Asymmetric JWT Signing using AWS KMS

How to sign your JWT tokens without exposing your private key using AWS KMS

TL;DR

Node.js implementation using an asymmetric encryption key stored on AWS KMS to sign JWT tokens and verifying them using the public key. You can skip to the solution architecture.

JWT, Token Verification, and You

JWT tokens are an industry-standard, used mainly for user authentication.

It’s basically a JSON block with a signature attached, which allows you to verify that the content of the JSON was not tempered with. In the most common case, when your user logs in she gets a JWT token that is added to every request she sends, and this token is used to verify her identity.

How do you verify that your user is really who she claims to be? You take the signature from the JWT token and using your encryption key, you verify that it matches the content of the JSON. That’s called Token Verificaiton. The process of the creation of the signature in the first place is called Signing.

In order to sign and verify the token, you need an encryption method — either a symmetric or asymmetric (also called Public-Key encryption). In symmetric encryption, you’ll use the same key to sign and verify your token. In asymmetric encryption, you’ll use your private key to sign the token, and the public key to verify it.

What are we trying to solve?

Given a private key (either a symmetric or asymmetric), signing and verifying a string is quite simple, and there are multiple libraries for that.

However, to use most of these libraries you’ll need to have access to your secret key in order to sign the message (and if you’re using symmetric encryption, also to validate it). This is where things start to get messy: you need to keep your secret key somewhere that is reachable by your code, and at the same time, you’ll need to add a lot of protection layers on it to make sure no one gets his hands on it.

So what we want to solve is this: How to minimize the access to your private key and still be able to use it without too much fuss.

The first part of the solution is to use asymmetric encryption. In asymmetric you only need the private key to sign the token. The validation phase only requires the public key, and that can be, well, publicly available. This split will minimize the number of functions that need to access the private key.

The second part of the solution is to use AWS’s KMS service, which allows you to generate keys and use the KMS API to sign/validate messages without ever having direct access to the private key. Yes, that’s right: you’re generating a new private key, but you never get the private key. All you can do is ask AWS to use your key in order to sign or validate a token.

Let’s see how to do that.

#cloud #encryption #jwt #aws #development

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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

Asymmetric JWT Signing using AWS KMS

How to sign your JWT tokens without exposing your private key using AWS KMS

TL;DR

Node.js implementation using an asymmetric encryption key stored on AWS KMS to sign JWT tokens and verifying them using the public key. You can skip to the solution architecture.

JWT, Token Verification, and You

JWT tokens are an industry-standard, used mainly for user authentication.

It’s basically a JSON block with a signature attached, which allows you to verify that the content of the JSON was not tempered with. In the most common case, when your user logs in she gets a JWT token that is added to every request she sends, and this token is used to verify her identity.

How do you verify that your user is really who she claims to be? You take the signature from the JWT token and using your encryption key, you verify that it matches the content of the JSON. That’s called Token Verificaiton. The process of the creation of the signature in the first place is called Signing.

In order to sign and verify the token, you need an encryption method — either a symmetric or asymmetric (also called Public-Key encryption). In symmetric encryption, you’ll use the same key to sign and verify your token. In asymmetric encryption, you’ll use your private key to sign the token, and the public key to verify it.

What are we trying to solve?

Given a private key (either a symmetric or asymmetric), signing and verifying a string is quite simple, and there are multiple libraries for that.

However, to use most of these libraries you’ll need to have access to your secret key in order to sign the message (and if you’re using symmetric encryption, also to validate it). This is where things start to get messy: you need to keep your secret key somewhere that is reachable by your code, and at the same time, you’ll need to add a lot of protection layers on it to make sure no one gets his hands on it.

So what we want to solve is this: How to minimize the access to your private key and still be able to use it without too much fuss.

The first part of the solution is to use asymmetric encryption. In asymmetric you only need the private key to sign the token. The validation phase only requires the public key, and that can be, well, publicly available. This split will minimize the number of functions that need to access the private key.

The second part of the solution is to use AWS’s KMS service, which allows you to generate keys and use the KMS API to sign/validate messages without ever having direct access to the private key. Yes, that’s right: you’re generating a new private key, but you never get the private key. All you can do is ask AWS to use your key in order to sign or validate a token.

Let’s see how to do that.

#cloud #encryption #jwt #aws #development

AWS Cost Allocation Tags and Cost Reduction

Bob had just arrived in the office for his first day of work as the newly hired chief technical officer when he was called into a conference room by the president, Martha, who immediately introduced him to the head of accounting, Amanda. They exchanged pleasantries, and then Martha got right down to business:

“Bob, we have several teams here developing software applications on Amazon and our bill is very high. We think it’s unnecessarily high, and we’d like you to look into it and bring it under control.”

Martha placed a screenshot of the Amazon Web Services (AWS) billing report on the table and pointed to it.

“This is a problem for us: We don’t know what we’re spending this money on, and we need to see more detail.”

Amanda chimed in, “Bob, look, we have financial dimensions that we use for reporting purposes, and I can provide you with some guidance regarding some information we’d really like to see such that the reports that are ultimately produced mirror these dimensions — if you can do this, it would really help us internally.”

“Bob, we can’t stress how important this is right now. These projects are becoming very expensive for our business,” Martha reiterated.

“How many projects do we have?” Bob inquired.

“We have four projects in total: two in the aviation division and two in the energy division. If it matters, the aviation division has 75 developers and the energy division has 25 developers,” the CEO responded.

Bob understood the problem and responded, “I’ll see what I can do and have some ideas. I might not be able to give you retrospective insight, but going forward, we should be able to get a better idea of what’s going on and start to bring the cost down.”

The meeting ended with Bob heading to find his desk. Cost allocation tags should help us, he thought to himself as he looked for someone who might know where his office is.

#aws #aws cloud #node js #cost optimization #aws cli #well architected framework #aws cost report #cost control #aws cost #aws tags

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