From bcbbfce020cd186d72ca37cef9b90a260f001591 Mon Sep 17 00:00:00 2001
From: Nick Parker <nparker@zetetic.net>
Date: Fri, 16 Aug 2013 11:09:18 -0500
Subject: [PATCH] Generate new salt on rekey

---
 src/crypto.c      | 20 +++++++++++++++++---
 src/crypto.h      |  2 ++
 src/crypto_impl.c |  8 ++++++++
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/crypto.c b/src/crypto.c
index 2551e6b..a440be0 100644
--- a/src/crypto.c
+++ b/src/crypto.c
@@ -354,6 +354,9 @@ int sqlite3_rekey(sqlite3 *db, const void *pKey, int nKey) {
       int rc, page_count;
       Pgno pgno;
       PgHdr *page;
+      char *new_salt;
+      char *original_salt;
+      int kdf_salt_sz = FILE_HEADER_SZ;
       Pager *pPager = pDb->pBt->pBt->pPager;
 
       sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
@@ -363,11 +366,11 @@ int sqlite3_rekey(sqlite3 *db, const void *pKey, int nKey) {
         CODEC_TRACE(("sqlite3_rekey: no codec attached to db, exiting\n"));
         return SQLITE_OK;
       }
-
+      
       sqlite3_mutex_enter(db->mutex);
 
       codec_set_pass_key(db, 0, pKey, nKey, CIPHER_WRITE_CTX);
-    
+            
       /* do stuff here to rewrite the database 
       ** 1. Create a transaction on the database
       ** 2. Iterate through each page, reading it and then writing it.
@@ -375,6 +378,15 @@ int sqlite3_rekey(sqlite3 *db, const void *pKey, int nKey) {
       **    note: don't deallocate rekey since it may be used in a subsequent iteration 
       */
       rc = sqlite3BtreeBeginTrans(pDb->pBt, 1); /* begin write transaction */
+
+      original_salt = sqlite3_malloc(kdf_salt_sz);
+      memset(original_salt, 0, kdf_salt_sz);
+      memcpy(original_salt, sqlcipher_codec_ctx_get_kdf_salt(ctx), kdf_salt_sz);
+      new_salt = sqlite3_malloc(kdf_salt_sz);
+      memset(new_salt, 0, kdf_salt_sz);
+      sqlcipher_codec_ctx_random(ctx, new_salt, kdf_salt_sz);
+      sqlcipher_codec_ctx_set_kdf_salt(ctx, new_salt);
+      
       sqlite3PagerPagecount(pPager, &page_count);
       for(pgno = 1; rc == SQLITE_OK && pgno <= page_count; pgno++) { /* pgno's start at 1 see pager.c:pagerAcquire */
         if(!sqlite3pager_is_mj_pgno(pPager, pgno)) { /* skip this page (see pager.c:pagerAcquire for reasoning) */
@@ -399,9 +411,11 @@ int sqlite3_rekey(sqlite3 *db, const void *pKey, int nKey) {
         sqlcipher_codec_key_copy(ctx, CIPHER_WRITE_CTX);
       } else {
         CODEC_TRACE(("sqlite3_rekey: rollback\n"));
+        sqlcipher_codec_ctx_set_kdf_salt(ctx, original_salt);
         sqlite3BtreeRollback(pDb->pBt, SQLITE_ABORT_ROLLBACK);
       }
-
+      sqlite3_free(new_salt);
+      sqlite3_free(original_salt);
       sqlite3_mutex_leave(db->mutex);
     }
     return SQLITE_OK;
diff --git a/src/crypto.h b/src/crypto.h
index a45b57c..5dee294 100644
--- a/src/crypto.h
+++ b/src/crypto.h
@@ -202,6 +202,8 @@ int sqlcipher_codec_ctx_unset_flag(codec_ctx *ctx, unsigned int flag);
 int sqlcipher_codec_ctx_get_flag(codec_ctx *ctx, unsigned int flag, int for_ctx);
 
 const char* sqlcipher_codec_get_cipher_provider(codec_ctx *ctx);
+void sqlcipher_codec_ctx_random(codec_ctx *ctx, void *dest, int dest_sz);
+void sqlcipher_codec_ctx_set_kdf_salt(codec_ctx *ctx, void *salt);
 #endif
 #endif
 /* END SQLCIPHER */
diff --git a/src/crypto_impl.c b/src/crypto_impl.c
index 1e7fa99..d61868e 100644
--- a/src/crypto_impl.c
+++ b/src/crypto_impl.c
@@ -839,5 +839,13 @@ const char* sqlcipher_codec_get_cipher_provider(codec_ctx *ctx) {
   return ctx->read_ctx->provider->get_provider_name(ctx->read_ctx);
 }
 
+void sqlcipher_codec_ctx_random(codec_ctx *ctx, void *dest, int dest_sz){
+  ctx->read_ctx->provider->random(ctx->read_ctx->provider_ctx, dest, dest_sz);
+}
+
+void sqlcipher_codec_ctx_set_kdf_salt(codec_ctx *ctx, void *salt) {
+  memcpy(ctx->kdf_salt, salt, ctx->kdf_salt_sz);
+}
+
 #endif
 /* END SQLCIPHER */