Provided by: libapache2-mod-qos_11.61-1_amd64 bug


       qsfilter2  -  an  utility  to  generate  mod_qos  request  line  rules  out  from existing
       access/audit log data.


       qsfilter2 -i <path> [-c <path>] [-d <num>] [-h] [-b <num>] [-p|-s|-m|-o] [-l  <len>]  [-n]
       [-e] [-u 'uni'] [-k <prefix>] [-t] [-f <path>] [-v 0|1|2]


       mod_qos implements a request filter which validates each request line. The module supports
       both, negative and positive security model. The QS_Deny* directives are  used  to  specify
       request  line patterns which are not allowed to access the server (negative security model
       / blacklist). These rules are used to restrict access to certain  resources  which  should
       not be available to users or to protect the server from malicious patterns. The QS_Permit*
       rules implement a positive security model (whitelist). These directives are used to define
       allowed  request  line  patterns. Request which do not match any of these patterns are not
       allowed to access the server.

       qsfilter2 is an audit log analyzer used to generate filter rules (perl compatible  regular
       expressions)   which  may  be  used  by  mod_qos  to  deny  access  for  suspect  requests
       (QS_PermitUri rules). It parses existing audit log files  in  order  to  generate  request
       patterns covering all allowed requests.


       -i <path>
              Input  file  containing  request  URIs. The URIs for this file have to be extracted
              from the servers access logs. Each line of the input file contains  a  request  URI
              consiting of a path and and query.

              These access log data must include current request URIs but also request lines from
              previous rule generation steps. It must also  include  request  lines  which  cover
              manually  generated  rules. You may use the 'qos-path' and 'qos-query' variables to
              create an audit log  containing  all  request  data  (path  and  query/body  data).
              Example:     'CustomLog     audit_log    %{qos-path}n%{qos-query}n'.    See    also
     about the module settings.

       -c <path>
              mod_qos configuration file defining QS_DenyRequestLine and QS_PermitUri directives.
              qsfilter2  generates  rules  from access log data automatically. Manually generated
              rules (QS_PermitUri) may be provided from this file. Note: each manual rule must be
              represented by a request URI in the input data (-i) in order to make sure not to be
              deleted by the rule optimisation algorithm. QS_Deny* rules from this file are  used
              to filter request lines which should not be used for whitelist rule generation.
                     # manually defined whitelist rule:
                     QS_PermitUri +view deny "^[/a-zA-Z0-9]+/view\?(page=[0-9]+)?$"
                     # filter unwanted request line patterns:
                     QS_DenyRequestLine +printable deny ".*[\x00-\x19].*"

       -d <num>
              Depth  (sub  locations)  of  the  path string which is defined as a literal string.
              Default is 1.

       -h     Always use a string representing the handler name in the path even the url does not
              have a query. See also -d option.

       -b <num>
              Replaces  url pattern by the regular expression when detecting a base64/hex encoded
              string. Detecting sensibility is defined by a numeric value. You should use  values
              higher than 5 (default) or 0 to disable this function.

       -p     Represents query by pcre only (no literal strings).

       -s     Uses one single pcre for the whole query string.

       -m     Uses one pcre for multiple query values (recommended mode).

       -o     Does not care the order of query parameters.

       -l <len>
              Outsizes the query length by the defined length ({0,size+len}), default is 10.

       -n     Disables redundant rules elimination.

       -e     Exit on error.

       -u 'uni'
              Enables additional decoding methods. Use the same settings as you have used for the
              QS_Decoding directive.

       -k <prefix>
              Prefix used to generate rule identifiers (QSF by default).

       -t     Calculates the maximal latency per request (worst case) using the generated rules.

       -f <path>
              Filters the input by the provided path (prefix) only processing matching lines.

       -v <level>
              Verbose mode. (0=silent, 1=rule source, 2=detailed). Default is 1. Don't use  rules
              you  haven't  checked  the  request  data  used  to  generate it! Level 1 is highly
              recommended (as long as you don't have created the log  data  using  your  own  web


       The  output  of  qsfilter2  is  written  to  stdout.  The  output  contains  the generated
       QS_PermitUri directives but also information about the  source  which  has  been  used  to
       generate  these  rules.  It  is  very important to check the validity of each request line
       which has been used to calculate the QS_PermitUri rules. Each request line which has  been
       used  to generate a new rule is shown in the output prefixed by "ADD line <line number>:".
       These request lines should be stored and reused at any later rule generation (add them  to
       the  URI  input  file).  The  subsequent line shows the generated rule. At the end of data
       processing a list of all generated QS_PermitUri rules is shown. These  directives  may  be
       used withn the configuration file used by mod_qos.


         qsfilter2 -i loc.txt -c httpd.conf -m -e
         # ADD line 1: /aaa/
         # 003 ^(/[a-zA-Z0-9\-_]+)+[/]?\.?[a-zA-Z]{0,4}$
         # ADD line 3: /aaa/view?page=1
         # --- ^[/a-zA-Z0-9]+/view\?(page=[0-9]+)?$
         # ADD line 4: /aaa/edit?document=1
         # 004 ^[/a-zA-Z]+/edit\?((document)(=[0-9]*)*[&]?)*$
         # ADD line 5: /aaa/edit?image=1.jpg
         # 005 ^[/a-zA-Z]+/edit\?((image)(=[0-9\.a-zA-Z]*)*[&]?)*$
         QS_PermitUri +QSF001 deny "^[/a-zA-Z]+/edit\?((document|image)(=[0-9\.a-zA-Z]*)*[&]?)*$"
         QS_PermitUri +QSF002 deny "^[/a-zA-Z0-9]+/view\?(page=[0-9]+)?$"
         QS_PermitUri +QSF003 deny "^(/[a-zA-Z0-9\-_]+)+[/]?\.?[a-zA-Z]{0,4}$"


       qsdt(1),  qsexec(1),  qsgeo(1),  qsgrep(1),  qshead(1),  qslog(1),  qslogger(1), qspng(1),
       qsre(1), qsrespeed(1), qsrotate(1), qssign(1), qstail(1)


       Pascal Buchbinder,