feat(security): harden gateway boundaries and usage policies

Consolidate subscription usage policy enforcement, privacy-safe persistence, and gateway security hardening into one reviewable change.

Includes bounded HTTP and execution envelopes, header and protocol guards, DNS and relay validation, authentication and secret projection hardening, secure backup/install paths, and regression coverage.

crates/aether-admin/src/provider/state.rs

@@ -8,6 +8,7 @@ use uuid::Uuid;
 
 const KIRO_DEVICE_DEFAULT_START_URL: &str = "https://view.awsapps.com/start";
 const KIRO_DEVICE_DEFAULT_REGION: &str = "us-east-1";
+const MAX_UNVERIFIED_JWT_CLAIMS_BYTES: usize = 64 * 1024;
 
 pub fn current_unix_secs() -> u64 {
     SystemTime::now()
@@ -112,7 +113,18 @@ pub fn json_u64_value(value: Option<&Value>) -> Option<u64> {
 
 pub fn decode_jwt_claims(token: &str) -> Option<Map<String, Value>> {
     let payload = token.split('.').nth(1)?;
+    let max_encoded_len = MAX_UNVERIFIED_JWT_CLAIMS_BYTES
+        .saturating_add(2)
+        .checked_div(3)
+        .unwrap_or(usize::MAX)
+        .saturating_mul(4);
+    if payload.len() > max_encoded_len {
+        return None;
+    }
     let bytes = URL_SAFE_NO_PAD.decode(payload.as_bytes()).ok()?;
+    if bytes.len() > MAX_UNVERIFIED_JWT_CLAIMS_BYTES {
+        return None;
+    }
     serde_json::from_slice::<Value>(&bytes)
         .ok()?
         .as_object()
@@ -398,7 +410,10 @@ pub fn build_kiro_device_key_name(email: Option<&str>, refresh_token: Option<&st
 
 #[cfg(test)]
 mod tests {
-    use super::{enrich_admin_provider_oauth_auth_config, parse_provider_oauth_callback_params};
+    use super::{
+        decode_jwt_claims, enrich_admin_provider_oauth_auth_config,
+        parse_provider_oauth_callback_params, MAX_UNVERIFIED_JWT_CLAIMS_BYTES,
+    };
     use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine as _};
     use serde_json::json;
 
@@ -516,4 +531,16 @@ mod tests {
         assert_eq!(auth_config.get("user_id"), Some(&json!("user-image")));
         assert_eq!(auth_config.get("is_fedramp"), Some(&json!(true)));
     }
+
+    #[test]
+    fn decode_jwt_claims_rejects_oversized_payload_before_decode() {
+        let max_encoded_len = MAX_UNVERIFIED_JWT_CLAIMS_BYTES
+            .saturating_add(2)
+            .checked_div(3)
+            .unwrap()
+            .saturating_mul(4);
+        let token = format!("header.{}.signature", "A".repeat(max_encoded_len + 1));
+
+        assert_eq!(decode_jwt_claims(&token), None);
+    }
 }