NAME
proxycheck — open proxy server checker
SYNOPSYS
proxycheck options host[:proto_port_spec]...
DESCRIPTION
proxycheck is a simple open proxy checking tool which is capable to
quickly discovery open proxy servers on many hosts. It’s primary goal
is to detect an open proxy server in order to prevent it’s abuse by
various "bad guys", mostly spammers. Having a wide-open proxy service
running on a publicaly accessible network is a very bad idea nowadays,
and proxycheck may be used to find such system in order to be able to
either secure a system, or to refuse servicing it until it will be
secured properly.
In order to determine if a given host is running an open proxy service,
proxycheck tries to connect to a given destination system via a host
and perform some actions, trying to talk with the destination system.
If a talk is successeful, proxycheck assumes the proxy service is
running and wide-open.
proxycheck supports all commonly used proxy protocols, namely, HTTP
CONNECT method, SOCKS versions 4 and 5, and Wingate "telnet"‐style
proxies. In future, support for more protocols may be added.
Please note that with current number of various trojan horses
cicrulating around, each opening a proxy on a random port, it is not
really enouth to probe for standard (in whatever reason) ports built
into the proxycheck. Instead, it is highly recommended to use a list
of currently active ports maintained by several people on the ’net.
OPTIONS
The following command-line options are recognized:
-h print a short help and exit.
-v increase the verbosity level. All debugging messages will go to
standard error stream.
-d deshost:destport (required)
try to establish a proxied connection to the given dsthost, port
dstport. This option is required.
-c check[:params] (required)
the "method" proxycheck will use when talking to a destination
system to determine if a proxy is open or not. Interpretation
of params is check-dependant. This option is required. Several
methods are available:
chat:sendstr:expectstr
Try to perform simple "chat" with the destination system:
send the string given as sendstr and wait for expectstr
on output. If sendstr is empty, proxycheck will send the
proxy parameters in the form
protocol:ip-address:portnumber
to the remote system. Proxy assumed to be open if
expectstr is found.
dsbl (no parameters accepted)
try to submit all found proxies to the DSBL.org-like
system, see http://dsbl.org/ for more details. All the
parameters required (username, password, recipient
address, cookie server, ...) are expected to be found in
environment variables. Run proxycheck with -h option to
see a list of recognized variables and their default
values. By default, proxycheck will anonimously submit
all found proxies to unconfirmed.dsbl.org (which isn’t
very useful). For trusted DSBL user, at least DSBL_USER
and DSBL_PASS variables should be set properly.
-p proto_port_spec
specifies protocol and ports to connect to. If not given,
proxycheck will try it’s built-in default list. This option may
be specified more than once. See below for proto_port_spec.
If proto_port_spec is specified for a single host to check, it
applies to that host only, and no protocols/ports in default
list will be checked for that host.
-D do not reset default port list when using -p option, but prepend
new ports to it instead.
-a use more "advanced" ports/protocols. The more -a’s given, the
more ports/protocols will be probed. For a complete list of all
ports and protocols and their level, execute proxycheck with -h
option.
-t timeout
a timeout, in secounds, for every operation. Default value is
30 secounds. The timer starts at the connection attempt to the
proxy itself, after sending the "connect" command to the proxy
and so on.
-m maxconn
Do not attempt to make more than maxconn parallel connections.
By default, maximum number of parallel connections limited by
the operating system and on most systems it is around 1000.
-M maxhconn
Do not make more than maxhconn parallel connections to the same
host (default is unlimited). This may be useful for overloaded
proxies which can’t handle many parallel connections using
different ports/protocols, but may significantly slow down the
whole process.
-s when an open proxy is found on a given IP, stop probing for
other ports/protocols for this IP. Best used when many IPs are
tested, and/or with -M option. This is because currently,
proxycheck will not make any new connections to such host, but
will wait for already active connections to complete.
-b bindaddr
use bindaddr as a source address for all outgoing connections.
-n write a line about definitely closed proxies to stdout in
additional to writing about open proxies, in a form
127.0.0.1 http:8080 closed
-x print extended proxy information (proxy-agent and the like) if
available. This will be on the same "open" (or "closed" with
-n) line, last, enclosed in square brackets [].
-i filename
read list of hosts to check from a given file filename (in
addition to command line), or from stdin if filename if ‘-’.
Protocol and Port specification
Proxy protocols and ports to try (proto_port_spec) specified using the
following syntax:
[proto:][port,port,port]
like:
hc:3128,8080 (http protocol on ports 3128 and 8080)
hc: (default list of ports for http protocol)
3128 (try http protocol on standard http port 3128)
1234 (try all protocols on non-standard port 1234)
Run proxycheck -h to see a list of supported protocols and default
ports.
USAGE
Simplest usage of proxycheck is to try to connect to e.g. your own
mailserver with chat check method. First, connect to your mailserver
on port 25 to see which line it outputs upon connection (SMTP greething
line), and use it with chat:
proxycheck -d yourmailserver.example.org:25 \
-c chat::greething ip.add.re.ss...
proxycheck will write a single line for every proto:port it finds to be
open on stdout, in the form:
127.0.0.3 hc:80 open
where 127.0.0.3 is an IP address of a host being tested, hc is the
protocol name (HTTP CONNECT, consult proxycheck -h for a full list of
protocols) and 80 is a port number where the proxy service is running.
In addition, if proxycheck is able to guess outgoing IP address of a
proxy as seen by a destination system, and if that address is different
from input proxycheck is connecting to, it will print this information
too on the same line, like:
127.0.0.2 hc:80 open 127.0.0.3
where 127.0.0.3 is outgoing IP addres of a multihomed/cascaded proxy as
reported by the destination system. This IP address is hint only,
there is no simple and reliable way currently exists for proxycheck to
determine that information. Proxycheck is able to parse a line sent by
remote system in -c chat mode — in this mode, proxycheck skips all
printable characters after expstr it found and searches for opening
‘[’, when tries to find closing ’]’ and interpret digits and dots in
between as an IP address which gets printed like above. If your
mailserver’s initial reply contains remote system’s IP, or if your
mailserver replies with remote system’s IP address to HELO/EHLO
command, this feature may be useful (in the last case, HELO command
should be specified in chat).
When -n option is specified, for proto:ports which aren’t running open
proxy service, and for which proxycheck is able to strongly determine
this, a line in the following format will be written:
127.0.0.4 hc:80 closed
Note however that in most cases there is no way to reliable determine
whenever a given service is not open: for example, an open proxy server
may be overloaded and refusing connections. In most cases, proxycheck
assumes proxy is in unknown state, only a few codes are recognized as
real indication of "closed" state.
When -x option is specified, there will be additional proxy info
written on the same line (if available), like:
127.0.0.2 hc:80 open 127.0.0.3 [AnalogX 3.1415926]
127.0.0.3 hc:80 open [AnalogX 3.1415926]
127.0.0.4 hc:80 closed [AnalogX 3.1415926]
One may see some detail of proxycheck’s operations giving sufficient
number of -v options in the command line. Verbosity level of 5
(-vvvvv) will show almost everything. All the debugging output will go
to the standard error stream and thus will not affect normal operations
(when you process proxycheck’s output using some script).
EXIT CODE
proxycheck will exit with code 100 if at least one open proxy server
was found. In case of incorrect usage, it will exit with code 1. If
no open proxies where found, proxycheck will return 0.
LICENSE
This program is free software. It may be used and distributed in the
terms of General Public License (GPL) version 2 or later.
AUTHOR
proxycheck written by Michael Tokarev <mjt@corpit.ru>. Latest version
of this utlilty may be found at
http://www.corpit.ru/mjt/proxycheck.html.
proxycheck(1)