CCSP Training

With ASA/PIX OS release 7.2, the inspection engines now can utilize regular expression lists for filtering.

In the following example, HTTP URL filtering for hosts/domains and URL content with regexes is shown. The example denies HTTP requests to host 136.3.9.2 that contain the strings “/cd/” or “/show/” in the URL.

!-- regex for the show URI string
regex SHOW ".*/[Ss][Hh][Oo][Ww]/.*"
!-- regex for the cd URI string
regex CD ".*/[Cc][Dd]/.*"
!-- regex for destinatinon host, can be a domain name also
regex HOST "136.3.9.2"

!-- now the host regex is used in a class map
!-- multiple regexes can be matched in class map
!-- note the "match-any", meaning that one match is sufficient
class-map type regex match-any CM_DOMAINS
 match regex HOST

!-- the URI string regexes are combined together in a class map
!-- note the "match-any", meaning that one match is sufficient
class-map type regex match-any CM_FORBIDDENURI
 match regex SHOW
 match regex CD

!-- now the host and the uri class map are combined
!-- note the "match-all", meaning that both conitions must match
!-- so the host and either one of the two URI regexes
class-map type inspect http match-all CM_H_BADREQUEST
 match request header host regex class CM_DOMAINS
 match request uri regex class CM_FORBIDDENURI

!-- now the last class-map is used in a policy map
!-- where the action is defined (reject and log)
policy-map type inspect http PM_DENYBADHTTP
 parameters
 class CM_H_BADREQUEST
  reset log

!-- the last step: the policy is applied to the default policy
!-- by stating it as an additional parameter to the inspect http command
policy-map global_policy
 class inspection_default
inspect http PM_DENYBADHTTP
!
service-policy global_policy global

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