package errorpages import ( "bufio" "bytes" "errors" "fmt" "net" "net/http" "net/url" "strconv" "strings" "github.com/containous/traefik/log" "github.com/containous/traefik/middlewares" "github.com/containous/traefik/types" "github.com/vulcand/oxy/forward" "github.com/vulcand/oxy/utils" ) // Compile time validation that the response recorder implements http interfaces correctly. var _ middlewares.Stateful = &responseRecorderWithCloseNotify{} // Handler is a middleware that provides the custom error pages type Handler struct { BackendName string backendHandler http.Handler httpCodeRanges types.HTTPCodeRanges backendURL string backendQuery string FallbackURL string // Deprecated } // NewHandler initializes the utils.ErrorHandler for the custom error pages func NewHandler(errorPage *types.ErrorPage, backendName string) (*Handler, error) { if len(backendName) == 0 { return nil, errors.New("error pages: backend name is mandatory ") } httpCodeRanges, err := types.NewHTTPCodeRanges(errorPage.Status) if err != nil { return nil, err } return &Handler{ BackendName: backendName, httpCodeRanges: httpCodeRanges, backendQuery: errorPage.Query, backendURL: "http://0.0.0.0", }, nil } // PostLoad adds backend handler if available func (h *Handler) PostLoad(backendHandler http.Handler) error { if backendHandler == nil { fwd, err := forward.New() if err != nil { return err } h.backendHandler = fwd h.backendURL = h.FallbackURL } else { h.backendHandler = backendHandler } return nil } func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request, next http.HandlerFunc) { if h.backendHandler == nil { log.Error("Error pages: no backend handler.") next.ServeHTTP(w, req) return } recorder := newResponseRecorder(w) next.ServeHTTP(recorder, req) // check the recorder code against the configured http status code ranges for _, block := range h.httpCodeRanges { if recorder.GetCode() >= block[0] && recorder.GetCode() <= block[1] { log.Errorf("Caught HTTP Status Code %d, returning error page", recorder.GetCode()) var query string if len(h.backendQuery) > 0 { query = "/" + strings.TrimPrefix(h.backendQuery, "/") query = strings.Replace(query, "{status}", strconv.Itoa(recorder.GetCode()), -1) } pageReq, err := newRequest(h.backendURL + query) if err != nil { log.Error(err) w.WriteHeader(recorder.GetCode()) fmt.Fprint(w, http.StatusText(recorder.GetCode())) return } recorderErrorPage := newResponseRecorder(w) utils.CopyHeaders(pageReq.Header, req.Header) h.backendHandler.ServeHTTP(recorderErrorPage, pageReq.WithContext(req.Context())) utils.CopyHeaders(w.Header(), recorderErrorPage.Header()) w.WriteHeader(recorder.GetCode()) w.Write(recorderErrorPage.GetBody().Bytes()) return } } // did not catch a configured status code so proceed with the request utils.CopyHeaders(w.Header(), recorder.Header()) w.WriteHeader(recorder.GetCode()) w.Write(recorder.GetBody().Bytes()) } func newRequest(baseURL string) (*http.Request, error) { u, err := url.Parse(baseURL) if err != nil { return nil, fmt.Errorf("error pages: error when parse URL: %v", err) } req, err := http.NewRequest(http.MethodGet, u.String(), nil) if err != nil { return nil, fmt.Errorf("error pages: error when create query: %v", err) } req.RequestURI = u.RequestURI() return req, nil } type responseRecorder interface { http.ResponseWriter http.Flusher GetCode() int GetBody() *bytes.Buffer IsStreamingResponseStarted() bool } // newResponseRecorder returns an initialized responseRecorder. func newResponseRecorder(rw http.ResponseWriter) responseRecorder { recorder := &responseRecorderWithoutCloseNotify{ HeaderMap: make(http.Header), Body: new(bytes.Buffer), Code: http.StatusOK, responseWriter: rw, } if _, ok := rw.(http.CloseNotifier); ok { return &responseRecorderWithCloseNotify{recorder} } return recorder } // responseRecorderWithoutCloseNotify is an implementation of http.ResponseWriter that // records its mutations for later inspection. type responseRecorderWithoutCloseNotify struct { Code int // the HTTP response code from WriteHeader HeaderMap http.Header // the HTTP response headers Body *bytes.Buffer // if non-nil, the bytes.Buffer to append written data to responseWriter http.ResponseWriter err error streamingResponseStarted bool } type responseRecorderWithCloseNotify struct { *responseRecorderWithoutCloseNotify } // CloseNotify returns a channel that receives at most a // single value (true) when the client connection has gone away. func (r *responseRecorderWithCloseNotify) CloseNotify() <-chan bool { return r.responseWriter.(http.CloseNotifier).CloseNotify() } // Header returns the response headers. func (r *responseRecorderWithoutCloseNotify) Header() http.Header { if r.HeaderMap == nil { r.HeaderMap = make(http.Header) } return r.HeaderMap } func (r *responseRecorderWithoutCloseNotify) GetCode() int { return r.Code } func (r *responseRecorderWithoutCloseNotify) GetBody() *bytes.Buffer { return r.Body } func (r *responseRecorderWithoutCloseNotify) IsStreamingResponseStarted() bool { return r.streamingResponseStarted } // Write always succeeds and writes to rw.Body, if not nil. func (r *responseRecorderWithoutCloseNotify) Write(buf []byte) (int, error) { if r.err != nil { return 0, r.err } return r.Body.Write(buf) } // WriteHeader sets rw.Code. func (r *responseRecorderWithoutCloseNotify) WriteHeader(code int) { r.Code = code } // Hijack hijacks the connection func (r *responseRecorderWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) { return r.responseWriter.(http.Hijacker).Hijack() } // Flush sends any buffered data to the client. func (r *responseRecorderWithoutCloseNotify) Flush() { if !r.streamingResponseStarted { utils.CopyHeaders(r.responseWriter.Header(), r.Header()) r.responseWriter.WriteHeader(r.Code) r.streamingResponseStarted = true } _, err := r.responseWriter.Write(r.Body.Bytes()) if err != nil { log.Errorf("Error writing response in responseRecorder: %v", err) r.err = err } r.Body.Reset() if flusher, ok := r.responseWriter.(http.Flusher); ok { flusher.Flush() } }