random seed used in the hash of all strings to avoid intentional

collisions

1 files changed, 36 insertions, 1 deletions

diff --git a/lstate.c b/lstate.c
index bc13897b..5031a0a1 100644
--- a/lstate.c
+++ b/lstate.c
@@ -1,11 +1,12 @@
 /*
-** $Id: lstate.c,v 2.91 2011/08/23 17:24:34 roberto Exp roberto $
+** $Id: lstate.c,v 2.92 2011/10/03 17:54:25 roberto Exp roberto $
 ** Global State
 ** See Copyright Notice in lua.h
 */
 
 
 #include <stddef.h>
+#include <string.h>
 
 #define lstate_c
 #define LUA_CORE
@@ -42,6 +43,17 @@
 
 
 /*
+** a macro to help the creation of a unique random seed when a state is
+** created; the seed is used to randomize hashes.
+*/
+#if !defined(luai_makeseed)
+#include <time.h>
+#define luai_makeseed(L)        cast(size_t, time(NULL))
+#endif
+
+
+
+/*
 ** thread state + extra space
 */
 typedef struct LX {
@@ -66,6 +78,28 @@ typedef struct LG {
 
 
 /*
+** Compute an initial seed as random as possible. In ANSI, rely on
+** Address Space Layour Randomization (if present) to increase
+** randomness..
+*/
+#define addbuff(b,p,e) \
+  { size_t t = cast(size_t, e); \
+    memcpy(buff + p, &t, sizeof(t)); p += sizeof(t); }
+
+static unsigned int makeseed (lua_State *L) {
+  char buff[4 * sizeof(size_t)];
+  unsigned int h = luai_makeseed();
+  int p = 0;
+  addbuff(buff, p, L);  /* heap variable */
+  addbuff(buff, p, &h);  /* local variable */
+  addbuff(buff, p, luaO_nilobject);  /* global variable */
+  addbuff(buff, p, &lua_newstate);  /* public function */
+  lua_assert(p == sizeof(buff));
+  return luaS_hash(buff, p, h);
+}
+
+
+/*
 ** set GCdebt to a new value keeping the value (totalbytes + GCdebt)
 ** invariant
 */
@@ -242,6 +276,7 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->frealloc = f;
   g->ud = ud;
   g->mainthread = L;
+  g->seed = makeseed(L);
   g->uvhead.u.l.prev = &g->uvhead;
   g->uvhead.u.l.next = &g->uvhead;
   g->gcrunning = 0;  /* no GC while building state */