From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02B69C54EE9 for ; Tue, 20 Sep 2022 04:51:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229768AbiITEvC (ORCPT ); Tue, 20 Sep 2022 00:51:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229832AbiITEvA (ORCPT ); Tue, 20 Sep 2022 00:51:00 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A15852DC7; Mon, 19 Sep 2022 21:50:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 001E5B818B6; Tue, 20 Sep 2022 04:50:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7E9FC433D6; Tue, 20 Sep 2022 04:50:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1663649456; bh=fzjnfFvXaoLalr68n3B2MZyIURza6L8/C5Yc3Wy/osI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oX7GvtQRx5hPjag0bbNf26qO81fekuU0755+qCCtZxI00VfTgFLg/j7/suGU+f0dL BhH2cIEwfRo3I2lA2GS//8IkXQXMo1LQ7xSBsmPoKDZXPbXJSIYOuYWbTQzpQsG7l8 RE4lRC9d3vNLddHPdFIOMPRKIskmZtsbkbihaSp6qwrY3EyZE9iuKOhesLAhM3IBUr mxRe01nWD/AjhC83Jd1VrnevgW/wW1qnBy5WDp+FHTths2Y2OnwTfI6QHNrQaCpW09 SdJYvV3SGeS2odprJfSpI8qFRmXVVezO+mnShkDhE9k4X0zpnnZbEiKY/4asR0F4gN z5CEoJGxa7p8g== Date: Tue, 20 Sep 2022 07:50:51 +0300 From: Jarkko Sakkinen To: Stefan Berger Cc: Evan Green , linux-kernel@vger.kernel.org, gwendal@chromium.org, Eric Biggers , Matthew Garrett , zohar@linux.ibm.com, linux-integrity@vger.kernel.org, Pavel Machek , apronin@chromium.org, dlunev@google.com, rjw@rjwysocki.net, linux-pm@vger.kernel.org, corbet@lwn.net, jejb@linux.ibm.com, Matthew Garrett , Matthew Garrett , Jason Gunthorpe , Peter Huewe Subject: Re: [PATCH v2 02/10] tpm: Allow PCR 23 to be restricted to kernel-only use Message-ID: References: <20220823222526.1524851-1-evgreen@chromium.org> <20220823152108.v2.2.I9ded8c8caad27403e9284dfc78ad6cbd845bc98d@changeid> <4308c2d0-94ae-8a65-e0c7-69270e31d447@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4308c2d0-94ae-8a65-e0c7-69270e31d447@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Tue, Sep 13, 2022 at 08:26:09AM -0400, Stefan Berger wrote: > > > On 8/23/22 18:25, Evan Green wrote: > > From: Matthew Garrett > > > > Under certain circumstances it might be desirable to enable the creation > > of TPM-backed secrets that are only accessible to the kernel. In an > > ideal world this could be achieved by using TPM localities, but these > > don't appear to be available on consumer systems. An alternative is to > > simply block userland from modifying one of the resettable PCRs, leaving > > it available to the kernel. If the kernel ensures that no userland can > > access the TPM while it is carrying out work, it can reset PCR 23, > > extend it to an arbitrary value, create or load a secret, and then reset > > the PCR again. Even if userland somehow obtains the sealed material, it > > will be unable to unseal it since PCR 23 will never be in the > > appropriate state. > > > > From: Matthew Garrett > > Signed-off-by: Matthew Garrett > > > > Signed-off-by: Evan Green > > --- > > Matthew's original version of this patch is at: > > https://patchwork.kernel.org/patch/12096491/ > > > > Changes in v2: > > - Fixed sparse warnings > > > > drivers/char/tpm/Kconfig | 10 +++++++++ > > drivers/char/tpm/tpm-dev-common.c | 8 +++++++ > > drivers/char/tpm/tpm.h | 21 +++++++++++++++++++ > > drivers/char/tpm/tpm1-cmd.c | 35 +++++++++++++++++++++++++++++++ > > drivers/char/tpm/tpm2-cmd.c | 22 +++++++++++++++++++ > > drivers/char/tpm/tpm2-space.c | 2 +- > > 6 files changed, 97 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig > > index 927088b2c3d3f2..4483b61a428b11 100644 > > --- a/drivers/char/tpm/Kconfig > > +++ b/drivers/char/tpm/Kconfig > > @@ -211,4 +211,14 @@ config TCG_FTPM_TEE > > This driver proxies for firmware TPM running in TEE. > > source "drivers/char/tpm/st33zp24/Kconfig" > > + > > +config TCG_TPM_RESTRICT_PCR > > + bool "Restrict userland access to PCR 23" > > + depends on TCG_TPM > > + help > > + If set, block userland from extending or resetting PCR 23. This > > + allows it to be restricted to in-kernel use, preventing userland > > + from being able to make use of data sealed to the TPM by the kernel. > > + This is required for secure hibernation support, but should be left > > + disabled if any userland may require access to PCR23. > > endif # TCG_TPM > > diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c > > index dc4c0a0a512903..7a4e618c7d1942 100644 > > --- a/drivers/char/tpm/tpm-dev-common.c > > +++ b/drivers/char/tpm/tpm-dev-common.c > > @@ -198,6 +198,14 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, > > priv->response_read = false; > > *off = 0; > > + if (priv->chip->flags & TPM_CHIP_FLAG_TPM2) > > + ret = tpm2_cmd_restricted(priv->chip, priv->data_buffer, size); > > + else > > + ret = tpm1_cmd_restricted(priv->chip, priv->data_buffer, size); > > + > > + if (ret) > > + goto out; > > + > > /* > > * If in nonblocking mode schedule an async job to send > > * the command return the size. > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h > > index a80b341d38eb8c..077c3ca0a127ba 100644 > > --- a/drivers/char/tpm/tpm.h > > +++ b/drivers/char/tpm/tpm.h > > @@ -229,6 +229,8 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type); > > unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal); > > int tpm2_probe(struct tpm_chip *chip); > > int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip); > > +int tpm_find_and_validate_cc(struct tpm_chip *chip, struct tpm_space *space, > > + const void *buf, size_t bufsiz); > > int tpm2_find_cc(struct tpm_chip *chip, u32 cc); > > int tpm2_init_space(struct tpm_space *space, unsigned int buf_size); > > void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space); > > @@ -244,4 +246,23 @@ void tpm_bios_log_setup(struct tpm_chip *chip); > > void tpm_bios_log_teardown(struct tpm_chip *chip); > > int tpm_dev_common_init(void); > > void tpm_dev_common_exit(void); > > + > > +#ifdef CONFIG_TCG_TPM_RESTRICT_PCR > > +#define TPM_RESTRICTED_PCR 23 > > + > > +int tpm1_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size); > > +int tpm2_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size); > > +#else > > +static inline int tpm1_cmd_restricted(struct tpm_chip *chip, u8 *buffer, > > + size_t size) > > +{ > > + return 0; > > +} > > + > > +static inline int tpm2_cmd_restricted(struct tpm_chip *chip, u8 *buffer, > > + size_t size) > > +{ > > + return 0; > > +} > > +#endif > > #endif > > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c > > index 8ec743dec26544..318e75ae42fb85 100644 > > --- a/drivers/char/tpm/tpm1-cmd.c > > +++ b/drivers/char/tpm/tpm1-cmd.c > > @@ -845,3 +845,38 @@ int tpm1_get_pcr_allocation(struct tpm_chip *chip) > > return 0; > > } > > + > > +#ifdef CONFIG_TCG_TPM_RESTRICT_PCR > > +int tpm1_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size) > > +{ > > + struct tpm_header *header = (struct tpm_header *)buffer; > > + char len, offset; > > + __be32 *pcr; > > + int pos; > > + > > + switch (be32_to_cpu(header->ordinal)) { > > + case TPM_ORD_PCR_EXTEND: > > + if (size < (TPM_HEADER_SIZE + sizeof(u32))) > > + return -EINVAL; > > + pcr = (__be32 *)&buffer[TPM_HEADER_SIZE]; > > + if (be32_to_cpu(*pcr) == TPM_RESTRICTED_PCR) > > + return -EPERM; > > FYI: TPM 1.2 has transport sessions where the command is tunneled in an > encrypted channel and this check could be circumvented... BTW, Why do we want to support TPM 1.2 at all. I would not support it for new features. This could be just TPM2 only feeature. BR, Jarkko