sandbox/mac/mach_message_server.cc

   1 // Copyright 2014 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 "sandbox/mac/mach_message_server.h"
   6
   7 #include <bsm/libbsm.h>
   8 #include <servers/bootstrap.h>
   9
  10 #include <string>
  11
  12 #include "base/logging.h"
  13 #include "base/mac/mach_logging.h"
  14 #include "base/strings/stringprintf.h"
  15
  16 namespace sandbox {
  17
  18 MachMessageServer::MachMessageServer(
  19     MessageDemuxer* demuxer,
  20     mach_port_t server_receive_right,
  21     mach_msg_size_t buffer_size)
  22     : demuxer_(demuxer),
  23       server_port_(server_receive_right),
  24       buffer_size_(
  25           mach_vm_round_page(buffer_size + sizeof(mach_msg_audit_trailer_t))),
  26       did_forward_message_(false) {
  27   DCHECK(demuxer_);
  28 }
  29
  30 MachMessageServer::~MachMessageServer() {
  31 }
  32
  33 bool MachMessageServer::Initialize() {
  34   mach_port_t task = mach_task_self();
  35   kern_return_t kr;
  36
  37   // Allocate a port for use as a new server port if one was not passed to the
  38   // constructor.
  39   if (!server_port_.is_valid()) {
  40     mach_port_t port;
  41     if ((kr = mach_port_allocate(task, MACH_PORT_RIGHT_RECEIVE, &port)) !=
  42             KERN_SUCCESS) {
  43       MACH_LOG(ERROR, kr) << "Failed to allocate new server port.";
  44       return false;
  45     }
  46     server_port_.reset(port);
  47   }
  48
  49   // Allocate the message request and reply buffers.
  50   const int kMachMsgMemoryFlags = VM_MAKE_TAG(VM_MEMORY_MACH_MSG) |
  51                                   VM_FLAGS_ANYWHERE;
  52   vm_address_t buffer = 0;
  53
  54   kr = vm_allocate(task, &buffer, buffer_size_, kMachMsgMemoryFlags);
  55   if (kr != KERN_SUCCESS) {
  56     MACH_LOG(ERROR, kr) << "Failed to allocate request buffer.";
  57     return false;
  58   }
  59   request_buffer_.reset(buffer, buffer_size_);
  60
  61   kr = vm_allocate(task, &buffer, buffer_size_, kMachMsgMemoryFlags);
  62   if (kr != KERN_SUCCESS) {
  63     MACH_LOG(ERROR, kr) << "Failed to allocate reply buffer.";
  64     return false;
  65   }
  66   reply_buffer_.reset(buffer, buffer_size_);
  67
  68   // Set up the dispatch queue to service the bootstrap port.
  69   std::string label = base::StringPrintf(
  70       "org.chromium.sandbox.MachMessageServer.%p", demuxer_);
  71   dispatch_source_.reset(new base::DispatchSourceMach(
  72       label.c_str(), server_port_.get(), ^{ ReceiveMessage(); }));
  73   dispatch_source_->Resume();
  74
  75   return true;
  76 }
  77
  78 pid_t MachMessageServer::GetMessageSenderPID(IPCMessage request) {
  79   // Get the PID of the task that sent this request. This requires getting at
  80   // the trailer of the message, from the header.
  81   mach_msg_audit_trailer_t* trailer =
  82       reinterpret_cast<mach_msg_audit_trailer_t*>(
  83           reinterpret_cast<vm_address_t>(request.mach) +
  84               round_msg(request.mach->msgh_size));
  85   // TODO(rsesek): In the 10.7 SDK, there's audit_token_to_pid().
  86   pid_t sender_pid;
  87   audit_token_to_au32(trailer->msgh_audit,
  88       NULL, NULL, NULL, NULL, NULL, &sender_pid, NULL, NULL);
  89   return sender_pid;
  90 }
  91
  92 IPCMessage MachMessageServer::CreateReply(IPCMessage request_message) {
  93   mach_msg_header_t* request = request_message.mach;
  94
  95   IPCMessage reply_message;
  96   mach_msg_header_t* reply = reply_message.mach =
  97       reinterpret_cast<mach_msg_header_t*>(reply_buffer_.address());
  98   bzero(reply, buffer_size_);
  99
 100   reply->msgh_bits = MACH_MSGH_BITS_REMOTE(reply->msgh_bits);
 101   // Since mach_msg will automatically swap the request and reply ports,
 102   // undo that.
 103   reply->msgh_remote_port = request->msgh_remote_port;
 104   reply->msgh_local_port = MACH_PORT_NULL;
 105   // MIG servers simply add 100 to the request ID to generate the reply ID.
 106   reply->msgh_id = request->msgh_id + 100;
 107
 108   return reply_message;
 109 }
 110
 111 bool MachMessageServer::SendReply(IPCMessage reply) {
 112   kern_return_t kr = mach_msg(reply.mach, MACH_SEND_MSG,
 113       reply.mach->msgh_size, 0, MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE,
 114       MACH_PORT_NULL);
 115   MACH_LOG_IF(ERROR, kr != KERN_SUCCESS, kr)
 116       << "Unable to send intercepted reply message.";
 117   return kr == KERN_SUCCESS;
 118 }
 119
 120 void MachMessageServer::ForwardMessage(IPCMessage message,
 121                                        mach_port_t destination) {
 122   mach_msg_header_t* request = message.mach;
 123   request->msgh_local_port = request->msgh_remote_port;
 124   request->msgh_remote_port = destination;
 125   // Preserve the msgh_bits that do not deal with the local and remote ports.
 126   request->msgh_bits = (request->msgh_bits & ~MACH_MSGH_BITS_PORTS_MASK) |
 127       MACH_MSGH_BITS(MACH_MSG_TYPE_COPY_SEND, MACH_MSG_TYPE_MOVE_SEND_ONCE);
 128   kern_return_t kr = mach_msg_send(request);
 129   if (kr == KERN_SUCCESS) {
 130     did_forward_message_ = true;
 131   } else {
 132     MACH_LOG(ERROR, kr) << "Unable to forward message to the real launchd.";
 133   }
 134 }
 135
 136 void MachMessageServer::RejectMessage(IPCMessage request, int error_code) {
 137   IPCMessage reply = CreateReply(request);
 138   mig_reply_error_t* error_reply =
 139       reinterpret_cast<mig_reply_error_t*>(reply.mach);
 140   error_reply->Head.msgh_size = sizeof(mig_reply_error_t);
 141   error_reply->Head.msgh_bits =
 142       MACH_MSGH_BITS_REMOTE(MACH_MSG_TYPE_MOVE_SEND_ONCE);
 143   error_reply->NDR = NDR_record;
 144   error_reply->RetCode = error_code;
 145   SendReply(reply);
 146 }
 147
 148 mach_port_t MachMessageServer::GetServerPort() const {
 149   return server_port_.get();
 150 }
 151
 152 void MachMessageServer::ReceiveMessage() {
 153   const mach_msg_options_t kRcvOptions = MACH_RCV_MSG |
 154       MACH_RCV_TRAILER_TYPE(MACH_MSG_TRAILER_FORMAT_0) |
 155       MACH_RCV_TRAILER_ELEMENTS(MACH_RCV_TRAILER_AUDIT);
 156
 157   mach_msg_header_t* request =
 158       reinterpret_cast<mach_msg_header_t*>(request_buffer_.address());
 159   mach_msg_header_t* reply =
 160       reinterpret_cast<mach_msg_header_t*>(reply_buffer_.address());
 161
 162   // Zero out the buffers from handling any previous message.
 163   bzero(request, buffer_size_);
 164   bzero(reply, buffer_size_);
 165   did_forward_message_ = false;
 166
 167   // A Mach message server-once. The system library to run a message server
 168   // cannot be used here, because some requests are conditionally forwarded
 169   // to another server.
 170   kern_return_t kr = mach_msg(request, kRcvOptions, 0, buffer_size_,
 171       server_port_.get(), MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
 172   if (kr != KERN_SUCCESS) {
 173     MACH_LOG(ERROR, kr) << "Unable to receive message.";
 174     return;
 175   }
 176
 177   // Process the message.
 178   IPCMessage request_message = { request };
 179   demuxer_->DemuxMessage(request_message);
 180
 181   // Free any descriptors in the message body. If the message was forwarded,
 182   // any descriptors would have been moved out of the process on send. If the
 183   // forwarded message was sent from the process hosting this sandbox server,
 184   // destroying the message could also destroy rights held outside the scope of
 185   // this message server.
 186   if (!did_forward_message_) {
 187     mach_msg_destroy(request);
 188     mach_msg_destroy(reply);
 189   }
 190 }
 191
 192 }  // namespace sandbox