// Copyright 2015 Matthew Holt and The Caddy Authors // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package caddy import ( "bytes" "context" "crypto" "crypto/tls" "crypto/x509" "encoding/base64" "encoding/json" "errors" "expvar" "fmt" "hash" "hash/fnv" "io" "net" "net/http" "net/http/pprof" "net/url" "os" "path" "regexp" "strconv" "strings" "sync" "time" "github.com/caddyserver/certmagic" "github.com/prometheus/client_golang/prometheus" "go.uber.org/zap" "go.uber.org/zap/zapcore" ) func init() { // The hard-coded default `DefaultAdminListen` can be overidden // by setting the `CADDY_ADMIN` environment variable. // The environment variable may be used by packagers to change // the default admin address to something more appropriate for // that platform. See #5317 for discussion. if env, exists := os.LookupEnv("CADDY_ADMIN"); exists { DefaultAdminListen = env } } // AdminConfig configures Caddy's API endpoint, which is used // to manage Caddy while it is running. type AdminConfig struct { // If true, the admin endpoint will be completely disabled. // Note that this makes any runtime changes to the config // impossible, since the interface to do so is through the // admin endpoint. Disabled bool `json:"disabled,omitempty"` // The address to which the admin endpoint's listener should // bind itself. Can be any single network address that can be // parsed by Caddy. Accepts placeholders. // Default: the value of the `CADDY_ADMIN` environment variable, // or `localhost:2019` otherwise. // // Remember: When changing this value through a config reload, // be sure to use the `--address` CLI flag to specify the current // admin address if the currently-running admin endpoint is not // the default address. Listen string `json:"listen,omitempty"` // If true, CORS headers will be emitted, and requests to the // API will be rejected if their `Host` and `Origin` headers // do not match the expected value(s). Use `origins` to // customize which origins/hosts are allowed. If `origins` is // not set, the listen address is the only value allowed by // default. Enforced only on local (plaintext) endpoint. EnforceOrigin bool `json:"enforce_origin,omitempty"` // The list of allowed origins/hosts for API requests. Only needed // if accessing the admin endpoint from a host different from the // socket's network interface or if `enforce_origin` is true. If not // set, the listener address will be the default value. If set but // empty, no origins will be allowed. Enforced only on local // (plaintext) endpoint. Origins []string `json:"origins,omitempty"` // Options pertaining to configuration management. Config *ConfigSettings `json:"config,omitempty"` // Options that establish this server's identity. Identity refers to // credentials which can be used to uniquely identify and authenticate // this server instance. This is required if remote administration is // enabled (but does not require remote administration to be enabled). // Default: no identity management. Identity *IdentityConfig `json:"identity,omitempty"` // Options pertaining to remote administration. By default, remote // administration is disabled. If enabled, identity management must // also be configured, as that is how the endpoint is secured. // See the neighboring "identity" object. // // EXPERIMENTAL: This feature is subject to change. Remote *RemoteAdmin `json:"remote,omitempty"` // Holds onto the routers so that we can later provision them // if they require provisioning. routers []AdminRouter } // ConfigSettings configures the management of configuration. type ConfigSettings struct { // Whether to keep a copy of the active config on disk. Default is true. // Note that "pulled" dynamic configs (using the neighboring "load" module) // are not persisted; only configs that are pushed to Caddy get persisted. Persist *bool `json:"persist,omitempty"` // Loads a new configuration. This is helpful if your configs are // managed elsewhere and you want Caddy to pull its config dynamically // when it starts. The pulled config completely replaces the current // one, just like any other config load. It is an error if a pulled // config is configured to pull another config without a load_delay, // as this creates a tight loop. // // EXPERIMENTAL: Subject to change. LoadRaw json.RawMessage `json:"load,omitempty" caddy:"namespace=caddy.config_loaders inline_key=module"` // The duration after which to load config. If set, config will be pulled // from the config loader after this duration. A delay is required if a // dynamically-loaded config is configured to load yet another config. To // load configs on a regular interval, ensure this value is set the same // on all loaded configs; it can also be variable if needed, and to stop // the loop, simply remove dynamic config loading from the next-loaded // config. // // EXPERIMENTAL: Subject to change. LoadDelay Duration `json:"load_delay,omitempty"` } // IdentityConfig configures management of this server's identity. An identity // consists of credentials that uniquely verify this instance; for example, // TLS certificates (public + private key pairs). type IdentityConfig struct { // List of names or IP addresses which refer to this server. // Certificates will be obtained for these identifiers so // secure TLS connections can be made using them. Identifiers []string `json:"identifiers,omitempty"` // Issuers that can provide this admin endpoint its identity // certificate(s). Default: ACME issuers configured for // ZeroSSL and Let's Encrypt. Be sure to change this if you // require credentials for private identifiers. IssuersRaw []json.RawMessage `json:"issuers,omitempty" caddy:"namespace=tls.issuance inline_key=module"` issuers []certmagic.Issuer } // RemoteAdmin enables and configures remote administration. If enabled, // a secure listener enforcing mutual TLS authentication will be started // on a different port from the standard plaintext admin server. // // This endpoint is secured using identity management, which must be // configured separately (because identity management does not depend // on remote administration). See the admin/identity config struct. // // EXPERIMENTAL: Subject to change. type RemoteAdmin struct { // The address on which to start the secure listener. Accepts placeholders. // Default: :2021 Listen string `json:"listen,omitempty"` // List of access controls for this secure admin endpoint. // This configures TLS mutual authentication (i.e. authorized // client certificates), but also application-layer permissions // like which paths and methods each identity is authorized for. AccessControl []*AdminAccess `json:"access_control,omitempty"` } // AdminAccess specifies what permissions an identity or group // of identities are granted. type AdminAccess struct { // Base64-encoded DER certificates containing public keys to accept. // (The contents of PEM certificate blocks are base64-encoded DER.) // Any of these public keys can appear in any part of a verified chain. PublicKeys []string `json:"public_keys,omitempty"` // Limits what the associated identities are allowed to do. // If unspecified, all permissions are granted. Permissions []AdminPermissions `json:"permissions,omitempty"` publicKeys []crypto.PublicKey } // AdminPermissions specifies what kinds of requests are allowed // to be made to the admin endpoint. type AdminPermissions struct { // The API paths allowed. Paths are simple prefix matches. // Any subpath of the specified paths will be allowed. Paths []string `json:"paths,omitempty"` // The HTTP methods allowed for the given paths. Methods []string `json:"methods,omitempty"` } // newAdminHandler reads admin's config and returns an http.Handler suitable // for use in an admin endpoint server, which will be listening on listenAddr. func (admin *AdminConfig) newAdminHandler(addr NetworkAddress, remote bool) adminHandler { muxWrap := adminHandler{mux: http.NewServeMux()} // secure the local or remote endpoint respectively if remote { muxWrap.remoteControl = admin.Remote } else { muxWrap.enforceHost = !addr.isWildcardInterface() muxWrap.allowedOrigins = admin.allowedOrigins(addr) muxWrap.enforceOrigin = admin.EnforceOrigin } addRouteWithMetrics := func(pattern string, handlerLabel string, h http.Handler) { labels := prometheus.Labels{"path": pattern, "handler": handlerLabel} h = instrumentHandlerCounter( adminMetrics.requestCount.MustCurryWith(labels), h, ) muxWrap.mux.Handle(pattern, h) } // addRoute just calls muxWrap.mux.Handle after // wrapping the handler with error handling addRoute := func(pattern string, handlerLabel string, h AdminHandler) { wrapper := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { err := h.ServeHTTP(w, r) if err != nil { labels := prometheus.Labels{ "path": pattern, "handler": handlerLabel, "method": strings.ToUpper(r.Method), } adminMetrics.requestErrors.With(labels).Inc() } muxWrap.handleError(w, r, err) }) addRouteWithMetrics(pattern, handlerLabel, wrapper) } const handlerLabel = "admin" // register standard config control endpoints addRoute("/"+rawConfigKey+"/", handlerLabel, AdminHandlerFunc(handleConfig)) addRoute("/id/", handlerLabel, AdminHandlerFunc(handleConfigID)) addRoute("/stop", handlerLabel, AdminHandlerFunc(handleStop)) // register debugging endpoints addRouteWithMetrics("/debug/pprof/", handlerLabel, http.HandlerFunc(pprof.Index)) addRouteWithMetrics("/debug/pprof/cmdline", handlerLabel, http.HandlerFunc(pprof.Cmdline)) addRouteWithMetrics("/debug/pprof/profile", handlerLabel, http.HandlerFunc(pprof.Profile)) addRouteWithMetrics("/debug/pprof/symbol", handlerLabel, http.HandlerFunc(pprof.Symbol)) addRouteWithMetrics("/debug/pprof/trace", handlerLabel, http.HandlerFunc(pprof.Trace)) addRouteWithMetrics("/debug/vars", handlerLabel, expvar.Handler()) // register third-party module endpoints for _, m := range GetModules("admin.api") { router := m.New().(AdminRouter) handlerLabel := m.ID.Name() for _, route := range router.Routes() { addRoute(route.Pattern, handlerLabel, route.Handler) } admin.routers = append(admin.routers, router) } return muxWrap } // provisionAdminRouters provisions all the router modules // in the admin.api namespace that need provisioning. func (admin *AdminConfig) provisionAdminRouters(ctx Context) error { for _, router := range admin.routers { provisioner, ok := router.(Provisioner) if !ok { continue } err := provisioner.Provision(ctx) if err != nil { return err } } // We no longer need the routers once provisioned, allow for GC admin.routers = nil return nil } // allowedOrigins returns a list of origins that are allowed. // If admin.Origins is nil (null), the provided listen address // will be used as the default origin. If admin.Origins is // empty, no origins will be allowed, effectively bricking the // endpoint for non-unix-socket endpoints, but whatever. func (admin AdminConfig) allowedOrigins(addr NetworkAddress) []*url.URL { uniqueOrigins := make(map[string]struct{}) for _, o := range admin.Origins { uniqueOrigins[o] = struct{}{} } if admin.Origins == nil { if addr.isLoopback() { if addr.IsUnixNetwork() { // RFC 2616, Section 14.26: // "A client MUST include a Host header field in all HTTP/1.1 request // messages. If the requested URI does not include an Internet host // name for the service being requested, then the Host header field MUST // be given with an empty value." // // UPDATE July 2023: Go broke this by patching a minor security bug in 1.20.6. // Understandable, but frustrating. See: // https://github.com/golang/go/issues/60374 // See also the discussion here: // https://github.com/golang/go/issues/61431 // // We can no longer conform to RFC 2616 Section 14.26 from either Go or curl // in purity. (Curl allowed no host between 7.40 and 7.50, but now requires a // bogus host; see https://superuser.com/a/925610.) If we disable Host/Origin // security checks, the infosec community assures me that it is secure to do // so, because: // 1) Browsers do not allow access to unix sockets // 2) DNS is irrelevant to unix sockets // // I am not quite ready to trust either of those external factors, so instead // of disabling Host/Origin checks, we now allow specific Host values when // accessing the admin endpoint over unix sockets. I definitely don't trust // DNS (e.g. I don't trust 'localhost' to always resolve to the local host), // and IP shouldn't even be used, but if it is for some reason, I think we can // at least be reasonably assured that 127.0.0.1 and ::1 route to the local // machine, meaning that a hypothetical browser origin would have to be on the // local machine as well. uniqueOrigins[""] = struct{}{} uniqueOrigins["127.0.0.1"] = struct{}{} uniqueOrigins["::1"] = struct{}{} } else { uniqueOrigins[net.JoinHostPort("localhost", addr.port())] = struct{}{} uniqueOrigins[net.JoinHostPort("::1", addr.port())] = struct{}{} uniqueOrigins[net.JoinHostPort("127.0.0.1", addr.port())] = struct{}{} } } if !addr.IsUnixNetwork() { uniqueOrigins[addr.JoinHostPort(0)] = struct{}{} } } allowed := make([]*url.URL, 0, len(uniqueOrigins)) for originStr := range uniqueOrigins { var origin *url.URL if strings.Contains(originStr, "://") { var err error origin, err = url.Parse(originStr) if err != nil { continue } origin.Path = "" origin.RawPath = "" origin.Fragment = "" origin.RawFragment = "" origin.RawQuery = "" } else { origin = &url.URL{Host: originStr} } allowed = append(allowed, origin) } return allowed } // replaceLocalAdminServer replaces the running local admin server // according to the relevant configuration in cfg. If no configuration // for the admin endpoint exists in cfg, a default one is used, so // that there is always an admin server (unless it is explicitly // configured to be disabled). func replaceLocalAdminServer(cfg *Config) error { // always* be sure to close down the old admin endpoint // as gracefully as possible, even if the new one is // disabled -- careful to use reference to the current // (old) admin endpoint since it will be different // when the function returns // (* except if the new one fails to start) oldAdminServer := localAdminServer var err error defer func() { // do the shutdown asynchronously so that any // current API request gets a response; this // goroutine may last a few seconds if oldAdminServer != nil && err == nil { go func(oldAdminServer *http.Server) { err := stopAdminServer(oldAdminServer) if err != nil { Log().Named("admin").Error("stopping current admin endpoint", zap.Error(err)) } }(oldAdminServer) } }() // set a default if admin wasn't otherwise configured if cfg.Admin == nil { cfg.Admin = &AdminConfig{ Listen: DefaultAdminListen, } } // if new admin endpoint is to be disabled, we're done if cfg.Admin.Disabled { Log().Named("admin").Warn("admin endpoint disabled") return nil } // extract a singular listener address addr, err := parseAdminListenAddr(cfg.Admin.Listen, DefaultAdminListen) if err != nil { return err } handler := cfg.Admin.newAdminHandler(addr, false) ln, err := addr.Listen(context.TODO(), 0, net.ListenConfig{}) if err != nil { return err } serverMu.Lock() localAdminServer = &http.Server{ Addr: addr.String(), // for logging purposes only Handler: handler, ReadTimeout: 10 * time.Second, ReadHeaderTimeout: 5 * time.Second, IdleTimeout: 60 * time.Second, MaxHeaderBytes: 1024 * 64, } serverMu.Unlock() adminLogger := Log().Named("admin") go func() { serverMu.Lock() server := localAdminServer serverMu.Unlock() if err := server.Serve(ln.(net.Listener)); !errors.Is(err, http.ErrServerClosed) { adminLogger.Error("admin server shutdown for unknown reason", zap.Error(err)) } }() adminLogger.Info("admin endpoint started", zap.String("address", addr.String()), zap.Bool("enforce_origin", cfg.Admin.EnforceOrigin), zap.Array("origins", loggableURLArray(handler.allowedOrigins))) if !handler.enforceHost { adminLogger.Warn("admin endpoint on open interface; host checking disabled", zap.String("address", addr.String())) } return nil } // manageIdentity sets up automated identity management for this server. func manageIdentity(ctx Context, cfg *Config) error { if cfg == nil || cfg.Admin == nil || cfg.Admin.Identity == nil { return nil } // set default issuers; this is pretty hacky because we can't // import the caddytls package -- but it works if cfg.Admin.Identity.IssuersRaw == nil { cfg.Admin.Identity.IssuersRaw = []json.RawMessage{ json.RawMessage(`{"module": "zerossl"}`), json.RawMessage(`{"module": "acme"}`), } } // load and provision issuer modules if cfg.Admin.Identity.IssuersRaw != nil { val, err := ctx.LoadModule(cfg.Admin.Identity, "IssuersRaw") if err != nil { return fmt.Errorf("loading identity issuer modules: %s", err) } for _, issVal := range val.([]any) { cfg.Admin.Identity.issuers = append(cfg.Admin.Identity.issuers, issVal.(certmagic.Issuer)) } } // we'll make a new cache when we make the CertMagic config, so stop any previous cache if identityCertCache != nil { identityCertCache.Stop() } logger := Log().Named("admin.identity") cmCfg := cfg.Admin.Identity.certmagicConfig(logger, true) // issuers have circular dependencies with the configs because, // as explained in the caddytls package, they need access to the // correct storage and cache to solve ACME challenges for _, issuer := range cfg.Admin.Identity.issuers { // avoid import cycle with caddytls package, so manually duplicate the interface here, yuck if annoying, ok := issuer.(interface{ SetConfig(cfg *certmagic.Config) }); ok { annoying.SetConfig(cmCfg) } } // obtain and renew server identity certificate(s) return cmCfg.ManageAsync(ctx, cfg.Admin.Identity.Identifiers) } // replaceRemoteAdminServer replaces the running remote admin server // according to the relevant configuration in cfg. It stops any previous // remote admin server and only starts a new one if configured. func replaceRemoteAdminServer(ctx Context, cfg *Config) error { if cfg == nil { return nil } remoteLogger := Log().Named("admin.remote") oldAdminServer := remoteAdminServer defer func() { if oldAdminServer != nil { go func(oldAdminServer *http.Server) { err := stopAdminServer(oldAdminServer) if err != nil { Log().Named("admin").Error("stopping current secure admin endpoint", zap.Error(err)) } }(oldAdminServer) } }() if cfg.Admin == nil || cfg.Admin.Remote == nil { return nil } addr, err := parseAdminListenAddr(cfg.Admin.Remote.Listen, DefaultRemoteAdminListen) if err != nil { return err } // make the HTTP handler but disable Host/Origin enforcement // because we are using TLS authentication instead handler := cfg.Admin.newAdminHandler(addr, true) // create client certificate pool for TLS mutual auth, and extract public keys // so that we can enforce access controls at the application layer clientCertPool := x509.NewCertPool() for i, accessControl := range cfg.Admin.Remote.AccessControl { for j, certBase64 := range accessControl.PublicKeys { cert, err := decodeBase64DERCert(certBase64) if err != nil { return fmt.Errorf("access control %d public key %d: parsing base64 certificate DER: %v", i, j, err) } accessControl.publicKeys = append(accessControl.publicKeys, cert.PublicKey) clientCertPool.AddCert(cert) } } // create TLS config that will enforce mutual authentication if identityCertCache == nil { return fmt.Errorf("cannot enable remote admin without a certificate cache; configure identity management to initialize a certificate cache") } cmCfg := cfg.Admin.Identity.certmagicConfig(remoteLogger, false) tlsConfig := cmCfg.TLSConfig() tlsConfig.NextProtos = nil // this server does not solve ACME challenges tlsConfig.ClientAuth = tls.RequireAndVerifyClientCert tlsConfig.ClientCAs = clientCertPool // convert logger to stdlib so it can be used by HTTP server serverLogger, err := zap.NewStdLogAt(remoteLogger, zap.DebugLevel) if err != nil { return err } serverMu.Lock() // create secure HTTP server remoteAdminServer = &http.Server{ Addr: addr.String(), // for logging purposes only Handler: handler, TLSConfig: tlsConfig, ReadTimeout: 10 * time.Second, ReadHeaderTimeout: 5 * time.Second, IdleTimeout: 60 * time.Second, MaxHeaderBytes: 1024 * 64, ErrorLog: serverLogger, } serverMu.Unlock() // start listener lnAny, err := addr.Listen(ctx, 0, net.ListenConfig{}) if err != nil { return err } ln := lnAny.(net.Listener) ln = tls.NewListener(ln, tlsConfig) go func() { serverMu.Lock() server := remoteAdminServer serverMu.Unlock() if err := server.Serve(ln); !errors.Is(err, http.ErrServerClosed) { remoteLogger.Error("admin remote server shutdown for unknown reason", zap.Error(err)) } }() remoteLogger.Info("secure admin remote control endpoint started", zap.String("address", addr.String())) return nil } func (ident *IdentityConfig) certmagicConfig(logger *zap.Logger, makeCache bool) *certmagic.Config { var cmCfg *certmagic.Config if ident == nil { // user might not have configured identity; that's OK, we can still make a // certmagic config, although it'll be mostly useless for remote management ident = new(IdentityConfig) } template := certmagic.Config{ Storage: DefaultStorage, // do not act as part of a cluster (this is for the server's local identity) Logger: logger, Issuers: ident.issuers, } if makeCache { identityCertCache = certmagic.NewCache(certmagic.CacheOptions{ GetConfigForCert: func(certmagic.Certificate) (*certmagic.Config, error) { return cmCfg, nil }, Logger: logger.Named("cache"), }) } cmCfg = certmagic.New(identityCertCache, template) return cmCfg } // IdentityCredentials returns this instance's configured, managed identity credentials // that can be used in TLS client authentication. func (ctx Context) IdentityCredentials(logger *zap.Logger) ([]tls.Certificate, error) { if ctx.cfg == nil || ctx.cfg.Admin == nil || ctx.cfg.Admin.Identity == nil { return nil, fmt.Errorf("no server identity configured") } ident := ctx.cfg.Admin.Identity if len(ident.Identifiers) == 0 { return nil, fmt.Errorf("no identifiers configured") } if logger == nil { logger = Log() } magic := ident.certmagicConfig(logger, false) return magic.ClientCredentials(ctx, ident.Identifiers) } // enforceAccessControls enforces application-layer access controls for r based on remote. // It expects that the TLS server has already established at least one verified chain of // trust, and then looks for a matching, authorized public key that is allowed to access // the defined path(s) using the defined method(s). func (remote RemoteAdmin) enforceAccessControls(r *http.Request) error { for _, chain := range r.TLS.VerifiedChains { for _, peerCert := range chain { for _, adminAccess := range remote.AccessControl { for _, allowedKey := range adminAccess.publicKeys { // see if we found a matching public key; the TLS server already verified the chain // so we know the client possesses the associated private key; this handy interface // doesn't appear to be defined anywhere in the std lib, but was implemented here: // https://github.com/golang/go/commit/b5f2c0f50297fa5cd14af668ddd7fd923626cf8c comparer, ok := peerCert.PublicKey.(interface{ Equal(crypto.PublicKey) bool }) if !ok || !comparer.Equal(allowedKey) { continue } // key recognized; make sure its HTTP request is permitted for _, accessPerm := range adminAccess.Permissions { // verify method methodFound := accessPerm.Methods == nil for _, method := range accessPerm.Methods { if method == r.Method { methodFound = true break } } if !methodFound { return APIError{ HTTPStatus: http.StatusForbidden, Message: "not authorized to use this method", } } // verify path pathFound := accessPerm.Paths == nil for _, allowedPath := range accessPerm.Paths { if strings.HasPrefix(r.URL.Path, allowedPath) { pathFound = true break } } if !pathFound { return APIError{ HTTPStatus: http.StatusForbidden, Message: "not authorized to access this path", } } } // public key authorized, method and path allowed return nil } } } } // in theory, this should never happen; with an unverified chain, the TLS server // should not accept the connection in the first place, and the acceptable cert // pool is configured using the same list of public keys we verify against return APIError{ HTTPStatus: http.StatusUnauthorized, Message: "client identity not authorized", } } func stopAdminServer(srv *http.Server) error { if srv == nil { return fmt.Errorf("no admin server") } ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) defer cancel() err := srv.Shutdown(ctx) if err != nil { return fmt.Errorf("shutting down admin server: %v", err) } Log().Named("admin").Info("stopped previous server", zap.String("address", srv.Addr)) return nil } // AdminRouter is a type which can return routes for the admin API. type AdminRouter interface { Routes() []AdminRoute } // AdminRoute represents a route for the admin endpoint. type AdminRoute struct { Pattern string Handler AdminHandler } type adminHandler struct { mux *http.ServeMux // security for local/plaintext endpoint enforceOrigin bool enforceHost bool allowedOrigins []*url.URL // security for remote/encrypted endpoint remoteControl *RemoteAdmin } // ServeHTTP is the external entry point for API requests. // It will only be called once per request. func (h adminHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { ip, port, err := net.SplitHostPort(r.RemoteAddr) if err != nil { ip = r.RemoteAddr port = "" } log := Log().Named("admin.api").With( zap.String("method", r.Method), zap.String("host", r.Host), zap.String("uri", r.RequestURI), zap.String("remote_ip", ip), zap.String("remote_port", port), zap.Reflect("headers", r.Header), ) if r.TLS != nil { log = log.With( zap.Bool("secure", true), zap.Int("verified_chains", len(r.TLS.VerifiedChains)), ) } if r.RequestURI == "/metrics" { log.Debug("received request") } else { log.Info("received request") } h.serveHTTP(w, r) } // serveHTTP is the internal entry point for API requests. It may // be called more than once per request, for example if a request // is rewritten (i.e. internal redirect). func (h adminHandler) serveHTTP(w http.ResponseWriter, r *http.Request) { if h.remoteControl != nil { // enforce access controls on secure endpoint if err := h.remoteControl.enforceAccessControls(r); err != nil { h.handleError(w, r, err) return } } if strings.Contains(r.Header.Get("Upgrade"), "websocket") { // I've never been able demonstrate a vulnerability myself, but apparently // WebSocket connections originating from browsers aren't subject to CORS // restrictions, so we'll just be on the safe side h.handleError(w, r, fmt.Errorf("websocket connections aren't allowed")) return } if h.enforceHost { // DNS rebinding mitigation err := h.checkHost(r) if err != nil { h.handleError(w, r, err) return } } if h.enforceOrigin { // cross-site mitigation origin, err := h.checkOrigin(r) if err != nil { h.handleError(w, r, err) return } if r.Method == http.MethodOptions { w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, GET, POST, PUT, PATCH, DELETE") w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Content-Length, Cache-Control") w.Header().Set("Access-Control-Allow-Credentials", "true") } w.Header().Set("Access-Control-Allow-Origin", origin) } h.mux.ServeHTTP(w, r) } func (h adminHandler) handleError(w http.ResponseWriter, r *http.Request, err error) { if err == nil { return } if err == errInternalRedir { h.serveHTTP(w, r) return } apiErr, ok := err.(APIError) if !ok { apiErr = APIError{ HTTPStatus: http.StatusInternalServerError, Err: err, } } if apiErr.HTTPStatus == 0 { apiErr.HTTPStatus = http.StatusInternalServerError } if apiErr.Message == "" && apiErr.Err != nil { apiErr.Message = apiErr.Err.Error() } Log().Named("admin.api").Error("request error", zap.Error(err), zap.Int("status_code", apiErr.HTTPStatus), ) w.Header().Set("Content-Type", "application/json") w.WriteHeader(apiErr.HTTPStatus) encErr := json.NewEncoder(w).Encode(apiErr) if encErr != nil { Log().Named("admin.api").Error("failed to encode error response", zap.Error(encErr)) } } // checkHost returns a handler that wraps next such that // it will only be called if the request's Host header matches // a trustworthy/expected value. This helps to mitigate DNS // rebinding attacks. func (h adminHandler) checkHost(r *http.Request) error { var allowed bool for _, allowedOrigin := range h.allowedOrigins { if r.Host == allowedOrigin.Host { allowed = true break } } if !allowed { return APIError{ HTTPStatus: http.StatusForbidden, Err: fmt.Errorf("host not allowed: %s", r.Host), } } return nil } // checkOrigin ensures that the Origin header, if // set, matches the intended target; prevents arbitrary // sites from issuing requests to our listener. It // returns the origin that was obtained from r. func (h adminHandler) checkOrigin(r *http.Request) (string, error) { originStr, origin := h.getOrigin(r) if origin == nil { return "", APIError{ HTTPStatus: http.StatusForbidden, Err: fmt.Errorf("required Origin header is missing or invalid"), } } if !h.originAllowed(origin) { return "", APIError{ HTTPStatus: http.StatusForbidden, Err: fmt.Errorf("client is not allowed to access from origin '%s'", originStr), } } return origin.String(), nil } func (h adminHandler) getOrigin(r *http.Request) (string, *url.URL) { origin := r.Header.Get("Origin") if origin == "" { origin = r.Header.Get("Referer") } originURL, err := url.Parse(origin) if err != nil { return origin, nil } originURL.Path = "" originURL.RawPath = "" originURL.Fragment = "" originURL.RawFragment = "" originURL.RawQuery = "" return origin, originURL } func (h adminHandler) originAllowed(origin *url.URL) bool { for _, allowedOrigin := range h.allowedOrigins { if allowedOrigin.Scheme != "" && origin.Scheme != allowedOrigin.Scheme { continue } if origin.Host == allowedOrigin.Host { return true } } return false } // etagHasher returns a the hasher we used on the config to both // produce and verify ETags. func etagHasher() hash.Hash32 { return fnv.New32a() } // makeEtag returns an Etag header value (including quotes) for // the given config path and hash of contents at that path. func makeEtag(path string, hash hash.Hash) string { return fmt.Sprintf(`"%s %x"`, path, hash.Sum(nil)) } func handleConfig(w http.ResponseWriter, r *http.Request) error { switch r.Method { case http.MethodGet: w.Header().Set("Content-Type", "application/json") // Set the ETag as a trailer header. // The alternative is to write the config to a buffer, and // then hash that. w.Header().Set("Trailer", "ETag") hash := etagHasher() configWriter := io.MultiWriter(w, hash) err := readConfig(r.URL.Path, configWriter) if err != nil { return APIError{HTTPStatus: http.StatusBadRequest, Err: err} } // we could consider setting up a sync.Pool for the summed // hashes to reduce GC pressure. w.Header().Set("Etag", makeEtag(r.URL.Path, hash)) return nil case http.MethodPost, http.MethodPut, http.MethodPatch, http.MethodDelete: // DELETE does not use a body, but the others do var body []byte if r.Method != http.MethodDelete { if ct := r.Header.Get("Content-Type"); !strings.Contains(ct, "/json") { return APIError{ HTTPStatus: http.StatusBadRequest, Err: fmt.Errorf("unacceptable content-type: %v; 'application/json' required", ct), } } buf := bufPool.Get().(*bytes.Buffer) buf.Reset() defer bufPool.Put(buf) _, err := io.Copy(buf, r.Body) if err != nil { return APIError{ HTTPStatus: http.StatusBadRequest, Err: fmt.Errorf("reading request body: %v", err), } } body = buf.Bytes() } forceReload := r.Header.Get("Cache-Control") == "must-revalidate" err := changeConfig(r.Method, r.URL.Path, body, r.Header.Get("If-Match"), forceReload) if err != nil && !errors.Is(err, errSameConfig) { return err } default: return APIError{ HTTPStatus: http.StatusMethodNotAllowed, Err: fmt.Errorf("method %s not allowed", r.Method), } } return nil } func handleConfigID(w http.ResponseWriter, r *http.Request) error { idPath := r.URL.Path parts := strings.Split(idPath, "/") if len(parts) < 3 || parts[2] == "" { return APIError{ HTTPStatus: http.StatusBadRequest, Err: fmt.Errorf("request path is missing object ID"), } } if parts[0] != "" || parts[1] != "id" { return APIError{ HTTPStatus: http.StatusBadRequest, Err: fmt.Errorf("malformed object path"), } } id := parts[2] // map the ID to the expanded path rawCfgMu.RLock() expanded, ok := rawCfgIndex[id] rawCfgMu.RUnlock() if !ok { return APIError{ HTTPStatus: http.StatusNotFound, Err: fmt.Errorf("unknown object ID '%s'", id), } } // piece the full URL path back together parts = append([]string{expanded}, parts[3:]...) r.URL.Path = path.Join(parts...) return errInternalRedir } func handleStop(w http.ResponseWriter, r *http.Request) error { if r.Method != http.MethodPost { return APIError{ HTTPStatus: http.StatusMethodNotAllowed, Err: fmt.Errorf("method not allowed"), } } exitProcess(context.Background(), Log().Named("admin.api")) return nil } // unsyncedConfigAccess traverses into the current config and performs // the operation at path according to method, using body and out as // needed. This is a low-level, unsynchronized function; most callers // will want to use changeConfig or readConfig instead. This requires a // read or write lock on currentCtxMu, depending on method (GET needs // only a read lock; all others need a write lock). func unsyncedConfigAccess(method, path string, body []byte, out io.Writer) error { var err error var val any // if there is a request body, decode it into the // variable that will be set in the config according // to method and path if len(body) > 0 { err = json.Unmarshal(body, &val) if err != nil { return fmt.Errorf("decoding request body: %v", err) } } enc := json.NewEncoder(out) cleanPath := strings.Trim(path, "/") if cleanPath == "" { return fmt.Errorf("no traversable path") } parts := strings.Split(cleanPath, "/") if len(parts) == 0 { return fmt.Errorf("path missing") } // A path that ends with "..." implies: // 1) the part before it is an array // 2) the payload is an array // and means that the user wants to expand the elements // in the payload array and append each one into the // destination array, like so: // array = append(array, elems...) // This special case is handled below. ellipses := parts[len(parts)-1] == "..." if ellipses { parts = parts[:len(parts)-1] } var ptr any = rawCfg traverseLoop: for i, part := range parts { switch v := ptr.(type) { case map[string]any: // if the next part enters a slice, and the slice is our destination, // handle it specially (because appending to the slice copies the slice // header, which does not replace the original one like we want) if arr, ok := v[part].([]any); ok && i == len(parts)-2 { var idx int if method != http.MethodPost { idxStr := parts[len(parts)-1] idx, err = strconv.Atoi(idxStr) if err != nil { return fmt.Errorf("[%s] invalid array index '%s': %v", path, idxStr, err) } if idx < 0 || idx >= len(arr) { return fmt.Errorf("[%s] array index out of bounds: %s", path, idxStr) } } switch method { case http.MethodGet: err = enc.Encode(arr[idx]) if err != nil { return fmt.Errorf("encoding config: %v", err) } case http.MethodPost: if ellipses { valArray, ok := val.([]any) if !ok { return fmt.Errorf("final element is not an array") } v[part] = append(arr, valArray...) } else { v[part] = append(arr, val) } case http.MethodPut: // avoid creation of new slice and a second copy (see // https://github.com/golang/go/wiki/SliceTricks#insert) arr = append(arr, nil) copy(arr[idx+1:], arr[idx:]) arr[idx] = val v[part] = arr case http.MethodPatch: arr[idx] = val case http.MethodDelete: v[part] = append(arr[:idx], arr[idx+1:]...) default: return fmt.Errorf("unrecognized method %s", method) } break traverseLoop } if i == len(parts)-1 { switch method { case http.MethodGet: err = enc.Encode(v[part]) if err != nil { return fmt.Errorf("encoding config: %v", err) } case http.MethodPost: // if the part is an existing list, POST appends to // it, otherwise it just sets or creates the value if arr, ok := v[part].([]any); ok { if ellipses { valArray, ok := val.([]any) if !ok { return fmt.Errorf("final element is not an array") } v[part] = append(arr, valArray...) } else { v[part] = append(arr, val) } } else { v[part] = val } case http.MethodPut: if _, ok := v[part]; ok { return fmt.Errorf("[%s] key already exists: %s", path, part) } v[part] = val case http.MethodPatch: if _, ok := v[part]; !ok { return fmt.Errorf("[%s] key does not exist: %s", path, part) } v[part] = val case http.MethodDelete: delete(v, part) default: return fmt.Errorf("unrecognized method %s", method) } } else { // if we are "PUTting" a new resource, the key(s) in its path // might not exist yet; that's OK but we need to make them as // we go, while we still have a pointer from the level above if v[part] == nil && method == http.MethodPut { v[part] = make(map[string]any) } ptr = v[part] } case []any: partInt, err := strconv.Atoi(part) if err != nil { return fmt.Errorf("[/%s] invalid array index '%s': %v", strings.Join(parts[:i+1], "/"), part, err) } if partInt < 0 || partInt >= len(v) { return fmt.Errorf("[/%s] array index out of bounds: %s", strings.Join(parts[:i+1], "/"), part) } ptr = v[partInt] default: return fmt.Errorf("invalid traversal path at: %s", strings.Join(parts[:i+1], "/")) } } return nil } // RemoveMetaFields removes meta fields like "@id" from a JSON message // by using a simple regular expression. (An alternate way to do this // would be to delete them from the raw, map[string]any // representation as they are indexed, then iterate the index we made // and add them back after encoding as JSON, but this is simpler.) func RemoveMetaFields(rawJSON []byte) []byte { return idRegexp.ReplaceAllFunc(rawJSON, func(in []byte) []byte { // matches with a comma on both sides (when "@id" property is // not the first or last in the object) need to keep exactly // one comma for correct JSON syntax comma := []byte{','} if bytes.HasPrefix(in, comma) && bytes.HasSuffix(in, comma) { return comma } return []byte{} }) } // AdminHandler is like http.Handler except ServeHTTP may return an error. // // If any handler encounters an error, it should be returned for proper // handling. type AdminHandler interface { ServeHTTP(http.ResponseWriter, *http.Request) error } // AdminHandlerFunc is a convenience type like http.HandlerFunc. type AdminHandlerFunc func(http.ResponseWriter, *http.Request) error // ServeHTTP implements the Handler interface. func (f AdminHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request) error { return f(w, r) } // APIError is a structured error that every API // handler should return for consistency in logging // and client responses. If Message is unset, then // Err.Error() will be serialized in its place. type APIError struct { HTTPStatus int `json:"-"` Err error `json:"-"` Message string `json:"error"` } func (e APIError) Error() string { if e.Err != nil { return e.Err.Error() } return e.Message } // parseAdminListenAddr extracts a singular listen address from either addr // or defaultAddr, returning the network and the address of the listener. func parseAdminListenAddr(addr string, defaultAddr string) (NetworkAddress, error) { input, err := NewReplacer().ReplaceOrErr(addr, true, true) if err != nil { return NetworkAddress{}, fmt.Errorf("replacing listen address: %v", err) } if input == "" { input = defaultAddr } listenAddr, err := ParseNetworkAddress(input) if err != nil { return NetworkAddress{}, fmt.Errorf("parsing listener address: %v", err) } if listenAddr.PortRangeSize() != 1 { return NetworkAddress{}, fmt.Errorf("must be exactly one listener address; cannot listen on: %s", listenAddr) } return listenAddr, nil } // decodeBase64DERCert base64-decodes, then DER-decodes, certStr. func decodeBase64DERCert(certStr string) (*x509.Certificate, error) { derBytes, err := base64.StdEncoding.DecodeString(certStr) if err != nil { return nil, err } return x509.ParseCertificate(derBytes) } type loggableURLArray []*url.URL func (ua loggableURLArray) MarshalLogArray(enc zapcore.ArrayEncoder) error { if ua == nil { return nil } for _, u := range ua { enc.AppendString(u.String()) } return nil } var ( // DefaultAdminListen is the address for the local admin // listener, if none is specified at startup. DefaultAdminListen = "localhost:2019" // DefaultRemoteAdminListen is the address for the remote // (TLS-authenticated) admin listener, if enabled and not // specified otherwise. DefaultRemoteAdminListen = ":2021" ) // PIDFile writes a pidfile to the file at filename. It // will get deleted before the process gracefully exits. func PIDFile(filename string) error { pid := []byte(strconv.Itoa(os.Getpid()) + "\n") err := os.WriteFile(filename, pid, 0o600) if err != nil { return err } pidfile = filename return nil } // idRegexp is used to match ID fields and their associated values // in the config. It also matches adjacent commas so that syntax // can be preserved no matter where in the object the field appears. // It supports string and most numeric values. var idRegexp = regexp.MustCompile(`(?m),?\s*"` + idKey + `"\s*:\s*(-?[0-9]+(\.[0-9]+)?|(?U)".*")\s*,?`) // pidfile is the name of the pidfile, if any. var pidfile string // errInternalRedir indicates an internal redirect // and is useful when admin API handlers rewrite // the request; in that case, authentication and // authorization needs to happen again for the // rewritten request. var errInternalRedir = fmt.Errorf("internal redirect; re-authorization required") const ( rawConfigKey = "config" idKey = "@id" ) var bufPool = sync.Pool{ New: func() any { return new(bytes.Buffer) }, } // keep a reference to admin endpoint singletons while they're active var ( serverMu sync.Mutex localAdminServer, remoteAdminServer *http.Server identityCertCache *certmagic.Cache )