RegEx - Pattern Match

Reply
Not applicable

RegEx - Pattern Match

Hey everyone,

I'm attempting to build a pattern match for a custom vulnerability.  Here are the criteria:

  • File is always a random 24 character file with a '.exe' extension
  • First three characters are always 'e54'

I had the following regex built, but the PA doesn't like it for some reason.

(e54([a-zA-Z0-9]{21})\.exe)

It gives me some invalid character internal error.  Any thoughts?

Tags (1)
L7 Applicator

Re: RegEx - Pattern Match

Hello mrsold,

A Pattern must be at least 7 bytes. In the entire pattern there must exist at least one 7 byte string that has fixed values.

Regular expression syntax for patterns in custom app signatures

Thanks

Not applicable

Re: RegEx - Pattern Match

HULK wrote:

Hello mrsold,

A Pattern must be at least 7 bytes. In the entire pattern there must exist at least one 7 byte string that has fixed values.

Regular expression syntax for patterns in custom app signatures

Thanks

Thanks Hulk. 

Am I counting wrong?  I thought that string I posted is at least 7 bytes.

L7 Applicator

Re: RegEx - Pattern Match

Hello mrsold,

There should be a continuous 7 byte string.

Examples

-> pattern -> a -> regex 'abc[abc]{3}abc.*abc' is invalid.

->  'abc.{3}abcdefg.*abc' ----is valid >>>>>>>> 7 byte

        -> foo.*bar.*foobarfoo   (invalid)

        ->  foo.*fooba       (valid)

Hope this helps.

Thanks

Not applicable

Re: RegEx - Pattern Match

HULK wrote:

Hello mrsold,

There should be a continuous 7 byte string.

Examples

-> pattern -> a -> regex 'abc[abc]{3}abc.*abc' is invalid.

->  'abc.{3}abcdefg.*abc' ----is valid >>>>>>>> 7 byte

        -> foo.*bar.*foobarfoo   (invalid)

        ->  foo.*fooba       (valid)

Hope this helps.

Thanks

Ah yes, the continuous is a very important part.

Thanks!

L2 Linker

Re: RegEx - Pattern Match

Hi Guys,

I'm trying to create the pattern to reset the connection if the connection comes from Internet Explorer.

I took PCAP with wireshark and user-agent shows as : "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko" (there is \r\n at the end but I think its wireshark? )

Nevertheless

I copied my text to RegExr; and did my regular expression to match.

.*Mozilla\/5\.0\s\(Windows\sNT\s6\.1\;\sWOW64\;\sTrident\/7\.0\;\srv\:11\.0\)\slike\sGecko

it highlights the text, meaning It is a valid expression, Palo Alto takes it, and while I was troubleshooting I even got some hits but internet explorer works as normal.

Can you tell if this is even possible?

L0 Member

Re: RegEx - Pattern Match

Hello,

 

I know this is an old thread but anyone knows why this particular string is not accepted as a pattern for SNI with ssl client hello as context? It keeps telling me it has to be at least 7 byte long.

 

www.gsop.avxeur.com

gsop.avxeur.com

avx.eur.com

 

All the above cannot go through..

 

i randomly try youtube.com, singtel.com, asiaone.com, all is ok.

 

Hope somone can help! Thanks! 

Like what you see?

Show your appreciation!

Click Like if a post is helpful to you or if you just want to show your support.

Click Accept as Solution to acknowledge that the answer to your question has been provided.

The button appears next to the replies on topics you’ve started. The member who gave the solution and all future visitors to this topic will appreciate it!

These simple actions take just seconds of your time, but go a long way in showing appreciation for community members and the Live Community as a whole!

The Live Community thanks you for your participation!