Adjust plaintext header size rules

- for sqlcipher the plaintext header size must be a multiple of the AES blocksize (16 bytes)
- for legacy chacha20 (resp. sqleet) the plaintext header size can be an arbitrary value greater or equal 0
- for non-legacy chacha20, ascon128, and aegis the plaintext header size can be 0 or a value greater or equal between 24

The upper limit for the plaintext header size is currently 100. In theory, it could be limited by the page size reduced by the number of reserved bytes.

Author: utelle

src/cipher_chacha20.c

@@ -198,7 +198,8 @@ EncryptPageChaCha20Cipher(void* cipher, int page, unsigned char* data, int len,
     if (plaintextHeaderSize > 0)
     {
       usePlaintextHeader = 1;
-      offset = (plaintextHeaderSize > CIPHER_PAGE1_OFFSET) ? plaintextHeaderSize : CIPHER_PAGE1_OFFSET;
+      offset = (chacha20Cipher->m_legacy != 0) ? plaintextHeaderSize :
+               (plaintextHeaderSize > CIPHER_PAGE1_OFFSET) ? plaintextHeaderSize : CIPHER_PAGE1_OFFSET;
     }
     else
     {
@@ -283,7 +284,8 @@ DecryptPageChaCha20Cipher(void* cipher, int page, unsigned char* data, int len,
     if (plaintextHeaderSize > 0)
     {
       usePlaintextHeader = 1;
-      offset = (plaintextHeaderSize > CIPHER_PAGE1_OFFSET) ? plaintextHeaderSize : CIPHER_PAGE1_OFFSET;
+      offset = (chacha20Cipher->m_legacy != 0) ? plaintextHeaderSize :
+               (plaintextHeaderSize > CIPHER_PAGE1_OFFSET) ? plaintextHeaderSize : CIPHER_PAGE1_OFFSET;
     }
     else
     {

src/cipher_config.c

@@ -178,7 +178,7 @@ sqlite3mc_cipher_name(int cipherIndex)
 }
 
 static
-int checkParameterValue(const char* paramName, int value)
+int checkParameterValue(const char* paramName, int value, const char* cipherName)
 {
   int ok = 1;
   if (sqlite3_stricmp(paramName, "legacy_page_size") == 0 && value > 0)
@@ -187,7 +187,10 @@ int checkParameterValue(const char* paramName, int value)
   }
   if (ok && sqlite3_stricmp(paramName, "plaintext_header_size") == 0 && value > 0)
   {
-    ok = value % 16 == 0;
+    if (sqlite3_stricmp(cipherName, "sqlcipher") == 0)
+    {
+      ok = value % 16 == 0;
+    }
   }
   return ok;
 }
@@ -299,7 +302,7 @@ sqlite3mc_config_cipher(sqlite3* db, const char* cipherName, const char* paramNa
       if (!hasMinPrefix && !hasMaxPrefix)
       {
         if (newValue >= 0 && newValue >= param->m_minValue && newValue <= param->m_maxValue &&
-            checkParameterValue(paramName, newValue))
+            checkParameterValue(paramName, newValue, cipherName))
         {
           if (hasDefaultPrefix)
           {

src/cipher_sqlcipher.c

@@ -349,16 +349,24 @@ EncryptPageSQLCipherCipher(void* cipher, int page, unsigned char* data, int len,
   int legacy = sqlCipherCipher->m_legacy;
   int nReserved = (reserved == 0 && legacy == 0) ? 0 : GetReservedSQLCipherCipher(cipher);
   int n = len - nReserved;
-  int offset = (page == 1) ? (sqlCipherCipher->m_legacy != 0) ? 16 : 24 : 0;
+  int offset = 0;
   int blen;
   unsigned char iv[128];
   int usePlaintextHeader = 0;
 
   /* Check whether a plaintext header should be used */
-  if (page == 1 && sqlCipherCipher->m_legacy >= SQLCIPHER_VERSION_4 && sqlCipherCipher->m_plaintextHeaderSize > 0)
+  if (page == 1)
   {
-    usePlaintextHeader = 1;
-    offset = sqlCipherCipher->m_plaintextHeaderSize;
+    int plaintextHeaderSize = sqlCipherCipher->m_plaintextHeaderSize;
+    offset = (sqlCipherCipher->m_legacy != 0) ? 16 : 24;
+    if (plaintextHeaderSize > 0)
+    {
+      usePlaintextHeader = 1;
+      if (sqlCipherCipher->m_legacy >= SQLCIPHER_VERSION_4)
+      {
+        offset = plaintextHeaderSize;
+      }
+    }
   }
 
   /* Check whether number of required reserved bytes and actually reserved bytes match */
@@ -423,17 +431,25 @@ DecryptPageSQLCipherCipher(void* cipher, int page, unsigned char* data, int len,
   int legacy = sqlCipherCipher->m_legacy;
   int nReserved = (reserved == 0 && legacy == 0) ? 0 : GetReservedSQLCipherCipher(cipher);
   int n = len - nReserved;
-  int offset = (page == 1) ? (sqlCipherCipher->m_legacy != 0) ? 16 : 24 : 0;
+  int offset = 0;
   int hmacOk = 1;
   int blen;
   unsigned char iv[128];
   int usePlaintextHeader = 0;
 
   /* Check whether a plaintext header should be used */
-  if (page == 1 && sqlCipherCipher->m_legacy >= SQLCIPHER_VERSION_4 && sqlCipherCipher->m_plaintextHeaderSize > 0)
+  if (page == 1)
   {
-    usePlaintextHeader = 1;
-    offset = sqlCipherCipher->m_plaintextHeaderSize;
+    int plaintextHeaderSize = sqlCipherCipher->m_plaintextHeaderSize;
+    offset = (sqlCipherCipher->m_legacy != 0) ? 16 : 24;
+    if (plaintextHeaderSize > 0)
+    {
+      usePlaintextHeader = 1;
+      if (sqlCipherCipher->m_legacy >= SQLCIPHER_VERSION_4)
+      {
+        offset = plaintextHeaderSize;
+      }
+    }
   }
 
   /* Check whether number of required reserved bytes and actually reserved bytes match */