components/nacl/browser/nacl_file_host.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 "components/nacl/browser/nacl_file_host.h"
   6
   7 #include "base/bind.h"
   8 #include "base/file_util.h"
   9 #include "base/files/file.h"
  10 #include "base/files/file_path.h"
  11 #include "base/path_service.h"
  12 #include "base/strings/utf_string_conversions.h"
  13 #include "base/threading/sequenced_worker_pool.h"
  14 #include "components/nacl/browser/nacl_browser.h"
  15 #include "components/nacl/browser/nacl_browser_delegate.h"
  16 #include "components/nacl/browser/nacl_host_message_filter.h"
  17 #include "components/nacl/common/nacl_host_messages.h"
  18 #include "content/public/browser/browser_thread.h"
  19 #include "content/public/browser/render_view_host.h"
  20 #include "content/public/browser/site_instance.h"
  21 #include "ipc/ipc_platform_file.h"
  22
  23 using content::BrowserThread;
  24
  25 namespace {
  26
  27 // Force a prefix to prevent user from opening "magic" files.
  28 const char* kExpectedFilePrefix = "pnacl_public_";
  29
  30 // Restrict PNaCl file lengths to reduce likelyhood of hitting bugs
  31 // in file name limit error-handling-code-paths, etc.
  32 const size_t kMaxFileLength = 40;
  33
  34 void NotifyRendererOfError(
  35     nacl::NaClHostMessageFilter* nacl_host_message_filter,
  36     IPC::Message* reply_msg) {
  37   reply_msg->set_reply_error();
  38   nacl_host_message_filter->Send(reply_msg);
  39 }
  40
  41 typedef void (*WriteFileInfoReply)(IPC::Message* reply_msg,
  42                                    IPC::PlatformFileForTransit file_desc,
  43                                    uint64 file_token_lo,
  44                                    uint64 file_token_hi);
  45
  46 void DoRegisterOpenedNaClExecutableFile(
  47     scoped_refptr<nacl::NaClHostMessageFilter> nacl_host_message_filter,
  48     base::File file,
  49     base::FilePath file_path,
  50     IPC::Message* reply_msg,
  51     WriteFileInfoReply write_reply_message) {
  52   // IO thread owns the NaClBrowser singleton.
  53   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
  54
  55   nacl::NaClBrowser* nacl_browser = nacl::NaClBrowser::GetInstance();
  56   uint64 file_token_lo = 0;
  57   uint64 file_token_hi = 0;
  58   nacl_browser->PutFilePath(file_path, &file_token_lo, &file_token_hi);
  59
  60   IPC::PlatformFileForTransit file_desc = IPC::TakeFileHandleForProcess(
  61       file.Pass(),
  62       nacl_host_message_filter->PeerHandle());
  63
  64   write_reply_message(reply_msg, file_desc, file_token_lo, file_token_hi);
  65   nacl_host_message_filter->Send(reply_msg);
  66 }
  67
  68 void DoOpenPnaclFile(
  69     scoped_refptr<nacl::NaClHostMessageFilter> nacl_host_message_filter,
  70     const std::string& filename,
  71     bool is_executable,
  72     IPC::Message* reply_msg) {
  73   DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
  74   base::FilePath full_filepath;
  75
  76   // PNaCl must be installed.
  77   base::FilePath pnacl_dir;
  78   if (!nacl::NaClBrowser::GetDelegate()->GetPnaclDirectory(&pnacl_dir) ||
  79       !base::PathExists(pnacl_dir)) {
  80     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  81     return;
  82   }
  83
  84   // Do some validation.
  85   if (!nacl_file_host::PnaclCanOpenFile(filename, &full_filepath)) {
  86     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  87     return;
  88   }
  89
  90   base::File file_to_open = nacl::OpenNaClReadExecImpl(full_filepath,
  91                                                        is_executable);
  92   if (!file_to_open.IsValid()) {
  93     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  94     return;
  95   }
  96
  97   // This function is running on the blocking pool, but the path needs to be
  98   // registered in a structure owned by the IO thread.
  99   // Not all PNaCl files are executable. Only register those that are
 100   // executable in the NaCl file_path cache.
 101   if (is_executable) {
 102     BrowserThread::PostTask(
 103         BrowserThread::IO, FROM_HERE,
 104         base::Bind(&DoRegisterOpenedNaClExecutableFile,
 105                    nacl_host_message_filter,
 106                    Passed(file_to_open.Pass()), full_filepath, reply_msg,
 107                    static_cast<WriteFileInfoReply>(
 108                        NaClHostMsg_GetReadonlyPnaclFD::WriteReplyParams)));
 109   } else {
 110     IPC::PlatformFileForTransit target_desc =
 111         IPC::TakeFileHandleForProcess(file_to_open.Pass(),
 112                                       nacl_host_message_filter->PeerHandle());
 113     uint64_t dummy_file_token = 0;
 114     NaClHostMsg_GetReadonlyPnaclFD::WriteReplyParams(
 115         reply_msg, target_desc, dummy_file_token, dummy_file_token);
 116     nacl_host_message_filter->Send(reply_msg);
 117   }
 118 }
 119
 120 // Convert the file URL into a file descriptor.
 121 // This function is security sensitive.  Be sure to check with a security
 122 // person before you modify it.
 123 void DoOpenNaClExecutableOnThreadPool(
 124     scoped_refptr<nacl::NaClHostMessageFilter> nacl_host_message_filter,
 125     const GURL& file_url,
 126     IPC::Message* reply_msg) {
 127   DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
 128
 129   base::FilePath file_path;
 130   if (!nacl::NaClBrowser::GetDelegate()->MapUrlToLocalFilePath(
 131           file_url,
 132           true /* use_blocking_api */,
 133           nacl_host_message_filter->profile_directory(),
 134           &file_path)) {
 135     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 136     return;
 137   }
 138
 139   base::File file = nacl::OpenNaClReadExecImpl(file_path,
 140                                                true /* is_executable */);
 141   if (file.IsValid()) {
 142     // This function is running on the blocking pool, but the path needs to be
 143     // registered in a structure owned by the IO thread.
 144     BrowserThread::PostTask(
 145         BrowserThread::IO, FROM_HERE,
 146         base::Bind(
 147             &DoRegisterOpenedNaClExecutableFile,
 148             nacl_host_message_filter,
 149             Passed(file.Pass()), file_path, reply_msg,
 150             static_cast<WriteFileInfoReply>(
 151                 NaClHostMsg_OpenNaClExecutable::WriteReplyParams)));
 152   } else {
 153     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 154     return;
 155   }
 156 }
 157
 158 }  // namespace
 159
 160 namespace nacl_file_host {
 161
 162 void GetReadonlyPnaclFd(
 163     scoped_refptr<nacl::NaClHostMessageFilter> nacl_host_message_filter,
 164     const std::string& filename,
 165     bool is_executable,
 166     IPC::Message* reply_msg) {
 167   if (!BrowserThread::PostBlockingPoolTask(
 168           FROM_HERE,
 169           base::Bind(&DoOpenPnaclFile,
 170                      nacl_host_message_filter,
 171                      filename,
 172                      is_executable,
 173                      reply_msg))) {
 174     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 175   }
 176 }
 177
 178 // This function is security sensitive.  Be sure to check with a security
 179 // person before you modify it.
 180 bool PnaclCanOpenFile(const std::string& filename,
 181                       base::FilePath* file_to_open) {
 182   if (filename.length() > kMaxFileLength)
 183     return false;
 184
 185   if (filename.empty())
 186     return false;
 187
 188   // Restrict character set of the file name to something really simple
 189   // (a-z, 0-9, and underscores).
 190   for (size_t i = 0; i < filename.length(); ++i) {
 191     char charAt = filename[i];
 192     if (charAt < 'a' || charAt > 'z')
 193       if (charAt < '0' || charAt > '9')
 194         if (charAt != '_')
 195           return false;
 196   }
 197
 198   // PNaCl must be installed.
 199   base::FilePath pnacl_dir;
 200   if (!nacl::NaClBrowser::GetDelegate()->GetPnaclDirectory(&pnacl_dir) ||
 201       pnacl_dir.empty())
 202     return false;
 203
 204   // Prepend the prefix to restrict files to a whitelisted set.
 205   base::FilePath full_path = pnacl_dir.AppendASCII(
 206       std::string(kExpectedFilePrefix) + filename);
 207   *file_to_open = full_path;
 208   return true;
 209 }
 210
 211 void OpenNaClExecutable(
 212     scoped_refptr<nacl::NaClHostMessageFilter> nacl_host_message_filter,
 213     int render_view_id,
 214     const GURL& file_url,
 215     IPC::Message* reply_msg) {
 216   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
 217     BrowserThread::PostTask(
 218         BrowserThread::UI, FROM_HERE,
 219         base::Bind(
 220             &OpenNaClExecutable,
 221             nacl_host_message_filter,
 222             render_view_id, file_url, reply_msg));
 223     return;
 224   }
 225
 226   // Make sure render_view_id is valid and that the URL is a part of the
 227   // render view's site. Without these checks, apps could probe the extension
 228   // directory or run NaCl code from other extensions.
 229   content::RenderViewHost* rvh = content::RenderViewHost::FromID(
 230       nacl_host_message_filter->render_process_id(), render_view_id);
 231   if (!rvh) {
 232     nacl_host_message_filter->BadMessageReceived();  // Kill the renderer.
 233     return;
 234   }
 235   content::SiteInstance* site_instance = rvh->GetSiteInstance();
 236   if (!content::SiteInstance::IsSameWebSite(site_instance->GetBrowserContext(),
 237                                             site_instance->GetSiteURL(),
 238                                             file_url)) {
 239     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 240     return;
 241   }
 242
 243   // The URL is part of the current app. Now query the extension system for the
 244   // file path and convert that to a file descriptor. This should be done on a
 245   // blocking pool thread.
 246   if (!BrowserThread::PostBlockingPoolTask(
 247       FROM_HERE,
 248       base::Bind(
 249           &DoOpenNaClExecutableOnThreadPool,
 250           nacl_host_message_filter,
 251           file_url, reply_msg))) {
 252     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 253   }
 254 }
 255
 256 }  // namespace nacl_file_host