[MPlayer-dev-eng] [PATCH] fix SAMI parsing

[Reimar Döffinger]

On Sun, Jun 06, 2010 at 07:24:46PM -0400, hyc at highlandsun.com wrote:
> On Mon, Jun 07, 2010 at 12:26:33AM +0200, Reimar D?ffinger wrote:
> > On Sun, Jun 06, 2010 at 02:51:29PM -0700, Howard Chu wrote:
> > 
> > > +		uint32_t c = strtol(s+2, &s, 0);
> > > +		uint8_t tmp;
> > > +		PUT_UTF8(c, tmp, *p++ = tmp;)
> > > +		if (*s == ';') s++; }
> > 
> > I'm sorry, but I think you'll have to somehow "prove"
> > this is not a security issue.
> > Checking and documenting that PUT_UTF8 will never write
> > more than we read might be possible.
> > Or just "blindly" checking we still have at least 8 bytes
> > free should do as well.
> 
> Not necessary. Decimal numbers encode only 3.25 bits per byte, while UTF-8 encodes 7 bits per byte. This conversion will always fit.

Given that 3.25 bits just don't exist, it obviously is not that easy.
And you forgot another case as well: negative numbers.
This kind of thing just can't be done hand-wavy like that, or you'll
always miss a case.