feat(api): add CryptoService for secret encryption (MS22-P1b)

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();
+  });
+});