feat: add bounded control plane rate limiting

multiplayer-todo.md

@@ -1184,7 +1184,7 @@ the local/CI/community transport, not a silent production fallback.
 | 8.9 `[D:8.4,8.7]` | **IN PROGRESS.** Pure Go join policy binds SteamID/player/match/server/team/slot/protocol/expiry, rejects duplicate roster slots, permits same-identity reclaim through backend loss and fences prior server-owned generations | `server/domain/reconnect.go` covers SteamID/server/slot binding, expiry, repeated reclaim, grace boundary and old-generation fencing; signed token issuance/verification, persistent leases, Godot `hello` transport and production integration remain |
 | 8.10 `[D:8.5,8.31]` | **IN PROGRESS.** Dependency-free workload credential policy validates an adapter-verified signature, issuer/audience/time bounds, namespace/service account, pod UID, GameServer UID, allocation ID, match ID and server ID before result submission | `server/domain/workload.go` and adversarial tests reject every binding mutation, missing/unverified signature and time boundary; `server/testkit/pipeline_test.go` carries allocation identity through the offline result path; projected-token/JWT adapter, trusted-cluster verification and live duplicate/conflict alerting remain |
 | 8.11 `[D:8.1]` | **DONE.** Write the threat model: forged clients/replay/queues/results, floods/bots, pod/insider compromise, gameplay and API DDoS, SDR signing-key theft, dependencies and denial-of-wallet | [`docs/THREAT-MODEL.md`](docs/THREAT-MODEL.md) records prevention, detection/response, owner and residual risk for every threat; it separates offline CA/online signer, client/game-server/PostgreSQL/Redis trust boundaries and recovery behavior |
-| 8.12 `[D:8.11]` | **IN PROGRESS.** Provider-neutral Kubernetes baseline enforces restricted namespace admission, non-root/read-only/no-capability workloads, separate service accounts, allocator-only RBAC, default-deny networking and explicit edge/data/DNS/Agones flows; application manifests consume externally populated Secret objects | `deploy/k8s/base/` plus `server/security/test_kubernetes_policies.py` cover the static hardening and secret-reference invariants; private-store provisioning, edge DDoS/WAF/origin shielding, WebSocket limits, overload shedding, encrypted backups and live policy/load tests remain |
+| 8.12 `[D:8.11]` | **IN PROGRESS.** Provider-neutral Kubernetes baseline enforces restricted namespace admission, non-root/read-only/no-capability workloads, separate service accounts, allocator-only RBAC, default-deny networking and explicit edge/data/DNS/Agones flows; application manifests consume externally populated Secret objects; the Go API now has an optional bounded per-replica rate-limit/429 boundary | `deploy/k8s/base/` plus `server/security/test_kubernetes_policies.py`, `server/api/rate_limit.go` and adversarial tests cover static hardening, secret-reference invariants, fixed-window limits and bounded key memory; private-store provisioning, distributed/global quotas, edge DDoS/WAF/origin shielding, WebSocket limits, overload shedding, encrypted backups and live policy/load tests remain |
 | 8.13 `[D:8.12]` | **IN PROGRESS.** Docker/Kubernetes references are digest-pinned, a dependency-free checker rejects mutable tags/plaintext credentials and concrete release overlays can reject template digests; release documentation defines SBOM, dependency/image scanning, signing, admission verification and a 24-hour critical-fix SLA | `scripts/verify_supply_chain.py`, `server/security/test_supply_chain.py`, `docs/SUPPLY-CHAIN.md` and `.github/workflows/supply-chain.yml` cover repository policy and provenance requirements; registry SBOM/scan/sign/admission execution and a concrete production overlay remain |
 
 #### 8C — Queueing, matchmaking, playlists and rating

server/api/rate_limit.go

@@ -0,0 +1,81 @@
+package api
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+// RateLimiter is an optional fixed-window limiter for the control-plane edge.
+// It is intentionally process-local: a deployment must use a shared edge
+// limiter for global quotas, while this boundary still protects each replica.
+type RateLimiter struct {
+	mu      sync.Mutex
+	limit   int
+	window  time.Duration
+	maxKeys int
+	entries map[string]rateWindow
+}
+
+type rateWindow struct {
+	started time.Time
+	count   int
+}
+
+func NewRateLimiter(limit int, window time.Duration, maxKeys int) (*RateLimiter, error) {
+	if limit < 1 || window <= 0 || maxKeys < 1 {
+		return nil, fmt.Errorf("invalid rate limiter configuration")
+	}
+	return &RateLimiter{limit: limit, window: window, maxKeys: maxKeys, entries: make(map[string]rateWindow)}, nil
+}
+
+func (l *RateLimiter) Allow(key string, now time.Time) bool {
+	if l == nil || key == "" || now.IsZero() {
+		return false
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	for storedKey, entry := range l.entries {
+		if !now.Before(entry.started.Add(l.window)) {
+			delete(l.entries, storedKey)
+		}
+	}
+	entry, exists := l.entries[key]
+	if !exists {
+		if len(l.entries) >= l.maxKeys {
+			return false
+		}
+		l.entries[key] = rateWindow{started: now, count: 1}
+		return true
+	}
+	if !now.Before(entry.started.Add(l.window)) {
+		l.entries[key] = rateWindow{started: now, count: 1}
+		return true
+	}
+	if entry.count >= l.limit {
+		return false
+	}
+	entry.count++
+	l.entries[key] = entry
+	return true
+}
+
+func requestRateKey(r *http.Request) string {
+	if authorization := strings.TrimSpace(r.Header.Get("Authorization")); authorization != "" {
+		digest := sha256.Sum256([]byte(authorization))
+		return "auth:" + hex.EncodeToString(digest[:])
+	}
+	host := r.RemoteAddr
+	if parsedHost, _, err := net.SplitHostPort(host); err == nil {
+		host = parsedHost
+	}
+	if host == "" {
+		return ""
+	}
+	return "ip:" + host
+}

server/api/rate_limit_test.go

@@ -0,0 +1,62 @@
+package api
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestRateLimiterEnforcesWindowAndBoundsKeyMemory(t *testing.T) {
+	limiter, err := NewRateLimiter(2, time.Second, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	start := time.Unix(1000, 0)
+	if !limiter.Allow("player-1", start) || !limiter.Allow("player-1", start.Add(100*time.Millisecond)) {
+		t.Fatal("allowed requests were rejected")
+	}
+	if limiter.Allow("player-1", start.Add(200*time.Millisecond)) {
+		t.Fatal("request over the window limit was accepted")
+	}
+	if limiter.Allow("player-2", start.Add(300*time.Millisecond)) {
+		t.Fatal("unbounded new key bypassed the memory bound")
+	}
+	if !limiter.Allow("player-1", start.Add(time.Second)) {
+		t.Fatal("window did not reset at the boundary")
+	}
+}
+
+func TestRateLimitedHTTPBoundaryReturnsGeneric429(t *testing.T) {
+	limiter, err := NewRateLimiter(1, time.Minute, 8)
+	if err != nil {
+		t.Fatal(err)
+	}
+	service := &Service{RateLimiter: limiter, Now: func() time.Time { return time.Unix(1000, 0) }}
+	server := httptest.NewServer(service.Handler())
+	defer server.Close()
+	request, err := http.NewRequest(http.MethodGet, server.URL+"/healthz", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	request.Header.Set("Authorization", "Bearer secret-session:secret-token")
+	response, err := server.Client().Do(request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_ = response.Body.Close()
+	if response.StatusCode != http.StatusOK {
+		t.Fatalf("first request status = %d", response.StatusCode)
+	}
+	request, _ = http.NewRequest(http.MethodGet, server.URL+"/healthz", strings.NewReader(""))
+	request.Header.Set("Authorization", "Bearer secret-session:secret-token")
+	response, err = server.Client().Do(request)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_ = response.Body.Close()
+	if response.StatusCode != http.StatusTooManyRequests {
+		t.Fatalf("limited request status = %d", response.StatusCode)
+	}
+}

server/api/service.go

@@ -71,6 +71,7 @@ type Service struct {
 	Proposals      map[string]*domain.Proposal
 	RankedProfiles map[string]domain.RankedProfile
 	TierPolicy     domain.TierPolicy
+	RateLimiter    *RateLimiter
 	proposalMu     sync.Mutex
 	eventsMu       sync.Mutex
 	events         *eventHub
@@ -96,7 +97,16 @@ func (s *Service) Handler() http.Handler {
 	mux.HandleFunc("/api/v1/proposals/", s.contractProposalMutation)
 	mux.HandleFunc("/api/v1/assignments/", s.contractAssignment)
 	mux.HandleFunc("/api/v1/events", s.controlPlaneEvent)
-	return mux
+	if s.RateLimiter == nil {
+		return mux
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !s.RateLimiter.Allow(requestRateKey(r), s.now()) {
+			writeError(w, http.StatusTooManyRequests, "rate_limited")
+			return
+		}
+		mux.ServeHTTP(w, r)
+	})
 }
 
 type steamSessionRequest struct {