From patchwork Sun Nov 29 22:20:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Bottomley X-Patchwork-Id: 11939367 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 E175090 for ; Sun, 29 Nov 2020 22:28:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8443B207BC for ; Sun, 29 Nov 2020 22:28:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="M5fd2HSq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727433AbgK2W2W (ORCPT ); Sun, 29 Nov 2020 17:28:22 -0500 Received: from bedivere.hansenpartnership.com ([96.44.175.130]:42648 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725950AbgK2W2V (ORCPT ); Sun, 29 Nov 2020 17:28:21 -0500 Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 62F5A1280A33; Sun, 29 Nov 2020 14:27:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1606688861; bh=UOlUBNX3P8lJMTEgBXDRy3o28wCd+vNL9heFQ6js35Y=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References:From; b=M5fd2HSqPjltvHCxYVXt8pqKF3W/dqqk6yVpfemTlaZObbBlL7QvUWdQExtq9ch/1 lKCEU+VENZmHGvxI9WDi38h1o4rSnl/EB7TM+LU2hxTJ5uVU8uE6qwbzPIJnMXXC4Z m9Pn+jhZv8z59qJOp4DtWvD4kxBdYNR0KlAVRBHI= 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 D320IP_tkiBm; Sun, 29 Nov 2020 14:27:41 -0800 (PST) Received: from jarvis.int.hansenpartnership.com (jarvis.ext.hansenpartnership.com [153.66.160.226]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id E25E61280A32; Sun, 29 Nov 2020 14:27:40 -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 v14 5/5] security: keys: trusted: Make sealed key properly interoperable Date: Sun, 29 Nov 2020 14:20:04 -0800 Message-Id: <20201129222004.4428-6-James.Bottomley@HansenPartnership.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20201129222004.4428-1-James.Bottomley@HansenPartnership.com> References: <20201129222004.4428-1-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 03dea445362c..7886b6d39d68 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, unsigned int blob_len; 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); @@ -356,8 +358,9 @@ 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) { @@ -384,6 +387,16 @@ 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; @@ -464,7 +477,7 @@ 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; } @@ -475,9 +488,19 @@ 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: