Check for unreasonable data in binary propagation (#529)

* Check for unreasonable data in binary propagation

Assume the data is corrupt and return an error instead of attempting
to allocate hundreds of megabytes.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

* Change to W3C limits

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

propagation.go

@@ -215,6 +215,12 @@ func (p *BinaryPropagator) Inject(
 	return nil
 }
 
+// W3C limits https://github.com/w3c/baggage/blob/master/baggage/HTTP_HEADER_FORMAT.md#limits
+const (
+	maxBinaryBaggage      = 180
+	maxBinaryNameValueLen = 4096
+)
+
 // Extract implements Extractor of BinaryPropagator
 func (p *BinaryPropagator) Extract(abstractCarrier interface{}) (SpanContext, error) {
 	carrier, ok := abstractCarrier.(io.Reader)
@@ -245,6 +251,9 @@ func (p *BinaryPropagator) Extract(abstractCarrier interface{}) (SpanContext, er
 	if err := binary.Read(carrier, binary.BigEndian, &numBaggage); err != nil {
 		return emptyContext, opentracing.ErrSpanContextCorrupted
 	}
+	if numBaggage > maxBinaryBaggage {
+		return emptyContext, opentracing.ErrSpanContextCorrupted
+	}
 	if iNumBaggage := int(numBaggage); iNumBaggage > 0 {
 		ctx.baggage = make(map[string]string, iNumBaggage)
 		buf := p.buffers.Get().(*bytes.Buffer)
@@ -265,6 +274,9 @@ func (p *BinaryPropagator) Extract(abstractCarrier interface{}) (SpanContext, er
 			if err := binary.Read(carrier, binary.BigEndian, &valLen); err != nil {
 				return emptyContext, opentracing.ErrSpanContextCorrupted
 			}
+			if keyLen+valLen > maxBinaryNameValueLen {
+				return emptyContext, opentracing.ErrSpanContextCorrupted
+			}
 			buf.Reset()
 			buf.Grow(int(valLen))
 			if n, err := io.CopyN(buf, carrier, int64(valLen)); err != nil || int32(n) != valLen {

propagation_test.go

@@ -16,7 +16,9 @@ package jaeger
 
 import (
 	"bytes"
+	"encoding/base64"
 	"net/http"
+	"strings"
 	"testing"
 	"time"
 
@@ -127,6 +129,26 @@ func TestSpanPropagator(t *testing.T) {
 	}...)
 }
 
+func TestBinaryCorruption(t *testing.T) {
+	const op = "test"
+	reporter := NewInMemoryReporter()
+	tracer, closer := NewTracer("x", NewConstSampler(true), reporter)
+
+	sp := tracer.StartSpan(op)
+	carrier := new(bytes.Buffer)
+	err := tracer.Inject(sp.Context(), opentracing.Binary, carrier)
+	assert.NoError(t, err)
+
+	// suppose we encode the data then forget to decode it
+	data := base64.StdEncoding.EncodeToString(carrier.Bytes())
+	_, err = tracer.Extract(opentracing.Binary, strings.NewReader(data))
+	if assert.Error(t, err) {
+		assert.Equal(t, opentracing.ErrSpanContextCorrupted, err)
+	}
+	sp.Finish()
+	closer.Close()
+}
+
 func TestSpanIntegrityAfterSerialize(t *testing.T) {
 	serializedString := "f6c385a2c57ed8d7:00b04a90b7723bdc:76c385a2c57ed8d7:1"