diff --git a/redis.conf b/redis.conf index 1b79e09e..d2eae1af 100644 --- a/redis.conf +++ b/redis.conf @@ -392,6 +392,23 @@ auto-aof-rewrite-min-size 64mb # Set it to 0 or a negative value for unlimited execution without warnings. lua-time-limit 5000 +# By default variables in a Lua script are global, this means that a correct +# script must declare all the local variables explicitly using the 'local' +# keyword. Lua beginners are known to violate this rule, polluting the global +# namespace, or creating scripts that may fail under certain conditions, for +# this reason by default Redis installs a protection that will raise an error +# every time a script attempts to access a global variable that was not +# explicitly declared via global(). +# +# It's worth to note that normal Redis scripts should never use globals, but +# we don't entirely disable the possibility because from time to time crazy +# things in the right hands can be pretty powerful. +# +# Globals protection may result into a minor performance hint, so it is +# possible to disable the feature in production environments using the +# following configuration directive, or at runtime using CONFIG SET. +lua-protect-globals yes + ################################ REDIS CLUSTER ############################### # # Normal Redis instances can't be part of a Redis Cluster, only nodes that are diff --git a/src/config.c b/src/config.c index 8dffe288..5aa807f2 100644 --- a/src/config.c +++ b/src/config.c @@ -311,6 +311,10 @@ void loadServerConfigFromString(char *config) { server.cluster.configfile = zstrdup(argv[1]); } else if (!strcasecmp(argv[0],"lua-time-limit") && argc == 2) { server.lua_time_limit = strtoll(argv[1],NULL,10); + } else if (!strcasecmp(argv[0],"lua-protect-globals") && argc == 2) { + if ((server.lua_protect_globals = yesnotoi(argv[1])) == -1) { + err = "argument must be 'yes' or 'no'"; goto loaderr; + } } else if (!strcasecmp(argv[0],"slowlog-log-slower-than") && argc == 2) { @@ -552,6 +556,16 @@ void configSetCommand(redisClient *c) { } else if (!strcasecmp(c->argv[2]->ptr,"lua-time-limit")) { if (getLongLongFromObject(o,&ll) == REDIS_ERR || ll < 0) goto badfmt; server.lua_time_limit = ll; + } else if (!strcasecmp(c->argv[2]->ptr,"lua-protect-globals")) { + int enable = yesnotoi(o->ptr); + + if (enable == -1) goto badfmt; + if (enable == 0 && server.lua_protect_globals == 1) { + scriptingDisableGlobalsProtection(server.lua); + } else if (enable && server.lua_protect_globals == 0) { + scriptingEnableGlobalsProtection(server.lua); + } + server.lua_protect_globals = enable; } else if (!strcasecmp(c->argv[2]->ptr,"slowlog-log-slower-than")) { if (getLongLongFromObject(o,&ll) == REDIS_ERR) goto badfmt; server.slowlog_log_slower_than = ll; @@ -735,6 +749,7 @@ void configGetCommand(redisClient *c) { config_get_bool_field("daemonize", server.daemonize); config_get_bool_field("rdbcompression", server.rdb_compression); config_get_bool_field("activerehashing", server.activerehashing); + config_get_bool_field("lua-protect-globals", server.lua_protect_globals); /* Everything we can't handle with macros follows. */ diff --git a/src/redis.c b/src/redis.c index 7ddeb886..089251b6 100644 --- a/src/redis.c +++ b/src/redis.c @@ -1068,6 +1068,7 @@ void initServerConfig() { server.lua_time_limit = REDIS_LUA_TIME_LIMIT; server.lua_client = NULL; server.lua_timedout = 0; + server.lua_protect_globals = 1; updateLRUClock(); resetServerSaveParams(); diff --git a/src/redis.h b/src/redis.h index 5a3d1a9c..bd4ef5a1 100644 --- a/src/redis.h +++ b/src/redis.h @@ -717,6 +717,7 @@ struct redisServer { int lua_timedout; /* True if we reached the time limit for script execution. */ int lua_kill; /* Kill the script if true. */ + int lua_protect_globals; /* If true globals must be declared */ /* Assert & bug reportign */ char *assert_failed; char *assert_file; @@ -1102,6 +1103,8 @@ void clusterPropagatePublish(robj *channel, robj *message); /* Scripting */ void scriptingInit(void); +void scriptingEnableGlobalsProtection(lua_State *lua); +void scriptingDisableGlobalsProtection(lua_State *lua); /* Git SHA1 */ char *redisGitSHA1(void); diff --git a/src/scripting.c b/src/scripting.c index 03938edd..138437cf 100644 --- a/src/scripting.c +++ b/src/scripting.c @@ -412,45 +412,57 @@ void luaLoadLibraries(lua_State *lua) { #endif } -void scriptingProtectGlobals(lua_State *lua) { - char *s[26]; +/* This function installs metamethods in the global table _G that prevent + * the creation of globals accidentally. + * + * It should be the last to be called in the scripting engine initialization + * sequence, because it may interact with creation of globals. + * Note that the function is designed to be called multiple times if needed + * without issues, because it is possible to enabled/disable globals protection + * at runtime with CONFIG SET. */ +void scriptingEnableGlobalsProtection(lua_State *lua) { + char *s[32]; sds code = sdsempty(); - int j; + int j = 0; - /* strict.lua from: http://metalua.luaforge.net/src/lib/strict.lua.html */ - s[0]="local mt = getmetatable(_G)\n"; - s[1]="if mt == nil then\n"; - s[2]=" mt = {}\n"; - s[3]=" setmetatable(_G, mt)\n"; - s[4]="end\n"; - s[5]="__STRICT = true\n"; - s[6]="mt.__declared = {}\n"; - s[7]="mt.__newindex = function (t, n, v)\n"; - s[8]=" if __STRICT and not mt.__declared[n] and debug.getinfo(2) then\n"; - s[9]=" local w = debug.getinfo(2, \"S\").what\n"; - s[10]=" if w ~= \"main\" and w ~= \"C\" then\n"; - s[11]=" error(\"assign to undeclared global var '\"..n..\"'\", 2)\n"; - s[12]=" end\n"; - s[13]=" mt.__declared[n] = true\n"; - s[14]=" end\n"; - s[15]=" rawset(t, n, v)\n"; - s[16]="end\n"; - s[17]="mt.__index = function (t, n)\n"; - s[18]=" if debug.getinfo(2) and not mt.__declared[n] and debug.getinfo(2, \"S\").what ~= \"C\" then\n"; - s[19]=" error(\"global var '\"..n..\"' is not declared\", 2)\n"; - s[20]=" end\n"; - s[21]=" return rawget(t, n)\n"; - s[22]="end\n"; - s[23]="function global(...)\n"; - s[24]=" for _, v in ipairs{...} do mt.__declared[v] = true end\n"; - s[25]="end\n"; + /* strict.lua from: http://metalua.luaforge.net/src/lib/strict.lua.html. + * Modified to be adapted to Redis. */ + s[j++]="mt = {}\n"; + s[j++]="setmetatable(_G, mt)\n"; + s[j++]="mt.declared = {}\n"; + s[j++]="mt.__newindex = function (t, n, v)\n"; + s[j++]=" if not mt.declared[n] and debug.getinfo(2) then\n"; + s[j++]=" local w = debug.getinfo(2, \"S\").what\n"; + s[j++]=" if w ~= \"main\" and w ~= \"C\" then\n"; + s[j++]=" error(\"assignment to undeclared global variable '\"..n..\"'\", 2)\n"; + s[j++]=" end\n"; + s[j++]=" mt.declared[n] = true\n"; + s[j++]=" end\n"; + s[j++]=" rawset(t, n, v)\n"; + s[j++]="end\n"; + s[j++]="mt.__index = function (t, n)\n"; + s[j++]=" if debug.getinfo(2) and not mt.declared[n] and debug.getinfo(2, \"S\").what ~= \"C\" then\n"; + s[j++]=" error(\"global variable '\"..n..\"' is not declared\", 2)\n"; + s[j++]=" end\n"; + s[j++]=" return rawget(t, n)\n"; + s[j++]="end\n"; + s[j++]="function global(...)\n"; + s[j++]=" for _, v in ipairs{...} do mt.declared[v] = true end\n"; + s[j++]="end\n"; + s[j++]=NULL; - for (j = 0; j < 26; j++) code = sdscatlen(code,s[j],strlen(s[j])); - luaL_loadbuffer(lua,code,sdslen(code),"strict_lua"); + for (j = 0; s[j] != NULL; j++) code = sdscatlen(code,s[j],strlen(s[j])); + luaL_loadbuffer(lua,code,sdslen(code),"enable_strict_lua"); lua_pcall(lua,0,0,0); sdsfree(code); } +void scriptingDisableGlobalsProtection(lua_State *lua) { + char *s = "setmetatable(_G, nil)\n"; + luaL_loadbuffer(lua,s,strlen(s),"disable_strict_lua"); + lua_pcall(lua,0,0,0); +} + /* Initialize the scripting environment. * It is possible to call this function to reset the scripting environment * assuming that we call scriptingRelease() before. @@ -543,7 +555,8 @@ void scriptingInit(void) { /* Lua beginners ofter don't use "local", this is likely to introduce * subtle bugs in their code. To prevent problems we protect accesses * to global variables. */ - scriptingProtectGlobals(lua); + if (server.lua_protect_globals) + scriptingEnableGlobalsProtection(lua); server.lua = lua; }