How to configure John The Ripper to use a static string as part of password discovery?

Question

I recendly found an old microcontroller project of mine again and want to use it. Unfortunatly I forgot the password but know the middle of it. Further I get managed to free the shadow file.

Is there a way to tell John The Ripper "hey, this string is part of the password"? So John is only trying to prepend and/or append characters to it. Currently John is trying (unnecessarily) random passwords for some weeks now.

As far as I understand John's wordlist features contains only complete passwords to try and not just parts of it.

So: How to configure John The Ripper to use a static string as part of password discovery?

Answer 1

Use rules to append and and prefix character to that known part of the password. $x - will add character x to the end of the known password
$x $y - will add character xy to the end of the known password
^x - will add character x to the end of the known password
^x ^y - will add character xy to the beginning of the known password

In addition your "known part of the password part" should be on a text file. (i.e. Dictionary file) configured in john.conf/john.ini, same with the rule to be used.