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2418374def
When ignoreLockingMode option is used, we default to the unix-none or win32-none VFS, and enforce the connection to be read-only, because it's trivial to corrupt data using a no-lock VFS. Unfortunately read-only mode doesn't allow to open a WAL database if the journal files are missing, unless the device is marked as "immutable". There is no SQLITE_OPEN_* flag for immutable, and adding one could easily be misinterpreted since it only makes sense for read-only. This implement a readonly-immutable-nolock VFS shim on top of unix-none or win32-none that overrides device characteristics with immutable. When ignoreLockingMode option is specified, we use this VFS. It can only be used on read-only connections, as enforced both by Storage service and a MOZ_ASSERT. Differential Revision: https://phabricator.services.mozilla.com/D162492
131 lines
4.7 KiB
C++
131 lines
4.7 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* This VFS is built on top of the (unix|win32)-none, but it additionally
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* sets any opened file as immutable, that allows to also open in read-only
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* mode databases using WAL, or other journals that need auxiliary files, when
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* such files cannot be created.
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* This is useful when trying to read from third-party databases, avoiding any
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* risk of creating auxiliary files (e.g. journals).
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* It can only be used on read-only connections, because being a no-lock VFS
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* it would be trivial to corrupt the data.
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*/
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#include "nsDebug.h"
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#include "sqlite3.h"
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#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
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#if defined(XP_WIN)
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# define BASE_VFS "win32-none"
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#else
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# define BASE_VFS "unix-none"
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#endif
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#define VFS_NAME "readonly-immutable-nolock"
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namespace {
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static int vfsOpen(sqlite3_vfs* vfs, const char* zName, sqlite3_file* pFile,
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int flags, int* pOutFlags) {
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if ((flags & SQLITE_OPEN_READONLY) == 0) {
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// This is not done to be used in readwrite connections.
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return SQLITE_CANTOPEN;
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}
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sqlite3_vfs* pOrigVfs = ORIGVFS(vfs);
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int rc = pOrigVfs->xOpen(pOrigVfs, zName, pFile, flags, pOutFlags);
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if (rc != SQLITE_OK) {
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return rc;
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}
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const sqlite3_io_methods* pOrigMethods = pFile->pMethods;
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// If the IO version is higher than the last known one, you should update
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// this IO adding appropriate methods for any methods added in the version
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// change.
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MOZ_ASSERT(pOrigMethods->iVersion <= 3);
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static const sqlite3_io_methods vfs_io_methods = {
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pOrigMethods->iVersion, /* iVersion */
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pOrigMethods->xClose, /* xClose */
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pOrigMethods->xRead, /* xRead */
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pOrigMethods->xWrite, /* xWrite */
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pOrigMethods->xTruncate, /* xTruncate */
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pOrigMethods->xSync, /* xSync */
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pOrigMethods->xFileSize, /* xFileSize */
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pOrigMethods->xLock, /* xLock */
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pOrigMethods->xUnlock, /* xUnlock */
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pOrigMethods->xCheckReservedLock, /* xCheckReservedLock */
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pOrigMethods->xFileControl, /* xFileControl */
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pOrigMethods->xSectorSize, /* xSectorSize */
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[](sqlite3_file*) {
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return SQLITE_IOCAP_IMMUTABLE;
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}, /* xDeviceCharacteristics */
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pOrigMethods->xShmMap, /* xShmMap */
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pOrigMethods->xShmLock, /* xShmLock */
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pOrigMethods->xShmBarrier, /* xShmBarrier */
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pOrigMethods->xShmUnmap, /* xShmUnmap */
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pOrigMethods->xFetch, /* xFetch */
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pOrigMethods->xUnfetch /* xUnfetch */
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};
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pFile->pMethods = &vfs_io_methods;
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if (pOutFlags) {
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*pOutFlags = flags;
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}
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return SQLITE_OK;
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}
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} // namespace
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namespace mozilla::storage {
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UniquePtr<sqlite3_vfs> ConstructReadOnlyNoLockVFS() {
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if (sqlite3_vfs_find(VFS_NAME) != nullptr) {
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return nullptr;
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}
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sqlite3_vfs* pOrigVfs = sqlite3_vfs_find(BASE_VFS);
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if (!pOrigVfs) {
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return nullptr;
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}
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// If the VFS version is higher than the last known one, you should update
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// this VFS adding appropriate methods for any methods added in the version
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// change.
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MOZ_ASSERT(pOrigVfs->iVersion <= 3);
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static const sqlite3_vfs vfs = {
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pOrigVfs->iVersion, /* iVersion */
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pOrigVfs->szOsFile, /* szOsFile */
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pOrigVfs->mxPathname, /* mxPathname */
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nullptr, /* pNext */
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VFS_NAME, /* zName */
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pOrigVfs, /* pAppData */
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vfsOpen, /* xOpen */
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pOrigVfs->xDelete, /* xDelete */
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pOrigVfs->xAccess, /* xAccess */
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pOrigVfs->xFullPathname, /* xFullPathname */
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pOrigVfs->xDlOpen, /* xDlOpen */
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pOrigVfs->xDlError, /* xDlError */
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pOrigVfs->xDlSym, /* xDlSym */
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pOrigVfs->xDlClose, /* xDlClose */
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pOrigVfs->xRandomness, /* xRandomness */
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pOrigVfs->xSleep, /* xSleep */
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pOrigVfs->xCurrentTime, /* xCurrentTime */
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pOrigVfs->xGetLastError, /* xGetLastError */
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pOrigVfs->xCurrentTimeInt64, /* xCurrentTimeInt64 */
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pOrigVfs->xSetSystemCall, /* xSetSystemCall */
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pOrigVfs->xGetSystemCall, /* xGetSystemCall */
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pOrigVfs->xNextSystemCall /* xNextSystemCall */
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};
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return MakeUnique<sqlite3_vfs>(vfs);
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}
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} // namespace mozilla::storage
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