fix(gateway): harden client identity and bound key stores

src/config/schema.rs

@@ -479,9 +479,22 @@ pub struct GatewayConfig {
     #[serde(default = "default_webhook_rate_limit")]
     pub webhook_rate_limit_per_minute: u32,
 
+    /// Trust proxy-forwarded client IP headers (`X-Forwarded-For`, `X-Real-IP`).
+    /// Disabled by default; enable only behind a trusted reverse proxy.
+    #[serde(default)]
+    pub trust_forwarded_headers: bool,
+
+    /// Maximum distinct client keys tracked by gateway rate limiter maps.
+    #[serde(default = "default_gateway_rate_limit_max_keys")]
+    pub rate_limit_max_keys: usize,
+
     /// TTL for webhook idempotency keys.
     #[serde(default = "default_idempotency_ttl_secs")]
     pub idempotency_ttl_secs: u64,
+
+    /// Maximum distinct idempotency keys retained in memory.
+    #[serde(default = "default_gateway_idempotency_max_keys")]
+    pub idempotency_max_keys: usize,
 }
 
 fn default_gateway_port() -> u16 {
@@ -504,6 +517,14 @@ fn default_idempotency_ttl_secs() -> u64 {
     300
 }
 
+fn default_gateway_rate_limit_max_keys() -> usize {
+    10_000
+}
+
+fn default_gateway_idempotency_max_keys() -> usize {
+    10_000
+}
+
 fn default_true() -> bool {
     true
 }
@@ -518,7 +539,10 @@ impl Default for GatewayConfig {
             paired_tokens: Vec::new(),
             pair_rate_limit_per_minute: default_pair_rate_limit(),
             webhook_rate_limit_per_minute: default_webhook_rate_limit(),
+            trust_forwarded_headers: false,
+            rate_limit_max_keys: default_gateway_rate_limit_max_keys(),
             idempotency_ttl_secs: default_idempotency_ttl_secs(),
+            idempotency_max_keys: default_gateway_idempotency_max_keys(),
         }
     }
 }
@@ -2946,7 +2970,10 @@ channel_id = "C123"
         );
         assert_eq!(g.pair_rate_limit_per_minute, 10);
         assert_eq!(g.webhook_rate_limit_per_minute, 60);
+        assert!(!g.trust_forwarded_headers);
+        assert_eq!(g.rate_limit_max_keys, 10_000);
         assert_eq!(g.idempotency_ttl_secs, 300);
+        assert_eq!(g.idempotency_max_keys, 10_000);
     }
 
     #[test]
@@ -2974,7 +3001,10 @@ channel_id = "C123"
             paired_tokens: vec!["zc_test_token".into()],
             pair_rate_limit_per_minute: 12,
             webhook_rate_limit_per_minute: 80,
+            trust_forwarded_headers: true,
+            rate_limit_max_keys: 2048,
             idempotency_ttl_secs: 600,
+            idempotency_max_keys: 4096,
         };
         let toml_str = toml::to_string(&g).unwrap();
         let parsed: GatewayConfig = toml::from_str(&toml_str).unwrap();
@@ -2983,7 +3013,10 @@ channel_id = "C123"
         assert_eq!(parsed.paired_tokens, vec!["zc_test_token"]);
         assert_eq!(parsed.pair_rate_limit_per_minute, 12);
         assert_eq!(parsed.webhook_rate_limit_per_minute, 80);
+        assert!(parsed.trust_forwarded_headers);
+        assert_eq!(parsed.rate_limit_max_keys, 2048);
         assert_eq!(parsed.idempotency_ttl_secs, 600);
+        assert_eq!(parsed.idempotency_max_keys, 4096);
     }
 
     #[test]
@@ -3622,6 +3655,9 @@ default_model = "legacy-model"
         assert!(g.require_pairing);
         assert!(!g.allow_public_bind);
         assert!(g.paired_tokens.is_empty());
+        assert!(!g.trust_forwarded_headers);
+        assert_eq!(g.rate_limit_max_keys, 10_000);
+        assert_eq!(g.idempotency_max_keys, 10_000);
     }
 
     // ── Peripherals config ───────────────────────────────────────