encoding/gob: add "too big" check when writing a message
Messages that are too big are rejected when read, so they should
be rejected when written too.
Fixes #10518.
Change-Id: I96678fbe2d94f51b957fe26faef33cd8df3823dd
Reviewed-on: https://go-review.googlesource.com/9965
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/encoding/gob/encoder.go b/src/encoding/gob/encoder.go
index a340e47..62d0f42 100644
--- a/src/encoding/gob/encoder.go
+++ b/src/encoding/gob/encoder.go
@@ -5,6 +5,7 @@
package gob
import (
+ "errors"
"io"
"reflect"
"sync"
@@ -65,6 +66,11 @@
// it by hand.
message := b.Bytes()
messageLen := len(message) - maxLength
+ // Length cannot be bigger than the decoder can handle.
+ if messageLen >= tooBig {
+ enc.setError(errors.New("gob: encoder: message too big"))
+ return
+ }
// Encode the length.
enc.countState.b.Reset()
enc.countState.encodeUint(uint64(messageLen))
diff --git a/src/encoding/gob/encoder_test.go b/src/encoding/gob/encoder_test.go
index c0bd379..8a72a31 100644
--- a/src/encoding/gob/encoder_test.go
+++ b/src/encoding/gob/encoder_test.go
@@ -976,3 +976,21 @@
}
}
}
+
+// TestHugeWriteFails tests that enormous messages trigger an error.
+func TestHugeWriteFails(t *testing.T) {
+ if testing.Short() {
+ // Requires allocating a monster, so don't do this from all.bash.
+ t.Skip("skipping huge allocation in short mode")
+ }
+ huge := make([]byte, tooBig)
+ huge[0] = 7 // Make sure it's not all zeros.
+ buf := new(bytes.Buffer)
+ err := NewEncoder(buf).Encode(huge)
+ if err == nil {
+ t.Fatalf("expected error for huge slice")
+ }
+ if !strings.Contains(err.Error(), "message too big") {
+ t.Fatalf("expected 'too big' error; got %s\n", err.Error())
+ }
+}
