command: hashsum: md5sum reports wrong sum for the file named 4k.bin

[Sascha Hauer]

On Fri, Jan 05, 2018 at 09:17:30PM +0300, Peter Mamonov wrote:
> On Fri, Jan 05, 2018 at 12:44:19PM +0100, Sascha Hauer wrote:
> > Hi Peter,
> > 
> > On Thu, Dec 21, 2017 at 01:48:11PM +0300, Peter Mamonov wrote:
> > > On Wed, Dec 20, 2017 at 01:48:14PM +0300, Peter Mamonov wrote:
> > > > Hi,
> > > > 
> > > > The md5sum command reports wrong sum for a file named 4k.bin and, I guess, for 
> > > > other files named alike. Here are the commands to reproduce the bug:
> > > 
> > > The problem lays in __do_digest() function: 
> > >  - it initializes variables `start` and `size` at commands/digest.c:38
> > >  - then it calls parse_area_spec(*argv, &start, &size) at commands/digest.c:42
> > >  - parse_area_spec() returns error as it should, however it changes the value 
> > >  of the `start` at lib/misc.c:87.
> > >  - this causes digest algo to skip leading 4k of the data from the file.
> > > 
> > > I'm not quite sure what is the best solution:
> > >  - prevent parse_area_spec() from setting start if it fails?
> > >  - reinitialize start/size after unsuccessfull call to parse_area_spec()?
> > 
> > preventing parse_area_spec() from modifying start and size if it fails
> > seems like a good idea.
> > 
> > However, this doesn't solve the problem, does it? parse_area_spec()
> > only fails because the dot in 4k.bin is not valid, but if you name
> > the file only '4k' then parse_area_spec() won't fail.
> > The problem is that we cannot know whether '4k' is a file or an area.
> 
> You are right. However, there is no ambiguity in the "4k.bin" and similar 
> cases, so we can fix at least this obvious problem.

Indeed, so a patch for parse_area_spec() would be welcomed.

Sascha

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