bootstrap: verify signatures

Cargo.lock

@@ -91,6 +91,12 @@ dependencies = [
  "windows-targets",
 ]
 
+[[package]]
+name = "base64"
+version = "0.22.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
+
 [[package]]
 name = "bitflags"
 version = "2.9.1"
@@ -225,8 +231,9 @@ dependencies = [
 
 [[package]]
 name = "init"
-version = "2.4.0"
+version = "2.4.1"
 dependencies = [
+ "base64",
  "cpio",
  "env_logger",
  "eyre",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "init"
-version = "2.4.0"
+version = "2.4.1"
 edition = "2024"
 
 [profile.release]
@@ -28,3 +28,4 @@ zstd = "0.13.3"
 unix_mode = "0.1.4"
 cpio = "0.4.1"
 lz4 = "1.28.1"
+base64 = "0.22.1"

Dockerfile

@@ -19,7 +19,7 @@ run . /etc/os-release \
 
 run apk add --no-cache --update -p . musl coreutils \
  lvm2 lvm2-extra lvm2-dmeventd udev cryptsetup \
- e2fsprogs lsblk openssh-server wireguard-tools-wg-quick \
+ e2fsprogs lsblk openssl openssh-server wireguard-tools-wg-quick \
  && rm -rf usr/share/apk var/cache/apk etc/motd
 
 copy etc/sshd_config etc/ssh/sshd_config
@@ -36,7 +36,7 @@ run mkdir -p bin run var/log; cd bin && for cmd in init-version init-connect boo
 # check viability
 run chroot . init-version
 
-run find |cpio -H newc -o >/initrd
+run find * |cpio -H newc -oF /initrd
 
 # ------------------------------------------------------------------------
 from alpine:3.22.0

build-test-initrd

@@ -0,0 +1,21 @@
+#! /bin/bash
+
+dir=tmp/test-initrd
+base_initrd=dist/initrd
+test_initrd=test-initrd
+
+set -ex
+
+rm -fr $dir
+mkdir $dir
+
+cpio --quiet --extract --file $base_initrd --directory $dir
+(cd $test_initrd && find * |cpio --quiet --create -H newc) |cpio --quiet --extract --directory $dir
+
+(cd $dir && find * |cpio --create -H newc -R 0:0) >test-initrd.cpio
+
+cpio --quiet -tF test-initrd.cpio
+if cpio -tF test-initrd.cpio 2>&1 |grep bytes.of.junk; then echo "bad cpio archive"; exit 1; fi
+
+lz4 -l9v test-initrd.cpio && mv test-initrd.cpio.lz4 test-initrd.cpio
+

modd.test.conf

@@ -1,9 +1,6 @@
 modd.test.conf {}
 
-dist/initrd test-initrd/**/* {
+dist/initrd build-test-initrd test-initrd/**/* {
-    prep: cp -f dist/initrd test-initrd.cpio
+    prep: ./build-test-initrd
-    prep: cd test-initrd && find |cpio -oAv -H newc -F ../test-initrd.cpio
-    prep: lz4 -l9v test-initrd.cpio && mv test-initrd.cpio.lz4 test-initrd.cpio
-    prep: if lz4cat test-initrd.cpio | cpio -t 2>&1 |grep bytes.of.junk; then echo "bad cpio archive"; exit 1; fi
     prep: kill $(<qemu.pid)
 }

src/bootstrap/config.rs

@@ -30,6 +30,9 @@ pub struct Config {
     #[serde(default)]
     pub crypt: Vec<CryptDev>,
 
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub signer_public_key: Option<String>,
+
     pub bootstrap: Bootstrap,
 }
 

src/cmd/init.rs

@@ -257,10 +257,19 @@ async fn mount(src: Option<&str>, dst: &str, fstype: &str, opts: Option<&str>) {
         error!("failed to create dir {dst}: {e}");
     }
 
+    let mut is_file = false;
+
     if let Some(src) = src {
+        retry_or_ignore(async || {
+            is_file = (fs::metadata(src).await)
+                .map_err(|e| format_err!("stat {src} failed: {e}"))?
+                .is_file();
+            Ok(())
+        })
+        .await;
         match fstype {
             "ext4" => {
-                exec("fsck", &["-p", src]).await;
+                exec("fsck.ext4", &["-p", src]).await;
             }
             _ => {}
         }
@@ -272,13 +281,11 @@ async fn mount(src: Option<&str>, dst: &str, fstype: &str, opts: Option<&str>) {
     }
 
     retry_or_ignore(async || {
-        // check source, use a loopdev if needed
+        // if it's a file, we need to use a loopdev
-        if let Some(src) = src {
+        if is_file {
-            if fs::metadata(src).await?.is_file() {
             // loopdev crate has annoying dependencies, just use the normal mount program
             return try_exec("mount", &args).await;
         }
-        }
 
         let (cmd_str, _) = cmd_str("mount", &args);
         let flags = nix::mount::MsFlags::empty();

src/cmd/init/bootstrap.rs

@@ -11,10 +11,10 @@ use crate::bootstrap::config::Config;
 use crate::{dkl, utils};
 
 pub async fn bootstrap(cfg: Config) {
+    let verifier = retry(async || Verifier::from_config(&cfg)).await;
     let bs = cfg.bootstrap;
 
     retry_or_ignore(async || {
-        fs::create_dir_all("/boostrap").await?;
         mount(Some(&bs.dev), "/bootstrap", "ext4", None).await;
         Ok(())
     })
@@ -33,12 +33,12 @@ pub async fn bootstrap(cfg: Config) {
     .await;
 
     let sys_cfg: dkl::Config = retry(async || {
-        let sys_cfg_bytes = seed_config(base_dir, &bs.seed).await?;
+        let sys_cfg_bytes = seed_config(base_dir, &bs.seed, &verifier).await?;
         Ok(serde_yaml::from_slice(&sys_cfg_bytes)?)
     })
     .await;
 
-    mount_system(&sys_cfg, base_dir).await;
+    mount_system(&sys_cfg, base_dir, &verifier).await;
 
     retry_or_ignore(async || {
         let path = "/etc/resolv.conf";
@@ -68,7 +68,67 @@ pub async fn bootstrap(cfg: Config) {
     exec("chroot", &["/system", "update-ca-certificates"]).await
 }
 
-async fn seed_config(base_dir: &str, seed_url: &Option<String>) -> Result<Vec<u8>> {
+struct Verifier {
+    pubkey: Option<Vec<u8>>,
+}
+impl Verifier {
+    fn from_config(cfg: &Config) -> Result<Self> {
+        let Some(ref pubkey) = cfg.signer_public_key else {
+            return Ok(Self { pubkey: None });
+        };
+
+        use base64::{prelude::BASE64_STANDARD, Engine};
+        let pubkey = BASE64_STANDARD.decode(pubkey)?;
+        let pubkey = Some(pubkey);
+
+        return Ok(Self { pubkey });
+    }
+
+    async fn verify_path(&self, path: &str) -> Result<()> {
+        let Some(ref pubkey) = self.pubkey else {
+            return Ok(());
+        };
+
+        info!("verifying {path}");
+
+        let mut pubkey = std::io::Cursor::new(pubkey);
+
+        let sig = format!("{path}.sig");
+
+        use std::process::Stdio;
+        use tokio::process::Command;
+
+        let mut openssl = Command::new("openssl")
+            .stdin(Stdio::piped())
+            .args(&[
+                "dgst",
+                "-sha512",
+                "-verify",
+                "/dev/stdin",
+                "-signature",
+                &sig,
+                path,
+            ])
+            .spawn()?;
+
+        tokio::io::copy(&mut pubkey, openssl.stdin.as_mut().unwrap()).await?;
+
+        let status = openssl.wait().await?;
+        if status.success() {
+            Ok(())
+        } else {
+            Err(format_err!(
+                "signature verification failed for {path}: {status}"
+            ))
+        }
+    }
+}
+
+async fn seed_config(
+    base_dir: &str,
+    seed_url: &Option<String>,
+    verifier: &Verifier,
+) -> Result<Vec<u8>> {
     let cfg_path = &format!("{base_dir}/config.yaml");
 
     if fs::try_exists(cfg_path).await? {
@@ -92,6 +152,8 @@ async fn seed_config(base_dir: &str, seed_url: &Option<String>) -> Result<Vec<u8
         return Err(format_err!("{cfg_path} does not exist after seeding"));
     }
 
+    verifier.verify_path(&cfg_path).await?;
+
     Ok(fs::read(cfg_path).await?)
 }
 
@@ -107,7 +169,7 @@ async fn fetch_bootstrap(seed_url: &str, output_file: &str) -> Result<()> {
     Ok(())
 }
 
-async fn mount_system(cfg: &dkl::Config, bs_dir: &str) {
+async fn mount_system(cfg: &dkl::Config, bs_dir: &str, verifier: &Verifier) {
     let mem_dir = "/mem";
     mount(None, mem_dir, "tmpfs", Some("size=512m")).await;
 
@@ -116,14 +178,17 @@ async fn mount_system(cfg: &dkl::Config, bs_dir: &str) {
 
     for layer in &cfg.layers {
         let src = if layer == "modules" {
-            "/modules.sqfs"
+            "/modules.sqfs".to_string()
         } else {
-            &format!("{bs_dir}/{layer}.fs")
+            let p = format!("{bs_dir}/{layer}.fs");
+            retry(async || verifier.verify_path(&p).await).await;
+            p
         };
+
         let tgt = &format!("{mem_dir}/{layer}.fs");
         retry(async || {
             info!("copying layer {layer} from {src}");
-            fs::copy(src, tgt).await?;
+            fs::copy(&src, tgt).await?;
             Ok(())
         })
         .await;

test-initrd/config.yaml

@@ -21,6 +21,8 @@ auths:
     sshKey:   ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAICkpbU6sf4t0f6XAv9DuW3XH5iLM0AI5rc8PT2jwea1N
     password: bXlzZWVk:HMSxrg1cYphaPuUYUbtbl/htep/tVYYIQAuvkNMVpw0 # mypass
 
+signer_public_key: MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQA29glSqk7MqoUIjD+UQG+b4v59pTFkn8rYtNhOftTe7uiLUvGFsjNdzP3tW64t/c6YD2p6dtI3oQXGOVQO1vIWPEBc6Sq++BRpQ0FVna+dgNQx8/kLXN9Na0ZYbK7q0haCI7/EHWOX79JFFxJE9HJ67AOMmXwGJ2jrfa1CUnWvfCmT+E=
+
 ssh:
   listen: "[::]:22"
   user_ca: /user_ca.pub