[Pkg-db-devel] Bug#437742: db: Encryption broken on arm (old ABI)

[Ben Hutchings]

I tracked this down to structure padding, which is weird on ARM.

The EINVAL comes from:
	if ((data_len % DB_AES_CHUNK) != 0)
		return (EINVAL);
in __aes_encrypt(), called by __db_encrypt_and_checksum_pg().

data_len is calculated as DBMETASIZE - P_OVERHEAD(dbp).  For an
encrypted database this evaluates to 448, a multiple of DB_AES_CHUNK =
16.  On ARM (old ABI) it evaluates to 446 because sizeof(PG_CRYPTO) is
40 and not 38 as expected.

So encrypted databases never worked on this architecture, and we should
be able to fix this up by replacing sizeof(PG_CRYPTO) with
SIZEOF_PG_CRYPTO defined to 38.  A similar hack is already used for
sizeof(PAGE).

Not yet tested on ARM, as it takes about 4 hours to run the test suite
on agnesi.  Will report the results when that's done.

Ben.

--- db-4.7.25.orig/dbinc/db_page.h
+++ db-4.7.25/dbinc/db_page.h
@@ -223,6 +223,17 @@
 	 */
 } PG_CRYPTO;
 
+/*
+ * With most compilers sizeof(PG_CRYPTO) == 38.  However some ABIs
+ * require it to be padded to 40 bytes.  The padding must be excluded
+ * from our size calculations due to the 16-byte alignment requirement
+ * for crypto.
+ *
+ * A similar problem applies to PG_CHKSUM, but it's too late to change
+ * that.
+ */
+#define SIZEOF_PG_CRYPTO 38
+
 typedef struct _db_page {
 	DB_LSN	  lsn;		/* 00-07: Log sequence number. */
 	db_pgno_t pgno;		/* 08-11: Current page number. */
@@ -258,7 +269,7 @@
  */
 #define	P_INP(dbp, pg)							\
 	((db_indx_t *)((u_int8_t *)(pg) + SIZEOF_PAGE +			\
-	(F_ISSET((dbp), DB_AM_ENCRYPT) ? sizeof(PG_CRYPTO) :		\
+	(F_ISSET((dbp), DB_AM_ENCRYPT) ? SIZEOF_PG_CRYPTO :		\
 	(F_ISSET((dbp), DB_AM_CHKSUM) ? sizeof(PG_CHKSUM) : 0))))
 
 #define	P_IV(dbp, pg)							\

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