mod_proxy/2770: FTP proxy over firewall fails

[Andreas Pflug <Pf...@It-Warehouse.DE>]

>Number:         2770
>Category:       mod_proxy
>Synopsis:       FTP proxy over firewall fails
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          change-request
>Submitter-Id:   apache
>Arrival-Date:   Mon Aug  3 09:50:02 PDT 1998
>Last-Modified:
>Originator:     Pflug@It-Warehouse.DE
>Organization:
apache
>Release:        1.3.0
>Environment:
Linux 2.0.34
>Description:
I'm running Apache as proxy on a firewall blocking connections between unknown ports. FTP transfer to eg. ftp.microsoft.com will establish a PASV connection between two unknown ports if firewalling is disabled, but fail otherwise. I commented out the PASV section in proxy_ftp.c (line 770 "try to setup PASV first" to line 846 "try the regular way") with some success (ftp.netscape.com would work, the data connection was proxy:unknown to ftp.nescape.com:21 as expected). With ftp.microsoft.com, a connection between proxy:21 and ftp.microsoft.com:21 was established, but the browser will simply time out. No error_log entry.
>How-To-Repeat:
access (any) ftp-server when only connections from/to well-known ports (20, 21) are allowed.
>Fix:
Configuration option: use well-known ports only; try regular mode first, then PASV
>Audit-Trail:
>Unformatted:
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