Replace offset with count of initial unaligned bytes.

1 files changed, 19 insertions, 16 deletions

diff --git a/ocb.c b/ocb.c
index d53380f8..0c2a7f12 100644
--- a/ocb.c
+++ b/ocb.c
@@ -369,35 +369,34 @@ ocb_crypt_n_4way (struct ocb_ctx *ctx, const struct ocb_key *key,
 }
 #endif
 
-/* Rotate bytes (8-c) positions to the right, in memory order. */
+/* Rotate bytes c positions to the right, in memory order. */
 #if WORDS_BIGENDIAN
 # define MEM_ROTATE_RIGHT(c, s0, s1) do {				\
-    uint64_t __rotate_t = ((s0) >> (64-8*(c))) | ((s1) << (8*(c)));	\
-    (s1) = ((s1) >> (64-8*(c))) | ((s0) << (8*(c)));			\
+    uint64_t __rotate_t = ((s0) >> (8*(c))) | ((s1) << (64-8*(c)));	\
+    (s1) = ((s1) >> (8*(c))) | ((s0) << (64-8*(c)));			\
     (s0) = __rotate_t;							\
   } while (0)
 #else
 # define MEM_ROTATE_RIGHT(c, s0, s1) do {				\
-    uint64_t __rotate_t = ((s0) << (64-8*(c))) | ((s1) >> (8*(c)));	\
-    (s1) = ((s1) << (64-8*(c))) | ((s0) >> (8*(c)));			\
+    uint64_t __rotate_t = ((s0) << (8*(c))) | ((s1) >> (64-8*(c)));	\
+    (s1) = ((s1) << (8*(c))) | ((s0) >> (64-8*(c)));			\
     (s0) = __rotate_t;							\
   } while (0)
 #endif
 
 /* Mask for the first c bytes in memory */
 #if WORDS_BIGENDIAN
-# define MEM_MASK(c) (-((uint64_t) 1 << 8*(c)))
+# define MEM_MASK(c) (-((uint64_t) 1 << (64 - 8*(c))))
 #else
-# define MEM_MASK(c) (((uint64_t) 1 << (64-8*(c))) - 1)
+# define MEM_MASK(c) (((uint64_t) 1 << (8*(c))) - 1)
 #endif
 
 /* Checksum of n complete blocks. */
-
 static void
 ocb_checksum_n (union nettle_block16 *checksum,
 		size_t n, const uint8_t *src)
 {
-  unsigned offset = (uintptr_t) src & 7;
+  unsigned initial;
   uint64_t edge_word = 0;
   uint64_t s0, s1;
 
@@ -406,12 +405,16 @@ ocb_checksum_n (union nettle_block16 *checksum,
       memxor (checksum->b, src, OCB_BLOCK_SIZE);
       return;
     }
-  if (offset > 0)
+
+  /* Initial unaligned bytes. */
+  initial = -(uintptr_t) src & 7;
+
+  if (initial > 0)
     {
       /* Input not 64-bit aligned. Read initial bytes. */
       unsigned i;
       /* Edge word is read in big-endian order */
-      for (i = 8 - offset; i > 0; i--)
+      for (i = initial; i > 0; i--)
 	edge_word = (edge_word << 8) + *src++;
       n--;
     }
@@ -422,18 +425,18 @@ ocb_checksum_n (union nettle_block16 *checksum,
       s0 ^= ((const uint64_t *) src)[0];
       s1 ^= ((const uint64_t *) src)[1];
     }
-  if (offset > 0)
+  if (initial > 0)
     {
       unsigned i;
       uint64_t mask;
       s0 ^= ((const uint64_t *) src)[0];
-      for (i = offset, src += 8; i > 0; i--)
+      for (i = 8 - initial, src += 8; i > 0; i--)
 	edge_word = (edge_word << 8) + *src++;
 
-      /* Rotate [s0, s1] right 8 - offset bytes. */
-      MEM_ROTATE_RIGHT(offset, s0, s1);
+      /* Rotate [s0, s1] right initial bytes. */
+      MEM_ROTATE_RIGHT(initial, s0, s1);
       /* Add in the edge bytes.  */
-      mask = MEM_MASK(offset);
+      mask = MEM_MASK(initial);
       edge_word = bswap64_if_le (edge_word);
       s0 ^= (edge_word & mask);
       s1 ^= (edge_word & ~mask);