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7c04846eac
Allow inline CSS for debug handlers to make prototyping easier. These are generally not accessible to the public and the small risk of CSS injection via user content seems acceptable. Also allow form submissions on the same domain, instead of banning all forms. An example of such form is http://webhooks.corp.ts.net:6359/debug/private-nodes/ Updates #3576 Signed-off-by: Andrew Lytvynov <awly@tailscale.com>
158 lines
5.2 KiB
Go
158 lines
5.2 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, pat := mux.Handler(&http.Request{URL: &url.URL{Path: "/debug/"}})
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if d, ok := h.(*DebugHandler); ok && pat == "/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("/debug/", ret)
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// Register this one directly on mux, rather than using
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// ret.URL/etc, as we don't need another line of output on the
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// index page. The /pprof/ index already covers it.
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mux.Handle("/debug/pprof/profile", BrowserHeaderHandler(http.HandlerFunc(pprof.Profile)))
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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("vars", "Metrics (Go)", expvar.Handler())
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ret.Handle("varz", "Metrics (Prometheus)", http.HandlerFunc(promvarz.Handler))
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ret.Handle("pprof/", "pprof", http.HandlerFunc(pprof.Index))
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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("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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// 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 := "/debug/" + slug
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d.mux.Handle(href, Protected(debugBrowserHeaderHandler(handler)))
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d.URL(href, desc)
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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; plugin-types '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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