Re: [Xen-devel] [PATCH OSSTEST v7 01/15] TestSupport: Add helper to fetch a URL on a host

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-07-06 at 15:48 +0100, Ian Jackson wrote:
> Ian Campbell writes ("[PATCH OSSTEST v7 01/15] TestSupport: Add helper to 
> fetch a URL on a host"):
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > ---
> > v7: Quote $url and $path, switch to a heredoc to avoid resulting over
> >     long line
> ...
> 
> Last time I wrote:
> 
>   Do we care that this will break badly if the url contains shell
>   metacharacters ?  I think we may do.
> 
> but:
> 
> > +    $useproxy wget --progress=dot:mega -O \"$path\" \"$url\"
> 
> Did you try this with $path or $url containing $ or   or " or \ or ` or
> starting with - ?

No, I think I just hadn't thought very clearly enough about what you
meant.

> There are a fair few places in osstest where we're quite lax with this
> kind of thing, but (hopefully) only where the information definitely
> comes from the configuration (or some other trusted source).  A
> general helper like this ought to be robust against that kind of input
> (which may well mean failing, but it should not include potentially
> executing bits of the input or misinterpreting it as command line
> options to wget.
> 
> \Q may be of some help.

Really? I thought that escaped things at the Perl level, is that
sufficient for the shell stuff within the Perl too?

I suspect I just don't understand clearly enough what \Q actually does.

Ian.


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