Date: Mon, 15 May 2017 19:23:26 +0000 From: Alexey Dokuchaev <danfe@FreeBSD.org> To: Nikolai Lifanov <lifanov@FreeBSD.org> Cc: Konstantin Belousov <kib@FreeBSD.org>, svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r318313 - head/libexec/rtld-elf Message-ID: <20170515192326.GB28684@FreeBSD.org> In-Reply-To: <6c327032-9eb5-2b0a-39ed-2140144a5a0d@FreeBSD.org> References: <201705151848.v4FImwMW070221@repo.freebsd.org> <20170515185236.GB1637@FreeBSD.org> <6c327032-9eb5-2b0a-39ed-2140144a5a0d@FreeBSD.org>
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On Mon, May 15, 2017 at 03:09:33PM -0400, Nikolai Lifanov wrote: > On 05/15/2017 14:52, Alexey Dokuchaev wrote: > > 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? Does this have > > any security implications? > > This is a use case for fixing accidentally hosed /bin/chmod binary and > not some sort of an escalation thing. You will need to be root to do > this. Because /bin/chmod is owned by root, not because /libexec/ld-elf.so.1 is limiting execution to root only, or is it (I might have missed uid check in that patch [1], but at a quick glance I didn't see it). On a living system, there are plenty of other ways to restore missing +x on /bin/chmod as long as you can call chmod(2), from simple Python script down to manually crafting small binary in hex. > Likewise, with working chmod binary, you should be able to mark > binaries with write access executable. Well, it's not just about chmod(1), this opens what can be a can of worms and I want to know how big it is. ./danfe [1] Idea for security.bsd.ld_elf_exec_root_only sysctl(8)?
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