Publish quixos-nix-helpers from 932fe7714761fb8b5db4bd6401357cdff762a428

.quixos-subtree-source.json

@@ -1,7 +1,7 @@
 {
   "version": 1,
   "sourceRepo": "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/quixos",
-  "sourceCommit": "abc91ab1cbbd61ffd7f0a49dbc5768598ac8745c",
+  "sourceCommit": "932fe7714761fb8b5db4bd6401357cdff762a428",
   "sourcePath": "quixos-instance/quixos-nix-helpers",
   "exportName": "quixos-nix-helpers",
   "mirrorRemote": "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/quixos-nix-helpers.git"

PORTABLE_ARTIFACTS.md

@@ -113,8 +113,9 @@ service = {
 };
 ```
 
-Each invocation gets a fresh engine process. The adapter admits one active frame
+Each invocation gets a fresh Worker in a reusable engine process. An engine runs
-and a bounded FIFO; queue wait consumes the deadline. Overflow is an explicit
+one active frame; the adapter has bounded concurrency and queueing. Queue wait
+consumes the deadline. Overflow is an explicit
 `RESTRICTED_QUEUE_FULL` result. Cancellation kills the engine process group and
 removes its sockets before acknowledgement. All graph calls inherit the trusted
 invocation identity; authored code cannot choose another frame or workspace.
@@ -127,11 +128,15 @@ parent environment credentials, and unlisted modules are denied. Explicit dates,
 available. Host-managed HTTP bridges expose only the current frame's declared
 graph ports. Authored serialization is untrusted protocol input.
 
-This is an inner execution restriction, **not a hardened shared-process sandbox**.
+The packaged runtime uses the platform's Bubblewrap/seccomp launcher. Only the
-One workspace owns the surrounding VM. Systemd limits the entire package cgroup,
+engine's read-only runtime closure and private broker directory are mounted;
-including adapter and child engines; memory exhaustion terminates that group.
+native filesystem/process/network escape probes qualify that boundary. Systemd
-No per-isolate memory protection is claimed. A guest user can control its VM,
+limits the whole package in a workspace VM. Shared authority additionally charges
-so authoritative graph grants and credentials must remain outside it.
+each engine to its own cgroup before launch. No per-isolate memory protection or
+Cloudflare hosted side-channel defenses are claimed. See the
+[runtime decision](../../docs/RESTRICTED_RUNTIME_DECISION.md#os-process-confinement-implementation)
+for the exact boundary and residual risks. A guest user can control its VM, so
+authoritative graph grants and credentials must remain outside it.
 
 Qualification commands:
 

artifacts.nix

@@ -96,18 +96,7 @@ let
       esbuild = "${pkgs.esbuild}/bin/esbuild";
       shell = "${pkgs.runtimeShell}";
       serviceAdapter = ./portable-service.mjs;
-      restricted =
+      restrictedSDK = "${(import ./restricted-execution { inherit pkgs core; }).sdk}/core.mjs";
-        if service.restricted or false then
-          let
-            executor = import ./restricted-execution { inherit pkgs core; };
-          in
-          {
-            runtime = "${executor.runtime}/bin/quixos-restricted-registry";
-            sdk = "${executor.sdk}/core.mjs";
-            limits = service.limits or { };
-          }
-        else
-          null;
     }
   );
   compiled =

build-artifacts.mjs

@@ -128,8 +128,7 @@ for (const { target, mode, settings } of builds) {
   const bundlePath =
     mode === "remote" ? "share/quixos/remote/server/module.mjs" : `share/quixos/portable/${target}/module.mjs`;
   await fs.mkdir(path.dirname(path.join(output, bundlePath)), { recursive: true });
-  const restricted = !!config.restricted && target === "server";
+  const coreImport = target === "browser" ? coreURL : coreServer;
-  const coreImport = target === "browser" ? coreURL : restricted ? config.restricted.sdk : coreServer;
   const metadata = path.join(work, "bundle-meta.json");
   measureBuild("portable-bundle", { package: pkg.revision, target, mode }, () =>
     execFileSync(
@@ -137,7 +136,7 @@ for (const { target, mode, settings } of builds) {
       [
         entry,
         "--bundle",
-        `--platform=${target === "browser" || restricted ? "browser" : "node"}`,
+        `--platform=${target === "browser" ? "browser" : "node"}`,
         "--format=esm",
         "--minify-whitespace",
         "--target=es2024",
@@ -159,7 +158,7 @@ for (const { target, mode, settings } of builds) {
         (i) =>
           i.external &&
           i.path !== coreImport &&
-          !(target === "server" && !restricted && builtinModules.includes(i.path.replace(/^node:/, ""))),
+          !(target === "server" && builtinModules.includes(i.path.replace(/^node:/, ""))),
       ),
     )
   )
@@ -182,6 +181,44 @@ for (const { target, mode, settings } of builds) {
     files: [await recordFile(bundlePath, "text/javascript"), ...sharedFiles],
   };
   implementations.push({ ...body, contentDigest: compiler.implementationDigest(body) });
+  if (target === "server" && mode !== "remote" && exports.length) {
+    // A closed candidate is not an eligibility claim. The host checks these
+    // bytes and its exact qualified SDK before admitting it to the sandbox.
+    // Keep a normal service implementation for unsupported dependencies.
+    const restrictedPath = "share/quixos/restricted/module.mjs";
+    const sdkPath = "share/quixos/restricted/core.mjs";
+    const sdkName = "quixos:restricted-sdk/v1";
+    await fs.mkdir(path.dirname(path.join(output, restrictedPath)), { recursive: true });
+    await fs.copyFile(config.restrictedSDK, path.join(output, sdkPath));
+    measureBuild("restricted-bundle", { package: pkg.revision }, () =>
+      execFileSync(
+        config.esbuild,
+        [
+          entry,
+          "--bundle",
+          "--platform=node",
+          "--format=esm",
+          "--minify-whitespace",
+          "--target=es2024",
+          `--outfile=${path.join(output, restrictedPath)}`,
+          `--alias:@quixos/camino-replica-core=${sdkName}`,
+          `--external:${sdkName}`,
+        ],
+        { cwd: work, stdio: "inherit" },
+      ),
+    );
+    const restricted = {
+      id: "restricted-module",
+      target: "server",
+      compatibility: "quixos-restricted-module-v1",
+      path: restrictedPath,
+      ports: "quixos-transaction-ports-v1",
+      registryExport: settings.registryExport,
+      exports,
+      files: [await recordFile(restrictedPath, "text/javascript"), await recordFile(sdkPath, "text/javascript")],
+    };
+    implementations.push({ ...restricted, contentDigest: compiler.implementationDigest(restricted) });
+  }
 }
 const components =
   config.group && !config.components

build-service.mjs

@@ -13,62 +13,6 @@ export async function buildService({
   recordFile,
 }) {
   const relative = compiler.artifactPath;
-  if (config.restricted) {
-    if (config.service.entry || pkg.exports.some((e) => e.execution.kind === "remote"))
-      throw Error(
-        "Restricted services require portable snapshot/transaction exports; remote/custom services keep their VM path",
-      );
-    const modules = implementations.filter((i) => i.target === "server");
-    if (modules.length !== 1 || pkg.exports.some((e) => !modules[0].exports.includes(e.id)))
-      throw Error("Restricted service requires exactly one checked portable registry covering all exports");
-    const limits = config.restricted.limits;
-    if (!limits || typeof limits !== "object" || Array.isArray(limits))
-      throw Error("Restricted limits must be an object");
-    if (Object.keys(limits).some((key) => !["deadlineMs", "maxBytes", "maxPortCalls", "maxQueued"].includes(key)))
-      throw Error("Unknown restricted service limit");
-    for (const [key, min, max] of [
-      ["deadlineMs", 1, 60000],
-      ["maxBytes", 1024, 4194304],
-      ["maxPortCalls", 1, 10000],
-      ["maxQueued", 0, 64],
-    ])
-      if (limits[key] !== undefined && (!Number.isSafeInteger(limits[key]) || limits[key] < min || limits[key] > max))
-        throw Error("Invalid restricted service limit " + key);
-    await fs.mkdir(path.join(output, "bin"), { recursive: true });
-    await fs.mkdir(path.join(output, "share/quixos/service"), { recursive: true });
-    const configFile = "share/quixos/service/restricted.json";
-    const module = modules[0];
-    await fs.writeFile(
-      path.join(output, configFile),
-      JSON.stringify({
-        module: path.relative("share/quixos/service", module.path),
-        registryExport: module.registryExport,
-        exports: module.exports,
-        sdk: [{ name: config.restricted.sdk, path: config.restricted.sdk }],
-        ...limits,
-      }),
-    );
-    await fs.writeFile(
-      path.join(output, "bin/service"),
-      `#!${config.shell}\nservice_root=\${0%/*}/..\nexec ${config.restricted.runtime} "$service_root/${configFile}"\n`,
-      { mode: 0o755 },
-    );
-    const body = {
-      id: "service",
-      target: "server",
-      compatibility: "quixos-service-v1",
-      path: "bin/service",
-      ports: "quixos-transaction-ports-v1",
-      exports: module.exports,
-      files: [
-        await recordFile("bin/service", "text/x-shellscript"),
-        await recordFile(configFile, "application/json"),
-        ...module.files,
-      ],
-    };
-    implementations.unshift({ ...body, contentDigest: compiler.implementationDigest(body) });
-    return;
-  }
   if (pkg.exports.length || config.service.entry) {
     await fs.mkdir(path.join(output, "bin"), { recursive: true });
     await fs.mkdir(path.join(output, "share/quixos/service"), { recursive: true });
@@ -78,7 +22,10 @@ export async function buildService({
         throw Error("Custom service entry must be JavaScript; use a separate typed/language build before packaging");
       serviceEntry = path.join(config.source, relative(config.service.entry));
     } else {
-      const modules = implementations.filter((implementation) => implementation.target === "server");
+      const modules = implementations.filter(
+        (implementation) =>
+          implementation.target === "server" && implementation.compatibility === "quixos-js-module-v1",
+      );
       if (pkg.exports.some((entry) => !modules.some((module) => module.exports.includes(entry.id))))
         throw Error("Generated service does not cover every package export; provide a custom service");
       if (!modules.length) throw Error("Generated service requires a checked registry");

restricted-execution/default.nix

@@ -1,6 +1,36 @@
 { pkgs, core }:
 let
   workerd = import ./workerd.nix { inherit pkgs; };
+  sandbox = import ./sandbox.nix {
+    inherit pkgs;
+    runtime = workerd;
+    executable = "${workerd}/bin/workerd";
+  };
+  nativeProbe =
+    pkgs.runCommand "quixos-restricted-native-probe"
+      {
+        nativeBuildInputs = [ pkgs.stdenv.cc ];
+      }
+      ''
+        mkdir -p "$out/bin"
+        $CC -O2 -Wall -Wextra -Werror ${./sandbox-probe.c} -o "$out/bin/probe"
+      '';
+  nativeProbeSandbox = import ./sandbox.nix {
+    inherit pkgs;
+    runtime = nativeProbe;
+    executable = "${nativeProbe}/bin/probe";
+  };
+  identityLauncher =
+    pkgs.runCommand "quixos-restricted-identity-launcher"
+      {
+        nativeBuildInputs = [ pkgs.stdenv.cc ];
+      }
+      ''
+        mkdir -p "$out/bin"
+        $CC -O2 -Wall -Wextra -Werror ${./identity-launcher.c} \
+          -DSANDBOX_EXECUTABLE='"${sandbox}/bin/quixos-restricted-sandbox"' \
+          -o "$out/bin/quixos-restricted-engine"
+      '';
   # Transaction-port/value adapters do not need the browser's CRDT/Wasm engine.
   # Keep this surface explicit; it is bundled into checked restricted handlers.
   sdk = pkgs.runCommand "quixos-restricted-sdk" { nativeBuildInputs = [ pkgs.esbuild ]; } ''
@@ -23,6 +53,7 @@ let
         makeWrapper ${pkgs.nodejs_24}/bin/node "$out/bin/quixos-restricted-registry" \
           --add-flags "$out/lib/service.mjs" \
           --set QUIXOS_RESTRICTED_WORKERD ${workerd}/bin/workerd \
+          --set QUIXOS_RESTRICTED_SANDBOX ${sandbox}/bin/quixos-restricted-sandbox \
           --set QUIXOS_RESTRICTED_WORKER "$out/lib/worker.mjs"
       '';
   qualification =
@@ -40,6 +71,9 @@ in
 {
   inherit
     workerd
+    sandbox
+    identityLauncher
+    nativeProbeSandbox
     sdk
     runtime
     qualification

restricted-execution/identity-launcher.c

@@ -0,0 +1,88 @@
+#define _GNU_SOURCE
+#include <dirent.h>
+#include <fcntl.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <sys/resource.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/* Installed only as a narrowly executable NixOS wrapper. This trusted helper
+ * accepts no executable, environment, filesystem root or arbitrary UID. The
+ * caller is platform authority, never a workspace guest or authored Worker. */
+static void fail(const char *message) {
+  fprintf(stderr, "RESTRICTED_IDENTITY: %s\n", message);
+  exit(125);
+}
+
+int main(int argc, char **argv) {
+  const char *root = "/run/quixos-restricted-engines/";
+  uid_t caller = getuid();
+  gid_t group = getgid();
+  struct passwd *owner = getpwnam("quixos-graph");
+  if (geteuid() != 0) fail("privileged wrapper unavailable");
+  if (!owner) fail("authority identity unavailable");
+  if (caller != owner->pw_uid) fail("caller identity mismatch");
+  if (argc != 3) fail("invalid arguments");
+  char *end;
+  unsigned long number = strtoul(argv[2], &end, 10);
+  if (!*argv[2] || *end || number < 610000 || number >= 610064)
+    fail("invalid engine identity");
+  uid_t identity = (uid_t)number;
+  if (strlen(argv[1]) != strlen(root) + 16 || strncmp(argv[1], root, strlen(root)))
+    fail("invalid engine directory");
+  const char *name = argv[1] + strlen(root);
+  if (strncmp(name, "qx-engine-", 10) ||
+      strlen(name) != 16 || strspn(name + 10, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789") != 6)
+    fail("invalid engine directory");
+  int parent = open("/run/quixos-restricted-engines", O_RDONLY | O_DIRECTORY | O_NOFOLLOW);
+  struct stat info;
+  if (parent < 0 || fstat(parent, &info) || info.st_uid != caller || (info.st_mode & 066))
+    fail("invalid engine root");
+  int directory = openat(parent, name, O_RDONLY | O_DIRECTORY | O_NOFOLLOW);
+  if (directory < 0 || fstat(directory, &info) || info.st_uid != caller || (info.st_mode & 077))
+    fail("invalid engine owner");
+  DIR *entries = fdopendir(dup(directory));
+  if (!entries) fail("engine entries");
+  struct dirent *entry;
+  unsigned int files = 0;
+  while ((entry = readdir(entries))) {
+    const char *file = entry->d_name;
+    if (!strcmp(file, ".") || !strcmp(file, "..")) continue;
+    int socket = !strcmp(file, "broker.sock");
+    if ((!socket && strcmp(file, "config.capnp") && strcmp(file, "parent.mjs")) ||
+        fstatat(directory, file, &info, AT_SYMLINK_NOFOLLOW) || info.st_uid != caller ||
+        info.st_nlink != 1 || (socket ? !S_ISSOCK(info.st_mode) : !S_ISREG(info.st_mode)) ||
+        info.st_size > 4 * 1024 * 1024)
+      fail("unexpected engine file");
+    files++;
+  }
+  closedir(entries);
+  if (files != 3) fail("incomplete engine configuration");
+  const char *files_to_transfer[] = {"config.capnp", "parent.mjs", "broker.sock"};
+  for (size_t i = 0; i < 3; i++) {
+    if (fchownat(directory, files_to_transfer[i], identity, group, AT_SYMLINK_NOFOLLOW) ||
+        fchmodat(directory, files_to_transfer[i], 0660, 0))
+      fail("engine file ownership");
+  }
+  if (fchown(directory, identity, group) || fchmod(directory, 0770))
+    fail("engine directory ownership");
+  close(directory);
+  close(parent);
+  struct rlimit core = {0, 0};
+  if (setrlimit(RLIMIT_CORE, &core) || setgroups(0, NULL) ||
+      setresgid(identity, identity, identity) || setresuid(identity, identity, identity) ||
+      prctl(PR_SET_DUMPABLE, 0) || prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0))
+    fail("identity confinement");
+  /* The containing directory grants only its owner and authority access. A
+   * socket created by workerd must also admit authority's different UID/GID. */
+  umask(0000);
+  char *args[] = {SANDBOX_EXECUTABLE, argv[1], NULL};
+  clearenv();
+  execv(SANDBOX_EXECUTABLE, args);
+  fail("sandbox launch");
+}

restricted-execution/identity-module.nix

@@ -0,0 +1,28 @@
+{
+  executor,
+  enable,
+  controlGroup,
+}:
+{ config, lib, ... }:
+{
+  config = lib.mkIf enable {
+    assertions = [
+      {
+        assertion = lib.all (user: user.uid == null || user.uid < 610000 || user.uid >= 610064) (
+          builtins.attrValues config.users.users
+        );
+        message = "UIDs 610000–610063 are reserved for restricted engine identities.";
+      }
+    ];
+    systemd.tmpfiles.rules = [
+      "d /run/quixos-restricted-engines 0711 quixos-graph ${controlGroup} -"
+    ];
+    security.wrappers.quixos-restricted-engine = {
+      source = "${executor.identityLauncher}/bin/quixos-restricted-engine";
+      owner = "root";
+      group = controlGroup;
+      permissions = "u+rx,g+rx,o-rwx";
+      setuid = true;
+    };
+  };
+}

restricted-execution/sandbox-probe.c

@@ -0,0 +1,64 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ptrace.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static void check(int condition, const char *label) {
+  if (!condition) {
+    fprintf(stderr, "ESCAPE: %s (%s)\n", label, strerror(errno));
+    exit(1);
+  }
+}
+int main(void) {
+  for (int fd = 3; fd < 256; fd++)
+    check(fcntl(fd, F_GETFD) < 0 && errno == EBADF, "inherited descriptor");
+  check(!getenv("QUIXOS_VM_SECRET"), "parent environment");
+  check(open("/etc/test-secret", O_RDONLY) < 0, "authority filesystem");
+  check(open("/sys/fs/cgroup/cgroup.procs", O_WRONLY) < 0, "resource controls");
+  check(open("/proc/1/root/etc/test-secret", O_RDONLY) < 0, "proc root escape");
+  check(socket(AF_INET, SOCK_STREAM, 0) < 0 && errno == EPERM, "IPv4 socket");
+  check(socket(AF_INET6, SOCK_STREAM, 0) < 0 && errno == EPERM, "IPv6 socket");
+  check(socket(AF_NETLINK, SOCK_RAW, 0) < 0 && errno == EPERM, "netlink socket");
+  check(ptrace(PTRACE_TRACEME, 0, NULL, NULL) < 0 && errno == EPERM, "ptrace");
+  check(unshare(CLONE_NEWUSER) < 0, "nested user namespace");
+  pid_t child = fork();
+  if (child == 0) _exit(2);
+  check(child < 0 && errno == EPERM, "subprocess");
+  check(access("/bin/sh", X_OK) < 0, "ambient executable");
+  check(getppid() <= 1, "host process visibility");
+  struct sockaddr_un address = {.sun_family = AF_UNIX};
+  int outside = socket(AF_UNIX, SOCK_STREAM, 0);
+  check(outside >= 0, "Unix socket support");
+  strcpy(address.sun_path, "/run/quixos-native-authority/test.sock");
+  check(connect(outside, (struct sockaddr *)&address, sizeof(address)) < 0,
+    "authority Unix socket");
+  close(outside);
+  outside = socket(AF_UNIX, SOCK_STREAM, 0);
+  memset(address.sun_path, 0, sizeof(address.sun_path));
+  strcpy(address.sun_path + 1, "quixos-native-authority");
+  check(connect(outside, (struct sockaddr *)&address,
+    offsetof(struct sockaddr_un, sun_path) + 1 + strlen(address.sun_path + 1)) < 0,
+    "authority abstract socket");
+  close(outside);
+  char directory[4096];
+  check(getcwd(directory, sizeof(directory)) != NULL, "engine directory");
+  check(snprintf(address.sun_path, sizeof(address.sun_path), "%s/broker.sock", directory) <
+      (int)sizeof(address.sun_path), "broker path length");
+  int broker = socket(AF_UNIX, SOCK_STREAM, 0);
+  check(broker >= 0 && connect(broker, (struct sockaddr *)&address, sizeof(address)) == 0,
+      "authorized broker");
+  check(write(broker, "sandbox-probe", 13) == 13, "broker write");
+  close(broker);
+  puts("RESTRICTED_NATIVE_SANDBOX_PASSED");
+  return 0;
+}

restricted-execution/sandbox.c

@@ -0,0 +1,77 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/* Trusted, single-process admission gate. The supervisor charges this PID to
+ * its engine cgroup before releasing stdin. All subsequently created namespace
+ * helpers and threads inherit that charge. No authored code runs here. */
+static void fail(const char *message) {
+  fprintf(stderr, "RESTRICTED_SANDBOX: %s\n", message);
+  exit(125);
+}
+
+int main(int argc, char **argv) {
+  struct stat info;
+  if (argc != 2 || argv[1][0] != '/' || strstr(argv[1], "/../") ||
+      lstat(argv[1], &info) || !S_ISDIR(info.st_mode) ||
+      info.st_uid != getuid() || (info.st_mode & 007))
+    fail("invalid engine directory");
+  char gate;
+  if (read(STDIN_FILENO, &gate, 1) != 1 || gate != 1)
+    fail("engine admission was not released");
+  int input = open("/dev/null", O_RDONLY);
+  if (input < 0 || dup2(input, STDIN_FILENO) < 0)
+    fail("stdin");
+  close(input);
+  int filter = open(SANDBOX_FILTER, O_RDONLY);
+  if (filter < 0)
+    fail("seccomp filter");
+  char filter_fd[32];
+  snprintf(filter_fd, sizeof(filter_fd), "%d", filter);
+  char *args[4096];
+  size_t count = 0;
+#define ARG(value) args[count++] = (value)
+  ARG(SANDBOX_BWRAP);
+  ARG("--unshare-all");
+  ARG("--unshare-user");
+  ARG("--die-with-parent");
+  ARG("--disable-userns");
+  ARG("--assert-userns-disabled");
+  ARG("--cap-drop"); ARG("ALL");
+  ARG("--hostname"); ARG("quixos-restricted");
+  ARG("--clearenv");
+  ARG("--setenv"); ARG("TZ"); ARG("UTC");
+  ARG("--setenv"); ARG("LANG"); ARG("C.UTF-8");
+  FILE *closure = fopen(SANDBOX_CLOSURE, "r");
+  if (!closure)
+    fail("runtime closure");
+  char *line = NULL;
+  size_t capacity = 0;
+  while (getline(&line, &capacity, closure) >= 0) {
+    line[strcspn(line, "\n")] = 0;
+    if (strncmp(line, "/nix/store/", 11) || strchr(line, ' ') || count > 4000)
+      fail("runtime closure entry");
+    char *path = strdup(line);
+    if (!path)
+      fail("runtime closure allocation");
+    ARG("--ro-bind"); ARG(path); ARG(path);
+  }
+  fclose(closure);
+  free(line);
+  ARG("--proc"); ARG("/proc");
+  ARG("--dev"); ARG("/dev");
+  ARG("--tmpfs"); ARG("/tmp");
+  ARG("--bind"); ARG(argv[1]); ARG(argv[1]);
+  ARG("--chdir"); ARG(argv[1]);
+  ARG("--seccomp"); ARG(filter_fd);
+  ARG("--"); ARG(SANDBOX_EXECUTABLE);
+  ARG("serve"); ARG("--experimental"); ARG("config.capnp");
+  ARG(NULL);
+  execv(SANDBOX_BWRAP, args);
+  fail("bubblewrap failed");
+}

restricted-execution/sandbox.nix

@@ -0,0 +1,30 @@
+{
+  pkgs,
+  runtime,
+  executable,
+}:
+let
+  closure = pkgs.closureInfo { rootPaths = [ runtime ]; };
+  filter =
+    pkgs.runCommand "quixos-restricted-seccomp"
+      {
+        nativeBuildInputs = [
+          pkgs.stdenv.cc
+          pkgs.pkg-config
+        ];
+        buildInputs = [ pkgs.libseccomp ];
+      }
+      ''
+        $CC -O2 -Wall -Wextra -Werror ${./seccomp.c} $(pkg-config --cflags --libs libseccomp) -o filter
+        ./filter > "$out"
+      '';
+in
+pkgs.runCommand "quixos-restricted-sandbox" { nativeBuildInputs = [ pkgs.stdenv.cc ]; } ''
+  mkdir -p "$out/bin"
+  $CC -O2 -Wall -Wextra -Werror ${./sandbox.c} \
+    -DSANDBOX_BWRAP='"${pkgs.bubblewrap}/bin/bwrap"' \
+    -DSANDBOX_EXECUTABLE='"${executable}"' \
+    -DSANDBOX_FILTER='"${filter}"' \
+    -DSANDBOX_CLOSURE='"${closure}/store-paths"' \
+    -o "$out/bin/quixos-restricted-sandbox"
+''

restricted-execution/seccomp.c

@@ -0,0 +1,54 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <linux/sched.h>
+#include <seccomp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+/* Layered on an empty mount tree, fresh PID/user/network namespaces, no caps,
+ * no inherited descriptors and an immutable runtime closure. Deny kernel and
+ * process escape surfaces; retain V8's ordinary memory/thread syscalls. */
+static void checked(int result) {
+  if (result < 0) {
+    fprintf(stderr, "seccomp rule: %d\n", result);
+    exit(1);
+  }
+}
+int main(void) {
+  scmp_filter_ctx filter = seccomp_init(SCMP_ACT_ALLOW);
+  if (!filter) return 1;
+  const char *denied[] = {
+    "fork", "vfork", "execveat", "ptrace", "process_vm_readv", "process_vm_writev",
+    "pidfd_getfd", "kcmp", "bpf", "perf_event_open", "userfaultfd", "io_uring_setup",
+    "mount", "umount2", "pivot_root", "chroot", "move_mount", "open_tree", "fsopen",
+    "fsconfig", "fsmount", "fspick", "mount_setattr", "open_by_handle_at",
+    "name_to_handle_at", "setns", "unshare", "keyctl", "add_key", "request_key",
+    "reboot", "kexec_load", "kexec_file_load", "init_module", "finit_module",
+    "delete_module", "swapon", "swapoff", "syslog", "acct", "sethostname",
+    "setdomainname", "iopl", "ioperm", "lookup_dcookie", NULL
+  };
+  for (size_t i = 0; denied[i]; i++) {
+    int syscall = seccomp_syscall_resolve_name(denied[i]);
+    if (syscall != __NR_SCMP_ERROR)
+      checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), syscall, 0));
+  }
+  /* glibc falls back to clone when clone3 is unavailable. Only thread creation
+   * is admitted; subprocesses and new namespaces cannot be manufactured. */
+  checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(ENOSYS), SCMP_SYS(clone3), 0));
+  checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(clone), 1,
+    SCMP_A0(SCMP_CMP_MASKED_EQ, CLONE_THREAD, 0)));
+  const unsigned long namespaces[] = {CLONE_NEWUSER, CLONE_NEWNS, CLONE_NEWNET,
+    CLONE_NEWPID, CLONE_NEWIPC, CLONE_NEWUTS, CLONE_NEWCGROUP};
+  for (size_t i = 0; i < sizeof(namespaces) / sizeof(namespaces[0]); i++)
+    checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(clone), 1,
+      SCMP_A0(SCMP_CMP_MASKED_EQ, namespaces[i], namespaces[i])));
+  checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(socket), 1,
+    SCMP_A0(SCMP_CMP_NE, AF_UNIX)));
+  checked(seccomp_rule_add(filter, SCMP_ACT_ERRNO(EPERM), SCMP_SYS(ioctl), 1,
+    SCMP_A1(SCMP_CMP_EQ, 0x5412))); /* TIOCSTI */
+  checked(seccomp_export_bpf(filter, STDOUT_FILENO));
+  seccomp_release(filter);
+  return 0;
+}

restricted-execution/service.mjs

@@ -37,13 +37,13 @@ export class RestrictedEngineBudget {
       let releasing;
       const release = () =>
         (releasing ??= (async () => {
-          try {
+          await resource.release?.();
-            await resource.release?.();
+          this.#leases.delete(lease);
-          } finally {
-            this.#leases.delete(lease);
-          }
         })());
       release.attach = resource.attach;
+      release.usage = resource.usage;
+      release.kill = resource.kill;
+      release.uid = resource.uid;
       return release;
     } catch (error) {
       this.#leases.delete(lease);
@@ -83,6 +83,8 @@ export async function serveRestrictedRegistry(config, io = process) {
     !absolute(config.workerd) ||
     !absolute(config.worker) ||
     !absolute(config.module) ||
+    (config.sandbox !== undefined && !absolute(config.sandbox)) ||
+    (config.sandboxIdentity !== undefined && typeof config.sandboxIdentity !== "boolean") ||
     !/^[$A-Z_a-z][$\w]*$/.test(config.registryExport) ||
     !Array.isArray(config.exports) ||
     !config.exports.length ||
@@ -160,19 +162,38 @@ export async function serveRestrictedRegistry(config, io = process) {
       throw fixedError("RESTRICTED_BACKPRESSURE");
     io.stdout.write(line);
   };
-  // Linux USER_HZ is 100 on the supported NixOS architectures. Read process
+  // A sandbox has namespace helpers as well as workerd. Charge the complete
-  // CPU outside the engine; authored code cannot forge these usage messages.
+  // delegated cgroup when available; the qualification fallback follows the
+  // bounded process tree, never trusting a worker's self-reported counters.
+  const engineUsage = async (engine) => {
+    if (engine.release?.usage) return engine.release.usage();
+    engine.processTicks ??= new Map();
+    const pending = [engine.child.pid];
+    let memoryBytes = 0,
+      visited = 0;
+    while (pending.length) {
+      if (++visited > 64) throw fixedError("RESTRICTED_PROCESS_LIMIT");
+      const pid = pending.pop();
+      try {
+        const stat = await readFile(`/proc/${pid}/stat`, "utf8");
+        const fields = stat.slice(stat.lastIndexOf(")") + 2).split(" ");
+        engine.processTicks.set(`${pid}:${fields[19]}`, Number(fields[11]) + Number(fields[12]));
+        const status = await readFile(`/proc/${pid}/status`, "utf8");
+        memoryBytes += Number(status.match(/^VmRSS:\s+(\d+)/m)?.[1] ?? 0) * 1024;
+        const children = await readFile(`/proc/${pid}/task/${pid}/children`, "utf8");
+        pending.push(...children.trim().split(/\s+/).filter(Boolean).map(Number));
+      } catch (error) {
+        if (!["ENOENT", "ESRCH"].includes(error.code)) throw error;
+      }
+    }
+    return {
+      cpuMicroseconds: [...engine.processTicks.values()].reduce((sum, ticks) => sum + ticks * 10000, 0),
+      memoryBytes,
+    };
+  };
   const sampleCPU = async (call) => {
     if (!call.child?.pid) return;
-    let text;
+    const { cpuMicroseconds: total } = await engineUsage(call.engine);
-    try {
-      text = await readFile(`/proc/${call.child.pid}/stat`, "utf8");
-    } catch (error) {
-      if (error.code === "ENOENT" || error.code === "ESRCH") return;
-      throw error;
-    }
-    const fields = text.slice(text.lastIndexOf(")") + 2).split(" ");
-    const total = (Number(fields[11]) + Number(fields[12])) * 10000;
     const cpuMicroseconds = total - (call.cpuBaseline ?? 0);
     if (call.engine) call.engine.cpuTotal = total;
     if (!Number.isSafeInteger(cpuMicroseconds) || cpuMicroseconds < (call.cpuMicroseconds ?? 0))
@@ -217,8 +238,7 @@ export async function serveRestrictedRegistry(config, io = process) {
         // A delayed child request can never acquire the next call's authority.
         if (engine.current === call) engine.current = null;
         if (!stopped && reason.code === "INVOCATION_ENDED" && !usageFailure && !engine.destroying) {
-          const status = await readFile(`/proc/${engine.child.pid}/status`, "utf8").catch(() => "");
+          const rss = (await engineUsage(engine)).memoryBytes;
-          const rss = Number(status.match(/^VmRSS:\s+(\d+)/m)?.[1] ?? Infinity) * 1024;
           metrics.peakRSSBytes = Math.max(metrics.peakRSSBytes, rss);
           // Bound retained engine heaps as well as lifetime. Hard aggregate
           // physical memory remains the supervising process/cgroup's contract.
@@ -263,10 +283,13 @@ export async function serveRestrictedRegistry(config, io = process) {
       if (index >= 0) idleEngines.splice(index, 1);
       engine.current = null;
       if (engine.child?.pid) {
-        try {
+        if (engine.release.kill) await engine.release.kill();
-          process.kill(-engine.child.pid, "SIGKILL");
+        else {
-        } catch (error) {
+          try {
-          if (error.code !== "ESRCH") throw error;
+            process.kill(-engine.child.pid, "SIGKILL");
+          } catch (error) {
+            if (error.code !== "ESRCH") throw error;
+          }
         }
         await engine.exited;
       }
@@ -380,27 +403,37 @@ export async function serveRestrictedRegistry(config, io = process) {
     const file = join(engine.directory, "config.capnp");
     await writeFile(file, configuration);
     if (!call.open) return;
-    engine.child = spawn(config.workerd, ["serve", "--experimental", file], {
+    if (config.sandboxIdentity && !Number.isSafeInteger(engine.release.uid))
-      detached: true,
+      throw fixedError("RESTRICTED_IDENTITY_UNAVAILABLE");
-      env: { TZ: "UTC", LANG: "C.UTF-8" },
+    engine.child = spawn(
-      cwd: engine.directory,
+      config.sandbox ?? config.workerd,
-      stdio: ["ignore", "ignore", "pipe"],
+      config.sandbox
-    });
+        ? [engine.directory, ...(config.sandboxIdentity ? [String(engine.release.uid)] : [])]
+        : ["serve", "--experimental", file],
+      {
+        detached: true,
+        env: { TZ: "UTC", LANG: "C.UTF-8" },
+        cwd: engine.directory,
+        stdio: [config.sandbox ? "pipe" : "ignore", "ignore", "pipe"],
+      },
+    );
     metrics.starts++;
     engine.exited = new Promise((resolve) => {
       engine.child.once("exit", resolve);
       engine.child.once("error", resolve);
     });
+    engine.child.stdin?.on("error", () => engine.current?.terminate("RESTRICTED_START_FAILED"));
     call.child = engine.child;
-    await engine.release.attach?.(engine.child.pid);
-    watchCPU(call);
     let diagnostics = 0;
     engine.child.stderr.on("data", (chunk) => {
       if ((diagnostics += chunk.length) > 65536) {
         if (engine.current?.open) engine.current.terminate("RESTRICTED_DIAGNOSTIC_LIMIT");
         else void destroyEngine(engine).catch(fail);
-      }
+      } else config.diagnostics?.(chunk);
     });
+    await engine.release.attach?.(engine.child.pid);
+    if (config.sandbox && call.open) engine.child.stdin.end(Buffer.from([1]));
+    watchCPU(call);
     engine.child.once("error", () => engine.current?.terminate("RESTRICTED_START_FAILED"));
     void engine.exited.then(() => {
       if (engine.current?.open) engine.current.terminate("RESTRICTED_ENGINE_EXITED");
@@ -512,6 +545,7 @@ export async function serveRestrictedRegistry(config, io = process) {
       await finish(call, fixedError("INVOCATION_ENDED"), reply);
       metrics.completed++;
     } catch (error) {
+      config.diagnostics?.(Buffer.from(`RESTRICTED_HOST_ERROR:${error.code ?? error.name}\n`));
       if (call.open) {
         const code = /^RESTRICTED_[A-Z_]+$/.test(error.code ?? "") ? error.code : "RESTRICTED_PACKAGE_FAILED";
         await finish(call, error, { invocation: message.invocation, status: "failed", error: { code, message: code } });
@@ -663,6 +697,7 @@ if (process.argv[1] === new URL(import.meta.url).pathname) {
     ...config,
     workerd: process.env.QUIXOS_RESTRICTED_WORKERD,
     worker: process.env.QUIXOS_RESTRICTED_WORKER,
+    sandbox: process.env.QUIXOS_RESTRICTED_SANDBOX,
     module: join(dirname(process.argv[2]), config.module),
   });
 }

restricted-execution/service.test.mjs

@@ -50,7 +50,16 @@ async function fixture(source, options = {}) {
     }
   };
   const service = await serveRestrictedRegistry(
-    { workerd, worker, module, registryExport: "registry", exports: ["test"], sdk: [], ...options },
+    {
+      workerd,
+      worker,
+      module,
+      sandbox: process.env.QUIXOS_TEST_SANDBOX,
+      registryExport: "registry",
+      exports: ["test"],
+      sdk: [],
+      ...options,
+    },
     io,
   );
   assert.deepEqual(await receive(), { abi, kind: "ready", exports: ["test"] });
@@ -86,6 +95,27 @@ async function fixture(source, options = {}) {
 }
 const registry = (code) => `export const registry={exports:['test'],async invoke(request,channel){${code}}};`;
 
+test("uncertain OS cleanup cannot release engine capacity", async () => {
+  const budget = new RestrictedEngineBudget(1, async () => ({
+    async release() {
+      throw Error("kernel cleanup not confirmed");
+    },
+  }));
+  const release = await budget.acquire(
+    () => false,
+    async () => {},
+  );
+  await assert.rejects(release(), /cleanup not confirmed/);
+  assert.equal(budget.stats().engines, 1);
+  await assert.rejects(
+    budget.acquire(
+      () => false,
+      async () => {},
+    ),
+    { code: "RESTRICTED_ENGINE_LIMIT" },
+  );
+});
+
 test("parallel frames route independently and cancellation cannot retire a neighbor", async () => {
   const f = await fixture(
     registry("return await channel({portId:'read',action:{kind:'state',primitive:'read'},input:request.input});"),
@@ -407,15 +437,21 @@ test("bounded FIFO rejects overload without losing active or queued frames", asy
 test("queue wait consumes the deadline and cancelled work never reaches its ports", async () => {
   const f = await fixture(
     registry("return await channel({portId:'read',action:{kind:'state',primitive:'read'},input:null});"),
-    { deadlineMs: 350, maxActive: 1 },
+    { deadlineMs: 4000, maxActive: 1 },
   );
   try {
     const first = f.start();
-    await f.receive();
+    assert.equal((await f.receive()).kind, "port");
-    const queued = f.start();
+    // Expire while the first call is deliberately blocked. Two equal relative
-    const replies = [await f.receive(), await f.receive()];
+    // deadlines let fast startup legitimately begin the queued call first.
-    assert.deepEqual(new Set(replies.map((x) => x.invocation)), new Set([first.invocation, queued.invocation]));
+    const queued = f.start(null, { root: "queued-deadline", deadlineMs: 50, depth: 1, calls: 10 });
-    assert.ok(replies.every((x) => x.error.code === "RESTRICTED_DEADLINE"));
+    const expired = await f.receive();
+    assert.equal(expired.invocation, queued.invocation);
+    assert.equal(expired.error.code, "RESTRICTED_DEADLINE");
+    f.send({ kind: "cancel", ...first });
+    const cancelled = await f.receive();
+    assert.equal(cancelled.invocation, first.invocation);
+    assert.equal(cancelled.kind, "cancelled");
     const fresh = f.start();
     const port = await f.receive();
     assert.equal(port.invocation, fresh.invocation);

restricted-execution/workerd.nix

@@ -1,6 +1,6 @@
 # Pinned upstream engine. This binary supplies an import/capability boundary;
-# production execution additionally requires OS limits and platform approval
+# production execution additionally requires the qualified OS identity,
-# for shared placement, or a workspace VM for unreviewed application code.
+# namespace, syscall, cgroup and invocation-broker boundaries.
 { pkgs }:
 let
   version = "1.20261005.1";