From: Michael Tokarev (no email)
Date: Fri Nov 01 2002 - 07:58:29 EST
Just encountered yet another funny http "GET/CONNECT" proxy:
$telnet 211.90.175.195 8080
Trying 211.90.175.195...
Connected to 211.90.175.195.
Escape character is '^]'.
GET mail.corpit.ru:25 HTTP/1.0
554 Service unavailable; Client host [211.90.175.195] blocked using proxies.relays.monkeys.com; IP address [211.90.175.195] BLOCKED: See http://www.monkeys.com/anti-spam/filtering/proxies.html
502 Error: command not implemented
500 Error: bad syntax
ddd
502 Error: command not implemented
ddd
502 Error: command not implemented
ddd
502 Error: command not implemented
(ddd is what I typed). In the other words, this is almost transparent
http "GET/CONNECT" proxy - that is, instead of requested GET, we got
CONNECT and proxied connection.
Here is what was seen by postfix:
Transcript of session follows.
Out: 554 Service unavailable; Client host [211.90.175.195] blocked using
proxies.relays.monkeys.com; IP address [211.90.175.195] BLOCKED: See
http://www.monkeys.com/anti-spam/filtering/proxies.html
In: GET HTTP/1.0
Out: 502 Error: command not implemented
In:
Out: 500 Error: bad syntax
In: ddd
Out: 502 Error: command not implemented
In: ddd
Out: 502 Error: command not implemented
In: ddd
Out: 502 Error: command not implemented
Session aborted, reason: lost connection
I.e., the GET command was sent to smtp server.
There is more such examples. Like e.g. wingate's ftp proxy that
also allows to be abused this way (it sends USER command to smtp
server) - (I will not share information about it here).
Wietse, what I'm thinking of is - would it be OK to implement e.g.
smtpd_commands_maps parameter, where the key is a command received
by smtpd, and result is TERMINATE to terminate a session, or a reason?
This way, a generalized framework will be available that replaces
already existing one (when postfix closes SMTP session when it sees
email header instead of smtp command).
Thanks.
/mjt
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