linux-kernel - Re: [PATCH v8 17/17] integrity: Only use machine keyring when uefi_check_trust_mok

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Date:   Mon, 14 Feb 2022 12:37:01 +0000
From:   Darren Kenny <darren.kenny@...cle.com>
To:     Eric Snowberg <eric.snowberg@...cle.com>, keyrings@...r.kernel.org,
        linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
        dhowells@...hat.com, dwmw2@...radead.org,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jarkko@...nel.org, jmorris@...ei.org, serge@...lyn.com
Cc:     eric.snowberg@...cle.com, keescook@...omium.org,
        torvalds@...ux-foundation.org, weiyongjun1@...wei.com,
        nayna@...ux.ibm.com, ebiggers@...gle.com, ardb@...nel.org,
        nramas@...ux.microsoft.com, lszubowi@...hat.com, jason@...c4.com,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-security-module@...r.kernel.org,
        James.Bottomley@...senPartnership.com, pjones@...hat.com,
        konrad.wilk@...cle.com
Subject: Re: [PATCH v8 17/17] integrity: Only use machine keyring when
 uefi_check_trust_mok_keys is true

On Tuesday, 2021-11-23 at 23:41:24 -05, Eric Snowberg wrote:
> With the introduction of uefi_check_trust_mok_keys, it signifies the end-
> user wants to trust the machine keyring as trusted keys.  If they have
> chosen to trust the machine keyring, load the qualifying keys into it
> during boot, then link it to the secondary keyring .  If the user has not
> chosen to trust the machine keyring, it will be empty and not linked to
> the secondary keyring.
>
> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>

Reviewed-by: Darren Kenny <darren.kenny@...cle.com>

> ---
> v4: Initial version
> v5: Rename to machine keyring
> v6: Unmodified from v5
> v7: Made trust_mok static
> v8: Unmodified from v7
> ---
>  security/integrity/digsig.c                      |  2 +-
>  security/integrity/integrity.h                   |  5 +++++
>  .../integrity/platform_certs/keyring_handler.c   |  2 +-
>  .../integrity/platform_certs/machine_keyring.c   | 16 ++++++++++++++++
>  4 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> index 109b58840d45..1de09c7b5f93 100644
> --- a/security/integrity/digsig.c
> +++ b/security/integrity/digsig.c
> @@ -116,7 +116,7 @@ static int __init __integrity_init_keyring(const unsigned int id,
>  	} else {
>  		if (id == INTEGRITY_KEYRING_PLATFORM)
>  			set_platform_trusted_keys(keyring[id]);
> -		if (id == INTEGRITY_KEYRING_MACHINE)
> +		if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
>  			set_machine_trusted_keys(keyring[id]);
>  		if (id == INTEGRITY_KEYRING_IMA)
>  			load_module_cert(keyring[id]);
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 730771eececd..2e214c761158 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -287,9 +287,14 @@ static inline void __init add_to_platform_keyring(const char *source,
>  
>  #ifdef CONFIG_INTEGRITY_MACHINE_KEYRING
>  void __init add_to_machine_keyring(const char *source, const void *data, size_t len);
> +bool __init trust_moklist(void);
>  #else
>  static inline void __init add_to_machine_keyring(const char *source,
>  						  const void *data, size_t len)
>  {
>  }
> +static inline bool __init trust_moklist(void)
> +{
> +	return false;
> +}
>  #endif
> diff --git a/security/integrity/platform_certs/keyring_handler.c b/security/integrity/platform_certs/keyring_handler.c
> index 4872850d081f..1db4d3b4356d 100644
> --- a/security/integrity/platform_certs/keyring_handler.c
> +++ b/security/integrity/platform_certs/keyring_handler.c
> @@ -83,7 +83,7 @@ __init efi_element_handler_t get_handler_for_db(const efi_guid_t *sig_type)
>  __init efi_element_handler_t get_handler_for_mok(const efi_guid_t *sig_type)
>  {
>  	if (efi_guidcmp(*sig_type, efi_cert_x509_guid) == 0) {
> -		if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING))
> +		if (IS_ENABLED(CONFIG_INTEGRITY_MACHINE_KEYRING) && trust_moklist())
>  			return add_to_machine_keyring;
>  		else
>  			return add_to_platform_keyring;
> diff --git a/security/integrity/platform_certs/machine_keyring.c b/security/integrity/platform_certs/machine_keyring.c
> index 09fd8f20c756..7aaed7950b6e 100644
> --- a/security/integrity/platform_certs/machine_keyring.c
> +++ b/security/integrity/platform_certs/machine_keyring.c
> @@ -8,6 +8,8 @@
>  #include <linux/efi.h>
>  #include "../integrity.h"
>  
> +static bool trust_mok;
> +
>  static __init int machine_keyring_init(void)
>  {
>  	int rc;
> @@ -59,3 +61,17 @@ static __init bool uefi_check_trust_mok_keys(void)
>  
>  	return false;
>  }
> +
> +bool __init trust_moklist(void)
> +{
> +	static bool initialized;
> +
> +	if (!initialized) {
> +		initialized = true;
> +
> +		if (uefi_check_trust_mok_keys())
> +			trust_mok = true;
> +	}
> +
> +	return trust_mok;
> +}
> -- 
> 2.18.4