base/posix/unix_domain_socket_linux.cc

   1 // Copyright (c) 2011 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 "base/posix/unix_domain_socket_linux.h"
   6
   7 #include <errno.h>
   8 #include <sys/socket.h>
   9 #include <unistd.h>
  10
  11 #include <vector>
  12
  13 #include "base/files/scoped_file.h"
  14 #include "base/logging.h"
  15 #include "base/memory/scoped_vector.h"
  16 #include "base/pickle.h"
  17 #include "base/posix/eintr_wrapper.h"
  18 #include "base/stl_util.h"
  19
  20 #if !defined(OS_NACL_NONSFI)
  21 #include <sys/uio.h>
  22 #endif
  23
  24 const size_t UnixDomainSocket::kMaxFileDescriptors = 16;
  25
  26 #if !defined(OS_NACL_NONSFI)
  27 // Creates a connected pair of UNIX-domain SOCK_SEQPACKET sockets, and passes
  28 // ownership of the newly allocated file descriptors to |one| and |two|.
  29 // Returns true on success.
  30 static bool CreateSocketPair(base::ScopedFD* one, base::ScopedFD* two) {
  31   int raw_socks[2];
  32   if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, raw_socks) == -1)
  33     return false;
  34   one->reset(raw_socks[0]);
  35   two->reset(raw_socks[1]);
  36   return true;
  37 }
  38
  39 // static
  40 bool UnixDomainSocket::EnableReceiveProcessId(int fd) {
  41   const int enable = 1;
  42   return setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &enable, sizeof(enable)) == 0;
  43 }
  44 #endif  // !defined(OS_NACL_NONSFI)
  45
  46 // static
  47 bool UnixDomainSocket::SendMsg(int fd,
  48                                const void* buf,
  49                                size_t length,
  50                                const std::vector<int>& fds) {
  51   struct msghdr msg = {};
  52   struct iovec iov = { const_cast<void*>(buf), length };
  53   msg.msg_iov = &iov;
  54   msg.msg_iovlen = 1;
  55
  56   char* control_buffer = NULL;
  57   if (fds.size()) {
  58     const unsigned control_len = CMSG_SPACE(sizeof(int) * fds.size());
  59     control_buffer = new char[control_len];
  60
  61     struct cmsghdr* cmsg;
  62     msg.msg_control = control_buffer;
  63     msg.msg_controllen = control_len;
  64     cmsg = CMSG_FIRSTHDR(&msg);
  65     cmsg->cmsg_level = SOL_SOCKET;
  66     cmsg->cmsg_type = SCM_RIGHTS;
  67     cmsg->cmsg_len = CMSG_LEN(sizeof(int) * fds.size());
  68     memcpy(CMSG_DATA(cmsg), &fds[0], sizeof(int) * fds.size());
  69     msg.msg_controllen = cmsg->cmsg_len;
  70   }
  71
  72   // Avoid a SIGPIPE if the other end breaks the connection.
  73   // Due to a bug in the Linux kernel (net/unix/af_unix.c) MSG_NOSIGNAL isn't
  74   // regarded for SOCK_SEQPACKET in the AF_UNIX domain, but it is mandated by
  75   // POSIX.
  76   const int flags = MSG_NOSIGNAL;
  77   const ssize_t r = HANDLE_EINTR(sendmsg(fd, &msg, flags));
  78   const bool ret = static_cast<ssize_t>(length) == r;
  79   delete[] control_buffer;
  80   return ret;
  81 }
  82
  83 // static
  84 ssize_t UnixDomainSocket::RecvMsg(int fd,
  85                                   void* buf,
  86                                   size_t length,
  87                                   ScopedVector<base::ScopedFD>* fds) {
  88   return UnixDomainSocket::RecvMsgWithPid(fd, buf, length, fds, NULL);
  89 }
  90
  91 // static
  92 ssize_t UnixDomainSocket::RecvMsgWithPid(int fd,
  93                                          void* buf,
  94                                          size_t length,
  95                                          ScopedVector<base::ScopedFD>* fds,
  96                                          base::ProcessId* pid) {
  97   return UnixDomainSocket::RecvMsgWithFlags(fd, buf, length, 0, fds, pid);
  98 }
  99
 100 // static
 101 ssize_t UnixDomainSocket::RecvMsgWithFlags(int fd,
 102                                            void* buf,
 103                                            size_t length,
 104                                            int flags,
 105                                            ScopedVector<base::ScopedFD>* fds,
 106                                            base::ProcessId* out_pid) {
 107   fds->clear();
 108
 109   struct msghdr msg = {};
 110   struct iovec iov = { buf, length };
 111   msg.msg_iov = &iov;
 112   msg.msg_iovlen = 1;
 113
 114   const size_t kControlBufferSize =
 115       CMSG_SPACE(sizeof(int) * kMaxFileDescriptors)
 116 #if !defined(OS_NACL_NONSFI)
 117       // The PNaCl toolchain for Non-SFI binary build does not support ucred.
 118       + CMSG_SPACE(sizeof(struct ucred))
 119 #endif
 120       ;
 121   char control_buffer[kControlBufferSize];
 122   msg.msg_control = control_buffer;
 123   msg.msg_controllen = sizeof(control_buffer);
 124
 125   const ssize_t r = HANDLE_EINTR(recvmsg(fd, &msg, flags));
 126   if (r == -1)
 127     return -1;
 128
 129   int* wire_fds = NULL;
 130   unsigned wire_fds_len = 0;
 131   base::ProcessId pid = -1;
 132
 133   if (msg.msg_controllen > 0) {
 134     struct cmsghdr* cmsg;
 135     for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 136       const unsigned payload_len = cmsg->cmsg_len - CMSG_LEN(0);
 137       if (cmsg->cmsg_level == SOL_SOCKET &&
 138           cmsg->cmsg_type == SCM_RIGHTS) {
 139         DCHECK(payload_len % sizeof(int) == 0);
 140         DCHECK(wire_fds == NULL);
 141         wire_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
 142         wire_fds_len = payload_len / sizeof(int);
 143       }
 144 #if !defined(OS_NACL_NONSFI)
 145       // The PNaCl toolchain for Non-SFI binary build does not support
 146       // SCM_CREDENTIALS.
 147       if (cmsg->cmsg_level == SOL_SOCKET &&
 148           cmsg->cmsg_type == SCM_CREDENTIALS) {
 149         DCHECK(payload_len == sizeof(struct ucred));
 150         DCHECK(pid == -1);
 151         pid = reinterpret_cast<struct ucred*>(CMSG_DATA(cmsg))->pid;
 152       }
 153 #endif
 154     }
 155   }
 156
 157   if (msg.msg_flags & MSG_TRUNC || msg.msg_flags & MSG_CTRUNC) {
 158     for (unsigned i = 0; i < wire_fds_len; ++i)
 159       close(wire_fds[i]);
 160     errno = EMSGSIZE;
 161     return -1;
 162   }
 163
 164   if (wire_fds) {
 165     for (unsigned i = 0; i < wire_fds_len; ++i)
 166       fds->push_back(new base::ScopedFD(wire_fds[i]));
 167   }
 168
 169   if (out_pid) {
 170     // |pid| will legitimately be -1 if we read EOF, so only DCHECK if we
 171     // actually received a message.  Unfortunately, Linux allows sending zero
 172     // length messages, which are indistinguishable from EOF, so this check
 173     // has false negatives.
 174     if (r > 0 || msg.msg_controllen > 0)
 175       DCHECK_GE(pid, 0);
 176
 177     *out_pid = pid;
 178   }
 179
 180   return r;
 181 }
 182
 183 #if !defined(OS_NACL_NONSFI)
 184 // static
 185 ssize_t UnixDomainSocket::SendRecvMsg(int fd,
 186                                       uint8_t* reply,
 187                                       unsigned max_reply_len,
 188                                       int* result_fd,
 189                                       const Pickle& request) {
 190   return UnixDomainSocket::SendRecvMsgWithFlags(fd, reply, max_reply_len,
 191                                                 0,  /* recvmsg_flags */
 192                                                 result_fd, request);
 193 }
 194
 195 // static
 196 ssize_t UnixDomainSocket::SendRecvMsgWithFlags(int fd,
 197                                                uint8_t* reply,
 198                                                unsigned max_reply_len,
 199                                                int recvmsg_flags,
 200                                                int* result_fd,
 201                                                const Pickle& request) {
 202   // This socketpair is only used for the IPC and is cleaned up before
 203   // returning.
 204   base::ScopedFD recv_sock, send_sock;
 205   if (!CreateSocketPair(&recv_sock, &send_sock))
 206     return -1;
 207
 208   {
 209     std::vector<int> send_fds;
 210     send_fds.push_back(send_sock.get());
 211     if (!SendMsg(fd, request.data(), request.size(), send_fds))
 212       return -1;
 213   }
 214
 215   // Close the sending end of the socket right away so that if our peer closes
 216   // it before sending a response (e.g., from exiting), RecvMsgWithFlags() will
 217   // return EOF instead of hanging.
 218   send_sock.reset();
 219
 220   ScopedVector<base::ScopedFD> recv_fds;
 221   // When porting to OSX keep in mind it doesn't support MSG_NOSIGNAL, so the
 222   // sender might get a SIGPIPE.
 223   const ssize_t reply_len = RecvMsgWithFlags(
 224       recv_sock.get(), reply, max_reply_len, recvmsg_flags, &recv_fds, NULL);
 225   recv_sock.reset();
 226   if (reply_len == -1)
 227     return -1;
 228
 229   // If we received more file descriptors than caller expected, then we treat
 230   // that as an error.
 231   if (recv_fds.size() > (result_fd != NULL ? 1 : 0)) {
 232     NOTREACHED();
 233     return -1;
 234   }
 235
 236   if (result_fd)
 237     *result_fd = recv_fds.empty() ? -1 : recv_fds[0]->release();
 238
 239   return reply_len;
 240 }
 241 #endif  // !defined(OS_NACL_NONSFI)