chore: encrypt tenant NWC URL at rest and stop secret exposure in tenant APIs

backend/.env.template

@@ -28,5 +28,6 @@ LIVEKIT_API_SECRET=
 
 # Billing
 NWC_URL=                      # Nostr Wallet Connect URL for generating Lightning invoices
+NWC_URL_CIPHER_KEY=           # Nostr secret key (hex or nsec) used for NIP-44 encryption of tenant nwc_url at rest
 STRIPE_SECRET_KEY=            # Required Stripe API secret key (sk_...)
 STRIPE_WEBHOOK_SECRET=whsec_test_00000000000000000000000000  # Webhook signing secret (use real value in production)

backend/README.md

@@ -30,29 +30,30 @@ backend/
 
 Environment variables:
 
-| Variable                 | Description                                                             | Default                              |
+| Variable                 | Description                                                                             | Default                                  |
-| ------------------------ | ----------------------------------------------------------------------- | ------------------------------------ |
+| ------------------------ | --------------------------------------------------------------------------------------- | ---------------------------------------- |
-| `DATABASE_URL`           | SQLite URL. Relative paths are resolved under `backend/`.               | `sqlite://<backend>/data/caravel.db` |
+| `DATABASE_URL`           | SQLite URL. Relative paths are resolved under `backend/`.                               | `sqlite://<backend>/data/caravel.db`     |
-| `HOST`                   | API bind host (also used for NIP-98 `u` host check)                     | `127.0.0.1`                          |
+| `HOST`                   | API bind host (also used for NIP-98 `u` host check)                                     | `127.0.0.1`                              |
-| `PORT`                   | API bind port                                                           | `2892`                               |
+| `PORT`                   | API bind port                                                                           | `2892`                                   |
-| `ADMINS`                 | Comma-separated admin pubkeys (hex)                                     | _optional_                           |
+| `ADMINS`                 | Comma-separated admin pubkeys (hex)                                                     | _optional_                               |
-| `ALLOW_ORIGINS`          | Comma-separated CORS origins. If empty, CORS is permissive.             | _optional_                           |
+| `ALLOW_ORIGINS`          | Comma-separated CORS origins. If empty, CORS is permissive.                             | _optional_                               |
-| `ZOOID_API_URL`          | Zooid API base URL used by infra worker                                 | _required for infra sync_            |
+| `ZOOID_API_URL`          | Zooid API base URL used by infra worker                                                 | _required for infra sync_                |
-| `ZOOID_API_SECRET`       | Nostr secret key used for authentication of requests to the zooid API   | _required_                           |
+| `ZOOID_API_SECRET`       | Nostr secret key used for authentication of requests to the zooid API                   | _required_                               |
-| `RELAY_DOMAIN`           | Base domain appended to relay subdomains                                | empty                                |
+| `RELAY_DOMAIN`           | Base domain appended to relay subdomains                                                | empty                                    |
-| `LIVEKIT_URL`            | LiveKit URL sent to zooid when relay livekit is enabled                 | _optional_                           |
+| `LIVEKIT_URL`            | LiveKit URL sent to zooid when relay livekit is enabled                                 | _optional_                               |
-| `LIVEKIT_API_KEY`        | LiveKit API key sent to zooid                                           | _optional_                           |
+| `LIVEKIT_API_KEY`        | LiveKit API key sent to zooid                                                           | _optional_                               |
-| `LIVEKIT_API_SECRET`     | LiveKit API secret sent to zooid                                        | _optional_                           |
+| `LIVEKIT_API_SECRET`     | LiveKit API secret sent to zooid                                                        | _optional_                               |
-| `NWC_URL`                | Platform NWC URL used to generate BOLT11 invoices                       | _required for invoice generation_    |
+| `NWC_URL`                | Platform NWC URL used to generate BOLT11 invoices                                       | _required for invoice generation_        |
-| `STRIPE_SECRET_KEY`      | Stripe API secret key used for billing API operations                   | _required_                           |
+| `NWC_URL_CIPHER_KEY`     | Nostr secret key (hex or `nsec`) used for NIP-44 encryption of tenant `nwc_url` at rest | _required when tenant `nwc_url` is used_ |
-| `STRIPE_WEBHOOK_SECRET`  | Stripe webhook signing secret used to verify `Stripe-Signature` headers | _required_                           |
+| `STRIPE_SECRET_KEY`      | Stripe API secret key used for billing API operations                                   | _required_                               |
-| `ROBOT_SECRET`           | Robot Nostr secret key                                                  | _required_                           |
+| `STRIPE_WEBHOOK_SECRET`  | Stripe webhook signing secret used to verify `Stripe-Signature` headers                 | _required_                               |
-| `ROBOT_NAME`             | Robot display name (kind `0`)                                           | _optional_                           |
+| `ROBOT_SECRET`           | Robot Nostr secret key                                                                  | _required_                               |
-| `ROBOT_DESCRIPTION`      | Robot description (kind `0`)                                            | _optional_                           |
+| `ROBOT_NAME`             | Robot display name (kind `0`)                                                           | _optional_                               |
-| `ROBOT_PICTURE`          | Robot picture URL (kind `0`)                                            | _optional_                           |
+| `ROBOT_DESCRIPTION`      | Robot description (kind `0`)                                                            | _optional_                               |
-| `ROBOT_OUTBOX_RELAYS`    | Comma-separated relays published as kind `10002`                        | _required_                           |
+| `ROBOT_PICTURE`          | Robot picture URL (kind `0`)                                                            | _optional_                               |
-| `ROBOT_INDEXER_RELAYS`   | Comma-separated relays used for recipient relay discovery               | _required_                           |
+| `ROBOT_OUTBOX_RELAYS`    | Comma-separated relays published as kind `10002`                                        | _required_                               |
-| `ROBOT_MESSAGING_RELAYS` | Comma-separated relays published as kind `10050`                        | _required_                           |
+| `ROBOT_INDEXER_RELAYS`   | Comma-separated relays used for recipient relay discovery                               | _required_                               |
+| `ROBOT_MESSAGING_RELAYS` | Comma-separated relays published as kind `10050`                                        | _required_                               |
 
 Relay list env vars are comma-separated and trimmed. If a relay has no `ws://` or `wss://` scheme, `wss://` is prepended.
 

backend/src/api.rs

@@ -445,6 +445,18 @@ struct IdentityResponse {
     is_admin: bool,
 }
 
+#[derive(Serialize)]
+struct TenantResponse {
+    pubkey: String,
+    nwc_url: String,
+    nwc_configured: bool,
+    nwc_error: Option<String>,
+    created_at: i64,
+    stripe_customer_id: String,
+    stripe_subscription_id: Option<String>,
+    past_due_at: Option<i64>,
+}
+
 #[derive(Deserialize)]
 struct CreateRelayRequest {
     tenant: String,
@@ -486,7 +498,7 @@ async fn list_tenants(
     state.api.require_admin(&pubkey)?;
 
     match state.api.query.list_tenants().await {
-        Ok(tenants) => Ok(ok(StatusCode::OK, tenants)),
+        Ok(tenants) => Ok(ok(StatusCode::OK, scrub_tenants_for_response(tenants))),
         Err(e) => Ok(err(
             StatusCode::INTERNAL_SERVER_ERROR,
             "internal",
@@ -515,7 +527,7 @@ async fn create_tenant(
     let pubkey = state.api.extract_auth_pubkey(&headers)?;
 
     match state.api.query.get_tenant(&pubkey).await {
-        Ok(Some(t)) => Ok(ok(StatusCode::OK, t)),
+        Ok(Some(t)) => Ok(ok(StatusCode::OK, scrub_tenant_for_response(t))),
         Ok(None) => {
             let stripe_customer_id = match state.api.billing.stripe_create_customer(&pubkey).await {
                 Ok(id) => id,
@@ -539,10 +551,10 @@ async fn create_tenant(
             };
 
             match state.api.command.create_tenant(&tenant).await {
-                Ok(()) => Ok(ok(StatusCode::OK, tenant)),
+                Ok(()) => Ok(ok(StatusCode::OK, scrub_tenant_for_response(tenant))),
                 Err(e) if matches!(map_unique_error(&e), Some("pubkey-exists")) => {
                     match state.api.query.get_tenant(&pubkey).await {
-                        Ok(Some(t)) => Ok(ok(StatusCode::OK, t)),
+                        Ok(Some(t)) => Ok(ok(StatusCode::OK, scrub_tenant_for_response(t))),
                         Ok(None) => Ok(err(
                             StatusCode::INTERNAL_SERVER_ERROR,
                             "internal",
@@ -585,7 +597,7 @@ async fn get_tenant(
     let auth = state.api.extract_auth_pubkey(&headers)?;
     state.api.require_admin_or_tenant(&auth, &pubkey)?;
     let tenant = state.api.get_tenant_or_404(&pubkey).await?;
-    Ok(ok(StatusCode::OK, tenant))
+    Ok(ok(StatusCode::OK, scrub_tenant_for_response(tenant)))
 }
 
 async fn list_relays(
@@ -1122,7 +1134,7 @@ async fn update_tenant(
                     }
                 });
             }
-            Ok(ok(StatusCode::OK, tenant))
+            Ok(ok(StatusCode::OK, scrub_tenant_for_response(tenant)))
         }
         Err(e) => Ok(err(
             StatusCode::INTERNAL_SERVER_ERROR,
@@ -1131,3 +1143,20 @@ async fn update_tenant(
         )),
     }
 }
+
+fn scrub_tenant_for_response(tenant: Tenant) -> TenantResponse {
+    TenantResponse {
+        pubkey: tenant.pubkey,
+        nwc_url: String::new(),
+        nwc_configured: !tenant.nwc_url.is_empty(),
+        nwc_error: tenant.nwc_error,
+        created_at: tenant.created_at,
+        stripe_customer_id: tenant.stripe_customer_id,
+        stripe_subscription_id: tenant.stripe_subscription_id,
+        past_due_at: tenant.past_due_at,
+    }
+}
+
+fn scrub_tenants_for_response(tenants: Vec<Tenant>) -> Vec<TenantResponse> {
+    tenants.into_iter().map(scrub_tenant_for_response).collect()
+}

backend/src/billing.rs

@@ -151,7 +151,11 @@ impl Billing {
             return Ok(());
         }
 
-        tracing::info!(source, relay_count = relays.len(), "reconciling relay billing state");
+        tracing::info!(
+            source,
+            relay_count = relays.len(),
+            "reconciling relay billing state"
+        );
 
         for relay in relays {
             if let Err(error) = self.sync_relay_subscription_for_relay(&relay).await {
@@ -995,8 +999,7 @@ impl Billing {
         customer_id: &str,
         price_id: &str,
     ) -> Result<(String, String)> {
-        let idempotency_key =
+        let idempotency_key = self.idempotency_key(&["create_subscription", customer_id, price_id]);
-            self.idempotency_key(&["create_subscription", customer_id, price_id]);
         let resp = self
             .http
             .post(format!("{STRIPE_API}/subscriptions"))
@@ -1723,5 +1726,4 @@ mod tests {
         assert_eq!(billing.stripe_secret_key, "sk_test_dummy");
         assert_eq!(billing.stripe_webhook_secret, "whsec_test_dummy");
     }
-
 }

backend/src/command.rs

@@ -70,6 +70,7 @@ impl Command {
             anyhow::bail!("stripe_customer_id is required");
         }
 
+        let encrypted_nwc_url = tenant.encrypted_nwc_url_for_storage()?;
         let mut tx = self.pool.begin().await?;
 
         sqlx::query(
@@ -77,7 +78,7 @@ impl Command {
              VALUES (?, ?, ?, ?)",
         )
         .bind(&tenant.pubkey)
-        .bind(&tenant.nwc_url)
+        .bind(&encrypted_nwc_url)
         .bind(tenant.created_at)
         .bind(&tenant.stripe_customer_id)
         .execute(&mut *tx)
@@ -92,10 +93,11 @@ impl Command {
     }
 
     pub async fn update_tenant(&self, tenant: &Tenant) -> Result<()> {
+        let encrypted_nwc_url = tenant.encrypted_nwc_url_for_storage()?;
         let mut tx = self.pool.begin().await?;
 
         sqlx::query("UPDATE tenant SET nwc_url = ? WHERE pubkey = ?")
-            .bind(&tenant.nwc_url)
+            .bind(&encrypted_nwc_url)
             .bind(&tenant.pubkey)
             .execute(&mut *tx)
             .await?;

backend/src/infra.rs

@@ -106,7 +106,11 @@ impl Infra {
             return Ok(());
         }
 
-        tracing::info!(source, relay_count = relays.len(), "reconciling pending relay state");
+        tracing::info!(
+            source,
+            relay_count = relays.len(),
+            "reconciling pending relay state"
+        );
 
         for relay in relays {
             if relay.sync_error.trim().is_empty() {

backend/src/models.rs

@@ -1,5 +1,10 @@
+use anyhow::{Result, anyhow};
+use nostr_sdk::prelude::{Keys, nip44};
 use serde::{Deserialize, Serialize};
 
+const NIP44_ENVELOPE_PREFIX: &str = "enc:nip44:v2:";
+const LEGACY_ENVELOPE_PREFIX: &str = "enc:v1:";
+
 pub const RELAY_STATUS_ACTIVE: &str = "active";
 pub const RELAY_STATUS_INACTIVE: &str = "inactive";
 pub const RELAY_STATUS_DELINQUENT: &str = "delinquent";
@@ -36,6 +41,68 @@ pub struct Tenant {
     pub past_due_at: Option<i64>,
 }
 
+impl Tenant {
+    pub fn encrypted_nwc_url_for_storage(&self) -> Result<String> {
+        Self::encrypt_nwc_url_for_storage(&self.nwc_url)
+    }
+
+    pub fn decrypt_nwc_url_from_storage(&mut self) -> Result<()> {
+        self.nwc_url = Self::decrypt_nwc_url_value_from_storage(&self.nwc_url)?;
+        Ok(())
+    }
+
+    fn encrypt_nwc_url_for_storage(value: &str) -> Result<String> {
+        if value.is_empty() {
+            return Ok(String::new());
+        }
+
+        let keys = Self::parse_nwc_url_cipher_keys()?;
+        let payload = nip44::encrypt(
+            keys.secret_key(),
+            &keys.public_key(),
+            value,
+            nip44::Version::V2,
+        )
+        .map_err(|e| anyhow!("failed to encrypt nwc_url with NIP-44: {e}"))?;
+
+        Ok(format!("{NIP44_ENVELOPE_PREFIX}{payload}"))
+    }
+
+    fn decrypt_nwc_url_value_from_storage(value: &str) -> Result<String> {
+        if value.is_empty() {
+            return Ok(String::new());
+        }
+
+        if value.starts_with(LEGACY_ENVELOPE_PREFIX) {
+            return Err(anyhow!(
+                "unsupported legacy encrypted nwc_url envelope; re-save tenant configuration"
+            ));
+        }
+
+        let Some(payload) = value.strip_prefix(NIP44_ENVELOPE_PREFIX) else {
+            return Ok(value.to_string());
+        };
+
+        let keys = Self::parse_nwc_url_cipher_keys()?;
+        nip44::decrypt(keys.secret_key(), &keys.public_key(), payload)
+            .map_err(|e| anyhow!("failed to decrypt nwc_url with NIP-44: {e}"))
+    }
+
+    fn parse_nwc_url_cipher_keys() -> Result<Keys> {
+        let raw = std::env::var("NWC_URL_CIPHER_KEY")
+            .map_err(|_| anyhow!("missing NWC_URL_CIPHER_KEY environment variable"))?;
+        let trimmed = raw.trim();
+
+        if trimmed.is_empty() {
+            return Err(anyhow!("missing NWC_URL_CIPHER_KEY environment variable"));
+        }
+
+        Keys::parse(trimmed).map_err(|e| {
+            anyhow!("NWC_URL_CIPHER_KEY must be a valid nostr secret key (hex or nsec): {e}")
+        })
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, sqlx::FromRow)]
 pub struct Relay {
     pub id: String,

backend/src/query.rs

@@ -21,7 +21,7 @@ impl Query {
         )
         .fetch_all(&self.pool)
         .await?;
-        Ok(rows)
+        rows.into_iter().map(decrypt_tenant_nwc_url).collect()
     }
 
     pub async fn get_tenant(&self, pubkey: &str) -> Result<Option<Tenant>> {
@@ -33,7 +33,7 @@ impl Query {
         .bind(pubkey)
         .fetch_optional(&self.pool)
         .await?;
-        Ok(row)
+        row.map(decrypt_tenant_nwc_url).transpose()
     }
 
     pub fn list_plans() -> Vec<Plan> {
@@ -158,7 +158,7 @@ impl Query {
         .bind(stripe_customer_id)
         .fetch_optional(&self.pool)
         .await?;
-        Ok(row)
+        row.map(decrypt_tenant_nwc_url).transpose()
     }
 
     pub async fn get_invoice_nwc_payment_state(&self, invoice_id: &str) -> Result<Option<String>> {
@@ -224,3 +224,8 @@ impl Query {
         Ok(found.is_some())
     }
 }
+
+fn decrypt_tenant_nwc_url(mut tenant: Tenant) -> Result<Tenant> {
+    tenant.decrypt_nwc_url_from_storage()?;
+    Ok(tenant)
+}

frontend/src/lib/api.ts

@@ -99,6 +99,7 @@ export type UpdateRelayInput = {
 export type Tenant = {
   pubkey: string
   nwc_url: string
+  nwc_configured: boolean
   created_at: number
   stripe_customer_id: string
   stripe_subscription_id: string | null

frontend/src/lib/hooks.ts

@@ -135,7 +135,7 @@ export const reactivateRelayById = (id: string) => reactivateRelay(id)
 
 export async function tenantNeedsPaymentSetup(): Promise<boolean> {
   const tenant = await getTenant(account()!.pubkey)
-  return !tenant.nwc_url && !tenant.stripe_subscription_id
+  return !tenant.nwc_configured && !tenant.stripe_subscription_id
 }
 
 export async function getLatestOpenInvoice(): Promise<Invoice | null> {

frontend/src/pages/Account.tsx

@@ -18,9 +18,9 @@ export default function Account() {
   const invoicesLoading = useMinLoading(() => invoices.loading)
 
   const hasBillingChanges = createMemo(() => {
-    const current = tenant()?.nwc_url?.trim() ?? ""
     const next = nwcUrl().trim()
-    return current !== next
+    if (next) return true
+    return tenant()?.nwc_configured ?? false
   })
 
   createEffect(() => {
@@ -169,7 +169,7 @@ export default function Account() {
                               <p class="text-xs text-gray-500 mt-0.5">{periodLabel()}</p>
                             </Show>
                           </div>
-                          <div class="flex items-center gap-2 flex-shrink-0">
+                          <div class="flex items-center gap-2 shrink-0">
                             <Show when={isOpen()}>
                               <span class="text-xs text-blue-600 font-medium">Pay now</span>
                             </Show>

frontend/src/pages/relays/RelayDetail.tsx

@@ -52,7 +52,7 @@ export default function RelayDetail() {
     if (!isPaidRelay()) return false
     const t = tenant()
     if (!t) return false
-    return !t.nwc_url
+    return !t.nwc_configured
   })
 
   return (