[internal-branch.go1.19-vendor] http2/hpack: avoid quadratic complexity in hpack decoding
When parsing a field literal containing two Huffman-encoded strings,
don't decode the first string until verifying all data is present.
Avoids forced quadratic complexity when repeatedly parsing a partial
field, repeating the Huffman decoding of the string on each iteration.
Thanks to Philippe Antoine (Catena cyber) for reporting this issue.
Fixes golang/go#57855
Fixes CVE-2022-41723
For golang/go#58355
Change-Id: I58a743df450a4a4923dddd5cf6bb0592b0a7bdf3
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1688184
TryBot-Result: Security TryBots <security-trybots@go-security-trybots.iam.gserviceaccount.com>
Reviewed-by: Julie Qiu <julieqiu@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Reviewed-on: https://go-review.googlesource.com/c/net/+/468135
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 8e2b117aee74f6b86c207a808b0255de45c0a18a)
Reviewed-on: https://go-review.googlesource.com/c/net/+/468335
diff --git a/http2/hpack/hpack.go b/http2/hpack/hpack.go
index 85f18a2..02e80e3 100644
--- a/http2/hpack/hpack.go
+++ b/http2/hpack/hpack.go
@@ -359,6 +359,7 @@
var hf HeaderField
wantStr := d.emitEnabled || it.indexed()
+ var undecodedName undecodedString
if nameIdx > 0 {
ihf, ok := d.at(nameIdx)
if !ok {
@@ -366,15 +367,27 @@
}
hf.Name = ihf.Name
} else {
- hf.Name, buf, err = d.readString(buf, wantStr)
+ undecodedName, buf, err = d.readString(buf)
if err != nil {
return err
}
}
- hf.Value, buf, err = d.readString(buf, wantStr)
+ undecodedValue, buf, err := d.readString(buf)
if err != nil {
return err
}
+ if wantStr {
+ if nameIdx <= 0 {
+ hf.Name, err = d.decodeString(undecodedName)
+ if err != nil {
+ return err
+ }
+ }
+ hf.Value, err = d.decodeString(undecodedValue)
+ if err != nil {
+ return err
+ }
+ }
d.buf = buf
if it.indexed() {
d.dynTab.add(hf)
@@ -459,46 +472,52 @@
return 0, origP, errNeedMore
}
-// readString decodes an hpack string from p.
+// readString reads an hpack string from p.
//
-// wantStr is whether s will be used. If false, decompression and
-// []byte->string garbage are skipped if s will be ignored
-// anyway. This does mean that huffman decoding errors for non-indexed
-// strings past the MAX_HEADER_LIST_SIZE are ignored, but the server
-// is returning an error anyway, and because they're not indexed, the error
-// won't affect the decoding state.
-func (d *Decoder) readString(p []byte, wantStr bool) (s string, remain []byte, err error) {
+// It returns a reference to the encoded string data to permit deferring decode costs
+// until after the caller verifies all data is present.
+func (d *Decoder) readString(p []byte) (u undecodedString, remain []byte, err error) {
if len(p) == 0 {
- return "", p, errNeedMore
+ return u, p, errNeedMore
}
isHuff := p[0]&128 != 0
strLen, p, err := readVarInt(7, p)
if err != nil {
- return "", p, err
+ return u, p, err
}
if d.maxStrLen != 0 && strLen > uint64(d.maxStrLen) {
- return "", nil, ErrStringLength
+ // Returning an error here means Huffman decoding errors
+ // for non-indexed strings past the maximum string length
+ // are ignored, but the server is returning an error anyway
+ // and because the string is not indexed the error will not
+ // affect the decoding state.
+ return u, nil, ErrStringLength
}
if uint64(len(p)) < strLen {
- return "", p, errNeedMore
+ return u, p, errNeedMore
}
- if !isHuff {
- if wantStr {
- s = string(p[:strLen])
- }
- return s, p[strLen:], nil
- }
+ u.isHuff = isHuff
+ u.b = p[:strLen]
+ return u, p[strLen:], nil
+}
- if wantStr {
- buf := bufPool.Get().(*bytes.Buffer)
- buf.Reset() // don't trust others
- defer bufPool.Put(buf)
- if err := huffmanDecode(buf, d.maxStrLen, p[:strLen]); err != nil {
- buf.Reset()
- return "", nil, err
- }
- s = buf.String()
- buf.Reset() // be nice to GC
+type undecodedString struct {
+ isHuff bool
+ b []byte
+}
+
+func (d *Decoder) decodeString(u undecodedString) (string, error) {
+ if !u.isHuff {
+ return string(u.b), nil
}
- return s, p[strLen:], nil
+ buf := bufPool.Get().(*bytes.Buffer)
+ buf.Reset() // don't trust others
+ var s string
+ err := huffmanDecode(buf, d.maxStrLen, u.b)
+ if err == nil {
+ s = buf.String()
+ }
+ buf.Reset() // be nice to GC
+ bufPool.Put(buf)
+ return s, err
}
diff --git a/http2/hpack/hpack_test.go b/http2/hpack/hpack_test.go
index a361a2a..d4693f6 100644
--- a/http2/hpack/hpack_test.go
+++ b/http2/hpack/hpack_test.go
@@ -709,6 +709,36 @@
}
}
+func TestSlowIncrementalDecode(t *testing.T) {
+ // TODO(dneil): Fix for -race mode.
+ t.Skip("too slow in -race mode")
+
+ var buf bytes.Buffer
+ enc := NewEncoder(&buf)
+ hf := HeaderField{
+ Name: strings.Repeat("k", 1<<20),
+ Value: strings.Repeat("v", 1<<20),
+ }
+ enc.WriteField(hf)
+ hbuf := buf.Bytes()
+ count := 0
+ dec := NewDecoder(initialHeaderTableSize, func(got HeaderField) {
+ count++
+ if count != 1 {
+ t.Errorf("decoded %v fields, want 1", count)
+ }
+ if got.Name != hf.Name {
+ t.Errorf("decoded Name does not match input")
+ }
+ if got.Value != hf.Value {
+ t.Errorf("decoded Value does not match input")
+ }
+ })
+ for i := 0; i < len(hbuf); i++ {
+ dec.Write(hbuf[i : i+1])
+ }
+}
+
func TestSaveBufLimit(t *testing.T) {
const maxStr = 1 << 10
var got []HeaderField
