encoding/xml: use iterative Skip, rather than recursive
Prevents exhausting the stack limit in _incredibly_ deeply nested
structures.
Fixes #53614
Fixes CVE-2022-28131
Change-Id: I47db4595ce10cecc29fbd06afce7b299868599e6
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1419912
Reviewed-by: Julie Qiu <julieqiu@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/417062
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/src/encoding/xml/read.go b/src/encoding/xml/read.go
index 0161306..a6fb665 100644
--- a/src/encoding/xml/read.go
+++ b/src/encoding/xml/read.go
@@ -747,12 +747,12 @@
}
// Skip reads tokens until it has consumed the end element
-// matching the most recent start element already consumed.
-// It recurs if it encounters a start element, so it can be used to
-// skip nested structures.
+// matching the most recent start element already consumed,
+// skipping nested structures.
// It returns nil if it finds an end element matching the start
// element; otherwise it returns an error describing the problem.
func (d *Decoder) Skip() error {
+ var depth int64
for {
tok, err := d.Token()
if err != nil {
@@ -760,11 +760,12 @@
}
switch tok.(type) {
case StartElement:
- if err := d.Skip(); err != nil {
- return err
- }
+ depth++
case EndElement:
- return nil
+ if depth == 0 {
+ return nil
+ }
+ depth--
}
}
}
diff --git a/src/encoding/xml/read_test.go b/src/encoding/xml/read_test.go
index 42059db..58d1edd 100644
--- a/src/encoding/xml/read_test.go
+++ b/src/encoding/xml/read_test.go
@@ -9,6 +9,7 @@
"errors"
"io"
"reflect"
+ "runtime"
"strings"
"testing"
"time"
@@ -1109,3 +1110,19 @@
t.Fatalf("Unmarshal unexpected error: got %q, want %q", err, errExeceededMaxUnmarshalDepth)
}
}
+
+func TestCVE202230633(t *testing.T) {
+ if runtime.GOARCH == "wasm" {
+ t.Skip("causes memory exhaustion on js/wasm")
+ }
+ defer func() {
+ p := recover()
+ if p != nil {
+ t.Fatal("Unmarshal panicked")
+ }
+ }()
+ var example struct {
+ Things []string
+ }
+ Unmarshal(bytes.Repeat([]byte("<a>"), 17_000_000), &example)
+}
