Mutual TLS authentication - Demo

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For this demo, we are going to need a TLS Certificate that is going to be issued just for testing purposes.

Click on "Generate Certficate" which will return the contents for both private-key.pem and certificate.crt. Save them in your local computer.

Certificate details:

• Name: John Doe
• Email: john.doe@exampleloadbalancer.com

Generate Certificate

Mutual TLS verify mode

Step 1: Lets first send a request to ALB without a client certficate and we will notice TLS handshake fails.

Step 2: Now, after downloading the certificate and private key, we will test again providing them in the curl command.

In the example above, the mTLS handshake happens successfully amd ALB sends the client certficate information to the target using following HTTP headers:

Header	Description
X-Amzn-Mtls-Clientcert-Serial-Number	A hexadecimal representation of the leaf certificate serial number.
X-Amzn-Mtls-Clientcert-Issuer	An RFC2253 string representation of the issuer's distinguished name (DN).
X-Amzn-Mtls-Clientcert-Subject	An RFC2253 string representation of the subject's distinguished name (DN).
X-Amzn-Mtls-Clientcert-Validity	An ISO8601 format of the notBefore and notAfter date.
X-Amzn-Mtls-Clientcert-Leaf	URL-encoded PEM format of the leaf certificate, with +=/ as safe characters.

Mutual TLS passthrough

When you use mutual TLS passthrough mode, ALB sends the whole client certificate chain to the target using HTTP headers. Then, by using the client certificate chain, you can implement corresponding authentication and authorization logic in your application.

In the example above, the mTLS handshake happens successfully amd ALB sends the entrire client certficate chain information to the target using following HTTP header:

Header	Description
X-Amzn-Mtls-Clientcert	URL-encoded PEM format of the entire client certificate chain presented in the connection, with +=/ as safe characters.