WIP

server/.gitignore

@@ -3,3 +3,6 @@ container-baby.js
 
 # cache, will move later
 cache/
+
+# jailer
+jailer/

server/index.js

@@ -1,11 +1,13 @@
 import { delay } from "nanodelay";
-import { nanoid } from "nanoid";
+import { customAlphabet as nanoidCustomAlphabet, nanoid } from "nanoid";
+import which from "which";
 import { spawn, execFile as _execFile } from "node:child_process";
 import { createServer, request as _request } from "node:http";
 import { tmpdir } from "node:os";
-import { join } from "node:path";
+import { basename, join } from "node:path";
 import { downloadImage, parseImageRef } from "./container-baby.js";
 import { promisify } from "node:util";
+import { access, chmod, chown, link, mkdir } from "node:fs/promises";
 const execFile = promisify(_execFile);
 
 const server = createServer(listener);
@@ -55,52 +57,115 @@ async function runVm(image) {
  * @prop {boolean} is_read_only
  */
 
+/**
+ * gets absolute path to firecracker executable
+ * @returns {Promise<string>}
+ */
+async function getFirecrackerExe() {
+  const firecrackerExe = await which("firecracker", { nothrow: true });
+  console.debug(
+    `[fireactions] Using firecracker executable '${firecrackerExe}'`
+  );
+  return firecrackerExe;
+}
+
+const jailerDir = "./jailer";
+const [jailerUid, jailerGid] = [65534, 65534];
+
+// we need to use a custom alphabet because jailer is picky
+const jailerNanoid = nanoidCustomAlphabet(
+  "0123456789abcdefghijklmnopqrstuvwxyz-",
+  64
+);
+
 class FirecrackerInstance {
-  proc;
+  vmid;
   socketPath;
-  constructor() {
-    const vmid = nanoid();
-    this.socketPath = join(tmpdir(), `firecracker-${vmid}.sock`);
+  proc;
+  /**
+   * @param {{ firecrackerExe: string }} param0
+   * @private
+   */
+  constructor({ firecrackerExe }) {
+    this.vmid = jailerNanoid();
+    this.socketPath = join(this.chrootPath, `firecracker.sock`);
     console.debug(this.socketPath);
-    // TODO: jailer
     this.proc = spawn(
-      "firecracker",
+      "jailer",
       [
-        ...["--api-sock", this.socketPath],
-        ...["--level", "Debug"],
-        ...["--log-path", "/dev/stderr"],
-        "--show-level",
-        "--show-log-origin",
+        ...["--id", this.vmid],
+        ...["--exec-file", firecrackerExe],
+        ...["--uid", "" + jailerUid],
+        ...["--gid", "" + jailerGid],
+        ...["--chroot-base-dir", jailerDir],
+        "--",
+        ...["--api-sock", "/firecracker.sock"],
+        // ...["--level", "Debug"],
+        // ...["--log-path", "/stderr.log"],
+        // "--show-level",
+        // "--show-log-origin",
       ],
       {
         stdio: "inherit",
       }
     );
+
+    console.debug(
+      `[fireactions] Started firecracker with jailer at ${this.chrootPath}`
+    );
   }
+
+  get chrootPath() {
+    return join(jailerDir, "firecracker", this.vmid, "root");
+  }
+
+  /**
+   * @param {string} path path to file to hardlink to root of chroot
+   * @param {number} mod mod inside the chroot
+   */
+  async hardlinkToChroot(path, mod = 0o600) {
+    const chrootPath = join(this.chrootPath, basename(path));
+    let accesed = false;
+    try {
+      await access(chrootPath);
+      accesed = true;
+    } catch {}
+    if (accesed)
+      throw new Error("file with same name already exists inside chroot");
+    await link(path, chrootPath);
+    await chown(chrootPath, jailerUid, jailerGid);
+    await chmod(chrootPath, mod);
+  }
+
   /**
    * @param [opts] {{ drives?: Drive[] }}
    */
   static async run(opts) {
-    const self = new FirecrackerInstance();
+    await mkdir(jailerDir, { recursive: true });
+    const self = new FirecrackerInstance({
+      firecrackerExe: await getFirecrackerExe(),
+    });
+    await mkdir(self.chrootPath, { recursive: true });
     // TODO: retry until success
     await delay(15);
 
     const { ifname, hostAddr, guestAddr } = await createNetworkInterface();
 
+    await self.hardlinkToChroot("../vmlinux.bin", 0o400);
     await self.request("PUT", "/boot-source", {
-      kernel_image_path: "../vmlinux.bin",
+      kernel_image_path: "/vmlinux.bin",
       boot_args: `console=ttyS0 reboot=k panic=1 pci=off fireactions_ip=${guestAddr}:${hostAddr}`,
     });
-    await self.request("PUT", "/drives/rootfs", {
+    // TODO: readonly
+    self.attachDrive({
       drive_id: "rootfs",
-      path_on_host: "../rootfs.ext4",
+      path_on_host: "/rootfs.ext4",
       is_root_device: true,
-      // TODO: readonly
       is_read_only: false,
     });
     if (opts?.drives) {
       for (const drive of opts.drives) {
-        await self.request("PUT", "/drives/" + drive.drive_id, drive);
+        await self.attachDrive(drive);
       }
     }
     await self.request("PUT", "/network-interfaces/eth0", {
@@ -119,6 +184,18 @@ class FirecrackerInstance {
     });
   }
 
+  /**
+   * @param {Drive} drive
+   */
+  async attachDrive(drive) {
+    const perms = drive.is_read_only ? 0o400 : 0o600;
+    await this.hardlinkToChroot(drive.path_on_host, perms);
+    await this.request("PUT", "/drives/" + drive.drive_id, {
+      ...drive,
+      path_on_host: "/" + basename(drive.path_on_host),
+    });
+  }
+
   /**
    * @param {string} method
    * @param {string} path

server/package.json

@@ -5,7 +5,7 @@
   "description": "",
   "main": "index.js",
   "scripts": {
-    "start": "esbuild --bundle index.js --platform=node --sourcemap > build.cjs && sudo node --enable-source-maps build.cjs"
+    "start": "esbuild --bundle index.js --platform=node --sourcemap > build.cjs && sudo env PATH=\"$PATH:$HOME/.local/bin\" node --enable-source-maps build.cjs"
   },
   "keywords": [],
   "author": "",
@@ -15,12 +15,14 @@
     "@types/gunzip-maybe": "^1.4.0",
     "@types/node": "^20.2.5",
     "@types/tar-stream": "^2.2.2",
+    "@types/which": "^3.0.0",
     "undici": "^5.22.1"
   },
   "dependencies": {
     "gunzip-maybe": "^1.4.2",
     "nanodelay": "^2.0.2",
     "nanoid": "^4.0.2",
-    "tar-stream": "^3.0.0"
+    "tar-stream": "^3.0.0",
+    "which": "^3.0.1"
   }
 }

server/pnpm-lock.yaml

@@ -17,6 +17,9 @@ dependencies:
   tar-stream:
     specifier: ^3.0.0
     version: 3.0.0
+  which:
+    specifier: ^3.0.1
+    version: 3.0.1
 
 devDependencies:
   '@tsconfig/node16':
@@ -31,6 +34,9 @@ devDependencies:
   '@types/tar-stream':
     specifier: ^2.2.2
     version: 2.2.2
+  '@types/which':
+    specifier: ^3.0.0
+    version: 3.0.0
   undici:
     specifier: ^5.22.1
     version: 5.22.1
@@ -57,6 +63,10 @@ packages:
       '@types/node': 20.2.5
     dev: true
 
+  /@types/which@3.0.0:
+    resolution: {integrity: sha512-ASCxdbsrwNfSMXALlC3Decif9rwDMu+80KGp5zI2RLRotfMsTv7fHL8W8VDp24wymzDyIFudhUeSCugrgRFfHQ==}
+    dev: true
+
   /abort-controller@3.0.0:
     resolution: {integrity: sha512-h8lQ8tacZYnR3vNQTgibj+tODHI5/+l06Au2Pcriv/Gmet0eaj4TwWH41sO9wnHDiQsEj19q0drzdWdeAHtweg==}
     engines: {node: '>=6.5'}
@@ -170,6 +180,10 @@ packages:
     resolution: {integrity: sha512-VLghIWNM6ELQzo7zwmcg0NmTVyWKYjvIeM83yjp0wRDTmUnrM678fQbcKBo6n2CJEF0szoG//ytg+TKla89ALQ==}
     dev: false
 
+  /isexe@2.0.0:
+    resolution: {integrity: sha512-RHxMLp9lnKHGHRng9QFhRCMbYAcVpn69smSGcq3f36xjgVVWThj4qqLbTLlq7Ssj8B+fIQ1EuCEGI2lKsyQeIw==}
+    dev: false
+
   /nanodelay@2.0.2:
     resolution: {integrity: sha512-6AS5aCSXsjoxq2Jr9CdaAeT60yoYDOTp6po9ziqeOeY6vf6uTEHYSqWql6EFILrM3fEfXgkZ4KqE9L0rTm/wlA==}
     engines: {node: ^12.0.0 || ^14.0.0 || >=16.0.0}
@@ -301,6 +315,14 @@ packages:
     resolution: {integrity: sha512-EPD5q1uXyFxJpCrLnCc1nHnq3gOa6DZBocAIiI2TaSCA7VCJ1UJDMagCzIkXNsUYfD1daK//LTEQ8xiIbrHtcw==}
     dev: false
 
+  /which@3.0.1:
+    resolution: {integrity: sha512-XA1b62dzQzLfaEOSQFTCOd5KFf/1VSzZo7/7TUjnya6u0vGGKzU96UQBZTAThCb2j4/xjBAyii1OhRLJEivHvg==}
+    engines: {node: ^14.17.0 || ^16.13.0 || >=18.0.0}
+    hasBin: true
+    dependencies:
+      isexe: 2.0.0
+    dev: false
+
   /wrappy@1.0.2:
     resolution: {integrity: sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ==}
     dev: false

server/tar2squashfs.js

@@ -2,6 +2,8 @@
 // TODO: sandboxear mkquashfs
 // TODO: fijarse como hace firecracker-containerd
 // TODO: fijarse como hace [ignite](https://github.com/weaveworks/ignite)
+// TODO: fijarse como hace [thi](https://github.com/thi-startup/init)
+// TODO: fijarse como hace [firebuild](https://combust-labs.github.io/firebuild-docs/)
 
 import gunzip from "gunzip-maybe";
 import { spawn } from "node:child_process";