From patchwork Mon Jun 14 20:16:20 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Richard Weinberger X-Patchwork-Id: 12319811 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3392C49361 for ; Mon, 14 Jun 2021 20:24:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C84C861356 for ; Mon, 14 Jun 2021 20:24:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235165AbhFNU0W (ORCPT ); Mon, 14 Jun 2021 16:26:22 -0400 Received: from lilium.sigma-star.at ([109.75.188.150]:59380 "EHLO lilium.sigma-star.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234848AbhFNU0W (ORCPT ); Mon, 14 Jun 2021 16:26:22 -0400 X-Greylist: delayed 455 seconds by postgrey-1.27 at vger.kernel.org; Mon, 14 Jun 2021 16:26:18 EDT Received: from localhost (localhost [127.0.0.1]) by lilium.sigma-star.at (Postfix) with ESMTP id 7C89818190E4A; Mon, 14 Jun 2021 22:16:38 +0200 (CEST) Received: from lilium.sigma-star.at ([127.0.0.1]) by localhost (lilium.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id EytU5U21JfDt; Mon, 14 Jun 2021 22:16:37 +0200 (CEST) Received: from lilium.sigma-star.at ([127.0.0.1]) by localhost (lilium.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id Yxr3TtJK9DNP; Mon, 14 Jun 2021 22:16:37 +0200 (CEST) From: Richard Weinberger To: keyrings@vger.kernel.org Cc: David Gstir , Ahmad Fatoum , David Howells , "David S. Miller" , Fabio Estevam , Herbert Xu , James Bottomley , James Morris , Jarkko Sakkinen , Jonathan Corbet , linux-arm-kernel@lists.infradead.org, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, Mimi Zohar , NXP Linux Team , Pengutronix Kernel Team , Richard Weinberger , Sascha Hauer , "Serge E. Hallyn" , Shawn Guo Subject: [PATCH 3/3] doc: trusted-encrypted: add DCP as new trust source Date: Mon, 14 Jun 2021 22:16:20 +0200 Message-Id: <20210614201620.30451-4-richard@nod.at> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210614201620.30451-1-richard@nod.at> References: <20210614201620.30451-1-richard@nod.at> MIME-Version: 1.0 Precedence: bulk List-ID: From: David Gstir Update the documentation for trusted and encrypted KEYS with DCP as new trust source: - Describe security properties of DCP trust source - Describe key usage - Document blob format Cc: Ahmad Fatoum Cc: David Gstir Cc: David Howells Cc: "David S. Miller" Cc: Fabio Estevam Cc: Herbert Xu Cc: James Bottomley Cc: James Morris Cc: Jarkko Sakkinen Cc: Jonathan Corbet Cc: keyrings@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-crypto@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-integrity@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-security-module@vger.kernel.org Cc: Mimi Zohar Cc: NXP Linux Team Cc: Pengutronix Kernel Team Cc: Richard Weinberger Cc: Sascha Hauer Cc: "Serge E. Hallyn" Cc: Shawn Guo Co-developed-by: Richard Weinberger Signed-off-by: David Gstir --- .../security/keys/trusted-encrypted.rst | 84 ++++++++++++++++++- 1 file changed, 83 insertions(+), 1 deletion(-) diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst index 80d5a5af62a1..e8413122e4bc 100644 --- a/Documentation/security/keys/trusted-encrypted.rst +++ b/Documentation/security/keys/trusted-encrypted.rst @@ -35,6 +35,11 @@ safe. Rooted to Hardware Unique Key (HUK) which is generally burnt in on-chip fuses and is accessible to TEE only. + (3) DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs) + + Rooted to a one-time programmable key (OTP) that is generally burnt in + the on-chip fuses and is accessbile to the DCP encryption engine only. + * Execution isolation (1) TPM @@ -46,6 +51,12 @@ safe. Customizable set of operations running in isolated execution environment verified via Secure/Trusted boot process. + (3) DCP + + Fixed set of cryptographic operations running in isolated execution + environment. Only basic blob key encryption is executed there. + The actual key sealing/unsealing is done on main processor/kernel space. + * Optional binding to platform integrity state (1) TPM @@ -63,6 +74,11 @@ safe. Relies on Secure/Trusted boot process for platform integrity. It can be extended with TEE based measured boot process. + (3) DCP + + Relies on Secure/Trusted boot process (called HAB by vendor) for + platform integrity. + * Interfaces and APIs (1) TPM @@ -74,10 +90,14 @@ safe. TEEs have well-documented, standardized client interface and APIs. For more details refer to ``Documentation/staging/tee.rst``. + (3) DCP + + Vendor-specific API that is implemented as part of the DCP crypto driver in + ``drivers/crypto/mxs-dcp.c``. * Threat model - The strength and appropriateness of a particular TPM or TEE for a given + The strength and appropriateness of a particular TPM, TEE or DCP for a given purpose must be assessed when using them to protect security-relevant data. @@ -103,6 +123,14 @@ access control policy within the trust source. from platform specific hardware RNG or a software based Fortuna CSPRNG which can be seeded via multiple entropy sources. + * DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs) + + The DCP hardware device itself does not provide a dedicated RNG interface, + so the kernel default RNG is used. SoCs with DCP like the i.MX6ULL do have + a dedicated hardware RNG that is independent from DCP which can be enabled + to back the kernel RNG. + + Encrypted Keys -------------- @@ -188,6 +216,19 @@ Usage:: specific to TEE device implementation. The key length for new keys is always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). +Trusted Keys usage: DCP +----------------------- + +Usage:: + + keyctl add trusted name "new keylen" ring + keyctl add trusted name "load hex_blob" ring + keyctl print keyid + +"keyctl print" returns an ASCII hex copy of the sealed key, which is in format +specific to this DCP key-blob implementation. The key length for new keys is +always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). + Encrypted Keys usage -------------------- @@ -370,3 +411,44 @@ string length. privkey is the binary representation of TPM2B_PUBLIC excluding the initial TPM2B header which can be reconstructed from the ASN.1 octed string length. + +DCP Blob Format +--------------- + +The Data Co-Processor (DCP) provides hardware-bound AES keys using its +AES encryption engine only. It does not provide direct key sealing/unsealing. +To make DCP hardware encryption keys usable as trust source, we define +our own custom format that uses a hardware-bound key to secure the sealing +key stored in the key blob. + +Whenever a new tusted key using DCP is generated, we generate a random 128-bit +blob encryption key (BEK) and 128-bit nonce. The BEK and nonce are used to +encrypt the trusted key payload using AES-128-GCM. + +The BEK itself is encrypted using the hardware-bound key using the DCP's AES +encryption engine with AES-128-ECB. The encrypted BEK, generated nonce, +BEK-encrypted payload and authentication tag make up the blob format together +with a version number, payload length and authentication tag:: + + /* + * struct dcp_blob_fmt - DCP BLOB format. + * + * @fmt_version: Format version, currently being %1 + * @blob_key: Random AES 128 key which is used to encrypt @payload, + * @blob_key itself is encrypted with OTP or UNIQUE device key in + * AES-128-ECB mode by DCP. + * @nonce: Random nonce used for @payload encryption. + * @payload_len: Length of the plain text @payload. + * @payload: The payload itself, encrypted using AES-128-GCM and @blob_key, + * GCM auth tag of size AES_BLOCK_SIZE is attached at the end of it. + * + * The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) + @payload_len + + * AES_BLOCK_SIZE. + */ + struct dcp_blob_fmt { + __u8 fmt_version; + __u8 blob_key[AES_KEYSIZE_128]; + __u8 nonce[AES_KEYSIZE_128]; + __le32 payload_len; + __u8 payload[0]; + } __packed;