content/common/sandbox_linux/sandbox_linux.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CONTENT_COMMON_SANDBOX_LINUX_SANDBOX_LINUX_H_
   6 #define CONTENT_COMMON_SANDBOX_LINUX_SANDBOX_LINUX_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "content/public/common/sandbox_linux.h"
  14
  15 #if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
  16     defined(THREAD_SANITIZER) || defined(LEAK_SANITIZER) || \
  17     defined(UNDEFINED_SANITIZER) || defined(SANITIZER_COVERAGE)
  18 #include <sanitizer/common_interface_defs.h>
  19 #define ANY_OF_AMTLU_SANITIZER 1
  20 #endif
  21
  22 template <typename T> struct DefaultSingletonTraits;
  23 namespace base {
  24 class Thread;
  25 }
  26 namespace sandbox { class SetuidSandboxClient; }
  27
  28 namespace content {
  29
  30 // A singleton class to represent and change our sandboxing state for the
  31 // three main Linux sandboxes.
  32 // The sandboxing model allows using two layers of sandboxing. The first layer
  33 // can be implemented either with unprivileged namespaces or with the setuid
  34 // sandbox. This class provides a way to engage the namespace sandbox, but does
  35 // not deal with the legacy setuid sandbox directly.
  36 // The second layer is mainly based on seccomp-bpf and is engaged with
  37 // InitializeSandbox(). InitializeSandbox() is also responsible for "sealing"
  38 // the first layer of sandboxing. That is, InitializeSandbox must always be
  39 // called to have any meaningful sandboxing at all.
  40 class LinuxSandbox {
  41  public:
  42   // This is a list of sandbox IPC methods which the renderer may send to the
  43   // sandbox host. See http://code.google.com/p/chromium/wiki/LinuxSandboxIPC
  44   // This isn't the full list, values < 32 are reserved for methods called from
  45   // Skia.
  46   enum LinuxSandboxIPCMethods {
  47     METHOD_GET_FALLBACK_FONT_FOR_CHAR = 32,
  48     METHOD_LOCALTIME = 33,
  49     DEPRECATED_METHOD_GET_CHILD_WITH_INODE = 34,
  50     METHOD_GET_STYLE_FOR_STRIKE = 35,
  51     METHOD_MAKE_SHARED_MEMORY_SEGMENT = 36,
  52     METHOD_MATCH_WITH_FALLBACK = 37,
  53   };
  54
  55   // Get our singleton instance.
  56   static LinuxSandbox* GetInstance();
  57
  58   // Do some initialization that can only be done before any of the sandboxes
  59   // are enabled. If using the setuid sandbox, this should be called manually
  60   // before the setuid sandbox is engaged.
  61   // Security: When this runs, it is imperative that either InitializeSandbox()
  62   // runs as well or that all file descriptors returned in
  63   // GetFileDescriptorsToClose() get closed.
  64   // Otherwise file descriptors that bypass the security of the setuid sandbox
  65   // would be kept open. One must be particularly careful if a process performs
  66   // a fork().
  67   void PreinitializeSandbox();
  68
  69   // Check that the current process is the init process of a new PID
  70   // namespace and then proceed to drop access to the file system by using
  71   // a new unprivileged namespace. This is a layer-1 sandbox.
  72   // In order for this sandbox to be effective, it must be "sealed" by calling
  73   // InitializeSandbox().
  74   void EngageNamespaceSandbox();
  75
  76   // Return a list of file descriptors to close if PreinitializeSandbox() ran
  77   // but InitializeSandbox() won't. Avoid using.
  78   // TODO(jln): get rid of this hack.
  79   std::vector<int> GetFileDescriptorsToClose();
  80
  81   // Seal an eventual layer-1 sandbox and initialize the layer-2 sandbox with
  82   // an adequate policy depending on the process type and command line
  83   // arguments.
  84   // Currently the layer-2 sandbox is composed of seccomp-bpf and address space
  85   // limitations. This will instantiate the LinuxSandbox singleton if it
  86   // doesn't already exist.
  87   // This function should only be called without any thread running.
  88   static bool InitializeSandbox();
  89
  90   // Stop |thread| in a way that can be trusted by the sandbox.
  91   static void StopThread(base::Thread* thread);
  92
  93   // Returns the status of the renderer, worker and ppapi sandbox. Can only
  94   // be queried after going through PreinitializeSandbox(). This is a bitmask
  95   // and uses the constants defined in "enum LinuxSandboxStatus". Since the
  96   // status needs to be provided before the sandboxes are actually started,
  97   // this returns what will actually happen once InitializeSandbox()
  98   // is called from inside these processes.
  99   int GetStatus();
 100   // Returns true if the current process is single-threaded or if the number
 101   // of threads cannot be determined.
 102   bool IsSingleThreaded() const;
 103   // Did we start Seccomp BPF?
 104   bool seccomp_bpf_started() const;
 105
 106   // Simple accessor for our instance of the setuid sandbox. Will never return
 107   // NULL.
 108   // There is no StartSetuidSandbox(), the SetuidSandboxClient instance should
 109   // be used directly.
 110   sandbox::SetuidSandboxClient* setuid_sandbox_client() const;
 111
 112   // Check the policy and eventually start the seccomp-bpf sandbox. This should
 113   // never be called with threads started. If we detect that threads have
 114   // started we will crash.
 115   bool StartSeccompBPF(const std::string& process_type);
 116
 117   // Limit the address space of the current process (and its children).
 118   // to make some vulnerabilities harder to exploit.
 119   bool LimitAddressSpace(const std::string& process_type);
 120
 121 #if defined(ANY_OF_AMTLU_SANITIZER)
 122   __sanitizer_sandbox_arguments* sanitizer_args() const {
 123     return sanitizer_args_.get();
 124   };
 125 #endif
 126
 127  private:
 128   friend struct DefaultSingletonTraits<LinuxSandbox>;
 129
 130   LinuxSandbox();
 131   ~LinuxSandbox();
 132
 133   // Some methods are static and get an instance of the Singleton. These
 134   // are the non-static implementations.
 135   bool InitializeSandboxImpl();
 136   void StopThreadImpl(base::Thread* thread);
 137   // We must have been pre_initialized_ before using these.
 138   bool seccomp_bpf_supported() const;
 139   bool seccomp_bpf_with_tsync_supported() const;
 140   // Returns true if it can be determined that the current process has open
 141   // directories that are not managed by the LinuxSandbox class. This would
 142   // be a vulnerability as it would allow to bypass the setuid sandbox.
 143   bool HasOpenDirectories() const;
 144   // The last part of the initialization is to make sure any temporary "hole"
 145   // in the sandbox is closed. For now, this consists of closing proc_fd_.
 146   void SealSandbox();
 147   // GetStatus() makes promises as to how the sandbox will behave. This
 148   // checks that no promises have been broken.
 149   void CheckForBrokenPromises(const std::string& process_type);
 150   // Stop |thread| and make sure it does not appear in /proc/self/tasks/
 151   // anymore.
 152   void StopThreadAndEnsureNotCounted(base::Thread* thread) const;
 153
 154   // A file descriptor to /proc. It's dangerous to have it around as it could
 155   // allow for sandbox bypasses. It needs to be closed before we consider
 156   // ourselves sandboxed.
 157   int proc_fd_;
 158   bool seccomp_bpf_started_;
 159   // The value returned by GetStatus(). Gets computed once and then cached.
 160   int sandbox_status_flags_;
 161   // Did PreinitializeSandbox() run?
 162   bool pre_initialized_;
 163   bool seccomp_bpf_supported_;  // Accurate if pre_initialized_.
 164   bool seccomp_bpf_with_tsync_supported_;  // Accurate if pre_initialized_.
 165   bool yama_is_enforcing_;  // Accurate if pre_initialized_.
 166   bool initialize_sandbox_ran_;  // InitializeSandbox() was called.
 167   scoped_ptr<sandbox::SetuidSandboxClient> setuid_sandbox_client_;
 168 #if defined(ANY_OF_AMTLU_SANITIZER)
 169   scoped_ptr<__sanitizer_sandbox_arguments> sanitizer_args_;
 170 #endif
 171
 172   DISALLOW_COPY_AND_ASSIGN(LinuxSandbox);
 173 };
 174
 175 }  // namespace content
 176
 177 #endif  // CONTENT_COMMON_SANDBOX_LINUX_SANDBOX_LINUX_H_