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Message-Id: <90735C03-0C34-49ED-A79A-EC0165C274CC@dwheeler.com>
Date: Thu, 29 Dec 2022 12:56:22 -0500
From: "David A. Wheeler" <dwheeler@...eeler.com>
To: oss-security@...ts.openwall.com
Cc: Demi Marie Obenour <demi@...isiblethingslab.com>,
Alejandro Colomar <alx.manpages@...il.com>,
Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [patch] proc.5: tell how to parse /proc/*/stat
correctly
> On Dec 29, 2022, at 11:43 AM, Alan Coopersmith <alan.coopersmith@...cle.com> wrote:
Another solution is to escape bytes that might cause trouble in this field, e.g., using %xx hexadecimal.
So space would be %20, ")" would be %41, control characters 1-31 would be %01 to %1f,
and (of course) "%" would be encoded as %25.
Basically, URL-encode / Percent-encode them. See: https://en.wikipedia.org/wiki/Percent-encoding
Technically this would be a userspace change, but only in cases where the system
would probably have done the wrong thing previously. It's okay if we break *attacker* workflows
as long as we don't break others'. An advantage of URL encoding is that,
like JSON, it's a well-known format. I might do something different if this was a new system,
but that seems like the least-impact approach while eliminating the problem.
--- David A .Wheeler
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