First commit

2 files changed, 268 insertions, 0 deletions

diff --git a/middleware/errors/errors.go b/middleware/errors/errors.go
new file mode 100644
index 000000000..bf5bc7aae
--- /dev/null
+++ b/middleware/errors/errors.go
@@ -0,0 +1,100 @@
+// Package errors implements an HTTP error handling middleware.
+package errors
+
+import (
+	"fmt"
+	"log"
+	"runtime"
+	"strings"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/dns"
+)
+
+// ErrorHandler handles DNS errors (and errors from other middleware).
+type ErrorHandler struct {
+	Next      middleware.Handler
+	LogFile   string
+	Log       *log.Logger
+	LogRoller *middleware.LogRoller
+	Debug     bool // if true, errors are written out to client rather than to a log
+}
+
+func (h ErrorHandler) ServeDNS(w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	defer h.recovery(w, r)
+
+	rcode, err := h.Next.ServeDNS(w, r)
+
+	if err != nil {
+		errMsg := fmt.Sprintf("%s [ERROR %d %s %s] %v", time.Now().Format(timeFormat), rcode, r.Question[0].Name, dns.Type(r.Question[0].Qclass), err)
+
+		if h.Debug {
+			// Write error to response as a txt message instead of to log
+			answer := debugMsg(rcode, r)
+			txt, _ := dns.NewRR(". IN 0 TXT " + errMsg)
+			answer.Answer = append(answer.Answer, txt)
+			w.WriteMsg(answer)
+			return 0, err
+		}
+		h.Log.Println(errMsg)
+	}
+
+	return rcode, err
+}
+
+func (h ErrorHandler) recovery(w dns.ResponseWriter, r *dns.Msg) {
+	rec := recover()
+	if rec == nil {
+		return
+	}
+
+	// Obtain source of panic
+	// From: https://gist.github.com/swdunlop/9629168
+	var name, file string // function name, file name
+	var line int
+	var pc [16]uintptr
+	n := runtime.Callers(3, pc[:])
+	for _, pc := range pc[:n] {
+		fn := runtime.FuncForPC(pc)
+		if fn == nil {
+			continue
+		}
+		file, line = fn.FileLine(pc)
+		name = fn.Name()
+		if !strings.HasPrefix(name, "runtime.") {
+			break
+		}
+	}
+
+	// Trim file path
+	delim := "/coredns/"
+	pkgPathPos := strings.Index(file, delim)
+	if pkgPathPos > -1 && len(file) > pkgPathPos+len(delim) {
+		file = file[pkgPathPos+len(delim):]
+	}
+
+	panicMsg := fmt.Sprintf("%s [PANIC %s %s] %s:%d - %v", time.Now().Format(timeFormat), r.Question[0].Name, dns.Type(r.Question[0].Qtype), file, line, rec)
+	if h.Debug {
+		// Write error and stack trace to the response rather than to a log
+		var stackBuf [4096]byte
+		stack := stackBuf[:runtime.Stack(stackBuf[:], false)]
+		answer := debugMsg(dns.RcodeServerFailure, r)
+		// add stack buf in TXT, limited to 255 chars for now.
+		txt, _ := dns.NewRR(". IN 0 TXT " + string(stack[:255]))
+		answer.Answer = append(answer.Answer, txt)
+		w.WriteMsg(answer)
+	} else {
+		// Currently we don't use the function name, since file:line is more conventional
+		h.Log.Printf(panicMsg)
+	}
+}
+
+// debugMsg creates a debug message that gets send back to the client.
+func debugMsg(rcode int, r *dns.Msg) *dns.Msg {
+	answer := new(dns.Msg)
+	answer.SetRcode(r, rcode)
+	return answer
+}
+
+const timeFormat = "02/Jan/2006:15:04:05 -0700"
diff --git a/middleware/errors/errors_test.go b/middleware/errors/errors_test.go
new file mode 100644
index 000000000..4434e835c
--- /dev/null
+++ b/middleware/errors/errors_test.go
@@ -0,0 +1,168 @@
+package errors
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/miekg/coredns/middleware"
+)
+
+func TestErrors(t *testing.T) {
+	// create a temporary page
+	path := filepath.Join(os.TempDir(), "errors_test.html")
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Remove(path)
+
+	const content = "This is a error page"
+	_, err = f.WriteString(content)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Close()
+
+	buf := bytes.Buffer{}
+	em := ErrorHandler{
+		ErrorPages: map[int]string{
+			http.StatusNotFound:  path,
+			http.StatusForbidden: "not_exist_file",
+		},
+		Log: log.New(&buf, "", 0),
+	}
+	_, notExistErr := os.Open("not_exist_file")
+
+	testErr := errors.New("test error")
+	tests := []struct {
+		next         middleware.Handler
+		expectedCode int
+		expectedBody string
+		expectedLog  string
+		expectedErr  error
+	}{
+		{
+			next:         genErrorHandler(http.StatusOK, nil, "normal"),
+			expectedCode: http.StatusOK,
+			expectedBody: "normal",
+			expectedLog:  "",
+			expectedErr:  nil,
+		},
+		{
+			next:         genErrorHandler(http.StatusMovedPermanently, testErr, ""),
+			expectedCode: http.StatusMovedPermanently,
+			expectedBody: "",
+			expectedLog:  fmt.Sprintf("[ERROR %d %s] %v\n", http.StatusMovedPermanently, "/", testErr),
+			expectedErr:  testErr,
+		},
+		{
+			next:         genErrorHandler(http.StatusBadRequest, nil, ""),
+			expectedCode: 0,
+			expectedBody: fmt.Sprintf("%d %s\n", http.StatusBadRequest,
+				http.StatusText(http.StatusBadRequest)),
+			expectedLog: "",
+			expectedErr: nil,
+		},
+		{
+			next:         genErrorHandler(http.StatusNotFound, nil, ""),
+			expectedCode: 0,
+			expectedBody: content,
+			expectedLog:  "",
+			expectedErr:  nil,
+		},
+		{
+			next:         genErrorHandler(http.StatusForbidden, nil, ""),
+			expectedCode: 0,
+			expectedBody: fmt.Sprintf("%d %s\n", http.StatusForbidden,
+				http.StatusText(http.StatusForbidden)),
+			expectedLog: fmt.Sprintf("[NOTICE %d /] could not load error page: %v\n",
+				http.StatusForbidden, notExistErr),
+			expectedErr: nil,
+		},
+	}
+
+	req, err := http.NewRequest("GET", "/", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for i, test := range tests {
+		em.Next = test.next
+		buf.Reset()
+		rec := httptest.NewRecorder()
+		code, err := em.ServeHTTP(rec, req)
+
+		if err != test.expectedErr {
+			t.Errorf("Test %d: Expected error %v, but got %v",
+				i, test.expectedErr, err)
+		}
+		if code != test.expectedCode {
+			t.Errorf("Test %d: Expected status code %d, but got %d",
+				i, test.expectedCode, code)
+		}
+		if body := rec.Body.String(); body != test.expectedBody {
+			t.Errorf("Test %d: Expected body %q, but got %q",
+				i, test.expectedBody, body)
+		}
+		if log := buf.String(); !strings.Contains(log, test.expectedLog) {
+			t.Errorf("Test %d: Expected log %q, but got %q",
+				i, test.expectedLog, log)
+		}
+	}
+}
+
+func TestVisibleErrorWithPanic(t *testing.T) {
+	const panicMsg = "I'm a panic"
+	eh := ErrorHandler{
+		ErrorPages: make(map[int]string),
+		Debug:      true,
+		Next: middleware.HandlerFunc(func(w http.ResponseWriter, r *http.Request) (int, error) {
+			panic(panicMsg)
+		}),
+	}
+
+	req, err := http.NewRequest("GET", "/", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rec := httptest.NewRecorder()
+
+	code, err := eh.ServeHTTP(rec, req)
+
+	if code != 0 {
+		t.Errorf("Expected error handler to return 0 (it should write to response), got status %d", code)
+	}
+	if err != nil {
+		t.Errorf("Expected error handler to return nil error (it should panic!), but got '%v'", err)
+	}
+
+	body := rec.Body.String()
+
+	if !strings.Contains(body, "[PANIC /] middleware/errors/errors_test.go") {
+		t.Errorf("Expected response body to contain error log line, but it didn't:\n%s", body)
+	}
+	if !strings.Contains(body, panicMsg) {
+		t.Errorf("Expected response body to contain panic message, but it didn't:\n%s", body)
+	}
+	if len(body) < 500 {
+		t.Errorf("Expected response body to contain stack trace, but it was too short: len=%d", len(body))
+	}
+}
+
+func genErrorHandler(status int, err error, body string) middleware.Handler {
+	return middleware.HandlerFunc(func(w http.ResponseWriter, r *http.Request) (int, error) {
+		if len(body) > 0 {
+			w.Header().Set("Content-Length", strconv.Itoa(len(body)))
+			fmt.Fprint(w, body)
+		}
+		return status, err
+	})
+}