Re: [PATCH 2/2] connect: improve check for plink to reduce false positives

From: Jeff King <peff@peff.net>
Date: Apr 23, 2015, 15:53 UTC
Message-ID: <20150423155304.GA26018@peff.net>
In-Reply-To: <b6b4da1f7735b834043375e3d8eaa331@www.dscho.org>

On Thu, Apr 23, 2015 at 08:50:17AM +0200, Johannes Schindelin wrote:

Show 9 quoted lines

> > +				tortoiseplink = tplink == ssh ||
> > +					(tplink && is_dir_sep(tplink[-1]));
> 
> Maybe have a helper function here? Something like
> `basename_matches(const char *path, const char *basename, int
> ignore_case)`? That would be easier to read (I have to admit that I
> had to wrap my head around the logic to ensure that tplink[-1] is
> valid; It is, but it requires more brain cycles to verify than I would
> like).

Yeah, I had a similar thought when reading the patch.

Show 5 quoted lines

> Also, I am really hesitant to just test the start of the basename; I
> would rather have an entire basename match so that something  like
> "PLinKoeln" would not match. (And of course, for Windows I would want
> that hypothetical `basename_matches()` function to allow basenames to
> end in `.exe` automatically).

What about "plink-0.83" that was mentioned earlier in the thread? I think that is the reason brian's patch stuck to matching the start and not the end. But I have no idea if that is actually a real thing, or just a hypothetical.

If I were writing from scratch, I would probably keep things as tight as possible, like:

  const char *base = basename(ssh);
  plink = !strcasecmp(base, "plink") ||
          !strcasecmp(base, "plink.exe");
  tplink = !strcasecmp(base, "tortoiseplink") ||
           !strcasecmp(base, "tortoiseplink.exe"));

but maybe that is too tight at this point in time; we don't really know what's out there and working (or maybe _we_ do, but _I_ do not :) ).

At any rate, brian's patch only looks for a dir-separator anywhere, not the actual basename. So:

  /path/to/plink/ssh

would match, and I'm not sure if that's a good thing or not. So yet another variant is to use basename(), and then just check that the basename starts with "plink" (to catch "plink.exe", "plink-0.83", etc). That avoids cruft in the intermediate path, and unless your actual binary is named PlinKoeln, it will not false positive on the example you gave.

-Peff