package headscale import ( "bytes" "context" "crypto/rand" "encoding/hex" "errors" "fmt" "html/template" "net/http" "regexp" "strings" "time" "github.com/coreos/go-oidc/v3/oidc" "github.com/gin-gonic/gin" "github.com/patrickmn/go-cache" "github.com/rs/zerolog/log" "golang.org/x/oauth2" "gorm.io/gorm" "tailscale.com/types/key" ) const ( oidcStateCacheExpiration = time.Minute * 5 oidcStateCacheCleanupInterval = time.Minute * 10 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"}, } } // init the state cache if it hasn't been already if h.oidcStateCache == nil { h.oidcStateCache = cache.New( oidcStateCacheExpiration, oidcStateCacheCleanupInterval, ) } 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/:mKey. func (h *Headscale) RegisterOIDC(ctx *gin.Context) { machineKeyStr := ctx.Param("mkey") if machineKeyStr == "" { ctx.String(http.StatusBadRequest, "Wrong params") return } log.Trace(). Caller(). Str("machine_key", machineKeyStr). 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.oidcStateCache.Set(stateStr, machineKeyStr, oidcStateCacheExpiration) 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(`<html> <body> <h1>headscale</h1> <p> {{.Verb}} as {{.User}}, you can now close this window. </p> </body> </html>`), ) // OIDCCallback handles the callback from the OIDC endpoint // Retrieves the mkey 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 { 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 machineKeyIf, machineKeyFound := h.oidcStateCache.Get(state) if !machineKeyFound { log.Error(). Msg("requested machine state key expired before authorisation completed") ctx.String(http.StatusBadRequest, "state has expired") return } machineKeyStr, machineKeyOK := machineKeyIf.(string) var machineKey key.MachinePublic err = machineKey.UnmarshalText([]byte(MachinePublicKeyEnsurePrefix(machineKeyStr))) if err != nil { log.Error(). Msg("could not parse machine public key") ctx.String(http.StatusBadRequest, "could not parse public key") return } if !machineKeyOK { log.Error().Msg("could not get machine key from cache") ctx.String( http.StatusInternalServerError, "could not get machine key from cache", ) return } // TODO(kradalby): Currently, if it fails to find a requested expiry, non will be set requestedTime := time.Time{} if requestedTimeIf, found := h.requestedExpiryCache.Get(machineKey.String()); found { if reqTime, ok := requestedTimeIf.(time.Time); ok { requestedTime = reqTime } } // retrieve machine information machine, err := h.GetMachineByMachineKey(machineKey) if err != nil { log.Error().Msg("machine key not found in database") ctx.String( http.StatusInternalServerError, "could not get machine info from database", ) return } if machine.isRegistered() { log.Trace(). Caller(). Str("machine", machine.Name). Msg("machine already registered, reauthenticating") h.RefreshMachine(machine, requestedTime) 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 } now := time.Now().UTC() if namespaceName, ok := h.getNamespaceFromEmail(claims.Email); ok { // register the machine if it's new if !machine.Registered { log.Debug().Msg("Registering new machine after successful callback") namespace, err := h.GetNamespace(namespaceName) if errors.Is(err, gorm.ErrRecordNotFound) { 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 } ip, err := h.getAvailableIP() if err != nil { log.Error(). Caller(). Err(err). Msg("could not get an IP from the pool") ctx.String( http.StatusInternalServerError, "could not get an IP from the pool", ) return } machine.IPAddress = ip.String() machine.NamespaceID = namespace.ID machine.Registered = true machine.RegisterMethod = RegisterMethodOIDC machine.LastSuccessfulUpdate = &now machine.Expiry = &requestedTime h.db.Save(&machine) } 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()) return } log.Error(). Caller(). Str("email", claims.Email). Str("username", claims.Username). Str("machine", machine.Name). Msg("Email could not be mapped to a namespace") ctx.String( http.StatusBadRequest, "email from claim could not be mapped to a namespace", ) } // getNamespaceFromEmail passes the users email through a list of "matchers" // and iterates through them until it matches and returns a namespace. // If no match is found, an empty string will be returned. // TODO(kradalby): golang Maps key order is not stable, so this list is _not_ deterministic. Find a way to make the list of keys stable, preferably in the order presented in a users configuration. func (h *Headscale) getNamespaceFromEmail(email string) (string, bool) { for match, namespace := range h.cfg.OIDC.MatchMap { regex := regexp.MustCompile(match) if regex.MatchString(email) { return namespace, true } } return "", false }