From 0a6453ffb8866e453390f7c3848c679e567b9c69 Mon Sep 17 00:00:00 2001
From: Subash <suboss87@gmail.com>
Date: Fri, 13 Mar 2026 07:58:47 +0530
Subject: [PATCH] fix(line): add request body size limit to webhook handler

Prevent unauthenticated DoS via unbounded io.ReadAll on webhook
request body. Apply the same io.LimitReader pattern used by the
WeCom channel (4 MB cap) to reject oversized POST payloads before
signature verification or JSON parsing.

Fixes #1407
---
 pkg/channels/line/line.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/pkg/channels/line/line.go b/pkg/channels/line/line.go
index b36350a06..5b1caff18 100644
--- a/pkg/channels/line/line.go
+++ b/pkg/channels/line/line.go
@@ -166,7 +166,9 @@ func (c *LINEChannel) webhookHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	body, err := io.ReadAll(r.Body)
+	// Limit request body to 4 MB to prevent memory exhaustion (DoS).
+	const maxBodySize = 4 << 20 // 4 MB
+	body, err := io.ReadAll(io.LimitReader(r.Body, maxBodySize+1))
 	if err != nil {
 		logger.ErrorCF("line", "Failed to read request body", map[string]any{
 			"error": err.Error(),
@@ -174,6 +176,10 @@ func (c *LINEChannel) webhookHandler(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "Bad request", http.StatusBadRequest)
 		return
 	}
+	if len(body) > maxBodySize {
+		http.Error(w, "Request body too large", http.StatusRequestEntityTooLarge)
+		return
+	}
 
 	signature := r.Header.Get("X-Line-Signature")
 	if !c.verifySignature(body, signature) {