The squidGuard FAQ
squidGuard is an ultrafast and free filter, redirector and access controller for Squid By Pål Baltzersen and Lars Erik Håland Copyright © 1999-2000, Tele Danmark InterNordia

This page was last modified 2001-12-18

## FAQ - Frequently Asked/Answered Questions

Currently in semirandom order:

1. Is there a mailing list for squidGuard?
     Yes!.
2. I have db3.x.x installed and squidGuard won't compile?
     Only db2.x.x versions are supported. We are working on db3.x.x support, but the API has changed so it may take a while to fix.
3. squidGuard does not block?
     There my be at least 2 reasons for this:
     1. You didn't end your pass rules with "none". Pass rules ends with an implicit "all". It is good practice to allways en the pass rules with either "all" or "none" to make them clear. Ie. use:
        `pass good none`
        or
        `pass good !bad all`
     2. squidGuard goes into emergency mode. Reasons may be syntax errors in the config file, reference to non existing database files, filprotection problems or missing directories. Check the squidGuard log.
        Note:When run under Squid, squidGuard is run with the same user and group ID as Squid (`cache_effective_user` and `cache_effective_group` in squid.conf). The squidGuard configuration and database files must be readable for this user and/or group and the squidGuard log directory must be writable for this user and/or group. If not squidGuard will go into the "pass all for all" emergency mode.
4. How do I debug squidGuard?
     Do something like this:
     `echo "http://foo/bar 10.0.0.1/- - GET" | /usr/local/bin/squidGuard -c /tmp/test.cfg -d`
     This redirects the log to stderr. The response is either a blank line (pass on) or a the input with the URL part rewritten (redirect).
5. How can I block audio and video?
     Use an expressionlist with something like this:
     `\.(ra?m|mpe?g?|mov|movie|qt|avi|dif|dvd?|mpv2|mp3)($|\?)`
6. Are there any blacklist exchange plans?
     Yes, we plan to add an interface to the new web site to allow proxyadministrators to indirectly add and remove URLs from the robot config. Though there are still some practical issues to solve.
7. How can I contribute to the blacklists?
     If you have lists of links that would map to missing blacklist entries, or lists of exceptions/errors, please send them to blacklist@squidguard.org
     Note: The link list must consist of fully qualified URLs, ie. http://... (not the blacklist format).
     The exception/error lists must consist of domains and urls as (potentially) found in the blacklists.
     Direct additions to the domain and url lists are not very usefull, since they are the output from the robot; not the input. Though if you have a long list that would have been usefull you may of course reverse engineer it through:
     `sed 's@^@http://www.@;s@$@/@' domains urls >links`
8. How can I test timeconstraints
     You can set a simulated start time with the `-t yyyy-mm-ddTHH:MM:SS` option:
       `squidGuard -c test.conf -t 1999-12-31T23:59:30 -d <test.in>test.out 2>test.log`
     With the -t option squidGuard parses the given date&time and calculates an offset from the current time at startup and then adds this offset to all timevalues during runtime.
9. squidGuard compiles fine and the tests succeed, but it seems to pass all when run under Squid
     There may be at leaste two reasons for this:
     - Some versions of Squid (supposedly 2.2.*) silently ignores argumets to the right of `redirect_program prefix/bin/squidGuard`. Solutions are one of:
       - Set the actual config file location at compiletime with `--with-sg-config`
       - Use a shell wraper with `redirect_program prefix/bin/squidGuard.sh` and make `prefix/bin/squidGuard.sh` an executable shell like:
           `#! /bin/sh -
           exec prefix/bin/squidGuard -c whatever/squidGuard.conf`
     - When run under Squid, squidGuard is run with the same user and group ID as Squid (`cache_effective_user` and `cache_effective_group` in squid.conf). The squidGuard configuration and database files must be readable for this user and/or group and the squidGuard log directory must be writable for this user and/or group. If not squidGuard will go into the "pass all for all" emergency mode.
10. compilation of sg.l on fails with `"sg.l:line ...: Error: Too many positions"` with native lex
      Some native versions of lex have problems with sg.l. The solution is to use GNU flex wich is better anyway. Do "`setenv LEX flex`" if configure selects the native lex before flex. Flex should compile right out of the box similar to other GNU programs. (Thanks to laurent.foulonneau@mail.loyalty.nc).
11. Can I use proxy authenticated user the same way as RFC931/Ident user?
      Yes, if you patch Squid < 2.3 with this simple diff, kindly contributed by Antony T Curtis, the authenticated user will be passed from Squid to squidGuard. This patch has apparently already been incorporated in squid-2.3:
      `

          	A useful patch to Squid 2.2STABLE which fixes per-user redirection where
          	the user is authenticated using proxy-auth...

          	*** src/redirect.c.orig Tue Jun 22 14:04:43 1999
          	--- src/redirect.c      Tue Jun 22 15:46:41 1999
          	***************
          	*** 103,108 ****
          	--- 103,110 ----
          	      cbdataAdd(r, cbdataXfree, 0);
          	      r->orig_url = xstrdup(http->uri);
          	      r->client_addr = conn->log_addr;
          	+     if (http->request->user_ident[0])
          	+       r->client_ident = http->request->user_ident; else
          	      if (conn->ident == NULL || *conn->ident == '\0') {
          		r->client_ident = dash_str;
          	      } else {

      `
12. Can I manipulate domains.db and urls.db from Perl?
      Yes, but you must bind custom comparefunctions. Also note the domains are stored with a leading ".":
      `

                  use DB_File;

          	sub mirror($) {
          	  scalar(reverse(shift));
          	}

          	sub domainmatch($$) {
          	  my $search = mirror(lc(shift));
          	  my $found = mirror(lc(shift));
          	  if ("$search." eq $found) {
          	    return(0);
          	  } else {
          	    return(substr($search,0,length($found)) cmp $found);
          	  }
          	}

          	sub urlmatch($$) {
          	  my $search = lc(shift) . "/";
          	  my $found = lc(shift) . "/";
          	  if ($search eq $found) {
          	    return(0);
          	  } else {
          	    return(substr($search,0,length($found)) cmp $found);
          	  }
          	}

          	my (%url,%domain);

          	$DB_BTREE->{compare} = \&urlmatch;
          	my $url_db = tie(%url, "DB_File", "urls.db", O_CREAT|O_RDWR, 0664, $DB_BTREE)
          	|| die("urls.db: $!\n");

          	$DB_BTREE->{compare} = \&domainmatch;
          	my $domain_db = tie(%domain, "DB_File", "domains.db", O_CREAT|O_RDWR, 0664, $DB_BTREE)
          	|| die("domains.db: $!\n");

          	# Now you can operate on %url and %domain just as normal perl hashes:)
          	# Add "playboy.com" to the domainlist unless it's already there:
          	$domain{".playboy.com"} = "" unless(exists($domain{"playboy.com"}));
          	# or use the DB_File functions put, get, del and seq:
          	# Add "sex.com" and "dir.yahoo.com/business_and_economy/companies/sex"
          	# and delete "cnn.com":
          	$domain_db->put(".sex.com","") unless(exists($domain{"sex.com"}));
          	$domain_db->sync; # Seems to only sync the last change.
          	$domain_db->del("cnn.com") if(exists($domain{"cnn.com"}));
          	$domain_db->sync; # Seems to only sync the last change.
          	$url_db->put("xyz.com/~sex","") unless(exists($url{"xyz.com/~sex"}));
          	$url_db->sync; # Seems to only sync the last change.

          	$url_db->sync; # Seems to only sync the last change.
          	$domain_db->sync; # Seems to only sync the last change.
          	undef($url_db); # Destroy the object
          	undef($domain_db); # Destroy the object
          	untie(%url); # Sync and close the file and undef the hash
          	untie(%domain); # Sync and close the file and undef the hash

      ` See the perltie(1) and DB_File(3) man pages that comes with Perl for more info.
13. How can I list domains.db or urls.db from Perl?
      Use a script like this:
      `

          	#!/local/bin/perl -w
          	use strict;
          	use DB_File;

          	foreach (@ARGV) {
          	  my (%db, $key, $val);
          	  die("$_: $!\n") unless(-f);
          	  tie(%db, "DB_File", $_, O_RDONLY, 0664, $DB_BTREE) || die("$_: $!\n");
          	  foreach $key (keys(%db)) {
          	    if($val = $db{$key}) {
          	      $val = "\"$val\"";
          	    } else {
          	      $val = "undef";
          	    }
          	    print "$key -> $val\n";
          	  }
          	  untie(%db);
          	}

      ` See the perltie(1) and DB_File(3) man pages that comes with Perl for more info.
14. How can I get around "make: don't know how to make /bin/false. Stop"?
      Your system does not have lynx and not /bin/false either: If it has /usr/bin/false do:
      `

          	# ln -s ../usr/bin/false /bin/.

      ` Alternatively:
      `

          	# echo exit 255 >/bin/false
          	# chmod a+rx /bin/false

      `

If you have questions and/or answers that should be on the FAQ list please send them to squidguard@squidguard.org