cmd/openssl

About

openssl is the command-line program for managing SSL data and certificates.

Examples

• To check that a certificate file is valid, and see what it says (does not work with key files) - typical file extensions are .crt, .ca:

  openssl x509 -text -in <filename>

• To verify how a web server is presenting its certificate over https:

  openssl s_client -connect <domain>:443

  • To get the expiration date:

    echo | openssl s_client -connect <domain>:443 2>/dev/null | openssl x509 -noout -dates

• To generate a new private key:

  openssl genrsa -des3 -out <filename.key> 4096

• To remove the pass phrase from a private key:

  openssl rsa -in <oldfile.key> -out <newfile.key>

  There is slightly more explanation here.

Notes

• openssl verify [1] seems to be the tool of choice for checking certificate files stored locally.
• This also has some useful information about using openssl, and a little bit about the "chaining" concept.

Links

• manpage
  • openssl.cnf
• openssl.org
  • s_client
• examples
• Ubuntu documentation: OpenSSL