twofish: Fix undefined shift.

diff --git a/ChangeLog b/ChangeLog
index 2208874c876662477986e84591aa9ef22ea00b55..d068636c46f3be4f0bf9c9a510570321a9ab7e37 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2016-03-15  Niels Möller  <nisse@lysator.liu.se>
 
+       * twofish.c (gf_multiply): Change return value to uint32_t, to
+       make shifting of the return value well defined, without any type
+       casts. Fixes an undefined shift in compute_s, reported by Nikos
+       Mavrogiannopoulos.
+       (h_byte): Deleted type casts.
+
        * blowfish.c (blowfish_encrypt, blowfish_decrypt): Use READ_UINT32
        macro. Fixes an undefined shift, reported by Nikos
        Mavrogiannopoulos.

diff --git a/twofish.c b/twofish.c
index 45b08545b413658e9385307a78c5bb01f0fa1f7d..cfc6be92a3120d725509423ce974e89dda4767c5 100644 (file)
--- a/twofish.c
+++ b/twofish.c
@@ -135,9 +135,10 @@ static const uint8_t q1[256] = {
 
 /* ------------------------------------------------------------------------- */
 
-/* uint8_t gf_multiply(uint8_t p, uint8_t a, uint8_t b)
+/* uint32_t gf_multiply(uint8_t p, uint8_t a, uint8_t b)
  *
- * Multiplication in GF(2^8).
+ * Multiplication in GF(2^8). Larger return type, to avoid need for
+ * type casts when the return value is shifted left.
  *
  * This function multiplies a times b in the Galois Field GF(2^8) with
  * primitive polynomial p.
@@ -149,7 +150,7 @@ static const uint8_t q1[256] = {
  * operation.
  */
 
-static uint8_t
+static uint32_t
 gf_multiply(uint8_t p, uint8_t a, uint8_t b)
 {
   uint32_t shift  = b;
@@ -241,10 +242,10 @@ h_byte(int k, int i, uint8_t x, uint8_t l0, uint8_t l1, uint8_t l2, uint8_t l3)
               q_table[i][2][k == 2 ? x : l2 ^
                 q_table[i][1][k == 3 ? x : l3 ^ q_table[i][0][x]]]]];
 
-  return ( ((uint32_t)gf_multiply(0x69, mds_matrix[0][i], y))
-          | ((uint32_t)gf_multiply(0x69, mds_matrix[1][i], y) << 8)
-          | ((uint32_t)gf_multiply(0x69, mds_matrix[2][i], y) << 16)
-          | ((uint32_t)gf_multiply(0x69, mds_matrix[3][i], y) << 24) );
+  return ( (gf_multiply(0x69, mds_matrix[0][i], y))
+          | (gf_multiply(0x69, mds_matrix[1][i], y) << 8)
+          | (gf_multiply(0x69, mds_matrix[2][i], y) << 16)
+          | (gf_multiply(0x69, mds_matrix[3][i], y) << 24) );
 }
 
 /* uint32_t h(int k, uint8_t x, uint32_t l0, uint32_t l1, uint32_t l2, uint32_t l3);