linux-kernel - Re: [PATCH v22 01/12] landlock: Add object management

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Message-ID: <523d2141-e6f9-354d-d102-ae8345c84686@digikod.net>
Date:   Mon, 16 Nov 2020 22:36:17 +0100
From:   Mickaël Salaün <mic@...ikod.net>
To:     Pavel Machek <pavel@....cz>
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...capital.net>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Arnd Bergmann <arnd@...db.de>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Jann Horn <jannh@...gle.com>, Jeff Dike <jdike@...toit.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Richard Weinberger <richard@....at>,
        Shuah Khan <shuah@...nel.org>,
        Vincent Dagonneau <vincent.dagonneau@....gouv.fr>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        linux-security-module@...r.kernel.org, x86@...nel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v22 01/12] landlock: Add object management


On 16/11/2020 22:26, Pavel Machek wrote:
> Hi!
> 
>> A Landlock object enables to identify a kernel object (e.g. an inode).
>> A Landlock rule is a set of access rights allowed on an object.  Rules
>> are grouped in rulesets that may be tied to a set of processes (i.e.
>> subjects) to enforce a scoped access-control (i.e. a domain).
>>
>> Because Landlock's goal is to empower any process (especially
>> unprivileged ones) to sandbox themselves, we cannot rely on a
>> system-wide object identification such as file extended attributes.
> 
> 
>> +config SECURITY_LANDLOCK
>> +	bool "Landlock support"
>> +	depends on SECURITY
>> +	select SECURITY_PATH
>> +	help
>> +	  Landlock is a safe sandboxing mechanism which enables processes to
>> +	  restrict themselves (and their future children) by gradually
>> +	  enforcing tailored access control policies.  A security policy is a
>> +	  set of access rights (e.g. open a file in read-only, make a
>> +	  directory, etc.) tied to a file hierarchy.  Such policy can be configured
>> +	  and enforced by any processes for themselves thanks to dedicated system
>> +	  calls: landlock_create_ruleset(), landlock_add_rule(), and
>> +	  landlock_enforce_ruleset_current().
> 
> How does it interact with setuid binaries? Being able to exec passwd
> in a sandbox sounds like ... fun way to get root? :-).

It works like seccomp: if you run with CAP_SYS_ADMIN in the current
namespace, then SUID binaries may be allowed, otherwise if you use
PR_SET_NO_NEW_PRIVS, then executing a SUID binary is denied.

The 24th version is here:
https://lore.kernel.org/lkml/20201112205141.775752-1-mic@digikod.net/

> 
> Best regards,
> 								Pavel
> 								
>