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DBI::ProxyServer - a server for the DBD::Proxy driver
use DBI::ProxyServer;
DBI::ProxyServer::main(@ARGV);
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.
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' => $rootdir,
...
}
If you don't know chroot(), think of an FTP server where you can see a certain directory tree only after logging in. See also the --group and --user options.
GID's can be passed as group names or numeric values.
If you are running Perl 5.005 and did compile it for threads, then the server will create a new thread for each connection. The thread will execute the server's Run() method and then terminate. This mode is the default, you can force it with ``--mode=threads''.
If threads are not available, but you have a working fork(), then the server will behave similar by creating a new process for each connection. This mode will be used automatically in the absence of threads or if you use the ``--mode=fork'' option.
Finally there's a single-connection mode: If the server has accepted a connection, he will enter the Run() method. No other connections are accepted until the Run() method returns (if the client disconnects). This operation mode is usefull if you have neither threads nor fork(), for example on the Macintosh. For debugging purposes you can force this mode with ``--mode=single''.
UID's can be passed as group names or numeric values.
The config file is a Perl script. At the top of the file you may include arbitraty Perl source, for example load drivers at the start (usefull to enhance performance), prepare a chroot environment and so on.
The important thing is that you finally return a hash ref of option name/value pairs. The possible options are listed above.
All possibilities of Net::Daemon and RPC::PlServer apply, in particular
Additionally the server offers you query restrictions. Suggest the following client list:
'clients' => [
{ 'mask' => '^admin\.company\.com$',
'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
$sth->prepare("insert");
which in fact are ``SELECT * FROM foo'' or ``INSERT INTO foo VALUES (?, ?, ?)''.
There is a perl program ``dbiproxy'' which runs on a machine which is able to connect to all the databases we wish to reach. All Perl-DBD-drivers must be installed on this machine. You can also reach databases for which drivers are not available on the machine where you run the programm querying the database, e.g. ask MS-Access-database from Linux.
Create a configuration file ``proxy_oracle.cfg'' at the dbproxy-server:
{
# This shall run in a shell or a DOS-window
# facility => 'daemon',
pidfile => 'your_dbiproxy.pid',
logfile => 1,
debug => 0,
mode => 'single',
localport => '12400',
# Access control, the first match in this list wins!
# So the order is important
clients => [
# hint to organize:
# the most specialized rules for single machines/users are 1st
# then the denying rules
# the the rules about whole networks
# rule: internal_webserver
# desc: to get statistical information
{
# this IP-address only is meant
mask => '^10\.95\.81\.243$',
# 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
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]
# 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
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 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);
$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);
...
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.
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