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Message-ID: <9649cec7710241dc359c7c1a715b2cef36ebce15.camel@linux.ibm.com>
Date: Tue, 12 Nov 2024 23:34:07 -0500
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, linux-integrity@...r.kernel.org,
Jonathan Corbet <corbet@....net>, Peter Huewe <peterhuewe@....de>,
Jason
Gunthorpe <jgg@...pe.ca>,
James Bottomley
<James.Bottomley@...senPartnership.com>
Cc: Roberto Sassu <roberto.sassu@...wei.com>,
David Howells
<dhowells@...hat.com>, Paul Moore <paul@...l-moore.com>,
James Morris
<jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>, Thomas Huth
<thuth@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E.
McKenney" <paulmck@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Xiongwei Song <xiongwei.song@...driver.com>,
Stefan Berger
<stefanb@...ux.ibm.com>,
Ard Biesheuvel <ardb@...nel.org>, Al Viro
<viro@...iv.linux.org.uk>,
"open list:DOCUMENTATION"
<linux-doc@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>,
"open list:KEYS-TRUSTED" <keyrings@...r.kernel.org>,
"open list:SECURITY
SUBSYSTEM" <linux-security-module@...r.kernel.org>,
Josh Poimboeuf
<jpoimboe@...nel.org>
Subject: Re: [PATCH v3] tpm: Opt-in in disable PCR integrity protection
On Wed, 2024-11-13 at 02:24 +0200, Jarkko Sakkinen wrote:
> The initial HMAC session feature added TPM bus encryption and/or integrity
> protection to various in-kernel TPM operations. This can cause performance
> bottlenecks with IMA, as it heavily utilizes PCR extend operations.
>
> In order to mitigate this performance issue, introduce a kernel
> command-line parameter to the TPM driver for disabling the integrity
> protection for PCR extend operations (i.e. TPM2_PCR_Extend).
>
> Cc: James Bottomley <James.Bottomley@...senPartnership.com>
> Link: https://lore.kernel.org/linux-integrity/20241015193916.59964-1-zohar@linux.ibm.com/
> Fixes: 6519fea6fd37 ("tpm: add hmac checks to tpm2_pcr_extend()")
> Co-developed-by: Roberto Sassu <roberto.sassu@...wei.com>
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> Co-developed-by: Mimi Zohar <zohar@...ux.ibm.com>
> Signed-off-by: Mimi Zohar <zohar@...ux.ibm.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
The module_param variable documentation needs to be updated to reflect the
actual module_param variable 'disable_pcr_integrity'.
Otherwise,
Tested-by: Mimi Zohar <zohar@...ux.ibm.com>
> ---
> v3:
> - Please test this too ;-) I did quick testing only.
> - Fixed the reported glitches and mistakes.
> v2:
> - Followed Mimi's suggestions.
> ---
> .../admin-guide/kernel-parameters.txt | 9 ++++
> drivers/char/tpm/tpm-buf.c | 20 ++++++++
> drivers/char/tpm/tpm2-cmd.c | 30 ++++++++---
> drivers/char/tpm/tpm2-sessions.c | 51 ++++++++++---------
> include/linux/tpm.h | 3 ++
> 5 files changed, 82 insertions(+), 31 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 1666576acc0e..7107ad322b2e 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -6727,6 +6727,15 @@
> torture.verbose_sleep_duration= [KNL]
> Duration of each verbose-printk() sleep in jiffies.
>
> + tpm.disable_pcr_integrity_protection= [HW,TPM]
-> tpm.disable_pcr_integrity=
> + Do not protect PCR registers from unintended physical
> + access, or interposers in the bus by the means of
> + having an integrity protected session wrapped around
> + TPM2_PCR_Extend command. Consider this in a situation
> + where TPM is heavily utilized by IMA, thus protection
> + causing a major performance hit, and the space where
> + machines are deployed is by other means guarded.
> +
> tpm_suspend_pcr=[HW,TPM]
> Format: integer pcr id
> Specify that at suspend time, the tpm driver
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index cad0048bcc3c..e49a19fea3bd 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -146,6 +146,26 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
> }
> EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
>
> +/**
> + * tpm_buf_append_handle() - Add a handle
> + * @chip: &tpm_chip instance
> + * @buf: &tpm_buf instance
> + * @handle: a TPM object handle
> + *
> + * Add a handle to the buffer, and increase the count tracking the number of
> + * handles in the command buffer. Works only for command buffers.
> + */
> +void tpm_buf_append_handle(struct tpm_chip *chip, struct tpm_buf *buf, u32 handle)
> +{
> + if (buf->flags & TPM_BUF_TPM2B) {
> + dev_err(&chip->dev, "Invalid buffer type (TPM2B)\n");
> + return;
> + }
> +
> + tpm_buf_append_u32(buf, handle);
> + buf->handles++;
> +}
> +
> /**
> * tpm_buf_read() - Read from a TPM buffer
> * @buf: &tpm_buf instance
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 1e856259219e..dfdcbd009720 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -14,6 +14,10 @@
> #include "tpm.h"
> #include <crypto/hash_info.h>
>
> +static bool disable_pcr_integrity;
> +module_param(disable_pcr_integrity, bool, 0444);
> +MODULE_PARM_DESC(disable_pcr_integrity, "Disable integrity protection of TPM2_PCR_Extend");
'disable_pcr_integrity' doesn't match the documentation.
> +
> static struct tpm2_hash tpm2_hash_map[] = {
> {HASH_ALGO_SHA1, TPM_ALG_SHA1},
> {HASH_ALGO_SHA256, TPM_ALG_SHA256},
> @@ -232,18 +236,26 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
thanks,
Mimi
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