0880e6ac

feat: decompress gzip responses in middleware save

a73x 2026-03-31 12:44

Commit message

feat: decompress gzip responses in middleware save

SaveResponse now checks Content-Encoding and decompresses gzip
bodies before writing to disk.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

middleware/middleware.go

Old		New
@@ -1,7 +1,10 @@
1	package middleware	1	package middleware
2		2
3	import (	3	import (
		4	"bytes"
		5	"compress/gzip"
4	"fmt"	6	"fmt"
		7	"io"
5	"os"	8	"os"
6		9
7	"gopkg.in/yaml.v3"	10	"gopkg.in/yaml.v3"
@@ -71,7 +74,19 @@ func (m Middleware) Match(host, path string) Rule {
71	}	74	}
72		75
73	// SaveResponse writes the response body to the rule's destination file,	76	// SaveResponse writes the response body to the rule's destination file,
74	// overwriting any existing content.	77	// overwriting any existing content. If contentEncoding is "gzip", the
75	func (r *Rule) SaveResponse(body []byte) error {	78	// body is decompressed before writing.
		79	func (r *Rule) SaveResponse(body []byte, contentEncoding string) error {
		80	if contentEncoding == "gzip" {
		81	gr, err := gzip.NewReader(bytes.NewReader(body))
		82	if err != nil {
		83	return fmt.Errorf("decompressing gzip response: %w", err)
		84	}
		85	defer gr.Close()
		86	body, err = io.ReadAll(gr)
		87	if err != nil {
		88	return fmt.Errorf("reading decompressed response: %w", err)
		89	}
		90	}
76	return os.WriteFile(r.Dest, body, 0644)	91	return os.WriteFile(r.Dest, body, 0644)
77	}	92	}

middleware/middleware_test.go

Old		New
@@ -1,6 +1,8 @@
1	package middleware_test	1	package middleware_test
2		2
3	import (	3	import (
		4	"bytes"
		5	"compress/gzip"
4	"os"	6	"os"
5	"path/filepath"	7	"path/filepath"
6	"testing"	8	"testing"
@@ -95,7 +97,7 @@ func TestSaveResponseWritesBodyToFile(t *testing.T) {
95	}	97	}
96		98
97	body := []byte(`{"tokens": 42}`)	99	body := []byte(`{"tokens": 42}`)
98	err := rule.SaveResponse(body)	100	err := rule.SaveResponse(body, "")
99	if err != nil {	101	if err != nil {
100	t.Fatalf("unexpected error: %v", err)	102	t.Fatalf("unexpected error: %v", err)
101	}	103	}
@@ -120,10 +122,35 @@ func TestSaveResponseOverwritesExistingFile(t *testing.T) {
120	}	122	}
121		123
122	body := []byte(`{"new": true}`)	124	body := []byte(`{"new": true}`)
123	rule.SaveResponse(body)	125	rule.SaveResponse(body, "")
124		126
125	got, _ := os.ReadFile(dest)	127	got, _ := os.ReadFile(dest)
126	if string(got) != string(body) {	128	if string(got) != string(body) {
127	t.Errorf("expected %q, got %q", body, got)	129	t.Errorf("expected %q, got %q", body, got)
128	}	130	}
129	}	131	}
		132
		133	func TestSaveResponseDecompressesGzip(t *testing.T) {
		134	dest := filepath.Join(t.TempDir(), "out.json")
		135	rule := &middleware.Rule{
		136	Match: "example.com/data",
		137	Action: "save_response",
		138	Dest: dest,
		139	}
		140
		141	original := `{"tokens": 42}`
		142	var buf bytes.Buffer
		143	gw := gzip.NewWriter(&buf)
		144	gw.Write([]byte(original))
		145	gw.Close()
		146
		147	err := rule.SaveResponse(buf.Bytes(), "gzip")
		148	if err != nil {
		149	t.Fatalf("unexpected error: %v", err)
		150	}
		151
		152	got, _ := os.ReadFile(dest)
		153	if string(got) != original {
		154	t.Errorf("expected %q, got %q", original, got)
		155	}
		156	}

proxy/proxy.go

Old		New
@@ -254,7 +254,7 @@ func (p Proxy) handleConnectMITM(w http.ResponseWriter, r http.Request) {
254	log.Printf("ERROR: middleware failed to read response body from %s: %v", host, err)	254	log.Printf("ERROR: middleware failed to read response body from %s: %v", host, err)
255	upstreamResp.Body = io.NopCloser(bytes.NewReader(nil))	255	upstreamResp.Body = io.NopCloser(bytes.NewReader(nil))
256	} else {	256	} else {
257	if err := rule.SaveResponse(body); err != nil {	257	if err := rule.SaveResponse(body, upstreamResp.Header.Get("Content-Encoding")); err != nil {
258	log.Printf("ERROR: middleware failed to save response to %s: %v", rule.Dest, err)	258	log.Printf("ERROR: middleware failed to save response to %s: %v", rule.Dest, err)
259	} else {	259	} else {
260	log.Printf("MIDDLEWARE saved %s%s -> %s", host, req.URL.Path, rule.Dest)	260	log.Printf("MIDDLEWARE saved %s%s -> %s", host, req.URL.Path, rule.Dest)