Let’s Encrypt SSL Certificate for Cisco AnyConnect VPN

Please refer to the steps to apply Let’s Encrypt SSL Certificate for Cisco AnyConnect VPN

Export the PFX from Windows

Select Encryption = TripleDES-SHA1

Convert the PFX to base64

openssl base64 -in aventislab.pfx -out aventislab.base64

#View the content of cert.base64
cat aventislab.base64

Import the Let’s Encrypt SSL Wildcard Certificate to Cisco ASAv

crypto ca import vpn.aventislab.com pkcs12 XXXXX (XXX - Password to open the pfx file)

Enter the base 64 encoded pkcs12.
End with the word "quit" on a line by itself:

PASTE ALL CONTENT FROM THE OUTPUT FROM CAT aventislab.base64

quit
INFO: Import PKCS12 operation completed successfully

Verify the Let’s Encrypt Cert is installed successfuly

sh crypto ca certificates

Certificate
  Status: Available
  Certificate Serial Number: 03bb65a8a4a4905b35144a112a61c6b3a69f
  Certificate Usage: General Purpose
  Public Key Type: RSA (2048 bits)
  Signature Algorithm: SHA256 with RSA Encryption
  Issuer Name:
    cn=Let's Encrypt Authority X3
    o=Let's Encrypt
    c=US
  Subject Name:
    cn=*.aventislab.com
  OCSP AIA:
    URL: http://ocsp.int-x3.letsencrypt.org
  Validity Date:
    start date: 14:11:27 MYT Mar 4 2020
    end   date: 14:11:27 MYT Jun 2 2020
  Storage: config
  Associated Trustpoints: vpn.aventislab.com

Assign the Let’s Encrypt Cert to Outside Interface

ssl trust-point vpn.aventislab.com outside

Go to https://vpn.aventistech.com to verify the Let’s Encrypt Certificate is installed successfully