Hardening di un web server Apache: differenze tra le versioni

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=== Come scrivere nuove regole ===
=== Come scrivere nuove regole ===
Il modulo <code>mod-security</code> può utilizzare due tipi di filtro:
* Simple Filter: nella forma <code>SecFilter directive</code>
* Advanced Filter: nella forma <code>SecFilterSelective directive</code>
I filtri Simple Filter
Simple filter directives apply on any filters you turned on, so in our case, on GET and POST request.
the syntax of simple filter directive is:
SecFilter KEYWORD [ACTIONS]
KEYWORD can be a string or a regular expression, ACTIONS is optionnal, if it is not defined, mod-security will use the SecFilterDefaultAction value (log and return 500 error page as we defined earlier, in mod-security skeleton file).
Advance filters do filter specific streams. Its syntax is:
SecFilterSelective LOCATION KEYWORD [ACTIONS]
Same here, ACTIONS is optionnal, LOCATION consist of a serie of location identifier separated by pipes (|). An advance filter looks like:
SecFilterSelective "REMOTE_ADDR|REMOTE_HOST" KEYWORD
you can get the full list of keywords from mod-security site . For actions, you might want to refer to mod-security documentation action page.
Among the most important actions, we could highlight:
pass:Allow request to continue on filter match. This action is useful when you want to log a match but otherwise do not want to take action.
allow:This is a stronger version of the previous filter. After this action is performed the request will be allowed through and no other filters will be tried.
deny:Interrupt request processing on a filter match. Unless the status action is used too, ModSecurity will immediately return a HTTP 500 error code
status:Use the supplied HTTP status code when request is denied.
redirect:On filter match redirect the user to the given URL.
exec:Execute a binary on filter match. Full path to the binary is required
log: Log filter match to the Apache error log.
nolog:Do not log the filter match. This will also prevent the audit logging from taking place.
chain: Rule chaining allows you to chain several rules into a bigger test. Only the last rule in the chain will affect the request but in order to reach it, all rules before it must be matched too.
auditlog/noauditlog: Log/Do not log the transaction information to the audit log.

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