File bsc1198952-2.patch of Package redis.26568
From 21414ad4802659eeb3e81d20d86b437d3ab882dc Mon Sep 17 00:00:00 2001
From: meir <meir@redis.com>
Date: Tue, 22 Mar 2022 11:42:48 +0200
Subject: [PATCH] Move user eval function to be located on Lua registry. Today,
Redis wrap the user Lua code with a Lua function. For example, assuming the
user code is:
```
return redis.call('ping')
```
The actual code that would have sent to the Lua interpreter was:
```
f_b3a02c833904802db9c34a3cf1292eee3246df3c() return redis.call('ping') end
```
The wraped code would have been saved on the global dictionary with the
following name: `f_<script sha>` (in our example `f_b3a02c833904802db9c34a3cf1292eee3246df3c`).
This approach allows one user to easily override the implementation a another user code, example:
```
f_b3a02c833904802db9c34a3cf1292eee3246df3c = function() return 'hacked' end
```
Running the above code will cause `evalsha b3a02c833904802db9c34a3cf1292eee3246df3c 0` to return
hacked although it should have returned `pong`.
Another disadventage is that Redis basically runs code on the loading (compiling) phase without been
aware of it. User can do code injection like this:
```
return 1 end <run code on compling phase> function() return 1
```
The wraped code will look like this and the entire `<run code on compling phase>` block will run outside
of eval or evalsha context:
```
f_<sha>() return 1 end <run code on compling phase> function() return 1 end
```
---
src/scripting.c | 29 +++++++----------------------
1 file changed, 7 insertions(+), 22 deletions(-)
diff --git a/src/scripting.c b/src/scripting.c
index ccd78a8bfa9a..cc3924c7a45e 100644
--- a/src/scripting.c
+++ b/src/scripting.c
@@ -1104,7 +1104,7 @@ void scriptingEnableGlobalsProtection(lua_State *lua) {
s[j++]="mt.__newindex = function (t, n, v)\n";
s[j++]=" if dbg.getinfo(2) then\n";
s[j++]=" local w = dbg.getinfo(2, \"S\").what\n";
- s[j++]=" if w ~= \"main\" and w ~= \"C\" then\n";
+ s[j++]=" if w ~= \"C\" then\n";
s[j++]=" error(\"Script attempted to create global variable '\"..tostring(n)..\"'\", 2)\n";
s[j++]=" end\n";
s[j++]=" end\n";
@@ -1423,14 +1423,7 @@ sds luaCreateFunction(client *c, lua_State *lua, robj *body) {
return dictGetKey(de);
}
- sds funcdef = sdsempty();
- funcdef = sdscat(funcdef,"function ");
- funcdef = sdscatlen(funcdef,funcname,42);
- funcdef = sdscatlen(funcdef,"() ",3);
- funcdef = sdscatlen(funcdef,body->ptr,sdslen(body->ptr));
- funcdef = sdscatlen(funcdef,"\nend",4);
-
- if (luaL_loadbuffer(lua,funcdef,sdslen(funcdef),"@user_script")) {
+ if (luaL_loadbuffer(lua,body->ptr,sdslen(body->ptr),"@user_script")) {
if (c != NULL) {
addReplyErrorFormat(c,
"Error compiling script (new function): %s\n",
@@ -1438,20 +1431,12 @@ sds luaCreateFunction(client *c, lua_State *lua, robj *body) {
}
lua_pop(lua,1);
sdsfree(sha);
- sdsfree(funcdef);
return NULL;
}
- sdsfree(funcdef);
- if (lua_pcall(lua,0,0,0)) {
- if (c != NULL) {
- addReplyErrorFormat(c,"Error running script (new function): %s\n",
- lua_tostring(lua,-1));
- }
- lua_pop(lua,1);
- sdsfree(sha);
- return NULL;
- }
+ serverAssert(lua_isfunction(lua, -1));
+
+ lua_setfield(lua, LUA_REGISTRYINDEX, funcname);
/* We also save a SHA1 -> Original script map in a dictionary
* so that we can replicate / write in the AOF all the
@@ -1579,7 +1564,7 @@ void evalGenericCommand(client *c, int evalsha) {
lua_getglobal(lua, "__redis__err__handler");
/* Try to lookup the Lua function */
- lua_getglobal(lua, funcname);
+ lua_getfield(lua, LUA_REGISTRYINDEX, funcname);
if (lua_isnil(lua,-1)) {
lua_pop(lua,1); /* remove the nil from the stack */
/* Function not defined... let's define it if we have the
@@ -1597,7 +1582,7 @@ void evalGenericCommand(client *c, int evalsha) {
return;
}
/* Now the following is guaranteed to return non nil */
- lua_getglobal(lua, funcname);
+ lua_getfield(lua, LUA_REGISTRYINDEX, funcname);
serverAssert(!lua_isnil(lua,-1));
}
