| DBI::ProxyServer - a server for the DBD::Proxy driver |
DBI::ProxyServer - a server for the DBD::Proxy driver
use DBI::ProxyServer;
DBI::ProxyServer::main(@ARGV);
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 useful 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.
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 the RPC::PlServer manpage. See the Net::Daemon manpage. Available options include
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.
GID's can be passed as group names or numeric values.
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 useful if you have neither threads nor fork(),
for example on the Macintosh. For debugging purposes you can force this
mode with ``--mode=single''.
UID's can be passed as group names or numeric values.
DBI::ProxyServer is built on the RPC::PlServer manpage which is, in turn, built on the Net::Daemon manpage.
You should refer to the Net::Daemon manpage for how to shutdown the server, except that you can't because it's not currently documented there (as of v0.43). The bottom-line is that it seems that there's no support for graceful shutdown.
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 arbitrary Perl source, for example load drivers at the start (useful 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
chroot() environmentAdditionally 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
$sth->prepare("insert");
which in fact are ``SELECT * FROM foo'' or ``INSERT INTO foo VALUES (?, ?, ?)''.
This section tells you how to restrict a DBI-Proxy: Not every user from every workstation shall be able to execute every query.
There is a perl program ``dbiproxy'' which runs on a machine which is able to connect to all the databases we wish to reach. All Perl-DBD-drivers must be installed on this machine. You can also reach databases for which drivers are not available on the machine where you run the program querying the database, e.g. ask MS-Access-database from Linux.
Create a configuration file ``proxy_oracle.cfg'' at the dbproxy-server:
{
# This shall run in a shell or a DOS-window
# facility => 'daemon',
pidfile => 'your_dbiproxy.pid',
logfile => 1,
debug => 0,
mode => 'single',
localport => '12400',
# Access control, the first match in this list wins!
# So the order is important
clients => [
# hint to organize:
# the most specialized rules for single machines/users are 1st
# then the denying rules
# then the rules about whole networks
# rule: internal_webserver
# desc: to get statistical information
{
# this IP-address only is meant
mask => '^10\.95\.81\.243$',
# 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
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]
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;
}
my $rownum = 0;
while (my @row = $cur->fetchrow_array()) {
printf "Row is: %s\n", join(", ",@row);
if ($rownum++ > 5) {
print "... and so on\n";
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
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
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);
...
the RPC::PlServer manpage used underneath is not secure due to serializing and deserializing data with the Storable manpage module. Use the proxy driver only in trusted environment.
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.
dbiproxy, the DBD::Proxy manpage, the DBI manpage, the RPC::PlServer manpage, the RPC::PlClient manpage, the Net::Daemon manpage, the Net::Daemon::Log manpage, the Sys::Syslog manpage, the Win32::EventLog manpage, syslog
| DBI::ProxyServer - a server for the DBD::Proxy driver |