traefik/pkg/middlewares/auth/forward.go

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package auth
import (
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"context"
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"errors"
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"fmt"
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"io"
"net"
"net/http"
"regexp"
"strings"
"time"
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"github.com/traefik/traefik/v3/pkg/config/dynamic"
"github.com/traefik/traefik/v3/pkg/middlewares"
"github.com/traefik/traefik/v3/pkg/middlewares/connectionheader"
"github.com/traefik/traefik/v3/pkg/tracing"
"github.com/traefik/traefik/v3/pkg/types"
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"github.com/vulcand/oxy/v2/forward"
"github.com/vulcand/oxy/v2/utils"
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"go.opentelemetry.io/otel/trace"
)
const (
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xForwardedURI = "X-Forwarded-Uri"
xForwardedMethod = "X-Forwarded-Method"
)
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const typeNameForward = "ForwardAuth"
// hopHeaders Hop-by-hop headers to be removed in the authentication request.
// http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
// Proxy-Authorization header is forwarded to the authentication server (see https://tools.ietf.org/html/rfc7235#section-4.4).
var hopHeaders = []string{
forward.Connection,
forward.KeepAlive,
forward.Te, // canonicalized version of "TE"
forward.Trailers,
forward.TransferEncoding,
forward.Upgrade,
}
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type forwardAuth struct {
address string
authResponseHeaders []string
authResponseHeadersRegex *regexp.Regexp
next http.Handler
name string
client http.Client
trustForwardHeader bool
authRequestHeaders []string
addAuthCookiesToResponse map[string]struct{}
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}
// NewForward creates a forward auth middleware.
func NewForward(ctx context.Context, next http.Handler, config dynamic.ForwardAuth, name string) (http.Handler, error) {
logger := middlewares.GetLogger(ctx, name, typeNameForward)
logger.Debug().Msg("Creating middleware")
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addAuthCookiesToResponse := make(map[string]struct{})
for _, cookieName := range config.AddAuthCookiesToResponse {
addAuthCookiesToResponse[cookieName] = struct{}{}
}
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fa := &forwardAuth{
address: config.Address,
authResponseHeaders: config.AuthResponseHeaders,
next: next,
name: name,
trustForwardHeader: config.TrustForwardHeader,
authRequestHeaders: config.AuthRequestHeaders,
addAuthCookiesToResponse: addAuthCookiesToResponse,
}
// Ensure our request client does not follow redirects
fa.client = http.Client{
CheckRedirect: func(r *http.Request, via []*http.Request) error {
return http.ErrUseLastResponse
},
Timeout: 30 * time.Second,
}
if config.TLS != nil {
if config.TLS.CAOptional != nil {
logger.Warn().Msg("CAOptional option is deprecated, TLS client authentication is a server side option, please remove any usage of this option.")
}
clientTLS := &types.ClientTLS{
CA: config.TLS.CA,
Cert: config.TLS.Cert,
Key: config.TLS.Key,
InsecureSkipVerify: config.TLS.InsecureSkipVerify,
}
tlsConfig, err := clientTLS.CreateTLSConfig(ctx)
if err != nil {
return nil, fmt.Errorf("unable to create client TLS configuration: %w", err)
}
tr := http.DefaultTransport.(*http.Transport).Clone()
tr.TLSClientConfig = tlsConfig
fa.client.Transport = tr
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}
if config.AuthResponseHeadersRegex != "" {
re, err := regexp.Compile(config.AuthResponseHeadersRegex)
if err != nil {
return nil, fmt.Errorf("error compiling regular expression %s: %w", config.AuthResponseHeadersRegex, err)
}
fa.authResponseHeadersRegex = re
}
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return fa, nil
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}
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func (fa *forwardAuth) GetTracingInformation() (string, string, trace.SpanKind) {
return fa.name, typeNameForward, trace.SpanKindInternal
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}
func (fa *forwardAuth) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
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logger := middlewares.GetLogger(req.Context(), fa.name, typeNameForward)
req = connectionheader.Remove(req)
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forwardReq, err := http.NewRequestWithContext(req.Context(), http.MethodGet, fa.address, nil)
if err != nil {
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logMessage := fmt.Sprintf("Error calling %s. Cause %s", fa.address, err)
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logger.Debug().Msg(logMessage)
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tracing.SetStatusErrorf(req.Context(), logMessage)
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rw.WriteHeader(http.StatusInternalServerError)
return
}
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var forwardSpan trace.Span
if tracer := tracing.TracerFromContext(req.Context()); tracer != nil {
var tracingCtx context.Context
tracingCtx, forwardSpan = tracer.Start(req.Context(), "AuthRequest", trace.WithSpanKind(trace.SpanKindClient))
defer forwardSpan.End()
forwardReq = forwardReq.WithContext(tracingCtx)
tracing.InjectContextIntoCarrier(forwardReq)
tracing.LogClientRequest(forwardSpan, forwardReq)
}
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writeHeader(req, forwardReq, fa.trustForwardHeader, fa.authRequestHeaders)
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forwardResponse, forwardErr := fa.client.Do(forwardReq)
if forwardErr != nil {
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logMessage := fmt.Sprintf("Error calling %s. Cause: %s", fa.address, forwardErr)
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logger.Debug().Msg(logMessage)
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tracing.SetStatusErrorf(forwardReq.Context(), logMessage)
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rw.WriteHeader(http.StatusInternalServerError)
return
}
defer forwardResponse.Body.Close()
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body, readError := io.ReadAll(forwardResponse.Body)
if readError != nil {
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logMessage := fmt.Sprintf("Error reading body %s. Cause: %s", fa.address, readError)
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logger.Debug().Msg(logMessage)
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tracing.SetStatusErrorf(forwardReq.Context(), logMessage)
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rw.WriteHeader(http.StatusInternalServerError)
return
}
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// Ending the forward request span as soon as the response is handled.
// If any errors happen earlier, this span will be close by the defer instruction.
if forwardSpan != nil {
forwardSpan.End()
}
// Pass the forward response's body and selected headers if it
// didn't return a response within the range of [200, 300).
if forwardResponse.StatusCode < http.StatusOK || forwardResponse.StatusCode >= http.StatusMultipleChoices {
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logger.Debug().Msgf("Remote error %s. StatusCode: %d", fa.address, forwardResponse.StatusCode)
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utils.CopyHeaders(rw.Header(), forwardResponse.Header)
utils.RemoveHeaders(rw.Header(), hopHeaders...)
// Grab the location header, if any.
redirectURL, err := forwardResponse.Location()
if err != nil {
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if !errors.Is(err, http.ErrNoLocation) {
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logMessage := fmt.Sprintf("Error reading response location header %s. Cause: %s", fa.address, err)
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logger.Debug().Msg(logMessage)
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tracing.SetStatusErrorf(forwardReq.Context(), logMessage)
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rw.WriteHeader(http.StatusInternalServerError)
return
}
} else if redirectURL.String() != "" {
// Set the location in our response if one was sent back.
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rw.Header().Set("Location", redirectURL.String())
}
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tracing.LogResponseCode(forwardSpan, forwardResponse.StatusCode, trace.SpanKindClient)
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rw.WriteHeader(forwardResponse.StatusCode)
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if _, err = rw.Write(body); err != nil {
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logger.Error().Err(err).Send()
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}
return
}
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for _, headerName := range fa.authResponseHeaders {
headerKey := http.CanonicalHeaderKey(headerName)
req.Header.Del(headerKey)
if len(forwardResponse.Header[headerKey]) > 0 {
req.Header[headerKey] = append([]string(nil), forwardResponse.Header[headerKey]...)
}
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}
if fa.authResponseHeadersRegex != nil {
for headerKey := range req.Header {
if fa.authResponseHeadersRegex.MatchString(headerKey) {
req.Header.Del(headerKey)
}
}
for headerKey, headerValues := range forwardResponse.Header {
if fa.authResponseHeadersRegex.MatchString(headerKey) {
req.Header[headerKey] = append([]string(nil), headerValues...)
}
}
}
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tracing.LogResponseCode(forwardSpan, forwardResponse.StatusCode, trace.SpanKindClient)
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req.RequestURI = req.URL.RequestURI()
authCookies := forwardResponse.Cookies()
if len(authCookies) == 0 {
fa.next.ServeHTTP(rw, req)
return
}
fa.next.ServeHTTP(middlewares.NewResponseModifier(rw, req, fa.buildModifier(authCookies)), req)
}
func (fa *forwardAuth) buildModifier(authCookies []*http.Cookie) func(res *http.Response) error {
return func(res *http.Response) error {
cookies := res.Cookies()
res.Header.Del("Set-Cookie")
for _, cookie := range cookies {
if _, found := fa.addAuthCookiesToResponse[cookie.Name]; !found {
res.Header.Add("Set-Cookie", cookie.String())
}
}
for _, cookie := range authCookies {
if _, found := fa.addAuthCookiesToResponse[cookie.Name]; found {
res.Header.Add("Set-Cookie", cookie.String())
}
}
return nil
}
}
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func writeHeader(req, forwardReq *http.Request, trustForwardHeader bool, allowedHeaders []string) {
utils.CopyHeaders(forwardReq.Header, req.Header)
utils.RemoveHeaders(forwardReq.Header, hopHeaders...)
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forwardReq.Header = filterForwardRequestHeaders(forwardReq.Header, allowedHeaders)
if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
if trustForwardHeader {
if prior, ok := req.Header[forward.XForwardedFor]; ok {
clientIP = strings.Join(prior, ", ") + ", " + clientIP
}
}
forwardReq.Header.Set(forward.XForwardedFor, clientIP)
}
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xMethod := req.Header.Get(xForwardedMethod)
switch {
case xMethod != "" && trustForwardHeader:
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forwardReq.Header.Set(xForwardedMethod, xMethod)
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case req.Method != "":
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forwardReq.Header.Set(xForwardedMethod, req.Method)
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default:
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forwardReq.Header.Del(xForwardedMethod)
}
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xfp := req.Header.Get(forward.XForwardedProto)
switch {
case xfp != "" && trustForwardHeader:
forwardReq.Header.Set(forward.XForwardedProto, xfp)
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case req.TLS != nil:
forwardReq.Header.Set(forward.XForwardedProto, "https")
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default:
forwardReq.Header.Set(forward.XForwardedProto, "http")
}
if xfp := req.Header.Get(forward.XForwardedPort); xfp != "" && trustForwardHeader {
forwardReq.Header.Set(forward.XForwardedPort, xfp)
}
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xfh := req.Header.Get(forward.XForwardedHost)
switch {
case xfh != "" && trustForwardHeader:
forwardReq.Header.Set(forward.XForwardedHost, xfh)
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case req.Host != "":
forwardReq.Header.Set(forward.XForwardedHost, req.Host)
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default:
forwardReq.Header.Del(forward.XForwardedHost)
}
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xfURI := req.Header.Get(xForwardedURI)
switch {
case xfURI != "" && trustForwardHeader:
forwardReq.Header.Set(xForwardedURI, xfURI)
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case req.URL.RequestURI() != "":
forwardReq.Header.Set(xForwardedURI, req.URL.RequestURI())
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default:
forwardReq.Header.Del(xForwardedURI)
}
}
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func filterForwardRequestHeaders(forwardRequestHeaders http.Header, allowedHeaders []string) http.Header {
if len(allowedHeaders) == 0 {
return forwardRequestHeaders
}
filteredHeaders := http.Header{}
for _, headerName := range allowedHeaders {
values := forwardRequestHeaders.Values(headerName)
if len(values) > 0 {
filteredHeaders[http.CanonicalHeaderKey(headerName)] = append([]string(nil), values...)
}
}
return filteredHeaders
}