EVALSHA_RO and EVAL_RO Commands (#8820)

* EVALSHA_RO and EVAL_RO Commands

Added new readonly versions of EVAL
and EVALSHA.

src/scripting.c

@@ -603,6 +603,15 @@ int luaRedisGenericCommand(lua_State *lua, int raise_error) {
         goto cleanup;
     }
 
+    /* This check is for EVAL_RO, EVALSHA_RO. We want to allow only read only commands */
+    if ((server.lua_caller->cmd->proc == evalRoCommand ||
+         server.lua_caller->cmd->proc == evalShaRoCommand) &&
+         (cmd->flags & CMD_WRITE))
+    {
+        luaPushError(lua, "Write commands are not allowed from read-only scripts");
+        goto cleanup;
+    }
+
     /* Check the ACLs. */
     int acl_errpos;
     int acl_retval = ACLCheckAllPerm(c,&acl_errpos);
@@ -1696,6 +1705,10 @@ void evalCommand(client *c) {
         evalGenericCommandWithDebugging(c,0);
 }
 
+void evalRoCommand(client *c) {
+    evalCommand(c);
+}
+
 void evalShaCommand(client *c) {
     if (sdslen(c->argv[1]->ptr) != 40) {
         /* We know that a match is not possible if the provided SHA is
@@ -1713,6 +1726,10 @@ void evalShaCommand(client *c) {
     }
 }
 
+void evalShaRoCommand(client *c) {
+    evalShaCommand(c);
+}
+
 void scriptCommand(client *c) {
     if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"help")) {
         const char *help[] = {

src/server.c

@@ -910,10 +910,18 @@ struct redisCommand redisCommandTable[] = {
      "no-script may-replicate @scripting",
      0,evalGetKeys,0,0,0,0,0,0},
 
+    {"eval_ro",evalRoCommand,-3,
+     "no-script @scripting",
+     0,evalGetKeys,0,0,0,0,0,0},
+
     {"evalsha",evalShaCommand,-3,
      "no-script may-replicate @scripting",
      0,evalGetKeys,0,0,0,0,0,0},
 
+    {"evalsha_ro",evalShaRoCommand,-3,
+     "no-script @scripting",
+     0,evalGetKeys,0,0,0,0,0,0},
+
     {"slowlog",slowlogCommand,-2,
      "admin random ok-loading ok-stale",
      0,NULL,0,0,0,0,0,0},

src/server.h

@@ -2644,7 +2644,9 @@ void memoryCommand(client *c);
 void clientCommand(client *c);
 void helloCommand(client *c);
 void evalCommand(client *c);
+void evalRoCommand(client *c);
 void evalShaCommand(client *c);
+void evalShaRoCommand(client *c);
 void scriptCommand(client *c);
 void timeCommand(client *c);
 void bitopCommand(client *c);

tests/unit/scripting.tcl

@@ -320,6 +320,17 @@ start_server {tags {"scripting"}} {
         r eval {return 'hello' --trailing comment} 0
     } {hello}
 
+    test {EVAL_RO - Successful case} {
+        r set foo bar
+        assert_equal bar [r eval_ro {return redis.call('get', KEYS[1]);} 1 foo]
+    }
+
+    test {EVAL_RO - Cannot run write commands} {
+        r set foo bar
+        catch {r eval_ro {redis.call('del', KEYS[1]);} 1 foo} e
+        set e
+    } {*Write commands are not allowed from read-only scripts*}
+
     test {SCRIPTING FLUSH - is able to clear the scripts cache?} {
         r set mykey myval
         set v [r evalsha fd758d1589d044dd850a6f05d52f2eefd27f033f 1 mykey]