From 678bccd9eb7793d0c57a42cb9259f0aaef0b9484 Mon Sep 17 00:00:00 2001
From: Adam Duke <adam.v.duke@gmail.com>
Date: Mon, 16 Dec 2024 11:37:34 -0500
Subject: [PATCH 1/2] add additional buffer limit test cases

---
 buffer/buffer_test.go | 94 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 70 insertions(+), 24 deletions(-)

diff --git a/buffer/buffer_test.go b/buffer/buffer_test.go
index 4d99d13..e499d52 100644
--- a/buffer/buffer_test.go
+++ b/buffer/buffer_test.go
@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"strconv"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -173,30 +174,75 @@ func TestBuffer_requestLimitReached(t *testing.T) {
 }
 
 func TestBuffer_responseLimitReached(t *testing.T) {
-	srv := testutils.NewHandler(func(w http.ResponseWriter, _ *http.Request) {
-		_, _ = w.Write([]byte("hello, this response is too large"))
-	})
-	t.Cleanup(srv.Close)
-
-	// forwarder will proxy the request to whatever destination
-	fwd := forward.New(false)
-
-	// this is our redirect to server
-	rdr := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		req.URL = testutils.MustParseRequestURI(srv.URL)
-		fwd.ServeHTTP(w, req)
-	})
-
-	// stream handler will forward requests to redirect
-	st, err := New(rdr, MaxResponseBodyBytes(4))
-	require.NoError(t, err)
-
-	proxy := httptest.NewServer(st)
-	t.Cleanup(proxy.Close)
-
-	re, _, err := testutils.Get(proxy.URL)
-	require.NoError(t, err)
-	assert.Equal(t, http.StatusInternalServerError, re.StatusCode)
+	cases := []struct {
+		name                 string
+		body                 string
+		maxResponseBodyBytes int64
+	}{
+		{
+			name:                 "small limit with body larger than max response bytes",
+			body:                 "hello, this response is too large",
+			maxResponseBodyBytes: 4,
+		},
+		{
+			name:                 "small limit with body larger than 32768 bytes",
+			body:                 strings.Repeat("A", 32769),
+			maxResponseBodyBytes: 4,
+		},
+		{
+			name:                 "larger limit with body larger than 32768 bytes",
+			body:                 strings.Repeat("A", 32769),
+			maxResponseBodyBytes: 2000,
+		},
+		{
+			name:                 "larger limit with body larger than 32768 + 1999 bytes",
+			body:                 strings.Repeat("A", 32769+1999),
+			maxResponseBodyBytes: 2000,
+		},
+		{
+			name:                 "larger limit with body larger than 32768 + 2000 bytes",
+			body:                 strings.Repeat("A", 32769+2000),
+			maxResponseBodyBytes: 2000,
+		},
+		{
+			name:                 "larger limit with body larger than 65536 + 1999 bytes",
+			body:                 strings.Repeat("A", 65537+1999),
+			maxResponseBodyBytes: 2000,
+		},
+		{
+			name:                 "larger limit with body larger than 65536 + 2000 bytes",
+			body:                 strings.Repeat("A", 65537+2000),
+			maxResponseBodyBytes: 2000,
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			srv := testutils.NewHandler(func(w http.ResponseWriter, _ *http.Request) {
+				_, _ = w.Write([]byte(tc.body))
+			})
+			t.Cleanup(srv.Close)
+
+			// forwarder will proxy the request to whatever destination
+			fwd := forward.New(false)
+
+			// this is our redirect to server
+			rdr := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+				req.URL = testutils.MustParseRequestURI(srv.URL)
+				fwd.ServeHTTP(w, req)
+			})
+
+			// stream handler will forward requests to redirect
+			st, err := New(rdr, MaxResponseBodyBytes(tc.maxResponseBodyBytes))
+			require.NoError(t, err)
+
+			proxy := httptest.NewServer(st)
+			t.Cleanup(proxy.Close)
+
+			re, _, err := testutils.Get(proxy.URL)
+			require.NoError(t, err)
+			assert.Equal(t, http.StatusInternalServerError, re.StatusCode)
+		})
+	}
 }
 
 func TestBuffer_fileStreamingResponse(t *testing.T) {

From dfdf4a44a984076ae8f1b04c7910baedfcfe14dc Mon Sep 17 00:00:00 2001
From: Adam Duke <adam.v.duke@gmail.com>
Date: Sun, 29 Dec 2024 21:08:34 -0500
Subject: [PATCH 2/2] propagate underlying buffer write errors

---
 buffer/buffer.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/buffer/buffer.go b/buffer/buffer.go
index 4c52822..694ecc1 100644
--- a/buffer/buffer.go
+++ b/buffer/buffer.go
@@ -189,6 +189,12 @@ func (b *Buffer) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 			return
 		}
 
+		if bw.writeError != nil {
+			b.log.Error("vulcand/oxy/buffer: failed to copy response, err: %v", bw.writeError)
+			b.errHandler.ServeHTTP(w, req, bw.writeError)
+			return
+		}
+
 		var reader multibuf.MultiReader
 		if bw.expectBody(outReq) {
 			rdr, err := writer.Reader()
@@ -258,6 +264,7 @@ type bufferWriter struct {
 	buffer         multibuf.WriterOnce
 	responseWriter http.ResponseWriter
 	hijacked       bool
+	writeError     error
 	log            utils.Logger
 }
 
@@ -298,6 +305,7 @@ func (b *bufferWriter) Write(buf []byte) (int, error) {
 		// if the writer returns an error, the reverse proxy panics
 		b.log.Error("write: %v", err)
 		length = len(buf)
+		b.writeError = err
 	}
 	return length, nil
 }