webhooker/internal/middleware/clientip_test.go

package middleware_test

import (
	"bytes"
	"context"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/middleware"
)

const (
	// forwardedChain is the X-Forwarded-For a request arrives with:
	// the client, then a second proxy inside trustedProxyCIDR that the
	// request passed through before reaching trustedPeer.
	forwardedChain = clientIPv4 + ", 10.0.0.2"

	// untrustedPeer is a peer outside trustedProxyCIDR, so its
	// X-Forwarded-For is ignored and the peer is the client.
	untrustedPeer = "192.0.2.10:5555"

	// oneRequestPerMinute is the receiver limit these tests install:
	// the second request on a path is rejected, and the aggregate
	// limit is ReceiverAggregateMultiplierConst.
	oneRequestPerMinute = 1
)

// clientLogSite is one log line that names the client. build wraps the
// middleware that writes it around a handler, and requests is how many
// identical requests it takes before the line is written.
type clientLogSite struct {
	build    func(m *middleware.Middleware) http.Handler
	requests int
}

// clientLogSites maps the message of each line that names the client
// to the way to make it be written.
func clientLogSites() map[string]clientLogSite {
	served := func(*middleware.Middleware) http.Handler {
		return okHandler()
	}

	receiver := func(m *middleware.Middleware) http.Handler {
		return m.ReceiverRateLimit()(okHandler())
	}

	login := func(m *middleware.Middleware) http.Handler {
		return http.HandlerFunc(
			func(w http.ResponseWriter, r *http.Request) {
				m.RecordLoginFailure(r, "someone")
				w.WriteHeader(http.StatusUnauthorized)
			},
		)
	}

	csrf := func(m *middleware.Middleware) http.Handler {
		return m.CSRF(http.HandlerFunc(forbidden))(okHandler())
	}

	return map[string]clientLogSite{
		"http request": {
			build:    served,
			requests: 1,
		},
		"webhook receiver rate limit exceeded": {
			build:    receiver,
			requests: oneRequestPerMinute + 1,
		},
		// The aggregate limit sits in front of the per-entrypoint
		// one, so the requests that one rejects count towards it.
		"webhook receiver aggregate rate limit exceeded": {
			build: receiver,
			requests: middleware.ReceiverAggregateMultiplierConst*
				oneRequestPerMinute + 1,
		},
		"login failure limit exceeded": {
			build:    login,
			requests: middleware.LoginRateLimitConst + 1,
		},
		"csrf: token validation failed": {
			build:    csrf,
			requests: 1,
		},
	}
}

// clientLogLines sends the site's requests from peer, each carrying
// forwardedChain, through Logging and then the site, as production
// does, and returns the logged lines whose message is msg.
func clientLogLines(
	t *testing.T, site clientLogSite, msg, peer string,
) []map[string]any {
	t.Helper()

	buf := new(bytes.Buffer)
	log := slog.New(slog.NewJSONHandler(
		buf,
		&slog.HandlerOptions{Level: slog.LevelDebug},
	))

	cfg := &config.Config{
		Environment:       config.EnvironmentDev,
		ReceiverRateLimit: oneRequestPerMinute,
		TrustedProxies:    trustedProxies(trustedProxyCIDR),
	}

	m := middleware.NewForTest(
		log, cfg, newTestSessionManager(cfg, log, nil),
	)
	handler := m.Logging()(site.build(m))

	for range site.requests {
		req := httptest.NewRequestWithContext(
			context.Background(), http.MethodPost, "/h/x", nil,
		)
		req.RemoteAddr = peer
		req.Header.Set(headerXFF, forwardedChain)

		handler.ServeHTTP(httptest.NewRecorder(), req)
	}

	var lines []map[string]any

	for _, entry := range accessLogEntries(t, buf) {
		if entry["msg"] == msg {
			lines = append(lines, entry)
		}
	}

	return lines
}

// TestClientIP_LoggedNextToThePeer checks that every line that names
// the client carries both addresses: remoteIP, the connecting peer,
// and clientIP, the client the rate limiters key on.
func TestClientIP_LoggedNextToThePeer(t *testing.T) {
	t.Parallel()

	cases := map[string]struct {
		peer       string
		wantRemote string
		wantClient string
	}{
		"trusted proxy with a forwarded chain": {
			peer:       trustedPeer,
			wantRemote: "10.0.0.1",
			wantClient: clientIPv4,
		},
		"untrusted peer": {
			peer:       untrustedPeer,
			wantRemote: "192.0.2.10",
			wantClient: "192.0.2.10",
		},
	}

	for msg, site := range clientLogSites() {
		for name, tc := range cases {
			t.Run(msg+"/"+name, func(t *testing.T) {
				t.Parallel()

				lines := clientLogLines(t, site, msg, tc.peer)
				require.NotEmpty(t, lines, "%q was never logged", msg)

				for _, line := range lines {
					assert.Equal(t, tc.wantRemote, line["remoteIP"])
					assert.Equal(t, tc.wantClient, line["clientIP"])
				}
			})
		}
	}
}