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Tim Bunce

NAME

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

SYNOPSIS

    use DBI::ProxyServer;
    DBI::ProxyServer::main(@ARGV);

DESCRIPTION

DBI::Proxy Server is a module for implementing a proxy for the DBI proxy driver, DBD::Proxy. It allows access to databases over the network if the DBMS does not offer networked operations. But the proxy server might be usefull for you, even if you have a DBMS with integrated network functionality: It can be used as a DBI proxy in a firewalled 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 encryption and a similar configuration file. DBI::ProxyServer adds the possibility 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".

OPTIONS

When calling the DBI::ProxyServer::main() function, you supply an array of options. (@ARGV, the array of command line options is used, if you don't.) 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(3). See Net::Daemon(3). 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, $dir;
    }
    link("$unixsockdir/$unixsockfile",
         "$rootdir$unixsockdir/$unixsockfile");
    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.

clients

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. See "Access control" below.

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 (3). 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 privileged 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 number.

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(3) for details.

mode (--mode=modename)

The server can run in three different modes, depending on the environment.

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.

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 privileged 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.

CONFIGURATION FILE

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 on.

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 following 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

    $sth->prepare("select");

or

    $sth->prepare("insert");

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

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.

SEE ALSO

dbiproxy(1), DBD::Proxy(3), DBI(3), RPC::PlServer(3), RPC::PlClient(3), Net::Daemon(3), Net::Daemon::Log(3), Sys::Syslog(3), Win32::EventLog(3), syslog(2)