From 9a1843ef2df09edcc28f4f1b2ace93a39d35cc59 Mon Sep 17 00:00:00 2001
From: Valentino Geron <valentino@redislabs.com>
Date: Thu, 26 Mar 2020 11:49:21 +0200
Subject: XREAD and XREADGROUP should not be allowed from scripts when BLOCK
 option is being used

---
 src/server.c             |  4 ++--
 src/t_stream.c           |  5 +++++
 tests/unit/scripting.tcl | 11 +++++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/server.c b/src/server.c
index 84439461e..4fc7e0103 100644
--- a/src/server.c
+++ b/src/server.c
@@ -947,11 +947,11 @@ struct redisCommand redisCommandTable[] = {
      0,NULL,1,1,1,0,0,0},
 
     {"xread",xreadCommand,-4,
-     "read-only no-script @stream @blocking",
+     "read-only @stream @blocking",
      0,xreadGetKeys,1,1,1,0,0,0},
 
     {"xreadgroup",xreadCommand,-7,
-     "write no-script @stream @blocking",
+     "write @stream @blocking",
      0,xreadGetKeys,1,1,1,0,0,0},
 
     {"xgroup",xgroupCommand,-2,
diff --git a/src/t_stream.c b/src/t_stream.c
index 557d1d642..157f1eaeb 100644
--- a/src/t_stream.c
+++ b/src/t_stream.c
@@ -1373,6 +1373,11 @@ void xreadCommand(client *c) {
         int moreargs = c->argc-i-1;
         char *o = c->argv[i]->ptr;
         if (!strcasecmp(o,"BLOCK") && moreargs) {
+            if (c->flags & CLIENT_LUA) {
+                /* There is no sense to use BLOCK option within LUA */
+                addReplyErrorFormat(c, "%s command is not allowed with BLOCK option from scripts", (char *)c->argv[0]->ptr);
+                return;
+            }
             i++;
             if (getTimeoutFromObjectOrReply(c,c->argv[i],&timeout,
                 UNIT_MILLISECONDS) != C_OK) return;
diff --git a/tests/unit/scripting.tcl b/tests/unit/scripting.tcl
index fb36d0b80..8b364b287 100644
--- a/tests/unit/scripting.tcl
+++ b/tests/unit/scripting.tcl
@@ -146,6 +146,17 @@ start_server {tags {"scripting"}} {
         set e
     } {*not allowed*}
 
+    test {EVAL - Scripts can't run XREAD and XREADGROUP with BLOCK option} {
+        r del s
+        r xgroup create s g $ MKSTREAM
+        set res [r eval {return redis.pcall('xread','STREAMS','s','$')} 1 s]
+        assert {$res eq {}}
+        assert_error "*xread command is not allowed with BLOCK option from scripts" {r eval {return redis.pcall('xread','BLOCK',0,'STREAMS','s','$')} 1 s}
+        set res [r eval {return redis.pcall('xreadgroup','group','g','c','STREAMS','s','>')} 1 s]
+        assert {$res eq {}}
+        assert_error "*xreadgroup command is not allowed with BLOCK option from scripts" {r eval {return redis.pcall('xreadgroup','group','g','c','BLOCK',0,'STREAMS','s','>')} 1 s}
+    }
+
     test {EVAL - Scripts can't run certain commands} {
         set e {}
         r debug lua-always-replicate-commands 0
-- 
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