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[release-branch.go1.17] encoding/gob: add a depth limit for ignored fields

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Enforce a nesting limit of 10,000 for ignored fields during decoding
of messages. This prevents the possibility of triggering stack
exhaustion.

Fixes #53709
Updates #53615
Fixes CVE-2022-30635

Change-Id: I05103d06dd5ca3945fcba3c1f5d3b5a645e8fb0f
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1484771
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
(cherry picked from commit 55e8f938d22bfec29cc9dc9671044c5a41d1ea9c)
Reviewed-on: https://go-review.googlesource.com/c/go/+/417074
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
This commit is contained in:
Roland Shoemaker 2022-06-07 13:00:43 -07:00 committed by Michael Knyszek
parent 76f8b7304d
commit cd54600b86
2 changed files with 36 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/encoding/gob/decode.go
View File

@ -871,8 +871,13 @@ func (dec *Decoder) decOpFor(wireId typeId, rt reflect.Type, name string, inProg
return &op
}
var maxIgnoreNestingDepth = 10000
// decIgnoreOpFor returns the decoding op for a field that has no destination.
func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp) *decOp {
func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp, depth int) *decOp {
if depth > maxIgnoreNestingDepth {
error_(errors.New("invalid nesting depth"))
}
// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
// Return the pointer to the op we're already building.
if opPtr := inProgress[wireId]; opPtr != nil {
@ -896,7 +901,7 @@ func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp)
errorf("bad data: undefined type %s", wireId.string())
case wire.ArrayT != nil:
elemId := wire.ArrayT.Elem
elemOp := dec.decIgnoreOpFor(elemId, inProgress)
elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreArray(state, *elemOp, wire.ArrayT.Len)
}
@ -904,15 +909,15 @@ func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp)
case wire.MapT != nil:
keyId := dec.wireType[wireId].MapT.Key
elemId := dec.wireType[wireId].MapT.Elem
keyOp := dec.decIgnoreOpFor(keyId, inProgress)
elemOp := dec.decIgnoreOpFor(elemId, inProgress)
keyOp := dec.decIgnoreOpFor(keyId, inProgress, depth+1)
elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreMap(state, *keyOp, *elemOp)
}
case wire.SliceT != nil:
elemId := wire.SliceT.Elem
elemOp := dec.decIgnoreOpFor(elemId, inProgress)
elemOp := dec.decIgnoreOpFor(elemId, inProgress, depth+1)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreSlice(state, *elemOp)
}
@ -1073,7 +1078,7 @@ func (dec *Decoder) compileSingle(remoteId typeId, ut *userTypeInfo) (engine *de
func (dec *Decoder) compileIgnoreSingle(remoteId typeId) *decEngine {
engine := new(decEngine)
engine.instr = make([]decInstr, 1) // one item
op := dec.decIgnoreOpFor(remoteId, make(map[typeId]*decOp))
op := dec.decIgnoreOpFor(remoteId, make(map[typeId]*decOp), 0)
ovfl := overflow(dec.typeString(remoteId))
engine.instr[0] = decInstr{*op, 0, nil, ovfl}
engine.numInstr = 1
@ -1118,7 +1123,7 @@ func (dec *Decoder) compileDec(remoteId typeId, ut *userTypeInfo) (engine *decEn
localField, present := srt.FieldByName(wireField.Name)
// TODO(r): anonymous names
if !present || !isExported(wireField.Name) {
op := dec.decIgnoreOpFor(wireField.Id, make(map[typeId]*decOp))
op := dec.decIgnoreOpFor(wireField.Id, make(map[typeId]*decOp), 0)
engine.instr[fieldnum] = decInstr{*op, fieldnum, nil, ovfl}
continue
}

24
src/encoding/gob/gobencdec_test.go
View File

@ -12,6 +12,7 @@ import (
"fmt"
"io"
"net"
"reflect"
"strings"
"testing"
"time"
@ -796,3 +797,26 @@ func TestNetIP(t *testing.T) {
t.Errorf("decoded to %v, want 1.2.3.4", ip.String())
}
}
func TestIngoreDepthLimit(t *testing.T) {
// We don't test the actual depth limit because it requires building an
// extremely large message, which takes quite a while.
oldNestingDepth := maxIgnoreNestingDepth
maxIgnoreNestingDepth = 100
defer func() { maxIgnoreNestingDepth = oldNestingDepth }()
b := new(bytes.Buffer)
enc := NewEncoder(b)
typ := reflect.TypeOf(int(0))
nested := reflect.ArrayOf(1, typ)
for i := 0; i < 100; i++ {
nested = reflect.ArrayOf(1, nested)
}
badStruct := reflect.New(reflect.StructOf([]reflect.StructField{{Name: "F", Type: nested}}))
enc.Encode(badStruct.Interface())
dec := NewDecoder(b)
var output struct{ Hello int }
expectedErr := "invalid nesting depth"
if err := dec.Decode(&output); err == nil || err.Error() != expectedErr {
t.Errorf("Decode didn't fail with depth limit of 100: want %q, got %q", expectedErr, err)
}
}