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google.go
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google.go
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// Package google implements logging in through Google's OpenID Connect provider.
package google
import (
"context"
"errors"
"fmt"
"log/slog"
"net/http"
"os"
"strings"
"time"
"cloud.google.com/go/compute/metadata"
"github.com/coreos/go-oidc/v3/oidc"
"golang.org/x/exp/slices"
"golang.org/x/oauth2"
"golang.org/x/oauth2/google"
admin "google.golang.org/api/admin/directory/v1"
"google.golang.org/api/impersonate"
"google.golang.org/api/option"
"github.com/dexidp/dex/connector"
pkg_groups "github.com/dexidp/dex/pkg/groups"
)
const (
issuerURL = "https://accounts.google.com"
wildcardDomainToAdminEmail = "*"
)
// Config holds configuration options for Google logins.
type Config struct {
ClientID string `json:"clientID"`
ClientSecret string `json:"clientSecret"`
RedirectURI string `json:"redirectURI"`
Scopes []string `json:"scopes"` // defaults to "profile" and "email"
// Optional list of whitelisted domains
// If this field is nonempty, only users from a listed domain will be allowed to log in
HostedDomains []string `json:"hostedDomains"`
// Optional list of whitelisted groups
// If this field is nonempty, only users from a listed group will be allowed to log in
Groups []string `json:"groups"`
// Optional path to service account json
// If nonempty, and groups claim is made, will use authentication from file to
// check groups with the admin directory api
ServiceAccountFilePath string `json:"serviceAccountFilePath"`
// Deprecated: Use DomainToAdminEmail
AdminEmail string
// Required if ServiceAccountFilePath
// The map workspace domain to email of a GSuite super user which the service account will impersonate
// when listing groups
DomainToAdminEmail map[string]string
// If this field is true, fetch direct group membership and transitive group membership
FetchTransitiveGroupMembership bool `json:"fetchTransitiveGroupMembership"`
// Optional value for the prompt parameter, defaults to consent when offline_access
// scope is requested
PromptType *string `json:"promptType"`
}
// Open returns a connector which can be used to login users through Google.
func (c *Config) Open(id string, logger *slog.Logger) (conn connector.Connector, err error) {
logger = logger.With(slog.Group("connector", "type", "google", "id", id))
if c.AdminEmail != "" {
logger.Warn(`use "domainToAdminEmail.*" option instead of "adminEmail"`, "deprecated", true)
if c.DomainToAdminEmail == nil {
c.DomainToAdminEmail = make(map[string]string)
}
c.DomainToAdminEmail[wildcardDomainToAdminEmail] = c.AdminEmail
}
ctx, cancel := context.WithCancel(context.Background())
provider, err := oidc.NewProvider(ctx, issuerURL)
if err != nil {
cancel()
return nil, fmt.Errorf("failed to get provider: %v", err)
}
scopes := []string{oidc.ScopeOpenID}
if len(c.Scopes) > 0 {
scopes = append(scopes, c.Scopes...)
} else {
scopes = append(scopes, "profile", "email")
}
adminSrv := make(map[string]*admin.Service)
// We know impersonation is required when using a service account credential
// TODO: or is it?
if len(c.DomainToAdminEmail) == 0 && c.ServiceAccountFilePath != "" {
cancel()
return nil, fmt.Errorf("directory service requires the domainToAdminEmail option to be configured")
}
if (len(c.DomainToAdminEmail) > 0) || slices.Contains(scopes, "groups") {
for domain, adminEmail := range c.DomainToAdminEmail {
srv, err := createDirectoryService(c.ServiceAccountFilePath, adminEmail, logger)
if err != nil {
cancel()
return nil, fmt.Errorf("could not create directory service: %v", err)
}
adminSrv[domain] = srv
}
}
promptType := "consent"
if c.PromptType != nil {
promptType = *c.PromptType
}
clientID := c.ClientID
return &googleConnector{
redirectURI: c.RedirectURI,
oauth2Config: &oauth2.Config{
ClientID: clientID,
ClientSecret: c.ClientSecret,
Endpoint: provider.Endpoint(),
Scopes: scopes,
RedirectURL: c.RedirectURI,
},
verifier: provider.Verifier(
&oidc.Config{ClientID: clientID},
),
logger: logger,
cancel: cancel,
hostedDomains: c.HostedDomains,
groups: c.Groups,
serviceAccountFilePath: c.ServiceAccountFilePath,
domainToAdminEmail: c.DomainToAdminEmail,
fetchTransitiveGroupMembership: c.FetchTransitiveGroupMembership,
adminSrv: adminSrv,
promptType: promptType,
}, nil
}
var (
_ connector.CallbackConnector = (*googleConnector)(nil)
_ connector.RefreshConnector = (*googleConnector)(nil)
)
type googleConnector struct {
redirectURI string
oauth2Config *oauth2.Config
verifier *oidc.IDTokenVerifier
cancel context.CancelFunc
logger *slog.Logger
hostedDomains []string
groups []string
serviceAccountFilePath string
domainToAdminEmail map[string]string
fetchTransitiveGroupMembership bool
adminSrv map[string]*admin.Service
promptType string
}
func (c *googleConnector) Close() error {
c.cancel()
return nil
}
func (c *googleConnector) LoginURL(s connector.Scopes, callbackURL, state string) (string, error) {
if c.redirectURI != callbackURL {
return "", fmt.Errorf("expected callback URL %q did not match the URL in the config %q", callbackURL, c.redirectURI)
}
var opts []oauth2.AuthCodeOption
if len(c.hostedDomains) > 0 {
preferredDomain := c.hostedDomains[0]
if len(c.hostedDomains) > 1 {
preferredDomain = "*"
}
opts = append(opts, oauth2.SetAuthURLParam("hd", preferredDomain))
}
if s.OfflineAccess {
opts = append(opts, oauth2.AccessTypeOffline, oauth2.SetAuthURLParam("prompt", c.promptType))
}
return c.oauth2Config.AuthCodeURL(state, opts...), nil
}
type oauth2Error struct {
error string
errorDescription string
}
func (e *oauth2Error) Error() string {
if e.errorDescription == "" {
return e.error
}
return e.error + ": " + e.errorDescription
}
func (c *googleConnector) HandleCallback(s connector.Scopes, r *http.Request) (identity connector.Identity, err error) {
q := r.URL.Query()
if errType := q.Get("error"); errType != "" {
return identity, &oauth2Error{errType, q.Get("error_description")}
}
token, err := c.oauth2Config.Exchange(r.Context(), q.Get("code"))
if err != nil {
return identity, fmt.Errorf("google: failed to get token: %v", err)
}
return c.createIdentity(r.Context(), identity, s, token)
}
func (c *googleConnector) Refresh(ctx context.Context, s connector.Scopes, identity connector.Identity) (connector.Identity, error) {
t := &oauth2.Token{
RefreshToken: string(identity.ConnectorData),
Expiry: time.Now().Add(-time.Hour),
}
token, err := c.oauth2Config.TokenSource(ctx, t).Token()
if err != nil {
return identity, fmt.Errorf("google: failed to get token: %v", err)
}
return c.createIdentity(ctx, identity, s, token)
}
func (c *googleConnector) createIdentity(ctx context.Context, identity connector.Identity, s connector.Scopes, token *oauth2.Token) (connector.Identity, error) {
rawIDToken, ok := token.Extra("id_token").(string)
if !ok {
return identity, errors.New("google: no id_token in token response")
}
idToken, err := c.verifier.Verify(ctx, rawIDToken)
if err != nil {
return identity, fmt.Errorf("google: failed to verify ID Token: %v", err)
}
var claims struct {
Username string `json:"name"`
Email string `json:"email"`
EmailVerified bool `json:"email_verified"`
HostedDomain string `json:"hd"`
}
if err := idToken.Claims(&claims); err != nil {
return identity, fmt.Errorf("oidc: failed to decode claims: %v", err)
}
if len(c.hostedDomains) > 0 {
found := false
for _, domain := range c.hostedDomains {
if claims.HostedDomain == domain {
found = true
break
}
}
if !found {
return identity, fmt.Errorf("oidc: unexpected hd claim %v", claims.HostedDomain)
}
}
var groups []string
if s.Groups && len(c.adminSrv) > 0 {
checkedGroups := make(map[string]struct{})
groups, err = c.getGroups(claims.Email, c.fetchTransitiveGroupMembership, checkedGroups)
if err != nil {
return identity, fmt.Errorf("google: could not retrieve groups: %v", err)
}
if len(c.groups) > 0 {
groups = pkg_groups.Filter(groups, c.groups)
if len(groups) == 0 {
return identity, fmt.Errorf("google: user %q is not in any of the required groups", claims.Username)
}
}
}
identity = connector.Identity{
UserID: idToken.Subject,
Username: claims.Username,
Email: claims.Email,
EmailVerified: claims.EmailVerified,
ConnectorData: []byte(token.RefreshToken),
Groups: groups,
}
return identity, nil
}
// getGroups creates a connection to the admin directory service and lists
// all groups the user is a member of
func (c *googleConnector) getGroups(email string, fetchTransitiveGroupMembership bool, checkedGroups map[string]struct{}) ([]string, error) {
var userGroups []string
var err error
groupsList := &admin.Groups{}
domain := c.extractDomainFromEmail(email)
adminSrv, err := c.findAdminService(domain)
if err != nil {
return nil, err
}
for {
groupsList, err = adminSrv.Groups.List().
UserKey(email).PageToken(groupsList.NextPageToken).Do()
if err != nil {
return nil, fmt.Errorf("could not list groups: %v", err)
}
for _, group := range groupsList.Groups {
if _, exists := checkedGroups[group.Email]; exists {
continue
}
checkedGroups[group.Email] = struct{}{}
// TODO (joelspeed): Make desired group key configurable
userGroups = append(userGroups, group.Email)
if !fetchTransitiveGroupMembership {
continue
}
// getGroups takes a user's email/alias as well as a group's email/alias
transitiveGroups, err := c.getGroups(group.Email, fetchTransitiveGroupMembership, checkedGroups)
if err != nil {
return nil, fmt.Errorf("could not list transitive groups: %v", err)
}
userGroups = append(userGroups, transitiveGroups...)
}
if groupsList.NextPageToken == "" {
break
}
}
return userGroups, nil
}
func (c *googleConnector) findAdminService(domain string) (*admin.Service, error) {
adminSrv, ok := c.adminSrv[domain]
if !ok {
adminSrv, ok = c.adminSrv[wildcardDomainToAdminEmail]
c.logger.Debug("using wildcard admin email to fetch groups", "admin_email", c.domainToAdminEmail[wildcardDomainToAdminEmail])
}
if !ok {
return nil, fmt.Errorf("unable to find super admin email, domainToAdminEmail for domain: %s not set, %s is also empty", domain, wildcardDomainToAdminEmail)
}
return adminSrv, nil
}
// extracts the domain name from an email input. If the email is valid, it returns the domain name after the "@" symbol.
// However, in the case of a broken or invalid email, it returns a wildcard symbol.
func (c *googleConnector) extractDomainFromEmail(email string) string {
at := strings.LastIndex(email, "@")
if at >= 0 {
_, domain := email[:at], email[at+1:]
return domain
}
return wildcardDomainToAdminEmail
}
// getCredentialsFromFilePath reads and returns the service account credentials from the file at the provided path.
// If an error occurs during the read, it is returned.
func getCredentialsFromFilePath(serviceAccountFilePath string) ([]byte, error) {
jsonCredentials, err := os.ReadFile(serviceAccountFilePath)
if err != nil {
return nil, fmt.Errorf("error reading credentials from file: %v", err)
}
return jsonCredentials, nil
}
// getCredentialsFromDefault retrieves the application's default credentials.
// If the default credential is empty, it attempts to create a new service with metadata credentials.
// If successful, it returns the service and nil error.
// If unsuccessful, it returns the error and a nil service.
func getCredentialsFromDefault(ctx context.Context, email string, logger *slog.Logger) ([]byte, *admin.Service, error) {
credential, err := google.FindDefaultCredentials(ctx)
if err != nil {
return nil, nil, fmt.Errorf("failed to fetch application default credentials: %w", err)
}
if credential.JSON == nil {
logger.Info("JSON is empty, using flow for GCE")
service, err := createServiceWithMetadataServer(ctx, email, logger)
if err != nil {
return nil, nil, err
}
return nil, service, nil
}
return credential.JSON, nil, nil
}
// createServiceWithMetadataServer creates a new service using metadata server.
// If an error occurs during the process, it is returned along with a nil service.
func createServiceWithMetadataServer(ctx context.Context, adminEmail string, logger *slog.Logger) (*admin.Service, error) {
serviceAccountEmail, err := metadata.EmailWithContext(ctx, "default")
logger.Info("discovered serviceAccountEmail", "email", serviceAccountEmail)
if err != nil {
return nil, fmt.Errorf("unable to get service account email from metadata server: %v", err)
}
config := impersonate.CredentialsConfig{
TargetPrincipal: serviceAccountEmail,
Scopes: []string{admin.AdminDirectoryGroupReadonlyScope},
Lifetime: 0,
Subject: adminEmail,
}
tokenSource, err := impersonate.CredentialsTokenSource(ctx, config)
if err != nil {
return nil, fmt.Errorf("unable to impersonate with %s, error: %v", adminEmail, err)
}
return admin.NewService(ctx, option.WithHTTPClient(oauth2.NewClient(ctx, tokenSource)))
}
// createDirectoryService sets up super user impersonation and creates an admin client for calling
// the google admin api. If no serviceAccountFilePath is defined, the application default credential
// is used.
func createDirectoryService(serviceAccountFilePath, email string, logger *slog.Logger) (service *admin.Service, err error) {
var jsonCredentials []byte
ctx := context.Background()
if serviceAccountFilePath == "" {
logger.Warn("the application default credential is used since the service account file path is not used")
jsonCredentials, service, err = getCredentialsFromDefault(ctx, email, logger)
if err != nil {
return
}
if service != nil {
return
}
} else {
jsonCredentials, err = getCredentialsFromFilePath(serviceAccountFilePath)
if err != nil {
return
}
}
config, err := google.JWTConfigFromJSON(jsonCredentials, admin.AdminDirectoryGroupReadonlyScope)
if err != nil {
return nil, fmt.Errorf("unable to parse client secret file to config: %v", err)
}
// Only attempt impersonation when there is a user configured
if email != "" {
config.Subject = email
}
return admin.NewService(ctx, option.WithHTTPClient(config.Client(ctx)))
}