contractshield 1.5.6

Contract-First API Security for Python

ContractShield

Contract-First API Security for Python

Protect your business logic, not just your formats. ContractShield validates API requests at the application layer using JSON Schema and CEL expressions.

🛡️ What is ContractShield?

ContractShield is an open-source API security middleware that:

• Validates contracts - Enforce JSON Schema + CEL business rules
• Blocks vulnerabilities - Detect SQLi, XSS, path traversal before they hit your code
• Complements your WAF - Protects business logic that infrastructure can't see

Client → WAF (format) → ContractShield (contract + logic) → Your App

📦 Installation

# Core package
pip install contractshield

# With FastAPI support
pip install contractshield[fastapi]

# With Flask support
pip install contractshield[flask]

# With CEL expressions
pip install contractshield[cel]

# Everything
pip install contractshield[all]

🚀 Quick Start

FastAPI

from fastapi import FastAPI
from contractshield.fastapi import ContractShieldMiddleware

app = FastAPI()

app.add_middleware(
    ContractShieldMiddleware,
    openapi_path="./openapi.yaml",
    enable_vulnerability_scan=True
)

@app.post("/api/transfer")
async def transfer(data: dict):
    # ContractShield has already validated:
    # - JSON Schema from OpenAPI spec
    # - CEL business rules
    # - No SQL injection / XSS in fields
    return {"status": "success"}

Flask

from flask import Flask
from contractshield.flask import ContractShieldMiddleware

app = Flask(__name__)
app.wsgi_app = ContractShieldMiddleware(
    app.wsgi_app,
    openapi_path="./openapi.yaml"
)

@app.route("/api/transfer", methods=["POST"])
def transfer():
    return {"status": "success"}

📋 OpenAPI Example

# openapi.yaml
openapi: 3.0.3
info:
  title: Banking API
  version: 1.0.0
paths:
  /api/transfer:
    post:
      requestBody:
        content:
          application/json:
            schema:
              type: object
              required: [amount, currency]
              properties:
                amount:
                  type: number
                  minimum: 0.01
                  maximum: 100000
                currency:
                  type: string
                  enum: [CHF, EUR, USD]
              x-cel-expression: "amount > 0 && amount <= user.dailyLimit"

🔒 Vulnerability Detection

ContractShield scans all incoming data for:

Vulnerability	Example
SQL Injection	' OR 1=1 --
XSS	<script>alert(1)</script>
Path Traversal	../../etc/passwd
Prototype Pollution	__proto__, constructor

⚡ Pro Features

Upgrade to Pro for advanced capabilities:

• Learning Mode - Auto-generate rules from traffic
• Hot-reload - Update rules without restart
• Sink-aware RASP - Context-aware protection
• Analytics Dashboard - Visualize threats

from contractshield import ContractShield

shield = ContractShield(
    license="CSH-XXXX-XXXX-XXXX",
    learning_mode=True  # Pro feature
)

Get your license at contractshield.dev/pricing

📚 Documentation

• Full Documentation
• API Reference
• Examples

🔗 Links

• Website
• GitHub
• npm packages (Node.js)
• PyPI (Python)

Security & Compliance

• OWASP ASVS Level 1 — Input validation (V5), API security (V13), access control (V4). Full compliance map →
• OWASP API Security Top 10 — Protection against API1 (BOLA), API6 (Mass Assignment), API7 (SSRF), API8 (Injection)
• CWE Coverage — CWE-22, CWE-78, CWE-89, CWE-639, CWE-915, CWE-918, CWE-943, CWE-1321

📄 License

Apache 2.0 - See LICENSE

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🇨🇭 Made in Switzerland