From 052b08160ad68c71763c0aea87c9acf55ca76de6 Mon Sep 17 00:00:00 2001
From: "mergify[bot]" <37929162+mergify[bot]@users.noreply.github.com>
Date: Tue, 9 Nov 2021 19:53:44 +0100
Subject: [PATCH] Set a cap on the length of subscription queries. (backport
 #7263) (#7264)

As a safety measure, don't allow a query string to be unreasonably
long. The query filter is not especially efficient, so a query that
needs more than basic detail should filter coarsely in the subscriber
and refine on the client side.

This affects Subscribe and TxSearch queries.

(cherry picked from commit 9dc3d7f9a26f2e395311b2f1d705aa950bb25c7a)
---
 internal/rpc/core/events.go | 7 +++++++
 internal/rpc/core/tx.go     | 2 ++
 2 files changed, 9 insertions(+)

diff --git a/internal/rpc/core/events.go b/internal/rpc/core/events.go
index 8632e00c1..46d9ff6a7 100644
--- a/internal/rpc/core/events.go
+++ b/internal/rpc/core/events.go
@@ -2,6 +2,7 @@ package core
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"time"
 
@@ -14,6 +15,10 @@ import (
 const (
 	// Buffer on the Tendermint (server) side to allow some slowness in clients.
 	subBufferSize = 100
+
+	// maxQueryLength is the maximum length of a query string that will be
+	// accepted. This is just a safety check to avoid outlandish queries.
+	maxQueryLength = 512
 )
 
 // Subscribe for events via WebSocket.
@@ -25,6 +30,8 @@ func (env *Environment) Subscribe(ctx *rpctypes.Context, query string) (*coretyp
 		return nil, fmt.Errorf("max_subscription_clients %d reached", env.Config.MaxSubscriptionClients)
 	} else if env.EventBus.NumClientSubscriptions(addr) >= env.Config.MaxSubscriptionsPerClient {
 		return nil, fmt.Errorf("max_subscriptions_per_client %d reached", env.Config.MaxSubscriptionsPerClient)
+	} else if len(query) > maxQueryLength {
+		return nil, errors.New("maximum query length exceeded")
 	}
 
 	env.Logger.Info("Subscribe to query", "remote", addr, "query", query)
diff --git a/internal/rpc/core/tx.go b/internal/rpc/core/tx.go
index 60c7519c0..7ba2bf90c 100644
--- a/internal/rpc/core/tx.go
+++ b/internal/rpc/core/tx.go
@@ -72,6 +72,8 @@ func (env *Environment) TxSearch(
 
 	if !indexer.KVSinkEnabled(env.EventSinks) {
 		return nil, fmt.Errorf("transaction searching is disabled due to no kvEventSink")
+	} else if len(query) > maxQueryLength {
+		return nil, errors.New("maximum query length exceeded")
 	}
 
 	q, err := tmquery.New(query)