Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 813 insertions, 0 deletions

diff --git a/security/sandbox/linux/Sandbox.cpp b/security/sandbox/linux/Sandbox.cpp
new file mode 100644
index 0000000000..9b1196bc5f
--- /dev/null
+++ b/security/sandbox/linux/Sandbox.cpp
@@ -0,0 +1,813 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "Sandbox.h"
+
+#include "LinuxSched.h"
+#include "SandboxBrokerClient.h"
+#include "SandboxChrootProto.h"
+#include "SandboxFilter.h"
+#include "SandboxInternal.h"
+#include "SandboxLogging.h"
+#include "SandboxOpenedFiles.h"
+#include "SandboxReporterClient.h"
+
+#include <dirent.h>
+#ifdef NIGHTLY_BUILD
+#  include "dlfcn.h"
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/futex.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/ptrace.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "mozilla/Array.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Range.h"
+#include "mozilla/SandboxInfo.h"
+#include "mozilla/StackWalk.h"
+#include "mozilla/Span.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/ipc/UtilityProcessSandboxing.h"
+#include "prenv.h"
+#include "base/posix/eintr_wrapper.h"
+#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
+#include "sandbox/linux/bpf_dsl/codegen.h"
+#include "sandbox/linux/bpf_dsl/dump_bpf.h"
+#include "sandbox/linux/bpf_dsl/policy.h"
+#include "sandbox/linux/bpf_dsl/policy_compiler.h"
+#include "sandbox/linux/bpf_dsl/seccomp_macros.h"
+#include "sandbox/linux/seccomp-bpf/trap.h"
+#include "sandbox/linux/system_headers/linux_filter.h"
+#include "sandbox/linux/system_headers/linux_seccomp.h"
+#include "sandbox/linux/system_headers/linux_syscalls.h"
+#if defined(ANDROID)
+#  include "sandbox/linux/system_headers/linux_ucontext.h"
+#endif
+
+#ifndef SECCOMP_FILTER_FLAG_SPEC_ALLOW
+#  define SECCOMP_FILTER_FLAG_SPEC_ALLOW (1UL << 2)
+#endif
+
+#ifdef MOZ_ASAN
+// Copy libsanitizer declarations to avoid depending on ASAN headers.
+// See also bug 1081242 comment #4.
+extern "C" {
+namespace __sanitizer {
+// Win64 uses long long, but this is Linux.
+typedef signed long sptr;
+}  // namespace __sanitizer
+
+typedef struct {
+  int coverage_sandboxed;
+  __sanitizer::sptr coverage_fd;
+  unsigned int coverage_max_block_size;
+} __sanitizer_sandbox_arguments;
+
+MOZ_IMPORT_API void __sanitizer_sandbox_on_notify(
+    __sanitizer_sandbox_arguments* args);
+}  // extern "C"
+#endif  // MOZ_ASAN
+
+// Signal number used to enable seccomp on each thread.
+mozilla::Atomic<int> gSeccompTsyncBroadcastSignum(0);
+
+namespace mozilla {
+
+static mozilla::Atomic<bool> gSandboxCrashOnError(false);
+
+// This is initialized by SandboxSetCrashFunc().
+SandboxCrashFunc gSandboxCrashFunc;
+
+static SandboxReporterClient* gSandboxReporterClient;
+static void (*gChromiumSigSysHandler)(int, siginfo_t*, void*);
+
+// Test whether a ucontext, interpreted as the state after a syscall,
+// indicates the given error.  See also sandbox::Syscall::PutValueInUcontext.
+static bool ContextIsError(const ucontext_t* aContext, int aError) {
+  // Avoid integer promotion warnings.  (The unary addition makes
+  // the decltype not evaluate to a reference type.)
+  typedef decltype(+SECCOMP_RESULT(aContext)) reg_t;
+
+#ifdef __mips__
+  return SECCOMP_PARM4(aContext) != 0 &&
+         SECCOMP_RESULT(aContext) == static_cast<reg_t>(aError);
+#else
+  return SECCOMP_RESULT(aContext) == static_cast<reg_t>(-aError);
+#endif
+}
+
+/**
+ * This is the SIGSYS handler function.  It delegates to the Chromium
+ * TrapRegistry handler (see InstallSigSysHandler, below) and, if the
+ * trap handler installed by the policy would fail with ENOSYS,
+ * crashes the process.  This allows unintentional policy failures to
+ * be reported as crash dumps and fixed.  It also logs information
+ * about the failed system call.
+ *
+ * Note that this could be invoked in parallel on multiple threads and
+ * that it could be in async signal context (e.g., intercepting an
+ * open() called from an async signal handler).
+ */
+MOZ_NEVER_INLINE static void SigSysHandler(int nr, siginfo_t* info,
+                                           void* void_context) {
+  ucontext_t* ctx = static_cast<ucontext_t*>(void_context);
+  // This shouldn't ever be null, but the Chromium handler checks for
+  // that and refrains from crashing, so let's not crash release builds:
+  MOZ_DIAGNOSTIC_ASSERT(ctx);
+  if (!ctx) {
+    return;
+  }
+
+  // Save a copy of the context before invoking the trap handler,
+  // which will overwrite one or more registers with the return value.
+  ucontext_t savedCtx = *ctx;
+
+  gChromiumSigSysHandler(nr, info, ctx);
+  if (!ContextIsError(ctx, ENOSYS)) {
+    return;
+  }
+
+  SandboxReport report = gSandboxReporterClient->MakeReportAndSend(&savedCtx);
+
+  // TODO, someday when this is enabled on MIPS: include the two extra
+  // args in the error message.
+  SANDBOX_LOG(
+      "seccomp sandbox violation: pid %d, tid %d, syscall %d,"
+      " args %d %d %d %d %d %d.%s",
+      report.mPid, report.mTid, report.mSyscall, report.mArgs[0],
+      report.mArgs[1], report.mArgs[2], report.mArgs[3], report.mArgs[4],
+      report.mArgs[5], gSandboxCrashOnError ? "  Killing process." : "");
+
+  if (gSandboxCrashOnError) {
+    // Bug 1017393: record syscall number somewhere useful.
+    info->si_addr = reinterpret_cast<void*>(report.mSyscall);
+
+    gSandboxCrashFunc(nr, info, &savedCtx, CallerPC());
+    _exit(127);
+  }
+}
+
+/**
+ * This function installs the SIGSYS handler.  This is slightly
+ * complicated because we want to use Chromium's handler to dispatch
+ * to specific trap handlers defined in the policy, but we also need
+ * the full original signal context to give to Breakpad for crash
+ * dumps.  So we install Chromium's handler first, then retrieve its
+ * address so our replacement can delegate to it.
+ */
+static void InstallSigSysHandler(void) {
+  struct sigaction act;
+
+  // Ensure that the Chromium handler is installed.
+  Unused << sandbox::Trap::Registry();
+
+  // If the signal handling state isn't as expected, crash now instead
+  // of crashing later (and more confusingly) when SIGSYS happens.
+
+  if (sigaction(SIGSYS, nullptr, &act) != 0) {
+    MOZ_CRASH("Couldn't read old SIGSYS disposition");
+  }
+  if ((act.sa_flags & SA_SIGINFO) != SA_SIGINFO) {
+    MOZ_CRASH("SIGSYS not already set to a siginfo handler?");
+  }
+  MOZ_RELEASE_ASSERT(act.sa_sigaction);
+  gChromiumSigSysHandler = act.sa_sigaction;
+  act.sa_sigaction = SigSysHandler;
+  // Currently, SA_NODEFER should already be set by the Chromium code,
+  // but it's harmless to ensure that it's set:
+  MOZ_ASSERT(act.sa_flags & SA_NODEFER);
+  act.sa_flags |= SA_NODEFER;
+  if (sigaction(SIGSYS, &act, nullptr) < 0) {
+    MOZ_CRASH("Couldn't change SIGSYS disposition");
+  }
+}
+
+/**
+ * This function installs the syscall filter, a.k.a. seccomp.  The
+ * aUseTSync flag indicates whether this should apply to all threads
+ * in the process -- which will fail if the kernel doesn't support
+ * that -- or only the current thread.
+ *
+ * SECCOMP_MODE_FILTER is the "bpf" mode of seccomp which allows
+ * to pass a bpf program (in our case, it contains a syscall
+ * whitelist).
+ *
+ * PR_SET_NO_NEW_PRIVS ensures that it is impossible to grant more
+ * syscalls to the process beyond this point (even after fork()), and
+ * prevents gaining capabilities (e.g., by exec'ing a setuid root
+ * program).  The kernel won't allow seccomp-bpf without doing this,
+ * because otherwise it could be used for privilege escalation attacks.
+ *
+ * Returns false if the filter was already installed (see the
+ * PR_SET_NO_NEW_PRIVS rule in SandboxFilter.cpp).  Crashes on any
+ * other error condition.
+ *
+ * @see SandboxInfo
+ * @see BroadcastSetThreadSandbox
+ */
+[[nodiscard]] static bool InstallSyscallFilter(const sock_fprog* aProg,
+                                               bool aUseTSync) {
+  if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+    if (!aUseTSync && errno == ETXTBSY) {
+      return false;
+    }
+    SANDBOX_LOG_ERRNO("prctl(PR_SET_NO_NEW_PRIVS) failed");
+    MOZ_CRASH("prctl(PR_SET_NO_NEW_PRIVS)");
+  }
+
+  if (aUseTSync) {
+    // Try with SECCOMP_FILTER_FLAGS_SPEC_ALLOW, and then without if
+    // that fails with EINVAL (or if an env var is set, for testing
+    // purposes).
+    //
+    // Context: Linux 4.17 applied some Spectre mitigations (SSBD and
+    // STIBP) by default when seccomp-bpf is used, but also added that
+    // flag to opt out (and also sysadmin-level overrides).  Later,
+    // Linux 5.16 turned them off by default; the rationale seems to
+    // be, roughly: the attacks are impractical or were already
+    // mitigated in other ways, there are worse attacks that these
+    // measures don't stop, and the performance impact is severe
+    // enough that container software was already opting out.
+    //
+    // For the full rationale, see
+    // https://github.com/torvalds/linux/commit/2f46993d83ff4abb310e
+    //
+    // In our case, STIBP causes a noticeable performance hit: WASM
+    // microbenchmarks of indirect calls regress by up to 2x or 3x
+    // depending on CPU.  Given that upstream Linux has changed the
+    // default years ago, we opt out.
+
+    static const bool kSpecAllow = !PR_GetEnv("MOZ_SANDBOX_NO_SPEC_ALLOW");
+
+    const auto setSeccomp = [aProg](int aFlags) -> long {
+      return syscall(__NR_seccomp, SECCOMP_SET_MODE_FILTER,
+                     SECCOMP_FILTER_FLAG_TSYNC | aFlags, aProg);
+    };
+
+    long rv;
+    if (kSpecAllow) {
+      rv = setSeccomp(SECCOMP_FILTER_FLAG_SPEC_ALLOW);
+    } else {
+      rv = -1;
+      errno = EINVAL;
+    }
+    if (rv != 0 && errno == EINVAL) {
+      rv = setSeccomp(0);
+    }
+    if (rv != 0) {
+      SANDBOX_LOG_ERRNO("thread-synchronized seccomp failed");
+      MOZ_CRASH("seccomp+tsync failed, but kernel supports tsync");
+    }
+  } else {
+    if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, (unsigned long)aProg, 0,
+              0)) {
+      SANDBOX_LOG_ERRNO("prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER) failed");
+      MOZ_CRASH("prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER)");
+    }
+  }
+  return true;
+}
+
+// Use signals for permissions that need to be set per-thread.
+// The communication channel from the signal handler back to the main thread.
+static mozilla::Atomic<int> gSetSandboxDone;
+// Pass the filter itself through a global.
+const sock_fprog* gSetSandboxFilter;
+
+// We have to dynamically allocate the signal number; see bug 1038900.
+// This function returns the first realtime signal currently set to
+// default handling (i.e., not in use), or 0 if none could be found.
+//
+// WARNING: if this function or anything similar to it (including in
+// external libraries) is used on multiple threads concurrently, there
+// will be a race condition.
+static int FindFreeSignalNumber() {
+  for (int signum = SIGRTMAX; signum >= SIGRTMIN; --signum) {
+    struct sigaction sa;
+
+    if (sigaction(signum, nullptr, &sa) == 0 &&
+        (sa.sa_flags & SA_SIGINFO) == 0 && sa.sa_handler == SIG_DFL) {
+      return signum;
+    }
+  }
+  return 0;
+}
+
+// Returns true if sandboxing was enabled, or false if sandboxing
+// already was enabled.  Crashes if sandboxing could not be enabled.
+static bool SetThreadSandbox() {
+  return InstallSyscallFilter(gSetSandboxFilter, false);
+}
+
+static void SetThreadSandboxHandler(int signum) {
+  // The non-zero number sent back to the main thread indicates
+  // whether action was taken.
+  if (SetThreadSandbox()) {
+    gSetSandboxDone = 2;
+  } else {
+    gSetSandboxDone = 1;
+  }
+  // Wake up the main thread.  See the FUTEX_WAIT call, below, for an
+  // explanation.
+  syscall(__NR_futex, reinterpret_cast<int*>(&gSetSandboxDone), FUTEX_WAKE, 1);
+}
+
+static void EnterChroot() {
+  const char* env = PR_GetEnv(kSandboxChrootEnvFlag);
+  if (!env || !*env || *env == '0') {
+    return;
+  }
+  char msg = kSandboxChrootRequest;
+  ssize_t msg_len = HANDLE_EINTR(write(kSandboxChrootClientFd, &msg, 1));
+  MOZ_RELEASE_ASSERT(msg_len == 1);
+  msg_len = HANDLE_EINTR(read(kSandboxChrootClientFd, &msg, 1));
+  MOZ_RELEASE_ASSERT(msg_len == 1);
+  MOZ_RELEASE_ASSERT(msg == kSandboxChrootResponse);
+  close(kSandboxChrootClientFd);
+}
+
+static void BroadcastSetThreadSandbox(const sock_fprog* aFilter) {
+  pid_t pid, tid, myTid;
+  DIR* taskdp;
+  struct dirent* de;
+
+  // This function does not own *aFilter, so this global needs to
+  // always be zeroed before returning.
+  gSetSandboxFilter = aFilter;
+
+  static_assert(sizeof(mozilla::Atomic<int>) == sizeof(int),
+                "mozilla::Atomic<int> isn't represented by an int");
+  pid = getpid();
+  myTid = syscall(__NR_gettid);
+  taskdp = opendir("/proc/self/task");
+  if (taskdp == nullptr) {
+    SANDBOX_LOG_ERRNO("opendir /proc/self/task");
+    MOZ_CRASH("failed while trying to open directory /proc/self/task");
+  }
+
+  // In case this races with a not-yet-deprivileged thread cloning
+  // itself, repeat iterating over all threads until we find none
+  // that are still privileged.
+  bool sandboxProgress;
+  const int tsyncSignum = gSeccompTsyncBroadcastSignum;
+  do {
+    sandboxProgress = false;
+    // For each thread...
+    while ((de = readdir(taskdp))) {
+      char* endptr;
+      tid = strtol(de->d_name, &endptr, 10);
+      if (*endptr != '\0' || tid <= 0) {
+        // Not a task ID.
+        continue;
+      }
+      if (tid == myTid) {
+        // Drop this thread's privileges last, below, so we can
+        // continue to signal other threads.
+        continue;
+      }
+
+      MOZ_RELEASE_ASSERT(tsyncSignum != 0);
+
+      // Reset the futex cell and signal.
+      gSetSandboxDone = 0;
+      if (syscall(__NR_tgkill, pid, tid, tsyncSignum) != 0) {
+        if (errno == ESRCH) {
+          SANDBOX_LOG("Thread %d unexpectedly exited.", tid);
+          // Rescan threads, in case it forked before exiting.
+          sandboxProgress = true;
+          continue;
+        }
+        SANDBOX_LOG_ERRNO("tgkill(%d,%d)", pid, tid);
+        MOZ_CRASH("failed while trying to send a signal to a thread");
+      }
+      // It's unlikely, but if the thread somehow manages to exit
+      // after receiving the signal but before entering the signal
+      // handler, we need to avoid blocking forever.
+      //
+      // Using futex directly lets the signal handler send the wakeup
+      // from an async signal handler (pthread mutex/condvar calls
+      // aren't allowed), and to use a relative timeout that isn't
+      // affected by changes to the system clock (not possible with
+      // POSIX semaphores).
+      //
+      // If a thread doesn't respond within a reasonable amount of
+      // time, but still exists, we crash -- the alternative is either
+      // blocking forever or silently losing security, and it
+      // shouldn't actually happen.
+      static const int crashDelay = 10;  // seconds
+      struct timespec timeLimit;
+      clock_gettime(CLOCK_MONOTONIC, &timeLimit);
+      timeLimit.tv_sec += crashDelay;
+      while (true) {
+        static const struct timespec futexTimeout = {0,
+                                                     10 * 1000 * 1000};  // 10ms
+        // Atomically: if gSetSandboxDone == 0, then sleep.
+        if (syscall(__NR_futex, reinterpret_cast<int*>(&gSetSandboxDone),
+                    FUTEX_WAIT, 0, &futexTimeout) != 0) {
+          if (errno != EWOULDBLOCK && errno != ETIMEDOUT && errno != EINTR) {
+            SANDBOX_LOG_ERRNO("FUTEX_WAIT");
+            MOZ_CRASH("failed during FUTEX_WAIT");
+          }
+        }
+        // Did the handler finish?
+        if (gSetSandboxDone > 0) {
+          if (gSetSandboxDone == 2) {
+            sandboxProgress = true;
+          }
+          break;
+        }
+        // Has the thread ceased to exist?
+        if (syscall(__NR_tgkill, pid, tid, 0) != 0) {
+          if (errno == ESRCH) {
+            SANDBOX_LOG("Thread %d unexpectedly exited.", tid);
+          }
+          // Rescan threads, in case it forked before exiting.
+          // Also, if it somehow failed in a way that wasn't ESRCH,
+          // and still exists, that will be handled on the next pass.
+          sandboxProgress = true;
+          break;
+        }
+        struct timespec now;
+        clock_gettime(CLOCK_MONOTONIC, &now);
+        if (now.tv_sec > timeLimit.tv_sec ||
+            (now.tv_sec == timeLimit.tv_sec &&
+             now.tv_nsec > timeLimit.tv_nsec)) {
+          SANDBOX_LOG(
+              "Thread %d unresponsive for %d seconds."
+              "  Killing process.",
+              tid, crashDelay);
+
+          MOZ_CRASH("failed while waiting for unresponsive thread");
+        }
+      }
+    }
+    rewinddir(taskdp);
+  } while (sandboxProgress);
+
+  void (*oldHandler)(int);
+  oldHandler = signal(tsyncSignum, SIG_DFL);
+  if (oldHandler != SetThreadSandboxHandler) {
+    // See the comment on FindFreeSignalNumber about race conditions.
+    SANDBOX_LOG("handler for signal %d was changed to %p!", tsyncSignum,
+                oldHandler);
+    MOZ_CRASH("handler for the signal was changed to another");
+  }
+  gSeccompTsyncBroadcastSignum = 0;
+  Unused << closedir(taskdp);
+  // And now, deprivilege the main thread:
+  SetThreadSandbox();
+  gSetSandboxFilter = nullptr;
+}
+
+static void ApplySandboxWithTSync(sock_fprog* aFilter) {
+  // At this point we're committed to using tsync, because we'd have
+  // needed to allocate a signal and prevent it from being blocked on
+  // other threads (see SandboxHooks.cpp), so there's no attempt to
+  // fall back to the non-tsync path.
+  if (!InstallSyscallFilter(aFilter, true)) {
+    MOZ_CRASH("failed while trying to install syscall filter");
+  }
+}
+
+#ifdef NIGHTLY_BUILD
+static bool IsLibPresent(const char* aName) {
+  if (const auto handle = dlopen(aName, RTLD_LAZY | RTLD_NOLOAD)) {
+    dlclose(handle);
+    return true;
+  }
+  return false;
+}
+
+static const Array<const char*, 1> kLibsThatWillCrash{
+    "libesets_pac.so",
+};
+#endif  // NIGHTLY_BUILD
+
+void SandboxEarlyInit() {
+  if (PR_GetEnv("MOZ_SANDBOXED") == nullptr) {
+    return;
+  }
+
+  // Fix LD_PRELOAD for any child processes.  See bug 1434392 comment #10;
+  // this can probably go away when audio remoting is mandatory.
+  const char* oldPreload = PR_GetEnv("MOZ_ORIG_LD_PRELOAD");
+  char* preloadEntry;
+  // This string is "leaked" because the environment takes ownership.
+  if (asprintf(&preloadEntry, "LD_PRELOAD=%s", oldPreload ? oldPreload : "") !=
+      -1) {
+    PR_SetEnv(preloadEntry);
+  }
+
+  // If TSYNC is not supported, set up signal handler
+  // used to enable seccomp on each thread.
+  if (!SandboxInfo::Get().Test(SandboxInfo::kHasSeccompTSync)) {
+    // The signal number has to be chosen early, so that the
+    // interceptions in SandboxHooks.cpp can prevent it from being
+    // masked.
+    const int tsyncSignum = FindFreeSignalNumber();
+    if (tsyncSignum == 0) {
+      SANDBOX_LOG("No available signal numbers!");
+      MOZ_CRASH("failed while trying to find a free signal number");
+    }
+    gSeccompTsyncBroadcastSignum = tsyncSignum;
+
+    // ...and the signal handler also needs to be installed now, to
+    // indicate to anything else looking for free signals that it's
+    // claimed.
+    void (*oldHandler)(int);
+    oldHandler = signal(tsyncSignum, SetThreadSandboxHandler);
+    if (oldHandler != SIG_DFL) {
+      // See the comment on FindFreeSignalNumber about race conditions.
+      if (oldHandler == SIG_ERR) {
+        MOZ_CRASH("failed while registering the signal handler");
+      } else {
+        MOZ_CRASH("failed because the signal is in use by another handler");
+      }
+      SANDBOX_LOG("signal %d in use by handler %p!\n", tsyncSignum, oldHandler);
+    }
+  }
+}
+
+static void RunGlibcLazyInitializers() {
+  // Make glibc's lazy initialization of shm_open() run before sandboxing
+  int fd = shm_open("/dummy", O_RDONLY, 0);
+  if (fd > 0) {
+    close(fd);  // In the unlikely case we actually opened something
+  }
+}
+
+static void SandboxLateInit() {
+#ifdef NIGHTLY_BUILD
+  gSandboxCrashOnError = true;
+  for (const char* name : kLibsThatWillCrash) {
+    if (IsLibPresent(name)) {
+      gSandboxCrashOnError = false;
+      break;
+    }
+  }
+#endif
+
+  if (const char* envVar = PR_GetEnv("MOZ_SANDBOX_CRASH_ON_ERROR")) {
+    if (envVar[0]) {
+      gSandboxCrashOnError = envVar[0] != '0';
+    }
+  }
+
+  RunGlibcLazyInitializers();
+}
+
+// Common code for sandbox startup.
+static void SetCurrentProcessSandbox(
+    UniquePtr<sandbox::bpf_dsl::Policy> aPolicy) {
+  MOZ_ASSERT(gSandboxCrashFunc);
+  MOZ_RELEASE_ASSERT(gSandboxReporterClient != nullptr);
+  SandboxLateInit();
+
+  // Auto-collect child processes -- mainly the chroot helper if
+  // present, but also anything setns()ed into the pid namespace (not
+  // yet implemented).  This process won't be able to waitpid them
+  // after the seccomp-bpf policy is applied.
+  signal(SIGCHLD, SIG_IGN);
+
+  // Note: PolicyCompiler borrows the policy and registry for its
+  // lifetime, but does not take ownership of them.
+  sandbox::bpf_dsl::PolicyCompiler compiler(aPolicy.get(),
+                                            sandbox::Trap::Registry());
+
+  // In case of errors detected by the compiler (like ABI violations),
+  // log and crash normally; the default is SECCOMP_RET_KILL_THREAD,
+  // which results in hard-to-debug hangs.
+  compiler.SetPanicFunc([](const char* error) -> sandbox::bpf_dsl::ResultExpr {
+    // Note: this assumes that `error` is a string literal, which is
+    // currently the case for all callers.  (An intentionally leaked
+    // heap allocation would also work.)
+    return sandbox::bpf_dsl::Trap(
+        [](const sandbox::arch_seccomp_data&, void* aux) -> intptr_t {
+          auto error = reinterpret_cast<const char*>(aux);
+          SANDBOX_LOG("Panic: %s", error);
+          MOZ_CRASH("Sandbox Panic");
+          // unreachable
+        },
+        (void*)error);
+  });
+
+  sandbox::CodeGen::Program program = compiler.Compile();
+  if (SandboxInfo::Get().Test(SandboxInfo::kVerbose)) {
+    sandbox::bpf_dsl::DumpBPF::PrintProgram(program);
+  }
+
+  InstallSigSysHandler();
+
+#ifdef MOZ_ASAN
+  __sanitizer_sandbox_arguments asanArgs;
+  asanArgs.coverage_sandboxed = 1;
+  asanArgs.coverage_fd = -1;
+  asanArgs.coverage_max_block_size = 0;
+  __sanitizer_sandbox_on_notify(&asanArgs);
+#endif
+
+  // The syscall takes a C-style array, so copy the vector into one.
+  size_t programLen = program.size();
+  UniquePtr<sock_filter[]> flatProgram(new sock_filter[programLen]);
+  for (auto i = program.begin(); i != program.end(); ++i) {
+    flatProgram[i - program.begin()] = *i;
+  }
+
+  sock_fprog fprog;
+  fprog.filter = flatProgram.get();
+  fprog.len = static_cast<unsigned short>(programLen);
+  MOZ_RELEASE_ASSERT(static_cast<size_t>(fprog.len) == programLen);
+
+  const SandboxInfo info = SandboxInfo::Get();
+  if (info.Test(SandboxInfo::kHasSeccompTSync)) {
+    if (info.Test(SandboxInfo::kVerbose)) {
+      SANDBOX_LOG("using seccomp tsync");
+    }
+    ApplySandboxWithTSync(&fprog);
+  } else {
+    if (info.Test(SandboxInfo::kVerbose)) {
+      SANDBOX_LOG("no tsync support; using signal broadcast");
+    }
+    BroadcastSetThreadSandbox(&fprog);
+  }
+
+  // Now that all threads' filesystem accesses are being intercepted
+  // (if a broker is used) it's safe to chroot the process:
+  EnterChroot();
+}
+
+/**
+ * Starts the seccomp sandbox for a content process.  Should be called
+ * only once, and before any potentially harmful content is loaded.
+ *
+ * Will normally make the process exit on failure.
+ */
+bool SetContentProcessSandbox(ContentProcessSandboxParams&& aParams) {
+  int brokerFd = aParams.mBrokerFd;
+  aParams.mBrokerFd = -1;
+
+  if (!SandboxInfo::Get().Test(SandboxInfo::kEnabledForContent)) {
+    if (brokerFd >= 0) {
+      close(brokerFd);
+    }
+    return false;
+  }
+
+  auto procType = aParams.mFileProcess ? SandboxReport::ProcType::FILE
+                                       : SandboxReport::ProcType::CONTENT;
+  gSandboxReporterClient = new SandboxReporterClient(procType);
+
+  // This needs to live until the process exits.
+  static SandboxBrokerClient* sBroker;
+  if (brokerFd >= 0) {
+    sBroker = new SandboxBrokerClient(brokerFd);
+  }
+
+  SetCurrentProcessSandbox(
+      GetContentSandboxPolicy(sBroker, std::move(aParams)));
+  return true;
+}
+/**
+ * Starts the seccomp sandbox for a media plugin process.  Should be
+ * called only once, and before any potentially harmful content is
+ * loaded -- including the plugin itself, if it's considered untrusted.
+ *
+ * The file indicated by aFilePath, if non-null, can be open()ed
+ * read-only, once, after the sandbox starts; it should be the .so
+ * file implementing the not-yet-loaded plugin.
+ *
+ * Will normally make the process exit on failure.
+ */
+void SetMediaPluginSandbox(const char* aFilePath) {
+  MOZ_RELEASE_ASSERT(aFilePath != nullptr);
+  if (!SandboxInfo::Get().Test(SandboxInfo::kEnabledForMedia)) {
+    return;
+  }
+
+  gSandboxReporterClient =
+      new SandboxReporterClient(SandboxReport::ProcType::MEDIA_PLUGIN);
+
+  SandboxOpenedFile plugin(aFilePath);
+  if (!plugin.IsOpen()) {
+    SANDBOX_LOG_ERRNO("failed to open plugin file %s", aFilePath);
+    MOZ_CRASH("failed while trying to open the plugin file ");
+  }
+
+  auto files = new SandboxOpenedFiles();
+  files->Add(std::move(plugin));
+  files->Add("/dev/urandom", SandboxOpenedFile::Dup::YES);
+  files->Add("/dev/random", SandboxOpenedFile::Dup::YES);
+  files->Add("/etc/ld.so.cache");  // Needed for NSS in clearkey.
+  files->Add("/sys/devices/system/cpu/cpu0/tsc_freq_khz");
+  files->Add("/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq");
+  files->Add("/proc/cpuinfo");  // Info also available via CPUID instruction.
+  files->Add("/proc/sys/crypto/fips_enabled");  // Needed for NSS in clearkey.
+#ifdef __i386__
+  files->Add("/proc/self/auxv");  // Info also in process's address space.
+#endif
+  // Bug 1712506: the Widevine CDM will try to access these but
+  // doesn't appear to need them.
+  files->Add("/sys/devices/system/cpu/online", SandboxOpenedFile::Error{});
+  files->Add("/proc/stat", SandboxOpenedFile::Error{});
+  files->Add("/proc/net/unix", SandboxOpenedFile::Error{});
+  files->Add("/proc/self/maps", SandboxOpenedFile::Error{});
+
+  // Finally, start the sandbox.
+  SetCurrentProcessSandbox(GetMediaSandboxPolicy(files));
+}
+
+void SetRemoteDataDecoderSandbox(int aBroker) {
+  if (!SandboxInfo::Get().Test(SandboxInfo::kHasSeccompBPF) ||
+      PR_GetEnv("MOZ_DISABLE_RDD_SANDBOX")) {
+    if (aBroker >= 0) {
+      close(aBroker);
+    }
+    return;
+  }
+
+  gSandboxReporterClient =
+      new SandboxReporterClient(SandboxReport::ProcType::RDD);
+
+  // FIXME(bug 1513773): merge this with the one for content?
+  static SandboxBrokerClient* sBroker;
+  if (aBroker >= 0) {
+    sBroker = new SandboxBrokerClient(aBroker);
+  }
+
+  SetCurrentProcessSandbox(GetDecoderSandboxPolicy(sBroker));
+}
+
+void SetSocketProcessSandbox(int aBroker) {
+  if (!SandboxInfo::Get().Test(SandboxInfo::kHasSeccompBPF) ||
+      PR_GetEnv("MOZ_DISABLE_SOCKET_PROCESS_SANDBOX")) {
+    if (aBroker >= 0) {
+      close(aBroker);
+    }
+    return;
+  }
+
+  gSandboxReporterClient =
+      new SandboxReporterClient(SandboxReport::ProcType::SOCKET_PROCESS);
+
+  static SandboxBrokerClient* sBroker;
+  if (aBroker >= 0) {
+    sBroker = new SandboxBrokerClient(aBroker);
+  }
+
+  SetCurrentProcessSandbox(GetSocketProcessSandboxPolicy(sBroker));
+}
+
+void SetUtilitySandbox(int aBroker, ipc::SandboxingKind aKind) {
+  if (!SandboxInfo::Get().Test(SandboxInfo::kHasSeccompBPF) ||
+      !IsUtilitySandboxEnabled(aKind)) {
+    if (aBroker >= 0) {
+      close(aBroker);
+    }
+    return;
+  }
+
+  gSandboxReporterClient =
+      new SandboxReporterClient(SandboxReport::ProcType::UTILITY);
+
+  static SandboxBrokerClient* sBroker;
+  if (aBroker >= 0) {
+    sBroker = new SandboxBrokerClient(aBroker);
+  }
+
+  UniquePtr<sandbox::bpf_dsl::Policy> policy;
+  switch (aKind) {
+    case ipc::SandboxingKind::GENERIC_UTILITY:
+      policy = GetUtilitySandboxPolicy(sBroker);
+      break;
+
+    default:
+      MOZ_ASSERT(false, "Invalid SandboxingKind");
+      break;
+  }
+
+  SetCurrentProcessSandbox(std::move(policy));
+}
+
+bool SetSandboxCrashOnError(bool aValue) {
+  bool oldValue = gSandboxCrashOnError;
+  gSandboxCrashOnError = aValue;
+  return oldValue;
+}
+
+}  // namespace mozilla