linux-kernel - Re: [PATCH v5 01/10] capabilities: introduce CAP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 21 Jan 2020 20:30:54 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Stephen Smalley <sds@...ho.nsa.gov>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "james.bottomley@...senpartnership.com" 
        <james.bottomley@...senpartnership.com>,
        Serge Hallyn <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robert Richter <rric@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Song Liu <songliubraving@...com>,
        Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        linux-arm-kernel@...ts.infradead.org,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        oprofile-list@...ts.sf.net
Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel
 and user space


On 21.01.2020 17:43, Stephen Smalley wrote:
> On 1/20/20 6:23 AM, 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 perf_events, i915_perf
>> and other performance monitoring and observability subsystems.
>>
>> CAP_PERFMON intends to harden system security and integrity during system
>> performance monitoring and observability operations by decreasing attack
>> surface that is available to a CAP_SYS_ADMIN privileged process [1].
>> Providing 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 operation more secure.
>>
>> CAP_PERFMON intends to take over CAP_SYS_ADMIN credentials related to
>> system performance monitoring and observability operations and balance
>> 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."
>>
>> 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 embargoed hardware issues mitigation procedure [2].
>> The bugs in the software itself could 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>
>> ---
>>   include/linux/capability.h          | 12 ++++++++++++
>>   include/uapi/linux/capability.h     |  8 +++++++-
>>   security/selinux/include/classmap.h |  4 ++--
>>   3 files changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/capability.h b/include/linux/capability.h
>> index ecce0f43c73a..8784969d91e1 100644
>> --- a/include/linux/capability.h
>> +++ b/include/linux/capability.h
>> @@ -251,6 +251,18 @@ extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct
>>   extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
>>   extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
>>   extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns);
>> +static inline bool perfmon_capable(void)
>> +{
>> +    struct user_namespace *ns = &init_user_ns;
>> +
>> +    if (ns_capable_noaudit(ns, CAP_PERFMON))
>> +        return ns_capable(ns, CAP_PERFMON);
>> +
>> +    if (ns_capable_noaudit(ns, CAP_SYS_ADMIN))
>> +        return ns_capable(ns, CAP_SYS_ADMIN);
>> +
>> +    return false;
>> +}
> 
> Why _noaudit()?  Normally only used when a permission failure is non-fatal to the operation.  Otherwise, we want the audit message.

Some of ideas from v4 review.
Well, on the second sight, it defenitly should be logged for CAP_SYS_ADMIN.
Probably it is not so fatal for CAP_PERFMON, but personally 
I would unconditionally log it for CAP_PERFMON as well.
Good catch, thank you.

~Alexey