From patchwork Thu Oct 31 13:58:42 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sumit Garg X-Patchwork-Id: 11221277 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 426AD913 for ; Thu, 31 Oct 2019 14:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 16AD021734 for ; Thu, 31 Oct 2019 14:00:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="pjyU78O3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727592AbfJaOAY (ORCPT ); Thu, 31 Oct 2019 10:00:24 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:41897 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727972AbfJaOAY (ORCPT ); Thu, 31 Oct 2019 10:00:24 -0400 Received: by mail-pg1-f193.google.com with SMTP id l3so4113574pgr.8 for ; Thu, 31 Oct 2019 07:00:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=ihVno30NiTJ4nXlPwk0p1JArXGGwnpn9XYnN+QyiMz4=; b=pjyU78O3YD26ZTvmDq7xDFKMfe99rm566ijOjFmjEwdUYnQCPRdeZh7dv5cb6Oos8F QSMyWgVfo7mHozTV03x0jbZZRFQ4MxkzyoxnQSASeZLcT+BBWjFafJWIhxAR71eLjsbI skUqbhe3vLZYr0aQyxC4mSDwJLduVYXX6TAuOGWX4zjay4Dl7oI5v5QoC3NjmlUnQOwh zDwnvUGNk71ke/htRBQMgau7Skx9H0uP2dPYY9vy5Z5pD430uSHA/dcr9RabkYUHiZvB 8cHTdQFXB8svq3viRjwodMFg1PV4zVPLrOzJjHsmldInuV4PcY2HEPSGNgy8RvfBO/tW bKlw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=ihVno30NiTJ4nXlPwk0p1JArXGGwnpn9XYnN+QyiMz4=; b=N/C8HK+qGczZ+Zto2kntPHGEVe5nF7/WwENkyWYFCBCgdDRMP9AH9nRV5xq9Nwjl0y prtwAxUcjbHzY1Bdbdd3CoMsqnmW5YQWCrsPt9F7JeDZ8+8WKYZhsSpfTuRDVxV6ApfM XmRCfyjR7q80NCkAp0YX3H0JBUjLsjywOcEwu2dFjLuNCHVwLCAfaDJG388ddpwbjznd VlzfvlgXuRcxzLniJivCuY56wF3Vnc4OkbeJNGTdcpS2k4IK1dFrIlnjreC/a/OEU+5F GDS0gKHmkCZfNDSLnjjPNNeCLLAGZEIgFrv2H1CjIP7x7454sECvoICvzkXAyi+CMgv0 qB2g== X-Gm-Message-State: APjAAAVn/VXIkv4ql15Bw8d5fuYXIX0TwqMgdkjW2x8o8uUWsV+DI3/g uial+lvygbtWiXlPpGI/ZbKh3g== X-Google-Smtp-Source: APXvYqz8MkbuV1hRddfSZ/QAk8v+XST0VkzaBOaZtV3PDcEQqkrpHQNhHr7g24puFk5SVUbTJ1tdbA== X-Received: by 2002:a17:90a:fa02:: with SMTP id cm2mr7821867pjb.129.1572530422954; Thu, 31 Oct 2019 07:00:22 -0700 (PDT) Received: from localhost.localdomain ([117.252.69.143]) by smtp.gmail.com with ESMTPSA id i16sm3522441pfa.184.2019.10.31.07.00.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 31 Oct 2019 07:00:22 -0700 (PDT) From: Sumit Garg To: jens.wiklander@linaro.org, jarkko.sakkinen@linux.intel.com, dhowells@redhat.com Cc: corbet@lwn.net, jejb@linux.ibm.com, zohar@linux.ibm.com, jmorris@namei.org, serge@hallyn.com, casey@schaufler-ca.com, ard.biesheuvel@linaro.org, daniel.thompson@linaro.org, stuart.yoder@arm.com, janne.karhunen@gmail.com, keyrings@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tee-dev@lists.linaro.org, Sumit Garg Subject: [Patch v3 6/7] doc: keys: Document usage of TEE based Trusted Keys Date: Thu, 31 Oct 2019 19:28:42 +0530 Message-Id: <1572530323-14802-7-git-send-email-sumit.garg@linaro.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1572530323-14802-1-git-send-email-sumit.garg@linaro.org> References: <1572530323-14802-1-git-send-email-sumit.garg@linaro.org> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: Provide documentation for usage of TEE based Trusted Keys via existing user-space "keyctl" utility. Also, document various use-cases. Signed-off-by: Sumit Garg --- Documentation/security/keys/index.rst | 1 + Documentation/security/keys/tee-trusted.rst | 93 +++++++++++++++++++++++++++++ 2 files changed, 94 insertions(+) create mode 100644 Documentation/security/keys/tee-trusted.rst diff --git a/Documentation/security/keys/index.rst b/Documentation/security/keys/index.rst index 647d58f..f9ef557 100644 --- a/Documentation/security/keys/index.rst +++ b/Documentation/security/keys/index.rst @@ -9,3 +9,4 @@ Kernel Keys ecryptfs request-key trusted-encrypted + tee-trusted diff --git a/Documentation/security/keys/tee-trusted.rst b/Documentation/security/keys/tee-trusted.rst new file mode 100644 index 0000000..ef03745 --- /dev/null +++ b/Documentation/security/keys/tee-trusted.rst @@ -0,0 +1,93 @@ +====================== +TEE based Trusted Keys +====================== + +TEE based Trusted Keys provides an alternative approach for providing Trusted +Keys in case TPM chip isn't present. + +Trusted Keys use a TEE service/device both to generate and to seal the keys. +Keys are sealed under a hardware unique key in the TEE, and only unsealed by +the TEE. + +For more information about TEE, refer to ``Documentation/tee.txt``. + +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 TEE device implementation. The key length for new keys are always +in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). + +Examples of trusted key and its usage as 'master' key for encrypted key usage: + +More details about encrypted keys can be found here: +``Documentation/security/keys/trusted-encrypted.rst`` + +Create and save a trusted key named "kmk" of length 32 bytes:: + + $ keyctl add trusted kmk "new 32" @u + 754414669 + + $ keyctl show + Session Keyring + 827385718 --alswrv 0 65534 keyring: _uid_ses.0 + 274124851 --alswrv 0 65534 \_ keyring: _uid.0 + 754414669 --als-rv 0 0 \_ trusted: kmk + + $ keyctl print 754414669 + 15676790697861b422175596ae001c2f505cea2c6f3ebbc5fb08eeb1f343a07e + + $ keyctl pipe 754414669 > kmk.blob + +Load a trusted key from the saved blob:: + + $ keyctl add trusted kmk "load `cat kmk.blob`" @u + 491638700 + + $ keyctl print 491638700 + 15676790697861b422175596ae001c2f505cea2c6f3ebbc5fb08eeb1f343a07e + +The initial consumer of trusted keys is EVM, which at boot time needs a high +quality symmetric key for HMAC protection of file metadata. The use of a +TEE based trusted key provides security that the EVM key has not been +compromised by a user level problem and tied to particular hardware. + +Create and save an encrypted key "evm" using the above trusted key "kmk": + +option 1: omitting 'format':: + + $ keyctl add encrypted evm "new trusted:kmk 32" @u + 608915065 + +option 2: explicitly defining 'format' as 'default':: + + $ keyctl add encrypted evm "new default trusted:kmk 32" @u + 608915065 + + $ keyctl print 608915065 + default trusted:kmk 32 f380ac588a925f488d5be007cf23e4c900b8b652ab62241c8 + ed54906189b6659d139d619d4b51752a2645537b11fd44673f13154a65b3f595d5fb2131 + 2fe45529ea0407c644ea4026f2a1a75661f2c9b66 + + $ keyctl pipe 608915065 > evm.blob + +Load an encrypted key "evm" from saved blob:: + + $ keyctl add encrypted evm "load `cat evm.blob`" @u + 831684262 + + $ keyctl print 831684262 + default trusted:kmk 32 f380ac588a925f488d5be007cf23e4c900b8b652ab62241c8 + ed54906189b6659d139d619d4b51752a2645537b11fd44673f13154a65b3f595d5fb2131 + 2fe45529ea0407c644ea4026f2a1a75661f2c9b66 + +Other uses for trusted and encrypted keys, such as for disk and file encryption +are anticipated. In particular the 'ecryptfs' encrypted keys format can be used +to mount an eCryptfs filesystem. More details about the usage can be found in +the file ``Documentation/security/keys/ecryptfs.rst``. + +Another format 'enc32' can be used to support encrypted keys with payload size +of 32 bytes.