Forum Discussion

SSHSSH_97332's avatar
SSHSSH_97332
Icon for Nimbostratus rankNimbostratus
May 14, 2012

Regular Expression to Force Parameter to be in IP Format

i need to force parameter value to be in IP format : ( 3 digits . 3 digits . 3 digits . 3 digits ) , i found option called regex ( regular expression ) under parameters Tab . How can i define regex t...
app sec
BIG-IP Access Policy Manager (APM)
security
mister_paul_717's avatar
mister_paul_717
Icon for Nimbostratus rankNimbostratus
May 14, 2012
Every tool has a slightly different implementation of regex. I haven't tested this on F5 yet, so it might not be quite right, but give it a try. I use it ALOT on other systems.

 

 

[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}

 

 

 

 

 

 

If f5 supports perl regexes, you can simplify it with

 

\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

 

 

 

The important difference between this and the previous poster's regex is it allows each octet in the ip (the octet is the 0-255 number) to be 1-3 digits. Most systems don't 0-pad the octets into 3 digit numbers, so you need this range.

 

 

 

This regex isn't perfect. It does not force the numbers to be 0-255 ( would match) but normally that is not a problem. However, you might need a more precise solution, for example, if you're trying to protect a parameter that lacks data validation. It probably is possible to write such a regex (I would try look-aheads), but it would be very complex and difficult for others to understand. I would advise against a regex in such a case.