# Security and API

* Defense on depth
* Best Practices for web servers
  + switch off unnecessary funtionality
  + limit secure remote access
  + use accounts with limited privileges
  + segregate development, testing and live environment
  + segregate data
  + secrity patches
  + monitor and audit servers and logs
  + use security tools
* Top 10 Application security risks
  + Injection - 
  + Broken authentication - compromised passwords
  + sensitive data exposure
  + xxe
  + broken acess control
  + security misconfiguration

[Equifax case study](https://www.csoonline.com/article/3444488/equifax-data-breach-faq-what-happened-who-was-affected-what-was-the-impact.html)
* security patches
* broken authentication
* broken access control
* security misconfiguration
* single point of failure
* lack of management commitment

## Security od Data in motion
* HTTPS / FTPS
* Type of SSL Certificates
  + Signed by a Cerficate Authority (CA)
  + Self-signed certificates (less trusted. For testing)
  
  + self sigend
  ```
  $ openssl genrsa -out key.pem
  $ openssl req -new -key key.pem -out csr.pem
  $ openssl x509 -req -days 9999 -in csr.pem -signkey key.pem -out cert.pem
  $ rm csr.pem
  ```

  ```Javascript

  ```
* role based access control

 ## Security date at rest
 * encrypt
   + sensitive files
   + storage drive
   + password
* security of username and password 

## Regulation and Standards
* [international](https://www.pcisecuritystandards.org/)
* [Singapore](https://www.mas.gov.sg/regulation/guidelines/technology-risk-management-guidelines)
* [Personal Data Protection Act](https://www.pdpc.gov.sg/Overview-of-PDPA/The-Legislation/Personal-Data-Protection-Act)
* [FintTech Service](https://singaporefintech.org/sfa-launches-digital-self-assessment-framework-to-fast-track-fintech-firms-partnerships-with-financial-institutions/)

## API Security
* Basic Authentication
* API key
* Bearer token
* JSON Web Token (JWT)

## SQL Injection attack

* sending body `{ id = "5 or 1=1" }`, will return all records. Thus, data leak
* need strong validation of inputs

```javascript
// GET route for /user/id query
// with body = { "id": 2 }
app.get("/user/id", (request, response) => {
    console.log(request.body);
    // !!! validation example !!!
    if (request.body.id === null 
        || Number.isNaN(request.body.id)
        || !Number.isInteger(request.body.id)) {
        response.send("Some id error occur");
        return;
    }
    //
    connection.query(`SELECT * FROM users WHERE user_id = ${request.body.id}`, 
    (err, result) => {
        if (err) {
            response.send("Some id error occur");
        }
        else {
            response.send(result);
        }    
    });
});

```

## Code organisation & management
* folder tree
  + \server.js
  + \database.js
  + \routes  => store all routes
  + \routes\customer.js
  + \routes\seller.js
    
* modularise into individual module file
  + server.js : setup server listen and route linkage
  ```javascript
  const express = require("express");
  const bodyParser = require("body-parser");
  
  const CustomerRouter = require("./routes/customer");
  const SellerRouter = require("./routes/seller");
  
  let app = express();  //uri mapper
  app.use(bodyParser.json());
  
  app.use("/customer", CustomerRouter);
  app.use("/seller", SellerRouter);
  
  app.listen(3000);
  ```
  + database.js : database connection
  ```javascript
  const mysql = require("mysql");
  
  let params = {
    host: "localhost",
    user: "root",
    password: "root",
    database: "sales",
  };
  
  mysqlConnection = mysql.createConnection(params);
  
  mysqlConnection.connect((err) => {
    if (err) {
      console.log("Failed to Connect");
    } else {
      console.log("Connection successful");
    }
  });
  
  module.exports = mysqlConnection;  
  ```
  + customer.js : customer apis
  ```javascript
  const express = require("express");
  const connection = require("../database");  // import database connection
  
  CustomerRouter = express.Router();
  
  // localhost:3000/customer/
  CustomerRouter.get("/", (req, res) => {
    connection.query("select * from customer", (err, rows) => {
      if (err) {
        console.log(err);
        res.send("Some error occurred");
      } else {
        res.send(rows);
      }
    });
  });
  
  // localhost:3000/customer/name/Zixuan
  CustomerRouter.get("/name/:value", (req, res) => {
    connection.query(
      `select * from customer where customer_name = '${req.params.value}'`,
      (err, rows) => {
        if (err) {
          console.log(err);
          res.send("Some error occurred");
        } else {
          res.send(rows);
        }
      }
    );
  });
  
  // localhost:3000/customer/id/10
  CustomerRouter.delete("/id/:value", (req, res) => {
    connection.query(
      `delete from customer where customer_id = ${req.params.value}`,
      (err, rows) => {
        if (err) {
          console.log(err);
          res.send("Some error occurred");
        } else {
          res.send("Deleted Successfully");
        }
      }
    );
  });
  
  module.exports = CustomerRouter;
  ```
  + seller.js : seller apis
  ```javascript
  const express = require("express");
  const connection = require("../database");
  
  SellerRouter = express.Router();
  
  // localhost:3000/seller/
  SellerRouter.post("/", (req, res) => {
    connection.query(
      `insert into seller (seller_name, seller_wallet) values ('${req.body.  name}',${req.body.wallet})`,
      (err, rows) => {
        if (err) {
          console.log(err);
          res.send("Some error occurred.");
        } else {
          res.send("Saved Successfully.");
        }
      }
    );
  });
  
  module.exports = SellerRouter;
  ```
* sample client fetch
```javascript
const fetch = require("node-fetch");

fetch("http://localhost:3000/customer/name/Zixuan", {
  method: "get",
  //   body: JSON.stringify(
  //     (body = {
  //       name: "dixant",
  //       email: "mittal",
  //     })
  //   ),
  headers: { "Content-Type": "application/json" },
})
  .then((res) => res.json())
  .then((json) => console.log(json));
```

* API key

```javascript

connection.query(
  `SELECT * FROM client WHERE client_id = ${request.body.client_id} AND client_key = '${request.body.client_key}'`,
  (err, result) => {
    if (ok)
      serve the request...
      ...
  }
)
```

* Backend server
  + formatting conflicting
  + flexibility with separation
  + separation on client-ui and backend