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e0cd433485
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e0cd433485 | ||
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| 449b28f8a1 |
109
packages/secubox-toolbox-ng/cmd/sbxmitm/gzip.go
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109
packages/secubox-toolbox-ng/cmd/sbxmitm/gzip.go
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@ -0,0 +1,109 @@
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// SPDX-License-Identifier: LicenseRef-CMSD-1.0
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// Copyright (c) 2026 CyberMind — Gérald Kerma <devel@cybermind.fr>
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//
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// SecuBox-Deb :: toolbox-ng :: gzip-aware banner injection (#662)
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//
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// The transparency-banner inject (injectLoader) scans the HTML body for
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// <head>/<body>. Browsers send `Accept-Encoding: gzip, br`, so most upstream
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// responses come back COMPRESSED — and a compressed body has no plaintext
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// <head>/<body> for injectLoader to find, so it silently no-ops (the banner
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// vanished on every gzip page). mitmPipeline now pins the upstream request to
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// `Accept-Encoding: gzip` (dropping br/zstd/deflate we cannot decode with the
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// stdlib), so every response is either gzip or identity.
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//
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// This file holds the gzip helpers + the single inject-path transform that
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// decompresses (if gzip) → injectLoader → recompresses, fail-open on any error
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// so a banner asset never breaks the page.
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//
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// Pure standard library — compress/gzip only; no external modules (brotli/zstd
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// are NOT in the stdlib, which is exactly why we constrain the wire to gzip).
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package main
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import (
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"bytes"
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"compress/gzip"
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"io"
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"strings"
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)
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// gunzipCap bounds the decompressed output so a maliciously-crafted gzip body
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// (a "decompression bomb") cannot blow the worker's memory. The upstream body
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// itself is already read under an 8MiB LimitReader; 32MiB of inflated HTML is a
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// generous ceiling for a single page. Exceeding it → treated as an error
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// (caller fails open and serves the original compressed bytes).
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const gunzipCap = 32 << 20
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// gunzipBytes inflates a gzip-compressed body. It is defensive on two axes:
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// - a malformed/non-gzip input returns an error (caller fails open),
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// - the decompressed output is capped at gunzipCap; if the stream would
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// exceed it, that is reported as an error too (decompression-bomb guard).
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func gunzipBytes(in []byte) ([]byte, error) {
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zr, err := gzip.NewReader(bytes.NewReader(in))
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if err != nil {
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return nil, err
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}
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defer zr.Close()
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// Read up to gunzipCap+1 so we can tell "exactly at the cap" (fine) from
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// "the stream is bigger than the cap" (bomb → error).
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out, err := io.ReadAll(io.LimitReader(zr, gunzipCap+1))
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if err != nil {
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return nil, err
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}
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if len(out) > gunzipCap {
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return nil, errGunzipTooLarge
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}
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return out, nil
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}
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// errGunzipTooLarge is returned by gunzipBytes when the decompressed stream
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// exceeds gunzipCap (decompression-bomb guard).
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var errGunzipTooLarge = errString("gunzip output exceeds cap")
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// errString is a tiny stdlib-only error type (avoids importing errors/fmt for
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// one sentinel).
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type errString string
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func (e errString) Error() string { return string(e) }
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// gzipBytes compresses in with the default gzip level. It never errors: the
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// gzip.Writer only writes into an in-memory bytes.Buffer, which cannot fail.
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func gzipBytes(in []byte) []byte {
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var buf bytes.Buffer
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zw := gzip.NewWriter(&buf)
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_, _ = zw.Write(in)
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_ = zw.Close()
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return buf.Bytes()
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}
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// injectIntoBody runs the transparency-banner injection over a (possibly
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// gzip-compressed) HTML body, returning the new body bytes to serve and whether
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// the body was rewritten.
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//
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// - encoding == "" (identity): injectLoader runs directly on body; the result
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// is returned (ok=true). The caller MUST update Content-Length to len(out).
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// - encoding == "gzip" (case-insensitive): the body is gunzipped, injected,
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// then RE-gzipped so the client transfer stays compressed (the tunnel is
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// perf-sensitive). The caller keeps Content-Encoding: gzip and sets
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// Content-Length to len(out).
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// - any other encoding (br/zstd/deflate — should not occur after the upstream
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// Accept-Encoding pin, but be safe): pass through untouched, ok=false.
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//
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// Fail-open: if gunzip fails (corrupt / not-actually-gzip / bomb), the ORIGINAL
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// bytes are returned with ok=false so the page is never broken.
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//
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// idempotency / placement live entirely inside injectLoader (unchanged).
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func injectIntoBody(body []byte, encoding, clientHash string, wg bool) (out []byte, ok bool) {
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switch strings.ToLower(strings.TrimSpace(encoding)) {
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case "":
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return injectLoader(body, clientHash, wg), true
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case "gzip":
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plain, err := gunzipBytes(body)
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if err != nil {
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return body, false // fail open: serve the original compressed bytes
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}
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injected := injectLoader(plain, clientHash, wg)
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return gzipBytes(injected), true
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default:
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return body, false // unknown encoding we cannot decode → pass through
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}
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}
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152
packages/secubox-toolbox-ng/cmd/sbxmitm/gzip_test.go
Normal file
152
packages/secubox-toolbox-ng/cmd/sbxmitm/gzip_test.go
Normal file
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@ -0,0 +1,152 @@
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// SPDX-License-Identifier: LicenseRef-CMSD-1.0
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// Copyright (c) 2026 CyberMind — Gérald Kerma <devel@cybermind.fr>
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//
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// SecuBox-Deb :: toolbox-ng :: gzip-aware banner injection tests (#662)
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//
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// Covers the LIVE bug: the banner only injected into UNCOMPRESSED HTML, so
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// gzip pages (the common case — browsers send Accept-Encoding: gzip,br) lost
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// the banner. These tests pin the decompress→inject→recompress transform and
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// its fail-open behaviour.
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package main
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import (
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"bytes"
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"strings"
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"testing"
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)
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func TestGzipRoundTrip(t *testing.T) {
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cases := [][]byte{
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[]byte(""),
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[]byte("hello world"),
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[]byte(`<html><head><title>x</title></head><body>hi</body></html>`),
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bytes.Repeat([]byte("AB"), 100000), // larger, compressible payload
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}
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for _, x := range cases {
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got, err := gunzipBytes(gzipBytes(x))
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if err != nil {
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t.Fatalf("gunzipBytes(gzipBytes(%d bytes)) errored: %v", len(x), err)
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}
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if !bytes.Equal(got, x) {
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t.Fatalf("round-trip mismatch: got %d bytes, want %d bytes", len(got), len(x))
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}
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}
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}
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func TestGunzipNonGzipFails(t *testing.T) {
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// Plain bytes that are not a gzip stream → error, no panic.
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if _, err := gunzipBytes([]byte("this is definitely not gzip")); err == nil {
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t.Fatal("gunzipBytes on non-gzip input must error")
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}
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}
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func TestInjectIntoBodyGzip(t *testing.T) {
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// End-to-end-ish: HTML with <head>, gzipped, run through the exact transform
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// the inject path uses. Result must gunzip back to an injected, intact doc.
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html := `<html><head><title>page</title></head><body>content</body></html>`
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out, ok := injectIntoBody(gzipBytes([]byte(html)), "gzip", "abc123", true)
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if !ok {
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t.Fatal("gzip inject must report ok=true")
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}
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plain, err := gunzipBytes(out)
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if err != nil {
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t.Fatalf("re-gzipped output must gunzip cleanly: %v", err)
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}
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s := string(plain)
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if !strings.Contains(s, bannerGuard) {
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t.Fatalf("banner guard %q absent after gzip inject:\n%s", bannerGuard, s)
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}
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// Document otherwise intact: original head/body content preserved.
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if !strings.Contains(s, "<title>page</title>") || !strings.Contains(s, "<body>content</body>") {
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t.Fatalf("original document content displaced:\n%s", s)
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}
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// The loader tag landed inside <head>.
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if !strings.Contains(s, `<head><!-- `+bannerGuard) {
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t.Fatalf("loader tag not inserted right after <head>:\n%s", s)
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}
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}
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func TestInjectIntoBodyGzipCaseInsensitiveEncoding(t *testing.T) {
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html := `<head></head>`
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out, ok := injectIntoBody(gzipBytes([]byte(html)), "GZIP", "z", false)
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if !ok {
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t.Fatal("Content-Encoding GZIP (upper) must be recognised → ok=true")
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}
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plain, err := gunzipBytes(out)
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if err != nil {
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t.Fatalf("gunzip failed: %v", err)
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}
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if !strings.Contains(string(plain), bannerGuard) {
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t.Fatalf("banner absent for upper-case GZIP encoding: %s", plain)
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}
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}
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func TestInjectIntoBodyGzipFailOpen(t *testing.T) {
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// Bytes labelled gzip but NOT gzip → fail open: original bytes, ok=false,
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// no panic.
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bad := []byte("not gzip at all <head></head>")
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out, ok := injectIntoBody(bad, "gzip", "x", false)
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if ok {
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t.Fatal("corrupt gzip body must fail open (ok=false)")
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}
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if !bytes.Equal(out, bad) {
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t.Fatalf("fail-open must return the ORIGINAL bytes untouched")
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}
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}
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func TestInjectIntoBodyIdentity(t *testing.T) {
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// Identity (empty Content-Encoding): inject directly, grown body returned.
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html := []byte(`<html><head></head><body>hi</body></html>`)
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out, ok := injectIntoBody(html, "", "deadbeef", false)
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if !ok {
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t.Fatal("identity inject must report ok=true")
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}
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if !bytes.Contains(out, []byte(bannerGuard)) {
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t.Fatalf("banner absent on identity inject: %s", out)
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}
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if len(out) <= len(html) {
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t.Fatalf("identity inject must GROW the body: got %d, was %d", len(out), len(html))
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}
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}
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func TestInjectIntoBodyUnknownEncodingPassthrough(t *testing.T) {
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// br/zstd/deflate (shouldn't occur after the Accept-Encoding pin) → untouched.
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body := []byte("\x1f\x8b some br-ish bytes")
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out, ok := injectIntoBody(body, "br", "x", false)
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if ok {
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t.Fatal("unknown encoding must pass through (ok=false)")
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}
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if !bytes.Equal(out, body) {
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t.Fatalf("unknown-encoding passthrough must be byte-for-byte")
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}
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}
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func TestGunzipBombGuard(t *testing.T) {
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// A body that inflates beyond gunzipCap must be rejected (not OOM the worker).
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// gzip of >32MiB of zeros compresses to a small blob but inflates past the
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// cap → gunzipBytes returns an error → inject path fails open.
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big := gzipBytes(make([]byte, gunzipCap+1024))
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if _, err := gunzipBytes(big); err == nil {
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t.Fatal("gunzipBytes must reject output exceeding gunzipCap")
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}
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// And via the inject path: fail open, original bytes preserved.
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out, ok := injectIntoBody(big, "gzip", "x", false)
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if ok {
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t.Fatal("over-cap gzip body must fail open through injectIntoBody")
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}
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if !bytes.Equal(out, big) {
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t.Fatal("over-cap fail-open must return the original compressed bytes")
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}
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}
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func TestGunzipExactlyAtCap(t *testing.T) {
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// A body that inflates to EXACTLY gunzipCap is allowed (boundary).
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payload := make([]byte, gunzipCap)
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got, err := gunzipBytes(gzipBytes(payload))
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if err != nil {
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t.Fatalf("exactly-at-cap payload must be allowed: %v", err)
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}
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if len(got) != gunzipCap {
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t.Fatalf("at-cap length mismatch: got %d, want %d", len(got), gunzipCap)
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}
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}
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@ -37,6 +37,7 @@ import (
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"net"
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"net/http"
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"os"
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"strconv"
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"strings"
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"sync"
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"time"
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@ -324,6 +325,16 @@ func (px *Proxy) mitmPipeline(tconn *tls.Conn, rawClient net.Conn, host, verdict
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clientHash := clientHashFromConn(rawClient) // mac_hash-aware (WG persona)
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anonymizeRequest(req.Header)
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// #662 — pin the upstream Accept-Encoding to gzip (overwrite, dropping
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// br/zstd/deflate we cannot decode with the stdlib). This guarantees every
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// response is either gzip or identity, so the inject path can reliably
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// gunzip→inject→re-gzip the HTML. We Set (not Del): Del would make Go's
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// Transport auto-decompress and re-serve identity, losing wire compression
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// to the client for ALL resources (incl. non-injected ones). Set keeps the
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// Transport in pass-through mode so non-HTML bodies stay compressed
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// end-to-end. Browsers always accept gzip, so relaying gzip back is safe.
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req.Header.Set("Accept-Encoding", "gzip")
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// proxy upstream, inject into HTML bodies.
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up := &http.Client{Timeout: 30 * time.Second}
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if dialHost != "" {
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@ -356,9 +367,25 @@ func (px *Proxy) mitmPipeline(tconn *tls.Conn, rawClient net.Conn, host, verdict
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// Inject the transparency-banner loader only on 2xx text/html responses
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// (mirrors the Python addon, which skips non-200). The loader's same-origin
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// <script src="/__toolbox/loader.js"> is served by the short-circuit above.
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//
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// #662 — the body may be gzip-compressed (we pinned Accept-Encoding: gzip
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// upstream). injectIntoBody gunzips→injects→re-gzips when Content-Encoding
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// is gzip, injects directly when identity, and fails open (untouched) on a
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// corrupt/unknown encoding. Only on a successful rewrite do we update the
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// framing: writeResponse emits Content-Length from len(body), but a stale
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// resp.ContentLength / Content-Encoding could mislead downstream — so we
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// keep them consistent with the bytes we actually serve.
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if resp.StatusCode >= 200 && resp.StatusCode < 300 &&
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strings.Contains(resp.Header.Get("Content-Type"), "text/html") {
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body = injectLoader(body, clientHash, wg)
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if out, ok := injectIntoBody(body, resp.Header.Get("Content-Encoding"), clientHash, wg); ok {
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body = out
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// Keep the response framing consistent with the served bytes. The
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// encoding is unchanged (gzip stays gzip, identity stays identity);
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// only the length changed because injection grew the body. A stale
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// Content-Length would truncate/corrupt the response.
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resp.Header.Set("Content-Length", strconv.Itoa(len(body)))
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resp.ContentLength = int64(len(body))
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}
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}
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writeResponse(tconn, resp, body)
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}
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@ -1,3 +1,12 @@
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secubox-toolbox-ng (0.1.3-1~bookworm1) bookworm; urgency=medium
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* banner: inject into COMPRESSED HTML too. Pin upstream Accept-Encoding to gzip
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(stdlib can't brotli), and in the inject path gunzip → injectLoader → re-gzip
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(32MiB inflate cap, fail-open on corrupt). Fixes missing banner on the common
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gzip/br case; non-HTML passes through untouched. (ref #662)
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-- Gerald KERMA <devel@cybermind.fr> Wed, 18 Jun 2026 19:45:00 +0000
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secubox-toolbox-ng (0.1.2-1~bookworm1) bookworm; urgency=medium
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* banner: port the real transparency-banner inject — inject the loader
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Reference in New Issue
Block a user