PATCH: 'source environment' param and % token subs for'netbios name'

[Nicolas Williams]

On Fri, 28 Jan 2000, Jeremy Allison wrote:
> Richard Sharpe wrote: 
> 
> > This sort of feature is so important for HA that I am about to commit your 
> > patches to 2.0.7, if Jeremy hasn't already done it. 
> > 
> > If Jeremy doesn't like the patch, he can argue about it. 
> 
> Richard, 
> 
>         Please don't do it *quite* yet. I fully intend to 
> grab it and apply it for 2.0.7 (I emailed Nicolas and 
> told him so), but I want to do some work 
> on the popen() part of it first to make it paranoid and 
> bullet-proof first. I recognised how useful it was for HA 
> work as soon as I looked over it :-). 

Well, yes, popen() is a bit problematic. I wish there were a standard
restricted shell that one could force popen() to use. That said, if one
restricts oneself to source env parameters like this:

	source environment = /etc/smb.conf.sh|

or

	source environment = /etc/smb.conf.sh %$(SOME_ENV_VAR) |

and if one avoids using % tokens whose value is determined by the user
then all should be ok.

Remember also that 'source environment' only does anything when the file
containing it is being included.

So all in all using popen() here should be fairly safe, provided one
does not do stupid things with it...

There is one other caveat though: it is possible to have env vars whose
value would confuse env(1). For example:

% echo $FOO
foo BAR=baz
% echo $BAR

% ( eval echo \$FOO )
foo BAR=baz
% ( eval echo \$BAR )

% 
% export FOO
% env|egrep 'FOO|BAR'
FOO=foo
BAR=baz
% 

This is a limitation of the format of env(1)'s output. Something to keep
in mind.

> Cheers, 
> 
>         Jeremy. 


Nico
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