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Security Architecture

Drop Security Architecture

Last updated: 2026-02-14 Source: Security audit (security/drop-security-rapport.md), hardening implementation (security/security-hardening-implementation.md), source code

Architecture model: Drop uses a PSD2 pass-through model. It never holds customer money — AISP reads bank balances via Open Banking, PISP initiates payments from the user's bank account. Cards are a FUTURE feature, gated behind feature flags (all default to false).

Authentication

JWT Token Management

Library: jose ^6.1.3 (well-maintained, no known vulnerabilities) Algorithm: HS256 with explicit setProtectedHeader Source: src/drop-app/src/lib/auth.ts

Setting Value Source
Algorithm HS256 auth.ts
Expiry 24 hours auth.ts cookie maxAge: 60 * 60 * 24
setIssuedAt() Yes Prevents token reuse
Secret (production) JWT_SECRET env var Fatal error if missing
Secret (development) process.cwd() hash Dev fallback for uniqueness

⚠️ PSD2 SCA Gap: The 24h login session is acceptable for AISP (balance viewing) but non-compliant for PISP (payment initiation). PSD2 RTS Art. 4 requires per-transaction SCA with a 5-minute payment session window. See ADR-017: PSD2 SCA Payment Sessions for the remediation design.

Source: src/drop-app/src/lib/auth.ts:48-54

Property Value Purpose
httpOnly true Prevents JavaScript access (XSS mitigation)
secure true (production) HTTPS-only cookie transport
sameSite "strict" CSRF prevention
maxAge 24 hours Session lifetime
path "/" Cookie scope

Password Hashing

Library: bcryptjs ^3.0.3 (pure JS, no native compilation issues) Source: src/drop-app/src/lib/utils-server.ts:8-16

Setting Value
Algorithm bcrypt
Cost factor 12
SHA-256 fallback Removed (security fix C4)

After hardening, verifyPassword() only accepts bcrypt hashes. SHA-256 legacy support has been removed entirely.

Session Management

Source: src/drop-app/src/lib/auth.ts:45-65, src/lib/middleware.ts:42-77

Sessions are tracked in the sessions table:

Column Type Purpose
id TEXT PK Session identifier (format: ses_<hex16>)
user_id TEXT FK References users.id
token_hash TEXT SHA-256 hash of JWT token
expires_at TEXT Expiration timestamp
revoked INTEGER 0 = active, 1 = revoked

Lifecycle:

  1. Login -- Session created with token hash (auth.ts:56-65)
  2. Each request -- Session checked for revocation (middleware.ts:66-74)
  3. Logout -- All user sessions revoked server-side (auth/logout/route.ts:5-14)

Authorization

IDOR Protection

All data access queries include AND user_id = ? to scope data to the authenticated user:

  • Recipients: scoped to user
  • Cards: scoped to user
  • Transactions: scoped to user
  • Bank accounts: scoped to user
  • Notifications: scoped to user
  • Settings: scoped to user

Merchant endpoints verify merchant role and ownership.

Role-Based Access

Roles (from lib/db.ts schema CHECK constraint):

  • user -- Standard user
  • merchant -- Merchant with dashboard access

KYC Status (required for financial operations):

  • pending -- Default on registration
  • approved -- Required for remittance
  • rejected -- Blocked from financial operations

Input Validation

Rate Limiting

Source: src/drop-app/src/lib/middleware.ts:6-31

Endpoint Type Limit Window
Auth routes (login, register) 10 requests 60 seconds
Transaction routes (remittance, qr-payment) 10 requests 60 seconds
Rate endpoints (/api/rates) 120 requests 60 seconds

Implementation: PostgreSQL-backed persistent rate limiting (survives restarts). Per-IP tracking using X-Forwarded-For header. (ADR-014: SQLite removed 2026-03-03)

Rate limit table (rate_limits):

  • key -- IP address (TEXT PK)
  • count -- Request count (INTEGER)
  • reset_at -- Window expiry (INTEGER, Unix timestamp)

CSRF Protection

Source: src/drop-app/src/lib/middleware.ts:44-55

Origin header validation on all authenticated requests:

  • Validates Origin header against allowed origins list
  • Allowed origins: NEXT_PUBLIC_APP_URL, http://localhost:3000, http://localhost:3001
  • Combined with sameSite: "strict" cookies

Input Sanitization

Source: src/drop-app/src/lib/middleware/validation.ts:149-203

  • sanitizeText() -- Removes HTML tags, control characters, trims whitespace, enforces max length
  • validateName() -- Rejects XSS payloads, script tags, numbers-only names
  • validateEmail() -- Regex validation for email format
  • validatePhone() -- International format validation
  • validateAmount() -- Positive, finite, max 2 decimal places
  • validateIBAN() -- Format and checksum validation
  • validatePIN() -- Exactly 4 digits
  • validateCurrency() -- Whitelist: EUR, USD, GBP, BAM, CHF, PLN, NOK, RSD, TRY, PKR
  • validateLanguage() -- Whitelist: nb, en, bs, sq

Applied to: recipients, merchants, settings, notifications.

Amount Validation

Endpoint Min Max Source
Remittance 100 NOK 50,000 NOK transactions/remittance/route.ts
QR Payment 1 NOK 100,000 NOK transactions/qr-payment/route.ts

Additional checks: Number.isFinite() to prevent NaN/Infinity injection. Pagination limited to max 50 per page.

SQL Injection Prevention

All 24 API endpoints use parameterized queries exclusively (? placeholders). No string concatenation in SQL statements.

Example from transactions/route.ts:

// Dynamic WHERE clauses use parameter arrays
const conditions: string[] = [];
const params: unknown[] = [];
if (type) { conditions.push("type = ?"); params.push(type); }

Merchant dashboard uses strict whitelist for period parameter.

Security Headers

Source: src/drop-app/next.config.ts:6-46

Header Value
Content-Security-Policy default-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; ...
X-Frame-Options DENY
X-Content-Type-Options nosniff
Referrer-Policy strict-origin-when-cross-origin
Permissions-Policy camera=(self), microphone=(), geolocation=(self)
Strict-Transport-Security max-age=63072000; includeSubDomains; preload

Known limitation: CSP includes unsafe-inline and unsafe-eval (required for Next.js dev mode). Should be tightened with nonce-based CSP for production.

API Response Masking

  • Card numbers: Masked as **** **** **** XXXX in responses (cards/[id]/route.ts:25-35)
  • CVV: Displayed as *** in responses
  • Bank accounts: Only last 4 digits visible (utils-server.ts:23-26)

Transaction Integrity

Source: transactions/remittance/route.ts, transactions/qr-payment/route.ts

  • Atomic balance deduction using PostgreSQL transactions (Drizzle ORM)
  • WHERE balance >= $1 prevents overdraw
  • PostgreSQL MVCC with explicit FOR UPDATE row locking
  • Fee calculated and included in deduction

Feature Flags

Source: src/drop-app/src/lib/feature-flags.ts

Gated features (disabled by default):

Flag Env Var Default
virtualCards NEXT_PUBLIC_FF_VIRTUAL_CARDS false
physicalCards NEXT_PUBLIC_FF_PHYSICAL_CARDS false
cardDetails NEXT_PUBLIC_FF_CARD_DETAILS false
cardFreeze NEXT_PUBLIC_FF_CARD_FREEZE false
cardPin NEXT_PUBLIC_FF_CARD_PIN false
spendingLimits NEXT_PUBLIC_FF_SPENDING_LIMITS false
notifications NEXT_PUBLIC_FF_NOTIFICATIONS true
merchantDashboard NEXT_PUBLIC_FF_MERCHANT_DASHBOARD true

API routes check feature flags and return 404 when disabled.

Dependency Security

Package Version Risk Assessment
jose ^6.1.3 Low -- Well-maintained JWT library
bcryptjs ^3.0.3 Low -- Pure JS bcrypt
drizzle-orm latest Low -- Type-safe ORM, parameterized queries
next 16.1.6 Low -- Recent version
react 19.2.3 Low -- Latest major
radix-ui ^1.4.3 Low -- UI components only

No known vulnerable dependencies identified (from security/drop-security-rapport.md:400-411).

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