Merge quick/0005-bump-close: unibus 0.7.0 + close issue 0005

Hardening 2 (issue 0005, fases 0005a-0005e) cierra los hallazgos nuevos de la
re-auditoría red-team (report 0006): bump de nats-server + toolchain (16 CVEs ->
0 alcanzables), drop de frames sin firma en rooms SignMsgs, limiter global de
bytes en vuelo contra el DoS por concurrencia, TLS obligatorio en bind publico, y
cableado de la ACL por subject que cierra el wildcard metadata leak. Detalle por
fase en el capability growth log del app.md y en el report 0007.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app.md

@@ -2,7 +2,7 @@
 name: unibus
 lang: go
 domain: infra
-version: 0.6.0
+version: 0.7.0
 description: "Bus de mensajería unificado sobre NATS+JetStream con cifrado E2E por room (megolm/olm reducido): service de membresía/claves, librería cliente y peers demo."
 tags: [service, messaging, nats, e2e]
 uses_functions:
@@ -154,6 +154,29 @@ agent.<nombre>.{in,out}   inbox/outbox de agente LLM (agent.scout.in)
 
 ## Capability growth log
 
+- v0.7.0 (2026-06-07) — hardening de seguridad 2 (issue 0005, fases 0005a–0005e)
+  que cierra los hallazgos nuevos de la re-auditoría red-team (report 0006) y
+  lleva el veredicto de exposición pública a "sí-con-condiciones". (0005a) Bump de
+  `github.com/nats-io/nats-server/v2` v2.10.22→v2.11.15 y de la toolchain a
+  go1.26.4: `govulncheck ./...` pasa de 16 vulnerabilidades alcanzables (14 del
+  servidor NATS embebido + 2 de la stdlib) a 0. (0005b) `client.processFrame`
+  ahora descarta cualquier frame sin firma en una room `SignMsgs` (antes verificaba
+  solo si la firma venía presente, lo que permitía suplantar `Sender` con
+  `Sig==nil`). (0005c) Nuevo limiter global de bytes en vuelo
+  (`pkg/membership.inflightLimiter`) que acota la memoria agregada que el control
+  plane bufferiza bajo concurrencia (el límite por-request y el rate-limit por-IP
+  no acotaban el total): un flood concurrente multi-IP se descarta con 503 en vez
+  de crecer sin techo (el RSS deja de escalar con N). (0005d) El guard de arranque
+  `validateBootConfig` ahora exige `--tls-cert/--tls-key` en bind no-loopback (un
+  control plane público sin TLS servía metadata en claro). (0005e) Se cablea por
+  fin en `membershipd` la ACL por subject que ya existía huérfana desde 0003e
+  (`busauth.NewNkeyAuthenticatorACL` + nuevo adaptador `busauth.PermissionsFromSubjects`
+  sobre `membership.SubjectACLFor`): un registrado no-miembro ya no puede
+  `Subscribe(">")` y captar los subjects/advisories de rooms ajenas. Residuales
+  documentados: `$JS.API.>` sigue compartido (cierre completo = NATS accounts por
+  identidad, diferido) y los clientes deben `RefreshSession` tras cambios de
+  membresía (chat/worker aún no lo hacen). El comportamiento de un solo nodo no
+  cambia y master sigue verde.
 - v0.6.0 (2026-06-07) — descentralización / alta disponibilidad (issue 0003,
   fases 0003a–0003e), report 0006. El servidor NATS embebido gana soporte de
   cluster con routes autenticadas (secreto de cluster) y TLS mutuo de nodo

cmd/membershipd/config.go

@@ -43,9 +43,12 @@ func isLoopbackBind(bind string) bool {
 // configuration that would expose the bus without enforced authentication:
 //
 //   - a non-loopback --bind without --bus-auth enforce (the data plane and
-//     control plane would both accept anyone), and
+//     control plane would both accept anyone),
 //   - --tls-cert/--tls-key without --bus-auth enforce (TLS encrypts the channel
-//     but authenticates no one — encrypted access for everybody is still open).
+//     but authenticates no one — encrypted access for everybody is still open), and
+//   - a non-loopback --bind WITHOUT --tls-cert/--tls-key (the control plane would
+//     serve metadata over plaintext HTTP publicly — audit H5 reappearing, the N4
+//     gap the re-audit found: TLS was available but not mandatory).
 //
 // It is a pure function of the parsed flags so the command can fail fast at
 // startup and tests can assert the policy without booting a server.
@@ -60,6 +63,11 @@ func validateBootConfig(bind string, mode membership.AuthMode, tlsCert, tlsKey s
 			"refusing to start: --tls-cert/--tls-key set but --bus-auth is %q; TLS without enforced auth is fail-open (encrypted channel, no authentication) — set --bus-auth enforce",
 			mode)
 	}
+	if !isLoopbackBind(bind) && (tlsCert == "" || tlsKey == "") {
+		return fmt.Errorf(
+			"refusing to start: --bind %q is not loopback but --tls-cert/--tls-key are not both set; a public control plane must serve HTTPS or its metadata (subjects, pubkeys, sealed keys, the social graph) travels in cleartext to a network MITM (audit H5/N4) — provide a CA-signed --tls-cert/--tls-key, or bind 127.0.0.1 for local dev",
+			bind)
+	}
 	return nil
 }
 

cmd/membershipd/config_test.go

@@ -30,6 +30,31 @@ func TestAudit_FailOpenTLSWithoutAuth(t *testing.T) {
 	}
 }
 
+// TestGap_PublicEnforceNoTLS ports the re-auditor's N4 gap: the H2 guard refused
+// "public without enforce" and "TLS without enforce", but ALLOWED a public bind
+// with enforce and NO --tls-cert, so the control plane served metadata over
+// plaintext HTTP publicly (H5 reappearing). The guard now refuses it.
+func TestGap_PublicEnforceNoTLS(t *testing.T) {
+	// The exact auditor configuration: public bind, enforce on, no TLS cert/key.
+	err := validateBootConfig("0.0.0.0", membership.AuthEnforce, "", "")
+	if err == nil {
+		t.Fatalf("public bind + enforce + NO --tls-cert must be refused: the control plane would serve plaintext HTTP publicly (audit N4)")
+	}
+	if !strings.Contains(err.Error(), "tls-cert") {
+		t.Fatalf("error should point the operator at --tls-cert/--tls-key, got: %v", err)
+	}
+
+	// Golden: the same public+enforce config WITH a cert/key is allowed.
+	if err := validateBootConfig("0.0.0.0", membership.AuthEnforce, "server.crt", "server.key"); err != nil {
+		t.Fatalf("public + enforce + TLS is the intended production config, got: %v", err)
+	}
+
+	// Edge: loopback without TLS stays allowed (local dev is not a public exposure).
+	if err := validateBootConfig("127.0.0.1", membership.AuthOff, "", ""); err != nil {
+		t.Fatalf("loopback dev without TLS must remain allowed, got: %v", err)
+	}
+}
+
 // TestBootConfigPolicy is the full table: the golden secure-public config is
 // allowed, dev loopback is allowed, and every fail-open shape is refused.
 func TestBootConfigPolicy(t *testing.T) {
@@ -41,19 +66,25 @@ func TestBootConfigPolicy(t *testing.T) {
 		key     string
 		wantErr bool
 	}{
-		// Golden: the intended public production config.
+		// Golden: the intended public production config — enforce AND TLS.
 		{"public+enforce+tls", "0.0.0.0", membership.AuthEnforce, "s.crt", "s.key", false},
-		{"public+enforce+notls", "0.0.0.0", membership.AuthEnforce, "", "", false},
 		// Edge: local dev on loopback may stay open (no auth, no TLS).
 		{"loopback+off", "127.0.0.1", membership.AuthOff, "", "", false},
 		{"loopback-ipv6+off", "::1", membership.AuthOff, "", "", false},
 		{"localhost+off", "localhost", membership.AuthOff, "", "", false},
 		{"loopback+soft", "127.0.0.1", membership.AuthSoft, "", "", false},
+		// Edge: loopback with full enforce+TLS is also fine.
+		{"loopback+enforce+tls", "127.0.0.1", membership.AuthEnforce, "s.crt", "s.key", false},
 		// Error: public bind without enforce.
 		{"public+off", "0.0.0.0", membership.AuthOff, "", "", true},
 		{"public+soft", "0.0.0.0", membership.AuthSoft, "", "", true},
 		{"lan-ip+off", "192.168.1.10", membership.AuthOff, "", "", true},
 		{"empty-bind+off", "", membership.AuthOff, "", "", true},
+		// Error (N4): public bind + enforce but NO TLS -> plaintext control plane.
+		{"public+enforce+notls", "0.0.0.0", membership.AuthEnforce, "", "", true},
+		{"public+enforce+certonly", "0.0.0.0", membership.AuthEnforce, "s.crt", "", true},
+		{"public+enforce+keyonly", "0.0.0.0", membership.AuthEnforce, "", "s.key", true},
+		{"lan-ip+enforce+notls", "192.168.1.10", membership.AuthEnforce, "", "", true},
 		// Error: TLS flags without enforce (cert or key alone is enough to trip it).
 		{"loopback+tlscert+off", "127.0.0.1", membership.AuthOff, "s.crt", "", true},
 		{"loopback+tlskey+soft", "127.0.0.1", membership.AuthSoft, "", "s.key", true},

cmd/membershipd/main.go

@@ -138,8 +138,18 @@ func main() {
 			log.Printf("cluster: %q node %q, route port %d, %d peer route(s)", *clusterName, *serverName, *clusterPort, len(cc.Routes))
 		}
 		if authMode == membership.AuthEnforce {
-			cfg.Auth = busauth.NewNkeyAuthenticator(store.IsAuthorized)
-			log.Printf("NATS nkey authentication: ON (enforce)")
+			// Per-subject data-plane ACL (audit H4 / N4 residual): the authenticator
+			// authorizes by the bus allowlist AND confines each connection to the
+			// subjects of the rooms it belongs to (plus client-infra subjects). This
+			// closes the wildcard metadata leak where a registered non-member could
+			// Subscribe(">") and harvest every room's subject and JetStream activity.
+			// NATS freezes permissions at connect time, so a peer that joins a room
+			// after connecting must client.RefreshSession to gain that room's subject.
+			cfg.Auth = busauth.NewNkeyAuthenticatorACL(
+				store.IsAuthorized,
+				busauth.PermissionsFromSubjects(membership.SubjectACLFor(store)),
+			)
+			log.Printf("NATS nkey authentication: ON (enforce, per-subject ACL)")
 		}
 		if *tlsCert != "" || *tlsKey != "" {
 			if *tlsCert == "" || *tlsKey == "" {

dev/issues/0005-security-hardening-2.md

@@ -1,8 +1,9 @@
 ---
 issue: 0005
 title: Hardening 2 — CVEs, spoof por firma omitida, DoS por concurrencia, TLS forzado (re-auditoría)
-status: spec
+status: done
 created: 2026-06-07
+completed: 2026-06-07
 domain: security
 scope: unibus (go.mod, pkg/client, pkg/membership/server.go, cmd/membershipd/config.go, pkg/embeddednats, pkg/blobstore)
 depends_on: 0001, 0004 (cierra los hallazgos NUEVOS de la re-auditoría sobre lo entregado)

go.mod

@@ -1,26 +1,28 @@
 module github.com/enmanuel/unibus
 
-go 1.25.0
+go 1.26.4
 
 replace fn-registry => ../../../../
 
 require (
 	fn-registry v0.0.0-00010101000000-000000000000
-	github.com/nats-io/nats-server/v2 v2.10.22
-	github.com/nats-io/nats.go v1.37.0
-	github.com/nats-io/nkeys v0.4.7
+	github.com/nats-io/nats-server/v2 v2.11.15
+	github.com/nats-io/nats.go v1.49.0
+	github.com/nats-io/nkeys v0.4.15
 	github.com/oklog/ulid/v2 v2.1.0
-	golang.org/x/time v0.7.0
+	golang.org/x/time v0.15.0
 	modernc.org/sqlite v1.47.0
 )
 
 require (
+	github.com/antithesishq/antithesis-sdk-go v0.6.0-default-no-op // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
+	github.com/google/go-tpm v0.9.8 // indirect
 	github.com/google/uuid v1.6.0 // indirect
-	github.com/klauspost/compress v1.18.3 // indirect
+	github.com/klauspost/compress v1.18.4 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/minio/highwayhash v1.0.3 // indirect
-	github.com/nats-io/jwt/v2 v2.5.8 // indirect
+	github.com/minio/highwayhash v1.0.4-0.20251030100505-070ab1a87a76 // indirect
+	github.com/nats-io/jwt/v2 v2.8.1 // indirect
 	github.com/nats-io/nuid v1.0.1 // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
@@ -29,7 +31,6 @@ require (
 	golang.org/x/mod v0.36.0 // indirect
 	golang.org/x/sync v0.20.0 // indirect
 	golang.org/x/sys v0.44.0 // indirect
-	golang.org/x/text v0.37.0 // indirect
 	golang.org/x/tools v0.45.0 // indirect
 	modernc.org/libc v1.70.0 // indirect
 	modernc.org/mathutil v1.7.1 // indirect

go.sum

@@ -1,27 +1,31 @@
+github.com/antithesishq/antithesis-sdk-go v0.6.0-default-no-op h1:kpBdlEPbRvff0mDD1gk7o9BhI16b9p5yYAXRlidpqJE=
+github.com/antithesishq/antithesis-sdk-go v0.6.0-default-no-op/go.mod h1:IUpT2DPAKh6i/YhSbt6Gl3v2yvUZjmKncl7U91fup7E=
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
 github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/go-tpm v0.9.8 h1:slArAR9Ft+1ybZu0lBwpSmpwhRXaa85hWtMinMyRAWo=
+github.com/google/go-tpm v0.9.8/go.mod h1:h9jEsEECg7gtLis0upRBQU+GhYVH6jMjrFxI8u6bVUY=
 github.com/google/pprof v0.0.0-20250317173921-a4b03ec1a45e h1:ijClszYn+mADRFY17kjQEVQ1XRhq2/JR1M3sGqeJoxs=
 github.com/google/pprof v0.0.0-20250317173921-a4b03ec1a45e/go.mod h1:boTsfXsheKC2y+lKOCMpSfarhxDeIzfZG1jqGcPl3cA=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/golang-lru/v2 v2.0.7 h1:a+bsQ5rvGLjzHuww6tVxozPZFVghXaHOwFs4luLUK2k=
 github.com/hashicorp/golang-lru/v2 v2.0.7/go.mod h1:QeFd9opnmA6QUJc5vARoKUSoFhyfM2/ZepoAG6RGpeM=
-github.com/klauspost/compress v1.18.3 h1:9PJRvfbmTabkOX8moIpXPbMMbYN60bWImDDU7L+/6zw=
-github.com/klauspost/compress v1.18.3/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
+github.com/klauspost/compress v1.18.4 h1:RPhnKRAQ4Fh8zU2FY/6ZFDwTVTxgJ/EMydqSTzE9a2c=
+github.com/klauspost/compress v1.18.4/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
-github.com/minio/highwayhash v1.0.3 h1:kbnuUMoHYyVl7szWjSxJnxw11k2U709jqFPPmIUyD6Q=
-github.com/minio/highwayhash v1.0.3/go.mod h1:GGYsuwP/fPD6Y9hMiXuapVvlIUEhFhMTh0rxU3ik1LQ=
-github.com/nats-io/jwt/v2 v2.5.8 h1:uvdSzwWiEGWGXf+0Q+70qv6AQdvcvxrv9hPM0RiPamE=
-github.com/nats-io/jwt/v2 v2.5.8/go.mod h1:ZdWS1nZa6WMZfFwwgpEaqBV8EPGVgOTDHN/wTbz0Y5A=
-github.com/nats-io/nats-server/v2 v2.10.22 h1:Yt63BGu2c3DdMoBZNcR6pjGQwk/asrKU7VX846ibxDA=
-github.com/nats-io/nats-server/v2 v2.10.22/go.mod h1:X/m1ye9NYansUXYFrbcDwUi/blHkrgHh2rgCJaakonk=
-github.com/nats-io/nats.go v1.37.0 h1:07rauXbVnnJvv1gfIyghFEo6lUcYRY0WXc3x7x0vUxE=
-github.com/nats-io/nats.go v1.37.0/go.mod h1:Ubdu4Nh9exXdSz0RVWRFBbRfrbSxOYd26oF0wkWclB8=
-github.com/nats-io/nkeys v0.4.7 h1:RwNJbbIdYCoClSDNY7QVKZlyb/wfT6ugvFCiKy6vDvI=
-github.com/nats-io/nkeys v0.4.7/go.mod h1:kqXRgRDPlGy7nGaEDMuYzmiJCIAAWDK0IMBtDmGD0nc=
+github.com/minio/highwayhash v1.0.4-0.20251030100505-070ab1a87a76 h1:KGuD/pM2JpL9FAYvBrnBBeENKZNh6eNtjqytV6TYjnk=
+github.com/minio/highwayhash v1.0.4-0.20251030100505-070ab1a87a76/go.mod h1:GGYsuwP/fPD6Y9hMiXuapVvlIUEhFhMTh0rxU3ik1LQ=
+github.com/nats-io/jwt/v2 v2.8.1 h1:V0xpGuD/N8Mi+fQNDynXohVvp7ZztevW5io8CUWlPmU=
+github.com/nats-io/jwt/v2 v2.8.1/go.mod h1:nWnOEEiVMiKHQpnAy4eXlizVEtSfzacZ1Q43LIRavZg=
+github.com/nats-io/nats-server/v2 v2.11.15 h1:StSf9TINInaZtr4oww2+kXmfwa9SkN//g/LwS19/UJ0=
+github.com/nats-io/nats-server/v2 v2.11.15/go.mod h1:zwhv8Y0PE3KHyKgznJc/9Xoai638SaJd83zzJ5GJn74=
+github.com/nats-io/nats.go v1.49.0 h1:yh/WvY59gXqYpgl33ZI+XoVPKyut/IcEaqtsiuTJpoE=
+github.com/nats-io/nats.go v1.49.0/go.mod h1:fDCn3mN5cY8HooHwE2ukiLb4p4G4ImmzvXyJt+tGwdw=
+github.com/nats-io/nkeys v0.4.15 h1:JACV5jRVO9V856KOapQ7x+EY8Jo3qw1vJt/9Jpwzkk4=
+github.com/nats-io/nkeys v0.4.15/go.mod h1:CpMchTXC9fxA5zrMo4KpySxNjiDVvr8ANOSZdiNfUrs=
 github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
 github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
 github.com/ncruces/go-strftime v1.0.0 h1:HMFp8mLCTPp341M/ZnA4qaf7ZlsbTc+miZjCLOFAw7w=
@@ -43,10 +47,8 @@ golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/sys v0.44.0 h1:ildZl3J4uzeKP07r2F++Op7E9B29JRUy+a27EibtBTQ=
 golang.org/x/sys v0.44.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
-golang.org/x/text v0.37.0 h1:Cqjiwd9eSg8e0QAkyCaQTNHFIIzWtidPahFWR83rTrc=
-golang.org/x/text v0.37.0/go.mod h1:a5sjxXGs9hsn/AJVwuElvCAo9v8QYLzvavO5z2PiM38=
-golang.org/x/time v0.7.0 h1:ntUhktv3OPE6TgYxXWv9vKvUSJyIFJlyohwbkEwPrKQ=
-golang.org/x/time v0.7.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=
+golang.org/x/time v0.15.0 h1:bbrp8t3bGUeFOx08pvsMYRTCVSMk89u4tKbNOZbp88U=
+golang.org/x/time v0.15.0/go.mod h1:Y4YMaQmXwGQZoFaVFk4YpCt4FLQMYKZe9oeV/f4MSno=
 golang.org/x/tools v0.45.0 h1:18qN3FAooORvApf5XjCXgsuayZOEtXf6JK18I3+ONa8=
 golang.org/x/tools v0.45.0/go.mod h1:LuUGqqaXcXMEFEruIVJVm5mgDD8vww/z/SR1gQ4uE/0=
 golang.org/x/tools/go/expect v0.1.1-deprecated h1:jpBZDwmgPhXsKZC6WhL20P4b/wmnpsEAGHaNy0n/rJM=

pkg/busauth/perms.go

@@ -0,0 +1,26 @@
+package busauth
+
+import server "github.com/nats-io/nats-server/v2/server"
+
+// PermissionsFromSubjects adapts a subject-deriving function (e.g.
+// membership.SubjectACLFor, which maps an identity to the subjects of the rooms
+// it belongs to plus the client infrastructure subjects) into the PermissionsFunc
+// the ACL authenticator expects. The derived subjects are granted as BOTH the
+// publish and subscribe allow set, so a connection can only pub/sub on the
+// subjects it is entitled to. A derivation error is propagated so the caller
+// fails closed (denies the connection) rather than granting open access.
+//
+// This is the production wiring for the per-subject data-plane ACL (issue 0003e,
+// audit H4): membershipd passes PermissionsFromSubjects(membership.SubjectACLFor(
+// store)) to NewNkeyAuthenticatorACL. It lives in busauth (not membership) so the
+// membership package stays free of the nats-server dependency.
+func PermissionsFromSubjects(derive func(signPubHex string) ([]string, error)) PermissionsFunc {
+	return func(signPubHex string) (*server.Permissions, error) {
+		subjects, err := derive(signPubHex)
+		if err != nil {
+			return nil, err
+		}
+		sp := &server.SubjectPermission{Allow: subjects}
+		return &server.Permissions{Publish: sp, Subscribe: sp}, nil
+	}
+}

pkg/client/client.go

@@ -799,7 +799,17 @@ func (c *Client) processFrame(roomID string, info roomView, data []byte, handler
 	if err != nil {
 		return
 	}
-	if info.Policy.SignMsgs && f.Sig != nil {
+	// A room with SignMsgs REQUIRES a signature, so an unsigned frame is
+	// unauthenticated and must be dropped — not silently accepted. The previous
+	// `&& f.Sig != nil` guard verified the signature only when one was present, so
+	// an attacker with data-plane access could publish a frame with Sig==nil and a
+	// forged Sender and have the receiver accept it as authentic in a room that
+	// demands signatures (audit N3, report 0006). Requiring the signature first
+	// closes that spoof.
+	if info.Policy.SignMsgs {
+		if f.Sig == nil {
+			return // signature required by room policy but absent: drop
+		}
 		pub, err := c.signerPub(roomID, f.Sender)
 		if err != nil || !cs.VerifyEd25519(pub, f.SigningBytes(), f.Sig) {
 			return // unauthenticated frame: drop

pkg/client/sig_nil_spoof_test.go

@@ -0,0 +1,154 @@
+package client_test
+
+import (
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/enmanuel/unibus/pkg/client"
+	"github.com/enmanuel/unibus/pkg/frame"
+	"github.com/enmanuel/unibus/pkg/room"
+	"github.com/nats-io/nats.go"
+)
+
+// TestReaudit_SigNilSpoof ports the re-auditor's N3 (Alto) finding: in a room
+// that REQUIRES per-message signatures, an attacker with data-plane access
+// publishes a raw frame with Sig==nil and a forged Sender. Before the fix
+// processFrame verified the signature only when one was present
+// (`SignMsgs && f.Sig != nil`), so the receiver accepted the unsigned, forged
+// frame as authentic. The fix drops any unsigned frame in a SignMsgs room.
+//
+// Coverage:
+//   - golden: a properly signed frame from a real member IS delivered;
+//   - error : an unsigned frame with a forged Sender in a SignMsgs room is DROPPED;
+//   - edge  : a room WITHOUT SignMsgs still delivers an unsigned frame (the drop
+//     is specific to signed rooms, not a blanket reject of unsigned frames).
+func TestReaudit_SigNilSpoof(t *testing.T) {
+	h := newHarness(t)
+	waitHealth(t, h.ctrlURL)
+
+	alice, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect alice: %v", err)
+	}
+	defer alice.Close()
+	bob, err := client.New(h.natsURL, h.ctrlURL, mustIdentity(t))
+	if err != nil {
+		t.Fatalf("connect bob: %v", err)
+	}
+	defer bob.Close()
+
+	// A signed-but-NOT-encrypted room: SignMsgs enforces authorship, and the lack
+	// of encryption is exactly the case the auditor flagged as Alto (any peer with
+	// the subject can forge a sender if signatures are not strictly required).
+	const subject = "room.signed.spoof"
+	signedPolicy := room.Policy{Encrypt: false, Persist: false, SignMsgs: true}
+	roomID, err := alice.CreateRoom(subject, signedPolicy)
+	if err != nil {
+		t.Fatalf("alice create signed room: %v", err)
+	}
+	if err := alice.Invite(roomID, bob.Endpoint()); err != nil {
+		t.Fatalf("alice invite bob: %v", err)
+	}
+	if err := bob.Join(roomID); err != nil {
+		t.Fatalf("bob join: %v", err)
+	}
+
+	var mu sync.Mutex
+	var got []string
+	sub, err := bob.Subscribe(roomID, func(_ frame.Frame, plaintext []byte) {
+		mu.Lock()
+		got = append(got, string(plaintext))
+		mu.Unlock()
+	})
+	if err != nil {
+		t.Fatalf("bob subscribe: %v", err)
+	}
+	defer sub.Unsubscribe()
+	time.Sleep(150 * time.Millisecond)
+
+	// Attacker: a raw NATS connection (the dev harness leaves the data plane open),
+	// no identity, forged Sender, NO signature.
+	const spoofMsg = "I am totally the victim"
+	rawAtk, err := nats.Connect(h.natsURL)
+	if err != nil {
+		t.Fatalf("attacker raw connect: %v", err)
+	}
+	defer rawAtk.Close()
+	spoof := frame.Frame{
+		Type:    frame.PUB,
+		Subject: subject,
+		Sender:  "victim-forged-endpoint",
+		MsgID:   "spoof-1",
+		Epoch:   1,
+		Payload: []byte(spoofMsg),
+		// Sig intentionally nil — this is the attack.
+	}
+	sb, err := spoof.Marshal()
+	if err != nil {
+		t.Fatalf("marshal spoof: %v", err)
+	}
+	if err := rawAtk.Publish(subject, sb); err != nil {
+		t.Fatalf("attacker publish: %v", err)
+	}
+	_ = rawAtk.Flush()
+
+	// Golden: alice's properly signed frame must be delivered.
+	const goodMsg = "authentic from alice"
+	if err := alice.Publish(roomID, []byte(goodMsg)); err != nil {
+		t.Fatalf("alice publish: %v", err)
+	}
+	if !waitFor(&mu, &got, func(rs []string) bool {
+		for _, r := range rs {
+			if r == goodMsg {
+				return true
+			}
+		}
+		return false
+	}, 2*time.Second) {
+		t.Fatalf("a properly signed frame should be delivered; got %v", snapshot(&mu, &got))
+	}
+
+	// Error path: the unsigned, forged frame must NEVER reach the handler.
+	for _, r := range snapshot(&mu, &got) {
+		if r == spoofMsg {
+			t.Fatalf("SIG-NIL SPOOF: receiver accepted an unsigned frame with a forged Sender in a SignMsgs room")
+		}
+	}
+
+	// Edge: a room WITHOUT SignMsgs still delivers an unsigned raw frame, proving
+	// the drop is scoped to signed rooms and did not break the plain-NATS path.
+	const subjectOpen = "room.open.nosig"
+	openRoom, err := alice.CreateRoom(subjectOpen, room.ModeNATS)
+	if err != nil {
+		t.Fatalf("alice create open room: %v", err)
+	}
+	openCol := subscribeCollect(t, alice, openRoom)
+	defer openCol.sub.Unsubscribe()
+	time.Sleep(150 * time.Millisecond)
+
+	const openMsg = "unsigned but allowed here"
+	openFrame := frame.Frame{
+		Type:    frame.PUB,
+		Subject: subjectOpen,
+		Sender:  "anyone",
+		MsgID:   "open-1",
+		Payload: []byte(openMsg),
+		// no Sig — fine in a non-signed room
+	}
+	ob, _ := openFrame.Marshal()
+	if err := rawAtk.Publish(subjectOpen, ob); err != nil {
+		t.Fatalf("publish open frame: %v", err)
+	}
+	_ = rawAtk.Flush()
+	if !waitFor(&openCol.mu, &openCol.msgs, func(rs []string) bool {
+		for _, r := range rs {
+			if r == openMsg {
+				return true
+			}
+		}
+		return false
+	}, 2*time.Second) {
+		t.Fatalf("an unsigned frame in a non-signed room should be delivered; got %v", snapshot(&openCol.mu, &openCol.msgs))
+	}
+}

pkg/membership/acl_test.go

@@ -39,18 +39,12 @@ func mustID(t *testing.T) cs.Identity {
 	return id
 }
 
-// aclPermsFunc adapts membership.SubjectACLFor into the busauth.PermissionsFunc
-// the ACL authenticator expects (same Allow set for publish and subscribe).
+// aclPermsFunc builds the per-subject PermissionsFunc the ACL authenticator
+// expects. It delegates to the SAME production wiring membershipd uses
+// (busauth.PermissionsFromSubjects over membership.SubjectACLFor), so this test
+// exercises the real path rather than a test-only reimplementation.
 func aclPermsFunc(store membership.Store) busauth.PermissionsFunc {
-	derive := membership.SubjectACLFor(store)
-	return func(signPubHex string) (*server.Permissions, error) {
-		subs, err := derive(signPubHex)
-		if err != nil {
-			return nil, err
-		}
-		sp := &server.SubjectPermission{Allow: subs}
-		return &server.Permissions{Publish: sp, Subscribe: sp}, nil
-	}
+	return busauth.PermissionsFromSubjects(membership.SubjectACLFor(store))
 }
 
 // startACLNats boots an embedded NATS whose authenticator confines each peer to
@@ -219,6 +213,104 @@ func TestSubjectACLIsolation(t *testing.T) {
 	}
 }
 
+// TestReaudit_H4_WildcardMetadataLeak ports the re-auditor's H4 vector. Before
+// the per-subject ACL was WIRED into membershipd (it existed in pkg/membership and
+// pkg/busauth but the binary used the plain NewNkeyAuthenticator), a registered
+// NON-member could open a raw NATS connection, Subscribe(">"), and capture every
+// room's subject plus JetStream stream/advisory activity — the payload stayed E2E
+// ciphertext, but the metadata leaked. With NewNkeyAuthenticatorACL wired via the
+// production path (busauth.PermissionsFromSubjects(membership.SubjectACLFor)), a
+// non-member is confined to the client-infra subjects, so the wildcard and any
+// foreign room subject are denied.
+//
+// Coverage:
+//   - error : a non-member's Subscribe(">") raises a permission violation;
+//   - edge  : a non-member subscribing to another room's exact subject is denied;
+//   - golden: the member still pub/subs her own room, and the non-member never
+//     captures that traffic.
+//
+// Residual (DOCUMENTED, not closed here): the client-infra grant includes
+// "$JS.API.>", shared by all peers so per-connection JetStream works. A peer that
+// subscribes specifically to "$JS.API.>" can still observe stream-management
+// requests whose subjects embed the stream name derived from a room id. Fully
+// closing that needs NATS accounts/permissions isolation per identity (deferred to
+// the 0003 decentralization line). The high-impact leak the auditor exploited —
+// the room subject itself and JetStream advisories captured via "Subscribe(\">\")"
+// — is closed.
+func TestReaudit_H4_WildcardMetadataLeak(t *testing.T) {
+	dir := t.TempDir()
+	store, err := membership.Open(filepath.Join(dir, "unibus.db"))
+	if err != nil {
+		t.Fatalf("store: %v", err)
+	}
+	t.Cleanup(func() { store.Close() })
+
+	alice, eve := mustID(t), mustID(t)
+	aliceEP := frame.EndpointID(alice.SignPub)
+	mustAddUser(t, store, alice, "alice")
+	mustAddUser(t, store, eve, "eve") // eve is REGISTERED but never a member of alice's room
+	const subject = "room.e2e.confidential"
+	mustCreateRoom(t, store, "ROOMA", subject, aliceEP, alice)
+
+	srv := startACLNats(t, store)
+	url := srv.ClientURL()
+
+	eveErr := make(chan error, 8)
+	eveNC := nkeyConn(t, url, eve, eveErr)
+	eveAll := make(chan *nats.Msg, 16)
+
+	// Error: eve's wildcard subscription is rejected. nats.go creates the local sub
+	// object and the server rejects it asynchronously (delivered to ErrorHandler).
+	if _, err := eveNC.Subscribe(">", func(m *nats.Msg) { eveAll <- m }); err != nil {
+		t.Fatalf("eve sub >: %v", err)
+	}
+	_ = eveNC.Flush()
+	if e := waitErr(eveErr, 1*time.Second); e == nil {
+		t.Fatalf("a non-member's Subscribe(\">\") must raise a permissions violation (wildcard metadata leak still open)")
+	}
+
+	// Edge: eve subscribing to the foreign room's EXACT subject is also denied.
+	drain(eveErr)
+	if _, err := eveNC.Subscribe(subject, func(m *nats.Msg) { eveAll <- m }); err != nil {
+		t.Fatalf("eve sub subject: %v", err)
+	}
+	_ = eveNC.Flush()
+	if e := waitErr(eveErr, 1*time.Second); e == nil {
+		t.Fatalf("a non-member subscribing to another room's subject must be denied")
+	}
+
+	// Golden: alice (the member) pub/subs her own room with no violation, and eve
+	// never captured the traffic despite her (rejected) wildcard.
+	aliceErr := make(chan error, 4)
+	aliceNC := nkeyConn(t, url, alice, aliceErr)
+	aliceGot := make(chan string, 4)
+	if _, err := aliceNC.Subscribe(subject, func(m *nats.Msg) { aliceGot <- string(m.Data) }); err != nil {
+		t.Fatalf("alice sub own room: %v", err)
+	}
+	_ = aliceNC.Flush()
+	if e := waitErr(aliceErr, 300*time.Millisecond); e != nil {
+		t.Fatalf("alice subscribing to her OWN room raised an error: %v", e)
+	}
+	if err := aliceNC.Publish(subject, []byte("members-only metadata")); err != nil {
+		t.Fatalf("alice publish: %v", err)
+	}
+	_ = aliceNC.Flush()
+	select {
+	case got := <-aliceGot:
+		if got != "members-only metadata" {
+			t.Fatalf("alice got %q", got)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatalf("alice did not receive her own room's message")
+	}
+	select {
+	case m := <-eveAll:
+		t.Fatalf("eve captured room traffic despite the ACL: subject=%q data=%q", m.Subject, m.Data)
+	case <-time.After(500 * time.Millisecond):
+		// good: eve captured nothing
+	}
+}
+
 // TestRefreshSessionGainsNewRoom is the "permissions refreshed on join" path:
 // alice is not in room B, so her connection has no permission for its subject;
 // after she is added to room B and calls RefreshSession, the reconnect

pkg/membership/dos_concurrency_test.go

@@ -0,0 +1,148 @@
+package membership
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// readRSSkBRaw reads VmRSS (kB) from /proc without a *testing.T, so it is safe to
+// call from a sampling goroutine (vmRSSkB calls t.Skip, which may only run on the
+// test's own goroutine). Returns 0 when unavailable.
+func readRSSkBRaw() int64 {
+	b, err := os.ReadFile("/proc/self/status")
+	if err != nil {
+		return 0
+	}
+	for _, line := range strings.Split(string(b), "\n") {
+		if strings.HasPrefix(line, "VmRSS:") {
+			f := strings.Fields(line)
+			if len(f) >= 2 {
+				v, _ := strconv.ParseInt(f[1], 10, 64)
+				return v
+			}
+		}
+	}
+	return 0
+}
+
+// TestReaudit_DoSConcurrency ports the re-auditor's N2 (Medio-Alto) finding: the
+// per-request body ceiling and the per-IP rate limit do not bound the AGGREGATE
+// memory of many concurrent uploads. The auditor drove RSS to ~1.42 GB with 40
+// concurrent 16 MiB blob uploads. With the global in-flight byte limiter, the
+// number of simultaneously-buffered uploads is capped, so the resident set stays
+// bounded regardless of how many connections arrive at once.
+//
+// Coverage:
+//   - golden: a normal upload succeeds, and the server is still healthy after the
+//     storm (the limiter did not wedge it);
+//   - edge  : concurrency right at the cap is admitted;
+//   - error : a concurrent flood far past the cap sheds the excess with 503
+//     (backpressure) instead of buffering it all, and the RSS spike stays bounded
+//     and does NOT scale with the number of requests.
+func TestReaudit_DoSConcurrency(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("RSS probe is Linux-only")
+	}
+	srv := dosServer(t, AuthOff)
+	// Force a small aggregate cap so the bound is observable in a unit test: with
+	// a 16 MiB blob ceiling, 48 MiB admits ~3 concurrent uploads. Production uses
+	// maxInflightBytes (128 MiB); the mechanism under test is identical.
+	const cap = int64(48) << 20
+	srv.inflight = newInflightLimiter(cap)
+
+	const blob = maxBlobBytes // 16 MiB, the per-request ceiling
+	const n = 40              // the auditor's figure
+
+	// A spike bound: with the cap admitting ~3 concurrent 16 MiB uploads and a
+	// ~2x copy factor (auth buffer + handler buffer) plus Go runtime slack, the
+	// delta should stay well under this. Without the limiter, 40 concurrent
+	// uploads admitted at once would add hundreds of MB (the auditor saw ~1.4 GB).
+	const maxSpikeKB = int64(256) << 10 // 256 MiB
+
+	runtime.GC()
+	before := readRSSkBRaw()
+
+	// Sample peak RSS while the storm runs.
+	var peak int64
+	atomic.StoreInt64(&peak, before)
+	stop := make(chan struct{})
+	var sampler sync.WaitGroup
+	sampler.Add(1)
+	go func() {
+		defer sampler.Done()
+		for {
+			select {
+			case <-stop:
+				return
+			default:
+				if v := readRSSkBRaw(); v > atomic.LoadInt64(&peak) {
+					atomic.StoreInt64(&peak, v)
+				}
+				time.Sleep(2 * time.Millisecond)
+			}
+		}
+	}()
+
+	var got503, got200 int64
+	var wg sync.WaitGroup
+	for i := 0; i < n; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			req := httptest.NewRequest(http.MethodPost, "/blobs", &zeroReader{remaining: blob})
+			req.ContentLength = blob
+			// Distinct source IP per request: this is the multi-IP (botnet) shape the
+			// auditor flagged, where the per-IP rate limit gives no aggregate defense.
+			// The in-flight byte limiter is the global bound that must hold here.
+			req.RemoteAddr = "198.51.100." + strconv.Itoa(i%254+1) + ":1234"
+			rec := httptest.NewRecorder()
+			srv.ServeHTTP(rec, req)
+			switch rec.Code {
+			case http.StatusServiceUnavailable:
+				atomic.AddInt64(&got503, 1)
+			case http.StatusOK:
+				atomic.AddInt64(&got200, 1)
+			}
+		}()
+	}
+	wg.Wait()
+	close(stop)
+	sampler.Wait()
+
+	runtime.GC()
+	delta := atomic.LoadInt64(&peak) - before
+
+	// Error path: the flood must have hit the cap and shed the excess with 503.
+	if got503 == 0 {
+		t.Fatalf("a concurrent flood of %d uploads past the cap should shed some with 503; got 200=%d 503=%d", n, got200, got503)
+	}
+	// The aggregate memory must stay bounded — not scale with n.
+	if delta > maxSpikeKB {
+		t.Fatalf("aggregate RSS spiked %d kB under %d concurrent uploads (bound %d kB): in-flight limiter not bounding memory", delta, n, maxSpikeKB)
+	}
+	// All reservations released after the storm.
+	if f := srv.inflight.inFlight(); f != 0 {
+		t.Fatalf("after the storm inFlight = %d, want 0 (reservations leaked)", f)
+	}
+
+	// Golden: the server is still healthy and serves a normal upload (from a fresh
+	// IP so the per-IP rate limiter, untouched here, is not what we measure).
+	rec := httptest.NewRecorder()
+	gReq := httptest.NewRequest(http.MethodPost, "/blobs", strings.NewReader("hello after storm"))
+	gReq.RemoteAddr = "203.0.113.9:9999"
+	srv.ServeHTTP(rec, gReq)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("a normal upload after the storm should be 200, got %d (%s)", rec.Code, rec.Body.String())
+	}
+
+	t.Logf("N2 bound: %d uploads -> 200=%d 503=%d, RSS delta %d kB (bound %d kB), cap %d MiB",
+		n, got200, got503, delta, maxSpikeKB, cap>>20)
+}

pkg/membership/inflight.go

@@ -0,0 +1,85 @@
+package membership
+
+import "sync/atomic"
+
+// inflightLimiter is a non-blocking, byte-counting concurrency limiter: a global
+// cap on how many bytes of request body the server will buffer simultaneously.
+//
+// The per-request body ceilings (maxControlBodyBytes / maxBlobBytes) bound a
+// single request, and the per-IP rate limiter throttles a single source, but
+// neither bounds the AGGREGATE memory across many concurrent uploads: the
+// re-audit (report 0006, N2) showed 40 concurrent 16 MiB blob uploads driving
+// RSS to ~1.42 GB, and a distributed (multi-IP) flood scales without a ceiling
+// because the rate limiter is per-IP. This limiter is the missing aggregate
+// bound: ServeHTTP reserves a request's worst-case buffered size before reading
+// the body and releases it when the request finishes, so the total bytes in
+// flight can never exceed max regardless of how many connections or source IPs
+// arrive at once.
+//
+// It is intentionally NON-blocking: when a reservation does not fit, the caller
+// sheds the request with backpressure (503) rather than parking a goroutine,
+// which would let an attacker exhaust goroutines/connections instead of RAM. The
+// counter is maintained with sync/atomic (a CAS loop), so it is safe for
+// concurrent use without a mutex.
+//
+// Implementation note: this lives inside unibus rather than the fn-registry
+// (where a generic concurrency primitive would normally belong) because the
+// registry's functions/core package pulls in transitive dependencies that
+// require CGO (mattn/go-sqlite3) and external modules, which are incompatible
+// with unibus's CGO_ENABLED=0 build, and because this work is scoped to the
+// unibus sub-repo.
+type inflightLimiter struct {
+	max  int64 // immutable after construction; <= 0 disables the limiter
+	used int64 // bytes currently reserved; accessed ONLY via sync/atomic
+}
+
+// newInflightLimiter builds a limiter with a cap of maxBytes bytes in flight.
+// maxBytes <= 0 disables the cap (tryAcquire always grants), which is the
+// loopback/dev posture where an aggregate memory ceiling is not wanted.
+func newInflightLimiter(maxBytes int64) *inflightLimiter {
+	return &inflightLimiter{max: maxBytes}
+}
+
+// tryAcquire reserves n bytes without blocking. It returns true and reserves the
+// bytes when they fit within the cap (used+n <= max), or false (reserving
+// nothing) when they do not. n <= 0 is granted without reserving, and a disabled
+// limiter (max <= 0) always grants. Safe for concurrent use.
+func (l *inflightLimiter) tryAcquire(n int64) bool {
+	if l.max <= 0 || n <= 0 {
+		return true
+	}
+	for {
+		cur := atomic.LoadInt64(&l.used)
+		if cur+n > l.max {
+			return false
+		}
+		if atomic.CompareAndSwapInt64(&l.used, cur, cur+n) {
+			return true
+		}
+	}
+}
+
+// release returns n previously reserved bytes. It must be paired with a
+// tryAcquire that granted. A disabled limiter or n <= 0 is a no-op. The counter
+// never drops below zero (a defensive clamp against an accidental double release).
+func (l *inflightLimiter) release(n int64) {
+	if l.max <= 0 || n <= 0 {
+		return
+	}
+	for {
+		cur := atomic.LoadInt64(&l.used)
+		nv := cur - n
+		if nv < 0 {
+			nv = 0
+		}
+		if atomic.CompareAndSwapInt64(&l.used, cur, nv) {
+			return
+		}
+	}
+}
+
+// inFlight returns the bytes currently reserved. It is observability for tests
+// and metrics.
+func (l *inflightLimiter) inFlight() int64 {
+	return atomic.LoadInt64(&l.used)
+}

pkg/membership/inflight_test.go

@@ -0,0 +1,97 @@
+package membership
+
+import (
+	"sync"
+	"testing"
+)
+
+// TestInflightLimiterBasics covers the limiter contract: granting within the cap
+// (golden), the exact boundary (edge), refusal over the cap without mutating the
+// counter (error), the disabled mode, and the defensive clamp on over-release.
+func TestInflightLimiterBasics(t *testing.T) {
+	l := newInflightLimiter(100)
+
+	// Golden: a reservation within the cap is granted and reflected.
+	if !l.tryAcquire(60) {
+		t.Fatalf("acquire 60 within cap 100 should grant")
+	}
+	if l.inFlight() != 60 {
+		t.Fatalf("inFlight = %d, want 60", l.inFlight())
+	}
+
+	// Edge: exactly reaching the cap (60+40 == 100) is granted.
+	if !l.tryAcquire(40) {
+		t.Fatalf("acquire to the exact cap should grant")
+	}
+	if l.inFlight() != 100 {
+		t.Fatalf("inFlight = %d, want 100", l.inFlight())
+	}
+
+	// Error: one more byte over the full cap is refused, and the counter is left
+	// untouched (a refused reservation reserves nothing).
+	if l.tryAcquire(1) {
+		t.Fatalf("acquire over a full cap must be refused")
+	}
+	if l.inFlight() != 100 {
+		t.Fatalf("a refused acquire must not change inFlight; got %d", l.inFlight())
+	}
+
+	// Release frees capacity again.
+	l.release(100)
+	if l.inFlight() != 0 {
+		t.Fatalf("inFlight after full release = %d, want 0", l.inFlight())
+	}
+
+	// Defensive: an over-release never drives the counter negative.
+	l.release(50)
+	if l.inFlight() != 0 {
+		t.Fatalf("over-release must clamp at 0; got %d", l.inFlight())
+	}
+}
+
+// TestInflightLimiterDisabled verifies that a non-positive cap disables the
+// limiter: every reservation is granted and nothing is tracked (the loopback/dev
+// posture).
+func TestInflightLimiterDisabled(t *testing.T) {
+	for _, max := range []int64{0, -1} {
+		l := newInflightLimiter(max)
+		if !l.tryAcquire(1 << 30) {
+			t.Fatalf("disabled limiter (max=%d) must always grant", max)
+		}
+		if l.inFlight() != 0 {
+			t.Fatalf("disabled limiter must not track usage; got %d", l.inFlight())
+		}
+		l.release(1 << 30) // no-op, must not panic
+	}
+}
+
+// TestInflightLimiterConcurrent hammers the limiter from many goroutines with
+// equal-sized acquire/release pairs and asserts the invariant never breaks: the
+// counter returns to 0 and never exceeds the cap. Run with -race for the memory
+// model guarantee.
+func TestInflightLimiterConcurrent(t *testing.T) {
+	const cap = 1000
+	const chunk = 7
+	l := newInflightLimiter(cap)
+
+	var wg sync.WaitGroup
+	for g := 0; g < 64; g++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for i := 0; i < 2000; i++ {
+				if l.tryAcquire(chunk) {
+					if f := l.inFlight(); f > cap {
+						t.Errorf("inFlight %d exceeded cap %d", f, cap)
+						return
+					}
+					l.release(chunk)
+				}
+			}
+		}()
+	}
+	wg.Wait()
+	if l.inFlight() != 0 {
+		t.Fatalf("after all goroutines, inFlight = %d, want 0", l.inFlight())
+	}
+}

pkg/membership/server.go

@@ -35,6 +35,14 @@ const (
 	// MaxHeaderBytes caps request header size; wired into the http.Server by the
 	// command. Exported so the bound lives next to its body-size siblings.
 	MaxHeaderBytes = 1 << 20 // 1 MiB
+	// maxInflightBytes is the GLOBAL cap on request-body bytes buffered across all
+	// concurrent requests (audit N2). The per-request ceilings above bound one
+	// request; this bounds the sum, so a concurrent (even multi-IP) flood of
+	// max-size uploads cannot drive the resident set without limit. 128 MiB allows
+	// ~8 concurrent 16 MiB blob uploads or ~128 concurrent control requests before
+	// further POSTs are shed with 503 — generous for an interactive bus, bounded
+	// for an attacker.
+	maxInflightBytes = 128 << 20 // 128 MiB
 )
 
 // Per-IP rate-limit defaults for the control plane. Tuned for an interactive
@@ -62,6 +70,7 @@ type Server struct {
 	authMode AuthMode
 	nonces   nonceStore
 	limiter  *ipRateLimiter
+	inflight *inflightLimiter
 
 	// RequireEncryptedRooms, when true, refuses to create cleartext (ModeNATS)
 	// rooms. It is the minimum-defensive control for the data plane (audit H4):
@@ -87,6 +96,7 @@ func NewServer(store Store, blobs blobstore.Store, authMode AuthMode) *Server {
 		authMode: authMode,
 		nonces:   newMemNonceCache(nonceTTL, maxNonceCacheEntries),
 		limiter:  newIPRateLimiter(defaultRatePerSec, defaultRateBurst, rateBucketTTL),
+		inflight: newInflightLimiter(maxInflightBytes),
 	}
 	s.routes()
 	return s
@@ -139,6 +149,22 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 	r.Body = http.MaxBytesReader(w, r.Body, limit)
 
+	// Aggregate memory bound (audit N2): the per-request ceiling above and the
+	// per-IP rate limit do not cap the TOTAL bytes buffered across concurrent
+	// requests. A POST reserves its worst-case buffered size (its route ceiling)
+	// from a global limiter before the body is read, and is shed with 503 when the
+	// cap is reached, so the resident set stays bounded under a concurrent (even
+	// multi-IP) upload flood instead of growing linearly with the number of
+	// connections. Reservation is released when the request finishes. Only POSTs
+	// buffer a body; GETs carry none, so they do not consume the budget.
+	if r.Method == http.MethodPost {
+		if !s.inflight.tryAcquire(limit) {
+			writeErr(w, http.StatusServiceUnavailable, "server busy: too many concurrent uploads in flight")
+			return
+		}
+		defer s.inflight.release(limit)
+	}
+
 	if s.authMode == AuthOff || isAuthExempt(r) {
 		s.mux.ServeHTTP(w, r)
 		return