agent: intention create returns 500 for bad body

agent/http.go

@@ -3,6 +3,7 @@ package agent
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"net/http/pprof"
@@ -384,6 +385,13 @@ func (s *HTTPServer) Index(resp http.ResponseWriter, req *http.Request) {
 
 // decodeBody is used to decode a JSON request body
 func decodeBody(req *http.Request, out interface{}, cb func(interface{}) error) error {
+	// This generally only happens in tests since real HTTP requests set
+	// a non-nil body with no content. We guard against it anyways to prevent
+	// a panic. The EOF response is the same behavior as an empty reader.
+	if req.Body == nil {
+		return io.EOF
+	}
+
 	var raw interface{}
 	dec := json.NewDecoder(req.Body)
 	if err := dec.Decode(&raw); err != nil {

agent/intentions_endpoint.go

@@ -50,9 +50,7 @@ func (s *HTTPServer) IntentionCreate(resp http.ResponseWriter, req *http.Request
 	s.parseDC(req, &args.Datacenter)
 	s.parseToken(req, &args.Token)
 	if err := decodeBody(req, &args.Intention, nil); err != nil {
-		resp.WriteHeader(http.StatusBadRequest)
-		fmt.Fprintf(resp, "Request decode failed: %v", err)
-		return nil, nil
+		return nil, fmt.Errorf("Failed to decode request body: %s", err)
 	}
 
 	var reply string

agent/intentions_endpoint_test.go

@@ -303,6 +303,19 @@ func TestIntentionsCreate_good(t *testing.T) {
 	}
 }
 
+func TestIntentionsCreate_noBody(t *testing.T) {
+	t.Parallel()
+
+	a := NewTestAgent(t.Name(), "")
+	defer a.Shutdown()
+
+	// Create with no body
+	req, _ := http.NewRequest("POST", "/v1/connect/intentions", nil)
+	resp := httptest.NewRecorder()
+	_, err := a.srv.IntentionCreate(resp, req)
+	require.Error(t, err)
+}
+
 func TestIntentionsSpecificGet_good(t *testing.T) {
 	t.Parallel()