DBI::ProxyServer(3) User Contributed Perl Documentation DBI::ProxyServer(3)
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 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.
OPTIONS
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 useful 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.
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 useful, 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 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 useful 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 useful, 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)
Suppresses startup of the server; instead the version string will
be printed and the program exits immediately.
SHUTDOWN
DBI::ProxyServer is built on RPC::PlServer which is, in turn, built on
Net::Daemon.
You should refer to Net::Daemon 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.
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 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
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
$sth->prepare("insert");
which in fact are "SELECT * FROM foo" or "INSERT INTO foo VALUES (?, ?,
?)".
Proxyserver Configuration file (bigger example)
This section tells you how to restrict a DBI-Proxy: Not every user from
every workstation shall be able to execute every query.
There is a perl program "dbiproxy" which runs on a machine which is
able to connect to all the databases we wish to reach. All Perl-DBD-
drivers must be installed on this machine. You can also reach databases
for which drivers are not available on the machine where you run the
program querying the database, e.g. ask MS-Access-database from Linux.
Create a configuration file "proxy_oracle.cfg" at the dbproxy-server:
{
# This shall run in a shell or a DOS-window
# facility => 'daemon',
pidfile => 'your_dbiproxy.pid',
logfile => 1,
debug => 0,
mode => 'single',
localport => '12400',
# Access control, the first match in this list wins!
# So the order is important
clients => [
# hint to organize:
# the most specialized rules for single machines/users are 1st
# then the denying rules
# the the rules about whole networks
# rule: internal_webserver
# desc: to get statistical information
{
# this IP-address only is meant
mask => '^10\.95\.81\.243$',
# 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$',
accept => 0,
},
# rule: employee_workplace
# desc: get detailled information
{
# any IP-address is meant here
mask => '^10\.95\.81\.(\d+)$',
# 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
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]
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;
}
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
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
o "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.
o "accept" tells the dbiproxy-server wether ip-adresse like in "mask"
are allowed to connect or not (0/1)
o "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);
$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);
...
Problems
o I don't know how to restrict users to special databases.
o I don't know how to pass query-parameters via dbish
SECURITY WARNING
RPC::PlServer used underneath is not secure due to serializing and
deserializing data with Storable module. Use the proxy driver only in
trusted environment.
AUTHOR
Copyright (c) 1997 Jochen Wiedmann
Am Eisteich 9
72555 Metzingen
Germany
Email: joe AT 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, DBD::Proxy, DBI, RPC::PlServer, RPC::PlClient, Net::Daemon,
Net::Daemon::Log, Sys::Syslog, Win32::EventLog, syslog
perl v5.16.3 2014-06-10 DBI::ProxyServer(3)
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