test(native): stabilize resource-limited binary layout controls

Keep the configured launcher alive while its limited Python child runs so ownership checks retain the admitted executable identity. Trigger memory exhaustion with one oversized ELF zero-fill tail rather than racing section traversal against a timeout.

Adapted from #1357. JavaScript syntax, strict C syntax compilation, formatting, and static checks passed. The Linux pwntools verification lane was not run on this macOS host.

Co-authored-by: You Wish <[email protected]>

scripts/fixtures/binary-layout-limited-python.c

@@ -0,0 +1,61 @@
+/* Keep the configured launcher identity alive while its resource-limited
+ * Python child runs. Both remain in REA's owned process group. */
+#define _POSIX_C_SOURCE 200809L
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/resource.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main(int argc, char **argv) {
+  char *python = getenv("REA_VERIFY_LIMITED_PYTHON");
+  char *limit = getenv("REA_VERIFY_LIMIT_OPTION");
+  if (python == NULL || python[0] != '/' || limit == NULL) {
+    fputs("limited Python fixture requires an absolute Python and limit\n", stderr);
+    return 127;
+  }
+  struct rlimit core = {0, 0};
+  if (setrlimit(RLIMIT_CORE, &core) != 0) {
+    perror("setrlimit");
+    return 127;
+  }
+  char **arguments = calloc((size_t)argc + 4, sizeof(char *));
+  if (arguments == NULL) return 127;
+  arguments[0] = "/usr/bin/prlimit";
+  arguments[1] = limit;
+  arguments[2] = "--";
+  arguments[3] = python;
+  for (int index = 1; index < argc; index++) arguments[index + 3] = argv[index];
+  pid_t child = fork();
+  if (child == 0) {
+    execv(arguments[0], arguments);
+    perror("execv");
+    _exit(127);
+  }
+  free(arguments);
+  if (child < 0) {
+    perror("fork");
+    return 127;
+  }
+  int status;
+  while (waitpid(child, &status, 0) < 0) {
+    if (errno == EINTR) continue;
+    perror("waitpid");
+    return 127;
+  }
+  if (WIFEXITED(status)) return WEXITSTATUS(status);
+  if (WIFSIGNALED(status)) {
+    int signum = WTERMSIG(status);
+    signal(signum, SIG_DFL);
+    sigset_t signals;
+    sigemptyset(&signals);
+    sigaddset(&signals, signum);
+    sigprocmask(SIG_UNBLOCK, &signals, NULL);
+    raise(signum);
+    return 128 + signum;
+  }
+  return 127;
+}

scripts/verify-binary-layout.mjs

@@ -15,6 +15,10 @@ import { promisify } from "node:util";
 import { Client } from "@modelcontextprotocol/client";
 import { StdioClientTransport } from "@modelcontextprotocol/client/stdio";
 import { PrivateRuntimeRoot } from "../dist/process/PrivateRuntimeRoot.js";
+import {
+  OwnedCommandFailure,
+  runOwnedCommand,
+} from "../dist/process/OwnedCommand.js";
 import { parseEvidence } from "../dist/domain/evidence.js";
 import { mcpTextValue } from "./lib/mcp-verifier-results.mjs";
 import { createVerifierRun, completeVerifierRun } from "./lib/verifier-run.mjs";
@@ -56,6 +60,13 @@ const root = await PrivateRuntimeRoot.create({
 const environment = Object.fromEntries(
   Object.entries(process.env).filter(([, value]) => typeof value === "string"),
 );
+const limitedPython = join(root.path, "limited-python");
+const limitedEnvironment = (option) => ({
+  ...environment,
+  REA_PWNTOOLS_PYTHON: limitedPython,
+  REA_VERIFY_LIMITED_PYTHON: python,
+  REA_VERIFY_LIMIT_OPTION: option,
+});
 const client = new Client({ name: "binary-layout-verifier", version: "1" });
 const transport = new StdioClientTransport({
   command: process.execPath,
@@ -73,6 +84,46 @@ let cases = 0;
 let bootstrapCases = 0;
 const failures = [];
 try {
+  await execute(
+    "gcc",
+    [
+      "-std=c11",
+      "-Wall",
+      "-Wextra",
+      "-Werror",
+      fileURLToPath(
+        new URL("./fixtures/binary-layout-limited-python.c", import.meta.url),
+      ),
+      "-o",
+      limitedPython,
+    ],
+    { timeout: 30_000, maxBuffer: 1024 * 1024 },
+  );
+  // A live limited child must retain its configured launcher's identity so
+  // timeout cleanup can still verify and terminate the entire owned group.
+  await assert.rejects(
+    runOwnedCommand(
+      {
+        command: limitedPython,
+        arguments: [
+          "-I",
+          "-c",
+          "import time; print('limited child ready', flush=True); time.sleep(60)",
+        ],
+        cwd: root.path,
+        runId: `${run.run_id}-limited-python-timeout`,
+        hostEnvironment: limitedEnvironment("--as=2147483648"),
+      },
+      { timeoutMs: 2000, diagnosticBytes: 1024 },
+    ),
+    (error) => {
+      assert.ok(error instanceof OwnedCommandFailure);
+      assert.equal(error.reason, "timeout");
+      assert.equal(error.cleanupFailure, null);
+      assert.ok(error.snapshot.stdout.text.includes("limited child ready"));
+      return true;
+    },
+  );
   const bootstrapRoot = join(root.path, "bootstrap-boundary");
   await mkdir(bootstrapRoot);
   const bootstrapPath = join(bootstrapRoot, "layout.py");
@@ -796,19 +847,12 @@ try {
     assert.deepEqual(await readFile(extendedPath), extendedObject);
     cases++;
   }
-  for (const [name, option, expected] of [
-    ["address-space", "--as=2147483648", '"address_space_bytes": 2147483648'],
-    ["cpu", "--cpu=20", '"cpu_seconds": 20'],
-    ["file-size", "--fsize=33554432", '"file_size_bytes": 33554432'],
+  for (const [option, expected] of [
+    ["--as=2147483648", '"address_space_bytes": 2147483648'],
+    ["--cpu=20", '"cpu_seconds": 20'],
+    ["--fsize=33554432", '"file_size_bytes": 33554432'],
   ]) {
-    const wrapper = join(root.path, `python-limit-${name}`);
-    const quotedPython = "'" + python.replaceAll("'", "'\"'\"'") + "'";
-    await writeFile(
-      wrapper,
-      `#!/bin/sh\nexec /usr/bin/prlimit ${option} -- ${quotedPython} "$@"\n`,
-      { mode: 0o700 },
-    );
-    const limitedEnvironment = { ...environment, REA_PWNTOOLS_PYTHON: wrapper };
+    const selectedEnvironment = limitedEnvironment(option);
     const limitedClient = new Client({
       name: "limited-layout-verifier",
       version: "1",
@@ -816,7 +860,7 @@ try {
     const limitedTransport = new StdioClientTransport({
       command: process.execPath,
       args: [entrypoint, "mcp"],
-      env: limitedEnvironment,
+      env: selectedEnvironment,
       stderr: "pipe",
     });
     try {
@@ -826,7 +870,7 @@ try {
           mode,
           join(root.path, "protected"),
           undefined,
-          limitedEnvironment,
+          selectedEnvironment,
           limitedClient,
         );
         assert.ok(value.limitations.some((item) => item.includes(expected)));
@@ -862,17 +906,29 @@ try {
   sectionHeavy.writeUInt16LE(sectionCount, 60);
   const sectionHeavyPath = join(root.path, "section-heavy.o");
   await writeFile(sectionHeavyPath, sectionHeavy);
-  const memoryWrapper = join(root.path, "python-memory-constraint");
-  const quotedPython = "'" + python.replaceAll("'", "'\"'\"'") + "'";
-  await writeFile(
-    memoryWrapper,
-    `#!/bin/sh\nexec /usr/bin/prlimit --as=100663296 -- ${quotedPython} "$@"\n`,
-    { mode: 0o700 },
+  // pwntools materializes each PT_LOAD zero-filled tail during inspection.
+  // One allocation larger than the whole address-space budget fails promptly;
+  // a large section count instead races CPU work against the command deadline.
+  const memoryHeavy = Buffer.from(await readFile(join(root.path, "protected")));
+  const memoryPhOffset = Number(memoryHeavy.readBigUInt64LE(32));
+  const memoryPhSize = memoryHeavy.readUInt16LE(54);
+  const memoryPhCount = memoryHeavy.readUInt16LE(56);
+  const lastLoadIndex = Array.from(
+    { length: memoryPhCount },
+    (_, index) => index,
+  ).findLast(
+    (index) =>
+      memoryHeavy.readUInt32LE(memoryPhOffset + index * memoryPhSize) === 1,
   );
-  const memoryEnvironment = {
-    ...environment,
-    REA_PWNTOOLS_PYTHON: memoryWrapper,
-  };
+  assert.notEqual(lastLoadIndex, undefined);
+  const memorySizeOffset = memoryPhOffset + lastLoadIndex * memoryPhSize + 40;
+  memoryHeavy.writeBigUInt64LE(
+    memoryHeavy.readBigUInt64LE(memorySizeOffset) + 128n * 1024n * 1024n,
+    memorySizeOffset,
+  );
+  const memoryHeavyPath = join(root.path, "memory-zero-tail");
+  await writeFile(memoryHeavyPath, memoryHeavy);
+  const memoryEnvironment = limitedEnvironment("--as=100663296");
   const memoryClient = new Client({
     name: "memory-layout-verifier",
     version: "1",
@@ -888,7 +944,7 @@ try {
     for (const mode of ["cli", "mcp"]) {
       const error = await inspect(
         mode,
-        sectionHeavyPath,
+        memoryHeavyPath,
         "resource_constraint",
         memoryEnvironment,
         memoryClient,
@@ -903,7 +959,7 @@ try {
       assert.ok(error.remediation.action.includes("memory"));
       cases++;
     }
-    assert.deepEqual(await readFile(sectionHeavyPath), sectionHeavy);
+    assert.deepEqual(await readFile(memoryHeavyPath), memoryHeavy);
   } finally {
     try {
       await memoryClient.close();
@@ -924,13 +980,7 @@ try {
   cpuHeavy.writeBigUInt64LE(BigInt(cpuSectionCount), sectionOffset + 32);
   const cpuHeavyPath = join(root.path, "cpu-section-heavy.o");
   await writeFile(cpuHeavyPath, cpuHeavy);
-  const cpuWrapper = join(root.path, "python-cpu-constraint");
-  await writeFile(
-    cpuWrapper,
-    `#!/bin/sh\nexec /usr/bin/prlimit --cpu=1: --core=0: -- ${quotedPython} "$@"\n`,
-    { mode: 0o700 },
-  );
-  const cpuEnvironment = { ...environment, REA_PWNTOOLS_PYTHON: cpuWrapper };
+  const cpuEnvironment = limitedEnvironment("--cpu=1:");
   const cpuClient = new Client({ name: "cpu-layout-verifier", version: "1" });
   const cpuTransport = new StdioClientTransport({
     command: process.execPath,
@@ -963,13 +1013,7 @@ try {
     }
   }
   for (const limit of [1024, 1]) {
-    const wrapper = join(root.path, `python-file-size-${limit}`);
-    await writeFile(
-      wrapper,
-      `#!/bin/sh\nexec /usr/bin/prlimit --fsize=${limit}: --core=0: -- ${quotedPython} "$@"\n`,
-      { mode: 0o700 },
-    );
-    const fileEnvironment = { ...environment, REA_PWNTOOLS_PYTHON: wrapper };
+    const fileEnvironment = limitedEnvironment(`--fsize=${limit}:`);
     const fileClient = new Client({
       name: "file-size-layout-verifier",
       version: "1",