The Tor Browser: storage/src/FileSystemModule.cpp@97036ab72558 (annotated)

storage/src/FileSystemModule.cpp@97036ab72558 (annotated)

storage/src/FileSystemModule.cpp

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
  * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "FileSystemModule.h"
 #include "sqlite3.h"
 #include "nsString.h"
 #include "nsISimpleEnumerator.h"
 #include "nsIFile.h"
 namespace {
 struct VirtualTableCursorBase
 {
   VirtualTableCursorBase()
   {
     memset(&mBase, 0, sizeof(mBase));
   }
   sqlite3_vtab_cursor mBase;
 };
 struct VirtualTableCursor : public VirtualTableCursorBase
 {
 public:
   VirtualTableCursor()
   : mRowId(-1)
   {
     mCurrentFileName.SetIsVoid(true);
   }
   const nsString& DirectoryPath() const
   {
     return mDirectoryPath;
   }
   const nsString& CurrentFileName() const
   {
     return mCurrentFileName;
   }
   int64_t RowId() const
   {
     return mRowId;
   }
   nsresult Init(const nsAString& aPath);
   nsresult NextFile();
 private:
   nsCOMPtr<nsISimpleEnumerator> mEntries;
   nsString mDirectoryPath;
   nsString mCurrentFileName;
   int64_t mRowId;
 };
 nsresult
 VirtualTableCursor::Init(const nsAString& aPath)
 {
   nsCOMPtr<nsIFile> directory =
     do_CreateInstance(NS_LOCAL_FILE_CONTRACTID);
   NS_ENSURE_TRUE(directory, NS_ERROR_FAILURE);
   nsresult rv = directory->InitWithPath(aPath);
   NS_ENSURE_SUCCESS(rv, rv);
   rv = directory->GetPath(mDirectoryPath);
   NS_ENSURE_SUCCESS(rv, rv);
   rv = directory->GetDirectoryEntries(getter_AddRefs(mEntries));
   NS_ENSURE_SUCCESS(rv, rv);
   rv = NextFile();
   NS_ENSURE_SUCCESS(rv, rv);
   return NS_OK;
 }
 nsresult
 VirtualTableCursor::NextFile()
 {
   bool hasMore;
   nsresult rv = mEntries->HasMoreElements(&hasMore);
   NS_ENSURE_SUCCESS(rv, rv);
   if (!hasMore) {
     mCurrentFileName.SetIsVoid(true);
     return NS_OK;
   }
   nsCOMPtr<nsISupports> entry;
   rv = mEntries->GetNext(getter_AddRefs(entry));
   NS_ENSURE_SUCCESS(rv, rv);
   nsCOMPtr<nsIFile> file = do_QueryInterface(entry);
   NS_ENSURE_TRUE(file, NS_ERROR_FAILURE);
   rv = file->GetLeafName(mCurrentFileName);
   NS_ENSURE_SUCCESS(rv, rv);
   mRowId++;
   return NS_OK;
 }
 int Connect(sqlite3* aDB, void* aAux, int aArgc, const char* const* aArgv,
             sqlite3_vtab** aVtab, char** aErr)
 {
   static const char virtualTableSchema[] =
     "CREATE TABLE fs ("
       "name TEXT, "
       "path TEXT"
     ")";
   int rc = sqlite3_declare_vtab(aDB, virtualTableSchema);
   if (rc != SQLITE_OK) {
     return rc;
   }
   sqlite3_vtab* vt = new sqlite3_vtab();
   memset(vt, 0, sizeof(*vt));
   *aVtab = vt;
   return SQLITE_OK;
 }
 int Disconnect(sqlite3_vtab* aVtab )
 {
   delete aVtab;
   return SQLITE_OK;
 }
 int BestIndex(sqlite3_vtab* aVtab, sqlite3_index_info* aInfo)
 {
   // Here we specify what index constraints we want to handle. That is, there
   // might be some columns with particular constraints in which we can help
   // SQLite narrow down the result set.
   //
   // For example, take the "path = x" where x is a directory. In this case,
   // we can narrow our search to just this directory instead of the entire file
   // system. This can be a significant optimization. So, we want to handle that
   // constraint. To do so, we would look for two specific input conditions:
   //
   // 1. aInfo->aConstraint[i].iColumn == 1
   // 2. aInfo->aConstraint[i].op == SQLITE_INDEX_CONSTRAINT_EQ
   //
   // The first states that the path column is being used in one of the input
   // constraints and the second states that the constraint involves the equal
   // operator.
   //
   // An even more specific search would be for name='xxx', in which case we
   // can limit the search to a single file, if it exists.
   //
   // What we have to do here is look for all of our index searches and select
   // the narrowest. We can only pick one, so obviously we want the one that
   // is the most specific, which leads to the smallest result set.
   for(int i = 0; i < aInfo->nConstraint; i++) {
     if (aInfo->aConstraint[i].iColumn == 1 && aInfo->aConstraint[i].usable) {
       if (aInfo->aConstraint[i].op & SQLITE_INDEX_CONSTRAINT_EQ) {
         aInfo->aConstraintUsage[i].argvIndex = 1;
       }
       break;
     }
     // TODO: handle single files (constrained also by the name column)
   }
   return SQLITE_OK;
 }
 int Open(sqlite3_vtab* aVtab, sqlite3_vtab_cursor** aCursor)
 {
   VirtualTableCursor* cursor = new VirtualTableCursor();
   *aCursor = reinterpret_cast<sqlite3_vtab_cursor*>(cursor);
   return SQLITE_OK;
 }
 int Close(sqlite3_vtab_cursor* aCursor)
 {
   VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);
   delete cursor;
   return SQLITE_OK;
 }
 int Filter(sqlite3_vtab_cursor* aCursor, int aIdxNum, const char* aIdxStr,
            int aArgc, sqlite3_value** aArgv)
 {
   VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);
   if(aArgc <= 0) {
     return SQLITE_OK;
   }
   nsDependentString path(
     reinterpret_cast<const char16_t*>(::sqlite3_value_text16(aArgv[0])));
   nsresult rv = cursor->Init(path);
   NS_ENSURE_SUCCESS(rv, SQLITE_ERROR);
   return SQLITE_OK;
 }
 int Next(sqlite3_vtab_cursor* aCursor)
 {
   VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);
   nsresult rv = cursor->NextFile();
   NS_ENSURE_SUCCESS(rv, SQLITE_ERROR);
   return SQLITE_OK;
 }
 int Eof(sqlite3_vtab_cursor* aCursor)
 {
   VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);
   return cursor->CurrentFileName().IsVoid() ? 1 : 0;
 }
 int Column(sqlite3_vtab_cursor* aCursor, sqlite3_context* aContext,
            int aColumnIndex)
 {
   VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);
   switch (aColumnIndex) {
     // name
     case 0: {
       const nsString& name = cursor->CurrentFileName();
       sqlite3_result_text16(aContext, name.get(),
                             name.Length() * sizeof(char16_t),
                             SQLITE_TRANSIENT);
       break;
     }
     // path
     case 1: {
       const nsString& path = cursor->DirectoryPath();
       sqlite3_result_text16(aContext, path.get(),
                             path.Length() * sizeof(char16_t),
                             SQLITE_TRANSIENT);
       break;
     }
     default:
       NS_NOTREACHED("Unsupported column!");
   }
   return SQLITE_OK;
 }
 int RowId(sqlite3_vtab_cursor* aCursor, sqlite3_int64* aRowid)
 {
   VirtualTableCursor* cursor = reinterpret_cast<VirtualTableCursor*>(aCursor);
   *aRowid = cursor->RowId();
   return SQLITE_OK;
 }
 } // anonymous namespace
 namespace mozilla {
 namespace storage {
 int RegisterFileSystemModule(sqlite3* aDB, const char* aName)
 {
   static sqlite3_module module = {
 ,
     Connect,
     Connect,
     BestIndex,
     Disconnect,
     Disconnect,
     Open,
     Close,
     Filter,
     Next,
     Eof,
     Column,
     RowId,
     nullptr,
     nullptr,
     nullptr,
     nullptr,
     nullptr,
     nullptr,
     nullptr
   };
   return sqlite3_create_module(aDB, aName, &module, nullptr);
 }
 } // namespace storage
 } // namespace mozilla

The Tor Browser / annotate

storage/src/FileSystemModule.cpp@97036ab72558 (annotated)

storage/src/FileSystemModule.cpp