From 1116d034d5354b2975a6089aad66dea00da696f3 Mon Sep 17 00:00:00 2001
From: Erik Dubbelboer <erik@dubbelboer.com>
Date: Tue, 1 Mar 2022 20:50:12 +0100
Subject: [PATCH] Fix panic while reading invalid trailers

---
 header.go    | 4 ++++
 http_test.go | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/header.go b/header.go
index e74bbc3c7f..7b9df0836f 100644
--- a/header.go
+++ b/header.go
@@ -2442,6 +2442,10 @@ func (h *RequestHeader) parseTrailer(buf []byte) (int, error) {
 }
 
 func isBadTrailer(key []byte) bool {
+	if len(key) == 0 {
+		return true
+	}
+
 	switch key[0] | 0x20 {
 	case 'a':
 		return caseInsensitiveCompare(key, strAuthorization)
diff --git a/http_test.go b/http_test.go
index 426b70a532..12ca1f1a8e 100644
--- a/http_test.go
+++ b/http_test.go
@@ -32,6 +32,9 @@ func TestInvalidTrailers(t *testing.T) {
 	if err := (&Response{}).Read(bufio.NewReader(bytes.NewReader([]byte{0x54, 0x52, 0x61, 0x49, 0x4c, 0x65, 0x52, 0x3a, 0x2c, 0x0a, 0x0a}))); !strings.Contains(err.Error(), "cannot find whitespace in the first line of response") {
 		t.Fatal(err)
 	}
+	if err := (&Request{}).Read(bufio.NewReader(bytes.NewReader([]byte{0xff, 0x20, 0x0a, 0x54, 0x52, 0x61, 0x49, 0x4c, 0x65, 0x52, 0x3a, 0x2c, 0x0a, 0x0a}))); !strings.Contains(err.Error(), "contain forbidden trailer") {
+		t.Fatal(err)
+	}
 
 	b, _ := base64.StdEncoding.DecodeString("tCAKIDoKCToKICAKCToKICAKCToKIAogOgoJOgogIAoJOgovIC8vOi4KOh0KVFJhSUxlUjo9HT09HQpUUmFJTGVSOicQAApUUmFJTGVSOj0gHSAKCT09HQoKOgoKCgo=")
 	if err := (&Request{}).Read(bufio.NewReader(bytes.NewReader(b))); !strings.Contains(err.Error(), "error when reading request headers: invalid header key") {