bug 1581986 - fix undefined shift behavior in md4 implementation r=kjacobs

Using left shift on a uint8_t promotes it to a signed integer. If the shift is
large enough that the sign bit gets affected, we have undefined behavior. This
patch fixes this by first casting to uint32_t.

Differential Revision: https://phabricator.services.mozilla.com/D46820

--HG--
extra : moz-landing-system : lando

security/manager/ssl/md4.c

@@ -64,8 +64,8 @@ static void b2w(uint32_t* out, const uint8_t* in, uint32_t len) {
   bpend = in + len;
 
   for (; bp != bpend; bp += 4, ++wp) {
-    *wp = (uint32_t)(bp[0]) | (uint32_t)(bp[1] << 8) | (uint32_t)(bp[2] << 16) |
-          (uint32_t)(bp[3] << 24);
+    *wp = (uint32_t)bp[0] | ((uint32_t)bp[1] << 8) | ((uint32_t)bp[2] << 16) |
+          ((uint32_t)bp[3] << 24);
   }
 }