netdev - Re: [PATCH v19 06/23] LSM: Use lsmblob in security_secctx_to

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Date:   Tue, 28 Jul 2020 16:41:59 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     John Johansen <john.johansen@...onical.com>,
        casey.schaufler@...el.com, jmorris@...ei.org,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Cc:     linux-audit@...hat.com, keescook@...omium.org,
        penguin-kernel@...ove.sakura.ne.jp, paul@...l-moore.com,
        sds@...ho.nsa.gov, netdev@...r.kernel.org,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v19 06/23] LSM: Use lsmblob in security_secctx_to_secid

On 7/28/2020 4:11 AM, John Johansen wrote:
> On 7/24/20 1:32 PM, Casey Schaufler wrote:
>> Change security_secctx_to_secid() to fill in a lsmblob instead
>> of a u32 secid. Multiple LSMs may be able to interpret the
>> string, and this allows for setting whichever secid is
>> appropriate. Change security_secmark_relabel_packet() to use a
>> lsmblob instead of a u32 secid. In some other cases there is
>> scaffolding where interfaces have yet to be converted.
>>
>> Reviewed-by: Kees Cook <keescook@...omium.org>
>> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
>> Cc: netdev@...r.kernel.org
> one comment below, but its a nice to have so
>
> Reviewed-by: John Johansen <john.johansen@...onical.com>
>
>
>> ---
>>  include/linux/security.h          | 30 +++++++++++++++++++++++----
>>  include/net/scm.h                 |  7 +++++--
>>  kernel/cred.c                     |  4 +---
>>  net/ipv4/ip_sockglue.c            |  6 ++++--
>>  net/netfilter/nft_meta.c          | 18 +++++++++-------
>>  net/netfilter/xt_SECMARK.c        |  9 ++++++--
>>  net/netlabel/netlabel_unlabeled.c | 23 +++++++++++++--------
>>  security/security.c               | 34 ++++++++++++++++++++++++++-----
>>  8 files changed, 98 insertions(+), 33 deletions(-)
>>
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index d81e8886d799..98176faaaba5 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -189,6 +189,27 @@ static inline bool lsmblob_equal(struct lsmblob *bloba, struct lsmblob *blobb)
>>  	return !memcmp(bloba, blobb, sizeof(*bloba));
>>  }
>>  
>> +/**
>> + * lsmblob_value - find the first non-zero value in an lsmblob structure.
>> + * @blob: Pointer to the data
>> + *
>> + * This needs to be used with extreme caution, as the cases where
>> + * it is appropriate are rare.
>> + *
>> + * Return the first secid value set in the lsmblob.
>> + * There should only be one.
> It would be really nice if we could have an LSM debug config, that would
> do things like checking there is indeed only one value when this fn
> is called.

I can't see a CONFIG_LSM_DEBUG for this alone, but if you have
other places you'd like to see it I'm open to it.