From: jvoisin <julien.voisin@dustri.org>
To: musl@lists.openwall.com
Cc: jvoisin <julien.voisin@dustri.org>
Subject: Re: [musl] [PATCH] Zero the leading stack canary byte
Date: Mon, 13 Dec 2021 13:24:38 +0100 [thread overview]
Message-ID: <cca0e62d-3798-2d7b-95f2-ec0d638b16ae@dustri.org> (raw)
In-Reply-To: <20211212193502.GF7074@brightrain.aerifal.cx>
> As written this patch assumes a 64-bit uintptr_t, which isn't ok.
> Indeed 56 bits should be fine on a 64-bit arch, but dropping from 32
> to 24 on a 32-bit arch severely weakens the protection. So it probably
> needs to be conditional on 64-bit.
Will do.
> Also, zeroing the first byte means we can no longer catch buffer
> overflows of the form "off-by-one string length". This seems
> unfortunate. Putting the 0 byte at the end would solve that at the
> expense of allowing the canary value to be leaked via missing
> termination bugs, and overall I would lean towards catching actual
> buffer overflow bugs vs stopping canary leaks.
As discussed on IRC, what about zero'ing the second byte instead? This
would allow to catch overflows, as well as preventing canary
leaks/overwrite via string-manipulating functions.
next prev parent reply other threads:[~2021-12-13 12:26 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-12 18:34 jvoisin
2021-12-12 19:35 ` Rich Felker
2021-12-13 12:24 ` jvoisin [this message]
2021-12-13 14:23 ` Rich Felker
2021-12-13 20:05 ` jvoisin
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