feat: sign reconnect authorisations

server/domain/reconnect_test.go

@@ -1,6 +1,8 @@
 package domain
 
 import (
+	"crypto/hmac"
+	"crypto/sha256"
 	"errors"
 	"testing"
 	"time"
@@ -92,3 +94,42 @@ func TestRankedAbandonCooldownUsesRollingSevenDayLadder(t *testing.T) {
 		t.Fatalf("abandonment repeated: %+v", again)
 	}
 }
+
+func TestSignedJoinAuthorisationBindsEveryClaimBeforeReclaim(t *testing.T) {
+	now := time.Unix(1000, 0).UTC()
+	r, err := NewRankedConnections("match-1", "server-1", "v1", testRoster(now))
+	if err != nil {
+		t.Fatal(err)
+	}
+	key := []byte("test-signing-key")
+	sign := func(payload []byte) ([]byte, error) {
+		mac := hmac.New(sha256.New, key)
+		_, _ = mac.Write(payload)
+		return mac.Sum(nil), nil
+	}
+	verify := func(payload, signature []byte) bool {
+		expected, _ := sign(payload)
+		return hmac.Equal(expected, signature)
+	}
+	signed, err := SignJoinAuthorisation(testRoster(now)[0], sign)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if gen, err := r.AdmitSigned(signed, verify, now); err != nil || gen != 1 {
+		t.Fatalf("signed initial admit = %d, %v", gen, err)
+	}
+	if err := r.Disconnect("a", 1, now); err != nil {
+		t.Fatal(err)
+	}
+	tampered := signed
+	tampered.Authorisation.Slot = 1
+	if _, err := r.AdmitSigned(tampered, verify, now.Add(time.Second)); !errors.Is(err, ErrJoinAuthorisation) {
+		t.Fatalf("tampered slot accepted: %v", err)
+	}
+	if _, err := r.AdmitSigned(signed, func([]byte, []byte) bool { return false }, now.Add(RankedReconnectGrace)); !errors.Is(err, ErrJoinAuthorisation) {
+		t.Fatalf("unverified signature accepted: %v", err)
+	}
+	if gen, err := r.AdmitSigned(signed, verify, now.Add(RankedReconnectGrace)); err != nil || gen != 2 {
+		t.Fatalf("signed reclaim = %d, %v", gen, err)
+	}
+}