tsweb

Documentation

Overview

Package tsweb contains code used in various Tailscale webservers.

Index

• Constants
• Variables
• func AcceptsEncoding(r *http.Request, enc string) bool
• func AddBrowserHeaders(w http.ResponseWriter)
• func AllowDebugAccess(r *http.Request) bool
• func BrowserHeaderHandler(h http.Handler) http.Handler
• func BrowserHeaderHandlerFunc(h http.HandlerFunc) http.HandlerFunc
• func DefaultCertDir(leafDir string) string
• func IsProd443(addr string) bool
• func Protected(h http.Handler) http.Handler
• func SetRequestID(h http.Handler) http.Handler
• func StdHandler(h ReturnHandler, opts HandlerOptions) http.Handler
• func VarzHandler(w http.ResponseWriter, r *http.Request)
• type AccessLogRecord
  • func (m AccessLogRecord) String() string
• type DebugHandler
  • func Debugger(mux *http.ServeMux) *DebugHandler
  • func (d *DebugHandler) Handle(slug, desc string, handler http.Handler)
  • func (d *DebugHandler) HandleSilent(slug string, handler http.Handler)
  • func (d *DebugHandler) KV(k string, v any)
  • func (d *DebugHandler) KVFunc(k string, v func() any)
  • func (d *DebugHandler) Section(f func(w io.Writer, r *http.Request))
  • func (d *DebugHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)
  • func (d *DebugHandler) URL(url, desc string)
• type ErrorHandlerFunc
• type HTTPError
  • func Error(code int, msg string, err error) HTTPError
  • func (e HTTPError) Error() string
  • func (e HTTPError) Unwrap() error
• type HandlerOptions
• type Middleware
• type Port80Handler
  • func (h Port80Handler) ServeHTTP(w http.ResponseWriter, r *http.Request)
• type RequestID
  • func RequestIDFromContext(ctx context.Context) RequestID
• type ReturnHandler
• type ReturnHandlerFunc
  • func (f ReturnHandlerFunc) ServeHTTPReturn(w http.ResponseWriter, r *http.Request) error

Examples

• DebugHandler.Handle
• DebugHandler.KV
• DebugHandler.KVFunc
• DebugHandler.Section
• DebugHandler.URL

Constants

const RequestIDHeader = "X-Tailscale-Request-Id"

RequestIDHeader is a custom HTTP header that the WithRequestID middleware uses to determine whether to re-use a given request ID from the client or generate a new one.

Variables

var DevMode bool

DevMode controls whether extra output in shown, for when the binary is being run in dev mode.

var RequestIDKey ctxkey.Key[RequestID]

RequestIDKey stores and loads RequestID values within a context.Context.

Functions

func AcceptsEncoding

func AcceptsEncoding(r *http.Request, enc string) bool

AcceptsEncoding reports whether r accepts the named encoding ("gzip", "br", etc).

func AddBrowserHeaders

func AddBrowserHeaders(w http.ResponseWriter)

AddBrowserHeaders sets various HTTP security headers for browser-facing endpoints.

The specific headers:

• require HTTPS access (HSTS)
• disallow iframe embedding
• mitigate MIME confusion attacks

These headers are based on https://infosec.mozilla.org/guidelines/web_security

func AllowDebugAccess

func AllowDebugAccess(r *http.Request) bool

AllowDebugAccess reports whether r should be permitted to access various debug endpoints.

func BrowserHeaderHandler

func BrowserHeaderHandler(h http.Handler) http.Handler

BrowserHeaderHandler wraps the provided http.Handler with a call to AddBrowserHeaders.

func BrowserHeaderHandlerFunc

func BrowserHeaderHandlerFunc(h http.HandlerFunc) http.HandlerFunc

BrowserHeaderHandlerFunc wraps the provided http.HandlerFunc with a call to AddBrowserHeaders.

func DefaultCertDir

func DefaultCertDir(leafDir string) string

func IsProd443

func IsProd443(addr string) bool

IsProd443 reports whether addr is a Go listen address for port 443.

func Protected

func Protected(h http.Handler) http.Handler

Protected wraps a provided debug handler, h, returning a Handler that enforces AllowDebugAccess and returns forbidden replies for unauthorized requests.

func SetRequestID

func SetRequestID(h http.Handler) http.Handler

SetRequestID is an HTTP middleware that injects a RequestID in the *http.Request Context. The value of that request id is either retrieved from the RequestIDHeader or a randomly generated one if not exists. Inner handlers can retrieve this ID from the RequestIDFromContext function.

func StdHandler

func StdHandler(h ReturnHandler, opts HandlerOptions) http.Handler

StdHandler converts a ReturnHandler into a standard http.Handler. Handled requests are logged using opts.Logf, as are any errors. Errors are handled as specified by the Handler interface.

func VarzHandler

func VarzHandler(w http.ResponseWriter, r *http.Request)

VarzHandler writes expvar values as Prometheus metrics. TODO: migrate all users to varz.Handler or promvarz.Handler and remove this.

Types

type AccessLogRecord

type AccessLogRecord struct {
	// Timestamp at which request processing started.
	When time.Time `json:"when"`
	// Time it took to finish processing the request. It does not
	// include the entire lifetime of the underlying connection in
	// cases like connection hijacking, only the lifetime of the HTTP
	// request handler.
	Seconds float64 `json:"duration,omitempty"`

	// The client's ip:port.
	RemoteAddr string `json:"remote_addr,omitempty"`
	// The HTTP protocol version, usually "HTTP/1.1 or HTTP/2".
	Proto string `json:"proto,omitempty"`
	// Whether the request was received over TLS.
	TLS bool `json:"tls,omitempty"`
	// The target hostname in the request.
	Host string `json:"host,omitempty"`
	// The HTTP method invoked.
	Method string `json:"method,omitempty"`
	// The unescaped request URI, including query parameters.
	RequestURI string `json:"request_uri,omitempty"`

	// The client's user-agent
	UserAgent string `json:"user_agent,omitempty"`
	// Where the client was before making this request.
	Referer string `json:"referer,omitempty"`

	// The HTTP response code sent to the client.
	Code int `json:"code,omitempty"`
	// Number of bytes sent in response body to client. If the request
	// was hijacked, only includes bytes sent up to the point of
	// hijacking.
	Bytes int `json:"bytes,omitempty"`
	// Error encountered during request processing.
	Err string `json:"err,omitempty"`
	// RequestID is a unique ID for this request. If the *http.Request context
	// carries this value via SetRequestID, then it will be displayed to the
	// client immediately after the error text, as well as logged here. This
	// makes it easier to correlate support requests with server logs. If a
	// RequestID generator is not configured, RequestID will be empty.
	RequestID RequestID `json:"request_id,omitempty"`
}

AccessLogRecord is a record of one HTTP request served.

func (AccessLogRecord) String

func (m AccessLogRecord) String() string

String returns m as a JSON string.

type DebugHandler

type DebugHandler struct {
	// contains filtered or unexported fields
}

DebugHandler is an http.Handler that serves a debugging "homepage", and provides helpers to register more debug endpoints and reports.

The rendered page consists of three sections: informational key/value pairs, links to other pages, and additional program-specific HTML. Callers can add to these sections using the KV, URL and Section helpers respectively.

Additionally, the Handle method offers a shorthand for correctly registering debug handlers and cross-linking them from /debug/.

func Debugger

func Debugger(mux *http.ServeMux) *DebugHandler

Debugger returns the DebugHandler registered on mux at /debug/, creating it if necessary.

func (*DebugHandler) Handle

func (d *DebugHandler) Handle(slug, desc string, handler http.Handler)

Handle registers handler at /debug/<slug> and creates a descriptive entry in /debug/ for it.

Example

mux := http.NewServeMux()
dbg := Debugger(mux)
// Registers /debug/flushcache with the given handler, and adds a
// link to /debug/ with the description "Flush caches".
dbg.Handle("flushcache", "Flush caches", http.HandlerFunc(http.NotFound))

func (*DebugHandler) HandleSilent

func (d *DebugHandler) HandleSilent(slug string, handler http.Handler)

HandleSilent registers handler at /debug/<slug>. It does not create a descriptive entry in /debug/ for it. This should be used sparingly, for things that need to be registered but would pollute the list of debug links.

func (*DebugHandler) KV

func (d *DebugHandler) KV(k string, v any)

KV adds a key/value list item to /debug/.

Example

mux := http.NewServeMux()
dbg := Debugger(mux)
// Adds two list items to /debug/, showing that the condition is
// red and there are 42 donuts.
dbg.KV("Condition", "red")
dbg.KV("Donuts", 42)

func (*DebugHandler) KVFunc

func (d *DebugHandler) KVFunc(k string, v func() any)

KVFunc adds a key/value list item to /debug/. v is called on every render of /debug/.

Example

mux := http.NewServeMux()
dbg := Debugger(mux)
// Adds an count of page renders to /debug/. Note this example
// isn't concurrency-safe.
views := 0
dbg.KVFunc("Debug pageviews", func() any {
	views = views + 1
	return views
})
dbg.KV("Donuts", 42)

func (*DebugHandler) Section

func (d *DebugHandler) Section(f func(w io.Writer, r *http.Request))

Section invokes f on every render of /debug/ to add supplemental HTML to the page body.

Example

mux := http.NewServeMux()
dbg := Debugger(mux)
// Adds a section to /debug/ that dumps the HTTP request of the
// visitor.
dbg.Section(func(w io.Writer, r *http.Request) {
	io.WriteString(w, "<h3>Dump of your HTTP request</h3>")
	fmt.Fprintf(w, "<code>%#v</code>", r)
})

func (*DebugHandler) ServeHTTP

func (d *DebugHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)

ServeHTTP implements http.Handler.

func (*DebugHandler) URL

func (d *DebugHandler) URL(url, desc string)

URL adds a URL and description list item to /debug/.

Example

mux := http.NewServeMux()
dbg := Debugger(mux)
// Links to the Tailscale website from /debug/.
dbg.URL("https://www.tailscale.com", "Homepage")

type ErrorHandlerFunc

type ErrorHandlerFunc func(http.ResponseWriter, *http.Request, HTTPError)

ErrorHandlerFunc is called to present a error response.

type HTTPError

type HTTPError struct {
	Code   int         // HTTP response code to send to client; 0 means 500
	Msg    string      // Response body to send to client
	Err    error       // Detailed error to log on the server
	Header http.Header // Optional set of HTTP headers to set in the response
}

HTTPError is an error with embedded HTTP response information.

It is the error type to be (optionally) used by Handler.ServeHTTPReturn.

func Error

func Error(code int, msg string, err error) HTTPError

Error returns an HTTPError containing the given information.

func (HTTPError) Error

func (e HTTPError) Error() string

Error implements the error interface.

func (HTTPError) Unwrap

func (e HTTPError) Unwrap() error

type HandlerOptions

type HandlerOptions struct {
	QuietLoggingIfSuccessful bool // if set, do not log successfully handled HTTP requests (200 and 304 status codes)
	Logf                     logger.Logf
	Now                      func() time.Time // if nil, defaults to time.Now

	// If non-nil, StatusCodeCounters maintains counters
	// of status codes for handled responses.
	// The keys are "1xx", "2xx", "3xx", "4xx", and "5xx".
	StatusCodeCounters *expvar.Map
	// If non-nil, StatusCodeCountersFull maintains counters of status
	// codes for handled responses.
	// The keys are HTTP numeric response codes e.g. 200, 404, ...
	StatusCodeCountersFull *expvar.Map

	// OnError is called if the handler returned a HTTPError. This
	// is intended to be used to present pretty error pages if
	// the user agent is determined to be a browser.
	OnError ErrorHandlerFunc
}

type Middleware

type Middleware func(h http.Handler) http.Handler

A Middleware is a function that wraps an http.Handler to extend or modify its behaviour.

The implementation of the wrapper is responsible for delegating its input request to the underlying handler, if appropriate.

type Port80Handler

type Port80Handler struct {
	Main http.Handler
	// FQDN is used to redirect incoming requests to https://<FQDN>.
	// If it is not set, the hostname is calculated from the incoming
	// request.
	FQDN string
}

Port80Handler is the handler to be given to autocert.Manager.HTTPHandler. The inner handler is the mux returned by NewMux containing registered /debug handlers.

func (Port80Handler) ServeHTTP

func (h Port80Handler) ServeHTTP(w http.ResponseWriter, r *http.Request)

type RequestID

type RequestID string

RequestID is an opaque identifier for a HTTP request, used to correlate user-visible errors with backend server logs. The RequestID is typically threaded through an HTTP Middleware (WithRequestID) and then can be extracted by HTTP Handlers to include in their logs.

RequestID is an opaque identifier for a HTTP request, used to correlate user-visible errors with backend server logs. If present in the context, the RequestID will be printed alongside the message text and logged in the AccessLogRecord.

A RequestID has the format "REQ-1{ID}", and the ID should be treated as an opaque string. The current implementation uses a UUID.

func RequestIDFromContext

func RequestIDFromContext(ctx context.Context) RequestID

RequestIDFromContext retrieves the RequestID from context that can be set by the SetRequestID function.

Deprecated: Use [RequestIDKey.Value] instead.

type ReturnHandler

type ReturnHandler interface {
	// ServeHTTPReturn is like http.Handler.ServeHTTP, except that
	// it can choose to return an error instead of writing to its
	// http.ResponseWriter.
	//
	// If ServeHTTPReturn returns an error, it caller should handle
	// an error by serving an HTTP 500 response to the user. The
	// error details should not be sent to the client, as they may
	// contain sensitive information. If the error is an
	// HTTPError, though, callers should use the HTTP response
	// code and message as the response to the client.
	ServeHTTPReturn(http.ResponseWriter, *http.Request) error
}

ReturnHandler is like net/http.Handler, but the handler can return an error instead of writing to its ResponseWriter.

type ReturnHandlerFunc

type ReturnHandlerFunc func(http.ResponseWriter, *http.Request) error

ReturnHandlerFunc is an adapter to allow the use of ordinary functions as ReturnHandlers. If f is a function with the appropriate signature, ReturnHandlerFunc(f) is a ReturnHandler that calls f.

func (ReturnHandlerFunc) ServeHTTPReturn

func (f ReturnHandlerFunc) ServeHTTPReturn(w http.ResponseWriter, r *http.Request) error

ServeHTTPReturn calls f(w, r).