lsn.diff

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File	+	−
src/backend/access/transam/xloginsert.c	0	0

diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
new file mode 100644
index 3ec67d4..57f4d71
*** a/src/backend/access/transam/xloginsert.c
--- b/src/backend/access/transam/xloginsert.c
*************** XLogResetInsertion(void)
*** 208,213 ****
--- 208,215 ----
  /*
   * Register a reference to a buffer with the WAL record being constructed.
   * This must be called for every page that the WAL-logged operation modifies.
+  * Because of page-level encryption, You cannot reference more than one
+  * RelFileNode in a WAL record;  Assert checks for that.
   */
  void
  XLogRegisterBuffer(uint8 block_id, Buffer buffer, uint8 flags)
*************** XLogRegisterBuffer(uint8 block_id, Buffe
*** 235,241 ****
  
  	/*
  	 * Check that this page hasn't already been registered with some other
! 	 * block_id.
  	 */
  #ifdef USE_ASSERT_CHECKING
  	{
--- 237,243 ----
  
  	/*
  	 * Check that this page hasn't already been registered with some other
! 	 * block_id, and check for different RelFileNodes in the same WAL record.
  	 */
  #ifdef USE_ASSERT_CHECKING
  	{
*************** XLogRegisterBuffer(uint8 block_id, Buffe
*** 248,256 ****
--- 250,274 ----
  			if (i == block_id || !regbuf_old->in_use)
  				continue;
  
+ 			/* check for duplicate block numbers */
  			Assert(!RelFileNodeEquals(regbuf_old->rnode, regbuf->rnode) ||
  				   regbuf_old->forkno != regbuf->forkno ||
  				   regbuf_old->block != regbuf->block);
+ 
+ 			/*
+ 			 * The initialization vector (IV) is used for page-level
+ 			 * encryption.  We use the LSN and page number as the IV, and IV
+ 			 * values must never be reused since it is insecure.	It is safe
+ 			 * to use the LSN on multiple pages in the same relation since
+ 			 * the page number is part of the IV.  It is unsafe to reuse the
+ 			 * LSN in different relations because the page number might be
+ 			 * the same, and hence the IV.  Therefore, we check here that
+ 			 * we don't have WAL records for different relations using the
+ 			 * same LSN.  We only encrypt MAIN_FORKNUM files.
+ 			 */
+ 			Assert(RelFileNodeEquals(regbuf_old->rnode, regbuf->rnode) ||
+ 				   regbuf_old->forkno != MAIN_FORKNUM ||
+ 				   regbuf->forkno != MAIN_FORKNUM);
  		}
  	}
  #endif