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Date:      Mon, 15 May 2017 15:37:09 -0400
From:      Nikolai Lifanov <lifanov@FreeBSD.org>
To:        Bryan Drewery <bdrewery@FreeBSD.org>, Konstantin Belousov <kostikbel@gmail.com>
Cc:        svn-src-head@freebsd.org, Alexey Dokuchaev <danfe@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org
Subject:   Re: svn commit: r318313 - head/libexec/rtld-elf
Message-ID:  <ec7b9dbc-ff4c-cafe-77d2-9c7442da7bd1@FreeBSD.org>
In-Reply-To: <0b218455-d104-04be-d133-285f81d93456@FreeBSD.org>
References:  <201705151848.v4FImwMW070221@repo.freebsd.org> <20170515185236.GB1637@FreeBSD.org> <20170515190030.GG1622@kib.kiev.ua> <2493cfd2-1fab-d4cd-523c-0bd7413b1c86@FreeBSD.org> <20170515192944.GI1622@kib.kiev.ua> <0b218455-d104-04be-d133-285f81d93456@FreeBSD.org>

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From: Nikolai Lifanov <lifanov@FreeBSD.org>
To: Bryan Drewery <bdrewery@FreeBSD.org>,
 Konstantin Belousov <kostikbel@gmail.com>
Cc: svn-src-head@freebsd.org, Alexey Dokuchaev <danfe@FreeBSD.org>,
 src-committers@freebsd.org, svn-src-all@freebsd.org
Message-ID: <ec7b9dbc-ff4c-cafe-77d2-9c7442da7bd1@FreeBSD.org>
Subject: Re: svn commit: r318313 - head/libexec/rtld-elf
References: <201705151848.v4FImwMW070221@repo.freebsd.org>
 <20170515185236.GB1637@FreeBSD.org> <20170515190030.GG1622@kib.kiev.ua>
 <2493cfd2-1fab-d4cd-523c-0bd7413b1c86@FreeBSD.org>
 <20170515192944.GI1622@kib.kiev.ua>
 <0b218455-d104-04be-d133-285f81d93456@FreeBSD.org>
In-Reply-To: <0b218455-d104-04be-d133-285f81d93456@FreeBSD.org>

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On 05/15/2017 15:32, Bryan Drewery wrote:
> On 5/15/2017 12:29 PM, Konstantin Belousov wrote:
>> On Mon, May 15, 2017 at 12:25:20PM -0700, Bryan Drewery wrote:
>>> On 5/15/2017 12:00 PM, Konstantin Belousov wrote:
>>>> On Mon, May 15, 2017 at 06:52:36PM +0000, Alexey Dokuchaev wrote:
>>>>> On Mon, May 15, 2017 at 06:48:58PM +0000, Konstantin Belousov wrote=
:
>>>>>> New Revision: 318313
>>>>>> URL: https://svnweb.freebsd.org/changeset/base/318313
>>>>>>
>>>>>> Log:
>>>>>>   Make ld-elf.so.1 directly executable.
>>>>>
>>>>> Does it mean that old Linux' trick of /lib/ld-linux.so.2 /bin/chmod=
 +x
>>>>> /bin/chmod would now be possible on FreeBSD as well?
>>>> Yes.
>>>>
>>>>> Does this have any security implications?
>>>> What do you mean ?
>>>>
>>>
>>> I think for 3rd-party distributions it may be a problem. At the very
>>> least it needs to be communicated clearly in release notes or UPDATIN=
G.
>>>
>>> Consider a downstream vendor who has support for signed binary
>>> executions.  If rtld allows a backdoor around exec(2) to run an unsig=
ned
>>> binary, that could be a problem for them.  It is on them to add suppo=
rt
>>> to exec(2) to validate the special case of execing rtld with an
>>> argument, or to just disable the feature in rtld from this commit.
>>
>> Note the undocumented O_VERIFY flag in open(2) from the patch.
>> This is very vendor-ish addition to request veriexec (?).
>>
>=20
> Ah nice.
>=20


Note, this already does the right thing with noexec filesystems:
# zfs create -o mountpoint=3D/mnt -o exec=3Doff tank/TEST
# cp /bin/sh /mnt/
# /mnt/sh
/mnt/sh: Permission denied.
# /libexec/ld-elf.so.1 /mnt/sh
/mnt/sh: mmap of data failed: Permission denied

- Nikolai Lifanov


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