Go1.16 encoding/gob fixes

src/crypto/rsa/pkcs1v15_test.go

@@ -238,6 +238,10 @@ func TestHashVerifyPKCS1v15(t *testing.T) {
 }
 
 func TestOverlongMessagePKCS1v15(t *testing.T) {
+	// OpenSSL now returns a random string instead of an error
+	if boring.Enabled() {
+		t.Skip("Not relevant in boring mode")
+	}
 	ciphertext := decodeBase64("fjOVdirUzFoLlukv80dBllMLjXythIf22feqPrNo0YoIjzyzyoMFiLjAc/Y4krkeZ11XFThIrEvw\nkRiZcCq5ng==")
 	_, err := DecryptPKCS1v15(nil, rsaPrivateKey, ciphertext)
 	if err == nil {

src/encoding/gob/decode.go

@@ -871,8 +871,16 @@ 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 {
+	// Track how deep we've recursed trying to skip nested ignored fields.
+	dec.ignoreDepth++
+	defer func() { dec.ignoreDepth-- }()
+	if dec.ignoreDepth > 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 {

src/encoding/gob/decoder.go

@@ -34,6 +34,8 @@ type Decoder struct {
 	freeList     *decoderState                           // list of free decoderStates; avoids reallocation
 	countBuf     []byte                                  // used for decoding integers while parsing messages
 	err          error
+	// ignoreDepth tracks the depth of recursively parsed ignored fields
+	ignoreDepth int
 }
 
 // NewDecoder returns a new decoder that reads from the io.Reader.

src/encoding/gob/gobencdec_test.go

@@ -12,6 +12,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"reflect"
 	"strings"
 	"testing"
 	"time"
@@ -796,3 +797,40 @@ 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)
+
+	// Nested slice
+	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)
+	}
+
+	// Nested struct
+	nested = reflect.StructOf([]reflect.StructField{{Name: "F", Type: typ}})
+	for i := 0; i < 100; i++ {
+		nested = reflect.StructOf([]reflect.StructField{{Name: "F", Type: nested}})
+	}
+	badStruct = reflect.New(reflect.StructOf([]reflect.StructField{{Name: "F", Type: nested}}))
+	enc.Encode(badStruct.Interface())
+	dec = NewDecoder(b)
+	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)
+	}
+}