Appfolio Security Basics

---
name: appfolio-security-basics
description: 'Secure AppFolio API credentials and tenant data.

  Trigger: "appfolio security".

  '
allowed-tools: Read, Write, Edit, Bash(npm:*), Bash(curl:*), Grep
version: 1.0.0
license: MIT
author: Jeremy Longshore <jeremy@intentsolutions.io>
tags:
- saas
- property-management
- appfolio
- real-estate
compatibility: Designed for Claude Code
---
# AppFolio Security Basics

## Overview

AppFolio manages property portfolios containing tenant PII (SSNs, bank accounts, lease terms), owner financial data, and maintenance vendor records. A breach exposes rent rolls, payment histories, and personally identifiable tenant information across every managed property. Secure every integration point: API credentials, webhook endpoints, and any pipeline that touches tenant or owner financial records.

## API Key Management

```typescript
import https from "https";
import axios, { AxiosInstance } from "axios";

function createAppFolioClient(): AxiosInstance {
  const clientId = process.env.APPFOLIO_CLIENT_ID;
  const clientSecret = process.env.APPFOLIO_CLIENT_SECRET;
  const baseUrl = process.env.APPFOLIO_BASE_URL;
  if (!clientId || !clientSecret || !baseUrl) {
    throw new Error("Missing APPFOLIO_CLIENT_ID, APPFOLIO_CLIENT_SECRET, or APPFOLIO_BASE_URL");
  }
  return axios.create({
    baseURL: baseUrl,
    auth: { username: clientId, password: clientSecret },
    httpsAgent: new https.Agent({ minVersion: "TLSv1.2", rejectUnauthorized: true }),
  });
}
```

## Webhook Signature Verification

```typescript
import crypto from "crypto";

function verifyAppFolioWebhook(req: Request, res: Response, next: NextFunction): void {
  const signature = req.headers["x-appfolio-signature"] as string;
  const secret = process.env.APPFOLIO_WEBHOOK_SECRET!;
  const expected = crypto.createHmac("sha256", secret).update(req.body).digest("hex");
  if (!signature || !crypto.timingSafeEqual(Buffer.from(signature), Buffer.from(expected))) {
    res.status(401).send("Invalid signature");
    return;
  }
  next();
}
```

## Input Validation

```typescript
import { z } from "zod";
const TenantSchema = z.object({
  tenant_id: z.string().uuid(),
  first_name: z.string().min(1).max(100),
  last_name: z.string().min(1).max(100),
  email: z.string().email(),
  unit_id: z.string().uuid(),
  lease_start: z.string().regex(/^\d{4}-\d{2}-\d{2}$/),
  rent_amount: z.number().positive().max(100000),
});

function validateTenantPayload(data: unknown) {
  return TenantSchema.parse(data);
}
```

## Data Protection

```typescript
const APPFOLIO_PII_FIELDS = ["ssn", "bank_account", "routing_number", "date_of_birth", "drivers_license"];

function redactAppFolioLog(record: Record<string, unknown>): Record<string, unknown> {
  const redacted = { ...record };
  for (const field of APPFOLIO_PII_FIELDS) {
    if (field in redacted) redacted[field] = "[REDACTED]";
  }
  return redacted;
}
```

## Security Checklist

- [ ] API credentials stored in secrets manager, not `.env` in production
- [ ] HTTPS enforced with TLS 1.2+ for all API calls
- [ ] Tenant SSN and bank account numbers never logged
- [ ] Webhook signatures verified on every inbound request
- [ ] API credentials rotated quarterly
- [ ] Access scoped to minimum required property endpoints
- [ ] Rent payment data encrypted at rest
- [ ] Audit trail enabled for tenant record access

## Error Handling

| Vulnerability | Risk | Mitigation |
|---|---|---|
| Leaked API credentials | Full property portfolio exposure | Secrets manager + rotation |
| Unvalidated webhook payloads | Spoofed tenant updates | HMAC signature verification |
| Tenant PII in logs | Compliance violation (state privacy laws) | Field-level redaction |
| Overly broad API scope | Lateral access to unrelated properties | Per-property credential scoping |
| Unencrypted payment data | Financial data breach | TLS 1.2+ in transit, AES at rest |

## Resources

- [AppFolio Stack APIs](https://www.appfolio.com/stack/partners/api)
- [OWASP API Security Top 10](https://owasp.org/www-project-api-security/)

## Next Steps

See `appfolio-prod-checklist`.