From patchwork Tue Mar 10 05:16:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Bottomley X-Patchwork-Id: 11428513 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 E81741731 for ; Tue, 10 Mar 2020 05:19:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C851C24655 for ; Tue, 10 Mar 2020 05:19:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="S1pB/IjS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726199AbgCJFTg (ORCPT ); Tue, 10 Mar 2020 01:19:36 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:35590 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726088AbgCJFTg (ORCPT ); Tue, 10 Mar 2020 01:19:36 -0400 Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id E24628EE130; Mon, 9 Mar 2020 22:19:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1583817575; bh=VKkedKqTNoZJDEOYvaVHaK/dcKAmmokAC4SoDN/BK3g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S1pB/IjSp2+9t0pm0wWFueCN6eTOXpUxJHF6kg7vbV0g7X5wtpplCMzEGDThDm2y0 Y7EM0lgsjrjisZ2Dedkk6lweUPLgCSuofuCuom542TS9RB8/WZvd1WqtrA/9gpKzkS ws7MzUMPaHU2t0QskQLQfvcgC008JcLyN+tvTp5w= 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 jx7B0fTpR5PA; Mon, 9 Mar 2020 22:19:35 -0700 (PDT) Received: from jarvis.lan (jarvis.ext.hansenpartnership.com [153.66.160.226]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 7FD6B8EE121; Mon, 9 Mar 2020 22:19:35 -0700 (PDT) From: James Bottomley To: linux-integrity@vger.kernel.org Cc: Mimi Zohar , Jarkko Sakkinen , David Woodhouse , keyrings@vger.kernel.org Subject: [PATCH v8 5/8] security: keys: trusted: Make sealed key properly interoperable Date: Mon, 9 Mar 2020 22:16:04 -0700 Message-Id: <20200310051607.30334-6-James.Bottomley@HansenPartnership.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20200310051607.30334-1-James.Bottomley@HansenPartnership.com> References: <20200310051607.30334-1-James.Bottomley@HansenPartnership.com> Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@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 --- v2: added length checks to untrusted payload v8: recover patch --- 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 03e9b184411b..cd46ab27baa5 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -297,6 +297,8 @@ 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 e8dcc47b3388..905c5ca4d51c 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: