server: a non-admin account can manage its own uploads

Signing in and being allowed to administer the server were the same
question: the OIDC callback refused a session outright to anyone outside
the admin group. A legitimate user could authenticate, be told what they
could not do, and be left with no way to see or delete the data their own
devices had uploaded.

They are separate questions now. Everyone who authenticates gets a
session; the admin flag rides inside the MAC'd payload, so promoting
yourself means forging a signature rather than editing a cookie, and a
role that does not parse fails closed to "user".

Pages scope themselves through visibleDevices/mayTouchRun rather than
filtering individually — per-page scoping is what the next page added
will be missing, and that failure is silent, since a listing that leaks
other people's uploads looks exactly like one that does not. Someone
else's run answers 404, not 403: a distinguishable refusal would confirm
the run exists. Revoking devices and minting enrolment tokens affect the
whole server and stay behind adminOnly at the route table, where someone
looking for who-may-do-what will actually find it.

Ownership is re-read per request instead of captured at sign-in, so
unlinking an account takes effect immediately rather than at session
expiry. Tests cover that, plus the degenerate case of an empty subject,
which must own nothing rather than everything with an empty account id.

Also: attribute the ICMPv6 finding per network. It compared "is IPv6
configured anywhere on this device" against "did any network answer",
which on a phone reports IPv6-is-broken about a network where IPv6 was
never configured. network_ref is null on every test, so the probe now
records per-network outcomes structurally rather than as prose a finding
would have to parse.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/internal/adminauth/adminauth.go

@@ -166,12 +166,21 @@ func (t *Throttle) Succeeded() {
 
 // ---- sessions ---------------------------------------------------------------------------
 
-// Session is an authenticated admin, however they proved it.
+// Session is an authenticated account, however it proved itself. Not necessarily an admin:
+// signing in and being allowed to administer the server are separate questions, and a plain user
+// gets a session so they can manage their own uploads.
 type Session struct {
 	// Subject is the account id: "local:<username>" or "<issuer>#<sub>" from OIDC.
 	Subject string
 	// Display is what the UI shows.
 	Display string
+	// Admin is authorisation, decided at sign-in and carried inside the signed payload.
+	//
+	// Inside, specifically — not derived later from the subject, and not stored beside the MAC.
+	// A flag outside the signature is a privilege escalation anyone can perform with a text
+	// editor, and re-deriving it per request would mean re-reading group membership from the IdP
+	// on a path that has no token to do it with.
+	Admin   bool
 	Expires time.Time
 }
 
@@ -203,12 +212,16 @@ func NewSecret() ([]byte, error) {
 
 var ErrSession = errors.New("session is not valid")
 
-// Issue returns the cookie value for a newly authenticated admin.
-func (s *Sessions) Issue(subject, display string) string {
+// Issue returns the cookie value for a newly authenticated account.
+func (s *Sessions) Issue(subject, display string, admin bool) string {
 	exp := time.Now().Add(s.ttl).Unix()
+	role := "u"
+	if admin {
+		role = "a"
+	}
 	payload := base64.RawURLEncoding.EncodeToString([]byte(subject)) + "." +
 		base64.RawURLEncoding.EncodeToString([]byte(display)) + "." +
-		strconv.FormatInt(exp, 10)
+		strconv.FormatInt(exp, 10) + "." + role
 	return payload + "." + s.mac(payload)
 }
 
@@ -225,7 +238,7 @@ func (s *Sessions) Parse(value string) (*Session, error) {
 		return nil, ErrSession
 	}
 	parts := strings.Split(payload, ".")
-	if len(parts) != 3 {
+	if len(parts) != 4 {
 		return nil, ErrSession
 	}
 	subject, err := base64.RawURLEncoding.DecodeString(parts[0])
@@ -243,7 +256,13 @@ func (s *Sessions) Parse(value string) (*Session, error) {
 	if time.Now().After(time.Unix(exp, 0)) {
 		return nil, fmt.Errorf("%w: expired", ErrSession)
 	}
-	return &Session{Subject: string(subject), Display: string(display), Expires: time.Unix(exp, 0)}, nil
+	// Anything that is not exactly the admin marker is a user. A malformed role must fail closed:
+	// the safe reading of an unparseable privilege claim is the smaller privilege.
+	admin := parts[3] == "a"
+	return &Session{
+		Subject: string(subject), Display: string(display),
+		Admin: admin, Expires: time.Unix(exp, 0),
+	}, nil
 }
 
 func (s *Sessions) mac(payload string) string {

server/internal/adminauth/adminauth_test.go

@@ -4,6 +4,8 @@
 package adminauth
 
 import (
+	"encoding/base64"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -96,7 +98,7 @@ func TestAnEmptyCredentialNeverVerifies(t *testing.T) {
 func TestSessionRoundTrip(t *testing.T) {
 	secret, _ := NewSecret()
 	s := NewSessions(secret, time.Hour)
-	got, err := s.Parse(s.Issue("local:admin", "Admin"))
+	got, err := s.Parse(s.Issue("local:admin", "Admin", true))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -110,7 +112,7 @@ func TestSessionRoundTrip(t *testing.T) {
 func TestTamperedSessionsAreRejected(t *testing.T) {
 	secret, _ := NewSecret()
 	s := NewSessions(secret, time.Hour)
-	good := s.Issue("local:admin", "Admin")
+	good := s.Issue("local:admin", "Admin", true)
 
 	parts := strings.Split(good, ".")
 	tampered := []string{
@@ -131,7 +133,7 @@ func TestTamperedSessionsAreRejected(t *testing.T) {
 func TestSessionsFromAnotherSecretAreRejected(t *testing.T) {
 	a, _ := NewSecret()
 	b, _ := NewSecret()
-	issued := NewSessions(a, time.Hour).Issue("local:admin", "Admin")
+	issued := NewSessions(a, time.Hour).Issue("local:admin", "Admin", true)
 	if _, err := NewSessions(b, time.Hour).Parse(issued); err == nil {
 		t.Fatal("a session signed with a different secret was accepted — rotating the secret " +
 			"must invalidate every existing session")
@@ -143,7 +145,7 @@ func TestExpiredSessionsAreRejected(t *testing.T) {
 	// A negative TTL is not reachable through NewSessions, so issue with a real one and check
 	// the boundary via a session that has already run out.
 	s := NewSessions(secret, time.Millisecond)
-	v := s.Issue("local:admin", "Admin")
+	v := s.Issue("local:admin", "Admin", true)
 	time.Sleep(10 * time.Millisecond)
 	if _, err := s.Parse(v); err == nil {
 		t.Fatal("an expired session was accepted")
@@ -201,3 +203,46 @@ func TestThrottleForgivesAfterAQuietPeriod(t *testing.T) {
 		t.Fatalf("an operator returning later was still throttled: %v", d)
 	}
 }
+
+// The admin flag is an authorisation decision carried in a cookie the client holds, so the
+// interesting cases are all about what happens when the client lies about it.
+func TestSessionAdminFlag(t *testing.T) {
+	s := NewSessions([]byte("secret"), time.Hour)
+
+	t.Run("round trips both ways", func(t *testing.T) {
+		admin, err := s.Parse(s.Issue("local:admin", "Admin", true))
+		if err != nil || !admin.Admin {
+			t.Fatalf("admin session did not survive: %+v err=%v", admin, err)
+		}
+		user, err := s.Parse(s.Issue("oidc#1", "Markus", false))
+		if err != nil || user.Admin {
+			t.Fatalf("user session came back as admin: %+v err=%v", user, err)
+		}
+	})
+
+	t.Run("promoting yourself invalidates the cookie", func(t *testing.T) {
+		// The whole point of putting the flag inside the MAC: editing it must break the signature
+		// rather than produce a valid admin session.
+		v := s.Issue("oidc#1", "Markus", false)
+		i := strings.LastIndex(v, ".")
+		tampered := strings.TrimSuffix(v[:i], ".u") + ".a" + v[i:]
+		if got, err := s.Parse(tampered); err == nil {
+			t.Fatalf("a self-promoted cookie was accepted as %+v", got)
+		}
+	})
+
+	t.Run("an unparseable role is not an admin", func(t *testing.T) {
+		// Fail closed: whatever a malformed privilege claim means, it does not mean "more access".
+		// Signed by us, so it passes the MAC — only the role parsing stands between it and admin.
+		exp := strconv.FormatInt(time.Now().Add(time.Hour).Unix(), 10)
+		payload := base64.RawURLEncoding.EncodeToString([]byte("oidc#1")) + "." +
+			base64.RawURLEncoding.EncodeToString([]byte("Markus")) + "." + exp + ".ADMIN"
+		sess, err := s.Parse(payload + "." + s.mac(payload))
+		if err != nil {
+			t.Fatalf("unexpected parse error: %v", err)
+		}
+		if sess.Admin {
+			t.Fatal("a role of \"ADMIN\" was treated as the admin marker")
+		}
+	})
+}

server/internal/adminui/auth.go

@@ -83,13 +83,17 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("GET /admin/callback", s.oidcCallback)
 	mux.HandleFunc("POST /logout", s.logout)
 
+	// Any signed-in account. These handlers scope what they show to the session themselves —
+	// an admin sees everything, a user sees their own devices and runs.
 	mux.HandleFunc("GET /", s.guard(s.dashboard))
 	mux.HandleFunc("GET /devices", s.guard(s.devices))
-	mux.HandleFunc("POST /devices/{id}/revoke", s.guard(s.revokeDevice))
-	mux.HandleFunc("POST /enroll-tokens", s.guard(s.mintToken))
 	mux.HandleFunc("GET /runs", s.guard(s.runsList))
 	mux.HandleFunc("GET /runs/{device}/{id}", s.guard(s.runView))
 	mux.HandleFunc("POST /runs/{device}/{id}/delete", s.guard(s.runDelete))
+	// Deleting your own upload is yours to do; revoking a device or minting an enrolment token
+	// affects the whole server, so those stay with the admin.
+	mux.HandleFunc("POST /devices/{id}/revoke", s.guard(s.adminOnly(s.revokeDevice)))
+	mux.HandleFunc("POST /enroll-tokens", s.guard(s.adminOnly(s.mintToken)))
 
 	return mux
 }
@@ -140,10 +144,28 @@ func (s *Server) csrfOK(r *http.Request, sess *adminauth.Session) bool {
 	return r.PostFormValue(csrfField) == s.csrfToken(sess)
 }
 
-func (s *Server) setSession(w http.ResponseWriter, subject, display string) {
+// adminOnly refuses a handler to a signed-in account that is not an administrator.
+//
+// A separate wrapper rather than a check inside each handler: an authorisation rule that has to be
+// remembered in every handler is one that will eventually be forgotten in a new one, and the route
+// table is where someone looks to find out who may do what.
+func (s *Server) adminOnly(
+	h func(http.ResponseWriter, *http.Request, *adminauth.Session),
+) func(http.ResponseWriter, *http.Request, *adminauth.Session) {
+	return func(w http.ResponseWriter, r *http.Request, sess *adminauth.Session) {
+		if !sess.Admin {
+			slog.Info("admin action refused", "account", sess.Subject, "path", r.URL.Path)
+			http.Error(w, "that action needs an administrator account", http.StatusForbidden)
+			return
+		}
+		h(w, r, sess)
+	}
+}
+
+func (s *Server) setSession(w http.ResponseWriter, subject, display string, admin bool) {
 	http.SetCookie(w, &http.Cookie{
 		Name:     sessionCookie,
-		Value:    s.Sessions.Issue(subject, display),
+		Value:    s.Sessions.Issue(subject, display, admin),
 		Path:     "/",
 		HttpOnly: true, // the cookie is a bearer credential; script has no business reading it
 		Secure:   s.Secure,
@@ -186,7 +208,7 @@ func (s *Server) loginSubmit(w http.ResponseWriter, r *http.Request) {
 	}
 	s.Throttle.Succeeded()
 	slog.Info("admin login", "user", user, "method", "local", "from", clientIP(r))
-	s.setSession(w, "local:"+cred.Username, cred.Username)
+	s.setSession(w, "local:"+cred.Username, cred.Username, true)
 	http.Redirect(w, r, "/", http.StatusSeeOther)
 }
 
@@ -271,18 +293,14 @@ func (s *Server) oidcCallback(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "the identity token was not accepted", http.StatusForbidden)
 		return
 	}
-	if !s.OIDC.IsAdmin(claims) {
-		// Named explicitly: "you signed in but you are not an admin" is a different problem from
-		// "your password is wrong", and the group is the thing to go and check.
-		slog.Info("admin access denied: not in group", "account", claims.AccountID(),
-			"want_group", s.OIDC.Config().AdminGroup, "have", claims.Groups)
-		http.Error(w, fmt.Sprintf(
-			"Signed in as %s, but that account is not in the %q group, so it cannot administer "+
-				"this server.", claims.Display(), s.OIDC.Config().AdminGroup), http.StatusForbidden)
-		return
-	}
-	slog.Info("admin login", "account", claims.AccountID(), "method", "oidc", "from", clientIP(r))
-	s.setSession(w, claims.AccountID(), claims.Display())
+	// Authentication and authorisation are answered separately here. Someone who is not in the
+	// admin group has still proved who they are, and their own uploads are their business to
+	// manage — refusing them a session outright, as this used to, left a legitimate account with
+	// no way to see or delete the data it had sent.
+	admin := s.OIDC.IsAdmin(claims)
+	slog.Info("login", "account", claims.AccountID(), "method", "oidc", "admin", admin,
+		"from", clientIP(r))
+	s.setSession(w, claims.AccountID(), claims.Display(), admin)
 	http.Redirect(w, r, "/", http.StatusSeeOther)
 }
 

server/internal/adminui/pages.go

@@ -16,6 +16,46 @@ import (
 	"echo-lot.app/server/internal/store"
 )
 
+// visibleDevices returns the devices a session may see: everything for an administrator, and for
+// anyone else the devices linked to their own account.
+//
+// Every page goes through this rather than filtering for itself. Scoping applied per-page is
+// scoping that will be missing from the next page someone adds, and the failure is silent — a
+// listing that quietly shows other people's uploads looks exactly like one that does not.
+func (s *Server) visibleDevices(sess *adminauth.Session) []store.Device {
+	all := s.Store.Devices()
+	if sess.Admin {
+		return all
+	}
+	owned := make(map[string]bool)
+	for _, id := range s.Store.DeviceIDsForAccount(sess.Subject) {
+		owned[id] = true
+	}
+	out := make([]store.Device, 0, len(owned))
+	for _, d := range all {
+		if owned[d.ID] {
+			out = append(out, d)
+		}
+	}
+	return out
+}
+
+// mayTouchRun reports whether this session may read or delete a given run.
+//
+// Checked against the device list rather than against the run's own metadata, so an unlinked or
+// revoked device stops granting access the moment the link is gone.
+func (s *Server) mayTouchRun(sess *adminauth.Session, device string) bool {
+	if sess.Admin {
+		return true
+	}
+	for _, d := range s.visibleDevices(sess) {
+		if d.ID == device {
+			return true
+		}
+	}
+	return false
+}
+
 func (s *Server) loginForm(w http.ResponseWriter, r *http.Request) {
 	if s.session(r) != nil {
 		http.Redirect(w, r, "/", http.StatusSeeOther)
@@ -29,7 +69,7 @@ func (s *Server) loginForm(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *Server) dashboard(w http.ResponseWriter, r *http.Request, sess *adminauth.Session) {
-	devices := s.Store.Devices()
+	devices := s.visibleDevices(sess)
 	linked := 0
 	for _, d := range devices {
 		if d.LinkedToAccount() {
@@ -37,7 +77,9 @@ func (s *Server) dashboard(w http.ResponseWriter, r *http.Request, sess *adminau
 		}
 	}
 	var selftest any
-	if s.SelfTest != nil {
+	// The self-test describes the server's own health, which is an operator's concern; a user
+	// looking at their uploads has no use for it and no ability to act on it.
+	if s.SelfTest != nil && sess.Admin {
 		selftest = s.SelfTest()
 	}
 	s.render(w, r, "dashboard", map[string]any{
@@ -48,6 +90,7 @@ func (s *Server) dashboard(w http.ResponseWriter, r *http.Request, sess *adminau
 		"Runs":     s.totalRuns(devices),
 		"SelfTest": selftest,
 		"Version":  s.Version,
+		"Admin":    sess.Admin,
 	})
 }
 
@@ -63,7 +106,7 @@ func (s *Server) totalRuns(devices []store.Device) int {
 }
 
 func (s *Server) devices(w http.ResponseWriter, r *http.Request, sess *adminauth.Session) {
-	devices := s.Store.Devices()
+	devices := s.visibleDevices(sess)
 	// Newest first: the device someone is looking for is almost always the one just enrolled.
 	sort.Slice(devices, func(i, j int) bool { return devices[i].Enrolled.After(devices[j].Enrolled) })
 
@@ -81,7 +124,7 @@ func (s *Server) devices(w http.ResponseWriter, r *http.Request, sess *adminauth
 	}
 	s.render(w, r, "devices", map[string]any{
 		"Session": sess, "CSRF": s.csrfToken(sess), "Rows": rows,
-		"Link": r.URL.Query().Get("link"),
+		"Link": r.URL.Query().Get("link"), "Admin": sess.Admin,
 	})
 }
 
@@ -118,7 +161,7 @@ func (s *Server) runsList(w http.ResponseWriter, r *http.Request, sess *adminaut
 		DeviceName string
 	}
 	var rows []row
-	for _, d := range s.Store.Devices() {
+	for _, d := range s.visibleDevices(sess) {
 		if s.Runs == nil {
 			break
 		}
@@ -134,10 +177,18 @@ func (s *Server) runsList(w http.ResponseWriter, r *http.Request, sess *adminaut
 	if len(rows) > 200 {
 		rows = rows[:200] // a page, not the archive; the count is on the dashboard
 	}
-	s.render(w, r, "runs", map[string]any{"Session": sess, "CSRF": s.csrfToken(sess), "Rows": rows})
+	s.render(w, r, "runs", map[string]any{
+		"Session": sess, "CSRF": s.csrfToken(sess), "Rows": rows, "Admin": sess.Admin,
+	})
 }
 
 func (s *Server) runView(w http.ResponseWriter, r *http.Request, sess *adminauth.Session) {
+	// 404 rather than 403 for someone else's run: a distinguishable "you may not see this" tells
+	// an unauthorised caller that the run exists, which is itself something they should not learn.
+	if !s.mayTouchRun(sess, r.PathValue("device")) {
+		http.NotFound(w, r)
+		return
+	}
 	body, err := s.Runs.Get(r.PathValue("device"), r.PathValue("id"))
 	if err != nil {
 		http.NotFound(w, r)
@@ -151,7 +202,7 @@ func (s *Server) runView(w http.ResponseWriter, r *http.Request, sess *adminauth
 		out = body
 	}
 	s.render(w, r, "run", map[string]any{
-		"Session": sess, "CSRF": s.csrfToken(sess),
+		"Session": sess, "CSRF": s.csrfToken(sess), "Admin": sess.Admin,
 		"Device": r.PathValue("device"), "ID": r.PathValue("id"),
 		"JSON": string(out),
 	})
@@ -159,6 +210,10 @@ func (s *Server) runView(w http.ResponseWriter, r *http.Request, sess *adminauth
 
 func (s *Server) runDelete(w http.ResponseWriter, r *http.Request, sess *adminauth.Session) {
 	device, id := r.PathValue("device"), r.PathValue("id")
+	if !s.mayTouchRun(sess, device) {
+		http.NotFound(w, r)
+		return
+	}
 	if err := s.Runs.Delete(device, id); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return

server/internal/adminui/render.go

@@ -67,7 +67,7 @@ const baseHTML = `<!doctype html>
 <header>
   <h1>Echolot</h1>
   <nav><a href="/">Overview</a><a href="/devices">Devices</a><a href="/runs">Runs</a></nav>
-  <span class="who">{{.Session.Display}}
+  <span class="who">{{.Session.Display}}{{if not .Session.Admin}} <span class="muted">(your account)</span>{{end}}
     <form method="post" action="/logout" class="inline"><button class="plain">Sign out</button></form>
   </span>
 </header>
@@ -94,18 +94,28 @@ const baseHTML = `<!doctype html>
 
 {{else if eq .Page "dashboard"}}
   <div class="grid">
-    <div class="stat"><b>{{.Devices}}</b><span>devices</span></div>
-    <div class="stat"><b>{{.Linked}}</b><span>signed in</span></div>
-    <div class="stat"><b>{{.Runs}}</b><span>stored runs</span></div>
+    <div class="stat"><b>{{.Devices}}</b><span>{{if .Admin}}devices{{else}}your devices{{end}}</span></div>
+    {{if .Admin}}<div class="stat"><b>{{.Linked}}</b><span>signed in</span></div>{{end}}
+    <div class="stat"><b>{{.Runs}}</b><span>{{if .Admin}}stored runs{{else}}your runs{{end}}</span></div>
   </div>
+  {{if not .Admin}}
+  <div class="card">
+    <p>This is your account. You can see the devices you have signed in on, review everything
+      they have uploaded, and delete any of it.</p>
+    <p class="muted">Administering the server &mdash; enrolling devices, revoking them, and
+      seeing other people's uploads &mdash; needs an administrator account.</p>
+  </div>
+  {{end}}
+  {{if .Admin}}
   <div class="card">
     <h3>Server</h3>
     <p class="muted">version {{.Version}}</p>
     {{with .SelfTest}}<pre>{{printf "%+v" .}}</pre>{{end}}
   </div>
+  {{end}}
 
 {{else if eq .Page "devices"}}
-  <h2>Devices</h2>
+  <h2>{{if .Admin}}Devices{{else}}Your devices{{end}}</h2>
   {{with .Link}}
   <div class="card">
     <p><b>Enrolment link</b> &mdash; single use, valid 24 hours. Treat it like a password until spent.</p>
@@ -114,10 +124,12 @@ const baseHTML = `<!doctype html>
       <code>adb shell am start -a android.intent.action.VIEW -d "{{.}}"</code></p>
   </div>
   {{end}}
+  {{if .Admin}}
   <form method="post" action="/enroll-tokens">
     <input type="hidden" name="csrf" value="{{.CSRF}}">
     <button>Create enrolment link</button>
   </form>
+  {{end}}
   <table>
     <tr><th>Device</th><th>Name</th><th>Account</th><th>Enrolled</th><th>Runs</th><th></th></tr>
     {{range .Rows}}
@@ -127,17 +139,17 @@ const baseHTML = `<!doctype html>
       <td>{{if .LinkedToAccount}}{{.AccountName}}{{else}}<span class="muted">not signed in</span>{{end}}</td>
       <td>{{.Enrolled.Format "2006-01-02 15:04"}}</td>
       <td>{{.Runs}}</td>
-      <td><form method="post" action="/devices/{{.ID}}/revoke" class="inline">
+      <td>{{if $.Admin}}<form method="post" action="/devices/{{.ID}}/revoke" class="inline">
         <input type="hidden" name="csrf" value="{{$.CSRF}}">
-        <button class="danger">Revoke</button></form></td>
+        <button class="danger">Revoke</button></form>{{end}}</td>
     </tr>
     {{else}}
-    <tr><td colspan="6" class="muted">No devices enrolled.</td></tr>
+    <tr><td colspan="6" class="muted">{{if $.Admin}}No devices enrolled.{{else}}You have not signed in on any device yet. Sign in from the Echolot app to link one.{{end}}</td></tr>
     {{end}}
   </table>
 
 {{else if eq .Page "runs"}}
-  <h2>Uploaded runs</h2>
+  <h2>{{if .Admin}}Uploaded runs{{else}}Your uploaded runs{{end}}</h2>
   <p class="muted">Shown exactly as uploaded, at the privacy level the uploader chose. Nothing
     here can un-redact a run.</p>
   <table>

server/internal/adminui/scope_test.go

@@ -0,0 +1,119 @@
+// SPDX-FileCopyrightText: 2026 Echolot contributors
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package adminui
+
+import (
+	"testing"
+	"time"
+
+	"echo-lot.app/server/internal/adminauth"
+	"echo-lot.app/server/internal/runs"
+	"echo-lot.app/server/internal/store"
+)
+
+// Two accounts, one device each, plus an unlinked device nobody owns.
+func fixture(t *testing.T) (*Server, string, string, string) {
+	t.Helper()
+	dir := t.TempDir()
+	st, err := store.Open(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rs, err := runs.Open(dir, runs.DefaultPolicy())
+	if err != nil {
+		t.Fatal(err)
+	}
+	enroll := func(name string) string {
+		tok, err := st.NewEnrollToken(time.Hour, "test")
+		if err != nil {
+			t.Fatal(err)
+		}
+		d, err := st.Redeem(tok, name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return d.ID
+	}
+	mine, theirs, orphan := enroll("mine"), enroll("theirs"), enroll("orphan")
+	if err := st.LinkAccount(mine, "oidc#me", "Me"); err != nil {
+		t.Fatal(err)
+	}
+	if err := st.LinkAccount(theirs, "oidc#you", "You"); err != nil {
+		t.Fatal(err)
+	}
+	for _, d := range []string{mine, theirs, orphan} {
+		if _, err := rs.Put(d, []byte(`{"run":{"id":"r"}}`), true); err != nil {
+			t.Fatal(err)
+		}
+	}
+	return &Server{Store: st, Runs: rs}, mine, theirs, orphan
+}
+
+func user() *adminauth.Session  { return &adminauth.Session{Subject: "oidc#me", Display: "Me"} }
+func admin() *adminauth.Session { return &adminauth.Session{Subject: "local:a", Admin: true} }
+
+func TestVisibleDevicesScopesToAccount(t *testing.T) {
+	s, mine, theirs, orphan := fixture(t)
+
+	got := s.visibleDevices(user())
+	if len(got) != 1 || got[0].ID != mine {
+		t.Fatalf("a user should see only their own device, got %+v", got)
+	}
+
+	all := s.visibleDevices(admin())
+	if len(all) != 3 {
+		t.Fatalf("an admin should see every device, got %d", len(all))
+	}
+	_ = theirs
+	_ = orphan
+}
+
+func TestUnlinkedDevicesBelongToNobody(t *testing.T) {
+	// An enrolled but never-signed-in device is not "everyone's" — a user must not inherit it
+	// just because no account claimed it.
+	s, _, _, orphan := fixture(t)
+	if s.mayTouchRun(user(), orphan) {
+		t.Fatal("an unlinked device was treated as the user's own")
+	}
+}
+
+func TestRunAccessFollowsDeviceOwnership(t *testing.T) {
+	s, mine, theirs, _ := fixture(t)
+
+	if !s.mayTouchRun(user(), mine) {
+		t.Fatal("a user cannot reach their own run")
+	}
+	if s.mayTouchRun(user(), theirs) {
+		t.Fatal("a user reached someone else's run")
+	}
+	if !s.mayTouchRun(admin(), theirs) {
+		t.Fatal("an admin should reach any run")
+	}
+}
+
+func TestAccessEndsWhenTheLinkDoes(t *testing.T) {
+	// Ownership is read from the device list on every request rather than captured at sign-in,
+	// so unlinking takes effect immediately — a session issued while linked must not keep working.
+	s, mine, _, _ := fixture(t)
+	sess := user()
+	if !s.mayTouchRun(sess, mine) {
+		t.Fatal("precondition: the device should start out owned")
+	}
+	if err := s.Store.LinkAccount(mine, "", ""); err != nil {
+		t.Fatal(err)
+	}
+	if s.mayTouchRun(sess, mine) {
+		t.Fatal("access survived the account link being removed")
+	}
+}
+
+func TestEmptySubjectMatchesNothing(t *testing.T) {
+	// The dangerous degenerate case: a session with no subject must own nothing, not everything
+	// that happens to have an empty account id.
+	s, _, _, _ := fixture(t)
+	anon := &adminauth.Session{Subject: "", Display: ""}
+	if got := s.visibleDevices(anon); len(got) != 0 {
+		t.Fatalf("an empty subject matched %d devices", len(got))
+	}
+}