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Subject: Re: [RFC PATCH 0/2] ima: uncompressed module appraisal support
From:   Eric Snowberg <eric.snowberg@oracle.com>
In-Reply-To: <1581100125.5585.623.camel@linux.ibm.com>
Date:   Fri, 7 Feb 2020 11:45:14 -0700
Cc:     Nayna <nayna@linux.vnet.ibm.com>, dmitry.kasatkin@gmail.com,
        jmorris@namei.org, serge@hallyn.com, dhowells@redhat.com,
        geert@linux-m68k.org, gregkh@linuxfoundation.org,
        nayna@linux.ibm.com, tglx@linutronix.de, bauerman@linux.ibm.com,
        mpe@ellerman.id.au, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
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To:     Mimi Zohar <zohar@linux.ibm.com>
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> On Feb 7, 2020, at 11:28 AM, Mimi Zohar <zohar@linux.ibm.com> wrote:
>=20
> On Fri, 2020-02-07 at 10:49 -0700, Eric Snowberg wrote:
>>=20
>>> On Feb 7, 2020, at 10:40 AM, Mimi Zohar <zohar@linux.ibm.com> wrote:
>>>=20
>>>> $ insmod ./foo.ko
>>>> insmod: ERROR: could not insert module ./foo.ko: Permission denied
>>>>=20
>>>> last entry from audit log:
>>>> type=3DINTEGRITY_DATA msg=3Daudit(1581089373.076:83): pid=3D2874 =
uid=3D0
>>>> auid=3D0 ses=3D1 subj=3Dunconfined_u:unconfined_r:unconfined_t:s0-
>>>> s0:c0.c1023 op=3Dappraise_data cause=3Dinvalid-signature =
comm=3D"insmod"
>>>> name=3D"/root/keys/modules/foo.ko" dev=3D"dm-0" ino=3D10918365
>>>> res=3D0^]UID=3D"root" AUID=3D=E2=80=9Croot"
>>>>=20
>>>> This is because modsig_verify() will be called from within
>>>> ima_appraise_measurement(),=20
>>>> since try_modsig is true.  Then modsig_verify() will return
>>>> INTEGRITY_FAIL.
>>>=20
>>> Why is it an "invalid signature"?  For that you need to look at the
>>> kernel messages.  Most likely it can't find the public key on the =
.ima
>>> keyring to verify the signature.
>>=20
>> It is invalid because the module has not been ima signed.=20
>=20
> With the IMA policy rule "appraise func=3DMODULE_CHECK
> appraise_type=3Dimasig|modsig", IMA first tries to verify the IMA
> signature stored as an xattr and on failure then attempts to verify
> the appended signatures.
>=20
> The audit message above indicates that there was a signature, but the
> signature validation failed.
>=20

I do have  CONFIG_IMA_APPRAISE_MODSIG enabled.  I believe the audit =
message above=20
is coming from modsig_verify in security/integrity/ima/ima_appraise.c.