Hi Daniel,

Thanks for the prompt reply. It was that 2003 e-mail that prompted me to
ask these questions! You have confirmed what I feared. I thought in all
these years, something may have changed but you are right, FTP is hardly on
the rise. Unfortunately, I will have to hack something up (perhaps option
1) because I need it in an embedded system for "backwards compatibility".

I trimmed the response somewhat, preserving your conclusions.

Thanks for clarifying,

Carlos

On Wed, Nov 23, 2016 at 2:35 AM, Daniel Stenberg <daniel_at_haxx.se> wrote:

> On Wed, 23 Nov 2016, Carlos Rimola wrote:
>
> 1) What form of FTP Proxy (servers) does Libcurl support? (RFCs?). Any
>> specific examples like ftp-proxy or squid?
>>
>
> Amusingly enough, I answered almost this question already 13 years ago:
> https://curl.haxx.se/mail/archive-2003-04/0120.html
>
> Strictly speaking, there's no formal support for proxy in the FTP protocol
> at all. There are not RFCs for that and there's not even any proper
> informal standards.
>
> There are three ways to do proxying with FTP:
>
> 1 - abuse the existing FTP protocol but send data in "wrong" fields. Like
> pass in the actual remote host name as user:
>
> ftp://user%40remotehost:password@ftpproxyhost/path/to/remote/file
>
> 2 - just ask for a ftp:// URL over a HTTP proxy and hope for the best
>
> 3 - tunnel through a HTTP proxy with *PROXYTUNNEL which makes libcurl use
> CONNECT - this kind of operation is often blocked by HTTP proxies.
>
> is not Libcurl's issue but mainly the weak definition of FTP Proxy in the
>> RFCs? However RFC-1919 ("Classical versus Transparent IP Proxies") seems to
>> clear much of how to make FTP proxies operate.
>>
>
> RFC 1919 is over 20 years old and I can agree that it discusses how
> connections work for proxies but it certainly does not detail enough how an
> FTP proxy should work or be used by a client such as curl.
>
> I think people have managed to get pass with the above methods so nobody
> ever implemented support for other for further ftp-proxies. FTP is hardly a
> protocol on the rise these days which I suppose also helps explain the lack
> of interest.
>
> --
>
> / daniel.haxx.se
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Received on 2016-11-24