src/chrome/browser/nacl_host/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 "chrome/browser/nacl_host/nacl_file_host.h"
   6
   7 #include "base/bind.h"
   8 #include "base/file_util.h"
   9 #include "base/files/file_path.h"
  10 #include "base/path_service.h"
  11 #include "base/platform_file.h"
  12 #include "base/strings/utf_string_conversions.h"
  13 #include "base/threading/sequenced_worker_pool.h"
  14 #include "chrome/browser/nacl_host/nacl_host_message_filter.h"
  15 #include "components/nacl/browser/nacl_browser.h"
  16 #include "components/nacl/common/nacl_browser_delegate.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     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 bool PnaclDoOpenFile(const base::FilePath& file_to_open,
  42                      base::PlatformFile* out_file) {
  43   base::PlatformFileError error_code;
  44   *out_file = base::CreatePlatformFile(file_to_open,
  45                                        base::PLATFORM_FILE_OPEN |
  46                                        base::PLATFORM_FILE_READ,
  47                                        NULL,
  48                                        &error_code);
  49   if (error_code != base::PLATFORM_FILE_OK) {
  50     return false;
  51   }
  52   return true;
  53 }
  54
  55 void DoOpenPnaclFile(
  56     scoped_refptr<NaClHostMessageFilter> nacl_host_message_filter,
  57     const std::string& filename,
  58     IPC::Message* reply_msg) {
  59   DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
  60   base::FilePath full_filepath;
  61
  62   // PNaCl must be installed.
  63   base::FilePath pnacl_dir;
  64   if (!nacl::NaClBrowser::GetDelegate()->GetPnaclDirectory(&pnacl_dir) ||
  65       !base::PathExists(pnacl_dir)) {
  66     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  67     return;
  68   }
  69
  70   // Do some validation.
  71   if (!nacl_file_host::PnaclCanOpenFile(filename, &full_filepath)) {
  72     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  73     return;
  74   }
  75
  76   base::PlatformFile file_to_open;
  77   if (!PnaclDoOpenFile(full_filepath, &file_to_open)) {
  78     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  79     return;
  80   }
  81
  82   // Send the reply!
  83   // Do any DuplicateHandle magic that is necessary first.
  84   IPC::PlatformFileForTransit target_desc =
  85       IPC::GetFileHandleForProcess(file_to_open,
  86                                    nacl_host_message_filter->PeerHandle(),
  87                                    true /* Close source */);
  88   if (target_desc == IPC::InvalidPlatformFileForTransit()) {
  89     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
  90     return;
  91   }
  92   NaClHostMsg_GetReadonlyPnaclFD::WriteReplyParams(
  93       reply_msg, target_desc);
  94   nacl_host_message_filter->Send(reply_msg);
  95 }
  96
  97 void DoRegisterOpenedNaClExecutableFile(
  98     scoped_refptr<NaClHostMessageFilter> nacl_host_message_filter,
  99     base::PlatformFile file,
 100     base::FilePath file_path,
 101     IPC::Message* reply_msg) {
 102   // IO thread owns the NaClBrowser singleton.
 103   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 104
 105   nacl::NaClBrowser* nacl_browser = nacl::NaClBrowser::GetInstance();
 106   uint64 file_token_lo = 0;
 107   uint64 file_token_hi = 0;
 108   nacl_browser->PutFilePath(file_path, &file_token_lo, &file_token_hi);
 109
 110   IPC::PlatformFileForTransit file_desc = IPC::GetFileHandleForProcess(
 111       file,
 112       nacl_host_message_filter->PeerHandle(),
 113       true /* close_source */);
 114
 115   NaClHostMsg_OpenNaClExecutable::WriteReplyParams(
 116       reply_msg, file_desc, file_token_lo, file_token_hi);
 117   nacl_host_message_filter->Send(reply_msg);
 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<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, true /* use_blocking_api */, &file_path)) {
 132     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 133     return;
 134   }
 135
 136   base::PlatformFile file;
 137   nacl::OpenNaClExecutableImpl(file_path, &file);
 138   if (file != base::kInvalidPlatformFileValue) {
 139     // This function is running on the blocking pool, but the path needs to be
 140     // registered in a structure owned by the IO thread.
 141     BrowserThread::PostTask(
 142         BrowserThread::IO, FROM_HERE,
 143         base::Bind(
 144             &DoRegisterOpenedNaClExecutableFile,
 145             nacl_host_message_filter,
 146             file, file_path, reply_msg));
 147   } else {
 148     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 149     return;
 150   }
 151 }
 152
 153 }  // namespace
 154
 155 namespace nacl_file_host {
 156
 157 void GetReadonlyPnaclFd(
 158     scoped_refptr<NaClHostMessageFilter> nacl_host_message_filter,
 159     const std::string& filename,
 160     IPC::Message* reply_msg) {
 161   if (!BrowserThread::PostBlockingPoolTask(
 162           FROM_HERE,
 163           base::Bind(&DoOpenPnaclFile,
 164                      nacl_host_message_filter,
 165                      filename,
 166                      reply_msg))) {
 167     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 168   }
 169 }
 170
 171 // This function is security sensitive.  Be sure to check with a security
 172 // person before you modify it.
 173 bool PnaclCanOpenFile(const std::string& filename,
 174                       base::FilePath* file_to_open) {
 175   if (filename.length() > kMaxFileLength)
 176     return false;
 177
 178   if (filename.empty())
 179     return false;
 180
 181   // Restrict character set of the file name to something really simple
 182   // (a-z, 0-9, and underscores).
 183   for (size_t i = 0; i < filename.length(); ++i) {
 184     char charAt = filename[i];
 185     if (charAt < 'a' || charAt > 'z')
 186       if (charAt < '0' || charAt > '9')
 187         if (charAt != '_')
 188           return false;
 189   }
 190
 191   // PNaCl must be installed.
 192   base::FilePath pnacl_dir;
 193   if (!nacl::NaClBrowser::GetDelegate()->GetPnaclDirectory(&pnacl_dir) ||
 194       pnacl_dir.empty())
 195     return false;
 196
 197   // Prepend the prefix to restrict files to a whitelisted set.
 198   base::FilePath full_path = pnacl_dir.AppendASCII(
 199       std::string(kExpectedFilePrefix) + filename);
 200   *file_to_open = full_path;
 201   return true;
 202 }
 203
 204 void OpenNaClExecutable(
 205     scoped_refptr<NaClHostMessageFilter> nacl_host_message_filter,
 206     int render_view_id,
 207     const GURL& file_url,
 208     IPC::Message* reply_msg) {
 209   if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
 210     BrowserThread::PostTask(
 211         BrowserThread::UI, FROM_HERE,
 212         base::Bind(
 213             &OpenNaClExecutable,
 214             nacl_host_message_filter,
 215             render_view_id, file_url, reply_msg));
 216     return;
 217   }
 218
 219   // Make sure render_view_id is valid and that the URL is a part of the
 220   // render view's site. Without these checks, apps could probe the extension
 221   // directory or run NaCl code from other extensions.
 222   content::RenderViewHost* rvh = content::RenderViewHost::FromID(
 223       nacl_host_message_filter->render_process_id(), render_view_id);
 224   if (!rvh) {
 225     nacl_host_message_filter->BadMessageReceived();  // Kill the renderer.
 226     return;
 227   }
 228   content::SiteInstance* site_instance = rvh->GetSiteInstance();
 229   if (!content::SiteInstance::IsSameWebSite(site_instance->GetBrowserContext(),
 230                                             site_instance->GetSiteURL(),
 231                                             file_url)) {
 232     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 233     return;
 234   }
 235
 236   // The URL is part of the current app. Now query the extension system for the
 237   // file path and convert that to a file descriptor. This should be done on a
 238   // blocking pool thread.
 239   if (!BrowserThread::PostBlockingPoolTask(
 240       FROM_HERE,
 241       base::Bind(
 242           &DoOpenNaClExecutableOnThreadPool,
 243           nacl_host_message_filter,
 244           file_url, reply_msg))) {
 245     NotifyRendererOfError(nacl_host_message_filter.get(), reply_msg);
 246   }
 247 }
 248
 249 }  // namespace nacl_file_host