From 67b897648d6cac32b94b7e98a01588df5c7c59de Mon Sep 17 00:00:00 2001
From: Damien Neil <dneil@google.com>
Date: Wed, 8 Nov 2023 02:47:56 +0800
Subject: [PATCH 1/2] [Backport] net/http: limit chunked data overhead

Offering: Cloud Core Network
CVE: CVE-2023-39326
Reference: https://go-review.googlesource.com/c/go/+/547355
Conflict: NA

The chunked transfer encoding adds some overhead to
the content transferred. When writing one byte per
chunk, for example, there are five bytes of overhead
per byte of data transferred: "1\r\nX\r\n" to send "X".

Chunks may include "chunk extensions",
which we skip over and do not use.
For example: "1;chunk extension here\r\nX\r\n".

A malicious sender can use chunk extensions to add
about 4k of overhead per byte of data.
(The maximum chunk header line size we will accept.)

Track the amount of overhead read in chunked data,
and produce an error if it seems excessive.

Note: The upstream does not submit this change to go1.17 according to the rules of MinorReleases.
Corego3.x are based on go1.17.8. Therefore, it need to submit the change to corego3.x.

Edited-by: machangwang m00509938

Updates #64433
Fixes #64434
Fixes CVE-2023-39326

Change-Id: I40f8d70eb6f9575fb43f506eb19132ccedafcf39
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/2076135
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
(cherry picked from commit 3473ae72ee66c60744665a24b2fde143e8964d4f)
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/2095407
Run-TryBot: Roland Shoemaker <bracewell@google.com>
TryBot-Result: Security TryBots <security-trybots@go-security-trybots.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/547355
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Signed-off-by: Ma Chang Wang  machangwang@huawei.com
---
 src/net/http/internal/chunked.go      | 36 +++++++++++++---
 src/net/http/internal/chunked_test.go | 59 +++++++++++++++++++++++++++
 2 files changed, 89 insertions(+), 6 deletions(-)

diff --git a/src/net/http/internal/chunked.go b/src/net/http/internal/chunked.go
index f06e5725f3..ddbaacbe5d 100644
--- a/src/net/http/internal/chunked.go
+++ b/src/net/http/internal/chunked.go
@@ -39,7 +39,8 @@ type chunkedReader struct {
 	n        uint64 // unread bytes in chunk
 	err      error
 	buf      [2]byte
-	checkEnd bool // whether need to check for \r\n chunk footer
+	checkEnd bool  // whether need to check for \r\n chunk footer
+	excess   int64 // "excessive" chunk overhead, for malicious sender detection
 }
 
 func (cr *chunkedReader) beginChunk() {
@@ -49,10 +50,38 @@ func (cr *chunkedReader) beginChunk() {
 	if cr.err != nil {
 		return
 	}
+	cr.excess += int64(len(line)) + 2 // header, plus \r\n after the chunk data
+	line = trimTrailingWhitespace(line)
+	line, cr.err = removeChunkExtension(line)
+	if cr.err != nil {
+		return
+	}
 	cr.n, cr.err = parseHexUint(line)
 	if cr.err != nil {
 		return
 	}
+	// A sender who sends one byte per chunk will send 5 bytes of overhead
+	// for every byte of data. ("1\r\nX\r\n" to send "X".)
+	// We want to allow this, since streaming a byte at a time can be legitimate.
+	//
+	// A sender can use chunk extensions to add arbitrary amounts of additional
+	// data per byte read. ("1;very long extension\r\nX\r\n" to send "X".)
+	// We don't want to disallow extensions (although we discard them),
+	// but we also don't want to allow a sender to reduce the signal/noise ratio
+	// arbitrarily.
+	//
+	// We track the amount of excess overhead read,
+	// and produce an error if it grows too large.
+	//
+	// Currently, we say that we're willing to accept 16 bytes of overhead per chunk,
+	// plus twice the amount of real data in the chunk.
+	cr.excess -= 16 + (2 * int64(cr.n))
+	if cr.excess < 0 {
+		cr.excess = 0
+	}
+	if cr.excess > 16*1024 {
+		cr.err = errors.New("chunked encoding contains too much non-data")
+	}
 	if cr.n == 0 {
 		cr.err = io.EOF
 	}
@@ -133,11 +162,6 @@ func readChunkLine(b *bufio.Reader) ([]byte, error) {
 	if len(p) >= maxLineLength {
 		return nil, ErrLineTooLong
 	}
-	p = trimTrailingWhitespace(p)
-	p, err = removeChunkExtension(p)
-	if err != nil {
-		return nil, err
-	}
 	return p, nil
 }
 
diff --git a/src/net/http/internal/chunked_test.go b/src/net/http/internal/chunked_test.go
index 08152ed1e2..5fbeb0855f 100644
--- a/src/net/http/internal/chunked_test.go
+++ b/src/net/http/internal/chunked_test.go
@@ -211,3 +211,62 @@ func TestChunkReadPartial(t *testing.T) {
 	}
 
 }
+
+func TestChunkReaderTooMuchOverhead(t *testing.T) {
+	// If the sender is sending 100x as many chunk header bytes as chunk data,
+	// we should reject the stream at some point.
+	chunk := []byte("1;")
+	for i := 0; i < 100; i++ {
+		chunk = append(chunk, 'a') // chunk extension
+	}
+	chunk = append(chunk, "\r\nX\r\n"...)
+	const bodylen = 1 << 20
+	r := NewChunkedReader(&funcReader{f: func(i int) ([]byte, error) {
+		if i < bodylen {
+			return chunk, nil
+		}
+		return []byte("0\r\n"), nil
+	}})
+	_, err := io.ReadAll(r)
+	if err == nil {
+		t.Fatalf("successfully read body with excessive overhead; want error")
+	}
+}
+
+func TestChunkReaderByteAtATime(t *testing.T) {
+	// Sending one byte per chunk should not trip the excess-overhead detection.
+	const bodylen = 1 << 20
+	r := NewChunkedReader(&funcReader{f: func(i int) ([]byte, error) {
+		if i < bodylen {
+			return []byte("1\r\nX\r\n"), nil
+		}
+		return []byte("0\r\n"), nil
+	}})
+	got, err := io.ReadAll(r)
+	if err != nil {
+		t.Errorf("unexpected error: %v", err)
+	}
+	if len(got) != bodylen {
+		t.Errorf("read %v bytes, want %v", len(got), bodylen)
+	}
+}
+
+type funcReader struct {
+	f   func(iteration int) ([]byte, error)
+	i   int
+	b   []byte
+	err error
+}
+
+func (r *funcReader) Read(p []byte) (n int, err error) {
+	if len(r.b) == 0 && r.err == nil {
+		r.b, r.err = r.f(r.i)
+		r.i++
+	}
+	n = copy(p, r.b)
+	r.b = r.b[n:]
+	if len(r.b) > 0 {
+		return n, nil
+	}
+	return n, r.err
+}
-- 
2.33.0

