Introduce WAL compatibility configuration parameter

Unfortunately WAL journal mode was in fact broken in all versions <= 1.2.5. To allow to recover a hot WAL journal left behind by an application using a version <= 1.2.5, the global configuration parameter mc_legacy_wal has been introduced. It should be noted that parallel use of the new version and a version <= 1.2.5 will most likely not work. For recovery of a hot WAL journal use mc_legacy_wal=1.

src/cipher_common.c

@@ -25,6 +25,7 @@ static CipherParams commonParams[] =
 {
   { "cipher",     CODEC_TYPE, CODEC_TYPE, 1, CODEC_TYPE_MAX },
   { "hmac_check",          1,          1, 0,              1 },
+  { "mc_legacy_wal",       0,          0, 0,              1 },
   CIPHER_PARAMS_SENTINEL
 };
 
@@ -205,6 +206,7 @@ sqlite3mcCodecInit(Codec* codec)
   {
     codec->m_isEncrypted = 0;
     codec->m_hmacCheck = 1;
+    codec->m_walLegacy = 0;
 
     codec->m_hasReadCipher = 0;
     codec->m_readCipherType = CODEC_TYPE_UNKNOWN;
@@ -264,6 +266,7 @@ sqlite3mcCodecSetup(Codec* codec, int cipherType, char* userPassword, int passwo
   CipherParams* globalParams = sqlite3mcGetCipherParams(codec->m_db, 0);
   codec->m_isEncrypted = 1;
   codec->m_hmacCheck = sqlite3mcGetCipherParameter(globalParams, "hmac_check");
+  codec->m_walLegacy = sqlite3mcGetCipherParameter(globalParams, "mc_legacy_wal");
   codec->m_hasReadCipher = 1;
   codec->m_hasWriteCipher = 1;
   codec->m_readCipherType = cipherType;
@@ -292,6 +295,7 @@ sqlite3mcSetupWriteCipher(Codec* codec, int cipherType, char* userPassword, int
   }
   codec->m_isEncrypted = 1;
   codec->m_hmacCheck = sqlite3mcGetCipherParameter(globalParams, "hmac_check");
+  codec->m_walLegacy = sqlite3mcGetCipherParameter(globalParams, "mc_legacy_wal");
   codec->m_hasWriteCipher = 1;
   codec->m_writeCipherType = cipherType;
   codec->m_writeCipher = codecDescriptorTable[codec->m_writeCipherType-1]->m_allocateCipher(codec->m_db);
@@ -475,6 +479,7 @@ sqlite3mcCodecCopy(Codec* codec, Codec* other)
   int rc = SQLITE_OK;
   codec->m_isEncrypted = other->m_isEncrypted;
   codec->m_hmacCheck = other->m_hmacCheck;
+  codec->m_walLegacy = other->m_walLegacy;
   codec->m_hasReadCipher = other->m_hasReadCipher;
   codec->m_hasWriteCipher = other->m_hasWriteCipher;
   codec->m_readCipherType = other->m_readCipherType;

src/cipher_common.h

@@ -39,6 +39,7 @@ typedef struct _Codec
 {
   int           m_isEncrypted;
   int           m_hmacCheck;
+  int           m_walLegacy;
   /* Read cipher */
   int           m_hasReadCipher;
   int           m_readCipherType;

src/cipher_config.c

@@ -656,6 +656,7 @@ sqlite3mcConfigureFromUri(sqlite3* db, const char *zDbName, int configDefault)
         int skipLegacy = 0;
         /* Set global parameters (cipher and hmac_check) */
         int hmacCheck = sqlite3_uri_boolean(dbFileName, "hmac_check", 1);
+        int walLegacy = sqlite3_uri_boolean(dbFileName, "mc_legacy_wal", 0);
         if (configDefault)
         {
           sqlite3mc_config(db, "default:cipher", globalCodecParameterTable[j].m_id);
@@ -668,6 +669,7 @@ sqlite3mcConfigureFromUri(sqlite3* db, const char *zDbName, int configDefault)
         {
           sqlite3mc_config(db, "hmac_check", hmacCheck);
         }
+        sqlite3mc_config(db, "mc_legacy_wal", walLegacy);
 
 #if HAVE_CIPHER_SQLCIPHER
         /* Special handling for SQLCipher */
@@ -794,6 +796,13 @@ sqlite3mcFileControlPragma(sqlite3* db, const char* zDbName, int op, void* pArg)
       ((char**)pArg)[0] = sqlite3_mprintf("%d", value);
       rc = SQLITE_OK;
     }
+    else if (sqlite3StrICmp(pragmaName, "mc_legacy_wal") == 0)
+    {
+      int walLegacy = (pragmaValue != NULL) ? sqlite3GetBoolean(pragmaValue, 0) : -1;
+      int value = sqlite3mc_config(db, "mc_legacy_wal", walLegacy);
+      ((char**)pArg)[0] = sqlite3_mprintf("%d", value);
+      rc = SQLITE_OK;
+    }
     else if (sqlite3StrICmp(pragmaName, "key") == 0)
     {
       rc = sqlite3_key_v2(db, zDbName, pragmaValue, -1);

src/sqlite3mc_version.h

@@ -14,8 +14,8 @@
 
 #define SQLITE3MC_VERSION_MAJOR      1
 #define SQLITE3MC_VERSION_MINOR      3
-#define SQLITE3MC_VERSION_RELEASE    1
+#define SQLITE3MC_VERSION_RELEASE    2
 #define SQLITE3MC_VERSION_SUBRELEASE 0
-#define SQLITE3MC_VERSION_STRING     "SQLite3 Multiple Ciphers 1.3.1"
+#define SQLITE3MC_VERSION_STRING     "SQLite3 Multiple Ciphers 1.3.2"
 
 #endif /* SQLITE3MC_VERSION_H_ */

src/sqlite3mc_vfs.c

@@ -281,7 +281,7 @@ SQLITE_PRIVATE void* sqlite3mcPagerCodec(PgHdr* pPg)
   {
     sqlite3mc_file* mcFile = (sqlite3mc_file*) pFile;
     Codec* codec = mcFile->codec;
-    if (codec != 0 && sqlite3mcIsEncrypted(codec))
+    if (codec != 0 && codec->m_walLegacy == 0 && sqlite3mcIsEncrypted(codec))
     {
       aData = sqlite3mcCodec(codec, pPg->pData, pPg->pgno, 6);
     }
@@ -676,7 +676,19 @@ static int mcReadWal(sqlite3_file* pFile, const void* buffer, int count, sqlite3
       */
       if (pageNo != 0)
       {
-        void* bufferDecrypted = sqlite3mcCodec(codec, (char*) buffer, pageNo, 3);
+        void* bufferDecrypted = sqlite3mcCodec(codec, (char*)buffer, pageNo, 3);
+      }
+    }
+    else if (codec->m_walLegacy != 0 && count == pageSize + walFrameHeaderSize)
+    {
+      int pageNo = sqlite3Get4byte(buffer);
+
+      /*
+      ** Decrypt page content if page number is valid
+      */
+      if (pageNo != 0)
+      {
+        void* bufferDecrypted = sqlite3mcCodec(codec, (char*)buffer+walFrameHeaderSize, pageNo, 3);
       }
     }
   }
@@ -905,7 +917,7 @@ static int mcWriteWal(sqlite3_file* pFile, const void* buffer, int count, sqlite
   sqlite3mc_file* mcFile = (sqlite3mc_file*) pFile;
   Codec* codec = (mcFile->pMainDb) ? mcFile->pMainDb->codec : 0;
 
-  if (codec != 0 && sqlite3mcIsEncrypted(codec))
+  if (codec != 0 && codec->m_walLegacy != 0 && sqlite3mcIsEncrypted(codec))
   {
     const int pageSize = sqlite3mcGetPageSize(codec);
 
@@ -921,7 +933,7 @@ static int mcWriteWal(sqlite3_file* pFile, const void* buffer, int count, sqlite
       ** immediately before writing the corresponding page content.
       ** Page numbers and checksums are written to file independently.
       ** Therefore it is necessary to explicitly read the page number
-      ** on writing to file the contetn of a page.
+      ** on writing to file the content of a page.
       */
       rc = REALFILE(pFile)->pMethods->xRead(REALFILE(pFile), ac, 4, offset - walFrameHeaderSize);
       if (rc == SQLITE_OK)
@@ -945,6 +957,26 @@ static int mcWriteWal(sqlite3_file* pFile, const void* buffer, int count, sqlite
         rc = REALFILE(pFile)->pMethods->xWrite(REALFILE(pFile), buffer, count, offset);
       }
     }
+    else if (count == pageSize + walFrameHeaderSize)
+    {
+      int pageNo = sqlite3Get4byte(buffer);
+      if (pageNo != 0)
+      {
+        /*
+        ** Encrypt the page buffer, but only if the page number is valid
+        */
+        void* bufferEncrypted = sqlite3mcCodec(codec, (char*)buffer+walFrameHeaderSize, pageNo, 7);
+        rc = REALFILE(pFile)->pMethods->xWrite(REALFILE(pFile), buffer, walFrameHeaderSize, offset);
+        rc = REALFILE(pFile)->pMethods->xWrite(REALFILE(pFile), bufferEncrypted, pageSize, offset+walFrameHeaderSize);
+      }
+      else
+      {
+        /*
+        ** Write buffer without encryption if the page number could not be determined
+        */
+        rc = REALFILE(pFile)->pMethods->xWrite(REALFILE(pFile), buffer, count, offset);
+      }
+    }
     else
     {
       /*
@@ -1014,7 +1046,7 @@ static int mcIoWrite(sqlite3_file* pFile, const void* buffer, int count, sqlite3
     */
   }
 #endif
-#if 0
+#if 1
   /*
   ** The page content is encrypted in memory in the WAL journal handler.
   ** This provides for compatibility with legacy applications using the