/*
** 2020-04-20
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
******************************************************************************
**
** This file implements a VFS shim that obfuscates database content
** written to disk by applying a CipherStrategy.
**
** COMPILING
**
** This extension requires SQLite 3.32.0 or later.
**
**
** LOADING
**
** Initialize it using a single API call as follows:
**
**     sqlite3_obfsvfs_init();
**
** Obfsvfs is a VFS Shim. When loaded, "obfsvfs" becomes the new
** default VFS and it uses the prior default VFS as the next VFS
** down in the stack.  This is normally what you want.  However, it
** complex situations where multiple VFS shims are being loaded,
** it might be important to ensure that obfsvfs is loaded in the
** correct order so that it sequences itself into the default VFS
** Shim stack in the right order.
**
** USING
**
** Open database connections using the sqlite3_open_v2() with
** the SQLITE_OPEN_URI flag and using a URI filename that includes
** the query parameter "key=XXXXXXXXXXX..." where the XXXX... consists
** of 64 hexadecimal digits (32 bytes of content).
**
** Create a new encrypted database by opening a file that does not
** yet exist using the key= query parameter.
**
** LIMITATIONS:
**
**    *   An obfuscated database must be created as such.  There is
**        no way to convert an existing database file into an
**        obfuscated database file other than to run ".dump" on the
**        older database and reimport the SQL text into a new
**        obfuscated database.
**
**    *   There is no way to change the key value, other than to
**        ".dump" and restore the database
**
**    *   The database page size must be exactly 8192 bytes.  No other
**        database page sizes are currently supported.
**
**    *   Memory-mapped I/O does not work for obfuscated databases.
**        If you think about it, memory-mapped I/O doesn't make any
**        sense for obfuscated databases since you have to make a
**        copy of the content to deobfuscate anyhow - you might as
**        well use normal read()/write().
**
**    *   Only the main database, the rollback journal, and WAL file
**        are obfuscated.  Other temporary files used for things like
**        SAVEPOINTs or as part of a large external sort remain
**        unobfuscated.
**
**    *   Requires SQLite 3.32.0 or later.
*/
#include "sqlite3.h"
#include <string.h>
#include <ctype.h>
#include <stdio.h> /* For debugging only */

#include "mozilla/dom/quota/IPCStreamCipherStrategy.h"
#include "mozilla/ScopeExit.h"
#include "nsPrintfCString.h"

/*
** Forward declaration of objects used by this utility
*/
using ObfsVfs = sqlite3_vfs;

/*
** Useful datatype abbreviations
*/
#if !defined(SQLITE_CORE)
using u8 = unsigned char;
#endif

/* Access to a lower-level VFS that (might) implement dynamic loading,
** access to randomness, etc.
*/
#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
#define ORIGFILE(p) ((sqlite3_file*)(((ObfsFile*)(p)) + 1))

/*
** Database page size for obfuscated databases
*/
#define OBFS_PGSZ 8192

using namespace mozilla;
using namespace mozilla::dom::quota;

/* An open file */
struct ObfsFile {
  sqlite3_file base;  /* IO methods */
  const char* zFName; /* Original name of the file */
  bool inCkpt;        /* Currently doing a checkpoint */
  ObfsFile* pPartner; /* Ptr from WAL to main-db, or from main-db to WAL */
  void* pTemp;        /* Temporary storage for encoded pages */
  IPCStreamCipherStrategy*
      encryptCipherStrategy; /* CipherStrategy for encryption */
  IPCStreamCipherStrategy*
      decryptCipherStrategy; /* CipherStrategy for decryption */
};

/*
** Methods for ObfsFile
*/
static int obfsClose(sqlite3_file*);
static int obfsRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
static int obfsWrite(sqlite3_file*, const void*, int iAmt, sqlite3_int64 iOfst);
static int obfsTruncate(sqlite3_file*, sqlite3_int64 size);
static int obfsSync(sqlite3_file*, int flags);
static int obfsFileSize(sqlite3_file*, sqlite3_int64* pSize);
static int obfsLock(sqlite3_file*, int);
static int obfsUnlock(sqlite3_file*, int);
static int obfsCheckReservedLock(sqlite3_file*, int* pResOut);
static int obfsFileControl(sqlite3_file*, int op, void* pArg);
static int obfsSectorSize(sqlite3_file*);
static int obfsDeviceCharacteristics(sqlite3_file*);
static int obfsShmMap(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
static int obfsShmLock(sqlite3_file*, int offset, int n, int flags);
static void obfsShmBarrier(sqlite3_file*);
static int obfsShmUnmap(sqlite3_file*, int deleteFlag);
static int obfsFetch(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void** pp);
static int obfsUnfetch(sqlite3_file*, sqlite3_int64 iOfst, void* p);

/*
** Methods for ObfsVfs
*/
static int obfsOpen(sqlite3_vfs*, const char*, sqlite3_file*, int, int*);
static int obfsDelete(sqlite3_vfs*, const char* zPath, int syncDir);
static int obfsAccess(sqlite3_vfs*, const char* zPath, int flags, int*);
static int obfsFullPathname(sqlite3_vfs*, const char* zPath, int, char* zOut);
static void* obfsDlOpen(sqlite3_vfs*, const char* zPath);
static void obfsDlError(sqlite3_vfs*, int nByte, char* zErrMsg);
static void (*obfsDlSym(sqlite3_vfs* pVfs, void* p, const char* zSym))(void);
static void obfsDlClose(sqlite3_vfs*, void*);
static int obfsRandomness(sqlite3_vfs*, int nByte, char* zBufOut);
static int obfsSleep(sqlite3_vfs*, int nMicroseconds);
static int obfsCurrentTime(sqlite3_vfs*, double*);
static int obfsGetLastError(sqlite3_vfs*, int, char*);
static int obfsCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
static int obfsSetSystemCall(sqlite3_vfs*, const char*, sqlite3_syscall_ptr);
static sqlite3_syscall_ptr obfsGetSystemCall(sqlite3_vfs*, const char* z);
static const char* obfsNextSystemCall(sqlite3_vfs*, const char* zName);

static const sqlite3_io_methods obfs_io_methods = {
    3,                         /* iVersion */
    obfsClose,                 /* xClose */
    obfsRead,                  /* xRead */
    obfsWrite,                 /* xWrite */
    obfsTruncate,              /* xTruncate */
    obfsSync,                  /* xSync */
    obfsFileSize,              /* xFileSize */
    obfsLock,                  /* xLock */
    obfsUnlock,                /* xUnlock */
    obfsCheckReservedLock,     /* xCheckReservedLock */
    obfsFileControl,           /* xFileControl */
    obfsSectorSize,            /* xSectorSize */
    obfsDeviceCharacteristics, /* xDeviceCharacteristics */
    obfsShmMap,                /* xShmMap */
    obfsShmLock,               /* xShmLock */
    obfsShmBarrier,            /* xShmBarrier */
    obfsShmUnmap,              /* xShmUnmap */
    obfsFetch,                 /* xFetch */
    obfsUnfetch                /* xUnfetch */
};

static constexpr int kKeyBytes = 32;
static constexpr int kIvBytes = IPCStreamCipherStrategy::BlockPrefixLength;
static constexpr int kClearTextPrefixBytesOnFirstPage = 32;
static constexpr int kReservedBytes = 32;
static constexpr int kBasicBlockSize = IPCStreamCipherStrategy::BasicBlockSize;
static_assert(kClearTextPrefixBytesOnFirstPage % kBasicBlockSize == 0);
static_assert(kReservedBytes % kBasicBlockSize == 0);

/* Obfuscate a page using p->encryptCipherStrategy.
**
** A new random nonce is created and stored in the last 32 bytes
** of the page.  All other bytes of the page are obfuscasted using the
** CipherStrategy.  Except, for page-1 (including the SQLite
** database header) the first 32 bytes are not obfuscated
**
** Return a pointer to the obfuscated content, which is held in the
** p->pTemp buffer.  Or return a NULL pointer if something goes wrong.
** Errors are reported using NS_WARNING().
*/
static void* obfsEncode(ObfsFile* p, /* File containing page to be obfuscated */
                        u8* a,       /* database page to be obfuscated */
                        int nByte /* Bytes of content in a[]. Must be a multiple
                                     of kBasicBlockSize. */
) {
  u8 aIv[kIvBytes];
  u8* pOut;
  int i;

  static_assert((kIvBytes & (kIvBytes - 1)) == 0);
  sqlite3_randomness(kIvBytes, aIv);
  pOut = (u8*)p->pTemp;
  if (pOut == nullptr) {
    pOut = static_cast<u8*>(sqlite3_malloc64(nByte));
    if (pOut == nullptr) {
      NS_WARNING(nsPrintfCString("unable to allocate a buffer in which to"
                                 " write obfuscated database content for %s",
                                 p->zFName)
                     .get());
      return nullptr;
    }
    p->pTemp = pOut;
  }
  if (memcmp(a, "SQLite format 3", 16) == 0) {
    i = kClearTextPrefixBytesOnFirstPage;
    if (a[20] != kReservedBytes) {
      NS_WARNING(nsPrintfCString("obfuscated database must have reserved-bytes"
                                 " set to %d",
                                 kReservedBytes)
                     .get());
      return nullptr;
    }
    memcpy(pOut, a, kClearTextPrefixBytesOnFirstPage);
  } else {
    i = 0;
  }
  const int payloadLength = nByte - kReservedBytes - i;
  MOZ_ASSERT(payloadLength > 0);
  // XXX I guess this can be done in-place as well, then we don't need the
  // temporary page at all, I guess?
  p->encryptCipherStrategy->Cipher(
      Span{aIv}, Span{a + i, static_cast<unsigned>(payloadLength)},
      Span{pOut + i, static_cast<unsigned>(payloadLength)});
  memcpy(pOut + nByte - kReservedBytes, aIv, kIvBytes);

  return pOut;
}

/* De-obfuscate a page using p->decryptCipherStrategy.
**
** The deobfuscation is done in-place.
**
** For pages that begin with the SQLite header text, the first
** 32 bytes are not deobfuscated.
*/
static void obfsDecode(ObfsFile* p, /* File containing page to be obfuscated */
                       u8* a,       /* database page to be obfuscated */
                       int nByte /* Bytes of content in a[]. Must be a multiple
                                    of kBasicBlockSize. */
) {
  int i;

  if (memcmp(a, "SQLite format 3", 16) == 0) {
    i = kClearTextPrefixBytesOnFirstPage;
  } else {
    i = 0;
  }
  const int payloadLength = nByte - kReservedBytes - i;
  MOZ_ASSERT(payloadLength > 0);
  p->decryptCipherStrategy->Cipher(
      Span{a + nByte - kReservedBytes, kIvBytes},
      Span{a + i, static_cast<unsigned>(payloadLength)},
      Span{a + i, static_cast<unsigned>(payloadLength)});
}

/*
** Close an obfsucated file.
*/
static int obfsClose(sqlite3_file* pFile) {
  ObfsFile* p = (ObfsFile*)pFile;
  if (p->pPartner) {
    MOZ_ASSERT(p->pPartner->pPartner == p);
    p->pPartner->pPartner = nullptr;
    p->pPartner = nullptr;
  }
  sqlite3_free(p->pTemp);

  delete p->decryptCipherStrategy;
  delete p->encryptCipherStrategy;

  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xClose(pFile);
}

/*
** Read data from an obfuscated file.
**
** If the file is less than one full page in length, then return
** a substitute "prototype" page-1.  This prototype page one
** specifies a database in WAL mode with an 8192-byte page size
** and a 32-byte reserved-bytes value.  Those settings are necessary
** for obfuscation to function correctly.
*/
static int obfsRead(sqlite3_file* pFile, void* zBuf, int iAmt,
                    sqlite_int64 iOfst) {
  int rc;
  ObfsFile* p = (ObfsFile*)pFile;
  pFile = ORIGFILE(pFile);
  rc = pFile->pMethods->xRead(pFile, zBuf, iAmt, iOfst);
  if (rc == SQLITE_OK) {
    if (iAmt == OBFS_PGSZ && !p->inCkpt) {
      obfsDecode(p, (u8*)zBuf, iAmt);
    }
  } else if (SQLITE_IOERR_SHORT_READ && iOfst == 0 && iAmt >= 100) {
    static const unsigned char aEmptyDb[] = {
        0x53, 0x51, 0x4c, 0x69, 0x74,           0x65, 0x20, 0x66,
        0x6f, 0x72, 0x6d, 0x61, 0x74,           0x20, 0x33, 0x00,
        0x20, 0x00, 0x02, 0x02, kReservedBytes, 0x40, 0x20, 0x20,
        0x00, 0x00, 0x00, 0x01, 0x00,           0x00, 0x00, 0x01};
    memcpy(zBuf, aEmptyDb, sizeof(aEmptyDb));
    memset(((u8*)zBuf) + sizeof(aEmptyDb), 0, iAmt - sizeof(aEmptyDb));
    rc = SQLITE_OK;
  }
  return rc;
}

/*
** Write data to an obfuscated file or journal.
*/
static int obfsWrite(sqlite3_file* pFile, const void* zBuf, int iAmt,
                     sqlite_int64 iOfst) {
  ObfsFile* p = (ObfsFile*)pFile;
  pFile = ORIGFILE(pFile);
  if (iAmt == OBFS_PGSZ && !p->inCkpt) {
    zBuf = obfsEncode(p, (u8*)zBuf, iAmt);
    if (zBuf == nullptr) {
      return SQLITE_IOERR;
    }
  }
  return pFile->pMethods->xWrite(pFile, zBuf, iAmt, iOfst);
}

/*
** Truncate an obfuscated file.
*/
static int obfsTruncate(sqlite3_file* pFile, sqlite_int64 size) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xTruncate(pFile, size);
}

/*
** Sync an obfuscated file.
*/
static int obfsSync(sqlite3_file* pFile, int flags) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xSync(pFile, flags);
}

/*
** Return the current file-size of an obfuscated file.
*/
static int obfsFileSize(sqlite3_file* pFile, sqlite_int64* pSize) {
  ObfsFile* p = (ObfsFile*)pFile;
  pFile = ORIGFILE(p);
  return pFile->pMethods->xFileSize(pFile, pSize);
}

/*
** Lock an obfuscated file.
*/
static int obfsLock(sqlite3_file* pFile, int eLock) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xLock(pFile, eLock);
}

/*
** Unlock an obfuscated file.
*/
static int obfsUnlock(sqlite3_file* pFile, int eLock) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xUnlock(pFile, eLock);
}

/*
** Check if another file-handle holds a RESERVED lock on an obfuscated file.
*/
static int obfsCheckReservedLock(sqlite3_file* pFile, int* pResOut) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xCheckReservedLock(pFile, pResOut);
}

/*
** File control method. For custom operations on an obfuscated file.
*/
static int obfsFileControl(sqlite3_file* pFile, int op, void* pArg) {
  int rc;
  ObfsFile* p = (ObfsFile*)pFile;
  pFile = ORIGFILE(pFile);
  if (op == SQLITE_FCNTL_PRAGMA) {
    char** azArg = (char**)pArg;
    MOZ_ASSERT(azArg[1] != nullptr);
    if (azArg[2] != nullptr && sqlite3_stricmp(azArg[1], "page_size") == 0) {
      /* Do not allow page size changes on an obfuscated database */
      return SQLITE_OK;
    }
  } else if (op == SQLITE_FCNTL_CKPT_START || op == SQLITE_FCNTL_CKPT_DONE) {
    p->inCkpt = op == SQLITE_FCNTL_CKPT_START;
    if (p->pPartner) {
      p->pPartner->inCkpt = p->inCkpt;
    }
  }
  rc = pFile->pMethods->xFileControl(pFile, op, pArg);
  if (rc == SQLITE_OK && op == SQLITE_FCNTL_VFSNAME) {
    *(char**)pArg = sqlite3_mprintf("obfs/%z", *(char**)pArg);
  }
  return rc;
}

/*
** Return the sector-size in bytes for an obfuscated file.
*/
static int obfsSectorSize(sqlite3_file* pFile) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xSectorSize(pFile);
}

/*
** Return the device characteristic flags supported by an obfuscated file.
*/
static int obfsDeviceCharacteristics(sqlite3_file* pFile) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xDeviceCharacteristics(pFile);
}

/* Create a shared memory file mapping */
static int obfsShmMap(sqlite3_file* pFile, int iPg, int pgsz, int bExtend,
                      void volatile** pp) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xShmMap(pFile, iPg, pgsz, bExtend, pp);
}

/* Perform locking on a shared-memory segment */
static int obfsShmLock(sqlite3_file* pFile, int offset, int n, int flags) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xShmLock(pFile, offset, n, flags);
}

/* Memory barrier operation on shared memory */
static void obfsShmBarrier(sqlite3_file* pFile) {
  pFile = ORIGFILE(pFile);
  pFile->pMethods->xShmBarrier(pFile);
}

/* Unmap a shared memory segment */
static int obfsShmUnmap(sqlite3_file* pFile, int deleteFlag) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xShmUnmap(pFile, deleteFlag);
}

/* Fetch a page of a memory-mapped file */
static int obfsFetch(sqlite3_file* pFile, sqlite3_int64 iOfst, int iAmt,
                     void** pp) {
  *pp = nullptr;
  return SQLITE_OK;
}

/* Release a memory-mapped page */
static int obfsUnfetch(sqlite3_file* pFile, sqlite3_int64 iOfst, void* pPage) {
  pFile = ORIGFILE(pFile);
  return pFile->pMethods->xUnfetch(pFile, iOfst, pPage);
}

/*
** Translate a single byte of Hex into an integer.
** This routine only works if h really is a valid hexadecimal
** character:  0..9a..fA..F
*/
static u8 obfsHexToInt(int h) {
  MOZ_ASSERT((h >= '0' && h <= '9') || (h >= 'a' && h <= 'f') ||
             (h >= 'A' && h <= 'F'));
#if 1 /* ASCII */
  h += 9 * (1 & (h >> 6));
#else /* EBCDIC */
  h += 9 * (1 & ~(h >> 4));
#endif
  return (u8)(h & 0xf);
}

/*
** Open a new file.
**
** If the file is an ordinary database file, or a rollback or WAL journal
** file, and if the key=XXXX parameter exists, then try to open the file
** as an obfuscated database.  All other open attempts fall through into
** the lower-level VFS shim.
**
** If the key=XXXX parameter exists but is not 64-bytes of hex key, then
** put an error message in NS_WARNING() and return SQLITE_CANTOPEN.
*/
static int obfsOpen(sqlite3_vfs* pVfs, const char* zName, sqlite3_file* pFile,
                    int flags, int* pOutFlags) {
  ObfsFile* p;
  sqlite3_file* pSubFile;
  sqlite3_vfs* pSubVfs;
  int rc, i;
  const char* zKey;
  u8 aKey[kKeyBytes];
  pSubVfs = ORIGVFS(pVfs);
  if (flags &
      (SQLITE_OPEN_MAIN_DB | SQLITE_OPEN_WAL | SQLITE_OPEN_MAIN_JOURNAL)) {
    zKey = sqlite3_uri_parameter(zName, "key");
  } else {
    zKey = nullptr;
  }
  if (zKey == nullptr) {
    return pSubVfs->xOpen(pSubVfs, zName, pFile, flags, pOutFlags);
  }
  for (i = 0;
       i < kKeyBytes && isxdigit(zKey[i * 2]) && isxdigit(zKey[i * 2 + 1]);
       i++) {
    aKey[i] = (obfsHexToInt(zKey[i * 2]) << 4) | obfsHexToInt(zKey[i * 2 + 1]);
  }
  if (i != kKeyBytes) {
    NS_WARNING(
        nsPrintfCString("invalid query parameter on %s: key=%s", zName, zKey)
            .get());
    return SQLITE_CANTOPEN;
  }
  p = (ObfsFile*)pFile;
  memset(p, 0, sizeof(*p));

  auto encryptCipherStrategy = MakeUnique<IPCStreamCipherStrategy>();
  auto decryptCipherStrategy = MakeUnique<IPCStreamCipherStrategy>();

  auto resetMethods = MakeScopeExit([pFile] { pFile->pMethods = nullptr; });

  if (NS_WARN_IF(NS_FAILED(encryptCipherStrategy->Init(
          CipherMode::Encrypt, Span{aKey, sizeof(aKey)},
          IPCStreamCipherStrategy::MakeBlockPrefix())))) {
    return SQLITE_ERROR;
  }

  if (NS_WARN_IF(NS_FAILED(decryptCipherStrategy->Init(
          CipherMode::Decrypt, Span{aKey, sizeof(aKey)})))) {
    return SQLITE_ERROR;
  }

  pSubFile = ORIGFILE(pFile);
  p->base.pMethods = &obfs_io_methods;
  rc = pSubVfs->xOpen(pSubVfs, zName, pSubFile, flags, pOutFlags);
  if (rc) {
    return rc;
  }

  resetMethods.release();

  if (flags & (SQLITE_OPEN_WAL | SQLITE_OPEN_MAIN_JOURNAL)) {
    sqlite3_file* pDb = sqlite3_database_file_object(zName);
    p->pPartner = (ObfsFile*)pDb;
    MOZ_ASSERT(p->pPartner->pPartner == nullptr);
    p->pPartner->pPartner = p;
  }
  p->zFName = zName;

  p->encryptCipherStrategy = encryptCipherStrategy.release();
  p->decryptCipherStrategy = decryptCipherStrategy.release();

  return SQLITE_OK;
}

/*
** All other VFS methods are pass-thrus.
*/
static int obfsDelete(sqlite3_vfs* pVfs, const char* zPath, int syncDir) {
  return ORIGVFS(pVfs)->xDelete(ORIGVFS(pVfs), zPath, syncDir);
}
static int obfsAccess(sqlite3_vfs* pVfs, const char* zPath, int flags,
                      int* pResOut) {
  return ORIGVFS(pVfs)->xAccess(ORIGVFS(pVfs), zPath, flags, pResOut);
}
static int obfsFullPathname(sqlite3_vfs* pVfs, const char* zPath, int nOut,
                            char* zOut) {
  return ORIGVFS(pVfs)->xFullPathname(ORIGVFS(pVfs), zPath, nOut, zOut);
}
static void* obfsDlOpen(sqlite3_vfs* pVfs, const char* zPath) {
  return ORIGVFS(pVfs)->xDlOpen(ORIGVFS(pVfs), zPath);
}
static void obfsDlError(sqlite3_vfs* pVfs, int nByte, char* zErrMsg) {
  ORIGVFS(pVfs)->xDlError(ORIGVFS(pVfs), nByte, zErrMsg);
}
static void (*obfsDlSym(sqlite3_vfs* pVfs, void* p, const char* zSym))(void) {
  return ORIGVFS(pVfs)->xDlSym(ORIGVFS(pVfs), p, zSym);
}
static void obfsDlClose(sqlite3_vfs* pVfs, void* pHandle) {
  ORIGVFS(pVfs)->xDlClose(ORIGVFS(pVfs), pHandle);
}
static int obfsRandomness(sqlite3_vfs* pVfs, int nByte, char* zBufOut) {
  return ORIGVFS(pVfs)->xRandomness(ORIGVFS(pVfs), nByte, zBufOut);
}
static int obfsSleep(sqlite3_vfs* pVfs, int nMicroseconds) {
  return ORIGVFS(pVfs)->xSleep(ORIGVFS(pVfs), nMicroseconds);
}
static int obfsCurrentTime(sqlite3_vfs* pVfs, double* pTimeOut) {
  return ORIGVFS(pVfs)->xCurrentTime(ORIGVFS(pVfs), pTimeOut);
}
static int obfsGetLastError(sqlite3_vfs* pVfs, int a, char* b) {
  return ORIGVFS(pVfs)->xGetLastError(ORIGVFS(pVfs), a, b);
}
static int obfsCurrentTimeInt64(sqlite3_vfs* pVfs, sqlite3_int64* p) {
  return ORIGVFS(pVfs)->xCurrentTimeInt64(ORIGVFS(pVfs), p);
}
static int obfsSetSystemCall(sqlite3_vfs* pVfs, const char* zName,
                             sqlite3_syscall_ptr pCall) {
  return ORIGVFS(pVfs)->xSetSystemCall(ORIGVFS(pVfs), zName, pCall);
}
static sqlite3_syscall_ptr obfsGetSystemCall(sqlite3_vfs* pVfs,
                                             const char* zName) {
  return ORIGVFS(pVfs)->xGetSystemCall(ORIGVFS(pVfs), zName);
}
static const char* obfsNextSystemCall(sqlite3_vfs* pVfs, const char* zName) {
  return ORIGVFS(pVfs)->xNextSystemCall(ORIGVFS(pVfs), zName);
}

namespace mozilla {
namespace storage {

const char* GetObfuscatingVFSName() { return "obfsvfs"; }

UniquePtr<sqlite3_vfs> ConstructObfuscatingVFS(const char* aBaseVFSName) {
  MOZ_ASSERT(aBaseVFSName);

  if (sqlite3_vfs_find(GetObfuscatingVFSName()) != nullptr) {
    return nullptr;
  }
  sqlite3_vfs* const pOrig = sqlite3_vfs_find(aBaseVFSName);
  if (pOrig == nullptr) {
    return nullptr;
  }

#ifdef DEBUG
  // If the VFS version is higher than the last known one, you should update
  // this VFS adding appropriate methods for any methods added in the version
  // change.
  static constexpr int kLastKnownVfsVersion = 3;
  MOZ_ASSERT(pOrig->iVersion <= kLastKnownVfsVersion);
#endif

  const sqlite3_vfs obfs_vfs = {
      pOrig->iVersion,                                      /* iVersion  */
      static_cast<int>(pOrig->szOsFile + sizeof(ObfsFile)), /* szOsFile */
      pOrig->mxPathname,                                    /* mxPathname */
      nullptr,                                              /* pNext */
      GetObfuscatingVFSName(),                              /* zName */
      pOrig,                                                /* pAppData */
      obfsOpen,                                             /* xOpen */
      obfsDelete,                                           /* xDelete */
      obfsAccess,                                           /* xAccess */
      obfsFullPathname,                                     /* xFullPathname */
      obfsDlOpen,                                           /* xDlOpen */
      obfsDlError,                                          /* xDlError */
      obfsDlSym,                                            /* xDlSym */
      obfsDlClose,                                          /* xDlClose */
      obfsRandomness,                                       /* xRandomness */
      obfsSleep,                                            /* xSleep */
      obfsCurrentTime,                                      /* xCurrentTime */
      obfsGetLastError,                                     /* xGetLastError */
      obfsCurrentTimeInt64, /* xCurrentTimeInt64 */
      obfsSetSystemCall,    /* xSetSystemCall */
      obfsGetSystemCall,    /* xGetSystemCall */
      obfsNextSystemCall    /* xNextSystemCall */
  };

  return MakeUnique<sqlite3_vfs>(obfs_vfs);
}

}  // namespace storage
}  // namespace mozilla