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pkce_flow.go
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/
pkce_flow.go
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package auth
import (
"context"
"crypto/sha256"
"crypto/subtle"
"encoding/base64"
"errors"
"fmt"
"html/template"
"net"
"net/http"
"net/url"
"strings"
"time"
log "github.com/sirupsen/logrus"
"golang.org/x/oauth2"
"github.com/netbirdio/netbird/client/internal"
"github.com/netbirdio/netbird/client/internal/templates"
)
var _ OAuthFlow = &PKCEAuthorizationFlow{}
const (
queryState = "state"
queryCode = "code"
queryError = "error"
queryErrorDesc = "error_description"
defaultPKCETimeoutSeconds = 300
)
// PKCEAuthorizationFlow implements the OAuthFlow interface for
// the Authorization Code Flow with PKCE.
type PKCEAuthorizationFlow struct {
providerConfig internal.PKCEAuthProviderConfig
state string
codeVerifier string
oAuthConfig *oauth2.Config
}
// NewPKCEAuthorizationFlow returns new PKCE authorization code flow.
func NewPKCEAuthorizationFlow(config internal.PKCEAuthProviderConfig) (*PKCEAuthorizationFlow, error) {
var availableRedirectURL string
// find the first available redirect URL
for _, redirectURL := range config.RedirectURLs {
if !isRedirectURLPortUsed(redirectURL) {
availableRedirectURL = redirectURL
break
}
}
if availableRedirectURL == "" {
return nil, fmt.Errorf("no available port found from configured redirect URLs: %q", config.RedirectURLs)
}
cfg := &oauth2.Config{
ClientID: config.ClientID,
ClientSecret: config.ClientSecret,
Endpoint: oauth2.Endpoint{
AuthURL: config.AuthorizationEndpoint,
TokenURL: config.TokenEndpoint,
},
RedirectURL: availableRedirectURL,
Scopes: strings.Split(config.Scope, " "),
}
return &PKCEAuthorizationFlow{
providerConfig: config,
oAuthConfig: cfg,
}, nil
}
// GetClientID returns the provider client id
func (p *PKCEAuthorizationFlow) GetClientID(_ context.Context) string {
return p.providerConfig.ClientID
}
// RequestAuthInfo requests a authorization code login flow information.
func (p *PKCEAuthorizationFlow) RequestAuthInfo(ctx context.Context) (AuthFlowInfo, error) {
state, err := randomBytesInHex(24)
if err != nil {
return AuthFlowInfo{}, fmt.Errorf("could not generate random state: %v", err)
}
p.state = state
codeVerifier, err := randomBytesInHex(64)
if err != nil {
return AuthFlowInfo{}, fmt.Errorf("could not create a code verifier: %v", err)
}
p.codeVerifier = codeVerifier
codeChallenge := createCodeChallenge(codeVerifier)
authURL := p.oAuthConfig.AuthCodeURL(
state,
oauth2.SetAuthURLParam("code_challenge_method", "S256"),
oauth2.SetAuthURLParam("code_challenge", codeChallenge),
oauth2.SetAuthURLParam("audience", p.providerConfig.Audience),
)
return AuthFlowInfo{
VerificationURIComplete: authURL,
ExpiresIn: defaultPKCETimeoutSeconds,
}, nil
}
// WaitToken waits for the OAuth token in the PKCE Authorization Flow.
// It starts an HTTP server to receive the OAuth token callback and waits for the token or an error.
// Once the token is received, it is converted to TokenInfo and validated before returning.
func (p *PKCEAuthorizationFlow) WaitToken(ctx context.Context, _ AuthFlowInfo) (TokenInfo, error) {
tokenChan := make(chan *oauth2.Token, 1)
errChan := make(chan error, 1)
parsedURL, err := url.Parse(p.oAuthConfig.RedirectURL)
if err != nil {
return TokenInfo{}, fmt.Errorf("failed to parse redirect URL: %v", err)
}
server := &http.Server{Addr: fmt.Sprintf(":%s", parsedURL.Port())}
defer func() {
shutdownCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
defer cancel()
if err := server.Shutdown(shutdownCtx); err != nil {
log.Errorf("failed to close the server: %v", err)
}
}()
go p.startServer(server, tokenChan, errChan)
select {
case <-ctx.Done():
return TokenInfo{}, ctx.Err()
case token := <-tokenChan:
return p.parseOAuthToken(token)
case err := <-errChan:
return TokenInfo{}, err
}
}
func (p *PKCEAuthorizationFlow) startServer(server *http.Server, tokenChan chan<- *oauth2.Token, errChan chan<- error) {
mux := http.NewServeMux()
mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
token, err := p.handleRequest(req)
if err != nil {
renderPKCEFlowTmpl(w, err)
errChan <- fmt.Errorf("PKCE authorization flow failed: %v", err)
return
}
renderPKCEFlowTmpl(w, nil)
tokenChan <- token
})
server.Handler = mux
if err := server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
errChan <- err
}
}
func (p *PKCEAuthorizationFlow) handleRequest(req *http.Request) (*oauth2.Token, error) {
query := req.URL.Query()
if authError := query.Get(queryError); authError != "" {
authErrorDesc := query.Get(queryErrorDesc)
return nil, fmt.Errorf("%s.%s", authError, authErrorDesc)
}
// Prevent timing attacks on the state
if state := query.Get(queryState); subtle.ConstantTimeCompare([]byte(p.state), []byte(state)) == 0 {
return nil, fmt.Errorf("invalid state")
}
code := query.Get(queryCode)
if code == "" {
return nil, fmt.Errorf("missing code")
}
return p.oAuthConfig.Exchange(
req.Context(),
code,
oauth2.SetAuthURLParam("code_verifier", p.codeVerifier),
)
}
func (p *PKCEAuthorizationFlow) parseOAuthToken(token *oauth2.Token) (TokenInfo, error) {
tokenInfo := TokenInfo{
AccessToken: token.AccessToken,
RefreshToken: token.RefreshToken,
TokenType: token.TokenType,
ExpiresIn: token.Expiry.Second(),
UseIDToken: p.providerConfig.UseIDToken,
}
if idToken, ok := token.Extra("id_token").(string); ok {
tokenInfo.IDToken = idToken
}
// if a provider doesn't support an audience, use the Client ID for token verification
audience := p.providerConfig.Audience
if audience == "" {
audience = p.providerConfig.ClientID
}
if err := isValidAccessToken(tokenInfo.GetTokenToUse(), audience); err != nil {
return TokenInfo{}, fmt.Errorf("validate access token failed with error: %v", err)
}
return tokenInfo, nil
}
func createCodeChallenge(codeVerifier string) string {
sha2 := sha256.Sum256([]byte(codeVerifier))
return base64.RawURLEncoding.EncodeToString(sha2[:])
}
// isRedirectURLPortUsed checks if the port used in the redirect URL is in use.
func isRedirectURLPortUsed(redirectURL string) bool {
parsedURL, err := url.Parse(redirectURL)
if err != nil {
log.Errorf("failed to parse redirect URL: %v", err)
return true
}
addr := fmt.Sprintf(":%s", parsedURL.Port())
conn, err := net.DialTimeout("tcp", addr, 3*time.Second)
if err != nil {
return false
}
defer func() {
if err := conn.Close(); err != nil {
log.Errorf("error while closing the connection: %v", err)
}
}()
return true
}
func renderPKCEFlowTmpl(w http.ResponseWriter, authError error) {
tmpl, err := template.New("pkce-auth-flow").Parse(templates.PKCEAuthMsgTmpl)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
data := make(map[string]string)
if authError != nil {
data["Error"] = authError.Error()
}
if err := tmpl.Execute(w, data); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
}
}