Linux, Networking, Security: Get Remote SSL Certificate From Command Line

Easy way to get the SSL certificate of a server from the command line in Linux. The nice thing about it is that you get the full certificate chain. Nice for troubleshooting issues.  After the “-connect”, specify the host and port you want to connect to.  TCP port 443 is the default https port.

[user1@testserver ~]$ openssl s_client -connect mail.google.com:443

CONNECTED(00000003)
---
Certificate chain
 0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=mail.google.com
   i:/C=ZA/O=Thawte Consulting (Pty) Ltd./CN=Thawte SGC CA
 1 s:/C=ZA/O=Thawte Consulting (Pty) Ltd./CN=Thawte SGC CA
   i:/C=US/O=VeriSign, Inc./OU=Class 3 Public Primary Certification Authority
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=/C=US/ST=California/L=Mountain View/O=Google Inc/CN=mail.google.com issuer=/C=ZA/O=Thawte Consulting (Pty) Ltd./CN=Thawte SGC CA
---
No client certificate CA names sent
---
SSL handshake has read 1778 bytes and written 316 bytes
---
New, TLSv1/SSLv3, Cipher is AES256-SHA
Server public key is 1024 bit
Compression: NONE
Expansion: NONE
SSL-Session:
    Protocol  : TLSv1
    Cipher    : AES256-SHA
    Session-ID: DEB23CF699255054E08F69181B2342E9F6D6DF0D02B399C36034E0D8BE18AC0C
    Session-ID-ctx:
    Master-Key: D696A99CEC2FDD9535FE2EC936531AD129FD97E56441E37AE7A143C40304E395EA7DA039797B948B009B42DA5377E668
    Key-Arg   : None
    Krb5 Principal: None
    Start Time: 1267560715
    Timeout   : 300 (sec)
    Verify return code: 0 (ok)
---
HTTP/1.0 400 Bad Request
Content-Type: text/html; charset=UTF-8
Content-Length: 1350
Date: Tue, 02 Mar 2010 20:11:57 GMT
Server: GFE/2.0
X-XSS-Protection: 0