ipc/ipc_channel_posix.cc

   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 #include "ipc/ipc_channel_posix.h"
   6
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <stddef.h>
  10 #include <sys/types.h>
  11 #include <sys/socket.h>
  12 #include <sys/stat.h>
  13 #include <sys/un.h>
  14 #include <unistd.h>
  15
  16 #if defined(OS_OPENBSD)
  17 #include <sys/uio.h>
  18 #endif
  19
  20 #include <string>
  21 #include <map>
  22
  23 #include "base/command_line.h"
  24 #include "base/file_path.h"
  25 #include "base/file_util.h"
  26 #include "base/location.h"
  27 #include "base/logging.h"
  28 #include "base/memory/scoped_ptr.h"
  29 #include "base/memory/singleton.h"
  30 #include "base/posix/eintr_wrapper.h"
  31 #include "base/posix/global_descriptors.h"
  32 #include "base/process_util.h"
  33 #include "base/rand_util.h"
  34 #include "base/stl_util.h"
  35 #include "base/string_util.h"
  36 #include "base/synchronization/lock.h"
  37 #include "ipc/file_descriptor_set_posix.h"
  38 #include "ipc/ipc_descriptors.h"
  39 #include "ipc/ipc_listener.h"
  40 #include "ipc/ipc_logging.h"
  41 #include "ipc/ipc_message_utils.h"
  42 #include "ipc/ipc_switches.h"
  43
  44 namespace IPC {
  45
  46 // IPC channels on Windows use named pipes (CreateNamedPipe()) with
  47 // channel ids as the pipe names.  Channels on POSIX use sockets as
  48 // pipes  These don't quite line up.
  49 //
  50 // When creating a child subprocess we use a socket pair and the parent side of
  51 // the fork arranges it such that the initial control channel ends up on the
  52 // magic file descriptor kPrimaryIPCChannel in the child.  Future
  53 // connections (file descriptors) can then be passed via that
  54 // connection via sendmsg().
  55 //
  56 // A POSIX IPC channel can also be set up as a server for a bound UNIX domain
  57 // socket, and will handle multiple connect and disconnect sequences.  Currently
  58 // it is limited to one connection at a time.
  59
  60 //------------------------------------------------------------------------------
  61 namespace {
  62
  63 // The PipeMap class works around this quirk related to unit tests:
  64 //
  65 // When running as a server, we install the client socket in a
  66 // specific file descriptor number (@kPrimaryIPCChannel). However, we
  67 // also have to support the case where we are running unittests in the
  68 // same process.  (We do not support forking without execing.)
  69 //
  70 // Case 1: normal running
  71 //   The IPC server object will install a mapping in PipeMap from the
  72 //   name which it was given to the client pipe. When forking the client, the
  73 //   GetClientFileDescriptorMapping will ensure that the socket is installed in
  74 //   the magic slot (@kPrimaryIPCChannel). The client will search for the
  75 //   mapping, but it won't find any since we are in a new process. Thus the
  76 //   magic fd number is returned. Once the client connects, the server will
  77 //   close its copy of the client socket and remove the mapping.
  78 //
  79 // Case 2: unittests - client and server in the same process
  80 //   The IPC server will install a mapping as before. The client will search
  81 //   for a mapping and find out. It duplicates the file descriptor and
  82 //   connects. Once the client connects, the server will close the original
  83 //   copy of the client socket and remove the mapping. Thus, when the client
  84 //   object closes, it will close the only remaining copy of the client socket
  85 //   in the fd table and the server will see EOF on its side.
  86 //
  87 // TODO(port): a client process cannot connect to multiple IPC channels with
  88 // this scheme.
  89
  90 class PipeMap {
  91  public:
  92   static PipeMap* GetInstance() {
  93     return Singleton<PipeMap>::get();
  94   }
  95
  96   ~PipeMap() {
  97     // Shouldn't have left over pipes.
  98     DCHECK(map_.empty());
  99   }
 100
 101   // Lookup a given channel id. Return -1 if not found.
 102   int Lookup(const std::string& channel_id) {
 103     base::AutoLock locked(lock_);
 104
 105     ChannelToFDMap::const_iterator i = map_.find(channel_id);
 106     if (i == map_.end())
 107       return -1;
 108     return i->second;
 109   }
 110
 111   // Remove the mapping for the given channel id. No error is signaled if the
 112   // channel_id doesn't exist
 113   void Remove(const std::string& channel_id) {
 114     base::AutoLock locked(lock_);
 115     map_.erase(channel_id);
 116   }
 117
 118   // Insert a mapping from @channel_id to @fd. It's a fatal error to insert a
 119   // mapping if one already exists for the given channel_id
 120   void Insert(const std::string& channel_id, int fd) {
 121     base::AutoLock locked(lock_);
 122     DCHECK_NE(-1, fd);
 123
 124     ChannelToFDMap::const_iterator i = map_.find(channel_id);
 125     CHECK(i == map_.end()) << "Creating second IPC server (fd " << fd << ") "
 126                            << "for '" << channel_id << "' while first "
 127                            << "(fd " << i->second << ") still exists";
 128     map_[channel_id] = fd;
 129   }
 130
 131  private:
 132   base::Lock lock_;
 133   typedef std::map<std::string, int> ChannelToFDMap;
 134   ChannelToFDMap map_;
 135
 136   friend struct DefaultSingletonTraits<PipeMap>;
 137 };
 138
 139 //------------------------------------------------------------------------------
 140 // Verify that kMaxPipeNameLength is a decent size.
 141 COMPILE_ASSERT(sizeof(((sockaddr_un*)0)->sun_path) >= kMaxPipeNameLength,
 142                BAD_SUN_PATH_LENGTH);
 143
 144 // Creates a unix domain socket bound to the specified name that is listening
 145 // for connections.
 146 bool CreateServerUnixDomainSocket(const std::string& pipe_name,
 147                                   int* server_listen_fd) {
 148   DCHECK(server_listen_fd);
 149
 150   if (pipe_name.length() == 0 || pipe_name.length() >= kMaxPipeNameLength) {
 151     DLOG(ERROR) << "pipe_name.length() == " << pipe_name.length();
 152     return false;
 153   }
 154
 155   // Create socket.
 156   int fd = socket(AF_UNIX, SOCK_STREAM, 0);
 157   if (fd < 0) {
 158     return false;
 159   }
 160
 161   // Make socket non-blocking
 162   if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) {
 163     PLOG(ERROR) << "fcntl(O_NONBLOCK) " << pipe_name;
 164     if (HANDLE_EINTR(close(fd)) < 0)
 165       PLOG(ERROR) << "close " << pipe_name;
 166     return false;
 167   }
 168
 169   // Delete any old FS instances.
 170   unlink(pipe_name.c_str());
 171
 172   // Make sure the path we need exists.
 173   FilePath path(pipe_name);
 174   FilePath dir_path = path.DirName();
 175   if (!file_util::CreateDirectory(dir_path)) {
 176     if (HANDLE_EINTR(close(fd)) < 0)
 177       PLOG(ERROR) << "close " << pipe_name;
 178     return false;
 179   }
 180
 181   // Create unix_addr structure.
 182   struct sockaddr_un unix_addr;
 183   memset(&unix_addr, 0, sizeof(unix_addr));
 184   unix_addr.sun_family = AF_UNIX;
 185   int path_len = snprintf(unix_addr.sun_path, IPC::kMaxPipeNameLength,
 186                           "%s", pipe_name.c_str());
 187   DCHECK_EQ(static_cast<int>(pipe_name.length()), path_len);
 188   size_t unix_addr_len = offsetof(struct sockaddr_un,
 189                                        sun_path) + path_len + 1;
 190
 191   // Bind the socket.
 192   if (bind(fd, reinterpret_cast<const sockaddr*>(&unix_addr),
 193            unix_addr_len) != 0) {
 194     PLOG(ERROR) << "bind " << pipe_name;
 195     if (HANDLE_EINTR(close(fd)) < 0)
 196       PLOG(ERROR) << "close " << pipe_name;
 197     return false;
 198   }
 199
 200   // Start listening on the socket.
 201   const int listen_queue_length = 1;
 202   if (listen(fd, listen_queue_length) != 0) {
 203     PLOG(ERROR) << "listen " << pipe_name;
 204     if (HANDLE_EINTR(close(fd)) < 0)
 205       PLOG(ERROR) << "close " << pipe_name;
 206     return false;
 207   }
 208
 209   *server_listen_fd = fd;
 210   return true;
 211 }
 212
 213 // Accept a connection on a socket we are listening to.
 214 bool ServerAcceptConnection(int server_listen_fd, int* server_socket) {
 215   DCHECK(server_socket);
 216
 217   int accept_fd = HANDLE_EINTR(accept(server_listen_fd, NULL, 0));
 218   if (accept_fd < 0)
 219     return false;
 220   if (fcntl(accept_fd, F_SETFL, O_NONBLOCK) == -1) {
 221     PLOG(ERROR) << "fcntl(O_NONBLOCK) " << accept_fd;
 222     if (HANDLE_EINTR(close(accept_fd)) < 0)
 223       PLOG(ERROR) << "close " << accept_fd;
 224     return false;
 225   }
 226
 227   *server_socket = accept_fd;
 228   return true;
 229 }
 230
 231 bool CreateClientUnixDomainSocket(const std::string& pipe_name,
 232                                   int* client_socket) {
 233   DCHECK(client_socket);
 234   DCHECK_GT(pipe_name.length(), 0u);
 235   DCHECK_LT(pipe_name.length(), kMaxPipeNameLength);
 236
 237   if (pipe_name.length() == 0 || pipe_name.length() >= kMaxPipeNameLength) {
 238     return false;
 239   }
 240
 241   // Create socket.
 242   int fd = socket(AF_UNIX, SOCK_STREAM, 0);
 243   if (fd < 0) {
 244     PLOG(ERROR) << "socket " << pipe_name;
 245     return false;
 246   }
 247
 248   // Make socket non-blocking
 249   if (fcntl(fd, F_SETFL, O_NONBLOCK) == -1) {
 250     PLOG(ERROR) << "fcntl(O_NONBLOCK) " << pipe_name;
 251     if (HANDLE_EINTR(close(fd)) < 0)
 252       PLOG(ERROR) << "close " << pipe_name;
 253     return false;
 254   }
 255
 256   // Create server side of socket.
 257   struct sockaddr_un server_unix_addr;
 258   memset(&server_unix_addr, 0, sizeof(server_unix_addr));
 259   server_unix_addr.sun_family = AF_UNIX;
 260   int path_len = snprintf(server_unix_addr.sun_path, IPC::kMaxPipeNameLength,
 261                           "%s", pipe_name.c_str());
 262   DCHECK_EQ(static_cast<int>(pipe_name.length()), path_len);
 263   size_t server_unix_addr_len = offsetof(struct sockaddr_un,
 264                                          sun_path) + path_len + 1;
 265
 266   if (HANDLE_EINTR(connect(fd, reinterpret_cast<sockaddr*>(&server_unix_addr),
 267                            server_unix_addr_len)) != 0) {
 268     PLOG(ERROR) << "connect " << pipe_name;
 269     if (HANDLE_EINTR(close(fd)) < 0)
 270       PLOG(ERROR) << "close " << pipe_name;
 271     return false;
 272   }
 273
 274   *client_socket = fd;
 275   return true;
 276 }
 277
 278 bool SocketWriteErrorIsRecoverable() {
 279 #if defined(OS_MACOSX)
 280   // On OS X if sendmsg() is trying to send fds between processes and there
 281   // isn't enough room in the output buffer to send the fd structure over
 282   // atomically then EMSGSIZE is returned.
 283   //
 284   // EMSGSIZE presents a problem since the system APIs can only call us when
 285   // there's room in the socket buffer and not when there is "enough" room.
 286   //
 287   // The current behavior is to return to the event loop when EMSGSIZE is
 288   // received and hopefull service another FD.  This is however still
 289   // technically a busy wait since the event loop will call us right back until
 290   // the receiver has read enough data to allow passing the FD over atomically.
 291   return errno == EAGAIN || errno == EMSGSIZE;
 292 #else
 293   return errno == EAGAIN;
 294 #endif  // OS_MACOSX
 295 }
 296
 297 }  // namespace
 298 //------------------------------------------------------------------------------
 299
 300 #if defined(OS_LINUX)
 301 int Channel::ChannelImpl::global_pid_ = 0;
 302 #endif  // OS_LINUX
 303
 304 Channel::ChannelImpl::ChannelImpl(const IPC::ChannelHandle& channel_handle,
 305                                   Mode mode, Listener* listener)
 306     : ChannelReader(listener),
 307       mode_(mode),
 308       peer_pid_(base::kNullProcessId),
 309       is_blocked_on_write_(false),
 310       waiting_connect_(true),
 311       message_send_bytes_written_(0),
 312       server_listen_pipe_(-1),
 313       pipe_(-1),
 314       client_pipe_(-1),
 315 #if defined(IPC_USES_READWRITE)
 316       fd_pipe_(-1),
 317       remote_fd_pipe_(-1),
 318 #endif  // IPC_USES_READWRITE
 319       pipe_name_(channel_handle.name),
 320       must_unlink_(false) {
 321   memset(input_cmsg_buf_, 0, sizeof(input_cmsg_buf_));
 322   if (!CreatePipe(channel_handle)) {
 323     // The pipe may have been closed already.
 324     const char *modestr = (mode_ & MODE_SERVER_FLAG) ? "server" : "client";
 325     LOG(WARNING) << "Unable to create pipe named \"" << channel_handle.name
 326                  << "\" in " << modestr << " mode";
 327   }
 328 }
 329
 330 Channel::ChannelImpl::~ChannelImpl() {
 331   Close();
 332 }
 333
 334 bool SocketPair(int* fd1, int* fd2) {
 335   int pipe_fds[2];
 336   if (socketpair(AF_UNIX, SOCK_STREAM, 0, pipe_fds) != 0) {
 337     PLOG(ERROR) << "socketpair()";
 338     return false;
 339   }
 340
 341   // Set both ends to be non-blocking.
 342   if (fcntl(pipe_fds[0], F_SETFL, O_NONBLOCK) == -1 ||
 343       fcntl(pipe_fds[1], F_SETFL, O_NONBLOCK) == -1) {
 344     PLOG(ERROR) << "fcntl(O_NONBLOCK)";
 345     if (HANDLE_EINTR(close(pipe_fds[0])) < 0)
 346       PLOG(ERROR) << "close";
 347     if (HANDLE_EINTR(close(pipe_fds[1])) < 0)
 348       PLOG(ERROR) << "close";
 349     return false;
 350   }
 351
 352   *fd1 = pipe_fds[0];
 353   *fd2 = pipe_fds[1];
 354
 355   return true;
 356 }
 357
 358 bool Channel::ChannelImpl::CreatePipe(
 359     const IPC::ChannelHandle& channel_handle) {
 360   DCHECK(server_listen_pipe_ == -1 && pipe_ == -1);
 361
 362   // Four possible cases:
 363   // 1) It's a channel wrapping a pipe that is given to us.
 364   // 2) It's for a named channel, so we create it.
 365   // 3) It's for a client that we implement ourself. This is used
 366   //    in unittesting.
 367   // 4) It's the initial IPC channel:
 368   //   4a) Client side: Pull the pipe out of the GlobalDescriptors set.
 369   //   4b) Server side: create the pipe.
 370
 371   int local_pipe = -1;
 372   if (channel_handle.socket.fd != -1) {
 373     // Case 1 from comment above.
 374     local_pipe = channel_handle.socket.fd;
 375 #if defined(IPC_USES_READWRITE)
 376     // Test the socket passed into us to make sure it is nonblocking.
 377     // We don't want to call read/write on a blocking socket.
 378     int value = fcntl(local_pipe, F_GETFL);
 379     if (value == -1) {
 380       PLOG(ERROR) << "fcntl(F_GETFL) " << pipe_name_;
 381       return false;
 382     }
 383     if (!(value & O_NONBLOCK)) {
 384       LOG(ERROR) << "Socket " << pipe_name_ << " must be O_NONBLOCK";
 385       return false;
 386     }
 387 #endif   // IPC_USES_READWRITE
 388   } else if (mode_ & MODE_NAMED_FLAG) {
 389     // Case 2 from comment above.
 390     if (mode_ & MODE_SERVER_FLAG) {
 391       if (!CreateServerUnixDomainSocket(pipe_name_, &local_pipe)) {
 392         return false;
 393       }
 394       must_unlink_ = true;
 395     } else if (mode_ & MODE_CLIENT_FLAG) {
 396       if (!CreateClientUnixDomainSocket(pipe_name_, &local_pipe)) {
 397         return false;
 398       }
 399     } else {
 400       LOG(ERROR) << "Bad mode: " << mode_;
 401       return false;
 402     }
 403   } else {
 404     local_pipe = PipeMap::GetInstance()->Lookup(pipe_name_);
 405     if (mode_ & MODE_CLIENT_FLAG) {
 406       if (local_pipe != -1) {
 407         // Case 3 from comment above.
 408         // We only allow one connection.
 409         local_pipe = HANDLE_EINTR(dup(local_pipe));
 410         PipeMap::GetInstance()->Remove(pipe_name_);
 411       } else {
 412         // Case 4a from comment above.
 413         // Guard against inappropriate reuse of the initial IPC channel.  If
 414         // an IPC channel closes and someone attempts to reuse it by name, the
 415         // initial channel must not be recycled here.  http://crbug.com/26754.
 416         static bool used_initial_channel = false;
 417         if (used_initial_channel) {
 418           LOG(FATAL) << "Denying attempt to reuse initial IPC channel for "
 419                      << pipe_name_;
 420           return false;
 421         }
 422         used_initial_channel = true;
 423
 424         local_pipe =
 425             base::GlobalDescriptors::GetInstance()->Get(kPrimaryIPCChannel);
 426       }
 427     } else if (mode_ & MODE_SERVER_FLAG) {
 428       // Case 4b from comment above.
 429       if (local_pipe != -1) {
 430         LOG(ERROR) << "Server already exists for " << pipe_name_;
 431         return false;
 432       }
 433       base::AutoLock lock(client_pipe_lock_);
 434       if (!SocketPair(&local_pipe, &client_pipe_))
 435         return false;
 436       PipeMap::GetInstance()->Insert(pipe_name_, client_pipe_);
 437     } else {
 438       LOG(ERROR) << "Bad mode: " << mode_;
 439       return false;
 440     }
 441   }
 442
 443 #if defined(IPC_USES_READWRITE)
 444   // Create a dedicated socketpair() for exchanging file descriptors.
 445   // See comments for IPC_USES_READWRITE for details.
 446   if (mode_ & MODE_CLIENT_FLAG) {
 447     if (!SocketPair(&fd_pipe_, &remote_fd_pipe_)) {
 448       return false;
 449     }
 450   }
 451 #endif  // IPC_USES_READWRITE
 452
 453   if ((mode_ & MODE_SERVER_FLAG) && (mode_ & MODE_NAMED_FLAG)) {
 454     server_listen_pipe_ = local_pipe;
 455     local_pipe = -1;
 456   }
 457
 458   pipe_ = local_pipe;
 459   return true;
 460 }
 461
 462 bool Channel::ChannelImpl::Connect() {
 463   if (server_listen_pipe_ == -1 && pipe_ == -1) {
 464     DLOG(INFO) << "Channel creation failed: " << pipe_name_;
 465     return false;
 466   }
 467
 468   bool did_connect = true;
 469   if (server_listen_pipe_ != -1) {
 470     // Watch the pipe for connections, and turn any connections into
 471     // active sockets.
 472     MessageLoopForIO::current()->WatchFileDescriptor(
 473         server_listen_pipe_,
 474         true,
 475         MessageLoopForIO::WATCH_READ,
 476         &server_listen_connection_watcher_,
 477         this);
 478   } else {
 479     did_connect = AcceptConnection();
 480   }
 481   return did_connect;
 482 }
 483
 484 bool Channel::ChannelImpl::ProcessOutgoingMessages() {
 485   DCHECK(!waiting_connect_);  // Why are we trying to send messages if there's
 486                               // no connection?
 487   if (output_queue_.empty())
 488     return true;
 489
 490   if (pipe_ == -1)
 491     return false;
 492
 493   // Write out all the messages we can till the write blocks or there are no
 494   // more outgoing messages.
 495   while (!output_queue_.empty()) {
 496     Message* msg = output_queue_.front();
 497
 498     size_t amt_to_write = msg->size() - message_send_bytes_written_;
 499     DCHECK_NE(0U, amt_to_write);
 500     const char* out_bytes = reinterpret_cast<const char*>(msg->data()) +
 501         message_send_bytes_written_;
 502
 503     struct msghdr msgh = {0};
 504     struct iovec iov = {const_cast<char*>(out_bytes), amt_to_write};
 505     msgh.msg_iov = &iov;
 506     msgh.msg_iovlen = 1;
 507     char buf[CMSG_SPACE(
 508         sizeof(int) * FileDescriptorSet::kMaxDescriptorsPerMessage)];
 509
 510     ssize_t bytes_written = 1;
 511     int fd_written = -1;
 512
 513     if (message_send_bytes_written_ == 0 &&
 514         !msg->file_descriptor_set()->empty()) {
 515       // This is the first chunk of a message which has descriptors to send
 516       struct cmsghdr *cmsg;
 517       const unsigned num_fds = msg->file_descriptor_set()->size();
 518
 519       DCHECK(num_fds <= FileDescriptorSet::kMaxDescriptorsPerMessage);
 520       if (msg->file_descriptor_set()->ContainsDirectoryDescriptor()) {
 521         LOG(FATAL) << "Panic: attempting to transport directory descriptor over"
 522                       " IPC. Aborting to maintain sandbox isolation.";
 523         // If you have hit this then something tried to send a file descriptor
 524         // to a directory over an IPC channel. Since IPC channels span
 525         // sandboxes this is very bad: the receiving process can use openat
 526         // with ".." elements in the path in order to reach the real
 527         // filesystem.
 528       }
 529
 530       msgh.msg_control = buf;
 531       msgh.msg_controllen = CMSG_SPACE(sizeof(int) * num_fds);
 532       cmsg = CMSG_FIRSTHDR(&msgh);
 533       cmsg->cmsg_level = SOL_SOCKET;
 534       cmsg->cmsg_type = SCM_RIGHTS;
 535       cmsg->cmsg_len = CMSG_LEN(sizeof(int) * num_fds);
 536       msg->file_descriptor_set()->GetDescriptors(
 537           reinterpret_cast<int*>(CMSG_DATA(cmsg)));
 538       msgh.msg_controllen = cmsg->cmsg_len;
 539
 540       // DCHECK_LE above already checks that
 541       // num_fds < kMaxDescriptorsPerMessage so no danger of overflow.
 542       msg->header()->num_fds = static_cast<uint16>(num_fds);
 543
 544 #if defined(IPC_USES_READWRITE)
 545       if (!IsHelloMessage(*msg)) {
 546         // Only the Hello message sends the file descriptor with the message.
 547         // Subsequently, we can send file descriptors on the dedicated
 548         // fd_pipe_ which makes Seccomp sandbox operation more efficient.
 549         struct iovec fd_pipe_iov = { const_cast<char *>(""), 1 };
 550         msgh.msg_iov = &fd_pipe_iov;
 551         fd_written = fd_pipe_;
 552         bytes_written = HANDLE_EINTR(sendmsg(fd_pipe_, &msgh, MSG_DONTWAIT));
 553         msgh.msg_iov = &iov;
 554         msgh.msg_controllen = 0;
 555         if (bytes_written > 0) {
 556           msg->file_descriptor_set()->CommitAll();
 557         }
 558       }
 559 #endif  // IPC_USES_READWRITE
 560     }
 561
 562     if (bytes_written == 1) {
 563       fd_written = pipe_;
 564 #if defined(IPC_USES_READWRITE)
 565       if ((mode_ & MODE_CLIENT_FLAG) && IsHelloMessage(*msg)) {
 566         DCHECK_EQ(msg->file_descriptor_set()->size(), 1U);
 567       }
 568       if (!msgh.msg_controllen) {
 569         bytes_written = HANDLE_EINTR(write(pipe_, out_bytes, amt_to_write));
 570       } else
 571 #endif  // IPC_USES_READWRITE
 572       {
 573         bytes_written = HANDLE_EINTR(sendmsg(pipe_, &msgh, MSG_DONTWAIT));
 574       }
 575     }
 576     if (bytes_written > 0)
 577       msg->file_descriptor_set()->CommitAll();
 578
 579     if (bytes_written < 0 && !SocketWriteErrorIsRecoverable()) {
 580 #if defined(OS_MACOSX)
 581       // On OSX writing to a pipe with no listener returns EPERM.
 582       if (errno == EPERM) {
 583         Close();
 584         return false;
 585       }
 586 #endif  // OS_MACOSX
 587       if (errno == EPIPE) {
 588         Close();
 589         return false;
 590       }
 591       PLOG(ERROR) << "pipe error on "
 592                   << fd_written
 593                   << " Currently writing message of size: "
 594                   << msg->size();
 595       return false;
 596     }
 597
 598     if (static_cast<size_t>(bytes_written) != amt_to_write) {
 599       if (bytes_written > 0) {
 600         // If write() fails with EAGAIN then bytes_written will be -1.
 601         message_send_bytes_written_ += bytes_written;
 602       }
 603
 604       // Tell libevent to call us back once things are unblocked.
 605       is_blocked_on_write_ = true;
 606       MessageLoopForIO::current()->WatchFileDescriptor(
 607           pipe_,
 608           false,  // One shot
 609           MessageLoopForIO::WATCH_WRITE,
 610           &write_watcher_,
 611           this);
 612       return true;
 613     } else {
 614       message_send_bytes_written_ = 0;
 615
 616       // Message sent OK!
 617       DVLOG(2) << "sent message @" << msg << " on channel @" << this
 618                << " with type " << msg->type() << " on fd " << pipe_;
 619       delete output_queue_.front();
 620       output_queue_.pop();
 621     }
 622   }
 623   return true;
 624 }
 625
 626 bool Channel::ChannelImpl::Send(Message* message) {
 627   DVLOG(2) << "sending message @" << message << " on channel @" << this
 628            << " with type " << message->type()
 629            << " (" << output_queue_.size() << " in queue)";
 630
 631 #ifdef IPC_MESSAGE_LOG_ENABLED
 632   Logging::GetInstance()->OnSendMessage(message, "");
 633 #endif  // IPC_MESSAGE_LOG_ENABLED
 634
 635   message->TraceMessageBegin();
 636   output_queue_.push(message);
 637   if (!is_blocked_on_write_ && !waiting_connect_) {
 638     return ProcessOutgoingMessages();
 639   }
 640
 641   return true;
 642 }
 643
 644 int Channel::ChannelImpl::GetClientFileDescriptor() {
 645   base::AutoLock lock(client_pipe_lock_);
 646   return client_pipe_;
 647 }
 648
 649 int Channel::ChannelImpl::TakeClientFileDescriptor() {
 650   base::AutoLock lock(client_pipe_lock_);
 651   int fd = client_pipe_;
 652   if (client_pipe_ != -1) {
 653     PipeMap::GetInstance()->Remove(pipe_name_);
 654     client_pipe_ = -1;
 655   }
 656   return fd;
 657 }
 658
 659 void Channel::ChannelImpl::CloseClientFileDescriptor() {
 660   base::AutoLock lock(client_pipe_lock_);
 661   if (client_pipe_ != -1) {
 662     PipeMap::GetInstance()->Remove(pipe_name_);
 663     if (HANDLE_EINTR(close(client_pipe_)) < 0)
 664       PLOG(ERROR) << "close " << pipe_name_;
 665     client_pipe_ = -1;
 666   }
 667 }
 668
 669 bool Channel::ChannelImpl::AcceptsConnections() const {
 670   return server_listen_pipe_ != -1;
 671 }
 672
 673 bool Channel::ChannelImpl::HasAcceptedConnection() const {
 674   return AcceptsConnections() && pipe_ != -1;
 675 }
 676
 677 bool Channel::ChannelImpl::GetClientEuid(uid_t* client_euid) const {
 678   DCHECK(HasAcceptedConnection());
 679 #if defined(OS_MACOSX) || defined(OS_OPENBSD)
 680   uid_t peer_euid;
 681   gid_t peer_gid;
 682   if (getpeereid(pipe_, &peer_euid, &peer_gid) != 0) {
 683     PLOG(ERROR) << "getpeereid " << pipe_;
 684     return false;
 685   }
 686   *client_euid = peer_euid;
 687   return true;
 688 #elif defined(OS_SOLARIS)
 689   return false;
 690 #else
 691   struct ucred cred;
 692   socklen_t cred_len = sizeof(cred);
 693   if (getsockopt(pipe_, SOL_SOCKET, SO_PEERCRED, &cred, &cred_len) != 0) {
 694     PLOG(ERROR) << "getsockopt " << pipe_;
 695     return false;
 696   }
 697   if (static_cast<unsigned>(cred_len) < sizeof(cred)) {
 698     NOTREACHED() << "Truncated ucred from SO_PEERCRED?";
 699     return false;
 700   }
 701   *client_euid = cred.uid;
 702   return true;
 703 #endif
 704 }
 705
 706 void Channel::ChannelImpl::ResetToAcceptingConnectionState() {
 707   // Unregister libevent for the unix domain socket and close it.
 708   read_watcher_.StopWatchingFileDescriptor();
 709   write_watcher_.StopWatchingFileDescriptor();
 710   if (pipe_ != -1) {
 711     if (HANDLE_EINTR(close(pipe_)) < 0)
 712       PLOG(ERROR) << "close pipe_ " << pipe_name_;
 713     pipe_ = -1;
 714   }
 715 #if defined(IPC_USES_READWRITE)
 716   if (fd_pipe_ != -1) {
 717     if (HANDLE_EINTR(close(fd_pipe_)) < 0)
 718       PLOG(ERROR) << "close fd_pipe_ " << pipe_name_;
 719     fd_pipe_ = -1;
 720   }
 721   if (remote_fd_pipe_ != -1) {
 722     if (HANDLE_EINTR(close(remote_fd_pipe_)) < 0)
 723       PLOG(ERROR) << "close remote_fd_pipe_ " << pipe_name_;
 724     remote_fd_pipe_ = -1;
 725   }
 726 #endif  // IPC_USES_READWRITE
 727
 728   while (!output_queue_.empty()) {
 729     Message* m = output_queue_.front();
 730     output_queue_.pop();
 731     delete m;
 732   }
 733
 734   // Close any outstanding, received file descriptors.
 735   ClearInputFDs();
 736 }
 737
 738 // static
 739 bool Channel::ChannelImpl::IsNamedServerInitialized(
 740     const std::string& channel_id) {
 741   return file_util::PathExists(FilePath(channel_id));
 742 }
 743
 744 #if defined(OS_LINUX)
 745 // static
 746 void Channel::ChannelImpl::SetGlobalPid(int pid) {
 747   global_pid_ = pid;
 748 }
 749 #endif  // OS_LINUX
 750
 751 // Called by libevent when we can read from the pipe without blocking.
 752 void Channel::ChannelImpl::OnFileCanReadWithoutBlocking(int fd) {
 753   bool send_server_hello_msg = false;
 754   if (fd == server_listen_pipe_) {
 755     int new_pipe = 0;
 756     if (!ServerAcceptConnection(server_listen_pipe_, &new_pipe)) {
 757       Close();
 758       listener()->OnChannelListenError();
 759     }
 760
 761     if (pipe_ != -1) {
 762       // We already have a connection. We only handle one at a time.
 763       // close our new descriptor.
 764       if (HANDLE_EINTR(shutdown(new_pipe, SHUT_RDWR)) < 0)
 765         DPLOG(ERROR) << "shutdown " << pipe_name_;
 766       if (HANDLE_EINTR(close(new_pipe)) < 0)
 767         DPLOG(ERROR) << "close " << pipe_name_;
 768       listener()->OnChannelDenied();
 769       return;
 770     }
 771     pipe_ = new_pipe;
 772
 773     if ((mode_ & MODE_OPEN_ACCESS_FLAG) == 0) {
 774       // Verify that the IPC channel peer is running as the same user.
 775       uid_t client_euid;
 776       if (!GetClientEuid(&client_euid)) {
 777         DLOG(ERROR) << "Unable to query client euid";
 778         ResetToAcceptingConnectionState();
 779         return;
 780       }
 781       if (client_euid != geteuid()) {
 782         DLOG(WARNING) << "Client euid is not authorised";
 783         ResetToAcceptingConnectionState();
 784         return;
 785       }
 786     }
 787
 788     if (!AcceptConnection()) {
 789       NOTREACHED() << "AcceptConnection should not fail on server";
 790     }
 791     send_server_hello_msg = true;
 792     waiting_connect_ = false;
 793   } else if (fd == pipe_) {
 794     if (waiting_connect_ && (mode_ & MODE_SERVER_FLAG)) {
 795       send_server_hello_msg = true;
 796       waiting_connect_ = false;
 797     }
 798     if (!ProcessIncomingMessages()) {
 799       // ClosePipeOnError may delete this object, so we mustn't call
 800       // ProcessOutgoingMessages.
 801       send_server_hello_msg = false;
 802       ClosePipeOnError();
 803     }
 804   } else {
 805     NOTREACHED() << "Unknown pipe " << fd;
 806   }
 807
 808   // If we're a server and handshaking, then we want to make sure that we
 809   // only send our handshake message after we've processed the client's.
 810   // This gives us a chance to kill the client if the incoming handshake
 811   // is invalid.
 812   if (send_server_hello_msg) {
 813     ProcessOutgoingMessages();
 814   }
 815 }
 816
 817 // Called by libevent when we can write to the pipe without blocking.
 818 void Channel::ChannelImpl::OnFileCanWriteWithoutBlocking(int fd) {
 819   DCHECK_EQ(pipe_, fd);
 820   is_blocked_on_write_ = false;
 821   if (!ProcessOutgoingMessages()) {
 822     ClosePipeOnError();
 823   }
 824 }
 825
 826 bool Channel::ChannelImpl::AcceptConnection() {
 827   MessageLoopForIO::current()->WatchFileDescriptor(pipe_,
 828                                                    true,
 829                                                    MessageLoopForIO::WATCH_READ,
 830                                                    &read_watcher_,
 831                                                    this);
 832   QueueHelloMessage();
 833
 834   if (mode_ & MODE_CLIENT_FLAG) {
 835     // If we are a client we want to send a hello message out immediately.
 836     // In server mode we will send a hello message when we receive one from a
 837     // client.
 838     waiting_connect_ = false;
 839     return ProcessOutgoingMessages();
 840   } else if (mode_ & MODE_SERVER_FLAG) {
 841     waiting_connect_ = true;
 842     return true;
 843   } else {
 844     NOTREACHED();
 845     return false;
 846   }
 847 }
 848
 849 void Channel::ChannelImpl::ClosePipeOnError() {
 850   if (HasAcceptedConnection()) {
 851     ResetToAcceptingConnectionState();
 852     listener()->OnChannelError();
 853   } else {
 854     Close();
 855     if (AcceptsConnections()) {
 856       listener()->OnChannelListenError();
 857     } else {
 858       listener()->OnChannelError();
 859     }
 860   }
 861 }
 862
 863 int Channel::ChannelImpl::GetHelloMessageProcId() {
 864   int pid = base::GetCurrentProcId();
 865 #if defined(OS_LINUX)
 866   // Our process may be in a sandbox with a separate PID namespace.
 867   if (global_pid_) {
 868     pid = global_pid_;
 869   }
 870 #endif
 871   return pid;
 872 }
 873
 874 void Channel::ChannelImpl::QueueHelloMessage() {
 875   // Create the Hello message
 876   scoped_ptr<Message> msg(new Message(MSG_ROUTING_NONE,
 877                                       HELLO_MESSAGE_TYPE,
 878                                       IPC::Message::PRIORITY_NORMAL));
 879   if (!msg->WriteInt(GetHelloMessageProcId())) {
 880     NOTREACHED() << "Unable to pickle hello message proc id";
 881   }
 882 #if defined(IPC_USES_READWRITE)
 883   scoped_ptr<Message> hello;
 884   if (remote_fd_pipe_ != -1) {
 885     if (!msg->WriteFileDescriptor(base::FileDescriptor(remote_fd_pipe_,
 886                                                        false))) {
 887       NOTREACHED() << "Unable to pickle hello message file descriptors";
 888     }
 889     DCHECK_EQ(msg->file_descriptor_set()->size(), 1U);
 890   }
 891 #endif  // IPC_USES_READWRITE
 892   output_queue_.push(msg.release());
 893 }
 894
 895 Channel::ChannelImpl::ReadState Channel::ChannelImpl::ReadData(
 896     char* buffer,
 897     int buffer_len,
 898     int* bytes_read) {
 899   if (pipe_ == -1)
 900     return READ_FAILED;
 901
 902   struct msghdr msg = {0};
 903
 904   struct iovec iov = {buffer, static_cast<size_t>(buffer_len)};
 905   msg.msg_iov = &iov;
 906   msg.msg_iovlen = 1;
 907
 908   msg.msg_control = input_cmsg_buf_;
 909
 910   // recvmsg() returns 0 if the connection has closed or EAGAIN if no data
 911   // is waiting on the pipe.
 912 #if defined(IPC_USES_READWRITE)
 913   if (fd_pipe_ >= 0) {
 914     *bytes_read = HANDLE_EINTR(read(pipe_, buffer, buffer_len));
 915     msg.msg_controllen = 0;
 916   } else
 917 #endif  // IPC_USES_READWRITE
 918   {
 919     msg.msg_controllen = sizeof(input_cmsg_buf_);
 920     *bytes_read = HANDLE_EINTR(recvmsg(pipe_, &msg, MSG_DONTWAIT));
 921   }
 922   if (*bytes_read < 0) {
 923     if (errno == EAGAIN) {
 924       return READ_PENDING;
 925 #if defined(OS_MACOSX)
 926     } else if (errno == EPERM) {
 927       // On OSX, reading from a pipe with no listener returns EPERM
 928       // treat this as a special case to prevent spurious error messages
 929       // to the console.
 930       return READ_FAILED;
 931 #endif  // OS_MACOSX
 932     } else if (errno == ECONNRESET || errno == EPIPE) {
 933       return READ_FAILED;
 934     } else {
 935       PLOG(ERROR) << "pipe error (" << pipe_ << ")";
 936       return READ_FAILED;
 937     }
 938   } else if (*bytes_read == 0) {
 939     // The pipe has closed...
 940     return READ_FAILED;
 941   }
 942   DCHECK(*bytes_read);
 943
 944   CloseClientFileDescriptor();
 945
 946   // Read any file descriptors from the message.
 947   if (!ExtractFileDescriptorsFromMsghdr(&msg))
 948     return READ_FAILED;
 949   return READ_SUCCEEDED;
 950 }
 951
 952 #if defined(IPC_USES_READWRITE)
 953 bool Channel::ChannelImpl::ReadFileDescriptorsFromFDPipe() {
 954   char dummy;
 955   struct iovec fd_pipe_iov = { &dummy, 1 };
 956
 957   struct msghdr msg = { 0 };
 958   msg.msg_iov = &fd_pipe_iov;
 959   msg.msg_iovlen = 1;
 960   msg.msg_control = input_cmsg_buf_;
 961   msg.msg_controllen = sizeof(input_cmsg_buf_);
 962   ssize_t bytes_received = HANDLE_EINTR(recvmsg(fd_pipe_, &msg, MSG_DONTWAIT));
 963
 964   if (bytes_received != 1)
 965     return true;  // No message waiting.
 966
 967   if (!ExtractFileDescriptorsFromMsghdr(&msg))
 968     return false;
 969   return true;
 970 }
 971 #endif
 972
 973 // On Posix, we need to fix up the file descriptors before the input message
 974 // is dispatched.
 975 //
 976 // This will read from the input_fds_ (READWRITE mode only) and read more
 977 // handles from the FD pipe if necessary.
 978 bool Channel::ChannelImpl::WillDispatchInputMessage(Message* msg) {
 979   uint16 header_fds = msg->header()->num_fds;
 980   if (!header_fds)
 981     return true;  // Nothing to do.
 982
 983   // The message has file descriptors.
 984   const char* error = NULL;
 985   if (header_fds > input_fds_.size()) {
 986     // The message has been completely received, but we didn't get
 987     // enough file descriptors.
 988 #if defined(IPC_USES_READWRITE)
 989     if (!ReadFileDescriptorsFromFDPipe())
 990       return false;
 991     if (header_fds > input_fds_.size())
 992 #endif  // IPC_USES_READWRITE
 993       error = "Message needs unreceived descriptors";
 994   }
 995
 996   if (header_fds > FileDescriptorSet::kMaxDescriptorsPerMessage)
 997     error = "Message requires an excessive number of descriptors";
 998
 999   if (error) {
1000     LOG(WARNING) << error
1001                  << " channel:" << this
1002                  << " message-type:" << msg->type()
1003                  << " header()->num_fds:" << header_fds;
1004 #if defined(CHROMIUM_SELINUX)
1005     LOG(WARNING) << "In the case of SELinux this can be caused when "
1006                     "using a --user-data-dir to which the default "
1007                     "policy doesn't give the renderer access to. ";
1008 #endif  // CHROMIUM_SELINUX
1009     // Abort the connection.
1010     ClearInputFDs();
1011     return false;
1012   }
1013
1014   // The shenaniganery below with &foo.front() requires input_fds_ to have
1015   // contiguous underlying storage (such as a simple array or a std::vector).
1016   // This is why the header warns not to make input_fds_ a deque<>.
1017   msg->file_descriptor_set()->SetDescriptors(&input_fds_.front(),
1018                                              header_fds);
1019   input_fds_.erase(input_fds_.begin(), input_fds_.begin() + header_fds);
1020   return true;
1021 }
1022
1023 bool Channel::ChannelImpl::DidEmptyInputBuffers() {
1024   // When the input data buffer is empty, the fds should be too. If this is
1025   // not the case, we probably have a rogue renderer which is trying to fill
1026   // our descriptor table.
1027   return input_fds_.empty();
1028 }
1029
1030 bool Channel::ChannelImpl::ExtractFileDescriptorsFromMsghdr(msghdr* msg) {
1031   // Check that there are any control messages. On OSX, CMSG_FIRSTHDR will
1032   // return an invalid non-NULL pointer in the case that controllen == 0.
1033   if (msg->msg_controllen == 0)
1034     return true;
1035
1036   for (cmsghdr* cmsg = CMSG_FIRSTHDR(msg);
1037        cmsg;
1038        cmsg = CMSG_NXTHDR(msg, cmsg)) {
1039     if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
1040       unsigned payload_len = cmsg->cmsg_len - CMSG_LEN(0);
1041       DCHECK_EQ(0U, payload_len % sizeof(int));
1042       const int* file_descriptors = reinterpret_cast<int*>(CMSG_DATA(cmsg));
1043       unsigned num_file_descriptors = payload_len / 4;
1044       input_fds_.insert(input_fds_.end(),
1045                         file_descriptors,
1046                         file_descriptors + num_file_descriptors);
1047
1048       // Check this after adding the FDs so we don't leak them.
1049       if (msg->msg_flags & MSG_CTRUNC) {
1050         ClearInputFDs();
1051         return false;
1052       }
1053
1054       return true;
1055     }
1056   }
1057
1058   // No file descriptors found, but that's OK.
1059   return true;
1060 }
1061
1062 void Channel::ChannelImpl::ClearInputFDs() {
1063   for (size_t i = 0; i < input_fds_.size(); ++i) {
1064     if (HANDLE_EINTR(close(input_fds_[i])) < 0)
1065       PLOG(ERROR) << "close ";
1066   }
1067   input_fds_.clear();
1068 }
1069
1070 void Channel::ChannelImpl::HandleHelloMessage(const Message& msg) {
1071   // The Hello message contains only the process id.
1072   PickleIterator iter(msg);
1073   int pid;
1074   if (!msg.ReadInt(&iter, &pid))
1075     NOTREACHED();
1076
1077 #if defined(IPC_USES_READWRITE)
1078   if (mode_ & MODE_SERVER_FLAG) {
1079     // With IPC_USES_READWRITE, the Hello message from the client to the
1080     // server also contains the fd_pipe_, which  will be used for all
1081     // subsequent file descriptor passing.
1082     DCHECK_EQ(msg.file_descriptor_set()->size(), 1U);
1083     base::FileDescriptor descriptor;
1084     if (!msg.ReadFileDescriptor(&iter, &descriptor)) {
1085       NOTREACHED();
1086     }
1087     fd_pipe_ = descriptor.fd;
1088     CHECK(descriptor.auto_close);
1089   }
1090 #endif  // IPC_USES_READWRITE
1091   peer_pid_ = pid;
1092   listener()->OnChannelConnected(pid);
1093 }
1094
1095 void Channel::ChannelImpl::Close() {
1096   // Close can be called multiple time, so we need to make sure we're
1097   // idempotent.
1098
1099   ResetToAcceptingConnectionState();
1100
1101   if (must_unlink_) {
1102     unlink(pipe_name_.c_str());
1103     must_unlink_ = false;
1104   }
1105   if (server_listen_pipe_ != -1) {
1106     if (HANDLE_EINTR(close(server_listen_pipe_)) < 0)
1107       DPLOG(ERROR) << "close " << server_listen_pipe_;
1108     server_listen_pipe_ = -1;
1109     // Unregister libevent for the listening socket and close it.
1110     server_listen_connection_watcher_.StopWatchingFileDescriptor();
1111   }
1112
1113   CloseClientFileDescriptor();
1114 }
1115
1116 //------------------------------------------------------------------------------
1117 // Channel's methods simply call through to ChannelImpl.
1118 Channel::Channel(const IPC::ChannelHandle& channel_handle, Mode mode,
1119                  Listener* listener)
1120     : channel_impl_(new ChannelImpl(channel_handle, mode, listener)) {
1121 }
1122
1123 Channel::~Channel() {
1124   delete channel_impl_;
1125 }
1126
1127 bool Channel::Connect() {
1128   return channel_impl_->Connect();
1129 }
1130
1131 void Channel::Close() {
1132   if (channel_impl_)
1133     channel_impl_->Close();
1134 }
1135
1136 void Channel::set_listener(Listener* listener) {
1137   channel_impl_->set_listener(listener);
1138 }
1139
1140 base::ProcessId Channel::peer_pid() const {
1141   return channel_impl_->peer_pid();
1142 }
1143
1144 bool Channel::Send(Message* message) {
1145   return channel_impl_->Send(message);
1146 }
1147
1148 int Channel::GetClientFileDescriptor() const {
1149   return channel_impl_->GetClientFileDescriptor();
1150 }
1151
1152 int Channel::TakeClientFileDescriptor() {
1153   return channel_impl_->TakeClientFileDescriptor();
1154 }
1155
1156 bool Channel::AcceptsConnections() const {
1157   return channel_impl_->AcceptsConnections();
1158 }
1159
1160 bool Channel::HasAcceptedConnection() const {
1161   return channel_impl_->HasAcceptedConnection();
1162 }
1163
1164 bool Channel::GetClientEuid(uid_t* client_euid) const {
1165   return channel_impl_->GetClientEuid(client_euid);
1166 }
1167
1168 void Channel::ResetToAcceptingConnectionState() {
1169   channel_impl_->ResetToAcceptingConnectionState();
1170 }
1171
1172 // static
1173 bool Channel::IsNamedServerInitialized(const std::string& channel_id) {
1174   return ChannelImpl::IsNamedServerInitialized(channel_id);
1175 }
1176
1177 // static
1178 std::string Channel::GenerateVerifiedChannelID(const std::string& prefix) {
1179   // A random name is sufficient validation on posix systems, so we don't need
1180   // an additional shared secret.
1181
1182   std::string id = prefix;
1183   if (!id.empty())
1184     id.append(".");
1185
1186   return id.append(GenerateUniqueRandomChannelID());
1187 }
1188
1189
1190 #if defined(OS_LINUX)
1191 // static
1192 void Channel::SetGlobalPid(int pid) {
1193   ChannelImpl::SetGlobalPid(pid);
1194 }
1195 #endif  // OS_LINUX
1196
1197 }  // namespace IPC