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Date: Mon, 29 May 2023 21:10:59 +0200
From: Jₑₙₛ Gustedt <jens.gustedt@...ia.fr>
To: Rich Felker <dalias@...c.org>
Cc: musl@...ts.openwall.com
Subject: Re: changes for scanf in C23
Rich,
on Mon, 29 May 2023 11:59:29 -0400 you (Rich Felker <dalias@...c.org>)
wrote:
> On Mon, May 29, 2023 at 12:32:02PM +0200, Jₑₙₛ Gustedt wrote:
> > Hi,
> > we already discussed this but it doesn't seem that we have come to a
> > conclusion.
> >
> > The problem is that for C23 semantics of several string to integer
> > conversion functions change: a 'b' or 'B' that previously was the
> > stop condition for integer parsing may become part of the integer
> > string. This concerns all `scanf` and `strto` derivatives.
> >
> > This is probably not a problem for most applications that parse
> > strings to integers, but it could be in some situations, and in
> > particular it could open vulnerabilities. E.g network addresses that
> > are read with base `0` (musl does this at some point to allow to
> > have decimal or hex strings) could be open to attacks, once people
> > start using binary encodings for integers more often. Another
> > scenario where this could lead to harm is automatically produced
> > output that is automatically scanned, and where nobody previously
> > took care of proper word boundaries.
> >
> > My current idea is to have two sets of these functions, one that has
> > the old semantics and one that has the new.
>
> This was rejected already in the first proposal (thread here):
>
> Message-ID: <20230503000045.GU4163@...ghtrain.aerifal.cx>
> https://www.openwall.com/lists/musl/2023/05/03/1
>
> "There are not going to be different versions of scanf/strto*
> because there's just no way to do that in a conforming way..."
Alright, saves me a lot of trouble. I'll forward all complaints by
users to you ;-)
Jₑₙₛ
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