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