mirror of
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110 lines
3.3 KiB
Go
110 lines
3.3 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package main
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import (
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"context"
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"fmt"
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"log"
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"net/http"
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"net/http/httputil"
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"net/url"
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"os"
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"strings"
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"tailscale.com/client/tailscale"
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"tailscale.com/client/tailscale/apitype"
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"tailscale.com/tsnet"
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"tailscale.com/types/logger"
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)
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type whoIsKey struct{}
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// authProxy is an http.Handler that authenticates requests using the Tailscale
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// LocalAPI and then proxies them to the Kubernetes API.
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type authProxy struct {
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logf logger.Logf
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lc *tailscale.LocalClient
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rp *httputil.ReverseProxy
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}
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func (h *authProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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who, err := h.lc.WhoIs(r.Context(), r.RemoteAddr)
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if err != nil {
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h.logf("failed to authenticate caller: %v", err)
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http.Error(w, "failed to authenticate caller", http.StatusInternalServerError)
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return
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}
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r = r.WithContext(context.WithValue(r.Context(), whoIsKey{}, who))
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h.rp.ServeHTTP(w, r)
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}
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// runAuthProxy runs an HTTP server that authenticates requests using the
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// Tailscale LocalAPI and then proxies them to the Kubernetes API.
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// It listens on :443 and uses the Tailscale HTTPS certificate.
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// s will be started if it is not already running.
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// rt is used to proxy requests to the Kubernetes API.
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//
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// It never returns.
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func runAuthProxy(s *tsnet.Server, rt http.RoundTripper, logf logger.Logf) {
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ln, err := s.ListenTLS("tcp", ":443")
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if err != nil {
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log.Fatalf("could not listen on :443: %v", err)
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}
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u, err := url.Parse(fmt.Sprintf("https://%s:%s", os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT_HTTPS")))
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if err != nil {
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log.Fatalf("runAuthProxy: failed to parse URL %v", err)
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}
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lc, err := s.LocalClient()
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if err != nil {
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log.Fatalf("could not get local client: %v", err)
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}
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ap := &authProxy{
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logf: logf,
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lc: lc,
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rp: &httputil.ReverseProxy{
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Director: func(r *http.Request) {
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// We want to proxy to the Kubernetes API, but we want to use
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// the caller's identity to do so. We do this by impersonating
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// the caller using the Kubernetes User Impersonation feature:
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// https://kubernetes.io/docs/reference/access-authn-authz/authentication/#user-impersonation
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// Out of paranoia, remove all authentication headers that might
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// have been set by the client.
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r.Header.Del("Authorization")
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r.Header.Del("Impersonate-Group")
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r.Header.Del("Impersonate-User")
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r.Header.Del("Impersonate-Uid")
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for k := range r.Header {
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if strings.HasPrefix(k, "Impersonate-Extra-") {
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r.Header.Del(k)
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}
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}
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// Now add the impersonation headers that we want.
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who := r.Context().Value(whoIsKey{}).(*apitype.WhoIsResponse)
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if who.Node.IsTagged() {
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// Use the nodes FQDN as the username, and the nodes tags as the groups.
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// "Impersonate-Group" requires "Impersonate-User" to be set.
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r.Header.Set("Impersonate-User", strings.TrimSuffix(who.Node.Name, "."))
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for _, tag := range who.Node.Tags {
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r.Header.Add("Impersonate-Group", tag)
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}
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} else {
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r.Header.Set("Impersonate-User", who.UserProfile.LoginName)
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}
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// Replace the URL with the Kubernetes APIServer.
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r.URL.Scheme = u.Scheme
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r.URL.Host = u.Host
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},
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Transport: rt,
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},
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}
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if err := http.Serve(ln, ap); err != nil {
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log.Fatalf("runAuthProxy: failed to serve %v", err)
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}
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}
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