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