webhooker/internal/server/sentry_test.go

package server_test

import (
	"context"
	"encoding/json"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/getsentry/sentry-go"
	sentryhttp "github.com/getsentry/sentry-go/http"
	"github.com/go-chi/chi"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/server"
)

// The four markers below are the credentials a captured event could
// carry off-host, one per field of sentry.Request that the SDK fills
// from the request without a SendDefaultPII guard.
const (
	// sentryBodyMarker is submitted as a form value. Since every
	// handler reads its fields with PostFormValue, the body is the
	// only place a password or a target URL is ever supplied.
	sentryBodyMarker = "QQSENTRYBODYMARKERQQ"

	// sentryQueryMarker rides the request line.
	sentryQueryMarker = "T00000000/B00000000/QQSENTRYQUERYMARKERQQ"

	// sentryHeaderMarker rides X-Csrf-Token, which gorilla/csrf
	// accepts in place of the form field.
	sentryHeaderMarker = "QQSENTRYHEADERMARKERQQ"

	// sentryReceiverUUID is the entrypoint identifier in the path of
	// a receiver request. It is a write capability: anyone holding
	// it can POST events this service accepts and its targets then
	// deliver, so it may not reach a third-party tracker.
	sentryReceiverUUID = "6d1f9c2a-3b7e-4f58-9a0d-c0ffeebadc0d"
)

// sentryKeptUserAgent is a non-secret header value planted so the
// assertions below cannot pass by the event carrying no headers at
// all.
const sentryKeptUserAgent = "webhooker-test-agent"

// captureTransport records events instead of shipping them, so a test
// sees exactly the payload the SDK would have put on the wire.
type captureTransport struct {
	mu     sync.Mutex
	events []*sentry.Event
}

func (c *captureTransport) Configure(sentry.ClientOptions) {}

func (c *captureTransport) Flush(time.Duration) bool { return true }

func (c *captureTransport) SendEvent(event *sentry.Event) {
	c.mu.Lock()
	defer c.mu.Unlock()

	c.events = append(c.events, event)
}

// sentryCase drives one request through the real sentryhttp middleware
// inside a real chi router and returns the events the SDK produced.
//
// Routing through a chi mux is load-bearing, not decoration. chi puts
// its routing context on the request context before the middleware
// chain runs and fills it in as it matches, so a hand-built request
// carries no route pattern at all and could not distinguish the hook
// working from the hook falling back.
//
// This is also the only construction path on which Request.Data
// appears: sentryhttp calls Scope.SetRequest, which tees r.Body into a
// 10 KiB buffer, ParseForm drains the tee, and Scope.ApplyToEvent
// copies the buffer into the event inside prepareEvent — before
// BeforeSend runs. A hand-built sentry.NewRequest never reads the body
// and so cannot regress-test any of it.
type sentryCase struct {
	// scrub selects whether the production BeforeSend hooks are
	// installed, so the same path shows both what the SDK collects
	// and what survives.
	scrub bool

	// tracing enables the transaction dispatch, which the service
	// leaves off. With it on, a served request produces a
	// transaction event through BeforeSendTransaction.
	tracing bool

	// panics selects the error dispatch, via BeforeSend.
	panics bool

	// request builds the request to serve, given the client whose
	// hub it must carry.
	request func(*sentry.Client) *http.Request
}

func (c sentryCase) capture(t *testing.T) []*sentry.Event {
	t.Helper()

	transport := &captureTransport{}

	opts := server.SentryClientOptionsForTest(
		"https://public@sentry.invalid/1", "webhooker-test",
	)
	opts.Transport = transport

	if !c.scrub {
		opts.BeforeSend = nil
		opts.BeforeSendTransaction = nil
	}

	if c.tracing {
		opts.EnableTracing = true
		opts.TracesSampleRate = 1.0
	}

	client, err := sentry.NewClient(opts)
	require.NoError(t, err)

	c.router().ServeHTTP(httptest.NewRecorder(), c.request(client))

	return transport.events
}

// router mirrors the one ordering these tests depend on, over the two
// route patterns they need: a recovering middleware outside, then the
// sentryhttp handler registered with Use and Repanic set, exactly as
// routes.go orders the two. The bare recover stands in for
// Middleware.Recoverer, which holds that outer slot in production; it
// is here only to keep panic stacks out of the test output. That the
// production one really does catch what sentryhttp re-raises is
// pinned separately, by TestSentryStillSeesAPanic.
func (c sentryCase) router() http.Handler {
	handler := func(_ http.ResponseWriter, r *http.Request) {
		// This call is what drains the body tee and fills the
		// buffer. Its success is asserted by the unscrubbed case
		// below, which sees the body in the event.
		_ = r.ParseForm()

		if c.panics {
			panic("boom")
		}
	}

	router := chi.NewRouter()
	router.Use(recoveringMiddleware)
	router.Use(
		sentryhttp.New(sentryhttp.Options{Repanic: true}).Handle,
	)
	router.HandleFunc("/pages/login", handler)
	router.HandleFunc("/webhook/{uuid}", handler)

	return router
}

func recoveringMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(
		func(w http.ResponseWriter, r *http.Request) {
			defer func() { _ = recover() }()

			next.ServeHTTP(w, r)
		},
	)
}

// sentryLoginRequest builds the password POST most cases drive, with a
// credential planted in the body, the query and a header.
func sentryLoginRequest(client *sentry.Client) *http.Request {
	form := url.Values{}
	form.Set("username", "admin")
	form.Set("password", sentryBodyMarker)

	req := sentryRequest(
		client,
		"/pages/login?url=https://hooks.slack.com/services/"+
			sentryQueryMarker,
		form.Encode(),
	)

	req.Header.Set("X-Csrf-Token", sentryHeaderMarker)

	return req
}

// sentryReceiverRequest builds a POST to the receiver route, whose
// concrete path carries the entrypoint capability.
func sentryReceiverRequest(client *sentry.Client) *http.Request {
	return sentryRequest(
		client, "/webhook/"+sentryReceiverUUID, "payload=hello",
	)
}

func sentryRequest(
	client *sentry.Client,
	target, body string,
) *http.Request {
	req := httptest.NewRequestWithContext(
		sentry.SetHubOnContext(
			context.Background(),
			sentry.NewHub(client, sentry.NewScope()),
		),
		http.MethodPost,
		target,
		strings.NewReader(body),
	)

	req.Header.Set(
		"Content-Type", "application/x-www-form-urlencoded",
	)
	req.Header.Set("User-Agent", sentryKeptUserAgent)

	return req
}

// marshalEvent encodes an event the way the transport does.
func marshalEvent(t *testing.T, event *sentry.Event) string {
	t.Helper()

	encoded, err := json.Marshal(event)
	require.NoError(t, err)

	return string(encoded)
}

// onlyEvent asserts a single event was captured and returns it.
func onlyEvent(t *testing.T, events []*sentry.Event) *sentry.Event {
	t.Helper()

	require.Len(t, events, 1)
	require.NotNil(t, events[0].Request)

	return events[0]
}

// TestSentryScrub_SDKCollectsTheRequestUnscrubbed pins the premise the
// hook exists for. Without it the SDK ships the whole POST body, the
// raw query, the CSRF header and the concrete request path, none of
// which SendDefaultPII=false suppresses.
func TestSentryScrub_SDKCollectsTheRequestUnscrubbed(t *testing.T) {
	t.Parallel()

	event := onlyEvent(t, sentryCase{
		panics:  true,
		request: sentryLoginRequest,
	}.capture(t))

	assert.Contains(
		t, event.Request.Data, sentryBodyMarker,
		"the SDK is expected to collect the POST body; if it no "+
			"longer does, the scrub hook's premise changed",
	)
	assert.Contains(t, event.Request.QueryString, sentryQueryMarker)
	assert.Contains(
		t, marshalEvent(t, event), sentryHeaderMarker,
	)

	receiver := onlyEvent(t, sentryCase{
		panics:  true,
		request: sentryReceiverRequest,
	}.capture(t))

	assert.Contains(
		t, receiver.Request.URL, sentryReceiverUUID,
		"the SDK is expected to build Request.URL from the "+
			"concrete path; if it no longer does, the route "+
			"pattern rewrite's premise changed",
	)
}

// TestSentryScrub_RedactsTheCapturedRequest is the regression test: no
// byte of any planted credential may survive into the marshalled event
// that leaves the process.
func TestSentryScrub_RedactsTheCapturedRequest(t *testing.T) {
	t.Parallel()

	event := onlyEvent(t, sentryCase{
		scrub:   true,
		panics:  true,
		request: sentryLoginRequest,
	}.capture(t))

	encoded := marshalEvent(t, event)

	assert.NotContains(t, encoded, sentryBodyMarker)
	assert.NotContains(t, encoded, sentryQueryMarker)
	assert.NotContains(t, encoded, sentryHeaderMarker)
	assert.NotContains(t, encoded, "hooks.slack.com")

	assert.Equal(t, "(redacted)", event.Request.Data)
	assert.Equal(t, "(redacted)", event.Request.QueryString)
	assert.Empty(t, event.Request.Cookies)
	assert.Empty(t, event.Request.Env)
}

// TestSentryScrub_ReplacesTheCapabilityPathWithTheRoutePattern is the
// regression test for the receiver URL: the entrypoint UUID is a write
// capability and may not reach the tracker, while the route it names
// must still be readable there.
func TestSentryScrub_ReplacesTheCapabilityPathWithTheRoutePattern(
	t *testing.T,
) {
	t.Parallel()

	event := onlyEvent(t, sentryCase{
		scrub:   true,
		panics:  true,
		request: sentryReceiverRequest,
	}.capture(t))

	assert.NotContains(
		t, marshalEvent(t, event), sentryReceiverUUID,
	)
	assert.Equal(
		t, "http://example.com/webhook/{uuid}", event.Request.URL,
	)
}

// TestSentryScrub_KeepsTheRoutingContext checks the hook does not cost
// the debugging signal: the route, its scheme and host, the method and
// the metadata headers still identify what failed. On a static route
// the pattern is the path, so the URL is unchanged there.
func TestSentryScrub_KeepsTheRoutingContext(t *testing.T) {
	t.Parallel()

	event := onlyEvent(t, sentryCase{
		scrub:   true,
		panics:  true,
		request: sentryLoginRequest,
	}.capture(t))

	assert.Equal(
		t, "http://example.com/pages/login", event.Request.URL,
	)
	assert.Equal(t, http.MethodPost, event.Request.Method)
	assert.Equal(
		t,
		sentryKeptUserAgent,
		event.Request.Headers["User-Agent"],
	)
	assert.Equal(
		t,
		"application/x-www-form-urlencoded",
		event.Request.Headers["Content-Type"],
	)
}

// TestSentryScrub_RedactsTheTransactionDispatch covers the other hook.
// Span.doFinish captures with a nil hint, so BeforeSendTransaction
// gets one with no context and no request: the route pattern is out of
// reach and both the URL and the SDK-built transaction name have to
// fall back. Tracing is off in this service, so no transaction event
// is produced today; the hook is a floor against that changing.
func TestSentryScrub_RedactsTheTransactionDispatch(t *testing.T) {
	t.Parallel()

	events := sentryCase{
		scrub:   true,
		tracing: true,
		request: sentryReceiverRequest,
	}.capture(t)

	event := onlyEvent(t, events)
	require.Equal(t, "transaction", event.Type)

	assert.NotContains(
		t, marshalEvent(t, event), sentryReceiverUUID,
	)
	assert.Equal(
		t, "http://example.com/(redacted)", event.Request.URL,
	)
	assert.Equal(t, "POST /(redacted)", event.Transaction)
}

// TestSentryScrub_TransactionDispatchIsUnscrubbedWithoutTheHook pins
// that dispatch's premise the same way, since it is the one the
// service does not exercise today.
func TestSentryScrub_TransactionDispatchIsUnscrubbedWithoutTheHook(
	t *testing.T,
) {
	t.Parallel()

	event := onlyEvent(t, sentryCase{
		tracing: true,
		request: sentryReceiverRequest,
	}.capture(t))

	require.Equal(t, "transaction", event.Type)
	assert.Contains(t, event.Request.URL, sentryReceiverUUID)
	assert.Contains(t, event.Transaction, sentryReceiverUUID)
}

// TestSentryScrub_FallsBackWithoutARoutePattern covers every way the
// pattern can be missing. None of them may fall back to the concrete
// path, and all of them keep the scheme, which is the CSRF TLS
// decision.
func TestSentryScrub_FallsBackWithoutARoutePattern(t *testing.T) {
	t.Parallel()

	concrete := "https://example.com/webhook/" + sentryReceiverUUID

	// A request with no chi routing context on it at all, which is
	// what an event captured outside the router would carry.
	unrouted := httptest.NewRequestWithContext(
		context.Background(), http.MethodPost, concrete, nil,
	)

	for name, hint := range map[string]*sentry.EventHint{
		"no hint":    nil,
		"no context": {},
		"no request": {Context: context.Background()},
		"unrouted request": {
			Context: context.WithValue(
				context.Background(),
				sentry.RequestContextKey,
				unrouted,
			),
		},
	} {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			event := sentry.NewEvent()
			event.Request = &sentry.Request{URL: concrete}
			event.Transaction = "POST /webhook/" +
				sentryReceiverUUID

			scrubbed := server.ScrubSentryRequestForTest(
				event, hint,
			)
			require.NotNil(t, scrubbed)

			assert.Equal(
				t,
				"https://example.com/(redacted)",
				scrubbed.Request.URL,
			)
			assert.Equal(
				t, "POST /(redacted)", scrubbed.Transaction,
			)
			assert.NotContains(
				t,
				marshalEvent(t, scrubbed),
				sentryReceiverUUID,
			)
		})
	}
}

// TestSentryScrub_WithholdsUnparseableValues covers the shapes the
// rewrite cannot take apart. Withholding them whole is the safe
// answer, since nothing can be said about which part is a path.
func TestSentryScrub_WithholdsUnparseableValues(t *testing.T) {
	t.Parallel()

	event := sentry.NewEvent()
	event.Request = &sentry.Request{
		URL: "/webhook/" + sentryReceiverUUID,
	}
	event.Transaction = "/webhook/" + sentryReceiverUUID

	scrubbed := server.ScrubSentryRequestForTest(event, nil)
	require.NotNil(t, scrubbed)

	assert.Equal(t, "(redacted)", scrubbed.Request.URL)
	assert.Equal(t, "(redacted)", scrubbed.Transaction)
}

// TestSentryScrub_ToleratesEventsWithoutARequest covers the events the
// hook sees outside an HTTP handler, where no request is attached.
func TestSentryScrub_ToleratesEventsWithoutARequest(t *testing.T) {
	t.Parallel()

	scrubbed := server.ScrubSentryRequestForTest(
		sentry.NewEvent(), nil,
	)

	require.NotNil(t, scrubbed)
	assert.Nil(t, scrubbed.Request)
	assert.Empty(t, scrubbed.Transaction)
	assert.Nil(t, server.ScrubSentryRequestForTest(nil, nil))
}