Add managed provider keys: encrypted store + env>DB resolver

AES-256-GCM encryption (KeyCipher) with master key from NEXUS_MASTER_KEY,
never persisted. ProvidersStore in SQLite: CRUD, enable/disable, default,
encrypted api keys, masked views for UI. KeyResolver applies env>DB precedence
and supports multiple providers. context.ts registers providers dynamically
from resolved config; backward compatible with env-only setups.

NexusAI/packages/core/src/config.ts

@@ -19,6 +19,10 @@ export interface NexusConfig {
   defaultProvider: string;
   mediaDir: string;
   dbPath: string;
+  /** SQLite path for the encrypted providers store (defaults to same as dbPath). */
+  providersDbPath: string;
+  /** Master secret for encrypting stored API keys (env NEXUS_MASTER_KEY). */
+  masterKey?: string;
   embedMaxBytes: number;
   nordrouter: NordRouterConfig;
   stt: SttConfig;
@@ -40,6 +44,8 @@ export function loadConfig(): NexusConfig {
     defaultProvider: process.env.NEXUS_DEFAULT_PROVIDER || 'nordrouter',
     mediaDir,
     dbPath,
+    providersDbPath: process.env.NEXUS_PROVIDERS_DB_PATH || dbPath,
+    masterKey: process.env.NEXUS_MASTER_KEY,
     embedMaxBytes: envInt('NEXUS_EMBED_MAX_BYTES', 10 * 1024 * 1024),
     nordrouter: {
       apiKey: process.env.NORDROUTER_API_KEY,

NexusAI/packages/core/src/db/providers-store.ts

@@ -0,0 +1,187 @@
+import Database from 'better-sqlite3';
+import * as fs from 'fs';
+import * as path from 'path';
+import { NexusError } from '../shared/errors.js';
+import { createLogger } from '../shared/logger.js';
+import { KeyCipher, maskSecret } from '../security/crypto.js';
+
+const log = createLogger('providers-store');
+
+export interface ProviderRow {
+  name: string;
+  type: string; // e.g. "nordrouter" | "routerai" | "openrouter"
+  baseUrl: string | null;
+  enabled: boolean;
+  isDefault: boolean;
+  createdAt: string;
+  updatedAt: string;
+}
+
+/** Public view: never exposes the raw key, only a masked hint. */
+export interface ProviderView extends ProviderRow {
+  hasKey: boolean;
+  keyHint: string | null;
+}
+
+export interface UpsertProviderInput {
+  name: string;
+  type: string;
+  baseUrl?: string | null;
+  apiKey?: string; // plaintext; will be encrypted at rest
+  enabled?: boolean;
+  isDefault?: boolean;
+}
+
+/**
+ * SQLite-backed provider registry with encrypted API keys.
+ * Managed by the admin (Phase 2); read by the MCP server at startup.
+ */
+export class ProvidersStore {
+  private readonly db: Database.Database;
+
+  constructor(dbPath: string, private readonly cipher: KeyCipher) {
+    fs.mkdirSync(path.dirname(dbPath), { recursive: true });
+    this.db = new Database(dbPath);
+    this.db.pragma('journal_mode = WAL');
+    this.init();
+  }
+
+  private init(): void {
+    this.db.exec(`
+      CREATE TABLE IF NOT EXISTS providers (
+        name TEXT PRIMARY KEY,
+        type TEXT NOT NULL,
+        base_url TEXT,
+        api_key_enc TEXT,
+        enabled INTEGER NOT NULL DEFAULT 1,
+        is_default INTEGER NOT NULL DEFAULT 0,
+        created_at TEXT NOT NULL,
+        updated_at TEXT NOT NULL
+      );
+    `);
+  }
+
+  upsert(input: UpsertProviderInput): void {
+    const now = new Date().toISOString();
+    const encKey = input.apiKey !== undefined ? this.cipher.encrypt(input.apiKey) : undefined;
+
+    const existing = this.db.prepare('SELECT name FROM providers WHERE name = ?').get(input.name);
+
+    if (existing) {
+      // Update only provided fields; keep existing key if not supplied.
+      this.db
+        .prepare(
+          `UPDATE providers SET
+             type = @type,
+             base_url = COALESCE(@baseUrl, base_url),
+             api_key_enc = COALESCE(@encKey, api_key_enc),
+             enabled = @enabled,
+             is_default = @isDefault,
+             updated_at = @now
+           WHERE name = @name`
+        )
+        .run({
+          name: input.name,
+          type: input.type,
+          baseUrl: input.baseUrl ?? null,
+          encKey: encKey ?? null,
+          enabled: input.enabled === false ? 0 : 1,
+          isDefault: input.isDefault ? 1 : 0,
+          now,
+        });
+    } else {
+      this.db
+        .prepare(
+          `INSERT INTO providers (name, type, base_url, api_key_enc, enabled, is_default, created_at, updated_at)
+           VALUES (@name, @type, @baseUrl, @encKey, @enabled, @isDefault, @now, @now)`
+        )
+        .run({
+          name: input.name,
+          type: input.type,
+          baseUrl: input.baseUrl ?? null,
+          encKey: encKey ?? null,
+          enabled: input.enabled === false ? 0 : 1,
+          isDefault: input.isDefault ? 1 : 0,
+          now,
+        });
+    }
+
+    if (input.isDefault) this.setDefault(input.name);
+    log.info(`provider upserted: ${input.name}`);
+  }
+
+  setEnabled(name: string, enabled: boolean): void {
+    const r = this.db
+      .prepare('UPDATE providers SET enabled = ?, updated_at = ? WHERE name = ?')
+      .run(enabled ? 1 : 0, new Date().toISOString(), name);
+    if (r.changes === 0) throw new NexusError('NOT_FOUND', `Provider not found: ${name}`);
+  }
+
+  setDefault(name: string): void {
+    const exists = this.db.prepare('SELECT 1 FROM providers WHERE name = ?').get(name);
+    if (!exists) throw new NexusError('NOT_FOUND', `Provider not found: ${name}`);
+    const tx = this.db.transaction(() => {
+      this.db.prepare('UPDATE providers SET is_default = 0').run();
+      this.db
+        .prepare('UPDATE providers SET is_default = 1, updated_at = ? WHERE name = ?')
+        .run(new Date().toISOString(), name);
+    });
+    tx();
+  }
+
+  remove(name: string): void {
+    this.db.prepare('DELETE FROM providers WHERE name = ?').run(name);
+  }
+
+  /** Return the decrypted API key for a provider, or undefined. */
+  getApiKey(name: string): string | undefined {
+    const row = this.db.prepare('SELECT api_key_enc FROM providers WHERE name = ?').get(name) as
+      | { api_key_enc: string | null }
+      | undefined;
+    if (!row?.api_key_enc) return undefined;
+    return this.cipher.decrypt(row.api_key_enc);
+  }
+
+  get(name: string): ProviderRow | undefined {
+    const row = this.db.prepare('SELECT * FROM providers WHERE name = ?').get(name) as any;
+    return row ? this.mapRow(row) : undefined;
+  }
+
+  list(): ProviderRow[] {
+    const rows = this.db.prepare('SELECT * FROM providers ORDER BY name').all() as any[];
+    return rows.map((r) => this.mapRow(r));
+  }
+
+  /** Admin-safe listing: masked key hint, never the raw key. */
+  listViews(): ProviderView[] {
+    const rows = this.db.prepare('SELECT * FROM providers ORDER BY name').all() as any[];
+    return rows.map((r) => {
+      const base = this.mapRow(r);
+      let keyHint: string | null = null;
+      if (r.api_key_enc) {
+        try {
+          keyHint = maskSecret(this.cipher.decrypt(r.api_key_enc));
+        } catch {
+          keyHint = '(undecryptable)';
+        }
+      }
+      return { ...base, hasKey: Boolean(r.api_key_enc), keyHint };
+    });
+  }
+
+  private mapRow(r: any): ProviderRow {
+    return {
+      name: r.name,
+      type: r.type,
+      baseUrl: r.base_url,
+      enabled: Boolean(r.enabled),
+      isDefault: Boolean(r.is_default),
+      createdAt: r.created_at,
+      updatedAt: r.updated_at,
+    };
+  }
+
+  close(): void {
+    this.db.close();
+  }
+}

NexusAI/packages/core/src/index.ts

@@ -4,6 +4,9 @@ export * from './shared/logger.js';
 export * from './shared/http.js';
 export * from './shared/polling.js';
 export * from './db/journal.js';
+export * from './db/providers-store.js';
+export * from './security/crypto.js';
+export * from './security/resolver.js';
 export * from './media/storage.js';
 export * from './media/content.js';
 export * from './providers/types.js';

NexusAI/packages/core/src/security/crypto.ts

@@ -0,0 +1,88 @@
+import * as crypto from 'crypto';
+import { NexusError } from '../shared/errors.js';
+
+/**
+ * AES-256-GCM encryption for API keys at rest.
+ *
+ * The master key is provided via env NEXUS_MASTER_KEY and NEVER stored in the DB.
+ * Only encrypted key material lives in SQLite, so backups / inspection of the DB
+ * do not leak provider API keys. Rotating NEXUS_MASTER_KEY invalidates stored
+ * ciphertext (re-enter keys), which is the intended security trade-off.
+ *
+ * Ciphertext format (base64):  [ 12-byte IV | 16-byte auth tag | ciphertext ]
+ */
+
+const ALGO = 'aes-256-gcm';
+const IV_LEN = 12;
+const TAG_LEN = 16;
+
+/**
+ * Derive a 32-byte key from the env master secret. Accepts either a 64-char
+ * hex string (used directly) or any passphrase (hashed with SHA-256).
+ */
+export function deriveMasterKey(secret: string | undefined): Buffer | undefined {
+  if (!secret) return undefined;
+  const trimmed = secret.trim();
+  if (/^[0-9a-fA-F]{64}$/.test(trimmed)) {
+    return Buffer.from(trimmed, 'hex');
+  }
+  return crypto.createHash('sha256').update(trimmed, 'utf8').digest();
+}
+
+export class KeyCipher {
+  private readonly key?: Buffer;
+
+  constructor(masterSecret: string | undefined) {
+    this.key = deriveMasterKey(masterSecret);
+  }
+
+  get enabled(): boolean {
+    return this.key !== undefined;
+  }
+
+  private requireKey(): Buffer {
+    if (!this.key) {
+      throw new NexusError(
+        'CONFIG',
+        'NEXUS_MASTER_KEY is not set; cannot encrypt/decrypt stored API keys'
+      );
+    }
+    return this.key;
+  }
+
+  encrypt(plaintext: string): string {
+    const key = this.requireKey();
+    const iv = crypto.randomBytes(IV_LEN);
+    const cipher = crypto.createCipheriv(ALGO, key, iv);
+    const enc = Buffer.concat([cipher.update(plaintext, 'utf8'), cipher.final()]);
+    const tag = cipher.getAuthTag();
+    return Buffer.concat([iv, tag, enc]).toString('base64');
+  }
+
+  decrypt(payload: string): string {
+    const key = this.requireKey();
+    const raw = Buffer.from(payload, 'base64');
+    if (raw.length < IV_LEN + TAG_LEN) {
+      throw new NexusError('CONFIG', 'Malformed encrypted key payload');
+    }
+    const iv = raw.subarray(0, IV_LEN);
+    const tag = raw.subarray(IV_LEN, IV_LEN + TAG_LEN);
+    const enc = raw.subarray(IV_LEN + TAG_LEN);
+    const decipher = crypto.createDecipheriv(ALGO, key, iv);
+    decipher.setAuthTag(tag);
+    try {
+      return Buffer.concat([decipher.update(enc), decipher.final()]).toString('utf8');
+    } catch {
+      throw new NexusError(
+        'CONFIG',
+        'Failed to decrypt API key (wrong NEXUS_MASTER_KEY or corrupted data)'
+      );
+    }
+  }
+}
+
+/** Mask a secret for display: keep last 4 chars. */
+export function maskSecret(secret: string): string {
+  if (secret.length <= 4) return '****';
+  return `${secret.slice(0, 3)}…${secret.slice(-4)}`;
+}

NexusAI/packages/core/src/security/resolver.ts

@@ -0,0 +1,96 @@
+import type { NexusConfig } from '../config.js';
+import type { ProvidersStore } from '../db/providers-store.js';
+import { createLogger } from '../shared/logger.js';
+
+const log = createLogger('key-resolver');
+
+export interface ResolvedProvider {
+  name: string;
+  type: string;
+  baseUrl: string;
+  apiKey?: string;
+  enabled: boolean;
+  isDefault: boolean;
+  /** Where the key came from, for diagnostics. */
+  keySource: 'env' | 'db' | 'none';
+}
+
+/**
+ * Resolve effective provider settings.
+ *
+ * Precedence for keys: ENV wins over DB. This keeps simple/CI setups working
+ * (just set NORDROUTER_API_KEY) while allowing admin-managed keys in the DB.
+ *
+ * Built-in providers (nordrouter) are always considered; DB rows can add more
+ * or override base URL / enabled / default.
+ */
+export class KeyResolver {
+  constructor(
+    private readonly config: NexusConfig,
+    private readonly store?: ProvidersStore
+  ) {}
+
+  private envKeyFor(providerName: string): string | undefined {
+    // Convention: <NAME>_API_KEY, e.g. NORDROUTER_API_KEY
+    const envName = `${providerName.toUpperCase()}_API_KEY`;
+    return process.env[envName];
+  }
+
+  private envBaseUrlFor(providerName: string): string | undefined {
+    const envName = `${providerName.toUpperCase()}_BASE_URL`;
+    return process.env[envName];
+  }
+
+  /** Resolve one provider by name. */
+  resolve(providerName: string, defaultBaseUrl: string): ResolvedProvider {
+    const dbRow = this.store?.get(providerName);
+    const envKey = this.envKeyFor(providerName);
+    const dbKey = this.store?.getApiKey(providerName);
+
+    const apiKey = envKey ?? dbKey;
+    const keySource: ResolvedProvider['keySource'] = envKey ? 'env' : dbKey ? 'db' : 'none';
+
+    const baseUrl =
+      this.envBaseUrlFor(providerName) || dbRow?.baseUrl || defaultBaseUrl;
+
+    return {
+      name: providerName,
+      type: dbRow?.type ?? providerName,
+      baseUrl,
+      apiKey,
+      enabled: dbRow ? dbRow.enabled : true,
+      isDefault: dbRow?.isDefault ?? false,
+      keySource,
+    };
+  }
+
+  /** All providers to register: built-ins + any DB-managed ones. */
+  resolveAll(builtins: Array<{ name: string; defaultBaseUrl: string }>): ResolvedProvider[] {
+    const seen = new Set<string>();
+    const out: ResolvedProvider[] = [];
+
+    for (const b of builtins) {
+      out.push(this.resolve(b.name, b.defaultBaseUrl));
+      seen.add(b.name);
+    }
+
+    for (const row of this.store?.list() ?? []) {
+      if (seen.has(row.name)) continue;
+      out.push(this.resolve(row.name, row.baseUrl || ''));
+      seen.add(row.name);
+    }
+
+    log.debug(
+      'resolved providers',
+      out.map((p) => ({ name: p.name, key: p.keySource, enabled: p.enabled }))
+    );
+    return out;
+  }
+
+  /** The effective default provider name. */
+  resolveDefault(resolved: ResolvedProvider[]): string {
+    const dbDefault = resolved.find((p) => p.isDefault && p.enabled);
+    if (dbDefault) return dbDefault.name;
+    return this.config.defaultProvider;
+  }
+}