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30c9189ed3
* tsweb: update ServeMux matching to 1.22.0 syntax Updates #cleanup Go 1.22.0 introduced the ability to use more expressive routing patterns that include HTTP method when constructing ServeMux entries. Applications that attempted to use these patterns in combination with the old `tsweb.Debugger` would experience a panic as Go would not permit the use of matching rules with mixed level of specificity. We now specify the method for each `/debug` handler to prevent incompatibilities. Signed-off-by: Patrick O'Doherty <patrick@tailscale.com>
174 lines
5.9 KiB
Go
174 lines
5.9 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package tsweb
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import (
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"expvar"
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"fmt"
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"html"
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"io"
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"net/http"
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"net/http/pprof"
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"net/url"
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"os"
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"runtime"
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"tailscale.com/tsweb/promvarz"
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"tailscale.com/tsweb/varz"
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"tailscale.com/version"
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)
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// DebugHandler is an http.Handler that serves a debugging "homepage",
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// and provides helpers to register more debug endpoints and reports.
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//
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// The rendered page consists of three sections: informational
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// key/value pairs, links to other pages, and additional
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// program-specific HTML. Callers can add to these sections using the
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// KV, URL and Section helpers respectively.
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//
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// Additionally, the Handle method offers a shorthand for correctly
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// registering debug handlers and cross-linking them from /debug/.
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type DebugHandler struct {
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mux *http.ServeMux // where this handler is registered
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kvs []func(io.Writer) // output one <li>...</li> each, see KV()
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urls []string // one <li>...</li> block with link each
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sections []func(io.Writer, *http.Request) // invoked in registration order prior to outputting </body>
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}
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// Debugger returns the DebugHandler registered on mux at /debug/,
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// creating it if necessary.
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func Debugger(mux *http.ServeMux) *DebugHandler {
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h, pattern := mux.Handler(&http.Request{Method: "GET", URL: &url.URL{Path: "/debug/"}})
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if d, ok := h.(*DebugHandler); ok && pattern == "GET /debug/" {
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return d
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}
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ret := &DebugHandler{
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mux: mux,
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}
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mux.Handle("GET /debug/", ret)
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ret.KVFunc("Uptime", func() any { return varz.Uptime() })
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ret.KV("Version", version.Long())
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ret.Handle("GET vars", "Metrics (Go)", expvar.Handler())
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ret.Handle("GET varz", "Metrics (Prometheus)", http.HandlerFunc(promvarz.Handler))
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ret.Handle("GET pprof/", "pprof (index)", http.HandlerFunc(pprof.Index))
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// the CPU profile handler is special because it responds
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// streamily, unlike every other pprof handler. This means it's
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// not made available through pprof.Index the way all the other
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// pprof types are, you have to register the CPU profile handler
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// separately. Use HandleSilent for that to not pollute the human
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// debug list with a link that produces streaming line noise if
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// you click it.
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ret.HandleSilent("pprof/profile", http.HandlerFunc(pprof.Profile))
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ret.URL("/debug/pprof/goroutine?debug=1", "Goroutines (collapsed)")
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ret.URL("/debug/pprof/goroutine?debug=2", "Goroutines (full)")
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ret.Handle("GET gc", "force GC", http.HandlerFunc(gcHandler))
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hostname, err := os.Hostname()
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if err == nil {
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ret.KV("Machine", hostname)
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}
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return ret
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}
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// ServeHTTP implements http.Handler.
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func (d *DebugHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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if !AllowDebugAccess(r) {
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http.Error(w, "debug access denied", http.StatusForbidden)
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return
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}
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if r.URL.Path != "/debug/" {
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// Sub-handlers are handled by the parent mux directly.
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http.NotFound(w, r)
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return
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}
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AddBrowserHeaders(w)
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f := func(format string, args ...any) { fmt.Fprintf(w, format, args...) }
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f("<html><body><h1>%s debug</h1><ul>", version.CmdName())
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for _, kv := range d.kvs {
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kv(w)
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}
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for _, url := range d.urls {
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io.WriteString(w, url)
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}
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for _, section := range d.sections {
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section(w, r)
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}
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}
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func (d *DebugHandler) handle(slug string, handler http.Handler) string {
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href := "GET /debug/" + slug
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d.mux.Handle(href, Protected(debugBrowserHeaderHandler(handler)))
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return href
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}
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// Handle registers handler at /debug/<slug> and creates a descriptive
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// entry in /debug/ for it.
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func (d *DebugHandler) Handle(slug, desc string, handler http.Handler) {
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href := d.handle(slug, handler)
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d.URL(href, desc)
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}
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// HandleSilent registers handler at /debug/<slug>. It does not create
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// a descriptive entry in /debug/ for it. This should be used
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// sparingly, for things that need to be registered but would pollute
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// the list of debug links.
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func (d *DebugHandler) HandleSilent(slug string, handler http.Handler) {
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d.handle(slug, handler)
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}
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// KV adds a key/value list item to /debug/.
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func (d *DebugHandler) KV(k string, v any) {
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val := html.EscapeString(fmt.Sprintf("%v", v))
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d.kvs = append(d.kvs, func(w io.Writer) {
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fmt.Fprintf(w, "<li><b>%s:</b> %s</li>", k, val)
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})
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}
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// KVFunc adds a key/value list item to /debug/. v is called on every
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// render of /debug/.
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func (d *DebugHandler) KVFunc(k string, v func() any) {
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d.kvs = append(d.kvs, func(w io.Writer) {
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val := html.EscapeString(fmt.Sprintf("%v", v()))
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fmt.Fprintf(w, "<li><b>%s:</b> %s</li>", k, val)
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})
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}
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// URL adds a URL and description list item to /debug/.
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func (d *DebugHandler) URL(url, desc string) {
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if desc != "" {
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desc = " (" + desc + ")"
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}
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d.urls = append(d.urls, fmt.Sprintf(`<li><a href="%s">%s</a>%s</li>`, url, url, html.EscapeString(desc)))
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}
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// Section invokes f on every render of /debug/ to add supplemental
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// HTML to the page body.
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func (d *DebugHandler) Section(f func(w io.Writer, r *http.Request)) {
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d.sections = append(d.sections, f)
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}
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func gcHandler(w http.ResponseWriter, r *http.Request) {
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w.Write([]byte("running GC...\n"))
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if f, ok := w.(http.Flusher); ok {
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f.Flush()
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}
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runtime.GC()
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w.Write([]byte("Done.\n"))
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}
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// debugBrowserHeaderHandler is a wrapper around BrowserHeaderHandler with a
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// more relaxed Content-Security-Policy that's acceptable for internal debug
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// pages. It should not be used on any public-facing handlers!
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func debugBrowserHeaderHandler(h http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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AddBrowserHeaders(w)
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// The only difference from AddBrowserHeaders is that this policy
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// allows inline CSS styles. They make debug pages much easier to
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// prototype, while the risk of user-injected CSS is relatively low.
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w.Header().Set("Content-Security-Policy", "default-src 'self'; frame-ancestors 'none'; form-action 'self'; base-uri 'self'; block-all-mixed-content; object-src 'none'; style-src 'self' 'unsafe-inline'")
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h.ServeHTTP(w, r)
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})
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}
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