Re: [PATCH v6 01/10] capabilities: introduce CAP_PERFMON to kernel and user space

[Alexey Budankov]

On 06.02.2020 21:30, Stephen Smalley wrote:
> 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@xxxxxxxxxxxxxxx>
>>>
>>> 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.

Ok. Thanks!

~Alexey