From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 2D12921103970 for ; Tue, 28 Aug 2018 15:48:26 -0700 (PDT) Subject: [PATCH v8 12/12] libnvdimm: add documentation for nvdimm security support From: Dave Jiang Date: Tue, 28 Aug 2018 15:48:25 -0700 Message-ID: <153549650543.4089.4276034419476883694.stgit@djiang5-desk3.ch.intel.com> In-Reply-To: <153549632073.4089.3609134467249378610.stgit@djiang5-desk3.ch.intel.com> References: <153549632073.4089.3609134467249378610.stgit@djiang5-desk3.ch.intel.com> MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: linux-nvdimm@lists.01.org Cc: alison.schofield@intel.com, keescook@chromium.org, ebiggers3@gmail.com, dhowells@redhat.com, keyrings@vger.kernel.org List-ID: Add theory of operation for the security support that's going into libnvdimm. Signed-off-by: Dave Jiang --- Documentation/nvdimm/security.txt | 82 +++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 Documentation/nvdimm/security.txt diff --git a/Documentation/nvdimm/security.txt b/Documentation/nvdimm/security.txt new file mode 100644 index 000000000000..b230447bf237 --- /dev/null +++ b/Documentation/nvdimm/security.txt @@ -0,0 +1,82 @@ +NVDIMM SECURITY +=============== + +1. Introduction +--------------- + +With the introduction of Intel DSM v1.7 specification [1], security DSMs are +introduced. The spec added the following security DSMs: "get security state", +"set passphrase", "disable passphrase", "unlock unit", "freeze lock", +"secure erase", and "overwrite". A security_ops data structure has been +added to struct dimm in order to support the security operations and generic +APIs are exposed to allow vendor neutral operations. + +2. Sysfs Interface +------------------ +The "security" sysfs attribute is provided in the nvdimm sysfs directory. For +example: +/sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0012:00/ndbus0/nmem0/security + +The "show" function of that attribute will display the security state for +that DIMM. The following states are available: disabled, unlocked, locked, +frozen, and unsupported. + +The "store" function takes several commands when the attribute is written to +in order to support some of the security functionalities: +update - enable security. Add or update current key. +disable - disable enabled security and remove key. +freeze - freeze changing of security states. +erase - generate new ecryption key for DIMM and crypto-scrambles all existing + user data. + +3. Key Management +----------------- + +The key is associted to the payload by the DIMM id. For example: +# cat /sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0012:00/ndbus0/nmem0/nfit/id +8089-a2-1740-00000133 +The DIMM id would be provided along with the key payload (passphrase) to +the kernel. + +The security keys are managed on the basis of a single key per DIMM. The +key "passphrase" is expected to be 32bytes long or padded to 32bytes. This is +similar to the ATA security specification [2]. A key is initially acquired +via the request_key() kernel API call and retrieved from userspace. It is up to +the user to provide an upcall application to retrieve the key in whatever +fashion meets their security requirements. + +The payload provided to the key can be a 32bytes payload or 64bytes payload +when doing an "update". The payload is viewed as 64 bytes in the following +format: +[32 bytes new key data zero padded][32 bytes current key data zero padded] +However, a 32bytes payload can be provided and will be assumed as the old +key to be 32 bytes of 0s and the provided 32bytes payload is the new key. +It is up to the user upcall function how that's presented as the key payload +to the kernel. + +All the other security functions that require a provided key can accept a +32bytes payload or 64bytes. If the payload is 64bytes, then second 32bytes +will be ignored and the first 32bytes contains the expected "passphrase". + +4. Unlocking +------------ +When the DIMMs are being enumerated by the kernel, the kernel will attempt to +retrieve the key from its keyring. If that fails, it will attempt to +acquire the key from the userspace upcall function. This is the only time +a locked DIMM can be unlocked. Once unlocked, the DIMM will remain unlocked +until reboot. + +5. Update +--------- +When doing an update, it is expected that the new key with the 64bit payload of +format described above is added via the keyutils API or utility. The update +command written to the sysfs attribute will be with the format: +update:: +If there is no old ID due to a security enabling, then a 0 should be passed in. +It is expected that a user logon key has been injected via keyutils to provide +the payload for the update operation. The kernel will take the new user key, +attempt the update operation with the nvdimm, and replace the existing key's +payload with the new passphrase. + +[1]: http://pmem.io/documents/NVDIMM_DSM_Interface-V1.7.pdf +[2]: http://www.t13.org/documents/UploadedDocuments/docs2006/e05179r4-ACS-SecurityClarifications.pdf _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm