mesh-controller/examples/route-proxy/policy_test.go

package main

import (
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"testing"

	"golang.org/x/crypto/bcrypt"
)

// What a route carries about the requests arriving at it — novox/hq ADR 0108.
//
// Each test here is one of the four capabilities that record closed the set at, plus the negative
// case it promised would be refused. The negative case is the one that rots quietly: nothing fails
// if it stops working, so nothing tells you it has.

// served starts a workload and gives back the host and port the mesh would have recorded for it.
func served(t *testing.T, body string) (string, int) {
	t.Helper()
	workload := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte(body))
	}))
	t.Cleanup(workload.Close)
	host, port, _ := strings.Cut(strings.TrimPrefix(workload.URL, "http://"), ":")
	n, err := strconv.Atoi(port)
	if err != nil {
		t.Fatal(err)
	}
	return host, n
}

// ask makes one request through the proxy for a given name and path, without following redirects.
func ask(t *testing.T, proxy, name, path string, auth [2]string) *http.Response {
	t.Helper()
	req, err := http.NewRequest(http.MethodGet, proxy+path, nil)
	if err != nil {
		t.Fatal(err)
	}
	req.Host = name
	if auth[0] != "" {
		req.SetBasicAuth(auth[0], auth[1])
	}
	client := &http.Client{CheckRedirect: func(*http.Request, []*http.Request) error {
		return http.ErrUseLastResponse
	}}
	answer, err := client.Do(req)
	if err != nil {
		t.Fatal(err)
	}
	t.Cleanup(func() { _ = answer.Body.Close() })
	return answer
}

func proxyFor(t *testing.T, routesJSON string) string {
	t.Helper()
	path := filepath.Join(t.TempDir(), "routes.json")
	if err := os.WriteFile(path, []byte(routesJSON), 0o644); err != nil {
		t.Fatal(err)
	}
	routes, err := routesFrom(path)
	if err != nil {
		t.Fatal(err)
	}
	held := newTable()
	held.set(routes)
	server := httptest.NewServer(handler(held))
	t.Cleanup(server.Close)
	return server.URL
}

// A refusal on a path shadows the ordinary route for that path and leaves every other path alone.
//
// **This is why path scoping is a prerequisite and not a sibling capability.** The rule being
// reproduced matches a path on a host that is already routed to a workload, so a table mapping a
// host to one target cannot express it at all — no amount of authentication or source filtering
// would have helped.
func TestARefusedPathShadowsTheRouteAndLeavesTheRestServed(t *testing.T) {
	at, port := served(t, "the workload")
	proxy := proxyFor(t, `{"given":[
	  {"from":"forge","node":"anchor","at":"`+at+`","values":{"name":"forge.example","port":`+strconv.Itoa(port)+`}},
	  {"from":"forge","node":"anchor","values":{"name":"forge.example","path":"/api/internal","priority":100,"deny":true}}
	]}`)

	if got := ask(t, proxy, "forge.example", "/api/internal/hook", [2]string{}).StatusCode; got != http.StatusForbidden {
		t.Fatalf("the refused path answered %d, so the block that was put in front of it during an "+
			"incident is not in front of it any more", got)
	}
	if got := ask(t, proxy, "forge.example", "/", [2]string{}).StatusCode; got != http.StatusOK {
		t.Fatalf("refusing one path took the whole route with it: %d", got)
	}
}

// A redirect answers with the redirect, and the request keeps its own path and query.
//
// Losing the path would turn canonicalising one name onto another into "every deep link now lands
// on the front page", which is the kind of breakage that produces no error anywhere.
func TestARedirectKeepsThePathAndQuery(t *testing.T) {
	proxy := proxyFor(t, `{"given":[
	  {"from":"site","node":"anchor","values":{"name":"www.example","redirect":"https://example/"}}
	]}`)

	answer := ask(t, proxy, "www.example", "/deep/page?ref=1", [2]string{})
	if answer.StatusCode != http.StatusMovedPermanently {
		t.Fatalf("a declared redirect answered %d", answer.StatusCode)
	}
	where := answer.Header.Get("Location")
	if !strings.Contains(where, "/deep/page") || !strings.Contains(where, "ref=1") {
		t.Fatalf("the redirect dropped the path or the query: %q", where)
	}
}

// Authentication refuses a request with no credentials, admits one with the right ones, and refuses
// the wrong ones — with the credentials read from the secret the declaration *named*.
func TestAuthenticationAdmitsOnlyWhatTheSecretSays(t *testing.T) {
	at, port := served(t, "the console")
	hash, err := bcrypt.GenerateFromPassword([]byte("correct horse"), bcrypt.MinCost)
	if err != nil {
		t.Fatal(err)
	}
	secret := filepath.Join(t.TempDir(), "console-auth")
	if err := os.WriteFile(secret, []byte("# a comment\nadmin:"+string(hash)+"\n"), 0o600); err != nil {
		t.Fatal(err)
	}

	proxy := proxyFor(t, `{"given":[
	  {"from":"console","node":"anchor","at":"`+at+`","values":{"name":"console.example","port":`+strconv.Itoa(port)+`,"auth":"`+secret+`"}}
	]}`)

	if got := ask(t, proxy, "console.example", "/", [2]string{}).StatusCode; got != http.StatusUnauthorized {
		t.Fatalf("an admin surface with no login of its own answered %d without credentials", got)
	}
	if got := ask(t, proxy, "console.example", "/", [2]string{"admin", "wrong"}).StatusCode; got != http.StatusUnauthorized {
		t.Fatalf("the wrong password answered %d", got)
	}
	if got := ask(t, proxy, "console.example", "/", [2]string{"admin", "correct horse"}).StatusCode; got != http.StatusOK {
		t.Fatalf("the right password answered %d", got)
	}
}

// The negative case ADR 0108 promised would be refused: a credential in the declaration.
//
// **Refused whole, not tolerated and not served unprotected.** A hash carried in a declaration was
// the rejected option; nothing in the running system should quietly accept it later, because the
// precedent is far easier to set than to withdraw. If this test is deleted the option returns and
// nothing else notices.
func TestACredentialInTheDeclarationIsRefusedRatherThanServed(t *testing.T) {
	inline := []string{
		`{"given":[{"from":"c","node":"n","at":"127.0.0.1","values":{"name":"c.example","port":8080,"auth":"admin:$2a$10$abcdefghijklmnopqrstuv"}}]}`,
		`{"given":[{"from":"c","node":"n","at":"127.0.0.1","values":{"name":"c.example","port":8080,"auth":"$2a$10$abcdefghijklmnopqrstuv"}}]}`,
	}
	for _, body := range inline {
		path := filepath.Join(t.TempDir(), "routes.json")
		if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
			t.Fatal(err)
		}
		routes, err := routesFrom(path)
		if err != nil {
			t.Fatal(err)
		}
		if len(routes) != 0 {
			t.Fatalf("a declaration carrying a credential was served anyway: %v", routes)
		}
	}
}

// Authentication declared, secret unreadable: the route refuses. It does not serve unprotected.
//
// **Fail closed.** The alternative turns a missing file into a silently public admin surface, which
// is the outcome the whole record exists to prevent. It answers rather than 404s, so an operator
// sees "cannot read the credentials" instead of concluding the route was withdrawn.
func TestAnUnreadableSecretFailsClosed(t *testing.T) {
	at, port := served(t, "the console")
	missing := filepath.Join(t.TempDir(), "not-mounted")

	proxy := proxyFor(t, `{"given":[
	  {"from":"console","node":"anchor","at":"`+at+`","values":{"name":"console.example","port":`+strconv.Itoa(port)+`,"auth":"`+missing+`"}}
	]}`)

	answer := ask(t, proxy, "console.example", "/", [2]string{})
	if answer.StatusCode == http.StatusOK {
		t.Fatal("a route whose credentials could not be read served the workload unprotected")
	}
	if answer.StatusCode != http.StatusServiceUnavailable {
		t.Fatalf("expected the route to say it cannot check, got %d", answer.StatusCode)
	}
}

// Equal priorities resolve the same way every time, so the same declaration serves the same way
// after a restart.
//
// Sorting only by priority leaves rules that share one in whatever order the map produced. The
// proxy would still work, and would work differently between restarts — which is the hardest kind
// of fault to believe when it is reported.
func TestRulesThatShareAPriorityAreStillTotallyOrdered(t *testing.T) {
	first := []rule{
		{path: "/a", priority: 10, target: "http://x:1"},
		{path: "/bb", priority: 10, target: "http://y:2"},
		{path: "", priority: 10, target: "http://z:3"},
	}
	second := []rule{
		{path: "", priority: 10, target: "http://z:3"},
		{path: "/bb", priority: 10, target: "http://y:2"},
		{path: "/a", priority: 10, target: "http://x:1"},
	}
	inOrder(first)
	inOrder(second)
	for i := range first {
		if first[i].path != second[i].path || first[i].target != second[i].target {
			t.Fatalf("two orderings of the same rules disagree at %d: %q vs %q",
				i, first[i].path, second[i].path)
		}
	}
	// And the more specific rule is matched first, which is the intuitive reading.
	if first[0].path != "/bb" {
		t.Fatalf("the longest path is not matched first: %q", first[0].path)
	}
}

// Priority decides before path length does, so a rule can be made to win regardless of specificity.
func TestPriorityOutranksPathLength(t *testing.T) {
	rules := []rule{
		{path: "/very/long/path", priority: 1, target: "http://x:1"},
		{path: "", priority: 100, target: "http://y:2"},
	}
	inOrder(rules)
	if rules[0].priority != 100 {
		t.Fatalf("a higher priority did not win: %+v", rules[0])
	}
}

// A priority above a port number survives, because a priority is an ordering and not a port.
//
// **Found by review, and it was load-bearing.** Priority was first read with the port reader, which
// caps at 65535 — so a rule declared above that silently became priority 0 and stopped shadowing the
// route it exists to shadow. The one real rule this has to reproduce is declared at 100000, so the
// capability would have shipped looking complete and doing nothing.
func TestAPriorityAboveAPortNumberSurvives(t *testing.T) {
	at, port := served(t, "the workload")
	proxy := proxyFor(t, `{"given":[
	  {"from":"forge","node":"anchor","at":"`+at+`","values":{"name":"forge.example","port":`+strconv.Itoa(port)+`}},
	  {"from":"forge","node":"anchor","values":{"name":"forge.example","path":"/api/internal","priority":100000,"deny":true}}
	]}`)

	if got := ask(t, proxy, "forge.example", "/api/internal/hook", [2]string{}).StatusCode; got != http.StatusForbidden {
		t.Fatalf("a rule declared at priority 100000 answered %d instead of refusing", got)
	}
}

// A host routed only on some paths says so, rather than claiming the name is not served here.
//
// Saying "no route for this name" while listing that very name as served is a contradiction an
// operator has to disbelieve the proxy to get past — and path scoping makes it reachable, because a
// host can now have rules that none of this request's paths match.
func TestAHostRoutedOnlyOnSomePathsSaysSo(t *testing.T) {
	proxy := proxyFor(t, `{"given":[
	  {"from":"forge","node":"anchor","values":{"name":"forge.example","path":"/api/internal","deny":true}}
	]}`)

	answer := ask(t, proxy, "forge.example", "/elsewhere", [2]string{})
	if answer.StatusCode != http.StatusNotFound {
		t.Fatalf("an uncovered path answered %d", answer.StatusCode)
	}
	body := make([]byte, 256)
	n, _ := answer.Body.Read(body)
	said := string(body[:n])
	if !strings.Contains(said, "is served here") || !strings.Contains(said, "/elsewhere") {
		t.Fatalf("the refusal does not distinguish an uncovered path from an unserved name: %q", said)
	}
}