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Message-ID: <CAFA6WYMJp5u_+3bNc0ykFzveakOS4nqJfPvSoaFGQApFctL47A@mail.gmail.com>
Date: Mon, 19 Jul 2021 13:34:07 +0530
From: Sumit Garg <sumit.garg@...aro.org>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>
Cc: James Bottomley <jejb@...ux.ibm.com>,
Jarkko Sakkinen <jarkko@...nel.org>,
Mimi Zohar <zohar@...ux.ibm.com>,
David Howells <dhowells@...hat.com>,
kernel <kernel@...gutronix.de>, James Morris <jmorris@...ei.org>,
Eric Biggers <ebiggers@...nel.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Horia Geantă <horia.geanta@....com>,
Aymen Sghaier <aymen.sghaier@....com>,
Udit Agarwal <udit.agarwal@....com>,
Jan Luebbe <j.luebbe@...gutronix.de>,
David Gstir <david@...ma-star.at>,
Richard Weinberger <richard@....at>,
Franck LENORMAND <franck.lenormand@....com>,
"open list:ASYMMETRIC KEYS" <keyrings@...r.kernel.org>,
"open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
<linux-crypto@...r.kernel.org>,
linux-integrity <linux-integrity@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"open list:SECURITY SUBSYSTEM"
<linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v2 1/6] KEYS: trusted: allow use of TEE as backend without
TCG_TPM support
Hi Ahmad,
On Tue, 22 Jun 2021 at 18:08, Ahmad Fatoum <a.fatoum@...gutronix.de> wrote:
>
> With recent rework, trusted keys are no longer limited to TPM as trust
> source. The Kconfig symbol is unchanged however leading to a few issues:
>
> - TCG_TPM is required, even if only TEE is to be used
> - Enabling TCG_TPM, but excluding it from available trusted sources
> is not possible
> - TEE=m && TRUSTED_KEYS=y will lead to TEE support being silently
> dropped, which is not the best user experience
>
> Remedy these issues by introducing two new Kconfig symbols:
> TRUSTED_KEYS_TPM and TRUSTED_KEYS_TEE with the appropriate
> dependencies.
>
This should include a fixes tag to the rework commit.
> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
> ---
> To: James Bottomley <jejb@...ux.ibm.com>
> To: Jarkko Sakkinen <jarkko@...nel.org>
> To: Mimi Zohar <zohar@...ux.ibm.com>
> To: David Howells <dhowells@...hat.com>
> Cc: James Morris <jmorris@...ei.org>
> Cc: Eric Biggers <ebiggers@...nel.org>
> Cc: "Serge E. Hallyn" <serge@...lyn.com>
> Cc: "Horia Geantă" <horia.geanta@....com>
> Cc: Aymen Sghaier <aymen.sghaier@....com>
> Cc: Udit Agarwal <udit.agarwal@....com>
> Cc: Jan Luebbe <j.luebbe@...gutronix.de>
> Cc: David Gstir <david@...ma-star.at>
> Cc: Richard Weinberger <richard@....at>
> Cc: Franck LENORMAND <franck.lenormand@....com>
> Cc: Sumit Garg <sumit.garg@...aro.org>
> Cc: keyrings@...r.kernel.org
> Cc: linux-crypto@...r.kernel.org
> Cc: linux-integrity@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-security-module@...r.kernel.org
> ---
> security/keys/Kconfig | 14 ++++++-------
> security/keys/trusted-keys/Kconfig | 25 ++++++++++++++++++++++++-
> security/keys/trusted-keys/Makefile | 8 +++++---
> security/keys/trusted-keys/trusted_core.c | 4 ++--
> 4 files changed, 39 insertions(+), 12 deletions(-)
> create mode 100644 security/keys/trusted-keys/Kconfig
>
> diff --git a/security/keys/Kconfig b/security/keys/Kconfig
> index 64b81abd087e..6fdb953b319f 100644
> --- a/security/keys/Kconfig
> +++ b/security/keys/Kconfig
> @@ -70,23 +70,23 @@ config BIG_KEYS
>
> config TRUSTED_KEYS
> tristate "TRUSTED KEYS"
> - depends on KEYS && TCG_TPM
> + depends on KEYS
> select CRYPTO
> select CRYPTO_HMAC
> select CRYPTO_SHA1
> select CRYPTO_HASH_INFO
Should move these as well to TRUSTED_KEYS_TPM as the core code doesn't
mandate their need.
> - select ASN1_ENCODER
> - select OID_REGISTRY
> - select ASN1
> help
> This option provides support for creating, sealing, and unsealing
> keys in the kernel. Trusted keys are random number symmetric keys,
> - generated and RSA-sealed by the TPM. The TPM only unseals the keys,
> - if the boot PCRs and other criteria match. Userspace will only ever
> - see encrypted blobs.
> + generated and sealed by a trust source selected at kernel boot-time.
> + Userspace will only ever see encrypted blobs.
>
> If you are unsure as to whether this is required, answer N.
>
> +if TRUSTED_KEYS
> +source "security/keys/trusted-keys/Kconfig"
> +endif
> +
> config ENCRYPTED_KEYS
> tristate "ENCRYPTED KEYS"
> depends on KEYS
> diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig
> new file mode 100644
> index 000000000000..24af4aaceebf
> --- /dev/null
> +++ b/security/keys/trusted-keys/Kconfig
> @@ -0,0 +1,25 @@
> +config TRUSTED_KEYS_TPM
> + bool "TPM-based trusted keys"
> + depends on TCG_TPM >= TRUSTED_KEYS
> + default y
> + select ASN1_ENCODER
> + select OID_REGISTRY
> + select ASN1
> + help
> + Enable use of the Trusted Platform Module (TPM) as trusted key
> + backend. Trusted keys are are random number symmetric keys,
> + which will be generated and RSA-sealed by the TPM.
> + The TPM only unseals the keys, if the boot PCRs and other
> + criteria match.
> +
> +config TRUSTED_KEYS_TEE
> + bool "TEE-based trusted keys"
> + depends on TEE >= TRUSTED_KEYS
> + default y
> + help
> + Enable use of the Trusted Execution Environment (TEE) as trusted
> + key backend.
> +
> +if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE
> +comment "No trust source selected!"
> +endif
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
> index feb8b6c3cc79..96fc6c377398 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -5,10 +5,12 @@
>
> obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
> trusted-y += trusted_core.o
> -trusted-y += trusted_tpm1.o
> +trusted-$(CONFIG_TRUSTED_KEYS_TPM) += trusted_tpm1.o
>
> $(obj)/trusted_tpm2.o: $(obj)/tpm2key.asn1.h
> -trusted-y += trusted_tpm2.o
> -trusted-y += tpm2key.asn1.o
> +trusted-$(CONFIG_TRUSTED_KEYS_TPM) += trusted_tpm2.o
> +trusted-$(CONFIG_TRUSTED_KEYS_TPM) += tpm2key.asn1.o
> +
> +trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
>
> trusted-$(CONFIG_TEE) += trusted_tee.o
This should be dropped.
-Sumit
> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index d5c891d8d353..8cab69e5d0da 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -27,10 +27,10 @@ module_param_named(source, trusted_key_source, charp, 0);
> MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)");
>
> static const struct trusted_key_source trusted_key_sources[] = {
> -#if defined(CONFIG_TCG_TPM)
> +#if defined(CONFIG_TRUSTED_KEYS_TPM)
> { "tpm", &trusted_key_tpm_ops },
> #endif
> -#if defined(CONFIG_TEE)
> +#if defined(CONFIG_TRUSTED_KEYS_TEE)
> { "tee", &trusted_key_tee_ops },
> #endif
> };
> --
> git-series 0.9.1
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