modules/fail2ban/Dockerfile

@@ -1,23 +0,0 @@
-# fail2ban's runtime: the tool runtime, carrying the intrusion prevention's verbs and the client they
-# speak through.
-#
-# Built from this module's own directory and nothing else (novox/hq ADR 0069). Two bases, named in
-# module.json's `build.on`: the image this is compiled in and the image it runs in.
-ARG BUILD_BASE
-ARG RUNTIME_BASE
-
-FROM ${BUILD_BASE} AS build
-WORKDIR /app/modules/fail2ban
-COPY . .
-RUN node /app/node_modules/typescript/bin/tsc client.ts tools/index.ts \
-      --module NodeNext --moduleResolution NodeNext --target ES2022 --outDir dist
-
-FROM ${RUNTIME_BASE}
-# The daemon runs on the machine, declared by this module; what runs here is only its client, which
-# speaks to the daemon over the socket the machine shares into this container (novox/hq ADR 0179).
-# The package brings the client and the daemon together; the daemon is never started here.
-RUN apt-get update \
-      && apt-get install -y --no-install-recommends fail2ban \
-      && rm -rf /var/lib/apt/lists/*
-COPY --from=build /app/modules/fail2ban/dist /app/modules/fail2ban/dist
-ENV MESH_TOOL_MODULES=/app/modules/fail2ban/dist/tools/index.js

modules/fail2ban/client.ts

@@ -5,12 +5,15 @@
 // prevention seat's four verbs (ADR 0179). The daemon's state is fail2ban's, not the mesh's: the
 // mesh composes the jails and never writes the ban list.
 //
-// Spoken through fail2ban-client over the daemon's socket, which the machine shares into this
-// runtime; so the client here is the one from the runtime's own package and the daemon is the
-// machine's, and the two meet at /var/run/fail2ban/fail2ban.sock.
+// Spoken through fail2ban-client over the daemon's socket. Client and daemon come from the one
+// package this module declares on the machine, and the socket is root's: root is the module's
+// concern (ADR 0175 §4), and the runtime loading this bundle runs as the operator's account (to-be
+// 38 WP4), so the client is run through sudo without a prompt where the account is not root.
 
 import { execFile } from "node:child_process";
+import { accessSync, constants } from "node:fs";
 import { isIP } from "node:net";
+import { delimiter, join } from "node:path";
 import { promisify } from "node:util";
 
 const execFileP = promisify(execFile);
@@ -18,16 +21,44 @@ const execFileP = promisify(execFile);
 /** A command runner, so the verbs can be tested without a daemon. */
 export type Runner = (cmd: string, args: string[]) => Promise<string>;
 
+/** The command as it is run: as given when this process is root, else through sudo without a
+ *  prompt. The daemon's socket answers only to root. */
+export function escalated(cmd: string, args: string[], uid: number | undefined = process.getuid?.()): [string, string[]] {
+  if (uid === 0) return [cmd, args];
+  return ["sudo", ["-n", cmd, ...args]];
+}
+
+/** Whether a tool is on this machine: an executable of that name on the path, or where the
+ *  system keeps its administration. */
+export function installed(tool: string, path: string = process.env.PATH ?? ""): boolean {
+  const dirs = [...path.split(delimiter), "/usr/sbin", "/sbin", "/usr/bin"].filter((d) => d !== "");
+  return dirs.some((dir) => {
+    try {
+      accessSync(join(dir, tool), constants.X_OK);
+      return true;
+    } catch {
+      return false;
+    }
+  });
+}
+
 export const execRunner: Runner = async (cmd, args) => {
+  if (!installed(cmd)) throw new Error(`${cmd} is not installed on this machine`);
+  const [program, argv] = escalated(cmd, args);
   try {
-    const { stdout } = await execFileP(cmd, args, { maxBuffer: 16 * 1024 * 1024 });
+    const { stdout } = await execFileP(program, argv, { maxBuffer: 16 * 1024 * 1024 });
     return stdout;
   } catch (err) {
     const e = err as { code?: string | number; stderr?: string; stdout?: string; message?: string };
     const said = `${e.stdout ?? ""}${e.stderr ?? ""}`.trim();
-    if (e.code === "ENOENT") throw new Error(`${cmd} is not in this runtime`);
-    if (/Failed to access socket path|Is fail2ban running/i.test(said)) {
-      throw new Error("fail2ban is not running on this machine, or its socket is not shared with this runtime");
+    // What failed is named by how it failed: sudo missing is a spawn error, sudo refusing speaks
+    // on its own stderr line, and the rest is the client's own answer.
+    if (program === "sudo") {
+      if (e.code === "ENOENT") throw new Error(`${cmd} needs root, and sudo is not installed here for the runtime's account to escalate with`);
+      if (/^sudo:/m.test(said)) throw new Error(`${cmd} needs root and the runtime's account may not run it without a prompt: ${said}`);
+    }
+    if (/Failed to access socket path|Is fail2ban running|Permission denied to socket/i.test(said)) {
+      throw new Error("fail2ban is not running on this machine, or its socket does not answer the runtime's account");
     }
     // fail2ban-client's own last line is the one a person reads ("Sorry but the jail 'x' does not exist").
     const lines = said.split("\n").map((l) => l.trim()).filter(Boolean);
@@ -76,7 +107,8 @@ export class Fail2banClient {
     this.run = run;
   }
 
-  static fromEnv(_env: NodeJS.ProcessEnv = process.env): Fail2banClient {
+  /** The daemon as this machine has it, through its own client. */
+  static onThisMachine(): Fail2banClient {
     return new Fail2banClient();
   }
 

modules/fail2ban/module.json

@@ -19,9 +19,6 @@
   "tools": [
     "fail2ban_settings"
   ],
-  "own-secrets": {
-    "broker": "${dir:mesh-state}/broker"
-  },
   "jailing": {
     "into": "/etc/fail2ban/jail.d/mesh.conf",
     "filter-into": "/etc/fail2ban/filter.d"
@@ -56,12 +53,6 @@
       "path": "/var/run/fail2ban",
       "mode": "0755"
     },
-    {
-      "id": "mesh-state",
-      "type": "directory",
-      "mode": "0700",
-      "place": "mesh"
-    },
     {
       "id": "jail-local",
       "type": "file",
@@ -118,40 +109,17 @@
         "action-dualchain",
         "composed-jails"
       ]
-    },
-    {
-      "id": "runtime",
-      "type": "container",
-      "name": "mesh-fail2ban",
-      "artifact": "runtime",
-      "network": "host",
-      "volumes": [
-        "${dir:mesh-state}/broker:/run/secrets/broker:ro",
-        "/var/run/fail2ban:/var/run/fail2ban"
-      ],
-      "env": {
-        "MESH_BROKER_FILE": "/run/secrets/broker"
-      }
     }
   ],
   "build": {
-    "on": [
-      {
-        "arg": "BUILD_BASE",
-        "module": "mesh-tools",
-        "artifact": "build"
-      },
-      {
-        "arg": "RUNTIME_BASE",
-        "module": "mesh-tools",
-        "artifact": "runtime"
-      }
-    ],
     "artifacts": [
       {
-        "name": "runtime",
-        "kind": "image",
-        "from": "Dockerfile"
+        "name": "tools",
+        "kind": "bundle",
+        "language": "typescript",
+        "entrypoints": [
+          "tools/index.js"
+        ]
       }
     ]
   }

modules/fail2ban/package.json

@@ -12,7 +12,7 @@
     "typescript": "^5.6.0"
   },
   "scripts": {
-    "build": "tsc client.ts tools/index.ts --module NodeNext --moduleResolution NodeNext --target ES2022 --outDir dist",
+    "build": "tsc client.ts tools/index.ts --module NodeNext --moduleResolution NodeNext --target ES2022 --rootDir . --outDir dist",
     "test": "node --test --experimental-strip-types 'test/*.test.ts'"
   }
 }

modules/fail2ban/test/client.test.ts

@@ -2,7 +2,7 @@
 // on the control node on 2026-10-02 (novox/hq ADR 0179).
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { Fail2banClient, parseBans, parseJailStatus, type Runner } from "../client.ts";
+import { Fail2banClient, escalated, installed, parseBans, parseJailStatus, type Runner } from "../client.ts";
 
 const STATUS = "Status\n|- Number of jail:\t2\n`- Jail list:\trecidive, sshd\n";
 const RECIDIVE =
@@ -104,3 +104,11 @@ test("a jail's settings are read from the daemon's listings", async () => {
     logpath: [], journalmatch: "_SYSTEMD_UNIT=sshd.service + _COMM=sshd",
   });
 });
+
+test("the client runs as given by root and through sudo without a prompt by anyone else", () => {
+  assert.deepEqual(escalated("fail2ban-client", ["status"], 0), ["fail2ban-client", ["status"]]);
+  assert.deepEqual(escalated("fail2ban-client", ["set", "sshd", "banip", "198.51.100.7"], 1000),
+    ["sudo", ["-n", "fail2ban-client", "set", "sshd", "banip", "198.51.100.7"]]);
+  assert.equal(installed("sh"), true);
+  assert.equal(installed("no-such-client-of-the-mesh"), false);
+});

modules/fail2ban/tools/index.ts

@@ -55,7 +55,7 @@ export function getFail2banTools(fail2ban: Fail2banClient): ToolDefinition[] {
   ];
 }
 
-const fail2ban = Fail2banClient.fromEnv();
+const fail2ban = Fail2banClient.onThisMachine();
 // The seat's verbs under the seat's name: the runtime serves them on the seat's subjects where this
 // module holds it (ADR 0159, 0160). The module's own under its own.
 registerModuleTools("node-intrusion-prevention", () => getSeatVerbs(fail2ban));