package headscale import ( "bytes" "context" "crypto/rand" "encoding/hex" "errors" "fmt" "html/template" "net/http" "strings" "time" "github.com/coreos/go-oidc/v3/oidc" "github.com/gin-gonic/gin" "github.com/rs/zerolog/log" "golang.org/x/oauth2" "tailscale.com/types/key" ) const ( randomByteSize = 16 ) type IDTokenClaims struct { Name string `json:"name,omitempty"` Groups []string `json:"groups,omitempty"` Email string `json:"email"` Username string `json:"preferred_username,omitempty"` } func (h *Headscale) initOIDC() error { var err error // grab oidc config if it hasn't been already if h.oauth2Config == nil { h.oidcProvider, err = oidc.NewProvider(context.Background(), h.cfg.OIDC.Issuer) if err != nil { log.Error(). Err(err). Caller(). Msgf("Could not retrieve OIDC Config: %s", err.Error()) return err } h.oauth2Config = &oauth2.Config{ ClientID: h.cfg.OIDC.ClientID, ClientSecret: h.cfg.OIDC.ClientSecret, Endpoint: h.oidcProvider.Endpoint(), RedirectURL: fmt.Sprintf( "%s/oidc/callback", strings.TrimSuffix(h.cfg.ServerURL, "/"), ), Scopes: []string{oidc.ScopeOpenID, "profile", "email"}, } } return nil } // RegisterOIDC redirects to the OIDC provider for authentication // Puts machine key in cache so the callback can retrieve it using the oidc state param // Listens in /oidc/register/:nKey. func (h *Headscale) RegisterOIDC(ctx *gin.Context) { nodeKeyStr := ctx.Param("nkey") if nodeKeyStr == "" { ctx.String(http.StatusBadRequest, "Wrong params") return } log.Trace(). Caller(). Str("node_key", nodeKeyStr). Msg("Received oidc register call") randomBlob := make([]byte, randomByteSize) if _, err := rand.Read(randomBlob); err != nil { log.Error(). Caller(). Msg("could not read 16 bytes from rand") ctx.String(http.StatusInternalServerError, "could not read 16 bytes from rand") return } stateStr := hex.EncodeToString(randomBlob)[:32] // place the machine key into the state cache, so it can be retrieved later h.registrationCache.Set(stateStr, nodeKeyStr, registerCacheExpiration) authURL := h.oauth2Config.AuthCodeURL(stateStr) log.Debug().Msgf("Redirecting to %s for authentication", authURL) ctx.Redirect(http.StatusFound, authURL) } type oidcCallbackTemplateConfig struct { User string Verb string } var oidcCallbackTemplate = template.Must( template.New("oidccallback").Parse(`

headscale

{{.Verb}} as {{.User}}, you can now close this window.

`), ) // OIDCCallback handles the callback from the OIDC endpoint // Retrieves the nkey from the state cache and adds the machine to the users email namespace // TODO: A confirmation page for new machines should be added to avoid phishing vulnerabilities // TODO: Add groups information from OIDC tokens into machine HostInfo // Listens in /oidc/callback. func (h *Headscale) OIDCCallback(ctx *gin.Context) { code := ctx.Query("code") state := ctx.Query("state") if code == "" || state == "" { ctx.String(http.StatusBadRequest, "Wrong params") return } oauth2Token, err := h.oauth2Config.Exchange(context.Background(), code) if err != nil { log.Error(). Err(err). Caller(). Msg("Could not exchange code for token") ctx.String(http.StatusBadRequest, "Could not exchange code for token") return } log.Trace(). Caller(). Str("code", code). Str("state", state). Msg("Got oidc callback") rawIDToken, rawIDTokenOK := oauth2Token.Extra("id_token").(string) if !rawIDTokenOK { ctx.String(http.StatusBadRequest, "Could not extract ID Token") return } verifier := h.oidcProvider.Verifier(&oidc.Config{ClientID: h.cfg.OIDC.ClientID}) idToken, err := verifier.Verify(context.Background(), rawIDToken) if err != nil { log.Error(). Err(err). Caller(). Msg("failed to verify id token") ctx.String(http.StatusBadRequest, "Failed to verify id token") return } // TODO: we can use userinfo at some point to grab additional information about the user (groups membership, etc) // userInfo, err := oidcProvider.UserInfo(context.Background(), oauth2.StaticTokenSource(oauth2Token)) // if err != nil { // c.String(http.StatusBadRequest, fmt.Sprintf("Failed to retrieve userinfo")) // return // } // Extract custom claims var claims IDTokenClaims if err = idToken.Claims(&claims); err != nil { log.Error(). Err(err). Caller(). Msg("Failed to decode id token claims") ctx.String( http.StatusBadRequest, "Failed to decode id token claims", ) return } // retrieve machinekey from state cache nodeKeyIf, machineKeyFound := h.registrationCache.Get(state) if !machineKeyFound { log.Error(). Msg("requested node state key expired before authorisation completed") ctx.String(http.StatusBadRequest, "state has expired") return } nodeKeyFromCache, nodeKeyOK := nodeKeyIf.(string) var nodeKey key.NodePublic err = nodeKey.UnmarshalText( []byte(NodePublicKeyEnsurePrefix(nodeKeyFromCache)), ) if err != nil { log.Error(). Msg("could not parse node public key") ctx.String(http.StatusBadRequest, "could not parse public key") return } if !nodeKeyOK { log.Error().Msg("could not get node key from cache") ctx.String( http.StatusInternalServerError, "could not get machine key from cache", ) return } // retrieve machine information if it exist // The error is not important, because if it does not // exist, then this is a new machine and we will move // on to registration. machine, _ := h.GetMachineByNodeKeys(nodeKey, key.NodePublic{}) if machine != nil { log.Trace(). Caller(). Str("machine", machine.Name). Msg("machine already registered, reauthenticating") h.RefreshMachine(machine, time.Time{}) var content bytes.Buffer if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{ User: claims.Email, Verb: "Reauthenticated", }); err != nil { log.Error(). Str("func", "OIDCCallback"). Str("type", "reauthenticate"). Err(err). Msg("Could not render OIDC callback template") ctx.Data( http.StatusInternalServerError, "text/html; charset=utf-8", []byte("Could not render OIDC callback template"), ) } ctx.Data(http.StatusOK, "text/html; charset=utf-8", content.Bytes()) return } namespaceName, err := NormalizeToFQDNRules( claims.Email, h.cfg.OIDC.StripEmaildomain, ) if err != nil { log.Error().Err(err).Caller().Msgf("couldn't normalize email") ctx.String( http.StatusInternalServerError, "couldn't normalize email", ) return } // register the machine if it's new log.Debug().Msg("Registering new machine after successful callback") namespace, err := h.GetNamespace(namespaceName) if errors.Is(err, errNamespaceNotFound) { namespace, err = h.CreateNamespace(namespaceName) if err != nil { log.Error(). Err(err). Caller(). Msgf("could not create new namespace '%s'", namespaceName) ctx.String( http.StatusInternalServerError, "could not create new namespace", ) return } } else if err != nil { log.Error(). Caller(). Err(err). Str("namespace", namespaceName). Msg("could not find or create namespace") ctx.String( http.StatusInternalServerError, "could not find or create namespace", ) return } nodeKeyStr := NodePublicKeyStripPrefix(nodeKey) _, err = h.RegisterMachineFromAuthCallback( nodeKeyStr, namespace.Name, RegisterMethodOIDC, ) if err != nil { log.Error(). Caller(). Err(err). Msg("could not register machine") ctx.String( http.StatusInternalServerError, "could not register machine", ) return } var content bytes.Buffer if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{ User: claims.Email, Verb: "Authenticated", }); err != nil { log.Error(). Str("func", "OIDCCallback"). Str("type", "authenticate"). Err(err). Msg("Could not render OIDC callback template") ctx.Data( http.StatusInternalServerError, "text/html; charset=utf-8", []byte("Could not render OIDC callback template"), ) } ctx.Data(http.StatusOK, "text/html; charset=utf-8", content.Bytes()) }