LetsEncrypt + ASA 5500, automated certificate renewal script.

So there is no API for the ASA 5500 series, and you probably do not have an X series for Firepower firewall in your lab.  You could use the ASAv and the github script out there, but then you need licensing.  Due to this, I have created a fairly lengthy script that creates and renews your certs from Let's Encrypt.  You will need a Linux box, a web server running on it, root access (you have to run this with sudo at least), Python 3.x and paramiko-expect installed.  Most values are at the top to be changed.  It assumes you will use SSL-Trustpoint as the name, you can modify as you like.  This script is BSD licensing.  You may want to change the prompts and all fields at the top as needed.

So install Python 3.x (64 bit if needed), ensure your Path environment variable is set properly, then you will need to pip install paramiko-expect

This should work on all platforms!

This will also create a log file in /var/log/letsRenewASA.log as it is meant to be set up as a Cron job so that you no longer have to manually grab new certificates.

This script does NOT configure your VPN for you, you still have to do that yourself.

You can download it directly here:
https://drive.google.com/file/d/0Bz9hJ3nepc_7bUwxVUUxRG50OEU/view?usp=sharing

#!/usr/bin/python
#Copyright 2017 Tim Nelson
#
#Redistribution and use in source and binary forms, with or without modification,
#are permitted provided that the following conditions are met:
#
#1. Redistributions of source code must retain the above copyright notice,
#this list of conditions and the following disclaimer.
#
#2. Redistributions in binary form must reproduce the above copyright notice,
#this list of conditions and the following disclaimer in the documentation and/or
#other materials provided with the distribution.
#
#THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
#AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
#WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
#IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
#INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
#NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
#PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
#WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
#ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
#POSSIBILITY OF SUCH DAMAGE.


import paramiko, re, time
from paramiko_expect import SSHClientInteraction

asaHost = '<HOSTNAME OR IP OF ASA>'

hostname = '<ACTUAL HOSTNAME FIELD ON ASA>'
localHost = '127.0.0.1'
asaUser = '<ASAUSERNAME>'
asaPassword = '<ASAPASSWORD>'
enablePassword = '<ENABLEPASSWORD>'
localUser = '<LINUXUSERNAME>'
localPassword = '<LINUXPASSWORD>'
csrFilename = 'asa.csr'
logFile = '/var/log/letsRenewASA.log'
fqdn = '<YOUR FQDN>'
certString = 'CN=' + (fqdn) + ',OU=<YOUROU>,O=<ORGANIZATION>,C=US,St=<ST>,L=<CITY>'
letsEncrypt = '/usr/bin/letsencrypt/letsencrypt-auto'
email = '<YOUR ADMIN EMAIL>'
webRoot = '<ROOT DIRECTORY OF WEBSERVER>'

localPrompt = localUser + '@.*'
prompt0 = (hostname) + '> '
prompt1 = (hostname) + '# '
authPrompt = 'Password: '
confPrompt = '.*\)\# '
keyPrompt = '.*\[yes\/no\]: '
accept = 'Continue \(y\/n\)\?'
logFile = open(logFile ,'a+')
csrFile = open(csrFilename ,'w')
i = 10

logFile.write('\n\nStarting to Renew!\n')

client = paramiko.SSHClient()
client.load_system_host_keys()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect(hostname=asaHost, username=asaUser, password=asaPassword)
interact = SSHClientInteraction(client, timeout=120, display=False)
try:
        interact.expect(prompt0)
except Exception:
        logFile.write('could not read prompt0\n')
interact.send('en')
try:
        interact.expect(authPrompt)
except Exception:
        logFile.write('could not read authPrompt\n')
interact.send(enablePassword)
try:
        interact.expect(prompt1)
except Exception:
        logFile.write('could not read prompt1\n')
interact.send('conf t')
try:
        interact.expect(confPrompt)
except Exception:
        logFile.write('could not read confPrompt\n')
interact.send('crypto key generate rsa label SSL-Keypair modulus 2048')
interact.expect([keyPrompt, confPrompt])
if interact.last_match == keyPrompt:
        interact.send('n')
interact.send('crypto ca authenticate SSL-Trustpoint')
interact.expect(['.*delete.*', '.*unknown.*'])
if interact.last_match == '.*delete.*':
        interact.send('no crypto ca trustpoint SSL-Trustpoint')
        interact.expect([keyPrompt, '.*in use.*'])
        if interact.last_match == '.*in use.*':
                i = 0
                interact.send('no crypto ikev2 remote-access trustpoint SSL-Trustpoint')
                interact.expect(confPrompt)
                interact.send('no crypto ca trustpoint SSL-Trustpoint')
                interact.expect(keyPrompt)
        interact.send('y')
interact.send('crypto ca trustpoint SSL-Trustpoint')
interact.expect(confPrompt)
interact.send('enrollment terminal')
interact.expect(confPrompt)
interact.send('fqdn ' + (fqdn))
interact.expect(confPrompt)
interact.send('subject-name ' + (certString))
interact.expect(confPrompt)
interact.send('keypair SSL-Keypair')
interact.expect(confPrompt)
interact.send('exit')
interact.expect(confPrompt)
interact.send('crypto ca enroll SSL-Trustpoint')
interact.expect(keyPrompt)
interact.send('y')
interact.expect(keyPrompt)
interact.send('n')
interact.expect(keyPrompt)
interact.send('y')
interact.expect(keyPrompt)
cert = interact.current_output_clean
cert = re.sub('Certificate Request follows:\n', '', cert)
cert = re.sub('\x00', '', cert)
interact.send('n')
interact.expect(confPrompt)
interact.send('exit')
interact.expect(prompt1)
interact.send('exit')
csrFile.write(cert)
csrFile.close()
client.connect(hostname=localHost, username=localUser, password=localPassword)
interact = SSHClientInteraction(client, timeout=120, display=False)
try:
        interact.expect(localPrompt)
except Exception:
        logFile.write('could not read localPrompt\n')
        print('could not read localPrompt')
interact.send(
 (letsEncrypt) +
 ' certonly --authenticator manual --server https://acme-v01.api.letsencrypt.org/directory --text --email '+
 (email) + ' --csr ' + (csrFilename)
 )
interact.expect('.*o: ')
interact.send('y')
interact.expect('Press Enter to Continue')
cleanOutput = interact.current_output_clean
challengeFile = cleanOutput.splitlines()[8]
challengeFile = re.sub('http://' + (fqdn) + '/', (webRoot), challengeFile)
challengeContent = cleanOutput.splitlines()[4]
logFile.write('Created challengeFile at ' + (challengeFile) + '\n')
challengeFile = open(challengeFile, 'w')
challengeFile.write(challengeContent)
logFile.write('Put the following content: ' + (challengeContent) + ' in challengeFile\n')
challengeFile.close()
interact.send('\r')
interact.expect(localPrompt)
cleanOutput = interact.current_output_clean
interact.send('exit')
certPath = (cleanOutput.splitlines()[4])
certPath = re.sub('Server issued certificate; certificate written to ', '', certPath)
logFile.write('Grabbed the certificate from: ' + (certPath) + '\n')
chainPath = (cleanOutput.splitlines()[10])
chainPath = re.sub('\s+', '', chainPath)
chainFile = open(chainPath, 'r')
certFile = open(certPath, 'r')
caFile = chainFile.read()
caCert = re.findall(
 r'-----BEGIN CERTIFICATE-----(.*?)-----END CERTIFICATE-----',
 caFile, re.DOTALL
 )
caCert = '-----BEGIN CERTIFICATE-----' + (caCert[1]) + '-----END CERTIFICATE-----'
chainFile.close()
logFile.write('Grabbed the certificate chain from: ' + (chainPath) + '\n')
client.connect(hostname=asaHost, username=asaUser, password=asaPassword)
interact = SSHClientInteraction(client, timeout=120, display=False)
try:
        interact.expect(prompt0)
except Exception:
        logFile.write('could not read prompt0\n')
interact.send('en')
try:
        interact.expect(authPrompt)
except Exception:
        logFile.write('could not read authPrompt\n')
interact.send(enablePassword)
try:
        interact.expect(prompt1)
except Exception:
        logFile.write('could not read prompt1\n')
interact.send('conf t')
try:
        interact.expect(confPrompt)
except Exception:
        logFile.write('could not read confPrompt\n')
interact.send('crypto ca authenticate SSL-Trustpoint')
interact.expect('.*by itself.*')
for line in caCert.splitlines():
        interact.send(line)
        time.sleep(.1)
interact.send('quit')
interact.expect(keyPrompt)
interact.send('y')
interact.expect(confPrompt)
interact.send('crypto ca import SSL-Trustpoint certificate')
interact.expect(keyPrompt)
interact.send('y')
interact.expect('.*by itself.*')
lines2 = certFile.read().splitlines()
for line2 in lines2:
        interact.send(line2)
        time.sleep(.1)
certFile.close()
interact.send('quit')
interact.expect(confPrompt)
interact.send('ssl trust-point SSL-Trustpoint outside')
interact.expect(confPrompt)
if i == 0:
        interact.send('crypto ikev2 remote-access trustpoint SSL-Trustpoint')
        interact.expect(confPrompt)
interact.send('exit')
interact.expect(prompt1)
interact.send('wr')
interact.expect(prompt1)
logFile.write('SUCCESSFULLY installed the cert and chain to your ASA!\n')
logFile.close()
interact.send('exit')

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