From patchwork Tue Dec 10 00:08:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Bottomley X-Patchwork-Id: 11281079 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 40F5C138C for ; Tue, 10 Dec 2019 00:08:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E5622071E for ; Tue, 10 Dec 2019 00:08:12 +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="TBBVB0S5"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="TBBVB0S5" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727276AbfLJAIL (ORCPT ); Mon, 9 Dec 2019 19:08:11 -0500 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:38034 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726495AbfLJAIL (ORCPT ); Mon, 9 Dec 2019 19:08:11 -0500 Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 55F878EE112; Mon, 9 Dec 2019 16:08:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1575936491; bh=Sv+dYY144NbR3Y+mnbT1AlgQKmRsu3svS/dGn4iv9sU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=TBBVB0S59w0dTklPxSMRViekyJXbut8FamWqDp/r8Fxj/2F7XeGCVHWRvP4oBIEsS dZhgJpI4bDajH019ulP1wREUGAPPNQIS/HBMN8f9LL+aZ18j2BR1VUGs1DiffpoNR2 p/VN1CR2R+Xcz16q0m40v6oYKDAdKusf04dHBvSU= 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 dFy4rh2-2svk; Mon, 9 Dec 2019 16:08:11 -0800 (PST) Received: from jarvis.lan (unknown [50.35.76.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bedivere.hansenpartnership.com (Postfix) with ESMTPSA id EC1748EE0FC; Mon, 9 Dec 2019 16:08:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1575936491; bh=Sv+dYY144NbR3Y+mnbT1AlgQKmRsu3svS/dGn4iv9sU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=TBBVB0S59w0dTklPxSMRViekyJXbut8FamWqDp/r8Fxj/2F7XeGCVHWRvP4oBIEsS dZhgJpI4bDajH019ulP1wREUGAPPNQIS/HBMN8f9LL+aZ18j2BR1VUGs1DiffpoNR2 p/VN1CR2R+Xcz16q0m40v6oYKDAdKusf04dHBvSU= Message-ID: <1575936490.31378.55.camel@HansenPartnership.com> Subject: [PATCH v2 5/8] security: keys: trusted: Make sealed key properly interoperable From: James Bottomley To: linux-integrity@vger.kernel.org Cc: Mimi Zohar , Jarkko Sakkinen , David Woodhouse , keyrings@vger.kernel.org Date: Mon, 09 Dec 2019 16:08:10 -0800 In-Reply-To: <1575936272.31378.50.camel@HansenPartnership.com> References: <1575936272.31378.50.camel@HansenPartnership.com> X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 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 --- include/keys/trusted-type.h | 1 + include/linux/tpm.h | 2 + security/keys/trusted-keys/trusted_tpm2.c | 69 ++++++++++++++++++++++--------- 3 files changed, 53 insertions(+), 19 deletions(-) diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index a94c03a61d8f..4728e13aada8 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -22,6 +22,7 @@ struct trusted_key_payload { unsigned int key_len; unsigned int blob_len; unsigned char migratable; + unsigned char old_format; unsigned char key[MAX_KEY_SIZE + 1]; unsigned char blob[MAX_BLOB_SIZE]; }; 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 6ae3197f767f..6d2c5adbff18 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -218,6 +218,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, unsigned int blob_len; struct tpm_buf buf; u32 hash; + u32 flags; int i; int rc; @@ -246,29 +247,30 @@ int tpm2_seal_trusted(struct tpm_chip *chip, TPM_DIGEST_SIZE); /* sensitive */ - tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len + 1); + tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len); tpm_buf_append_u16(&buf, TPM_DIGEST_SIZE); tpm_buf_append(&buf, options->blobauth, TPM_DIGEST_SIZE); - 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); @@ -341,23 +343,42 @@ 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) + if (rc) { /* old form */ blob = payload->blob; + payload->old_format = 1; + } /* new format carries keyhandle but old format doesn't */ if (!options->keyhandle) return -EINVAL; - private_len = be16_to_cpup((__be16 *) &blob[0]); - if (private_len > (payload->blob_len - 2)) + /* must be big enough for at least the two be16 size counts */ + if (payload->blob_len < 4) + return -EINVAL; + private_len = get_unaligned_be16(blob); + /* must be big enough for following public_len */ + if (private_len + 2 + 2 > (payload->blob_len)) + return -E2BIG; + + public_len = get_unaligned_be16(blob + 2 + private_len); + if (private_len + 2 + public_len + 2 > payload->blob_len) return -E2BIG; - public_len = be16_to_cpup((__be16 *) &blob[2 + private_len]); + 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; @@ -438,7 +459,7 @@ 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; } @@ -449,9 +470,19 @@ 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: