【AWS】使用 API Gateway Authorizer 做使用者驗證 feat. Serverless

在 AWS 的 API gateway 上就有一個項目(Authorizer)是支援 Cognito 以及客制認證的方法，好處就是在進我們寫的 API 之前有個可以做身份確認的 Lambda Function 幫我們好前處理，而本篇則會介紹如何在 Serverless framework 上設定 API gateway 的 Authorizer 以及成功讓 API 回應，串接 Cognito 做使用部分就留給之後吧！

**👉 本篇的範例全都在 **GitHub

API Gateway - Authorizer

• 官方文件

擁有 Authorizer 的一個 Serverless 服務會長這樣:

User Request - [Authorizer] - API - Response user

好處除了前言所提到的前處理外，還有如果設定是 Edge 模式 (不是透過 region 從網路層傳) 的話其實在認證完後傳到 API 時速度是很快的。

以下就開始好好的介紹它 😆

實際的位置

如果在這邊設定覺得不知道在哪邊的話可以參考 - 純手動用法官方教學

中文的話左邊名為授權方，英文則是Authorizer

Serverless 實作

Yaml settings

原始如果串接 python WSGI 的話設定檔應該會長得如下:

functions:
  api:
    handler: wsgi_handler.handler
    events:
      - http: ANY /
      - http: ANY {proxy+}

設定 Authorizer Lambda function，先在跟 api 同層加上 Authorizer Lambda，指定 handler 為 handler 資料夾下的 authorizer.py 的 auth_handler function，並且設定 cors 為 true，避免呼叫 api 時被 AWS 擋下來無法使用。

接著在把 events 裡的兩個事件加上 authorizer 的 Function，名為 ResourceAuthorizer，改編過後入下:

functions:
  api:
    handler: wsgi_handler.handler
    events:
      - http:
          path: /
          method: ANY
          authorizer: ResourceAuthorizer
      - http:
          path: /{proxy+}
          method: ANY
          authorizer: ResourceAuthorizer
  ResourceAuthorizer:
    handler: handler/authorizer.auth_handler
    cors: true

#[object object] #serverless #function

What is GEEK

Buddha Community

How To Unite AWS KMS with Serverless Application Model (SAM)

The Basics

AWS KMS is a Key Management Service that let you create Cryptographic keys that you can use to encrypt and decrypt data and also other keys. You can read more about it here.

Important points about Keys

Please note that the customer master keys(CMK) generated can only be used to encrypt small amount of data like passwords, RSA key. You can use AWS KMS CMKs to generate, encrypt, and decrypt data keys. However, AWS KMS does not store, manage, or track your data keys, or perform cryptographic operations with data keys.

You must use and manage data keys outside of AWS KMS. KMS API uses AWS KMS CMK in the encryption operations and they cannot accept more than 4 KB (4096 bytes) of data. To encrypt application data, use the server-side encryption features of an AWS service, or a client-side encryption library, such as the AWS Encryption SDK or the Amazon S3 encryption client.

Scenario

We want to create signup and login forms for a website.

Passwords should be encrypted and stored in DynamoDB database.

What do we need?

1. KMS key to encrypt and decrypt data
2. DynamoDB table to store password.
3. Lambda functions & APIs to process Login and Sign up forms.
4. Sign up/ Login forms in HTML.

Lets Implement it as Serverless Application Model (SAM)!

Lets first create the Key that we will use to encrypt and decrypt password.

KmsKey:
    Type: AWS::KMS::Key
    Properties: 
      Description: CMK for encrypting and decrypting
      KeyPolicy:
        Version: '2012-10-17'
        Id: key-default-1
        Statement:
        - Sid: Enable IAM User Permissions
          Effect: Allow
          Principal:
            AWS: !Sub arn:aws:iam::${AWS::AccountId}:root
          Action: kms:*
          Resource: '*'
        - Sid: Allow administration of the key
          Effect: Allow
          Principal:
            AWS: !Sub arn:aws:iam::${AWS::AccountId}:user/${KeyAdmin}
          Action:
          - kms:Create*
          - kms:Describe*
          - kms:Enable*
          - kms:List*
          - kms:Put*
          - kms:Update*
          - kms:Revoke*
          - kms:Disable*
          - kms:Get*
          - kms:Delete*
          - kms:ScheduleKeyDeletion
          - kms:CancelKeyDeletion
          Resource: '*'
        - Sid: Allow use of the key
          Effect: Allow
          Principal:
            AWS: !Sub arn:aws:iam::${AWS::AccountId}:user/${KeyUser}
          Action:
          - kms:DescribeKey
          - kms:Encrypt
          - kms:Decrypt
          - kms:ReEncrypt*
          - kms:GenerateDataKey
          - kms:GenerateDataKeyWithoutPlaintext
          Resource: '*'

The important thing in above snippet is the KeyPolicy. KMS requires a Key Administrator and Key User. As a best practice your Key Administrator and Key User should be 2 separate user in your Organisation. We are allowing all permissions to the root users.

So if your key Administrator leaves the organisation, the root user will be able to delete this key. As you can see **KeyAdmin **can manage the key but not use it and KeyUser can only use the key. ${KeyAdmin} and **${KeyUser} **are parameters in the SAM template.

You would be asked to provide values for these parameters during SAM Deploy.

#aws #serverless #aws-sam #aws-key-management-service #aws-certification #aws-api-gateway #tutorial-for-beginners #aws-blogs

Public ASX100 APIs: The Essential List

We’ve conducted some initial research into the public APIs of the ASX100 because we regularly have conversations about what others are doing with their APIs and what best practices look like. Being able to point to good local examples and explain what is happening in Australia is a key part of this conversation.

Method

The method used for this initial research was to obtain a list of the ASX100 (as of 18 September 2020). Then work through each company looking at the following:

1. Whether the company had a public API: this was found by googling “[company name] API” and “[company name] API developer” and “[company name] developer portal”. Sometimes the company’s website was navigated or searched.
2. Some data points about the API were noted, such as the URL of the portal/documentation and the method they used to publish the API (portal, documentation, web page).
3. Observations were recorded that piqued the interest of the researchers (you will find these below).
4. Other notes were made to support future research.
5. You will find a summary of the data in the infographic below.

Data

With regards to how the APIs are shared:

• Documentation is where just the Swagger/OpenAPI docs are hosted somewhere. e.g. https://api.linkgroup.com/member/docs/index
• Portal is where an interactive portal has been developed. e.g. https://dev.telstra.com/
• The web page is where the company has a single page that isn’t interactive explaining their Public APIs. e.g. https://www.bendigoadelaide.com.au/banking-products-api.asp

#api #api-development #api-analytics #apis #api-integration #api-testing #api-security #api-gateway

Serverless Express – Easy APIs On AWS Lambda & AWS HTTP API

TLDR - Take existing Express.js apps and host them easily onto cheap, auto-scaling, serverless infrastructure on AWS Lambda and AWS HTTP API with Serverless Express. It’s packed loads of production-ready features, like custom domains, SSL certificates, canary deployments, and costs ~$0.000003 per request.

If you simply want to host a common Express.js Node.js application, have it auto-scale to billions of requests, and charge you only when it’s used, we have something special for you…

Announcing Serverless Express, a Serverless Framework offering enabling you to easily host and manage Express.js applications on AWS Lambda and the new AWS HTTP API, which is 60% faster and 71% cheaper than their initial API Gateway product.

Serverless Expess is a pure Express.js experience and it’s perfect for those that want to focus on apps, not infrastructure complexity.

Here are the highlights:

• Easy, Safe, Performance - Includes the optimal infrastructure pattern for cost, performance & scale.
• Never Pay For Idle - No API requests? No cost. Averages ~$0.000003 per request.
• Zero Configuration - Add your Express app, then deploy (advanced config options are available).
• Fast Deployments - Deploy changes to the cloud in seconds.
• Real-time Logging - Rapidly develop on the cloud w/ real-time logs and errors in the CLI.
• Canary Deployments - Deploy your app gradually to a subset of your traffic.
• Custom Domain + SSL - Auto-configure a custom domain w/ a free AWS ACM SSL certificate.
• Team Collaboration - Collaborate with your teamates with shared state and outputs.

Here is how to get started and deliver a Serverless Express.js based API with a custom domain, free SSL certificate and much more! You can also check out our Serverless Fullstack Application boilerplate, which includes Serverless Express in a real-world example that features a database, website using React and more.

Set-Up

Serverless Express is a Serverless Framework Component (i.e premium experiences for popular serverless use-cases) and you’ll need to install Node.js and the Serverless Framework CLI to use it.

Install Node.js here.

Then run this command to install Serverless Framework.

npm i -g serverless

Next, install the Serverless Express template:

serverless create --template-url https://github.com/serverless/components/tree/master/templates/express

Lastly, Serverless Express deploys onto your own Amazon Web Services account, so you’ll need Access Keys to an AWS account you own. Follow this guide to create those.

After you have created AWS Access Keys you can add them directly to an .env file, or reference an AWS Profile in a .env file, within the root of the template you installed.

AWS_ACCESS_KEY_ID=123456789
AWS_SECRET_ACCESS_KEY=123456789

You can also reference an AWS Profile in a .env file like this.

AWS_PROFILE=default

If you don’t include a .env file, the Serverless Framework will automatically look for a default AWS Profile in the root folder of your machine.

Also, Serverless Framework has a built-in stages concept. If you change the stage it will deploy a totally separate copy of your serverless application.

# serverless.yml
component: express@1.0.8
  name: express-api
  stage: prod

Even better, you can use different .env files for each stage by simply using this convention:

.env # all stages
.env.dev # "dev" stage
.env.prod # "prod" stage

One last—often overlooked—step is to install the Express.js dependency, by running npm i in the template.

#serverless #apis #aws #aws lambda #aws http api

Top 10 API Security Threats Every API Team Should Know

As more and more data is exposed via APIs either as API-first companies or for the explosion of single page apps/JAMStack, API security can no longer be an afterthought. The hard part about APIs is that it provides direct access to large amounts of data while bypassing browser precautions. Instead of worrying about SQL injection and XSS issues, you should be concerned about the bad actor who was able to paginate through all your customer records and their data.

Typical prevention mechanisms like Captchas and browser fingerprinting won’t work since APIs by design need to handle a very large number of API accesses even by a single customer. So where do you start? The first thing is to put yourself in the shoes of a hacker and then instrument your APIs to detect and block common attacks along with unknown unknowns for zero-day exploits. Some of these are on the OWASP Security API list, but not all.

Insecure pagination and resource limits

Most APIs provide access to resources that are lists of entities such as /users or /widgets. A client such as a browser would typically filter and paginate through this list to limit the number items returned to a client like so:

First Call: GET /items?skip=0&take=10 
Second Call: GET /items?skip=10&take=10

However, if that entity has any PII or other information, then a hacker could scrape that endpoint to get a dump of all entities in your database. This could be most dangerous if those entities accidently exposed PII or other sensitive information, but could also be dangerous in providing competitors or others with adoption and usage stats for your business or provide scammers with a way to get large email lists. See how Venmo data was scraped

A naive protection mechanism would be to check the take count and throw an error if greater than 100 or 1000. The problem with this is two-fold:

1. For data APIs, legitimate customers may need to fetch and sync a large number of records such as via cron jobs. Artificially small pagination limits can force your API to be very chatty decreasing overall throughput. Max limits are to ensure memory and scalability requirements are met (and prevent certain DDoS attacks), not to guarantee security.
2. This offers zero protection to a hacker that writes a simple script that sleeps a random delay between repeated accesses.

skip = 0
while True:    response = requests.post('https://api.acmeinc.com/widgets?take=10&skip=' + skip),                      headers={'Authorization': 'Bearer' + ' ' + sys.argv[1]})    print("Fetched 10 items")    sleep(randint(100,1000))    skip += 10

How to secure against pagination attacks

To secure against pagination attacks, you should track how many items of a single resource are accessed within a certain time period for each user or API key rather than just at the request level. By tracking API resource access at the user level, you can block a user or API key once they hit a threshold such as “touched 1,000,000 items in a one hour period”. This is dependent on your API use case and can even be dependent on their subscription with you. Like a Captcha, this can slow down the speed that a hacker can exploit your API, like a Captcha if they have to create a new user account manually to create a new API key.

Insecure API key generation

Most APIs are protected by some sort of API key or JWT (JSON Web Token). This provides a natural way to track and protect your API as API security tools can detect abnormal API behavior and block access to an API key automatically. However, hackers will want to outsmart these mechanisms by generating and using a large pool of API keys from a large number of users just like a web hacker would use a large pool of IP addresses to circumvent DDoS protection.

How to secure against API key pools

The easiest way to secure against these types of attacks is by requiring a human to sign up for your service and generate API keys. Bot traffic can be prevented with things like Captcha and 2-Factor Authentication. Unless there is a legitimate business case, new users who sign up for your service should not have the ability to generate API keys programmatically. Instead, only trusted customers should have the ability to generate API keys programmatically. Go one step further and ensure any anomaly detection for abnormal behavior is done at the user and account level, not just for each API key.

Accidental key exposure

APIs are used in a way that increases the probability credentials are leaked:

1. APIs are expected to be accessed over indefinite time periods, which increases the probability that a hacker obtains a valid API key that’s not expired. You save that API key in a server environment variable and forget about it. This is a drastic contrast to a user logging into an interactive website where the session expires after a short duration.
2. The consumer of an API has direct access to the credentials such as when debugging via Postman or CURL. It only takes a single developer to accidently copy/pastes the CURL command containing the API key into a public forum like in GitHub Issues or Stack Overflow.
3. API keys are usually bearer tokens without requiring any other identifying information. APIs cannot leverage things like one-time use tokens or 2-factor authentication.

If a key is exposed due to user error, one may think you as the API provider has any blame. However, security is all about reducing surface area and risk. Treat your customer data as if it’s your own and help them by adding guards that prevent accidental key exposure.

How to prevent accidental key exposure

The easiest way to prevent key exposure is by leveraging two tokens rather than one. A refresh token is stored as an environment variable and can only be used to generate short lived access tokens. Unlike the refresh token, these short lived tokens can access the resources, but are time limited such as in hours or days.

The customer will store the refresh token with other API keys. Then your SDK will generate access tokens on SDK init or when the last access token expires. If a CURL command gets pasted into a GitHub issue, then a hacker would need to use it within hours reducing the attack vector (unless it was the actual refresh token which is low probability)

Exposure to DDoS attacks

APIs open up entirely new business models where customers can access your API platform programmatically. However, this can make DDoS protection tricky. Most DDoS protection is designed to absorb and reject a large number of requests from bad actors during DDoS attacks but still need to let the good ones through. This requires fingerprinting the HTTP requests to check against what looks like bot traffic. This is much harder for API products as all traffic looks like bot traffic and is not coming from a browser where things like cookies are present.

Stopping DDoS attacks

The magical part about APIs is almost every access requires an API Key. If a request doesn’t have an API key, you can automatically reject it which is lightweight on your servers (Ensure authentication is short circuited very early before later middleware like request JSON parsing). So then how do you handle authenticated requests? The easiest is to leverage rate limit counters for each API key such as to handle X requests per minute and reject those above the threshold with a 429 HTTP response. There are a variety of algorithms to do this such as leaky bucket and fixed window counters.

Incorrect server security

APIs are no different than web servers when it comes to good server hygiene. Data can be leaked due to misconfigured SSL certificate or allowing non-HTTPS traffic. For modern applications, there is very little reason to accept non-HTTPS requests, but a customer could mistakenly issue a non HTTP request from their application or CURL exposing the API key. APIs do not have the protection of a browser so things like HSTS or redirect to HTTPS offer no protection.

How to ensure proper SSL

Test your SSL implementation over at Qualys SSL Test or similar tool. You should also block all non-HTTP requests which can be done within your load balancer. You should also remove any HTTP headers scrub any error messages that leak implementation details. If your API is used only by your own apps or can only be accessed server-side, then review Authoritative guide to Cross-Origin Resource Sharing for REST APIs

Incorrect caching headers

APIs provide access to dynamic data that’s scoped to each API key. Any caching implementation should have the ability to scope to an API key to prevent cross-pollution. Even if you don’t cache anything in your infrastructure, you could expose your customers to security holes. If a customer with a proxy server was using multiple API keys such as one for development and one for production, then they could see cross-pollinated data.

#api management #api security #api best practices #api providers #security analytics #api management policies #api access tokens #api access #api security risks #api access keys

Serverless Proxy with AWS API Gateway and AWS Lambda

It’s sometimes difficult to communicate between public and private subnet in AWS.

We will see how we can easily do that with the help of API Gateway and AWS Lambda.

Use case example

Example 1

It’s sometimes necessary to have a Github repository communicating with a private EC2 instance.

But when an instance is private, it can be really complicated without impacting the security of the instance.

#aws-lambda #serverless #api-gateway #aws