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From: Mimi Zohar To: James Bottomley , David Howells , Udit Agarwal Cc: zohar@linux.vnet.ibm.com, jmorris@namei.org, serge@hallyn.com, denkenz@gmail.com, linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, sahil.malhotra@nxp.com, ruchika.gupta@nxp.com, horia.geanta@nxp.com, aymen.sghaier@nxp.com Date: Fri, 03 Aug 2018 10:45:35 -0400 In-Reply-To: <1533306238.4140.1.camel@HansenPartnership.com> References: <20180723111432.26830-1-udit.agarwal@nxp.com> <8060.1533226481@warthog.procyon.org.uk> <1533297482.4337.373.camel@linux.ibm.com> <1533306238.4140.1.camel@HansenPartnership.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 18080314-0020-0000-0000-000002B0B151 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18080314-0021-0000-0000-000020FCE5CC Message-Id: <1533307535.4337.415.camel@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-03_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808030163 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2018-08-03 at 07:23 -0700, James Bottomley wrote: > On Fri, 2018-08-03 at 07:58 -0400, Mimi Zohar wrote: > > On Thu, 2018-08-02 at 17:14 +0100, David Howells wrote: > > > Udit Agarwal wrote: > > > > > > > +========== > > > > +Secure Key > > > > +========== > > > > + > > > > +Secure key is the new type added to kernel key ring service. > > > > +Secure key is a symmetric type key of minimum length 32 bytes > > > > +and with maximum possible length to be 128 bytes. It is produced > > > > +in kernel using the CAAM crypto engine. Userspace can only see > > > > +the blob for the corresponding key. All the blobs are displayed > > > > +or loaded in hex ascii. > > > > > > To echo Mimi, this sounds suspiciously like it should have a > > > generic interface, not one that's specifically tied to one piece of > > > hardware - particularly if it's named with generic "secure". > > > > > > Can you convert this into a "symmetric" type and make the backend > > > pluggable? > > > > TPM 1.2 didn't support symmetric keys.  For this reason, the TPM > > "unseals" the random number, used as a symmetric key, and returns the > > "unsealed" data to the kernel. > > > > Does anyone know if CAAM or TPM 2.0 have support for symmetric keys? > > It depends what you mean by "support". The answer is technically yes, > it's the TPM2_EncryptDecrypt primitive. However, the practical answer > is that symmetric keys are mostly used for bulk operations and the TPM > and its bus are way too slow to support that, so the only real, > practical use case is to have the TPM govern the release conditions for > symmetric keys which are later used by a fast bulk encryptor/decryptor > based in software. > > >  If they have symmetric key support, there would be no need for the > > symmetric key ever to leave the device in the clear.  The device > > would unseal/decrypt data, such as an encrypted key. > > > > The "symmetric" key type would be a generic interface for different > > devices. > > It's possible, but it would only work for a non-bulk use case; do we > have one of those? "trusted" keys are currently being used to decrypt other keys (eg. encrypted, ecryptfs, ...). Mimi