Displaying a remote SSL certificate details using CLI tools

In Chrome, clicking on the green HTTPS lock icon opens a window with the certificate details:

When I tried the same with cURL, I got only some of the information:

$ curl -vvI https://gnupg.org
* Rebuilt URL to: https://gnupg.org/
* Hostname was NOT found in DNS cache
*   Trying 217.69.76.60...
* Connected to gnupg.org (217.69.76.60) port 443 (#0)
* TLS 1.2 connection using TLS_DHE_RSA_WITH_AES_128_CBC_SHA
* Server certificate: gnupg.org
* Server certificate: Gandi Standard SSL CA
* Server certificate: UTN-USERFirst-Hardware
> HEAD / HTTP/1.1
> User-Agent: curl/7.37.1
> Host: gnupg.org
> Accept: */*

Any idea how to get the full certificate information form a command line tool (cURL or other)?

Solution 1:

You should be able to use OpenSSL for your purpose:

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

That command connects to the desired website and pipes the certificate in PEM format on to another openssl command that reads and parses the details.

(Note that "redundant" -servername parameter is necessary to make openssl do a request with SNI support.)

Solution 2:

Simple solution

That's my everyday script:

curl --insecure -vvI https://www.google.com 2>&1 | awk 'BEGIN { cert=0 } /^\* SSL connection/ { cert=1 } /^\*/ { if (cert) print }'

Output:

* SSL connection using TLS1.2 / ECDHE_RSA_AES_128_GCM_SHA256
*    server certificate verification SKIPPED
*    server certificate status verification SKIPPED
*    common name: www.google.com (matched)
*    server certificate expiration date OK
*    server certificate activation date OK
*    certificate public key: RSA
*    certificate version: #3
*    subject: C=US,ST=California,L=Mountain View,O=Google Inc,CN=www.google.com
*    start date: Wed, 24 May 2017 17:39:15 GMT
*    expire date: Wed, 16 Aug 2017 17:13:00 GMT
*    issuer: C=US,O=Google Inc,CN=Google Internet Authority G2
*    compression: NULL
* ALPN, server accepted to use http/1.1
* Connection #0 to host www.google.com left intact

Solution 3:

nmap -p 443 --script ssl-cert gnupg.org

The -p 443 specifies to scan port 443 only. All ports will be scanned if it is omitted, and the certificate details for any SSL service that is found will be displayed. The --script ssl-cert tells the Nmap scripting engine to run only the ssl-cert script. From the doc, this script "(r)etrieves a server's SSL certificate. The amount of information printed about the certificate depends on the verbosity level."

Sample output:

Starting Nmap 7.40 ( https://nmap.org ) at 2017-11-01 13:35 PDT
Nmap scan report for gnupg.org (217.69.76.60)
Host is up (0.16s latency).
Other addresses for gnupg.org (not scanned): (null)
rDNS record for 217.69.76.60: www.gnupg.org
PORT    STATE SERVICE
443/tcp open  https
| ssl-cert: Subject: commonName=gnupg.org
| Subject Alternative Name: DNS:gnupg.org, DNS:www.gnupg.org
| Issuer: commonName=Gandi Standard SSL CA 2/organizationName=Gandi/stateOrProvinceName=Paris/countryName=FR
| Public Key type: rsa
| Public Key bits: 2048
| Signature Algorithm: sha256WithRSAEncryption
| Not valid before: 2015-12-21T00:00:00
| Not valid after:  2018-03-19T23:59:59
| MD5:   c3a7 e0ed 388f 87cb ec7f fd3e 71f2 1c3e
|_SHA-1: 5196 ecf5 7aed 139f a511 735b bfb5 7534 df63 41ba

Nmap done: 1 IP address (1 host up) scanned in 2.31 seconds