On Fri, Jul 04, 2014 at 08:21:15AM +0200, Otto Moerbeek wrote:
> On Thu, Jul 03, 2014 at 11:35:15PM +0200, Kurt Roeckx wrote:
> 
> > On Thu, Jul 03, 2014 at 09:28:47PM +0100, Ben Laurie wrote:
> > > On 3 July 2014 20:06, Kurt Roeckx via RT <[email protected]> wrote:
> > > > On Thu, Jul 03, 2014 at 07:51:28PM +0200, Toralf F?rster via RT wrote:
> > > >> I think cppcheck is right here in void DES_ofb64_encrypt(), line 84, 85
> > > >> and 96, or ?:
> > > >>
> > > > The line before that:
> > > >
> > > >         dp=d;
> > > >>         l2c(v0,dp);<--- Uninitialized variable: d
> > > >>         l2c(v1,dp);<--- Uninitialized variable: d
> > > >>         while (l--)
> > > >>                 {
> > > >>                 if (n == 0)
> > > >>                         {
> > > >>                         DES_encrypt1(ti,schedule,DES_ENCRYPT);
> > > >>                         dp=d;
> > > >>                         t=ti[0]; l2c(t,dp);
> > > >>                         t=ti[1]; l2c(t,dp);
> > > >>                         save++;
> > > >>                         }
> > > >>                 *(out++)= *(in++)^d[n];<--- Uninitialized variable: d
> > > >>                 n=(n+1)&0x07;
> > > >>                 }
> > > >
> > > > d is uninitialized, but it's being written to, not read from,
> > > > so I don't see a problem with this.
> > > 
> > > What?
> > 
> > So l2c is:
> > #define l2c(l,c)        (*((c)++)=(unsigned char)(((l))&0xff), \
> >                          *((c)++)=(unsigned char)(((l)>> 8L)&0xff), \
> >                          *((c)++)=(unsigned char)(((l)>>16L)&0xff), \
> >                          *((c)++)=(unsigned char)(((l)>>24L)&0xff))
> > 
> > It reads v0 and v1 and writes to d (dp).  d being uninitialized
> > shouldn't be an issue.  Or am I missing something?
> 
> Yes, c (which is d) is both incremented and dereferenced. 

So we have:
DES_cblock d;
which as far as I know really is:
unsigned char d[8];

and:
register unsigned char *dp=d;
*((dp)++) = foo;

d is a valid pointer, but the content it points to is
uninitialized.  We end up writing to d[0], d[1], ..., d[7].  I
don't see us reading it, nor do I see a problem with it.


Kurt

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