Re: Prepending 'exec' to proxy command automatically

[Konstantin Tokarev]

18.12.2015, 16:24, "Matt Johnston" :
> On Wed, Dec 16, 2015 at 04:32:03PM +0300, Konstantin Tokarev wrote:
>>  08.12.2015, 21:00, "Konstantin Tokarev" :
>>  > If dbclient is given proxy command which does not start with exec, shell 
>> process is lingering alongside proxy command process. However, I've found 
>> that OpenSSH client (ProxyCommand option) prepends exec automatically.
>>  >
>>  > I think it would be convenient if dbclient added exec by default, but 
>> this will break if someone is already using explicit exec in -J argument. 
>> Note that OpenSSH client also breaks with exec.
>>  >
>>  > So options are:
>>  >
>>  > 1. Just prepend exec to all proxy commands and make too clever people fix 
>> their scripts.
>>  > 2. Check if proxy command starts with exec, if not, prepend it.
>>  > 3. Add separate -o ProxyCommand option prepending exec (it also should 
>> substitute %h, %p, and %r to be compatible with OpenSSH). Leave -J as is for 
>> compatibility but mark it as deprecated.
>>  >
>>  > What is the best way?
>
> Sorry, missed this mail originally. I think 1 is best, I've
> pushed that as
> https://secure.ucc.asn.au/hg/dropbear/rev/f7d565054e5f

Why not use asprintf? I see scpmisc.c already uses vasprintf.


> Interestingly bash and zsh seem to avoid the lingering shell
> themselves without "exec". dash works for testing.

I'm using busybox shell (and I guess it's the most popular shell choice among 
dropbear users ;)

-- 
Regards,
Konstantin

Re: Prepending 'exec' to proxy command automatically

[Matt Johnston]

On Wed, Dec 16, 2015 at 04:32:03PM +0300, Konstantin Tokarev wrote:
> 08.12.2015, 21:00, "Konstantin Tokarev" :
> > If dbclient is given proxy command which does not start with exec, shell 
> > process is lingering alongside proxy command process. However, I've found 
> > that OpenSSH client (ProxyCommand option) prepends exec automatically.
> >
> > I think it would be convenient if dbclient added exec by default, but this 
> > will break if someone is already using explicit exec in -J argument. Note 
> > that OpenSSH client also breaks with exec.
> >
> > So options are:
> >
> > 1. Just prepend exec to all proxy commands and make too clever people fix 
> > their scripts.
> > 2. Check if proxy command starts with exec, if not, prepend it.
> > 3. Add separate -o ProxyCommand option prepending exec (it also should 
> > substitute %h, %p, and %r to be compatible with OpenSSH). Leave -J as is 
> > for compatibility but mark it as deprecated.
> >
> > What is the best way?

Sorry, missed this mail originally. I think 1 is best, I've
pushed that as
https://secure.ucc.asn.au/hg/dropbear/rev/f7d565054e5f
Interestingly bash and zsh seem to avoid the lingering shell
themselves without "exec". dash works for testing.

Cheers,
Matt

Re: Prepending 'exec' to proxy command automatically

[Konstantin Tokarev]

08.12.2015, 21:00, "Konstantin Tokarev" :
> If dbclient is given proxy command which does not start with exec, shell 
> process is lingering alongside proxy command process. However, I've found 
> that OpenSSH client (ProxyCommand option) prepends exec automatically.
>
> I think it would be convenient if dbclient added exec by default, but this 
> will break if someone is already using explicit exec in -J argument. Note 
> that OpenSSH client also breaks with exec.
>
> So options are:
>
> 1. Just prepend exec to all proxy commands and make too clever people fix 
> their scripts.
> 2. Check if proxy command starts with exec, if not, prepend it.
> 3. Add separate -o ProxyCommand option prepending exec (it also should 
> substitute %h, %p, and %r to be compatible with OpenSSH). Leave -J as is for 
> compatibility but mark it as deprecated.
>
> What is the best way?

Matt, what do you think?

-- 
Regards,
Konstantin

Prepending 'exec' to proxy command automatically

[Konstantin Tokarev]

If dbclient is given proxy command which does not start with exec, shell 
process is lingering alongside proxy command process. However, I've found that 
OpenSSH client (ProxyCommand option) prepends exec automatically.

I think it would be convenient if dbclient added exec by default, but this will 
break if someone is already using explicit exec in -J argument. Note that 
OpenSSH client also breaks with exec.

So options are:

1. Just prepend exec to all proxy commands and make too clever people fix their 
scripts.
2. Check if proxy command starts with exec, if not, prepend it.
3. Add separate -o ProxyCommand option prepending exec (it also should 
substitute %h, %p, and %r to be compatible with OpenSSH). Leave -J as is for 
compatibility but mark it as deprecated.

What is the best way?

-- 
Regards,
Konstantin