encoding/gob: add a depth limit for ignored fields
Enforce a nesting limit of 10,000 for ignored fields during decoding
of messages. This prevents the possibility of triggering stack
exhaustion.
Fixes #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>
Reviewed-on: https://go-review.googlesource.com/c/go/+/417064
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Tatiana Bradley <tatiana@golang.org>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
diff --git a/src/encoding/gob/decode.go b/src/encoding/gob/decode.go
index 34f302a..eea2924 100644
--- a/src/encoding/gob/decode.go
+++ b/src/encoding/gob/decode.go
@@ -871,8 +871,13 @@
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 @@
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 @@
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) 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 @@
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
}
diff --git a/src/encoding/gob/gobencdec_test.go b/src/encoding/gob/gobencdec_test.go
index 1d5dde2..3d49887 100644
--- a/src/encoding/gob/gobencdec_test.go
+++ b/src/encoding/gob/gobencdec_test.go
@@ -12,6 +12,7 @@
"fmt"
"io"
"net"
+ "reflect"
"strings"
"testing"
"time"
@@ -796,3 +797,26 @@
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)
+ }
+}
