mirror of
https://github.com/tailscale/tailscale.git
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249 lines
8.0 KiB
Go
249 lines
8.0 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package web
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import (
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"bytes"
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"context"
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"crypto/rand"
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"encoding/base64"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"net/http"
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"time"
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"tailscale.com/client/tailscale/apitype"
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"tailscale.com/tailcfg"
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)
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const (
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sessionCookieName = "TS-Web-Session"
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sessionCookieExpiry = time.Hour * 24 * 30 // 30 days
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)
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// browserSession holds data about a user's browser session
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// on the full management web client.
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type browserSession struct {
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// ID is the unique identifier for the session.
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// It is passed in the user's "TS-Web-Session" browser cookie.
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ID string
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SrcNode tailcfg.NodeID
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SrcUser tailcfg.UserID
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AuthID string // from tailcfg.WebClientAuthResponse
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AuthURL string // from tailcfg.WebClientAuthResponse
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Created time.Time
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Authenticated bool
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}
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// isAuthorized reports true if the given session is authorized
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// to be used by its associated user to access the full management
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// web client.
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//
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// isAuthorized is true only when s.Authenticated is true (i.e.
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// the user has authenticated the session) and the session is not
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// expired.
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// 2023-10-05: Sessions expire by default 30 days after creation.
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func (s *browserSession) isAuthorized(now time.Time) bool {
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switch {
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case s == nil:
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return false
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case !s.Authenticated:
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return false // awaiting auth
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case s.isExpired(now):
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return false // expired
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}
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return true
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}
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// isExpired reports true if s is expired.
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// 2023-10-05: Sessions expire by default 30 days after creation.
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func (s *browserSession) isExpired(now time.Time) bool {
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return !s.Created.IsZero() && now.After(s.expires())
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}
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// expires reports when the given session expires.
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func (s *browserSession) expires() time.Time {
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return s.Created.Add(sessionCookieExpiry)
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}
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var (
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errNoSession = errors.New("no-browser-session")
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errNotUsingTailscale = errors.New("not-using-tailscale")
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errTaggedRemoteSource = errors.New("tagged-remote-source")
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errTaggedLocalSource = errors.New("tagged-local-source")
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errNotOwner = errors.New("not-owner")
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)
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// getSession retrieves the browser session associated with the request,
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// if one exists.
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//
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// An error is returned in any of the following cases:
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//
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// - (errNotUsingTailscale) The request was not made over tailscale.
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//
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// - (errNoSession) The request does not have a session.
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//
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// - (errTaggedRemoteSource) The source is remote (another node) and tagged.
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// Users must use their own user-owned devices to manage other nodes'
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// web clients.
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//
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// - (errTaggedLocalSource) The source is local (the same node) and tagged.
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// Tagged nodes can only be remotely managed, allowing ACLs to dictate
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// access to web clients.
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//
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// - (errNotOwner) The source is not the owner of this client (if the
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// client is user-owned). Only the owner is allowed to manage the
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// node via the web client.
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//
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// If no error is returned, the browserSession is always non-nil.
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// getTailscaleBrowserSession does not check whether the session has been
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// authorized by the user. Callers can use browserSession.isAuthorized.
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//
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// The WhoIsResponse is always populated, with a non-nil Node and UserProfile,
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// unless getTailscaleBrowserSession reports errNotUsingTailscale.
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func (s *Server) getSession(r *http.Request) (*browserSession, *apitype.WhoIsResponse, error) {
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whoIs, whoIsErr := s.lc.WhoIs(r.Context(), r.RemoteAddr)
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status, statusErr := s.lc.StatusWithoutPeers(r.Context())
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switch {
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case whoIsErr != nil:
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return nil, nil, errNotUsingTailscale
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case statusErr != nil:
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return nil, whoIs, statusErr
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case status.Self == nil:
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return nil, whoIs, errors.New("missing self node in tailscale status")
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case whoIs.Node.IsTagged() && whoIs.Node.StableID == status.Self.ID:
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return nil, whoIs, errTaggedLocalSource
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case whoIs.Node.IsTagged():
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return nil, whoIs, errTaggedRemoteSource
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case !status.Self.IsTagged() && status.Self.UserID != whoIs.UserProfile.ID:
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return nil, whoIs, errNotOwner
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}
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srcNode := whoIs.Node.ID
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srcUser := whoIs.UserProfile.ID
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cookie, err := r.Cookie(sessionCookieName)
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if errors.Is(err, http.ErrNoCookie) {
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return nil, whoIs, errNoSession
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} else if err != nil {
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return nil, whoIs, err
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}
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v, ok := s.browserSessions.Load(cookie.Value)
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if !ok {
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return nil, whoIs, errNoSession
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}
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session := v.(*browserSession)
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if session.SrcNode != srcNode || session.SrcUser != srcUser {
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// In this case the browser cookie is associated with another tailscale node.
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// Maybe the source browser's machine was logged out and then back in as a different node.
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// Return errNoSession because there is no session for this user.
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return nil, whoIs, errNoSession
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} else if session.isExpired(s.timeNow()) {
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// Session expired, remove from session map and return errNoSession.
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s.browserSessions.Delete(session.ID)
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return nil, whoIs, errNoSession
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}
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return session, whoIs, nil
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}
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// newSession creates a new session associated with the given source user/node,
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// and stores it back to the session cache. Creating of a new session includes
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// generating a new auth URL from the control server.
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func (s *Server) newSession(ctx context.Context, src *apitype.WhoIsResponse) (*browserSession, error) {
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d, err := s.getOrAwaitAuth(ctx, "", src.Node.ID)
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if err != nil {
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return nil, err
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}
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sid, err := s.newSessionID()
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if err != nil {
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return nil, err
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}
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session := &browserSession{
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ID: sid,
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SrcNode: src.Node.ID,
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SrcUser: src.UserProfile.ID,
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AuthID: d.ID,
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AuthURL: d.URL,
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Created: s.timeNow(),
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}
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s.browserSessions.Store(sid, session)
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return session, nil
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}
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// awaitUserAuth blocks until the given session auth has been completed
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// by the user on the control server, then updates the session cache upon
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// completion. An error is returned if control auth failed for any reason.
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func (s *Server) awaitUserAuth(ctx context.Context, session *browserSession) error {
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if session.isAuthorized(s.timeNow()) {
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return nil // already authorized
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}
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d, err := s.getOrAwaitAuth(ctx, session.AuthID, session.SrcNode)
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if err != nil {
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// Clean up the session. Doing this on any error from control
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// server to avoid the user getting stuck with a bad session
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// cookie.
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s.browserSessions.Delete(session.ID)
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return err
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}
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if d.Complete {
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session.Authenticated = d.Complete
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s.browserSessions.Store(session.ID, session)
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}
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return nil
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}
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// getOrAwaitAuth connects to the control server for user auth,
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// with the following behavior:
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//
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// 1. If authID is provided empty, a new auth URL is created on the control
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// server and reported back here, which can then be used to redirect the
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// user on the frontend.
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// 2. If authID is provided non-empty, the connection to control blocks until
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// the user has completed authenticating the associated auth URL,
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// or until ctx is canceled.
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func (s *Server) getOrAwaitAuth(ctx context.Context, authID string, src tailcfg.NodeID) (*tailcfg.WebClientAuthResponse, error) {
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type data struct {
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ID string
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Src tailcfg.NodeID
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}
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var b bytes.Buffer
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if err := json.NewEncoder(&b).Encode(data{ID: authID, Src: src}); err != nil {
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return nil, err
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}
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url := "http://" + apitype.LocalAPIHost + "/localapi/v0/debug-web-client"
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req, err := http.NewRequestWithContext(ctx, "POST", url, &b)
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if err != nil {
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return nil, err
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}
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resp, err := s.lc.DoLocalRequest(req)
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if err != nil {
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return nil, err
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}
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body, _ := io.ReadAll(resp.Body)
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resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return nil, fmt.Errorf("failed request: %s", body)
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}
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var authResp *tailcfg.WebClientAuthResponse
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if err := json.Unmarshal(body, &authResp); err != nil {
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return nil, err
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}
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return authResp, nil
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}
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func (s *Server) newSessionID() (string, error) {
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raw := make([]byte, 16)
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for i := 0; i < 5; i++ {
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if _, err := rand.Read(raw); err != nil {
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return "", err
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}
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cookie := "ts-web-" + base64.RawURLEncoding.EncodeToString(raw)
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if _, ok := s.browserSessions.Load(cookie); !ok {
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return cookie, nil
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}
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}
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return "", errors.New("too many collisions generating new session; please refresh page")
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}
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