthority, COMMON_NAME, ORGANIZATION};
+use rama::tls::boring::core::nid::Nid;
+use rama::tls::boring::core::x509::X509;
+use rcgen::SigningKey;
+use schannel::cert_context::CertContext;
+use schannel::cert_store::{CertAdd, CertStore};
+use std::io;
+use std::path::Path;
+use std::time::{SystemTime, UNIX_EPOCH};
+use tracing::warn;
+use windows::Win32::Security::Authorization::{GetNamedSecurityInfoW, SE_FILE_OBJECT};
+use windows::Win32::Security::*;
+use windows_registry::Type;
+
+/// SYSTEM and admins write, users only read, so no one else can plant a CA for node.
+const DATA_DIR_ACL: &str = concat!(
+    "O:BA",               // owner: Administrators
+    "D:P",                // protected: ignore ProgramData's rules, which let any user create files
+    "(A;OICI;FA;;;SY)",   // allow SYSTEM full control, inherited by files (OI) and subfolders (CI)
+    "(A;OICI;FA;;;BA)",   // allow Administrators full control
+    "(A;OICI;FRFX;;;BU)", // allow Users read and execute only
+);
+
+/// 1970 in FILETIME, which counts 100 ns from 1601.
+const FILETIME_UNIX_EPOCH: u128 = 116_444_736_000_000_000;
+
+/// Trusted machine-wide so restarts keep it; replaced if the hosts change.
+pub fn load_or_create_ca(
+    hosts: &[&str],
+    signer: &dyn SigningKey,
+) -> Result<CertificateAuthority, BoxError> {
+    let stored = read_registry_string(REGISTRY_KEY, "ca")?;
+    let ca = match stored.and_then(|blob| CertificateAuthority::from_blob(&blob, hosts, signer)) {
+        Some(ca) => ca,
+        None => {
+            warn!(?hosts, "minting a new CA");
+            let ca = CertificateAuthority::generate(hosts, signer)?;
+            LOCAL_MACHINE
+                .create(REGISTRY_KEY)?
+                .set_string("ca", ca.to_blob(hosts))?;
+            // Windows discards CRLs it cached before now, in case an old CA's is cached at our URL.
+            let now = SystemTime::now().duration_since(UNIX_EPOCH)?.as_nanos() / 100
+                + FILETIME_UNIX_EPOCH;
+            let chain = r"SOFTWARE\Microsoft\Cryptography\OID\EncodingType 0\CertDllCreateCertificateChainEngine\Config";
+            let resync = (now as u64).to_le_bytes();
+            LOCAL_MACHINE.create(chain)?.set_bytes(
+                "ChainCacheResyncFiletime",
+                Type::Bytes,
+                &resync,
+            )?;
+            ca
+        }
+    };
+    // Idempotent, and the registry value can outlive the certificate.
+    let der = ca.crt.to_der()?;
+    let mut store = CertStore::open_local_machine("Root")?;
+    store.add_cert(&CertContext::new(&der)?, CertAdd::ReplaceExisting)?;
+    remove_our_cas_except(Some(&der))?;
+    // For clients that read no trust store; screening still works for the rest if this fails.
+    let exported = secure_data_dir().and_then(|dir| std::fs::write(dir.join("ca.pem"), &ca.pem));
+    if let Err(error) = exported {
+        warn!(%error, "could not export the CA");
+    }
+    Ok(ca)
+}
+
+/// Created on first use, its owner and ACL 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)?,
+        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::create_dir_all(&dir)?;
+    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()? };
+    Ok(dir)
+}
+
+/// By SYSTEM or the Administrators group, as what an elevated process creates is.
+fn owned_by_admins(path: &Path) -> windows::core::Result<bool> {
+    let (mut owner, mut descriptor) = (PSID::default(), PSECURITY_DESCRIPTOR::default());
+    unsafe {
+        GetNamedSecurityInfoW(
+            &HSTRING::from(path),
+            SE_FILE_OBJECT,
+            OWNER_SECURITY_INFORMATION,
+            Some(&mut owner),
+            None,
+            None,
+            None,
+            &mut descriptor,
+        )
+        .ok()?
+    };
+    let admins = [WinBuiltinAdministratorsSid, WinLocalSystemSid];
+    let owned = admins
+        .into_iter()
+        .any(|sid| unsafe { IsWellKnownSid(owner, sid) }.as_bool());
+    // `owner` points into the descriptor, so it is freed last.
+    unsafe { LocalFree(Some(HLOCAL(descriptor.0))) };
+    Ok(owned)
+}
+
+/// Drops every CA of ours from LocalMachine\Root but `keep`.
+pub(super) fn remove_our_cas_except(keep: Option<&[u8]>) -> Result<(), BoxError> {
+    for cert in CertStore::open_local_machine("Root")?.certs() {
+        if keep != Some(cert.to_der()) && is_our_ca(cert.to_der()) {
+            cert.delete()?;
+        }
+    }
+    Ok(())
+}
+
+fn is_our_ca(der: &[u8]) -> bool {
+    let Ok(crt) = X509::from_der(der) else {
+        return false;
+    };
+    let name = |nid| {
+        let entry = crt.subject_name().entries_by_nid(nid).next()?;
+        Some(entry.data().as_utf8().ok()?.to_string())
+    };
+    name(Nid::COMMONNAME).as_deref() == Some(COMMON_NAME)
+        && name(Nid::ORGANIZATIONNAME).as_deref() == Some(ORGANIZATION)
+}
@@ -0,0 +1,133 @@
+//! The hosts file sends each registry host to its own loopback address, where a
+//! LocalSystem service screens it as the macOS extension does.
+
+mod ca;
+mod service;
+mod tpm;
+mod uninstall;
+
+pub use service::run as run_service;
+pub use tpm::CaKey;
+pub use uninstall::uninstall;
+
+use rama::error::BoxError;
+use std::net::Ipv4Addr;
+use std::path::PathBuf;
+use windows::core::{Owned, GUID, HSTRING};
+use windows::Win32::Foundation::{LocalFree, ERROR_FILE_NOT_FOUND, HLOCAL};
+use windows::Win32::Security::Authorization::*;
+use windows::Win32::Security::PSECURITY_DESCRIPTOR;
+use windows::Win32::System::Com::CoTaskMemFree;
+use windows::Win32::System::Environment::ExpandEnvironmentStringsW;
+use windows::Win32::UI::Shell::*;
+use windows_registry::LOCAL_MACHINE;
+
+const SERVICE_NAME: &str = "StrixFirewall";
+/// Admin-only, so it holds the CA as the System keychain does on macOS.
+const REGISTRY_KEY: &str = r"SOFTWARE\Strix Firewall";
+/// Serves the CRL our leaves point at; schannel fails closed without one.
+const CRL_ADDRESS: Ipv4Addr = Ipv4Addr::new(127, 0, 0, 2);
+
+/// Admin-only; holds the exported CA, the service log and the config.
+fn data_dir() -> PathBuf {
+    known_folder(&FOLDERID_ProgramData).join("Strix Firewall")
+}
+
+/// Admin-only, so users cannot relax what the service screens.
+fn config_file() -> PathBuf {
+    data_dir().join("config.json")
+}
+
+pub fn system_config() -> Option<PathBuf> {
+    Some(config_file())
+}
+
+/// In the folder Windows reads it from, normally %SystemRoot%\System32\drivers\etc.
+fn hosts_file() -> PathBuf {
+    let key = r"SYSTEM\CurrentControlSet\Services\Tcpip\Parameters";
+    let configured = LOCAL_MACHINE
+        .open(key)
+        .and_then(|key| key.get_hstring("DataBasePath"));
+    let dir = match configured {
+        Ok(dir) => expand_environment(&dir),
+        Err(_) => known_folder(&FOLDERID_System).join(r"drivers\etc"),
+    };
+    dir.join("hosts")
+}
+
+/// Windows always has its known folders.
+fn known_folder(id: &GUID) -> PathBuf {
+    let path = unsafe { SHGetKnownFolderPath(id, KF_FLAG_DEFAULT, None) }.expect("a known folder");
+    let dir = PathBuf::from(unsafe { path.to_hstring() }.to_os_string());
+    unsafe { CoTaskMemFree(Some(path.0 as *const _)) };
+    dir
+}
+
+fn expand_environment(path: &HSTRING) -> PathBuf {
+    let len = unsafe { ExpandEnvironmentStringsW(path, None) };
+    let mut expanded = vec![0; len as usize];
+    let len = unsafe { ExpandEnvironmentStringsW(path, Some(&mut expanded)) };
+    // Less the terminating null.
+    PathBuf::from(String::from_utf16_lossy(
+        &expanded[..(len as usize).saturating_sub(1)],
+    ))
+}
+
+/// From 127.0.0.3, leaving 127.0.0.1 to whatever else serves locally.
+fn loopback_addresses(hosts: &[&'static str]) -> Vec<(Ipv4Addr, &'static str)> {
+    (3..)
+        .zip(hosts)
+        .map(|(i, host)| (Ipv4Addr::new(127, 0, 0, i), *host))
+        .collect()
+}
+
+/// Points each host at its listener, replacing the lines we wrote before; with none, only removes
+/// them. Bytes, as the file needn't be UTF-8, and every other line is kept as it was.
+fn write_hosts_entries(hosts: &[&'static str]) -> std::io::Result<()> {
+    const TAG: &str = " # Strix Firewall";
+    let old = std::fs::read(hosts_file())?;
+    let ours = |line: &&[u8]| line.trim_ascii_end().ends_with(TAG.as_bytes());
+    let lines = old.split_inclusive(|&byte| byte == b'\n');
+    let mut new: Vec<u8> = lines
+        .filter(|line| !ours(line))
+        .flatten()
+        .copied()
+        .collect();
+    if !new.is_empty() && !new.ends_with(b"\n") {
+        new.extend_from_slice(b"\r\n");
+    }
+    for (address, host) in loopback_addresses(hosts) {
+        new.extend_from_slice(format!("{address} {host}{TAG}\r\n").as_bytes());
+    }
+    std::fs::write(hosts_file(), new)
+}
+
+/// Parses `sddl`; freed on drop.
+fn security_descriptor(sddl: &str) -> windows::core::Result<Owned<HLOCAL>> {
+    let mut descriptor = PSECURITY_DESCRIPTOR::default();
+    unsafe {
+        ConvertStringSecurityDescriptorToSecurityDescriptorW(
+            &HSTRING::from(sddl),
+            SDDL_REVISION_1,
+            &mut descriptor,
+            None,
+        )?
+    };
+    Ok(unsafe { Owned::new(HLOCAL(descriptor.0)) })
+}
+
+fn read_registry_string(key: &str, value: &str) -> Result<Option<String>, BoxError> {
+    none_if_missing(
+        LOCAL_MACHINE
+            .open(key)
+            .and_then(|key| key.get_string(value)),
+    )
+}
+
+/// `None` for a missing key or value.
+fn none_if_missing<T>(result: windows_registry::Result<T>) -> Result<Option<T>, BoxError> {
+    match result {
+        Err(error) if error.code() == ERROR_FILE_NOT_FOUND.to_hresult() => Ok(None),
+        result => Ok(Some(result?)),
+    }
+}
@@ -0,0 +1,234 @@
+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 crate::config::FirewallConfig;
+use crate::http::{reply, text};
+use crate::{mitm, telemetry, Firewall};
+use rama::dns::client::hickory::resolver::config::ResolveHosts;
+use rama::dns::client::hickory::{default_resolver_opts, HickoryDnsResolver};
+use rama::dns::client::resolver::DnsAddressResolver;
+use rama::dns::client::try_init_global_dns_resolver;
+use rama::error::BoxError;
+use rama::http::server::HttpServer;
+use rama::http::{Request, Response};
+use rama::io::BridgeIo;
+use rama::layer::ConsumeErrLayer;
+use rama::net::address::Domain;
+use rama::rt::Executor;
+use rama::service::service_fn;
+use rama::tcp::server::TcpListener;
+use rama::tcp::TcpStream;
+use rama::{Layer, Service};
+use rcgen::SigningKey;
+use std::convert::Infallible;
+use std::ffi::OsString;
+use std::net::{IpAddr, Ipv4Addr};
+use std::sync::Arc;
+use std::time::Duration;
+use tracing_appender::rolling::{RollingFileAppender, Rotation};
+use windows_service::service::*;
+use windows_service::service_control_handler::{
+    self, ServiceControlHandlerResult, ServiceStatusHandle,
+};
+use windows_service::{define_windows_service, service_dispatcher};
+
+const CRL_PATH: &str = "/ca.crl";
+
+define_windows_service!(ffi_service_main, service_main);
+
+/// Called by the service control manager, never by hand.
+pub fn run() -> windows_service::Result<()> {
+    service_dispatcher::start(SERVICE_NAME, ffi_service_main)
+}
+
+/// stderr goes nowhere in a service, so events go to a file beside the CA.
+fn service_main(_arguments: Vec<OsString>) {
+    let log = secure_data_dir().ok().and_then(|dir| {
+        RollingFileAppender::builder()
+            .rotation(Rotation::DAILY)
+            .filename_prefix("firewall")
+            .filename_suffix("log")
+            .max_log_files(7)
+            .build(dir)
+            .ok()
+    });
+    if let Some(appender) = log {
+        let filter = crate::log_filter("info");
+        let _ = tracing_subscriber::fmt()
+            .with_env_filter(filter)
+            .with_ansi(false)
+            .with_writer(appender)
+            .try_init();
+    }
+    std::panic::set_hook(Box::new(|panic| tracing::error!("{panic}")));
+    if let Err(error) = run_until_stopped() {
+        tracing::error!(%error, "the service stopped");
+    }
+}
+
+fn run_until_stopped() -> Result<(), BoxError> {
+    let (control_sender, mut control_receiver) = tokio::sync::mpsc::unbounded_channel();
+    let status = service_control_handler::register(SERVICE_NAME, move |control| match control {
+        ServiceControl::Stop
+        | ServiceControl::Shutdown
+        | ServiceControl::Pause
+        | ServiceControl::Continue => {
+            let _ = control_sender.send(control);
+            ServiceControlHandlerResult::NoError
+        }
+        ServiceControl::Interrogate => ServiceControlHandlerResult::NoError,
+        _ => ServiceControlHandlerResult::NotImplemented,
+    })?;
+    set_status(&status, ServiceState::StartPending, false)?;
+    let served = crate::runtime()?.block_on(async {
+        let hosts = match start_screening(&status).await {
+            Ok(hosts) => hosts,
+            Err(error) => {
+                telemetry::send().await;
+                return Err(error);
+            }
+        };
+        // Only pausing removes our hosts entries; a stop or crash keeps them, failing closed.
+        while let Some(control) = 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"),
+            }
+        }
+        Ok::<_, BoxError>(())
+    });
+    // A failed stop is what makes the service manager restart it.
+    set_status(&status, ServiceState::Stopped, served.is_err())?;
+    served
+}
+
+async fn start_screening(status: &ServiceStatusHandle) -> Result<Vec<&'static str>, BoxError> {
+    telemetry::set_mode("service");
+    telemetry::heartbeat();
+    // Never the hosts file, which points back at us; the Firewall's lookups included.
+    let mut options = default_resolver_opts();
+    options.use_hosts_file = ResolveHosts::Never;
+    let resolver = HickoryDnsResolver::try_new_system_with_options(options)?;
+    let _ = try_init_global_dns_resolver(resolver.clone());
+    let config =
+        FirewallConfig::load_from(&[config_file()]).inspect_err(|_| telemetry::error("config"))?;
+    let firewall = Arc::new(Firewall::new(config));
+    let hosts = firewall.hosts();
+    let key = CaKey::load_or_create().inspect_err(|_| telemetry::error("tpm"))?;
+    let signer: mitm::CaSigner = Arc::new(key);
+    let ca = load_or_create_ca(&hosts, &*signer).inspect_err(|_| telemetry::error("ca"))?;
+    let exec = Executor::default();
+
+    // An empty CRL for the leaves to point at, signed fresh for each fetch.
+    let crl_url = format!("http://{CRL_ADDRESS}{CRL_PATH}");
+    let (crl_hosts, crl_signer) = (hosts.clone(), Arc::clone(&signer));
+    let crl = service_fn(move |req: Request| {
+        let response = if req.uri().request_target() == CRL_PATH {
+            crl_response(&crl_hosts, &*crl_signer)
+        } else {
+            text(404, "No route.\n")
+        };
+        async move { Ok::<_, Infallible>(response) }
+    });
+    let crl = HttpServer::auto(exec.clone()).service(crl);
+    tokio::spawn(listen_on(CRL_ADDRESS, 80, &exec)?.serve(crl));
+
+    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] {
+            let upstream = RedirectedHost {
+                host,
+                port,
+                resolver: resolver.clone(),
+                service: service.clone(),
+            };
+            let upstream = ConsumeErrLayer::trace_as_debug().into_layer(upstream);
+            tokio::spawn(listen_on(address, port, &exec)?.serve(upstream));
+        }
+    }
+    // Rewritten on every start, so a restart picks up a changed host list.
+    write_hosts_entries(&hosts)?;
+    tracing::info!(?hosts, "screening redirected registry traffic");
+    set_status(status, ServiceState::Running, false)?;
+    Ok(hosts)
+}
+
+fn crl_response(hosts: &[&str], signer: &dyn SigningKey) -> Response {
+    match mitm::crl(hosts, signer) {
+        Ok(der) => reply(200, "application/pkix-crl", der),
+        Err(error) => text(503, &format!("{error}\n")),
+    }
+}
+
+fn listen_on(address: Ipv4Addr, port: u16, exec: &Executor) -> std::io::Result<TcpListener> {
+    let bound = std::net::TcpListener::bind((address, port))?;
+    bound.set_nonblocking(true)?;
+    TcpListener::try_from_std_tcp_listener(bound, exec.clone())
+}
+
+/// Each listener is bound to one host's address, which is how it knows where to connect.
+#[derive(Clone)]
+struct RedirectedHost {
+    host: &'static str,
+    port: u16,
+    resolver: HickoryDnsResolver,
+    service: mitm::MitmService,
+}
+
+impl Service<TcpStream> for RedirectedHost {
+    type Output = ();
+    type Error = BoxError;
+
+    async fn serve(&self, ingress: TcpStream) -> Result<(), BoxError> {
+        let address = self.resolve().await?;
+        let egress = tokio::net::TcpStream::connect((address, self.port)).await?;
+        let streams = BridgeIo(ingress, TcpStream::from(egress));
+        self.service.serve(streams).await
+    }
+}
+
+impl RedirectedHost {
+    /// IPv4 if it has one, else IPv6.
+    async fn resolve(&self) -> Result<IpAddr, BoxError> {
+        let domain = Domain::from_static(self.host);
+        if let Some(Ok(v4)) = self.resolver.lookup_ipv4_first(domain.clone()).await {
+            return Ok(v4.into());
+        }
+        match self.resolver.lookup_ipv6_first(domain).await {
+            Some(v6) => Ok(v6?.into()),
+            None => Err(format!("{} has no address", self.host).into()),
+        }
+    }
+}
+
+fn set_status(
+    status: &ServiceStatusHandle,
+    state: ServiceState,
+    failed: bool,
+) -> windows_service::Result<()> {
+    status.set_service_status(ServiceStatus {
+        service_type: ServiceType::OWN_PROCESS,
+        current_state: state,
+        controls_accepted: match state {
+            ServiceState::Running | ServiceState::Paused => {
+                ServiceControlAccept::STOP
+                    | ServiceControlAccept::SHUTDOWN
+                    | ServiceControlAccept::PAUSE_CONTINUE
+            }
+            _ => ServiceControlAccept::empty(),
+        },
+        exit_code: if failed {
+            ServiceExitCode::ServiceSpecific(1)
+        } else {
+            ServiceExitCode::Win32(0)
+        },
+        checkpoint: 0,
+        wait_hint: Duration::from_secs(30),
+        process_id: None,
+    })
+}
@@ -0,0 +1,160 @@
+use rama::error::BoxError;
+use rama::tls::boring::core::bn::BigNum;
+use rama::tls::boring::core::ecdsa::EcdsaSig;
+use rama::tls::boring::core::sha::sha256;
+use rcgen::{Error, PublicKeyData, SignatureAlgorithm, SigningKey, PKCS_ECDSA_P256_SHA256};
+use windows::core::{Owned, Result as WinResult, HSTRING};
+use windows::Win32::Foundation::{NTE_BAD_KEY, NTE_BAD_KEYSET};
+use windows::Win32::Security::Cryptography::*;
+
+const KEY_NAME: &str = "Strix Firewall CA";
+
+/// A P-256 key held by the TPM. Signing asks the TPM to sign, so the private key never leaves it.
+pub struct CaKey {
+    // Fields drop in order, so the key handle closes before its provider's.
+    key_handle: Owned<NCRYPT_KEY_HANDLE>,
+    _provider_handle: Owned<NCRYPT_PROV_HANDLE>,
+    /// 0x04 || X || Y, the form rcgen writes into a certificate's SubjectPublicKeyInfo.
+    public_point: Vec<u8>,
+}
+
+impl CaKey {
+    /// A machine key, so the service and an elevated installer share it.
+    pub fn load_or_create() -> Result<Self, BoxError> {
+        match open_key(KEY_NAME, NCRYPT_MACHINE_KEY_FLAG)? {
+            Some(key) => Ok(key),
+            None => Ok(create_key(KEY_NAME, NCRYPT_MACHINE_KEY_FLAG)?),
+        }
+    }
+
+    pub(super) fn delete_machine_key() -> Result<(), BoxError> {
+        if let Some(key) = open_key(KEY_NAME, NCRYPT_MACHINE_KEY_FLAG)? {
+            key.delete_from_tpm()?;
+        }
+        Ok(())
+    }
+
+    /// A per-user key under a random name, which needs no elevation; `delete_from_tpm` it after.
+    pub fn create_test_key() -> WinResult<Self> {
+        let name = format!("Strix Firewall test {:016x}", rand::random::<u64>());
+        create_key(&name, NCRYPT_FLAGS(0))
+    }
+
+    /// Deletes the key from the TPM, not just this handle to it.
+    pub fn delete_from_tpm(mut self) -> WinResult<()> {
+        // NCryptDeleteKey also frees the handle, so the Owned mustn't free it again.
+        let key_handle = std::mem::take(&mut *self.key_handle);
+        unsafe { NCryptDeleteKey(key_handle, 0) }
+    }
+
+    /// Takes both handles and reads the key's public point once, for rcgen.
+    fn from_handles(
+        provider_handle: Owned<NCRYPT_PROV_HANDLE>,
+        key_handle: Owned<NCRYPT_KEY_HANDLE>,
+    ) -> WinResult<Self> {
+        // A BCRYPT_ECCKEY_BLOB header, then X and Y.
+        const HEADER_LEN: usize = size_of::<BCRYPT_ECCKEY_BLOB>();
+        let mut blob = [0u8; HEADER_LEN + 64];
+        let mut blob_len = 0;
+        unsafe {
+            NCryptExportKey(
+                *key_handle,
+                None,
+                BCRYPT_ECCPUBLIC_BLOB,
+                None,
+                Some(&mut blob),
+                &mut blob_len,
+                NCRYPT_FLAGS(0),
+            )?
+        };
+        let (header, x_and_y) = blob.split_at(HEADER_LEN);
+        let is_p256 = header[..4] == BCRYPT_ECDSA_PUBLIC_P256_MAGIC.to_le_bytes();
+        if !is_p256 || blob_len as usize != blob.len() {
+            return Err(windows::core::Error::new(NTE_BAD_KEY, "key is not an ECDSA P-256 key"));
+        }
+        let public_point = [&[0x04], x_and_y].concat();
+        Ok(CaKey { key_handle, _provider_handle: provider_handle, public_point })
+    }
+}
+
+impl PublicKeyData for CaKey {
+    fn der_bytes(&self) -> &[u8] {
+        &self.public_point
+    }
+
+    fn algorithm(&self) -> &'static SignatureAlgorithm {
+        &PKCS_ECDSA_P256_SHA256
+    }
+}
+
+impl SigningKey for CaKey {
+    fn sign(&self, msg: &[u8]) -> Result<Vec<u8>, Error> {
+        let mut r_and_s = [0u8; 64];
+        let mut signature_len = 0;
+        let signed = unsafe {
+            NCryptSignHash(
+                *self.key_handle,
+                None,
+                &sha256(msg),
+                Some(&mut r_and_s),
+                &mut signature_len,
+                NCRYPT_SILENT_FLAG,
+            )
+        };
+        signed.map_err(|_| Error::RemoteKeyError)?;
+        // NCrypt returns r || s, each half the length; X.509 wants DER SEQUENCE { r, s }.
+        let (r, s) = r_and_s[..signature_len as usize].split_at(signature_len as usize / 2);
+        let der = BigNum::from_slice(r)
+            .and_then(|r| EcdsaSig::from_private_components(r, BigNum::from_slice(s)?))
+            .and_then(|signature| signature.to_der());
+        der.map_err(|_| Error::RemoteKeyError)
+    }
+}
+
+/// `None` if the TPM holds no key by that name.
+/// `scope` is `NCRYPT_MACHINE_KEY_FLAG`, or empty for the current user's keys.
+fn open_key(name: &str, scope: NCRYPT_FLAGS) -> WinResult<Option<CaKey>> {
+    let provider_handle = open_tpm_provider()?;
+    let mut key_handle = NCRYPT_KEY_HANDLE::default();
+    let opened = unsafe {
+        NCryptOpenKey(
+            *provider_handle,
+            &mut key_handle,
+            &HSTRING::from(name),
+            CERT_KEY_SPEC::default(), // legacy, unused by the TPM provider
+            scope | NCRYPT_SILENT_FLAG,
+        )
+    };
+    match opened {
+        Err(error) if error.code() == NTE_BAD_KEYSET => Ok(None),
+        Err(error) => Err(error),
+        Ok(()) => CaKey::from_handles(provider_handle, unsafe { Owned::new(key_handle) }).map(Some),
+    }
+}
+
+/// Generates the key inside the TPM, which never lets it out.
+fn create_key(name: &str, scope: NCRYPT_FLAGS) -> WinResult<CaKey> {
+    let provider_handle = open_tpm_provider()?;
+    let mut key_handle = NCRYPT_KEY_HANDLE::default();
+    unsafe {
+        NCryptCreatePersistedKey(
+            *provider_handle,
+            &mut key_handle,
+            NCRYPT_ECDSA_P256_ALGORITHM,
+            &HSTRING::from(name),
+            CERT_KEY_SPEC::default(), // legacy, unused by the TPM provider
+            scope,
+        )?
+    };
+    let key_handle = unsafe { Owned::new(key_handle) };
+    // Until finalized the key is only a handle; this generates and stores it.
+    unsafe { NCryptFinalizeKey(*key_handle, NCRYPT_SILENT_FLAG)? };
+    CaKey::from_handles(provider_handle, key_handle)
+}
+
+/// The Microsoft Platform Crypto Provider, which keeps its keys in the TPM.
+fn open_tpm_provider() -> WinResult<Owned<NCRYPT_PROV_HANDLE>> {
+    let mut provider_handle = NCRYPT_PROV_HANDLE::default();
+    unsafe { NCryptOpenStorageProvider(&mut provider_handle, MS_PLATFORM_CRYPTO_PROVIDER, 0)? };
+    Ok(unsafe { Owned::new(provider_handle) })
+}
@@ -0,0 +1,41 @@
+use super::ca::remove_our_cas_except;
+use super::tpm::CaKey;
+use super::*;
+use std::io::ErrorKind;
+use std::path::Path;
+use tracing::info;
+
+/// Run by the MSI after it deletes the service, which would restore the hosts entries. Does
+/// nothing for what is already gone.
+pub fn uninstall() -> Result<(), BoxError> {
+    write_hosts_entries(&[])?;
+    remove_our_cas_except(None)?;
+    none_if_missing(LOCAL_MACHINE.remove_tree(REGISTRY_KEY))?;
+    CaKey::delete_machine_key()?;
+    let entries = match std::fs::read_dir(data_dir()) {
+        Err(error) if error.kind() == ErrorKind::NotFound => Vec::new(),
+        entries => entries?.collect::<Result<Vec<_>, _>>()?,
+    };
+    for path in entries.into_iter().map(|entry| entry.path()) {
+        // The admin's config stays for a reinstall, as on macOS.
+        if path != config_file() {
+            remove_path(&path)?;
+        }
+    }
+    // Fails while the config is in it.
+    let _ = std::fs::remove_dir(data_dir());
+    info!("removed the CA, its key and the data folder");
+    Ok(())
+}
+
+/// A file or a folder, if it is there.
+fn remove_path(path: &Path) -> std::io::Result<()> {
+    let removed = match path.is_dir() {
+        true => std::fs::remove_dir_all(path),
+        false => std::fs::remove_file(path),
+    };
+    match removed {
+        Err(error) if error.kind() == ErrorKind::NotFound => Ok(()),
+        removed => removed,
+    }
+}
@@ -30,7 +30,7 @@ static TELEMETRY: LazyLock<Option<Telemetry>> = LazyLock::new(|| {
    })
 });

-/// How the firewall is running: "extension", "wrapper" or "proxy".
+/// How the firewall is running: "extension", "service", "wrapper" or "proxy".
 static MODE: OnceLock<&'static str> = OnceLock::new();

 struct Telemetry {
@@ -0,0 +1,21 @@
+#![cfg(windows)]
+
+use firewall::mitm::CertificateAuthority;
+use firewall::os::windows::CaKey;
+use rcgen::PublicKeyData;
+
+/// Skipped on machines without a TPM.
+#[test]
+fn key_signs_a_verifiable_ca() {
+    let key = match CaKey::create_test_key() {
+        Ok(key) => key,
+        Err(error) => return eprintln!("skipping, no TPM key: {error}"),
+    };
+    let ca = CertificateAuthority::generate(&["registry.npmjs.org"], &key);
+    let spki = key.subject_public_key_info();
+    key.delete_from_tpm().expect("delete the test key");
+    let ca = ca.expect("mint a ca");
+    let public = ca.crt.public_key().expect("ca public key");
+    assert!(ca.crt.verify(&public).expect("verify the ca"));
+    assert_eq!(public.public_key_to_der().unwrap(), spki);
+}
@@ -0,0 +1,167 @@
+<?xml version='1.0' encoding='windows-1252'?>
+<!--
+  Copyright (C) 2017 Christopher R. Field.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+
+<?if $(sys.BUILDARCH) = x64 or $(sys.BUILDARCH) = arm64 ?>
+    <?define PlatformProgramFilesFolder = "ProgramFiles64Folder" ?>
+<?else ?>
+    <?define PlatformProgramFilesFolder = "ProgramFilesFolder" ?>
+<?endif ?>
+
+<Wix xmlns='http://schemas.microsoft.com/wix/2006/wi'>
+
+    <Product
+        Id='*'
+        Name='strix-firewall'
+        UpgradeCode='D944C2F6-BF55-4B21-A60E-1BBDB1A66293'
+        Manufacturer='Strix'
+        Language='1033'
+        Codepage='1252'
+        Version='$(var.Version)'>
+
+        <Package Id='*'
+            Keywords='Installer'
+            Description='Screens package downloads for known malware before they reach your machine'
+            Manufacturer='Strix'
+            InstallerVersion='500'
+            Languages='1033'
+            Compressed='yes'
+            InstallScope='perMachine'
+            SummaryCodepage='1252'
+            />
+
+        <MajorUpgrade
+            Schedule='afterInstallInitialize'
+            DowngradeErrorMessage='A newer version of [ProductName] is already installed. Setup will now exit.'/>
+
+        <Media Id='1' Cabinet='media1.cab' EmbedCab='yes' DiskPrompt='CD-ROM #1'/>
+        <Property Id='DiskPrompt' Value='strix-firewall Installation'/>
+
+        <Directory Id='TARGETDIR' Name='SourceDir'>
+            <Directory Id='$(var.PlatformProgramFilesFolder)' Name='PFiles'>
+                <Directory Id='APPLICATIONFOLDER' Name='Strix Firewall'>
+                    <Component Id='Path' Guid='033B1050-23D0-4F5A-A0D3-F4757B4B67E0' KeyPath='yes'>
+                        <Environment
+                            Id='PATH'
+                            Name='PATH'
+                            Value='[APPLICATIONFOLDER]'
+                            Permanent='no'
+                            Part='last'
+                            Action='set'
+                            System='yes'/>
+                    </Component>
+                    <Component Id='binary0' Guid='*'>
+                        <File
+                            Id='exe0'
+                            Name='firewall.exe'
+                            DiskId='1'
+                            Source='$(var.CargoTargetBinDir)\firewall.exe'
+                            KeyPath='yes'/>
+                    </Component>
+                    <Component Id='binary1' Guid='*'>
+                        <File
+                            Id='exe1'
+                            Name='firewall-service.exe'
+                            DiskId='1'
+                            Source='$(var.CargoTargetBinDir)\firewall-service.exe'
+                            KeyPath='yes'/>
+                        <ServiceInstall
+                            Name='StrixFirewall'
+                            DisplayName='Strix Firewall'
+                            Description='Screens package downloads for known malware'
+                            Type='ownProcess'
+                            Start='auto'
+                            ErrorControl='normal'
+                            Vital='yes'>
+                            <!-- The default, except that interactive users (IU) may also start (RP), stop (WP) and pause (DT) it, as the tray does. -->
+                            <PermissionEx Sddl='D:(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCLCSWRPWPDTLOCRRC;;;IU)(A;;CCLCSWLOCRRC;;;SU)'/>
+                        </ServiceInstall>
+                        <!-- Waits, so a service that cannot start fails the install. -->
+                        <ServiceControl Id='StrixFirewall' Name='StrixFirewall' Start='install' Stop='both' Remove='uninstall' Wait='yes'/>
+                        <!-- For clients that read no trust store. SSL_CERT_FILE would replace OpenSSL's bundle. -->
+                        <Environment Id='NODE_EXTRA_CA_CERTS' Name='NODE_EXTRA_CA_CERTS' Value='[CommonAppDataFolder]Strix Firewall\ca.pem' Action='set' System='yes'/>
+                        <Environment Id='UV_SYSTEM_CERTS' Name='UV_SYSTEM_CERTS' Value='1' Action='set' System='yes'/>
+                    </Component>
+                </Directory>
+            </Directory>
+        </Directory>
+
+        <Feature
+            Id='Binaries'
+            Title='Application'
+            Description='Installs the firewall and its service.'
+            Level='1'
+            ConfigurableDirectory='APPLICATIONFOLDER'
+            AllowAdvertise='no'
+            Display='expand'
+            Absent='disallow'>
+            <ComponentRef Id='binary0'/>
+            <ComponentRef Id='binary1'/>
+
+            <Feature
+                Id='Environment'
+                Title='PATH Environment Variable'
+                Description='Add the install location of the [ProductName] executable to the PATH system environment variable. This allows the [ProductName] executable to be called from any location.'
+                Level='1'
+                Absent='allow'>
+                <ComponentRef Id='Path'/>
+            </Feature>
+        </Feature>
+
+        <!-- Removing the app must not leave the hosts file pointing at a service that is gone. -->
+        <CustomAction
+            Id='UninstallFirewall'
+            FileKey='exe1'
+            ExeCommand='uninstall'
+            Execute='deferred'
+            Impersonate='no'
+            Return='check'/>
+        <!--
+          Registry hosts lead nowhere while the service is down, so bring it back, also when it fails to
+          start. Through sc.exe, as MsiServiceConfigFailureActions cannot restart a service.
+        -->
+        <CustomAction
+            Id='SetFailureActions'
+            Directory='APPLICATIONFOLDER'
+            ExeCommand='"[System64Folder]sc.exe" failure StrixFirewall reset= 3600 actions= restart/5000/restart/5000/restart/5000'
+            Execute='deferred'
+            Impersonate='no'
+            Return='check'/>
+        <CustomAction
+            Id='SetFailureFlag'
+            Directory='APPLICATIONFOLDER'
+            ExeCommand='"[System64Folder]sc.exe" failureflag StrixFirewall 1'
+            Execute='deferred'
+            Impersonate='no'
+            Return='check'/>
+        <InstallExecuteSequence>
+            <!-- An upgrade removes the old version too, but should keep screening. -->
+            <Custom Action='UninstallFirewall' After='DeleteServices'>REMOVE~="ALL" AND NOT UPGRADINGPRODUCTCODE</Custom>
+            <Custom Action='SetFailureActions' After='InstallServices'>NOT REMOVE~="ALL"</Custom>
+            <Custom Action='SetFailureFlag' After='SetFailureActions'>NOT REMOVE~="ALL"</Custom>
+        </InstallExecuteSequence>
+
+        <SetProperty Id='ARPINSTALLLOCATION' Value='[APPLICATIONFOLDER]' After='CostFinalize'/>
+        <Property Id='ARPHELPLINK' Value='https://github.com/usestrix/firewall'/>
+
+        <UI>
+            <UIRef Id='WixUI_FeatureTree'/>
+            <Publish Dialog='WelcomeDlg' Control='Next' Event='NewDialog' Value='CustomizeDlg' Order='99'>1</Publish>
+            <Publish Dialog='CustomizeDlg' Control='Back' Event='NewDialog' Value='WelcomeDlg' Order='99'>1</Publish>
+        </UI>
+    </Product>
+
+</Wix>
@@ -4,7 +4,9 @@ members = ["cargo:core"]
 [dist]
 cargo-dist-version = "0.32.0"
 ci = "github"
-installers = ["shell", "powershell", "homebrew"]
+installers = ["shell", "powershell", "homebrew", "msi"]
+# core/wix/main.wxs is edited to install the service.
+allow-dirty = ["msi"]
 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"]
@@ -280,10 +280,10 @@ final class FirewallModel: NSObject, ObservableObject {
        return true
    }

-    /// The extension wrote these as root, so the bundled CLI removes them behind an admin prompt; returns what to report if it failed.
+    /// The extension wrote these as root, so the bundled firewall-uninstall removes them behind an admin prompt; returns what to report if it failed.
    private func removeStoredCA() -> String? {
-        let cli = Bundle.main.path(forAuxiliaryExecutable: "firewall") ?? ""
-        let script = "do shell script quoted form of \"\(cli)\" & \" uninstall\" with administrator privileges"
+        let uninstaller = Bundle.main.path(forAuxiliaryExecutable: "firewall-uninstall") ?? ""
+        let script = "do shell script quoted form of \"\(uninstaller)\" with administrator privileges"
        var error: NSDictionary?
        NSAppleScript(source: script)?.executeAndReturnError(&error)
        if let error {
@@ -55,7 +55,7 @@ sign() {
  echo "==> Signing with $IDENTITY"
  cp "$(profile_for $APP_ID)" "$APP/Contents/embedded.provisionprofile"
  cp "$(profile_for $EXT_ID)" "$EXT/Contents/embedded.provisionprofile"
-  codesign --force --options runtime --timestamp -s "$IDENTITY" "$APP/Contents/MacOS/firewall"
+  codesign --force --options runtime --timestamp -s "$IDENTITY" "$APP/Contents/MacOS/firewall-uninstall"
  codesign --force --options runtime --timestamp \
    --entitlements Extension/Extension.entitlements -s "$IDENTITY" "$EXT"
  codesign --force --options runtime --timestamp \
@@ -118,14 +118,14 @@ targets:
      - target: Extension
        embed: true
        codeSign: true
-    # Uninstall runs the CLI as root to remove what the extension left.
+    # Uninstall runs this as root to remove what the extension left.
    postBuildScripts:
-      - name: Embed the CLI
+      - name: Embed firewall-uninstall
        basedOnDependencyAnalysis: false
        script: |
          export PATH="$HOME/.cargo/bin:$PATH"
          unset CC CXX CFLAGS CXXFLAGS
          export SDKROOT="$(xcrun --sdk macosx --show-sdk-path)"
          cd "$SRCROOT/../core"
-          cargo build --bin firewall --target aarch64-apple-darwin $([ "$CONFIGURATION" = Debug ] || echo --release)
-          cp "target/aarch64-apple-darwin/$CARGO_PROFILE/firewall" "$TARGET_BUILD_DIR/$EXECUTABLE_FOLDER_PATH/"
+          cargo build --bin firewall-uninstall --target aarch64-apple-darwin $([ "$CONFIGURATION" = Debug ] || echo --release)
+          cp "target/aarch64-apple-darwin/$CARGO_PROFILE/firewall-uninstall" "$TARGET_BUILD_DIR/$EXECUTABLE_FOLDER_PATH/"
Author	SHA1	Message	Date
Ian	10fdd0f272	Install machine-wide screening on Windows with an MSI The MSI installs both binaries, registers and starts the service with a DACL that lets interactive users start, stop and pause it, restarts it on failure, and sets NODE_EXTRA_CA_CERTS and UV_SYSTEM_CERTS. Removing it runs `firewall-service.exe uninstall` once the service is deleted, which clears the hosts entries and removes the CA, its TPM key and the data folder but the config.	2026-10-22 15:23:40 -04:00
ian-at-strix	bdcc2e93dc	Move the macOS uninstall out of the CLI into its own binary (#56 )	2026-10-22 15:19:16 -04:00
ian-at-strixandIan Graham Martinez	9e457c4d69	Screen redirected registry traffic in a Windows service (#10 ) * Screen redirected registry traffic in a Windows service Each registry host gets its own loopback address, where a LocalSystem service serves mitm_service, connecting upstream through a resolver that ignores the hosts file. It trusts its CA machine-wide and serves the empty CRL that schannel needs. The service writes the hosts-file block once it listens. Pausing it removes the block and continuing rewrites it; a stop, crash or shutdown leaves it, so a restart fails closed and picks up a changed host list. * Explain the data folder ACL and the root store arguments * Use schannel for the root store * Free the parsed security descriptor on drop instead of through a closure * Rotate the service log daily with tracing-appender --------- Co-authored-by: Ian Graham Martinez <[email protected]>	2026-10-22 14:49:36 -04:00
ian-at-strixandIan Graham Martinez	7cafa16cc4	Hold the CA key in the TPM on Windows (#9 ) * Hold the CA key in the TPM on Windows A non-exportable machine key in the TPM, or in software where there is none, signs as the Secure Enclave key does on macOS. * Require the TPM for the Windows CA key A failure to open the TPM fell back to a software key, which minted a new CA and kept it for good. Fail instead, as macOS does without a Secure Enclave. * Use the windows crate for the TPM key --------- Co-authored-by: Ian Graham Martinez <[email protected]>	2026-10-22 10:53:51 -04:00
ian-at-strix	38d9a4500e	Layer a system config over the user's, and have the extension read only the system one (#43 )	2026-10-21 20:07:55 -04:00