handlers.go

package auth

import (
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/coreos/go-oidc/v3/oidc"
	"golang.org/x/oauth2"
)

func (a *authenticator) HandleRedirect(w http.ResponseWriter, r *http.Request) {
	var scopes []string
	if extraScopes := r.FormValue("extra_scopes"); extraScopes != "" {
		scopes = strings.Split(extraScopes, " ")
	}
	var clients []string
	if crossClients := r.FormValue("cross_client"); crossClients != "" {
		clients = strings.Split(crossClients, " ")
	}
	for _, client := range clients {
		scopes = append(scopes, "audience:server:client_id:"+client)
	}
	connectorID := ""
	if id := r.FormValue("connector_id"); id != "" {
		connectorID = id
	}

	authCodeURL := ""
	scopes = append(scopes, "openid", "profile", "email")
	if r.FormValue("offline_access") != "yes" {
		authCodeURL = a.oauth2Config(scopes).AuthCodeURL(a.newState())
	} else if a.offlineAsScope {
		scopes = append(scopes, "offline_access")
		authCodeURL = a.oauth2Config(scopes).AuthCodeURL(a.newState())
	} else {
		authCodeURL = a.oauth2Config(scopes).AuthCodeURL(a.newState(), oauth2.AccessTypeOffline)
	}
	if connectorID != "" {
		authCodeURL = authCodeURL + "&connector_id=" + connectorID
	}

	http.Redirect(w, r, authCodeURL, http.StatusSeeOther)
}

func (a *authenticator) HandleOAuth2Callback(w http.ResponseWriter, r *http.Request) {
	var (
		err   error
		token *oauth2.Token
	)

	ctx := oidc.ClientContext(r.Context(), a.client)
	oauth2Config := a.oauth2Config(nil)
	switch r.Method {
	case http.MethodGet:
		// Authorization redirect callback from OAuth2 auth flow.
		if errMsg := r.FormValue("error"); errMsg != "" {
			http.Error(w, errMsg+": "+r.FormValue("error_description"), http.StatusBadRequest)
			return
		}
		code := r.FormValue("code")
		if code == "" {
			http.Error(w, fmt.Sprintf("no code in request: %q", r.Form), http.StatusBadRequest)
			return
		}

		// TODO: verify state

		token, err = oauth2Config.Exchange(ctx, code)
	case http.MethodPost:
		// Form request from frontend to refresh a token.
		refresh := r.FormValue("refresh_token")
		if refresh == "" {
			http.Error(w, fmt.Sprintf("no refresh_token in request: %q", r.Form), http.StatusBadRequest)
			return
		}
		t := &oauth2.Token{
			RefreshToken: refresh,
			Expiry:       time.Now().Add(-time.Hour),
		}
		token, err = oauth2Config.TokenSource(ctx, t).Token()
	default:
		http.Error(w, fmt.Sprintf("method not implemented: %s", r.Method), http.StatusBadRequest)
		return
	}

	if err != nil {
		http.Error(w, fmt.Sprintf("failed to get token: %v", err), http.StatusInternalServerError)
		return
	}

	// extract the ID Token from OAuth2 token
	rawIDToken, ok := token.Extra("id_token").(string)
	if !ok {
		http.Error(w, "no id_token in token response", http.StatusInternalServerError)
		return
	}

	// parse and verify ID Token payload
	if _, err := a.verifier.Verify(r.Context(), rawIDToken); err != nil {
		http.Error(w, fmt.Sprintf("failed to verify ID token: %v", err), http.StatusInternalServerError)
		return
	}

	cookie := &http.Cookie{
		Name:     "oauth2-token",
		Value:    rawIDToken,
		Path:     "/",
		SameSite: http.SameSiteStrictMode,
		// HttpOnly: true,
		Secure: true, // TODO: set this to true on HTTPS
	}

	http.SetCookie(w, cookie)
	http.Redirect(w, r, a.SpaRedirectURI.String(), http.StatusFound)
}