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               'insert' => 'INSERT INTO foo VALUES (?, ?, ?)'
               }
        }

then only the users root and wwwrun may connect from admin.company.com,
executing arbitrary queries, but only wwwrun may connect from other
hosts and is restricted to

    $sth->prepare("select");

or

    $sth->prepare("insert");

which in fact are "SELECT * FROM foo" or "INSERT INTO foo VALUES (?, ?, ?)".


=head1 Proxyserver Configuration file (bigger example)

This section tells you how to restrict a DBI-Proxy: Not every user from
every workstation shall be able to execute every query.

There is a perl program "dbiproxy" which runs on a machine which is able
to connect to all the databases we wish to reach. All Perl-DBD-drivers must
be installed on this machine. You can also reach databases for which drivers
are not available on the machine where you run the program querying the
database, e.g. ask MS-Access-database from Linux.

Create a configuration file "proxy_oracle.cfg" at the dbproxy-server:

    {
	# This shall run in a shell or a DOS-window
	# facility => 'daemon',
	pidfile => 'your_dbiproxy.pid',
	logfile => 1,
	debug => 0,
	mode => 'single',
	localport => '12400',

	# Access control, the first match in this list wins!
	# So the order is important
	clients => [
		# hint to organize:
		# the most specialized rules for single machines/users are 1st
		# then the denying rules
		# then the rules about whole networks

		# rule: internal_webserver
		# desc: to get statistical information
		{
			# this IP-address only is meant
			mask => '^10\.95\.81\.243$',
			# accept (not defer) connections like this
			accept => 1,
			# only users from this list
			# are allowed to log on
			users => [ 'informationdesk' ],
			# only this statistical query is allowed
			# to get results for a web-query
			sql => {
				alive => 'select count(*) from dual',
				statistic_area => 'select count(*) from e01admin.e01e203 where geb_bezei like ?',
			}
		},

		# rule: internal_bad_guy_1
		{
			mask => '^10\.95\.81\.1$',
			accept => 0,
		},

		# rule: employee_workplace
		# desc: get detailed information
		{
			# any IP-address is meant here
			mask => '^10\.95\.81\.(\d+)$',
			# accept (not defer) connections like this
			accept => 1,
			# only users from this list
			# are allowed to log on
			users => [ 'informationdesk', 'lippmann' ],
			# all these queries are allowed:
			sql => {
				search_city => 'select ort_nr, plz, ort from e01admin.e01e200 where plz like ?',
				search_area => 'select gebiettyp, geb_bezei from e01admin.e01e203 where geb_bezei like ? or geb_bezei like ?',
			}
		},

		# rule: internal_bad_guy_2
		# This does NOT work, because rule "employee_workplace" hits
		# with its ip-address-mask of the whole network
		{
			# don't accept connection from this ip-address
			mask => '^10\.95\.81\.5$',
			accept => 0,
		}
	]
    }

Start the proxyserver like this:

	rem well-set Oracle_home needed for Oracle
	set ORACLE_HOME=d:\oracle\ora81
	dbiproxy --configfile proxy_oracle.cfg


=head2 Testing the connection from a remote machine

Call a program "dbish" from your commandline. I take the machine from rule "internal_webserver"

	dbish "dbi:Proxy:hostname=oracle.zdf;port=12400;dsn=dbi:Oracle:e01" informationdesk xxx

There will be a shell-prompt:

	informationdesk@dbi...> alive

	Current statement buffer (enter '/'...):
	alive

	informationdesk@dbi...> /
	COUNT(*)
	'1'
	[1 rows of 1 fields returned]


=head2 Testing the connection with a perl-script

Create a perl-script like this:

	# file: oratest.pl
	# call me like this: perl oratest.pl user password

	use strict;
	use DBI;

	my $user = shift || die "Usage: $0 user password";
	my $pass = shift || die "Usage: $0 user password";
	my $config = {
		dsn_at_proxy => "dbi:Oracle:e01",
		proxy => "hostname=oechsle.zdf;port=12400",
	};
	my $dsn = sprintf "dbi:Proxy:%s;dsn=%s",
		$config->{proxy},
		$config->{dsn_at_proxy};

	my $dbh = DBI->connect( $dsn, $user, $pass )
		|| die "connect did not work: $DBI::errstr";

	my $sql = "search_city";
	printf "%s\n%s\n%s\n", "="x40, $sql, "="x40;
	my $cur = $dbh->prepare($sql);
	$cur->bind_param(1,'905%');
	&show_result ($cur);

	my $sql = "search_area";
	printf "%s\n%s\n%s\n", "="x40, $sql, "="x40;
	my $cur = $dbh->prepare($sql);
	$cur->bind_param(1,'Pfarr%');
	$cur->bind_param(2,'Bronnamberg%');
	&show_result ($cur);

	my $sql = "statistic_area";
	printf "%s\n%s\n%s\n", "="x40, $sql, "="x40;
	my $cur = $dbh->prepare($sql);
	$cur->bind_param(1,'Pfarr%');
	&show_result ($cur);

	$dbh->disconnect;
	exit;


	sub show_result {
		my $cur = shift;
		unless ($cur->execute()) {
			print "Could not execute\n";
			return;
		}

lib/DBI/ProxyServer.pm  view on Meta::CPAN

				last;
			}
		}
		$cur->finish;
	}

The result

	C:\>perl oratest.pl informationdesk xxx
	========================================
	search_city
	========================================
	Row is: 3322, 9050, Chemnitz
	Row is: 3678, 9051, Chemnitz
	Row is: 10447, 9051, Chemnitz
	Row is: 12128, 9051, Chemnitz
	Row is: 10954, 90513, Zirndorf
	Row is: 5808, 90513, Zirndorf
	Row is: 5715, 90513, Zirndorf
	... and so on
	========================================
	search_area
	========================================
	Row is: 101, Bronnamberg
	Row is: 400, Pfarramt Zirndorf
	Row is: 400, Pfarramt Rosstal
	Row is: 400, Pfarramt Oberasbach
	Row is: 401, Pfarramt Zirndorf
	Row is: 401, Pfarramt Rosstal
	========================================
	statistic_area
	========================================
	DBD::Proxy::st execute failed: Server returned error: Failed to execute method CallMethod: Unknown SQL query: statistic_area at E:/Perl/site/lib/DBI/ProxyServer.pm line 258.
	Could not execute


=head2 How the configuration works

The most important section to control access to your dbi-proxy is "client=>"
in the file "proxy_oracle.cfg":

Controlling which person at which machine is allowed to access

=over 4

=item * "mask" is a perl regular expression against the plain ip-address of the machine which wishes to connect _or_ the reverse-lookup from a nameserver.

=item * "accept" tells the dbiproxy-server whether ip-addresses like in "mask" are allowed to connect or not (0/1)

=item * "users" is a reference to a list of usernames which must be matched, this is NOT a regular expression.

=back

Controlling which SQL-statements are allowed

You can put every SQL-statement you like in simply omitting "sql => ...", but the more important thing is to restrict the connection so that only allowed queries are possible.

If you include an sql-section in your config-file like this:

	sql => {
		alive => 'select count(*) from dual',
		statistic_area => 'select count(*) from e01admin.e01e203 where geb_bezei like ?',
	}

The user is allowed to put two queries against the dbi-proxy. The queries are _not_ "select count(*)...", the queries are "alive" and "statistic_area"! These keywords are replaced by the real query. So you can run a query for "alive":

	my $sql = "alive";
	my $cur = $dbh->prepare($sql);
	...

The flexibility is that you can put parameters in the where-part of the query so the query are not static. Simply replace a value in the where-part of the query through a question mark and bind it as a parameter to the query.

	my $sql = "statistic_area";
	my $cur = $dbh->prepare($sql);
	$cur->bind_param(1,'905%');
	# A second parameter would be called like this:
	# $cur->bind_param(2,'98%');

The result is this query:

	select count(*) from e01admin.e01e203
	where geb_bezei like '905%'

Don't try to put parameters into the sql-query like this:

	# Does not work like you think.
	# Only the first word of the query is parsed,
	# so it's changed to "statistic_area", the rest is omitted.
	# You _have_ to work with $cur->bind_param.
	my $sql = "statistic_area 905%";
	my $cur = $dbh->prepare($sql);
	...


=head2 Problems

=over 4

=item * I don't know how to restrict users to special databases.

=item * I don't know how to pass query-parameters via dbish

=back


=head1 SECURITY WARNING

L<RPC::PlServer> used underneath is not secure due to serializing and
deserializing data with L<Storable> module. Use the proxy driver only in
trusted environment.


=head1 AUTHOR

    Copyright (c) 1997    Jochen Wiedmann
                          Am Eisteich 9
                          72555 Metzingen
                          Germany

                          Email: joe@ispsoft.de
                          Phone: +49 7123 14881

The DBI::ProxyServer module is free software; you can redistribute it
and/or modify it under the same terms as Perl itself. In particular
permission is granted to Tim Bunce for distributing this as a part of
the DBI.