How to use OpenSSL for SSL/TLS handshake on Debian

Using OpenSSL for SSL/TLS handshake on Debian, you can follow these steps:

1. Install OpenSSL

First, make sure that OpenSSL is already installed on your Debian system. If not installed, you can use the following command to install:

sudo apt update
sudo apt install openssl

2. Start the OpenSSL client

Start the OpenSSL client with the following command:

openssl s_client

3. Connect to the server

Use the -connect option to specify the server address and port to connect to. For example, connect to port 443 of www.example.com:

openssl s_client -connect www.example.com:443

4. Check the handshake process

The OpenSSL client displays the detailed process of the SSL/TLS handshake, including all communications between the client and the server.

5. Use a specific protocol version

If you want to use a specific SSL/TLS protocol version, you can use the options such as -tls1_2, -tls1_3. For example, use TLS 1.3:

openssl s_client -connect www.example.com:443 -tls1_3

6. Use a specific encryption suite

If you want to use a specific encryption suite, you can use the -cipher option. For example, use AES256-GCM-SHA384:

openssl s_client -connect www.example.com:443 -cipher AES256-GCM-SHA384

7. Save handshake data to file

If you want to save the handshake data to a file, you can use the redirect operator >:

openssl s_client -connect www.example.com:443 > handshake.log

8. Use certificate verification

If you want to verify the server's certificate, you can use the -verify_return_error option:

openssl s_client -connect www.example.com:443 -verify_return_error

9. Use a self-signed certificate

If you want to use a self-signed certificate for testing, you can specify the CA certificate file using the -CAfile option:

openssl s_client -connect www.example.com:443 -CAfile my_ca_cert.pem

10. Use client certificate

If you want to use client certificates for authentication, you can specify the client certificate and private key files using the -cert and -key options:

openssl s_client -connect www.example.com:443 -cert client_cert.pem -key client_key.pem

Through the above steps, you can use OpenSSL on Debian for SSL/TLS handshake and perform various configurations and tests as needed.

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