From 1f3b349ea2df4cd4540ed78d46c9527d454a351e Mon Sep 17 00:00:00 2001
From: Juliusz Chroboczek <jch@irif.fr>
Date: Sat, 9 Dec 2023 15:51:35 +0100
Subject: [PATCH] Use MaxBytesReader in whip.

---
 webserver/webserver.go | 10 ++++++++--
 webserver/whip.go      | 17 ++++-------------
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/webserver/webserver.go b/webserver/webserver.go
index ec9518b..4d869c7 100644
--- a/webserver/webserver.go
+++ b/webserver/webserver.go
@@ -133,11 +133,17 @@ func httpError(w http.ResponseWriter, err error) {
 		return
 	}
 	if os.IsPermission(err) {
-		http.Error(w, "403 forbidden", http.StatusForbidden)
+		http.Error(w, "Forbidden", http.StatusForbidden)
+		return
+	}
+	var mberr *http.MaxBytesError
+	if errors.As(err, &mberr) {
+		http.Error(w, "Request body too large",
+			http.StatusRequestEntityTooLarge)
 		return
 	}
 	log.Printf("HTTP server error: %v", err)
-	http.Error(w, "500 Internal Server Error",
+	http.Error(w, "Internal server error",
 		http.StatusInternalServerError)
 }
 
diff --git a/webserver/whip.go b/webserver/whip.go
index aaac79d..7f833f1 100644
--- a/webserver/whip.go
+++ b/webserver/whip.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	crand "crypto/rand"
 	"encoding/base64"
-	"errors"
 	"fmt"
 	"io"
 	"log"
@@ -44,16 +43,6 @@ func newId() string {
 	return base64.RawURLEncoding.EncodeToString(b)
 }
 
-const sdpLimit = 1024 * 1024
-
-func readLimited(r io.Reader) ([]byte, error) {
-	v, err := io.ReadAll(io.LimitReader(r, sdpLimit))
-	if len(v) == sdpLimit {
-		err = errors.New("SDP too large")
-	}
-	return v, err
-}
-
 func canPresent(perms []string) bool {
 	for _, p := range perms {
 		if p == "present" {
@@ -119,6 +108,8 @@ func whipICEServers(w http.ResponseWriter) {
 	}
 }
 
+const sdpLimit = 1024 * 1024
+
 func whipEndpointHandler(w http.ResponseWriter, r *http.Request) {
 	if redirect(w, r) {
 		return
@@ -181,7 +172,7 @@ func whipEndpointHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	body, err := readLimited(r.Body)
+	body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, sdpLimit))
 	if err != nil {
 		httpError(w, err)
 		return
@@ -311,7 +302,7 @@ func whipResourceHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	body, err := readLimited(r.Body)
+	body, err := io.ReadAll(http.MaxBytesReader(w, r.Body, sdpLimit))
 	if err != nil {
 		httpError(w, err)
 		return