linux-kernel - Re: [PATCH v6 01/10] capabilities: introduce CAP

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Message-ID: <06cdca0e-65f2-b58d-a84e-5a1907aa9eb5@tycho.nsa.gov>
Date:   Thu, 6 Feb 2020 13:30:56 -0500
From:   Stephen Smalley <sds@...ho.nsa.gov>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        Serge Hallyn <serge@...lyn.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Will Deacon <will@...nel.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Stephane Eranian <eranian@...gle.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Jiri Olsa <jolsa@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        oprofile-list@...ts.sf.net
Subject: Re: [PATCH v6 01/10] capabilities: introduce CAP_PERFMON to kernel
 and user space

On 2/6/20 1:26 PM, Alexey Budankov wrote:
> 
> On 06.02.2020 21:23, Stephen Smalley wrote:
>> On 2/5/20 12:30 PM, Alexey Budankov wrote:
>>>
>>> Introduce CAP_PERFMON capability designed to secure system performance
>>> monitoring and observability operations so that CAP_PERFMON would assist
>>> CAP_SYS_ADMIN capability in its governing role for performance monitoring
>>> and observability subsystems.
>>>
>>> CAP_PERFMON hardens system security and integrity during performance
>>> monitoring and observability operations by decreasing attack surface that
>>> is available to a CAP_SYS_ADMIN privileged process [2]. Providing the access
>>> to system performance monitoring and observability operations under CAP_PERFMON
>>> capability singly, without the rest of CAP_SYS_ADMIN credentials, excludes
>>> chances to misuse the credentials and makes the operation more secure.
>>> Thus, CAP_PERFMON implements the principal of least privilege for performance
>>> monitoring and observability operations (POSIX IEEE 1003.1e: 2.2.2.39 principle
>>> of least privilege: A security design principle that states that a process
>>> or program be granted only those privileges (e.g., capabilities) necessary
>>> to accomplish its legitimate function, and only for the time that such
>>> privileges are actually required)
>>>
>>> CAP_PERFMON meets the demand to secure system performance monitoring and
>>> observability operations for adoption in security sensitive, restricted,
>>> multiuser production environments (e.g. HPC clusters, cloud and virtual compute
>>> environments), where root or CAP_SYS_ADMIN credentials are not available to
>>> mass users of a system, and securely unblocks accessibility of system performance monitoring and observability operations beyond root and CAP_SYS_ADMIN use cases.
>>>
>>> CAP_PERFMON takes over CAP_SYS_ADMIN credentials related to system performance
>>> monitoring and observability operations and balances amount of CAP_SYS_ADMIN
>>> credentials following the recommendations in the capabilities man page [1]
>>> for CAP_SYS_ADMIN: "Note: this capability is overloaded; see Notes to kernel
>>> developers, below." For backward compatibility reasons access to system
>>> performance monitoring and observability subsystems of the kernel remains
>>> open for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN capability
>>> usage for secure system performance monitoring and observability operations
>>> is discouraged with respect to the designed CAP_PERFMON capability.
>>>
>>> Although the software running under CAP_PERFMON can not ensure avoidance
>>> of related hardware issues, the software can still mitigate these issues
>>> following the official hardware issues mitigation procedure [2]. The bugs
>>> in the software itself can be fixed following the standard kernel development
>>> process [3] to maintain and harden security of system performance monitoring
>>> and observability operations.
>>>
>>> [1] http://man7.org/linux/man-pages/man7/capabilities.7.html
>>> [2] https://www.kernel.org/doc/html/latest/process/embargoed-hardware-issues.html
>>> [3] https://www.kernel.org/doc/html/latest/admin-guide/security-bugs.html
>>>
>>> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
>>
>> This will require a small update to the selinux-testsuite to correctly reflect the new capability requirements, but that's easy enough.
> 
> Is the suite a part of the kernel sources or something else?

It is external,
https://github.com/SELinuxProject/selinux-testsuite

I wasn't suggesting that your patch be blocked on updating the 
testsuite, just noting that it will need to be done.