Read Contents Of SSL Cert From The Command Line

Whilst it is possible to view the contents of an SSL cert from within most modern browsers I occasionally find the need to use the command line to find out the same information. I find this useful when renewing certificates as browsers can occasionally cache certificates for longer than expected, causing false results.

The following command connects to the server, downloads the SSL certificate from port 443 and then uses the openssl tool to extract the information from the certificate into a readable format.

echo | openssl s_client -showcerts -servername example.com -connect example.com:443 2>/dev/null | openssl x509 -inform pem -noout -text

This produces the following output.

Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            0f:d0:78:dd:48:f1:a2:bd:4d:0f:2b:a9:6b:60:38:fe
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=US, O=DigiCert Inc, CN=DigiCert SHA2 Secure Server CA
        Validity
            Not Before: Nov 28 00:00:00 2018 GMT
            Not After : Dec  2 12:00:00 2020 GMT
        Subject: C=US, ST=California, L=Los Angeles, O=Internet Corporation for Assigned Names and Numbers, OU=Technology, CN=www.example.org
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:d0:f0:12:74:a0:96:20:72:08:65:19:12:5a:5d:
                    4a:d0:3a:8c:66:8f:a0:29:2b:a7:db:d5:ac:0c:cf:
                    a5:71:92:15:42:15:b0:07:92:76:31:75:d7:27:8e:
                    4d:50:6a:75:d1:7b:53:5e:27:aa:ed:eb:a4:60:3a:
                    f2:8e:45:18:6b:45:33:5c:85:11:aa:20:12:fe:60:
                    ac:9d:4c:45:8f:dd:d3:0e:3e:77:0f:09:c2:85:65:
                    34:c7:22:fb:74:13:b9:42:9f:f7:21:f6:f0:9c:44:
                    74:6d:c9:df:b3:1f:8f:60:b7:71:11:06:90:63:41:
                    9d:8f:34:7b:24:49:46:ac:f2:f0:8d:0b:48:f4:d3:
                    92:1a:f7:a2:45:ee:cc:e5:d7:83:7f:2e:82:bd:71:
                    dd:28:19:58:33:6e:11:a1:3a:a0:6a:72:60:92:01:
                    59:9f:63:17:7a:49:42:7b:9c:3f:db:d3:05:e8:cc:
                    87:7e:f8:aa:fc:9d:d1:05:50:ab:75:b1:1e:ba:20:
                    cb:89:d4:6d:6c:37:82:28:4c:c5:3f:7c:c1:10:f5:
                    a0:a5:66:6b:53:53:c9:db:ed:85:c3:6d:05:f8:64:
                    a7:c9:0e:eb:8f:e1:c4:b1:eb:2d:68:0e:15:3f:e5:
                    e2:dc:fc:21:64:2d:ee:69:2b:04:78:db:77:65:cb:
                    54:f9
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Authority Key Identifier:
                keyid:0F:80:61:1C:82:31:61:D5:2F:28:E7:8D:46:38:B4:2C:E1:C6:D9:E2

            X509v3 Subject Key Identifier:
                66:98:62:02:E0:09:91:A7:D9:E3:36:FB:76:C6:B0:BF:A1:6D:A7:BE
            X509v3 Subject Alternative Name:
                DNS:www.example.org, DNS:example.com, DNS:example.edu, DNS:example.net, DNS:example.org, DNS:www.example.com, DNS:www.example.edu, DNS:www.example.net
            X509v3 Key Usage: critical
                Digital Signature, Key Encipherment
            X509v3 Extended Key Usage:
                TLS Web Server Authentication, TLS Web Client Authentication
            X509v3 CRL Distribution Points:

                Full Name:
                  URI:http://crl3.digicert.com/ssca-sha2-g6.crl

                Full Name:
                  URI:http://crl4.digicert.com/ssca-sha2-g6.crl

            X509v3 Certificate Policies:
                Policy: 2.16.840.1.114412.1.1
                  CPS: https://www.digicert.com/CPS
                Policy: 2.23.140.1.2.2

            Authority Information Access:
                OCSP - URI:http://ocsp.digicert.com
                CA Issuers - URI:http://cacerts.digicert.com/DigiCertSHA2SecureServerCA.crt

            X509v3 Basic Constraints: critical
                CA:FALSE
            1.3.6.1.4.1.11129.2.4.2:
                ...k.i.w.......X......gp
.....g\1.F.....H0F.!..d..!...H.v.K.F.W'..{.;.JWBl...l.!.....0.d..L|nXSW....EO..F..p...BB.v..u..Y|..C._..n.V.GV6.J.`....^......g\1.......G0E. o.w.....c-....A.@../..f.._s.H.P..!....H.....D%.<...+.|..'{..X....JN.v.oSv.1.1.....Q..w.....}..c).-. MwZ.I.J.h..a... .1....q.C.....O...z....D;....
[.V.=,r.
    Signature Algorithm: sha256WithRSAEncryption
         73:70:85:ef:40:41:a7:6a:43:d5:78:9c:7b:55:48:e6:bc:6b:
         99:86:ba:fb:0d:03:8b:78:fe:11:f0:29:a0:0c:cd:69:14:0b:
         c6:04:78:b2:ce:f0:87:d5:01:9d:c4:59:7a:71:fe:f0:6e:9e:
         c1:a0:b0:91:2d:1f:ea:3d:55:c5:33:05:0c:cd:c1:35:18:b0:
         6a:68:66:4c:bf:56:21:da:5b:d9:48:b9:8c:35:21:91:5d:dc:
         75:d7:7a:46:2c:22:27:a6:6f:d3:3a:17:eb:be:bd:13:c5:12:
         26:73:c0:5d:a3:35:89:6a:fb:27:d4:dd:aa:74:74:2e:37:e5:
         01:3b:a6:d0:30:b0:83:d0:a1:c4:75:21:85:b2:e5:fa:67:00:
         30:a2:bc:53:83:4d:bf:d6:a8:83:bb:bc:d6:ed:1c:b3:1e:f1:
         58:03:82:00:8e:9c:ef:90:f2:1a:5f:a2:a3:06:da:5d:be:9f:
         da:5d:a6:e6:2f:de:58:80:18:d3:f1:62:7b:a6:a3:9f:ae:a8:
         69:72:63:81:65:ae:82:83:a3:b5:97:8a:9b:20:51:ff:1a:3f:
         61:40:1e:48:d0:6b:38:f9:e1:fa:17:d8:77:4a:88:e6:3d:36:
         24:4f:ef:0a:b9:9f:70:f3:83:27:f8:cf:2a:05:75:10:a1:8a:
         0a:80:88:cd