Re: "command -p" does not correctly limit search to a safe PATH

[Jilles Tjoelker <jilles@stack.nl>]

On Fri, Sep 26, 2014 at 05:19:42PM +0800, Herbert Xu wrote:
> On Fri, Jul 19, 2013 at 09:49:31PM +0000, Harald van Dijk wrote:
> >
> > So, how about this, to be applied on top of my previous patch? It
> > defaults to using confstr() if available and reporting a hard error at
> > run time if that fails, but it can be configured to not use confstr(),
> > and/or fall back to a path specified at configuration time:

> Thanks for the patch.  But until someone who needs this complexity
> steps up, I'm going to stick with the simpler version below:

> [snip]
> diff --git a/src/var.h b/src/var.h
> index 79ee71a..872e2db 100644
> --- a/src/var.h
> +++ b/src/var.h
> @@ -107,7 +107,7 @@ extern const char defifsvar[];
>  extern const char defifs[];
>  #endif
>  extern const char defpathvar[];
> -#define defpath (defpathvar + 5)
> +#define defpath (defpathvar + 36)
>  
>  extern int lineno;
>  extern char linenovar[];

This needs a comment at the definition of defpathvar in var.c;
otherwise, someone changing the default path will subtly break command
-p without knowing. The number 36 is rather magic too, but it can be
found back through git history.

Alternatively, you could rely on the linker combining common string
constant endings: put in some #define for
"/usr/sbin:/usr/bin:/sbin:/bin" and make defpathvar a #define instead of
a const array.

-- 
Jilles Tjoelker