examples/route-proxy/main.go

@@ -10,10 +10,31 @@
 // program. What lives here is that contract, written as something that runs so it can be read
 // rather than described.
 //
+// **A route also carries what a request arriving at it may do** (novox/hq ADR 0108). The grant used
+// to say only where to send traffic, so this proxy applied nothing; the four things the ingress it
+// replaces actually relies on are now part of the contribution. The set is closed at four, because
+// an open middleware surface recreates the thing being replaced and is far harder to narrow later
+// than a closed one is to widen.
+//
 // What it is given, written by the host from an ordinary declaration:
 //
 //	$ROUTES    every consumer, the name it asked for, and where the mesh says that machine is
 //
+// Each contribution's values carry the name and port as before, and optionally:
+//
+//	path       the path prefix this rule is scoped to; absent means every path
+//	priority   which rule wins where two match; higher first, and the order is total
+//	deny       refuse the request outright — the shape an incident mitigation needs
+//	redirect   answer with a permanent redirect to this name, keeping the path and query
+//	auth       the *path of a secret* holding `user:hash` lines, never the credential itself
+//
+// A host may appear more than once, which is what path scoping means: one rule refusing a path
+// while another serves everything else on the same name.
+//
+// **`auth` names a secret and never holds one.** A declaration carrying a credential is refused
+// outright rather than served unprotected, and a secret that cannot be read makes the route refuse
+// rather than open — a gate that cannot check is not a gate that opens.
+//
 // It re-reads on change rather than being restarted, for the same reason the provisioner does:
 // a route arriving or leaving is an ordinary event and must not drop the connections of every
 // other workload.
@@ -23,6 +44,7 @@ import (
 	"bytes"
 	"context"
 	"crypto/sha256"
+	"crypto/subtle"
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/hex"
@@ -42,6 +64,7 @@ import (
 
 	"golang.org/x/crypto/acme"
 	"golang.org/x/crypto/acme/autocert"
+	"golang.org/x/crypto/bcrypt"
 )
 
 // Where public certificates come from when nothing says otherwise.
@@ -74,7 +97,7 @@ func issuer() string {
 // to what it may serve.
 func onlyWhatTheMeshSaid(held *table) autocert.HostPolicy {
 	return func(_ context.Context, host string) error {
-		if _, known := held.find(host); known {
+		if held.routed(host) {
 			return nil
 		}
 		return fmt.Errorf("no route for %q in this mesh, so no certificate is asked for", host)
@@ -95,48 +118,145 @@ type contribution struct {
 	Values map[string]any `json:"values"`
 }
 
+// policy is what a rule does with a request that matched it.
+//
+// **Decided by the mesh, not here** (novox/hq ADR 0108). A route grant used to hand back a name and
+// say nothing about what the name admitted, so this proxy admitted everything. The set is closed at
+// four — authentication, refusal, path scoping, redirect — because an open middleware surface
+// recreates the thing being replaced and is far harder to narrow later than a closed one is to widen.
+type policy struct {
+	// deny refuses the request outright, whatever it is.
+	deny bool
+	// redirectTo answers with a permanent redirect instead of proxying. The request's own path and
+	// query are carried across, which is what canonicalising one public name onto another means.
+	redirectTo string
+	// users is what a request must present, read at load time from the secret the declaration
+	// *named*. A declaration never carries the credential itself.
+	users map[string]string
+	// sealed is set when authentication was declared and the secret could not be read. The rule then
+	// refuses everything and says why.
+	//
+	// **Fail closed.** The alternative — serve the route unauthenticated because the gate is
+	// missing — turns an unreadable file into a silently public admin surface, which is the exact
+	// outcome ADR 0108 exists to prevent. A gate that cannot check is not a gate that opens.
+	sealed string
+}
+
+// rule is one way a host may be routed. A host may have several, which is what path scoping means.
+type rule struct {
+	path     string // "" matches every path
+	priority int
+	policy   policy
+	to       *httputil.ReverseProxy
+	target   string
+}
+
 // table is what the proxy is currently serving, replaced whole whenever the file changes.
 //
 // Replaced rather than merged: the file is the whole truth about who has a route, so merging
 // would keep serving a name whose module was unassigned — which is the stale-route fault
 // 08-connectivity lists as open, reintroduced one level down.
+//
+// Keyed by host to an *ordered* list rather than to one target, because two of the four policies
+// need a single host routed more than one way: a refusal on a path the ordinary route also matches,
+// and a certificate-challenge path on a host that otherwise serves a workload.
 type table struct {
-	mu      sync.RWMutex
+	mu sync.RWMutex
-	to      map[string]*httputil.ReverseProxy
+	to map[string][]rule
-	targets map[string]string
 }
 
-func (t *table) set(routes map[string]string) {
+func (t *table) set(routes map[string][]rule) {
-	made := map[string]*httputil.ReverseProxy{}
+	made := map[string][]rule{}
-	for name, target := range routes {
+	for host, rules := range routes {
-		where, err := url.Parse(target)
+		kept := make([]rule, 0, len(rules))
-		if err != nil {
+		for _, r := range rules {
-			log.Printf("route %s points at %q, which is not a URL: %v", name, target, err)
+			// A rule that only refuses or only redirects has nowhere to send anything, and needs
+			// nowhere: it answers by itself.
+			if r.policy.deny || r.policy.redirectTo != "" {
+				kept = append(kept, r)
+				continue
+			}
+			where, err := url.Parse(r.target)
+			if err != nil {
+				log.Printf("route %s points at %q, which is not a URL: %v", host, r.target, err)
+				continue
+			}
+			r.to = httputil.NewSingleHostReverseProxy(where)
+			kept = append(kept, r)
+		}
+		if len(kept) == 0 {
 			continue
 		}
-		made[name] = httputil.NewSingleHostReverseProxy(where)
+		inOrder(kept)
+		made[host] = kept
 	}
 	t.mu.Lock()
-	t.to, t.targets = made, routes
+	t.to = made
 	t.mu.Unlock()
 }
 
-func (t *table) find(host string) (*httputil.ReverseProxy, bool) {
+// inOrder puts the rules for one host into the order they are matched in, and does so totally.
-	// The port is not part of the name. A request to app.example:8080 is for app.example.
+//
+// **Equal priorities must resolve identically every time** (ADR 0108). Sorting only by priority
+// leaves rules that share one in whatever order the map produced, so the same declaration would
+// serve differently between restarts — a proxy that is not reproducible. Longest path first within a
+// priority is also the intuitive reading: the more specific rule wins. The last two keys exist only
+// to make the order total.
+func inOrder(rules []rule) {
+	sort.SliceStable(rules, func(i, j int) bool {
+		a, b := rules[i], rules[j]
+		if a.priority != b.priority {
+			return a.priority > b.priority
+		}
+		if len(a.path) != len(b.path) {
+			return len(a.path) > len(b.path)
+		}
+		if a.path != b.path {
+			return a.path < b.path
+		}
+		return a.target < b.target
+	})
+}
+
+// find is the rule that answers this request, or nothing if the host is not routed here at all.
+func (t *table) find(host, path string) (rule, bool) {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	for _, r := range t.to[bareHost(host)] {
+		if r.path == "" || strings.HasPrefix(path, r.path) {
+			return r, true
+		}
+	}
+	return rule{}, false
+}
+
+// routed says whether this proxy serves the name at all, whatever the path.
+//
+// Separate from find because certificate issuance is a question about the *name*: a host whose only
+// rules are path-scoped is still a name this proxy answers to, and still needs a certificate.
+func (t *table) routed(host string) bool {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+	return len(t.to[bareHost(host)]) > 0
+}
+
+// bareHost is the name without the port, lower-cased.
+//
+// The port is not part of the name: a request to app.example:8080 is for app.example. Lower-cased
+// because a Host header is not case-sensitive, and a route that only answers the spelling in the
+// manifest answers half the requests made to it.
+func bareHost(host string) string {
 	if h, _, err := net.SplitHostPort(host); err == nil {
 		host = h
 	}
-	t.mu.RLock()
+	return strings.ToLower(host)
-	defer t.mu.RUnlock()
-	p, ok := t.to[strings.ToLower(host)]
-	return p, ok
 }
 
 func (t *table) names() []string {
 	t.mu.RLock()
 	defer t.mu.RUnlock()
-	out := make([]string, 0, len(t.targets))
+	out := make([]string, 0, len(t.to))
-	for name := range t.targets {
+	for name := range t.to {
 		out = append(out, name)
 	}
 	sort.Strings(out)
@@ -285,29 +405,115 @@ func forThisAuthority(cache, directory string, root []byte) string {
 
 // newTable is an empty routing table.
 func newTable() *table {
-	return &table{to: map[string]*httputil.ReverseProxy{}, targets: map[string]string{}}
+	return &table{to: map[string][]rule{}}
 }
 
 // handler is the proxy itself, separated so it can be driven by a test without a listener.
 func handler(held *table) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		proxy, known := held.find(r.Host)
+		matched, known := held.find(r.Host, r.URL.Path)
 		if !known {
 			// **Named, not a bare 404.** A route that was withdrawn and a name that never existed
 			// are different things, and a proxy that says only "not found" makes an operator go
 			// and read the mesh to tell them apart. What it is serving is the answer to both.
+			//
+			// And since a host may now be routed only on some paths, those are a third thing:
+			// saying "no route for this name" while listing that very name as served is a
+			// contradiction an operator would have to disbelieve the proxy to get past.
 			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 			w.WriteHeader(http.StatusNotFound)
+			if held.routed(r.Host) {
+				fmt.Fprintf(w, "%s is served here, but no route covers %q.\n",
+					bareHost(r.Host), r.URL.Path)
+				return
+			}
 			fmt.Fprintf(w, "no route for %q in this mesh.\nserving: %s\n",
 				r.Host, strings.Join(held.names(), ", "))
 			return
 		}
-		proxy.ServeHTTP(w, r)
+
+		switch {
+		case matched.policy.sealed != "":
+			// Declared a gate, cannot check it. Refused, and says why — an operator reading this
+			// learns the secret is missing, rather than wondering why a protected name is 503.
+			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+			w.WriteHeader(http.StatusServiceUnavailable)
+			fmt.Fprintf(w, "this route requires authentication and its credentials cannot be read: %s\n",
+				matched.policy.sealed)
+			return
+
+		case matched.policy.deny:
+			http.Error(w, "this path is not served to you", http.StatusForbidden)
+			return
+
+		case matched.policy.redirectTo != "":
+			http.Redirect(w, r, canonical(matched.policy.redirectTo, r.URL), http.StatusMovedPermanently)
+			return
+
+		case len(matched.policy.users) > 0 && !allowed(matched.policy.users, r):
+			// The realm is the name asked for, so a browser's prompt says which route it is for.
+			w.Header().Set("WWW-Authenticate", fmt.Sprintf("Basic realm=%q, charset=\"UTF-8\"", bareHost(r.Host)))
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+
+		matched.to.ServeHTTP(w, r)
 	})
 }
 
-// routesFrom reads what the mesh wrote and turns it into name → target.
+// canonical is where a redirect sends this request.
-func routesFrom(path string) (map[string]string, error) {
+//
+// The declaration names the destination *name*; the request keeps its own path and query. That is
+// what canonicalising one public name onto another means — a link to a page under the old name has
+// to arrive at the same page under the new one, or the redirect silently loses every deep link.
+func canonical(to string, from *url.URL) string {
+	where, err := url.Parse(to)
+	if err != nil {
+		return to
+	}
+	if where.Path == "" || where.Path == "/" {
+		where.Path = from.Path
+	}
+	if where.RawQuery == "" {
+		where.RawQuery = from.RawQuery
+	}
+	return where.String()
+}
+
+// allowed says whether the request presented credentials this route accepts.
+//
+// **Every path costs one bcrypt comparison**, including an unknown user, which is why the miss
+// compares against a fixed hash rather than returning early. Returning early would make an unknown
+// user measurably faster than a known one with a wrong password, and that difference is a way to
+// enumerate the users of a route from outside it.
+func allowed(users map[string]string, r *http.Request) bool {
+	// A hash of nothing anybody knows. Its only job is to cost what a real comparison costs.
+	const absent = "$2a$10$N9qo8uLOickgx2ZMRZoMyeIjZAgcfl7p92ldGxad68LJZdL17lhWy"
+	user, password, ok := r.BasicAuth()
+	if !ok {
+		return false
+	}
+	want, known := users[user]
+	if !known {
+		want = absent
+	}
+	if err := bcrypt.CompareHashAndPassword([]byte(want), []byte(password)); err != nil {
+		return false
+	}
+	// `known` is checked after the comparison, not instead of it, so the timing is the same either
+	// way. subtle.ConstantTimeByteEq keeps the branch from being the thing that differs.
+	return subtle.ConstantTimeByteEq(boolByte(known), 1) == 1
+}
+
+func boolByte(b bool) byte {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+// routesFrom reads what the mesh wrote and turns it into host → the rules for that host.
+func routesFrom(path string) (map[string][]rule, error) {
 	raw, err := os.ReadFile(path)
 	if err != nil {
 		return nil, err
@@ -317,31 +523,134 @@ func routesFrom(path string) (map[string]string, error) {
 		return nil, err
 	}
 
-	out := map[string]string{}
+	out := map[string][]rule{}
 	for _, c := range said.Given {
 		name, _ := c.Values["name"].(string)
 		if name == "" {
 			log.Printf("%s on %s asked for a route and named nothing; skipped", c.From, c.Node)
 			continue
 		}
-		port, ok := asPort(c.Values["port"])
+		host := strings.ToLower(name)
-		if !ok {
+
-			log.Printf("%s on %s asked for route %q and gave no usable port; skipped",
+		made := rule{path: asPath(c.Values["path"])}
-				c.From, c.Node, name)
+		if p, ok := asWhole(c.Values["priority"]); ok {
-			continue
+			made.priority = p
 		}
-		// Where the mesh says that machine is. Empty means it is this one — a workload beside the
+		made.policy.deny, _ = c.Values["deny"].(bool)
-		// proxy is ordinary, and reaching it over loopback is both correct and the only thing
+		made.policy.redirectTo, _ = c.Values["redirect"].(string)
-		// that works when there is no private network.
+
-		at := c.At
+		if named, carried := c.Values["auth"].(string); carried && strings.TrimSpace(named) != "" {
-		if at == "" {
+			// **A declaration names a secret; it never holds one** (ADR 0108). Refused rather than
-			at = "127.0.0.1"
+			// tolerated, and the whole rule is dropped rather than served unprotected — the
+			// rejected option cannot come back by accident, which is the failure this check exists
+			// to make impossible.
+			if looksLikeACredential(named) {
+				log.Printf("%s on %s declared route %q with a credential in the declaration rather "+
+					"than the name of a secret; the whole route is refused (novox/hq ADR 0108)",
+					c.From, c.Node, name)
+				continue
+			}
+			users, err := usersFrom(named)
+			if err != nil {
+				// Fail closed: the rule is kept so the name stays routed and answers, and it
+				// answers by refusing. Dropping it instead would make the name 404 and read as a
+				// withdrawn route rather than an unreadable secret.
+				made.policy.sealed = err.Error()
+			}
+			made.policy.users = users
 		}
-		out[strings.ToLower(name)] = fmt.Sprintf("http://%s:%d", at, port)
+
+		// Only a rule that actually proxies needs somewhere to send the request.
+		if !made.policy.deny && made.policy.redirectTo == "" {
+			port, ok := asPort(c.Values["port"])
+			if !ok {
+				log.Printf("%s on %s asked for route %q and gave no usable port; skipped",
+					c.From, c.Node, name)
+				continue
+			}
+			// Where the mesh says that machine is. Empty means it is this one — a workload beside
+			// the proxy is ordinary, and reaching it over loopback is both correct and the only
+			// thing that works when there is no private network.
+			at := c.At
+			if at == "" {
+				at = "127.0.0.1"
+			}
+			made.target = fmt.Sprintf("http://%s:%d", at, port)
+		}
+
+		out[host] = append(out[host], made)
 	}
 	return out, nil
 }
 
+// asWhole is any whole number the mesh wrote, whatever its magnitude.
+//
+// **Not asPort.** Priority was read with the port reader first, which caps at 65535 — so a rule
+// declared at a priority 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 bug was
+// exactly load-bearing. A priority is an ordering, not a port: it has no range.
+func asWhole(v any) (int, bool) {
+	switch n := v.(type) {
+	case float64:
+		// JSON makes a float of every number, so a non-integral one was not meant as a priority.
+		if n != float64(int(n)) {
+			return 0, false
+		}
+		return int(n), true
+	case int:
+		return n, true
+	}
+	return 0, false
+}
+
+// asPath is the path prefix a rule is scoped to, or "" for every path.
+func asPath(v any) string {
+	p, _ := v.(string)
+	p = strings.TrimSpace(p)
+	if p == "" {
+		return ""
+	}
+	if !strings.HasPrefix(p, "/") {
+		p = "/" + p
+	}
+	return p
+}
+
+// looksLikeACredential is the check that keeps a secret out of a declaration.
+//
+// It errs towards refusing: a value holding a `:` (the htpasswd separator) or opening with a bcrypt
+// identifier is a credential, not a path, and no filesystem path the mesh writes needs either. A
+// false refusal is a loud log and a route that does not serve; a false accept is a credential
+// committed to a declaration, which is the thing being prevented.
+func looksLikeACredential(v string) bool {
+	v = strings.TrimSpace(v)
+	return strings.Contains(v, ":") || strings.HasPrefix(v, "$2")
+}
+
+// usersFrom reads the credentials the mesh mounted, in the one format every htpasswd already is.
+func usersFrom(path string) (map[string]string, error) {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("cannot read the secret named for this route: %w", err)
+	}
+	users := map[string]string{}
+	for _, line := range strings.Split(string(raw), "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		user, hash, ok := strings.Cut(line, ":")
+		if !ok || user == "" || hash == "" {
+			continue
+		}
+		users[user] = hash
+	}
+	if len(users) == 0 {
+		return nil, fmt.Errorf("the secret named for this route holds no usable credentials")
+	}
+	return users, nil
+}
+
 // asPort accepts what JSON makes of a number, which is a float even when it was written 8080.
 func asPort(v any) (int, bool) {
 	switch n := v.(type) {

examples/route-proxy/policy_test.go

@@ -0,0 +1,273 @@
+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)
+	}
+}

examples/route-proxy/routes_test.go

@@ -19,6 +19,23 @@ func write(t *testing.T, body string) string {
 	return path
 }
 
+// plain is the table an ordinary set of routes makes: one host, one target, no policy.
+func plain(routes map[string]string) map[string][]rule {
+	out := map[string][]rule{}
+	for host, target := range routes {
+		out[host] = []rule{{target: target}}
+	}
+	return out
+}
+
+// targetOf is where a host's first matching rule sends a request.
+func targetOf(routes map[string][]rule, host string) string {
+	if rules := routes[host]; len(rules) > 0 {
+		return rules[0].target
+	}
+	return ""
+}
+
 // A route is a grant: the consumer supplies a target, and where that machine is comes from the
 // mesh rather than from a naming convention the proxy has to know.
 func TestARouteGoesToWhereTheMeshSaysTheConsumerIs(t *testing.T) {
@@ -30,7 +47,7 @@ func TestARouteGoesToWhereTheMeshSaysTheConsumerIs(t *testing.T) {
 	}
 	// Lower-cased, because a Host header is not case-sensitive and a route that only answers the
 	// spelling in the manifest answers half the requests made to it.
-	if routes["app.example"] != "http://laptop.internal:8080" {
+	if targetOf(routes, "app.example") != "http://laptop.internal:8080" {
 		t.Fatalf("the route does not point at the consumer: %v", routes)
 	}
 }
@@ -44,7 +61,7 @@ func TestAConsumerOnTheProxysOwnMachineIsReachedOverLoopback(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if routes["app.example"] != "http://127.0.0.1:9000" {
+	if targetOf(routes, "app.example") != "http://127.0.0.1:9000" {
 		t.Fatalf("a workload on this machine was not reachable: %v", routes)
 	}
 }
@@ -59,7 +76,7 @@ func TestAContributionMissingWhatARouteNeedsIsSkipped(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(routes) != 1 || routes["fine.example"] == "" {
+	if len(routes) != 1 || targetOf(routes, "fine.example") == "" {
 		t.Fatalf("an unusable contribution was served: %v", routes)
 	}
 }
@@ -75,7 +92,7 @@ func TestTheProxyReachesTheWorkloadAndNamesWhatItServes(t *testing.T) {
 	host, port, _ := strings.Cut(target, ":")
 
 	held := newTable()
-	held.set(map[string]string{"app.example": "http://" + host + ":" + port})
+	held.set(plain(map[string]string{"app.example": "http://" + host + ":" + port}))
 
 	proxy := httptest.NewServer(handler(held))
 	defer proxy.Close()
@@ -120,16 +137,16 @@ func TestTheProxyReachesTheWorkloadAndNamesWhatItServes(t *testing.T) {
 // nothing fails more visibly than a stale grant, which is exactly why it must not survive.
 func TestWithdrawingARouteStopsServingIt(t *testing.T) {
 	held := newTable()
-	held.set(map[string]string{
+	held.set(plain(map[string]string{
 		"going.example":   "http://a.internal:80",
 		"staying.example": "http://b.internal:80",
-	})
+	}))
-	held.set(map[string]string{"staying.example": "http://b.internal:80"})
+	held.set(plain(map[string]string{"staying.example": "http://b.internal:80"}))
 
-	if _, still := held.find("going.example"); still {
+	if _, still := held.find("going.example", "/"); still {
 		t.Fatal("a route whose module was unassigned is still served")
 	}
-	if _, kept := held.find("staying.example"); !kept {
+	if _, kept := held.find("staying.example", "/"); !kept {
 		t.Fatal("withdrawing one route took another with it")
 	}
 }
@@ -137,8 +154,8 @@ func TestWithdrawingARouteStopsServingIt(t *testing.T) {
 // A Host header carries a port and the name does not.
 func TestARequestNamingAPortStillFindsItsRoute(t *testing.T) {
 	held := newTable()
-	held.set(map[string]string{"app.example": "http://a.internal:8080"})
+	held.set(plain(map[string]string{"app.example": "http://a.internal:8080"}))
-	if _, found := held.find("app.example:8080"); !found {
+	if _, found := held.find("app.example:8080", "/"); !found {
 		t.Fatal("a request to app.example:8080 did not find the route for app.example")
 	}
 }
@@ -168,7 +185,7 @@ func TestTheIssuerIsStagingUnlessNamed(t *testing.T) {
 // rate limit — and the proxy would look healthy throughout.
 func TestNoCertificateIsAskedForOnAnUnroutedName(t *testing.T) {
 	held := newTable()
-	held.set(map[string]string{"photos.example": "http://127.0.0.1:8080"})
+	held.set(plain(map[string]string{"photos.example": "http://127.0.0.1:8080"}))
 	policy := onlyWhatTheMeshSaid(held)
 
 	if err := policy(context.Background(), "photos.example"); err != nil {
@@ -184,7 +201,7 @@ func TestNoCertificateIsAskedForOnAnUnroutedName(t *testing.T) {
 // A route withdrawn stops being certifiable, without the proxy restarting.
 func TestWithdrawingARouteWithdrawsItsCertificate(t *testing.T) {
 	held := newTable()
-	held.set(map[string]string{"photos.example": "http://127.0.0.1:8080"})
+	held.set(plain(map[string]string{"photos.example": "http://127.0.0.1:8080"}))
 	policy := onlyWhatTheMeshSaid(held)
 	if err := policy(context.Background(), "photos.example"); err != nil {
 		t.Fatal(err)