blob: 6b15562119094fa40c308f2f066a8d9b5402beab [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <memory>
#include <string>
#include <vector>
#include "base/logging.h"
#include "base/macros.h"
#include "base/posix/global_descriptors.h"
#include "content/public/common/content_descriptors.h"
#include "content/public/common/sandbox_linux.h"
#if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
defined(THREAD_SANITIZER) || defined(LEAK_SANITIZER) || \
#include <sanitizer/common_interface_defs.h>
namespace base {
template <typename T>
struct DefaultSingletonTraits;
class Thread;
namespace sandbox { class SetuidSandboxClient; }
namespace content {
inline int GetSandboxFD() {
return kSandboxIPCChannel + base::GlobalDescriptors::kBaseDescriptor;
// A singleton class to represent and change our sandboxing state for the
// three main Linux sandboxes.
// The sandboxing model allows using two layers of sandboxing. The first layer
// can be implemented either with unprivileged namespaces or with the setuid
// sandbox. This class provides a way to engage the namespace sandbox, but does
// not deal with the legacy setuid sandbox directly.
// The second layer is mainly based on seccomp-bpf and is engaged with
// InitializeSandbox(). InitializeSandbox() is also responsible for "sealing"
// the first layer of sandboxing. That is, InitializeSandbox must always be
// called to have any meaningful sandboxing at all.
class LinuxSandbox {
// This is a list of sandbox IPC methods which the renderer may send to the
// sandbox host. See
// This isn't the full list, values < 32 are reserved for methods called from
// Skia.
enum LinuxSandboxIPCMethods {
// Get our singleton instance.
static LinuxSandbox* GetInstance();
// Do some initialization that can only be done before any of the sandboxes
// are enabled. If using the setuid sandbox, this should be called manually
// before the setuid sandbox is engaged.
// Security: When this runs, it is imperative that either InitializeSandbox()
// runs as well or that all file descriptors returned in
// GetFileDescriptorsToClose() get closed.
// Otherwise file descriptors that bypass the security of the setuid sandbox
// would be kept open. One must be particularly careful if a process performs
// a fork().
void PreinitializeSandbox();
// Check that the current process is the init process of a new PID
// namespace and then proceed to drop access to the file system by using
// a new unprivileged namespace. This is a layer-1 sandbox.
// In order for this sandbox to be effective, it must be "sealed" by calling
// InitializeSandbox().
void EngageNamespaceSandbox();
// Return a list of file descriptors to close if PreinitializeSandbox() ran
// but InitializeSandbox() won't. Avoid using.
// TODO(jln): get rid of this hack.
std::vector<int> GetFileDescriptorsToClose();
// Seal an eventual layer-1 sandbox and initialize the layer-2 sandbox with
// an adequate policy depending on the process type and command line
// arguments.
// Currently the layer-2 sandbox is composed of seccomp-bpf and address space
// limitations. This will instantiate the LinuxSandbox singleton if it
// doesn't already exist.
// This function should only be called without any thread running.
static bool InitializeSandbox();
// Stop |thread| in a way that can be trusted by the sandbox.
static void StopThread(base::Thread* thread);
// Returns the status of the renderer, worker and ppapi sandbox. Can only
// be queried after going through PreinitializeSandbox(). This is a bitmask
// and uses the constants defined in "enum LinuxSandboxStatus". Since the
// status needs to be provided before the sandboxes are actually started,
// this returns what will actually happen once InitializeSandbox()
// is called from inside these processes.
int GetStatus();
// Returns true if the current process is single-threaded or if the number
// of threads cannot be determined.
bool IsSingleThreaded() const;
// Did we start Seccomp BPF?
bool seccomp_bpf_started() const;
// Simple accessor for our instance of the setuid sandbox. Will never return
// NULL.
// There is no StartSetuidSandbox(), the SetuidSandboxClient instance should
// be used directly.
sandbox::SetuidSandboxClient* setuid_sandbox_client() const;
// Check the policy and eventually start the seccomp-bpf sandbox. This should
// never be called with threads started. If we detect that threads have
// started we will crash.
bool StartSeccompBPF(const std::string& process_type);
// Limit the address space of the current process (and its children).
// to make some vulnerabilities harder to exploit.
bool LimitAddressSpace(const std::string& process_type);
// Returns a file descriptor to proc. The file descriptor is no longer valid
// after the sandbox has been sealed.
int proc_fd() const {
DCHECK_NE(-1, proc_fd_);
return proc_fd_;
__sanitizer_sandbox_arguments* sanitizer_args() const {
return sanitizer_args_.get();
friend struct base::DefaultSingletonTraits<LinuxSandbox>;
// Some methods are static and get an instance of the Singleton. These
// are the non-static implementations.
bool InitializeSandboxImpl();
void StopThreadImpl(base::Thread* thread);
// We must have been pre_initialized_ before using these.
bool seccomp_bpf_supported() const;
bool seccomp_bpf_with_tsync_supported() const;
// Returns true if it can be determined that the current process has open
// directories that are not managed by the LinuxSandbox class. This would
// be a vulnerability as it would allow to bypass the setuid sandbox.
bool HasOpenDirectories() const;
// The last part of the initialization is to make sure any temporary "hole"
// in the sandbox is closed. For now, this consists of closing proc_fd_.
void SealSandbox();
// GetStatus() makes promises as to how the sandbox will behave. This
// checks that no promises have been broken.
void CheckForBrokenPromises(const std::string& process_type);
// Stop |thread| and make sure it does not appear in /proc/self/tasks/
// anymore.
void StopThreadAndEnsureNotCounted(base::Thread* thread) const;
// A file descriptor to /proc. It's dangerous to have it around as it could
// allow for sandbox bypasses. It needs to be closed before we consider
// ourselves sandboxed.
int proc_fd_;
bool seccomp_bpf_started_;
// The value returned by GetStatus(). Gets computed once and then cached.
int sandbox_status_flags_;
// Did PreinitializeSandbox() run?
bool pre_initialized_;
bool seccomp_bpf_supported_; // Accurate if pre_initialized_.
bool seccomp_bpf_with_tsync_supported_; // Accurate if pre_initialized_.
bool yama_is_enforcing_; // Accurate if pre_initialized_.
bool initialize_sandbox_ran_; // InitializeSandbox() was called.
std::unique_ptr<sandbox::SetuidSandboxClient> setuid_sandbox_client_;
std::unique_ptr<__sanitizer_sandbox_arguments> sanitizer_args_;
} // namespace content