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 CB14BECAAA2 for ; Fri, 26 Aug 2022 03:02:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244929AbiHZDCY (ORCPT ); Thu, 25 Aug 2022 23:02:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244066AbiHZDCS (ORCPT ); Thu, 25 Aug 2022 23:02:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76E89C7429; Thu, 25 Aug 2022 20:02:16 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 5185461E69; Fri, 26 Aug 2022 03:02:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C61FC433C1; Fri, 26 Aug 2022 03:02:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661482934; bh=VbL0nAmH2Klred+v5b72GoaYRxetUy7nlR4YWBVkvWA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VleN9Nv2Blt0CG8NzEm0Z40Adtd5kw/T14v1Oe6ythvlzjIRjhZBfbjQgqVbC2ZWS uhmq2yUGkc6BQUeH0u+MF+5pIZej9oMCrAYJGpOBq2X9B38xA6Bh0imI9KZrcFtB97 k5CDMZARMfVt+mxA7qSuWDNuBmsI3Xd6jl9MPLdydKYa3FJ5NsoFz+Dsj29XxsKSx6 wmkGv34OKFIMvouUGYemphXFZ1OnN++xyV52FJ1dAp2OZif3QpSuWfKrieH+Y1X3Ek 33wSbXjz87Ij8oxKIOf9mFJeYGBbxI+hAXkF4ny6t+rIAp2gby0JOgQCEQ8scuts6Y x1y5NligsbQqg== Date: Fri, 26 Aug 2022 06:02:07 +0300 From: Jarkko Sakkinen To: Evan Green Cc: 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220823152108.v2.2.I9ded8c8caad27403e9284dfc78ad6cbd845bc98d@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 23, 2022 at 03:25:18PM -0700, 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 Same issues as the other patch. > --- > Matthew's original version of this patch is at: > https://patchwork.kernel.org/patch/12096491/ Suggestion: find a lore URL instead for Matthew's patch, and then add "Link: " to your commit before sob's. It's a useful reference also in the commit log. > > 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; > + break; > + case TPM_ORD_PCR_RESET: > + if (size < (TPM_HEADER_SIZE + 1)) > + return -EINVAL; > + len = buffer[TPM_HEADER_SIZE]; > + if (size < (TPM_HEADER_SIZE + 1 + len)) > + return -EINVAL; > + offset = TPM_RESTRICTED_PCR/3; > + if (len < offset) > + break; > + pos = TPM_HEADER_SIZE + 1 + offset; > + if (buffer[pos] & (1 << (TPM_RESTRICTED_PCR - 2 * offset))) > + return -EPERM; > + break; > + } > + > + return 0; > +} > +#endif > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c > index 69126a6770386e..dbf7f5552c6782 100644 > --- a/drivers/char/tpm/tpm2-cmd.c > +++ b/drivers/char/tpm/tpm2-cmd.c > @@ -821,3 +821,25 @@ int tpm2_find_cc(struct tpm_chip *chip, u32 cc) > > return -1; > } > + > +#ifdef CONFIG_TCG_TPM_RESTRICT_PCR > +int tpm2_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size) > +{ > + int cc = tpm_find_and_validate_cc(chip, NULL, buffer, size); > + __be32 *handle; > + > + switch (cc) { > + case TPM2_CC_PCR_EXTEND: > + case TPM2_CC_PCR_RESET: > + if (size < (TPM_HEADER_SIZE + sizeof(u32))) > + return -EINVAL; > + > + handle = (__be32 *)&buffer[TPM_HEADER_SIZE]; > + if (be32_to_cpu(*handle) == TPM_RESTRICTED_PCR) > + return -EPERM; > + break; > + } > + > + return 0; > +} > +#endif > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c > index ffb35f0154c16c..6f51cd92c6400f 100644 > --- a/drivers/char/tpm/tpm2-space.c > +++ b/drivers/char/tpm/tpm2-space.c > @@ -262,7 +262,7 @@ static int tpm2_map_command(struct tpm_chip *chip, u32 cc, u8 *cmd) > return 0; > } > > -static int tpm_find_and_validate_cc(struct tpm_chip *chip, > +int tpm_find_and_validate_cc(struct tpm_chip *chip, > struct tpm_space *space, > const void *cmd, size_t len) Split the export to a separate commit. > { > -- > 2.31.0 > BR, Jarkko