[PATCH] cipher-ocb: fix out-of-array stack memory access

[Jussi Kivilinna]

* cipher/cipher-ocb.c (bit_copy): Do not access memory beyond
's' array when bitoff > 8.
--

Signed-off-by: Jussi Kivilinna <jussi.kivilinna at iki.fi>
---
 cipher/cipher-ocb.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/cipher/cipher-ocb.c b/cipher/cipher-ocb.c
index b146d058..24db6a9e 100644
--- a/cipher/cipher-ocb.c
+++ b/cipher/cipher-ocb.c
@@ -67,18 +67,19 @@ double_block (u64 b[2])
 /* Copy OCB_BLOCK_LEN from buffer S starting at bit offset BITOFF to
  * buffer D.  */
 static void
-bit_copy (unsigned char *d, const unsigned char *s, unsigned int bitoff)
+bit_copy (unsigned char d[16], const unsigned char s[24], unsigned int bitoff)
 {
   u64 s0l, s1l, s1r, s2r;
   unsigned int shift;
+  unsigned int byteoff;
 
-  s += bitoff / 8;
+  byteoff = bitoff / 8;
   shift = bitoff % 8;
 
-  s0l = buf_get_be64 (s + 0);
-  s1l = buf_get_be64 (s + 8);
+  s0l = buf_get_be64 (s + byteoff + 0);
+  s1l = buf_get_be64 (s + byteoff + 8);
   s1r = shift ? s1l : 0;
-  s2r = shift ? buf_get_be64 (s + 16) : 0;
+  s2r = shift ? buf_get_be64 (s + 16) << (8 * byteoff) : 0;
 
   buf_put_be64 (d + 0, (s0l << shift) | (s1r >> ((64 - shift) & 63)));
   buf_put_be64 (d + 8, (s1l << shift) | (s2r >> ((64 - shift) & 63)));
-- 
2.25.1