[vlc-devel] [PATCH] cli: fix line trimming with socket cli

[Rémi Denis-Courmont]

Hi,

On output side, there is a problrm my that garbage CR are inserted. This will indeed corrupt logs, especially if multipexing the standard error and standard output together, so we should remove the CR on non-Windows platforms.

Le 6 novembre 2020 10:48:40 GMT+02:00, Alexandre Janniaux <ajanni at videolabs.io> a écrit :
>Note that I don't care about supporting telnet protocol and its
>user management, control command and what else that I don't even
>know with this patch. That's not what it does. Telnet is
>exhibiting the issue and like Romain my main wonders are why we
>should care about parsing \r\n or \r characters at all,
>especially since it will likely break logs and rc output in
>scenario that were functionnal before.
>
>I also don't understand the position around telnet, its previous
>use case but that's probably something we should discuss with a
>smoother communication channel.
>
>Regards,
>--
>Alexandre Janniaux
>
>
>
>On Fri, Nov 06, 2020 at 01:20:23AM +0100, Pierre Ynard via vlc-devel
>wrote:
>> > This looks plain wrong. CR is not a special character, or
>specifically
>> > a line ending in a Unix CLI (main use of RC interface) or in
>> > netcat-type tools (secondary use with in Unix or TCP socket modes).
>>
>> What if you pipe commands from a file saved with CRLFs?
>>
>> Also, if I see correctly, the CLI outputs CRLFs (both C and lua). So
>umm
>> wouldn't it be rather strange if it didn't accept them in the input?
>>
>> > RC/CLI is *not* implementing the Telnet protocol. telnet is not for
>> > raw I/O. There's netcat et al for that.
>>
>> > The point is that you cannot use a Telnet client. VLC RC sends and
>> > receives raw UTF-8; that is simply not compatible with Telnet in
>> > either direction.
>>
>> > I'm not sure about the Telnet protocol specifically, but VLC RC and
>> > VLC Telnet interfaces are different modules.
>>
>> What do you mean with that about different modules? Telnet is a
>> transport whose main use case is indeed to provide access to a remote
>> CLI. There hasn't been any separate "telnet interface" since it was
>> merged into the lua CLI.
>>
>> Now if we consider your point about text encoding, as far as I can
>tell
>> there was never any consideration in the code about telnet being
>limited
>> to ASCII, so we could even argue that there has never been any VLC
>> interface actually implementing a telnet transport.
>>
>> It makes no sense to segregate this concern as if telnet was
>something
>> else's problem, not RC's. And we decided to fix regressions in the
>> CLI such as missing transports - not add regressions like CRLF going
>> unsupported. So logically, we should either port and fix telnet to
>> the C CLI, or consider that it's too broken and unwanted, and drop
>> it altogether from VLC - which would allow finally actually deleting
>> the redundant lua CLI. However, considering that the current telnet
>> interface is fine for lua but no good for the C CLI is a no go.
>>
>> > And Telnet clients don't support Unix sockets, which are the
>> > recommended access mean - for pretty damn obvious security reasons.
>>
>> Recommended by which authority, and in what way? I'm not aware of
>> anywhere stating that, and I'm not sure users are getting that
>message
>> either. If some given transports are recommended or discouraged,
>maybe
>> it could at least be stated in the their settings' help text.
>>
>> But let's talk about that. Unix sockets indeed allow easily setting
>> up some access control. But TCP sockets also allow setting up access
>> control with iptables or firewall rules. As for telnet, the prominent
>> difference in whatever telnet interface VLC offers is that it takes a
>> password. A simple password without channel encryption is considered
>> secure enough for the web interface, and unlike it telnet isn't
>> even open to cross-site attacks. Moreover, unlike the socket's file
>> permissions or TCP firewalling, telnet doesn't require external set
>> up or tools. So you could say it's actually the better choice on that
>> front!
>>
>> So what do we do with our offer of CLI transports?
>>
>> --
>> Pierre Ynard
>> "Une âme dans un corps, c'est comme un dessin sur une feuille de
>papier."
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