This popped up on my Twitter feed earlier: -
Check the expiration date of an SSL or TLS certificate
and I thought it worth book marking ...
Checking the expiration of various certificates on my network ....
openssl s_client -servername 192.168.1.1 -connect 192.168.1.1:443 < /dev/null | openssl x509 -noout -dates
depth=0 C = TW, ST = HsinChu, L = HuKou, O = DrayTek Corp., OU = DrayTek Support, CN = Vigor Router
verify error:num=18:self signed certificate
verify return:1
depth=0 C = TW, ST = HsinChu, L = HuKou, O = DrayTek Corp., OU = DrayTek Support, CN = Vigor Router
verify return:1
poll errornotBefore=Aug 30 17:21:28 2020 GMT
notAfter=Sep 29 17:21:28 2021 GMT
openssl s_client -servername 192.168.1.12 -connect 192.168.1.12:443 < /dev/null | openssl x509 -noout -dates
depth=0 CN = HP3050A, L = Vancouver, ST = Washington, C = US, O = HP, OU = HP-IPG
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 CN = HP3050A, L = Vancouver, ST = Washington, C = US, O = HP, OU = HP-IPG
verify error:num=21:unable to verify the first certificate
verify return:1
poll errornotBefore=Mar 16 06:51:44 2012 GMT
notAfter=Mar 11 06:51:44 2032 GMT
openssl s_client -servername nessus.local.com -connect nessus.local.com:8834 < /dev/null | openssl x509 -noout -dates
depth=0 O = Nessus Users United, OU = Nessus Server, L = New York, C = US, ST = NY, CN = nessus.local.com
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 O = Nessus Users United, OU = Nessus Server, L = New York, C = US, ST = NY, CN = nessus.local.com
verify error:num=21:unable to verify the first certificate
verify return:1
poll errornotBefore=Oct 4 12:29:02 2019 GMT
notAfter=Oct 3 12:29:02 2023 GMT