apps/api/src/app.module.ts

@@ -39,6 +39,7 @@ import { JobStepsModule } from "./job-steps/job-steps.module";
 import { CoordinatorIntegrationModule } from "./coordinator-integration/coordinator-integration.module";
 import { FederationModule } from "./federation/federation.module";
 import { CredentialsModule } from "./credentials/credentials.module";
+import { CryptoModule } from "./crypto/crypto.module";
 import { MosaicTelemetryModule } from "./mosaic-telemetry";
 import { SpeechModule } from "./speech/speech.module";
 import { DashboardModule } from "./dashboard/dashboard.module";
@@ -111,6 +112,7 @@ import { RlsContextInterceptor } from "./common/interceptors/rls-context.interce
     CoordinatorIntegrationModule,
     FederationModule,
     CredentialsModule,
+    CryptoModule,
     MosaicTelemetryModule,
     SpeechModule,
     DashboardModule,

apps/api/src/crypto/crypto.module.ts

@@ -0,0 +1,10 @@
+import { Module } from "@nestjs/common";
+import { ConfigModule } from "@nestjs/config";
+import { CryptoService } from "./crypto.service";
+
+@Module({
+  imports: [ConfigModule],
+  providers: [CryptoService],
+  exports: [CryptoService],
+})
+export class CryptoModule {}

apps/api/src/crypto/crypto.service.spec.ts

@@ -0,0 +1,71 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { ConfigService } from "@nestjs/config";
+import { CryptoService } from "./crypto.service";
+
+function createConfigService(secret?: string): ConfigService {
+  return {
+    get: (key: string) => {
+      if (key === "MOSAIC_SECRET_KEY") {
+        return secret;
+      }
+      return undefined;
+    },
+  } as unknown as ConfigService;
+}
+
+describe("CryptoService", () => {
+  let service: CryptoService;
+
+  beforeEach(() => {
+    service = new CryptoService(createConfigService("this-is-a-test-secret-key-with-32+chars"));
+  });
+
+  it("encrypt -> decrypt roundtrip", () => {
+    const plaintext = "my-secret-api-key";
+
+    const encrypted = service.encrypt(plaintext);
+    const decrypted = service.decrypt(encrypted);
+
+    expect(encrypted.startsWith("enc:")).toBe(true);
+    expect(decrypted).toBe(plaintext);
+  });
+
+  it("decrypt rejects tampered ciphertext", () => {
+    const encrypted = service.encrypt("sensitive-token");
+    const payload = encrypted.slice(4);
+    const bytes = Buffer.from(payload, "base64");
+
+    bytes[bytes.length - 1] = bytes[bytes.length - 1]! ^ 0xff;
+
+    const tampered = `enc:${bytes.toString("base64")}`;
+
+    expect(() => service.decrypt(tampered)).toThrow();
+  });
+
+  it("decrypt rejects non-encrypted string", () => {
+    expect(() => service.decrypt("plain-text-value")).toThrow();
+  });
+
+  it("isEncrypted detects prefix correctly", () => {
+    expect(service.isEncrypted("enc:abc")).toBe(true);
+    expect(service.isEncrypted("ENC:abc")).toBe(false);
+    expect(service.isEncrypted("plain-text")).toBe(false);
+  });
+
+  it("generateToken returns 64-char hex string", () => {
+    const token = service.generateToken();
+
+    expect(token).toMatch(/^[0-9a-f]{64}$/);
+  });
+
+  it("different plaintexts produce different ciphertexts (random IV)", () => {
+    const encryptedA = service.encrypt("value-a");
+    const encryptedB = service.encrypt("value-b");
+
+    expect(encryptedA).not.toBe(encryptedB);
+  });
+
+  it("missing MOSAIC_SECRET_KEY throws on construction", () => {
+    expect(() => new CryptoService(createConfigService(undefined))).toThrow();
+  });
+});

apps/api/src/crypto/crypto.service.ts

@@ -0,0 +1,82 @@
+import { Injectable } from "@nestjs/common";
+import { ConfigService } from "@nestjs/config";
+import { createCipheriv, createDecipheriv, hkdfSync, randomBytes } from "crypto";
+
+const ALGORITHM = "aes-256-gcm";
+const ENCRYPTED_PREFIX = "enc:";
+const IV_LENGTH = 12;
+const AUTH_TAG_LENGTH = 16;
+const DERIVED_KEY_LENGTH = 32;
+const HKDF_SALT = "mosaic.crypto.v1";
+const HKDF_INFO = "mosaic-db-secret-encryption";
+
+@Injectable()
+export class CryptoService {
+  private readonly key: Buffer;
+
+  constructor(private readonly config: ConfigService) {
+    const secret = this.config.get<string>("MOSAIC_SECRET_KEY");
+
+    if (!secret) {
+      throw new Error("MOSAIC_SECRET_KEY environment variable is required");
+    }
+
+    if (secret.length < 32) {
+      throw new Error("MOSAIC_SECRET_KEY must be at least 32 characters");
+    }
+
+    this.key = Buffer.from(
+      hkdfSync(
+        "sha256",
+        Buffer.from(secret, "utf8"),
+        Buffer.from(HKDF_SALT, "utf8"),
+        Buffer.from(HKDF_INFO, "utf8"),
+        DERIVED_KEY_LENGTH
+      )
+    );
+  }
+
+  encrypt(plaintext: string): string {
+    const iv = randomBytes(IV_LENGTH);
+    const cipher = createCipheriv(ALGORITHM, this.key, iv);
+    const ciphertext = Buffer.concat([cipher.update(plaintext, "utf8"), cipher.final()]);
+    const authTag = cipher.getAuthTag();
+    const payload = Buffer.concat([iv, ciphertext, authTag]).toString("base64");
+
+    return `${ENCRYPTED_PREFIX}${payload}`;
+  }
+
+  decrypt(encrypted: string): string {
+    if (!this.isEncrypted(encrypted)) {
+      throw new Error("Value is not encrypted");
+    }
+
+    const payloadBase64 = encrypted.slice(ENCRYPTED_PREFIX.length);
+
+    try {
+      const payload = Buffer.from(payloadBase64, "base64");
+      if (payload.length < IV_LENGTH + AUTH_TAG_LENGTH) {
+        throw new Error("Encrypted payload is too short");
+      }
+
+      const iv = payload.subarray(0, IV_LENGTH);
+      const authTag = payload.subarray(payload.length - AUTH_TAG_LENGTH);
+      const ciphertext = payload.subarray(IV_LENGTH, payload.length - AUTH_TAG_LENGTH);
+
+      const decipher = createDecipheriv(ALGORITHM, this.key, iv);
+      decipher.setAuthTag(authTag);
+
+      return Buffer.concat([decipher.update(ciphertext), decipher.final()]).toString("utf8");
+    } catch {
+      throw new Error("Failed to decrypt value");
+    }
+  }
+
+  isEncrypted(value: string): boolean {
+    return value.startsWith(ENCRYPTED_PREFIX);
+  }
+
+  generateToken(): string {
+    return randomBytes(32).toString("hex");
+  }
+}