From patchwork Wed Mar 27 08:24:52 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Gstir X-Patchwork-Id: 13605904 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 97EA14AEFB for ; Wed, 27 Mar 2024 08:25:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.52 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711527928; cv=none; b=rkb8RW4sc2is+EK0D3AxTNnDzFL7y3gIuB2A+H1W7qUr2nUhUuICOBaOX5A06G7sVJEYb7EbRQyVu6xehfnPiv2llIgQjMlWm60HUe4oAN5XJRd9rHplCRO3fh/8RJOHj16Df3TSc8hwPdFZkuLwDxXyD9Zt/zCAquJjXRNK/L8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711527928; c=relaxed/simple; bh=FDOPf3xlGpDAEZuAPeTmAaGWnb+6zG3xNnz2qq7Ohj4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jlhmpjEbJ72y1C+iLqiUA1Da7YPfVxj5qc5tKu/OTAIWmIRx5YjFRoBgzQNjVczbKBvCrYId2p530NuzE4HDHa0Zb3OZVmHZr9r+W6ZwugiiGrdhSu+X5GJ1m+Ec1g3SgL3TS/4BUnbq8SNEFH8xxmKoWN2axNSsKJiLMqx3n7I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sigma-star.at; spf=pass smtp.mailfrom=sigma-star.at; dkim=pass (2048-bit key) header.d=sigma-star.at header.i=@sigma-star.at header.b=XfvN7Gbh; arc=none smtp.client-ip=209.85.128.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sigma-star.at Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sigma-star.at Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sigma-star.at header.i=@sigma-star.at header.b="XfvN7Gbh" Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-41495dce900so623935e9.0 for ; Wed, 27 Mar 2024 01:25:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sigma-star.at; s=google; t=1711527925; x=1712132725; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=otEyEh5HNjpSjKJb9y7tWHyWPlbFploqEwD1jDd84X0=; b=XfvN7Gbh77ezLOEcJ8eRipMXL7+5qJjKmYm/ORphg7HV0Zr6k29AN3D7cq7v9B2GM2 tPbjFpIm/2337sSUvtuMU1LbZAfp3arcsBfnJrSv4ZgNUz5tGDZUsY7fZmv/jsrFRXzl JXHXlFQPCGzDBjY/rhafpZkF8WTd2XaeNiObcl/PRJV0+00RHkgDKfGgIabM7JftFsOn F5Oy9jP1NVcMhbaAKZ8IyMmB4IRzMCqIrcYjQNmXRPiRFLyd3G81MtZ5iKFhAnMLELeq 5K1/KXID2vQar9Z4KtaRj+GG4wBjna+9EF/JFO2tt23tBq3B0aJ7KlpgRM/qAmN/ARIo 3JFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711527925; x=1712132725; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=otEyEh5HNjpSjKJb9y7tWHyWPlbFploqEwD1jDd84X0=; b=cY8YyKjT9YkX36w04BbKIS0xAic+UWIJo5dLk2rp1Um0IG3z8YJgY7fXb422WwuRS0 M7INzhurUf/ltPwY1kC167V3wArOE++gXHwkP7sdrMDw4m+hrosoPs+ltnuaDN1gCU2w NZQQzIotXvCP8EQ/xxOmrubAKoyJOPaPtd6DX1de+/e5or4w7FVFrYigRzHZ782InRfb iV61f+B3U+X/ZTofmaAbQcEunmb/K93qmzfZepj5yJ/GLgjiGfFCTYoLxTLSp+l4ATjF e8JVSxjbkdsNfI5Sye/p/iWK63n004A0AkKouUXOayXkWshikV+VS6PuJZFhr9CGsnY6 GD5w== X-Forwarded-Encrypted: i=1; AJvYcCVEkM+aLFKAH4df9qYUmkKlhBpYmzFSIEmOp2COaNpezIC+lgMeEhg6zIv17vFFJziJAGh+Pwk/ZkHj7WLzXJAAyxcfgD5NnI4oWv3eOni2 X-Gm-Message-State: AOJu0YwzrHodP7xYTJWYU3H8HoTDAoBh41lD3kwT5VGO6Yd5xzyBRiME c+xM1FiH1N5ccTIEV/kLq3SwPHLXuuGr4dNY1xV0hf+EAFtpuzCTbmNmY3/b7KE= X-Google-Smtp-Source: AGHT+IG7wR0nbB0jDKSCAusOIuwb3AuuIwFZ056wKDFtuOvUrA17eWCc0lIQ1zSgLo9xL9Vo01c6zQ== X-Received: by 2002:a05:600c:6543:b0:414:8f85:6e50 with SMTP id dn3-20020a05600c654300b004148f856e50mr3234755wmb.19.1711527925056; Wed, 27 Mar 2024 01:25:25 -0700 (PDT) Received: from localhost ([82.150.214.1]) by smtp.gmail.com with UTF8SMTPSA id u8-20020a05600c19c800b0041478393b8fsm1367979wmq.42.2024.03.27.01.25.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Mar 2024 01:25:24 -0700 (PDT) From: David Gstir To: Mimi Zohar , James Bottomley , Jarkko Sakkinen , Herbert Xu , "David S. Miller" Cc: David Gstir , Shawn Guo , Jonathan Corbet , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team , Ahmad Fatoum , sigma star Kernel Team , David Howells , Li Yang , Paul Moore , James Morris , "Serge E. Hallyn" , "Paul E. McKenney" , Randy Dunlap , Catalin Marinas , "Rafael J. Wysocki" , Tejun Heo , "Steven Rostedt (Google)" , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-security-module@vger.kernel.org, Richard Weinberger , David Oberhollenzer Subject: [PATCH v7 6/6] docs: trusted-encrypted: add DCP as new trust source Date: Wed, 27 Mar 2024 09:24:52 +0100 Message-ID: <20240327082454.13729-7-david@sigma-star.at> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240327082454.13729-1-david@sigma-star.at> References: <20240327082454.13729-1-david@sigma-star.at> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 Co-developed-by: Richard Weinberger Signed-off-by: Richard Weinberger Co-developed-by: David Oberhollenzer Signed-off-by: David Oberhollenzer Signed-off-by: David Gstir --- .../security/keys/trusted-encrypted.rst | 85 +++++++++++++++++++ 1 file changed, 85 insertions(+) diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst index e989b9802f92..81fb3540bb20 100644 --- a/Documentation/security/keys/trusted-encrypted.rst +++ b/Documentation/security/keys/trusted-encrypted.rst @@ -42,6 +42,14 @@ safe. randomly generated and fused into each SoC at manufacturing time. Otherwise, a common fixed test key is used instead. + (4) 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 accessible to the DCP encryption engine only. + DCP provides two keys that can be used as root of trust: the OTP key + and the UNIQUE key. Default is to use the UNIQUE key, but selecting + the OTP key can be done via a module parameter (dcp_use_otp_key). + * Execution isolation (1) TPM @@ -57,6 +65,12 @@ safe. Fixed set of operations running in isolated execution environment. + (4) 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 @@ -79,6 +93,11 @@ safe. Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs for platform integrity. + (4) DCP + + Relies on Secure/Trusted boot process (called HAB by vendor) for + platform integrity. + * Interfaces and APIs (1) TPM @@ -94,6 +113,11 @@ safe. Interface is specific to silicon vendor. + (4) 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 trust source for a given @@ -129,6 +153,13 @@ selected trust source: CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device is probed. + * 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. + Users may override this by specifying ``trusted.rng=kernel`` on the kernel command-line to override the used RNG with the kernel's random number pool. @@ -231,6 +262,19 @@ Usage:: CAAM-specific format. 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 -------------------- @@ -426,3 +470,44 @@ 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 trusted 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[]; + } __packed;