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Date: Fri, 23 Aug 2013 22:23:45 +0800
From: Roy <>
Subject: Re: [PATCH] implement privmode support in dash

On Fri, 23 Aug 2013 19:40:31 +0800, "Jérémie Courrèges-Anglas"  
<> wrote:

> Also,
> Tavis Ormandy <> writes:
> [...]
>>> Apart from that, it is better to check the return value from setuid()
>>> and similar functions. In particular, some versions of Linux may fail
>>> setuid() for [EAGAIN], leaving the process running with the same
>>> privileges.
>> I don't think this is true anymore, but I have no strong objection to
>> adding it, so long as it's noted that bash and pdksh do not do this.
> Just for reference, from mksh:


BTW it is just changed in cvs. Log message:

Commit ID:	10052176CB912FE954B
Module name:	src
Changes by:	2013/08/23 14:07:41

Modified files:
	distrib/special/mksh: Makefile
	bin/mksh       : Makefile check.t misc.c mksh.1 sh.h

Log message:
SECURITY: Unbreak “set +p”, broken by OpenBSD ksh change.

TODO: I am seriously considering following Chet and changing
the way this works, by explicitly dropping privs unless the
shell is run with -p. Every other shell does it like mksh,
except Heirloom sh, which on the other hand doesn’t know any
explicit set -p or set +p (though it doesn’t know set +foo
for any foo either).

┌──┤ QUESTION: Do we need the ability to do this:
│ tg@...u:~ $ ./suidmksh -p -c 'whoami; set +p; whoami'
│ root
│ tg

If not, I’m seriously considering to drop set ±p as well,
only parse -p on the command line, with +p being the default,
and dropping FPRIVILEGED.

Thanks to RT for noticing and jilles for initial follow-up
discussion, as well as Chet Ramey for doing the sane/secure
thing instead of following Debian.

To generate a diff of this changeset, execute the following commands:
cvs -R rdiff -kk -upr1.71 -r1.72 src/distrib/special/mksh/Makefile
cvs -R rdiff -kk -upr1.645 -r1.646 src/bin/mksh/
cvs -R rdiff -kk -upr1.124 -r1.125 src/bin/mksh/Makefile
cvs -R rdiff -kk -upr1.630 -r1.631 src/bin/mksh/check.t
cvs -R rdiff -kk -upr1.214 -r1.215 src/bin/mksh/misc.c
cvs -R rdiff -kk -upr1.320 -r1.321 src/bin/mksh/mksh.1
cvs -R rdiff -kk -upr1.668 -r1.669 src/bin/mksh/sh.h

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