handle some error conditions involving bad data.

R=rsc
DELTA=32  (24 added, 1 deleted, 7 changed)
OCL=32461
CL=32463

src/pkg/gob/decode.go

@@ -19,6 +19,7 @@ import (
 
 var (
 	errBadUint = os.ErrorString("gob: encoded unsigned integer out of range");
+	errBadType = os.ErrorString("gob: unknown type id or corrupted data");
 	errRange = os.ErrorString("gob: internal error: field numbers out of bounds");
 	errNotStruct = os.ErrorString("gob: TODO: can only handle structs")
 )
@@ -768,6 +769,10 @@ func decode(b *bytes.Buffer, wireId typeId, e interface{}) os.Error {
 		return os.ErrorString("gob: decode can't handle " + rt.String())
 	}
 	typeLock.Lock();
+	if _, ok := idToType[wireId]; !ok {
+		typeLock.Unlock();
+		return errBadType;
+	}
 	enginePtr, err := getDecEnginePtr(wireId, rt);
 	typeLock.Unlock();
 	if err != nil {

src/pkg/gob/decoder.go

@@ -64,11 +64,11 @@ func (dec *Decoder) Decode(e interface{}) os.Error {
 	dec.state.err = nil;
 	for {
 		// Read a count.
-		nbytes, err := decodeUintReader(dec.r, dec.oneByte);
-		if err != nil {
-			return err;
+		var nbytes uint64;
+		nbytes, dec.state.err = decodeUintReader(dec.r, dec.oneByte);
+		if dec.state.err != nil {
+			break;
 		}
-
 		// Allocate the buffer.
 		if nbytes > uint64(len(dec.buf)) {
 			dec.buf = make([]byte, nbytes + 1000);
@@ -77,12 +77,13 @@ func (dec *Decoder) Decode(e interface{}) os.Error {
 
 		// Read the data
 		var n int;
-		n, err = dec.r.Read(dec.buf[0:nbytes]);
-		if err != nil {
-			return err;
+		n, dec.state.err = io.ReadFull(dec.r, dec.buf[0:nbytes]);
+		if dec.state.err != nil {
+			break;
 		}
 		if n < int(nbytes) {
-			return os.ErrorString("gob decode: short read");
+			dec.state.err = io.ErrUnexpectedEOF;
+			break;
 		}
 
 		// Receive a type id.

src/pkg/gob/encoder_test.go

@@ -7,6 +7,7 @@ package gob
 import (
 	"bytes";
 	"gob";
+	"io";
 	"os";
 	"reflect";
 	"strings";
@@ -227,3 +228,19 @@ func TestWrongTypeDecoder(t *testing.T) {
 	badTypeCheck(new(ET3), false, "different name of field", t);
 	badTypeCheck(new(ET4), true, "different type of field", t);
 }
+
+func corruptDataCheck(s string, err os.Error, t *testing.T) {
+	b := bytes.NewBuffer(strings.Bytes(s));
+	dec := NewDecoder(b);
+	dec.Decode(new(ET2));
+	if dec.state.err != err {
+		t.Error("expected error", err, "got", dec.state.err);
+	}
+}
+
+// Check that we survive bad data.
+func TestBadData(t *testing.T) {
+	corruptDataCheck("\x01\x01\x01", os.EOF, t);
+	corruptDataCheck("\x7Fhi", io.ErrUnexpectedEOF, t);
+	corruptDataCheck("\x03now is the time for all good men", errBadType, t);
+}