ipc/ipc_channel_posix.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 IPC_IPC_CHANNEL_POSIX_H_
   6 #define IPC_IPC_CHANNEL_POSIX_H_
   7
   8 #include "ipc/ipc_channel.h"
   9
  10 #include <sys/socket.h>  // for CMSG macros
  11
  12 #include <queue>
  13 #include <set>
  14 #include <string>
  15 #include <vector>
  16
  17 #include "base/files/scoped_file.h"
  18 #include "base/message_loop/message_loop.h"
  19 #include "base/process/process.h"
  20 #include "ipc/file_descriptor_set_posix.h"
  21 #include "ipc/ipc_channel_reader.h"
  22
  23 #if !defined(OS_MACOSX)
  24 // On Linux, the seccomp sandbox makes it very expensive to call
  25 // recvmsg() and sendmsg(). The restriction on calling read() and write(), which
  26 // are cheap, is that we can't pass file descriptors over them.
  27 //
  28 // As we cannot anticipate when the sender will provide us with file
  29 // descriptors, we have to make the decision about whether we call read() or
  30 // recvmsg() before we actually make the call. The easiest option is to
  31 // create a dedicated socketpair() for exchanging file descriptors. Any file
  32 // descriptors are split out of a message, with the non-file-descriptor payload
  33 // going over the normal connection, and the file descriptors being sent
  34 // separately over the other channel. When read()ing from a channel, we'll
  35 // notice if the message was supposed to have come with file descriptors and
  36 // use recvmsg on the other socketpair to retrieve them and combine them
  37 // back with the rest of the message.
  38 //
  39 // Mac can also run in IPC_USES_READWRITE mode if necessary, but at this time
  40 // doesn't take a performance hit from recvmsg and sendmsg, so it doesn't
  41 // make sense to waste resources on having the separate dedicated socketpair.
  42 // It is however useful for debugging between Linux and Mac to be able to turn
  43 // this switch 'on' on the Mac as well.
  44 //
  45 // The HELLO message from the client to the server is always sent using
  46 // sendmsg because it will contain the file descriptor that the server
  47 // needs to send file descriptors in later messages.
  48 #define IPC_USES_READWRITE 1
  49 #endif
  50
  51 namespace IPC {
  52
  53 class IPC_EXPORT ChannelPosix : public Channel,
  54                                 public internal::ChannelReader,
  55                                 public base::MessageLoopForIO::Watcher {
  56  public:
  57   ChannelPosix(const IPC::ChannelHandle& channel_handle, Mode mode,
  58                Listener* listener);
  59   virtual ~ChannelPosix();
  60
  61   // Channel implementation
  62   virtual bool Connect() OVERRIDE;
  63   virtual void Close() OVERRIDE;
  64   virtual bool Send(Message* message) OVERRIDE;
  65   virtual base::ProcessId GetPeerPID() const OVERRIDE;
  66   virtual base::ProcessId GetSelfPID() const OVERRIDE;
  67   virtual int GetClientFileDescriptor() const OVERRIDE;
  68   virtual int TakeClientFileDescriptor() OVERRIDE;
  69
  70   // Returns true if the channel supports listening for connections.
  71   bool AcceptsConnections() const;
  72
  73   // Returns true if the channel supports listening for connections and is
  74   // currently connected.
  75   bool HasAcceptedConnection() const;
  76
  77   // Closes any currently connected socket, and returns to a listening state
  78   // for more connections.
  79   void ResetToAcceptingConnectionState();
  80
  81   // Returns true if the peer process' effective user id can be determined, in
  82   // which case the supplied peer_euid is updated with it.
  83   bool GetPeerEuid(uid_t* peer_euid) const;
  84
  85   void CloseClientFileDescriptor();
  86
  87   static bool IsNamedServerInitialized(const std::string& channel_id);
  88 #if defined(OS_LINUX)
  89   static void SetGlobalPid(int pid);
  90 #endif  // OS_LINUX
  91
  92  private:
  93   bool CreatePipe(const IPC::ChannelHandle& channel_handle);
  94
  95   bool ProcessOutgoingMessages();
  96
  97   bool AcceptConnection();
  98   void ClosePipeOnError();
  99   int GetHelloMessageProcId() const;
 100   void QueueHelloMessage();
 101   void CloseFileDescriptors(Message* msg);
 102   void QueueCloseFDMessage(int fd, int hops);
 103
 104   // ChannelReader implementation.
 105   virtual ReadState ReadData(char* buffer,
 106                              int buffer_len,
 107                              int* bytes_read) OVERRIDE;
 108   virtual bool WillDispatchInputMessage(Message* msg) OVERRIDE;
 109   virtual bool DidEmptyInputBuffers() OVERRIDE;
 110   virtual void HandleInternalMessage(const Message& msg) OVERRIDE;
 111
 112 #if defined(IPC_USES_READWRITE)
 113   // Reads the next message from the fd_pipe_ and appends them to the
 114   // input_fds_ queue. Returns false if there was a message receiving error.
 115   // True means there was a message and it was processed properly, or there was
 116   // no messages.
 117   bool ReadFileDescriptorsFromFDPipe();
 118 #endif
 119
 120   // Finds the set of file descriptors in the given message.  On success,
 121   // appends the descriptors to the input_fds_ member and returns true
 122   //
 123   // Returns false if the message was truncated. In this case, any handles that
 124   // were sent will be closed.
 125   bool ExtractFileDescriptorsFromMsghdr(msghdr* msg);
 126
 127   // Closes all handles in the input_fds_ list and clears the list. This is
 128   // used to clean up handles in error conditions to avoid leaking the handles.
 129   void ClearInputFDs();
 130
 131   // MessageLoopForIO::Watcher implementation.
 132   virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE;
 133   virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE;
 134
 135   Mode mode_;
 136
 137   base::ProcessId peer_pid_;
 138
 139   // After accepting one client connection on our server socket we want to
 140   // stop listening.
 141   base::MessageLoopForIO::FileDescriptorWatcher
 142   server_listen_connection_watcher_;
 143   base::MessageLoopForIO::FileDescriptorWatcher read_watcher_;
 144   base::MessageLoopForIO::FileDescriptorWatcher write_watcher_;
 145
 146   // Indicates whether we're currently blocked waiting for a write to complete.
 147   bool is_blocked_on_write_;
 148   bool waiting_connect_;
 149
 150   // If sending a message blocks then we use this variable
 151   // to keep track of where we are.
 152   size_t message_send_bytes_written_;
 153
 154   // File descriptor we're listening on for new connections if we listen
 155   // for connections.
 156   base::ScopedFD server_listen_pipe_;
 157
 158   // The pipe used for communication.
 159   base::ScopedFD pipe_;
 160
 161   // For a server, the client end of our socketpair() -- the other end of our
 162   // pipe_ that is passed to the client.
 163   base::ScopedFD client_pipe_;
 164   mutable base::Lock client_pipe_lock_;  // Lock that protects |client_pipe_|.
 165
 166 #if defined(IPC_USES_READWRITE)
 167   // Linux/BSD use a dedicated socketpair() for passing file descriptors.
 168   base::ScopedFD fd_pipe_;
 169   base::ScopedFD remote_fd_pipe_;
 170 #endif
 171
 172   // The "name" of our pipe.  On Windows this is the global identifier for
 173   // the pipe.  On POSIX it's used as a key in a local map of file descriptors.
 174   std::string pipe_name_;
 175
 176   // Messages to be sent are queued here.
 177   std::queue<Message*> output_queue_;
 178
 179   // We assume a worst case: kReadBufferSize bytes of messages, where each
 180   // message has no payload and a full complement of descriptors.
 181   static const size_t kMaxReadFDs =
 182       (Channel::kReadBufferSize / sizeof(IPC::Message::Header)) *
 183       FileDescriptorSet::kMaxDescriptorsPerMessage;
 184
 185   // Buffer size for file descriptors used for recvmsg. On Mac the CMSG macros
 186   // don't seem to be constant so we have to pick a "large enough" value.
 187 #if defined(OS_MACOSX)
 188   static const size_t kMaxReadFDBuffer = 1024;
 189 #else
 190   static const size_t kMaxReadFDBuffer = CMSG_SPACE(sizeof(int) * kMaxReadFDs);
 191 #endif
 192
 193   // Temporary buffer used to receive the file descriptors from recvmsg.
 194   // Code that writes into this should immediately read them out and save
 195   // them to input_fds_, since this buffer will be re-used anytime we call
 196   // recvmsg.
 197   char input_cmsg_buf_[kMaxReadFDBuffer];
 198
 199   // File descriptors extracted from messages coming off of the channel. The
 200   // handles may span messages and come off different channels from the message
 201   // data (in the case of READWRITE), and are processed in FIFO here.
 202   // NOTE: The implementation assumes underlying storage here is contiguous, so
 203   // don't change to something like std::deque<> without changing the
 204   // implementation!
 205   std::vector<int> input_fds_;
 206
 207 #if defined(OS_MACOSX)
 208   // On OSX, sent FDs must not be closed until we get an ack.
 209   // Keep track of sent FDs here to make sure the remote is not
 210   // trying to bamboozle us.
 211   std::set<int> fds_to_close_;
 212 #endif
 213
 214   // True if we are responsible for unlinking the unix domain socket file.
 215   bool must_unlink_;
 216
 217 #if defined(OS_LINUX)
 218   // If non-zero, overrides the process ID sent in the hello message.
 219   static int global_pid_;
 220 #endif  // OS_LINUX
 221
 222   DISALLOW_IMPLICIT_CONSTRUCTORS(ChannelPosix);
 223 };
 224
 225 }  // namespace IPC
 226
 227 #endif  // IPC_IPC_CHANNEL_POSIX_H_