traefik/pkg/middlewares/customerrors/custom_errors.go

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package customerrors
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import (
"bufio"
"bytes"
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"context"
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"fmt"
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"net"
"net/http"
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"net/url"
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"strconv"
"strings"
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"github.com/opentracing/opentracing-go/ext"
"github.com/sirupsen/logrus"
"github.com/traefik/traefik/v2/pkg/config/dynamic"
"github.com/traefik/traefik/v2/pkg/log"
"github.com/traefik/traefik/v2/pkg/middlewares"
"github.com/traefik/traefik/v2/pkg/tracing"
"github.com/traefik/traefik/v2/pkg/types"
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"github.com/vulcand/oxy/utils"
)
// Compile time validation that the response recorder implements http interfaces correctly.
var (
_ middlewares.Stateful = &responseRecorderWithCloseNotify{}
_ middlewares.Stateful = &codeCatcherWithCloseNotify{}
)
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const typeName = "customError"
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type serviceBuilder interface {
BuildHTTP(ctx context.Context, serviceName string) (http.Handler, error)
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}
// customErrors is a middleware that provides the custom error pages..
type customErrors struct {
name string
next http.Handler
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backendHandler http.Handler
httpCodeRanges types.HTTPCodeRanges
backendQuery string
}
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// New creates a new custom error pages middleware.
func New(ctx context.Context, next http.Handler, config dynamic.ErrorPage, serviceBuilder serviceBuilder, name string) (http.Handler, error) {
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log.FromContext(middlewares.GetLoggerCtx(ctx, name, typeName)).Debug("Creating middleware")
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httpCodeRanges, err := types.NewHTTPCodeRanges(config.Status)
if err != nil {
return nil, err
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}
backend, err := serviceBuilder.BuildHTTP(ctx, config.Service)
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if err != nil {
return nil, err
}
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return &customErrors{
name: name,
next: next,
backendHandler: backend,
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httpCodeRanges: httpCodeRanges,
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backendQuery: config.Query,
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}, nil
}
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func (c *customErrors) GetTracingInformation() (string, ext.SpanKindEnum) {
return c.name, tracing.SpanKindNoneEnum
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}
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func (c *customErrors) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
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ctx := middlewares.GetLoggerCtx(req.Context(), c.name, typeName)
logger := log.FromContext(ctx)
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if c.backendHandler == nil {
logger.Error("Error pages: no backend handler.")
tracing.SetErrorWithEvent(req, "Error pages: no backend handler.")
c.next.ServeHTTP(rw, req)
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return
}
catcher := newCodeCatcher(rw, c.httpCodeRanges)
c.next.ServeHTTP(catcher, req)
if !catcher.isFilteredCode() {
return
}
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// check the recorder code against the configured http status code ranges
code := catcher.getCode()
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for _, block := range c.httpCodeRanges {
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if code < block[0] || code > block[1] {
continue
}
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logger.Debugf("Caught HTTP Status Code %d, returning error page", code)
var query string
if len(c.backendQuery) > 0 {
query = "/" + strings.TrimPrefix(c.backendQuery, "/")
query = strings.ReplaceAll(query, "{status}", strconv.Itoa(code))
}
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pageReq, err := newRequest("http://" + req.Host + query)
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if err != nil {
logger.Error(err)
rw.WriteHeader(code)
_, err = fmt.Fprint(rw, http.StatusText(code))
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if err != nil {
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http.Error(rw, err.Error(), http.StatusInternalServerError)
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}
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return
}
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recorderErrorPage := newResponseRecorder(ctx, rw)
utils.CopyHeaders(pageReq.Header, req.Header)
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c.backendHandler.ServeHTTP(recorderErrorPage, pageReq.WithContext(req.Context()))
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utils.CopyHeaders(rw.Header(), recorderErrorPage.Header())
rw.WriteHeader(code)
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if _, err = rw.Write(recorderErrorPage.GetBody().Bytes()); err != nil {
logger.Error(err)
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}
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return
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}
}
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func newRequest(baseURL string) (*http.Request, error) {
u, err := url.Parse(baseURL)
if err != nil {
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return nil, fmt.Errorf("error pages: error when parse URL: %w", err)
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}
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req, err := http.NewRequest(http.MethodGet, u.String(), nil)
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if err != nil {
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return nil, fmt.Errorf("error pages: error when create query: %w", err)
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}
req.RequestURI = u.RequestURI()
return req, nil
}
type responseInterceptor interface {
http.ResponseWriter
http.Flusher
getCode() int
isFilteredCode() bool
}
// codeCatcher is a response writer that detects as soon as possible whether the
// response is a code within the ranges of codes it watches for. If it is, it
// simply drops the data from the response. Otherwise, it forwards it directly to
// the original client (its responseWriter) without any buffering.
type codeCatcher struct {
headerMap http.Header
code int
httpCodeRanges types.HTTPCodeRanges
firstWrite bool
caughtFilteredCode bool
responseWriter http.ResponseWriter
headersSent bool
}
type codeCatcherWithCloseNotify struct {
*codeCatcher
}
// CloseNotify returns a channel that receives at most a
// single value (true) when the client connection has gone away.
func (cc *codeCatcherWithCloseNotify) CloseNotify() <-chan bool {
return cc.responseWriter.(http.CloseNotifier).CloseNotify()
}
func newCodeCatcher(rw http.ResponseWriter, httpCodeRanges types.HTTPCodeRanges) responseInterceptor {
catcher := &codeCatcher{
headerMap: make(http.Header),
code: http.StatusOK, // If backend does not call WriteHeader on us, we consider it's a 200.
responseWriter: rw,
httpCodeRanges: httpCodeRanges,
firstWrite: true,
}
if _, ok := rw.(http.CloseNotifier); ok {
return &codeCatcherWithCloseNotify{catcher}
}
return catcher
}
func (cc *codeCatcher) Header() http.Header {
if cc.headerMap == nil {
cc.headerMap = make(http.Header)
}
return cc.headerMap
}
func (cc *codeCatcher) getCode() int {
return cc.code
}
// isFilteredCode returns whether the codeCatcher received a response code among the ones it is watching,
// and for which the response should be deferred to the error handler.
func (cc *codeCatcher) isFilteredCode() bool {
return cc.caughtFilteredCode
}
func (cc *codeCatcher) Write(buf []byte) (int, error) {
if !cc.firstWrite {
if cc.caughtFilteredCode {
// We don't care about the contents of the response,
// since we want to serve the ones from the error page,
// so we just drop them.
return len(buf), nil
}
return cc.responseWriter.Write(buf)
}
cc.firstWrite = false
// If WriteHeader was already called from the caller, this is a NOOP.
// Otherwise, cc.code is actually a 200 here.
cc.WriteHeader(cc.code)
if cc.caughtFilteredCode {
return len(buf), nil
}
return cc.responseWriter.Write(buf)
}
func (cc *codeCatcher) WriteHeader(code int) {
if cc.headersSent || cc.caughtFilteredCode {
return
}
cc.code = code
for _, block := range cc.httpCodeRanges {
if cc.code >= block[0] && cc.code <= block[1] {
cc.caughtFilteredCode = true
break
}
}
// it will be up to the other response recorder to send the headers,
// so it is out of our hands now.
if cc.caughtFilteredCode {
return
}
utils.CopyHeaders(cc.responseWriter.Header(), cc.Header())
cc.responseWriter.WriteHeader(cc.code)
cc.headersSent = true
}
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// Hijack hijacks the connection.
func (cc *codeCatcher) Hijack() (net.Conn, *bufio.ReadWriter, error) {
if hj, ok := cc.responseWriter.(http.Hijacker); ok {
return hj.Hijack()
}
return nil, nil, fmt.Errorf("%T is not a http.Hijacker", cc.responseWriter)
}
// Flush sends any buffered data to the client.
func (cc *codeCatcher) Flush() {
// If WriteHeader was already called from the caller, this is a NOOP.
// Otherwise, cc.code is actually a 200 here.
cc.WriteHeader(cc.code)
if flusher, ok := cc.responseWriter.(http.Flusher); ok {
flusher.Flush()
}
}
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type responseRecorder interface {
http.ResponseWriter
http.Flusher
GetCode() int
GetBody() *bytes.Buffer
IsStreamingResponseStarted() bool
}
// newResponseRecorder returns an initialized responseRecorder.
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func newResponseRecorder(ctx context.Context, rw http.ResponseWriter) responseRecorder {
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recorder := &responseRecorderWithoutCloseNotify{
HeaderMap: make(http.Header),
Body: new(bytes.Buffer),
Code: http.StatusOK,
responseWriter: rw,
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logger: log.FromContext(ctx),
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}
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
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logger logrus.FieldLogger
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}
type responseRecorderWithCloseNotify struct {
*responseRecorderWithoutCloseNotify
}
// CloseNotify returns a channel that receives at most a
// single value (true) when the client connection has gone away.
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func (r *responseRecorderWithCloseNotify) CloseNotify() <-chan bool {
return r.responseWriter.(http.CloseNotifier).CloseNotify()
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}
// Header returns the response headers.
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func (r *responseRecorderWithoutCloseNotify) Header() http.Header {
if r.HeaderMap == nil {
r.HeaderMap = make(http.Header)
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}
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return r.HeaderMap
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}
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func (r *responseRecorderWithoutCloseNotify) GetCode() int {
return r.Code
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}
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func (r *responseRecorderWithoutCloseNotify) GetBody() *bytes.Buffer {
return r.Body
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}
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func (r *responseRecorderWithoutCloseNotify) IsStreamingResponseStarted() bool {
return r.streamingResponseStarted
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}
// Write always succeeds and writes to rw.Body, if not nil.
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func (r *responseRecorderWithoutCloseNotify) Write(buf []byte) (int, error) {
if r.err != nil {
return 0, r.err
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}
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return r.Body.Write(buf)
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}
// WriteHeader sets rw.Code.
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func (r *responseRecorderWithoutCloseNotify) WriteHeader(code int) {
r.Code = code
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}
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// Hijack hijacks the connection.
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func (r *responseRecorderWithoutCloseNotify) Hijack() (net.Conn, *bufio.ReadWriter, error) {
return r.responseWriter.(http.Hijacker).Hijack()
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}
// Flush sends any buffered data to the client.
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func (r *responseRecorderWithoutCloseNotify) Flush() {
if !r.streamingResponseStarted {
utils.CopyHeaders(r.responseWriter.Header(), r.Header())
r.responseWriter.WriteHeader(r.Code)
r.streamingResponseStarted = true
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}
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_, err := r.responseWriter.Write(r.Body.Bytes())
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if err != nil {
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r.logger.Errorf("Error writing response in responseRecorder: %v", err)
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r.err = err
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}
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r.Body.Reset()
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if flusher, ok := r.responseWriter.(http.Flusher); ok {
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flusher.Flush()
}
}