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DBI::ProxyServer(3)   User Contributed Perl Documentation  DBI::ProxyServer(3)

       DBI::ProxyServer - a server for the DBD::Proxy driver

	   use DBI::ProxyServer;

       DBI::Proxy Server is a module for implementing a proxy for the DBI
       proxy driver, DBD::Proxy. It allows access to databases over the net‐
       work if the DBMS does not offer networked operations. But the proxy
       server might be usefull for you, even if you have a DBMS with inte‐
       grated network functionality: It can be used as a DBI proxy in a fire‐
       walled environment.

       DBI::ProxyServer runs as a daemon on the machine with the DBMS or on
       the firewall. The client connects to the agent using the DBI driver
       DBD::Proxy, thus in the exactly same way than using DBD::mysql,
       DBD::mSQL or any other DBI driver.

       The agent is implemented as a RPC::PlServer application. Thus you have
       access to all the possibilities of this module, in particular encryp‐
       tion and a similar configuration file. DBI::ProxyServer adds the possi‐
       bility of query restrictions: You can define a set of queries that a
       client may execute and restrict access to those. (Requires a DBI driver
       that supports parameter binding.) See "CONFIGURATION FILE".

       The provided driver script, dbiproxy, may either be used as it is or
       used as the basis for a local version modified to meet your needs.

       When calling the DBI::ProxyServer::main() function, you supply an array
       of options. These options are parsed by the Getopt::Long module.	 The
       ProxyServer inherits all of RPC::PlServer's and hence Net::Daemon's
       options and option handling, in particular the ability to read options
       from either the command line or a config file. See RPC::PlServer. See
       Net::Daemon. Available options include

       chroot (--chroot=dir)
	   (UNIX only)	After doing a bind(), change root directory to the
	   given directory by doing a chroot(). This is usefull for security,
	   but it restricts the environment a lot. For example, you need to
	   load DBI drivers in the config file or you have to create hard
	   links to Unix sockets, if your drivers are using them. For example,
	   with MySQL, a config file might contain the following lines:

	       my $rootdir = '/var/dbiproxy';
	       my $unixsockdir = '/tmp';
	       my $unixsockfile = 'mysql.sock';
	       foreach $dir ($rootdir, "$rootdir$unixsockdir") {
		   mkdir 0755, $dir;
	       require DBD::mysql;

		   'chroot' => $rootdir,

	   If you don't know chroot(), think of an FTP server where you can
	   see a certain directory tree only after logging in. See also the
	   --group and --user options.

	   An array ref with a list of clients. Clients are hash refs, the
	   attributes accept (0 for denying access and 1 for permitting) and
	   mask, a Perl regular expression for the clients IP number or its
	   host name.

       configfile (--configfile=file)
	   Config files are assumed to return a single hash ref that overrides
	   the arguments of the new method. However, command line arguments in
	   turn take precedence over the config file. See the "CONFIGURATION
	   FILE" section below for details on the config file.

       debug (--debug)
	   Turn debugging mode on. Mainly this asserts that logging messages
	   of level "debug" are created.

       facility (--facility=mode)
	   (UNIX only) Facility to use for Sys::Syslog. The default is daemon.

       group (--group=gid)
	   After doing a bind(), change the real and effective GID to the
	   given.  This is usefull, if you want your server to bind to a priv‐
	   ileged port (<1024), but don't want the server to execute as root.
	   See also the --user option.

	   GID's can be passed as group names or numeric values.

       localaddr (--localaddr=ip)
	   By default a daemon is listening to any IP number that a machine
	   has. This attribute allows to restrict the server to the given IP

       localport (--localport=port)
	   This attribute sets the port on which the daemon is listening. It
	   must be given somehow, as there's no default.

       logfile (--logfile=file)
	   Be default logging messages will be written to the syslog (Unix) or
	   to the event log (Windows NT). On other operating systems you need
	   to specify a log file. The special value "STDERR" forces logging to
	   stderr. See Net::Daemon::Log for details.

       mode (--mode=modename)
	   The server can run in three different modes, depending on the envi‐

	   If you are running Perl 5.005 and did compile it for threads, then
	   the server will create a new thread for each connection. The thread
	   will execute the server's Run() method and then terminate. This
	   mode is the default, you can force it with "--mode=threads".

	   If threads are not available, but you have a working fork(), then
	   the server will behave similar by creating a new process for each
	   connection.	This mode will be used automatically in the absence of
	   threads or if you use the "--mode=fork" option.

	   Finally there's a single-connection mode: If the server has
	   accepted a connection, he will enter the Run() method. No other
	   connections are accepted until the Run() method returns (if the
	   client disconnects).	 This operation mode is usefull if you have
	   neither threads nor fork(), for example on the Macintosh. For
	   debugging purposes you can force this mode with "--mode=single".

       pidfile (--pidfile=file)
	   (UNIX only) If this option is present, a PID file will be created
	   at the given location. Default is to not create a pidfile.

       user (--user=uid)
	   After doing a bind(), change the real and effective UID to the
	   given.  This is usefull, if you want your server to bind to a priv‐
	   ileged port (<1024), but don't want the server to execute as root.
	   See also the --group and the --chroot options.

	   UID's can be passed as group names or numeric values.

       version (--version)
	   Supresses startup of the server; instead the version string will be
	   printed and the program exits immediately.

       The configuration file is just that of RPC::PlServer or Net::Daemon
       with some additional attributes in the client list.

       The config file is a Perl script. At the top of the file you may
       include arbitraty Perl source, for example load drivers at the start
       (usefull to enhance performance), prepare a chroot environment and so

       The important thing is that you finally return a hash ref of option
       name/value pairs. The possible options are listed above.

       All possibilities of Net::Daemon and RPC::PlServer apply, in particular

       Host and/or User dependent access control
       Host and/or User dependent encryption
       Changing UID and/or GID after binding to the port
       Running in a chroot() environment

       Additionally the server offers you query restrictions. Suggest the fol‐
       lowing client list:

	   'clients' => [
	       { 'mask' => '^admin\.company\.com$',
		 'accept' => 1,
		 'users' => [ 'root', 'wwwrun' ],
		 'mask' => '^admin\.company\.com$',
		 'accept' => 1,
		 'users' => [ 'root', 'wwwrun' ],
		 'sql' => {
		      'select' => 'SELECT * FROM foo',
		      '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




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

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
       programm 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
		       # the 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 detailled informations
			       # 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

       Testing the connection from a remote machine

       Call a programm "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 '/'...):

	       informationdesk@dbi...> /
	       [1 rows of 1 fields returned]

       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",

	       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);
	       &show_result ($cur);

	       my $sql = "search_area";
	       printf "%s\n%s\n%s\n", "="x40, $sql, "="x40;
	       my $cur = $dbh->prepare($sql);
	       &show_result ($cur);

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


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

		       my $rownum = 0;
		       while (my @row = $cur->fetchrow_array()) {
			       printf "Row is: %s\n", join(", ",@row);
			       if ($rownum++ > 5) {
				       print "... and so on\n";

       The result

	       C:\>perl oratest.pl informationdesk xxx
	       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
	       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
	       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

       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

       * "mask" is a perl regular expression against the plain ip-address of
       the machine which wishes to connect _or_ the reverse-lookup from a
       * "accept" tells the dbiproxy-server wether ip-adresse like in "mask"
       are allowed to connect or not (0/1)
       * "users" is a reference to a list of usernames which must be matched,
       this is NOT a regular expression.

       Controlling which SQL-statements are allowed

       You can put every SQL-statement you like in simply ommiting "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);
	       # 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);


       * I don't know how to restrict users to special databases.
       * I don't know how to pass query-parameters via dbish

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

				 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.

       dbiproxy, DBD::Proxy, DBI, RPC::PlServer, RPC::PlClient, Net::Daemon,
       Net::Daemon::Log, Sys::Syslog, Win32::EventLog, syslog

perl v5.8.8			  2007-05-13		   DBI::ProxyServer(3)

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