Extract Certificate Info

Ishan jain February 12, 2023 10:34

At times working in terminal can be faster, after all openssl is cli first.

Update: Added example output

There have been time when I am sitting in terminal an needed to debug a certificate on a site.

To examine a downloaded certificate we can leverage openssl:

openssl x509 -in <crt_file> \
 -noout -fingerprint -issuer -enddate -subject -ext subjectAltName

Where:

crt_file location of certificate file, often with .crt extension

For example, following command will examine the certificate from example.com stored in /tmp/ folder:

openssl x509 -in /tmp/example.com.crt \
 -noout -fingerprint -issuer -enddate -subject -ext subjectAltName

This will give similar output:

SHA1 Fingerprint=4D:A2:5A:6D:5E:F6:2C:5F:95:C7:BD:0A:73:EA:3C:17:7B:36:99:9D
issuer=C = US, O = DigiCert Inc, CN = DigiCert Global G2 TLS RSA SHA256 2020 CA1
notAfter=Mar  1 23:59:59 2025 GMT
subject=C = US, ST = California, L = Los Angeles, O = Internet\C2\A0Corporation\C2\A0for\C2\A0Assigned\C2\A0Names\C2\A0and\C2\A0Numbers, CN = www.example.org
X509v3 Subject Alternative Name:
    DNS:www.example.org, DNS:example.net, DNS:example.edu, DNS:example.com, DNS:example.org, DNS:www.example.com, DNS:www.example.edu, DNS:www.example.net