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ACM Private Certificate authority - Private certs for your webserver

This workshop demonstrates how ACM Private Certificate authority(PCA) can be created and made operational. It also helps you learn about how ACM PCA can be used to generate private certificates for your devices or web servers. In this usecase you will generate a CSR(certificate signing request) for your device or server and then get it signed by the AWS Certificate manager private CA

Let's look at some concepts :



Let's do some private cert generaton with AWS Certificate Manager(ACM) private certificate authority(PCA) :

Open the Cloud9 IDE environment called workshop-environment and navigate to the data-protection/usecase-4 directory. Follow the instructions below:

1. Run the python module named usecase-4-step-1.py

  • First you will see Pending DynamoDB table creation for storing shared variables printed on the runner window pane below
  • Wait for about 45 seconds
  • You should see shared_variables_crypto_builders DynamoDB table created printed

This module will create a DynamoDB table called shared_variables_crypto_builders . The primary purpose of this table is to share variables across the different python modules that we will run in this usecase.

2. Run the python module named usecase-4-step-2.py

  • This module creates a ACM private certificate authority with the common name acmpcausecase4.subordinate
  • This private certificate authority will publish certificate revocation lists within a S3 bucket whose name starts with builder-acm-pca-usecase-4-bucket-pca-crl
  • You should see the following printed in the runner window pane
    • Private CA has been created
    • Please generate the CSR and get it signed by your organizations's root cert
    • Success : The ARN of the subordinate private certificate authority is : arn:aws:acm-pca:::certificate-authority/57943599-30d2-8723-1234-1cb4b7d81128
  • In the AWS console browse to the AWS Certificate Manager service(ACM) . Under Private CA's you will see the private CA created and the status should show "Pending Certificate"


Some questions to think about :

  • Why is the status of the private CA showing "Pending Certificate" ?
  • Is the private certificate authority that's created a root CA or a subordinate CA ?
  • What's the purpose of the S3 bucket storing certificate revocation lists ?

3. Run the python module named usecase-4-step-3.py

  • This module creates a self signed root certificate with the common name rootca-builder
  • You can see in the code that the private key associated with the self signed cert is stored in an encrypted DynamoDB table. This is purely for demonstration purposes. In your organization you should store it in an HSM or a secure vault
  • You should see the following printed in the runner window pane below
  • Success - Self signed certificate file self-signed-cert.pem created"
  • This self signed certificate will be used in the certificate chain of trust


Some questions to think about :

  • In your organization would you use the root cert to sign subordinate CA's ?
  • Why is it necessary to store the private keys of root certs in an HSM ?
  • What would happen if the private key of the root cert gets compromised or stolen ?

4. Run the python module named usecase-4-step-4.py

  • This module gets a Certificate signing request(CSR) for the private certifiate authority with common name acmpcausecas4.subordinate that was created in Step 2
  • The certificate signing request is signed using the self signed certificate and it's private key that was created in Step 3
  • The signed cert is stored in a pem file called signed_subordinate_ca_cert.pem
  • You should see the following printed in the runner window pane below
  • Successfully created signed subordinate CA pem file signed_subordinate_ca_cert.pem

5. Run the python module named usecase-4-step-5.py

  • This module imports the subordinate CA signed certificate signed_subordinate_ca_cert.pem and the certificate chain of trust into AWS Certificate Manager(ACM)
  • The certificate chain contains the self signed or root CA certificate that we created in Step 3
  • After this operation the subordinate private certificate authority(CA) changes status to ACTIVE.
  • Browse to the ACM service within the AWS console and you should see the status of the subordiate CA with common name acmpcausecase4.subordinate as ACTIVE as shown below
  • We are at a point where the subordinate private certificate authority(PCA) can issue private certificates for any endpoint, device or server
  • You should see the following printed in the runner window pane below
  • Successfully imported signed cert and certificate chain into ACM


6. Run the python module named usecase-4-step-6.py

  • This module takes about 2 minutes to complete
  • This module creates a CSR for a webserver endpoint with common name 127.0.0.1 and the CSR is then passed to the issue_certificate API call which sends the CSR to AWS Certificate Manager and is signed by the subordinate private certificate authority
  • The signed webserver endpoint certificate pem file is called "webserver_cert.pem"
  • The issue_certificate API calls also returns the certificate chain of trust and the pem file that stores the certificate chain of trust is called "webserver_cert_chain.pem"
  • You should see the following printed in the runner window pane below
    • Successfully created server certificate webserver_cert.pem for the flask web server
    • Successfully created chain of trust webserver_cert_chain.pem for the flask web server

7. Run the python module named usecase-4-step-7.py

  • This module creates a python flask web server
  • The webserver is running within the Cloud9 environment and is exposed through the following URL https://127.0.0.1:5000/ on port 5000
  • You should see the following printed in the runner window pane below
  • Running on https://127.0.0.1:5000/
  • For the next steps this webserver needs to keep running. So please don't kill the runner window pane tab

8. Run the python module named usecase-4-step-8.py

  • This module uses the below curl command to do a HTTP GET on the flask webserver created in Step 7

curl --verbose -X GET https://127.0.0.1:5000/

  • We are using the curl command to simulate a HTTPS web client

  • Since the curl commmand does not supply the certificate trust chain as a parameter the HTTPS connection is going to complain that the server certificate is not recognized. You will see the following printed in the runner window pane below if you look through the printed log

curl: (60) Peer's Certificate issuer is not recognized

Certificate is not trusted - cannot validate server certificate

Some questions to think about :

  • Why was the server certificate not recognized by the curl command ?

9. Run the python module named usecase-4-step-9.py

  • This module uses curl to do a HTTPS GET on the flask webserver created in Step 7 using the following command :

curl --verbose --cacert 'webserver_cert_chain.pem' -X GET https://127.0.0.1:5000/

  • Since the curl command has the chain of trust pem file as a parameter the flask webserver certificate is successfully authenticated and you should see the following printed in the runner window pane.

Hello World!

Certificate is trusted and is valid

10. Run the python module named usecase-4-step-10-cleanup.py

  • This module cleans up all the resources that were created as part of this usecase
  • Please make sure that you run this cleanup script. Otherwise you will continue accruing charges for the ACM private certificate authority that was created during this usecase