From patchwork Wed Jan 27 19:06:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Bottomley X-Patchwork-Id: 12050825 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=-18.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 CCF14C433DB for ; Wed, 27 Jan 2021 19:17:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87D1264DC1 for ; Wed, 27 Jan 2021 19:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231136AbhA0TRN (ORCPT ); Wed, 27 Jan 2021 14:17:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231130AbhA0TRK (ORCPT ); Wed, 27 Jan 2021 14:17:10 -0500 Received: from bedivere.hansenpartnership.com (bedivere.hansenpartnership.com [IPv6:2607:fcd0:100:8a00::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4C4F3C061573; Wed, 27 Jan 2021 11:16:30 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 222FC128043E; Wed, 27 Jan 2021 11:16:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1611774990; bh=manDTqzsIFGWjGCEd9IW/zEZEI9+dK1VIDb+7rfMVBM=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References:From; b=t3glW1fDcVrC7jUmPhZk6aiREJaC1qR4YlKc+QqjhDjf2ggIvZwGYh3uP+B79uk/d OL0Csxo2zXLJBMALX88/feH1OpRNoYcReCVYGhrDkexlpwDAtc+wE3JzpzJla17yXD CRcPpmn1sggggDHb1soEJWXGAIbOSuhOqgtsV5SE= Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ffSmx6MLL289; Wed, 27 Jan 2021 11:16:30 -0800 (PST) Received: from jarvis.int.hansenpartnership.com (jarvis.ext.hansenpartnership.com [153.66.160.226]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id A8C6312803A7; Wed, 27 Jan 2021 11:16:29 -0800 (PST) From: James Bottomley To: linux-integrity@vger.kernel.org Cc: Mimi Zohar , Jarkko Sakkinen , David Woodhouse , keyrings@vger.kernel.org, David Howells Subject: [PATCH v15 5/5] security: keys: trusted: Make sealed key properly interoperable Date: Wed, 27 Jan 2021 11:06:17 -0800 Message-Id: <20210127190617.17564-6-James.Bottomley@HansenPartnership.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20210127190617.17564-1-James.Bottomley@HansenPartnership.com> References: <20210127190617.17564-1-James.Bottomley@HansenPartnership.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org The current implementation appends a migratable flag to the end of a key, meaning the format isn't exactly interoperable because the using party needs to know to strip this extra byte. However, all other consumers of TPM sealed blobs expect the unseal to return exactly the key. Since TPM2 keys have a key property flag that corresponds to migratable, use that flag instead and make the actual key the only sealed quantity. This is secure because the key properties are bound to a hash in the private part, so if they're altered the key won't load. Backwards compatibility is implemented by detecting whether we're loading a new format key or not and correctly setting migratable from the last byte of old format keys. Signed-off-by: James Bottomley Reviewed-by: Jarkko Sakkinen Tested-by: Jarkko Sakkinen --- v2: added length checks to untrusted payload v8: recover patch v14: add tested by --- include/linux/tpm.h | 2 + security/keys/trusted-keys/trusted_tpm2.c | 53 ++++++++++++++++------- 2 files changed, 40 insertions(+), 15 deletions(-) diff --git a/include/linux/tpm.h b/include/linux/tpm.h index c4ca52138e8b..f1e32bc7d618 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -305,6 +305,8 @@ struct tpm_buf { }; enum tpm2_object_attributes { + TPM2_OA_FIXED_TPM = BIT(1), + TPM2_OA_FIXED_PARENT = BIT(4), TPM2_OA_USER_WITH_AUTH = BIT(6), }; diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index b8ef087528e9..5d4e1f3ebb19 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -231,6 +231,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, int blob_len = 0; struct tpm_buf buf; u32 hash; + u32 flags; int i; int rc; @@ -259,31 +260,32 @@ int tpm2_seal_trusted(struct tpm_chip *chip, TPM_DIGEST_SIZE); /* sensitive */ - tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len + 1); + tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len); tpm_buf_append_u16(&buf, options->blobauth_len); if (options->blobauth_len) tpm_buf_append(&buf, options->blobauth, options->blobauth_len); - tpm_buf_append_u16(&buf, payload->key_len + 1); + tpm_buf_append_u16(&buf, payload->key_len); tpm_buf_append(&buf, payload->key, payload->key_len); - tpm_buf_append_u8(&buf, payload->migratable); /* public */ tpm_buf_append_u16(&buf, 14 + options->policydigest_len); tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH); tpm_buf_append_u16(&buf, hash); + /* key properties */ + flags = 0; + flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH; + flags |= payload->migratable ? (TPM2_OA_FIXED_TPM | + TPM2_OA_FIXED_PARENT) : 0; + tpm_buf_append_u32(&buf, flags); + /* policy */ - if (options->policydigest_len) { - tpm_buf_append_u32(&buf, 0); - tpm_buf_append_u16(&buf, options->policydigest_len); + tpm_buf_append_u16(&buf, options->policydigest_len); + if (options->policydigest_len) tpm_buf_append(&buf, options->policydigest, options->policydigest_len); - } else { - tpm_buf_append_u32(&buf, TPM2_OA_USER_WITH_AUTH); - tpm_buf_append_u16(&buf, 0); - } /* public parameters */ tpm_buf_append_u16(&buf, TPM_ALG_NULL); @@ -357,8 +359,9 @@ static int tpm2_load_cmd(struct tpm_chip *chip, unsigned int private_len; unsigned int public_len; unsigned int blob_len; - u8 *blob; + u8 *blob, *pub; int rc; + u32 attrs; rc = tpm2_key_decode(payload, options, &blob); if (rc) { @@ -385,6 +388,16 @@ static int tpm2_load_cmd(struct tpm_chip *chip, if (private_len + 2 + public_len + 2 > payload->blob_len) return -E2BIG; + pub = blob + 2 + private_len + 2; + /* key attributes are always at offset 4 */ + attrs = get_unaligned_be32(pub + 4); + + if ((attrs & (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) == + (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) + payload->migratable = 0; + else + payload->migratable = 1; + blob_len = private_len + public_len + 4; if (blob_len > payload->blob_len) return -E2BIG; @@ -465,7 +478,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, if (!rc) { data_len = be16_to_cpup( (__be16 *) &buf.data[TPM_HEADER_SIZE + 4]); - if (data_len < MIN_KEY_SIZE || data_len > MAX_KEY_SIZE + 1) { + if (data_len < MIN_KEY_SIZE || data_len > MAX_KEY_SIZE) { rc = -EFAULT; goto out; } @@ -476,9 +489,19 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, } data = &buf.data[TPM_HEADER_SIZE + 6]; - memcpy(payload->key, data, data_len - 1); - payload->key_len = data_len - 1; - payload->migratable = data[data_len - 1]; + if (payload->old_format) { + /* migratable flag is at the end of the key */ + memcpy(payload->key, data, data_len - 1); + payload->key_len = data_len - 1; + payload->migratable = data[data_len - 1]; + } else { + /* + * migratable flag already collected from key + * attributes + */ + memcpy(payload->key, data, data_len); + payload->key_len = data_len; + } } out: