lua: properly initialize random number generator

Formerly multiple instances could use the same seed,
which prevented the retry logic in Lua modules (e.g. prefill) from
retrying at different times.

AFAIK security impact is zero aside from potential thundering-herd
problem with many kresd instances.

diff --git a/NEWS b/NEWS
index 9bedf67100278d593138e397ba04886fba5c6e0d..413759954b349040f071c20bf73c8a0d3a94ee5b 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,7 @@ Bugfixes
 - lua resolve(): correctly include EDNS0 in the virtual packet (!963)
   Custom modules might have been confused by that.
 - do not leak bogus data into SERVFAIL answers (#396)
+- improve random Lua number generator initialization (!979)
 
 Incompatible changes
 --------------------

diff --git a/daemon/engine.c b/daemon/engine.c
index 3dd9faeb2b2de8b5d92f5552afb2869cf1fd3fba..0c34c4b2fb371e14555fddcb208a21c4b4420395 100644 (file)
--- a/daemon/engine.c
+++ b/daemon/engine.c
@@ -500,6 +500,13 @@ static int init_state(struct engine *engine)
        lua_setglobal(engine->L, "map");
        lua_pushlightuserdata(engine->L, engine);
        lua_setglobal(engine->L, "__engine");
+       /* Random number generator */
+       lua_getfield(engine->L, LUA_GLOBALSINDEX, "math");
+       lua_getfield(engine->L, -1, "randomseed");
+       lua_remove(engine->L, -2);
+       lua_Number seed = kr_rand_bytes(sizeof(lua_Number));
+       lua_pushnumber(engine->L, seed);
+       lua_call(engine->L, 1, 0);
        return kr_ok();
 }
 

diff --git a/modules/prefill/prefill.lua b/modules/prefill/prefill.lua
index d0f2d194f92f2015055ccd7fcf05b1453b2adaae..d8f4adf5be26baab8286eccdfbb249be719bf0c7 100644 (file)
--- a/modules/prefill/prefill.lua
+++ b/modules/prefill/prefill.lua
@@ -142,10 +142,6 @@ function forward_references.fill_cache()
        restart_timer(rz_cur_interval)
 end
 
-function prefill.init()
-       math.randomseed(os.time())
-end
-
 function prefill.deinit()
        stop_timer()
 end