linux-kernel - Re: [PATCH v3 1/2] integrity, KEYS: add a reference to platform keyring

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Message-Id: <1547767245.3931.56.camel@linux.ibm.com>
Date:   Thu, 17 Jan 2019 18:20:45 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Kairui Song <kasong@...hat.com>, linux-kernel@...r.kernel.org
Cc:     dhowells@...hat.com, dwmw2@...radead.org,
        jwboyer@...oraproject.org, keyrings@...r.kernel.org,
        jmorris@...ei.org, serge@...lyn.com, bauerman@...ux.ibm.com,
        ebiggers@...gle.com, nayna@...ux.ibm.com, dyoung@...hat.com,
        linux-integrity@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] integrity, KEYS: add a reference to platform
 keyring

On Wed, 2019-01-16 at 18:16 +0800, Kairui Song wrote:
> Currently when loading new kernel via kexec_file_load syscall, it is able
> to verify the signed PE bzimage against .builtin_trusted_keys or
> .secondary_trusted_keys. But the image could be signed with third part
> keys which will be provided by platform or firmware as EFI variable (eg.
> stored in MokListRT EFI variable), and the keys won't be available in
> keyrings mentioned above.
> 
> After commit 9dc92c45177a ('integrity: Define a trusted platform keyring')
> a .platform keyring is introduced to store the keys provided by platform
> or firmware, this keyring is intended to be used for verifying kernel
> images being loaded by kexec_file_load syscall. And with a few following
> up commits, keys provided by firmware is being loaded into this keyring,
> and IMA-appraisal is able to use the keyring to verify kernel images.
> IMA is the currently the only user of that keyring.

How about simply saying, Commit "...." introduced a platform keyring
for storing preboot keys, used for verifying the kexec kernel image's
signature.

> This patch exposes the .platform, and makes it useable for other
> components. For example, kexec_file_load could use this .platform
> keyring to verify the kernel image's image.

The above statement is too generic.  Please replace "and makes it 
useable for other components" with " keyring, making it accessible for
verifying a PE signed kernel image".

> 
> Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
> Signed-off-by: Kairui Song <kasong@...hat.com>

Reviewed/Tested-by: Mimi Zohar <zohar@...ux.ibm.com>
> ---
>  certs/system_keyring.c        | 9 +++++++++
>  include/keys/system_keyring.h | 5 +++++
>  security/integrity/digsig.c   | 6 ++++++
>  3 files changed, 20 insertions(+)
> 
> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> index 81728717523d..4690ef9cda8a 100644
> --- a/certs/system_keyring.c
> +++ b/certs/system_keyring.c
> @@ -24,6 +24,9 @@ static struct key *builtin_trusted_keys;
>  #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
>  static struct key *secondary_trusted_keys;
>  #endif
> +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> +static struct key *platform_trusted_keys;
> +#endif
>  
>  extern __initconst const u8 system_certificate_list[];
>  extern __initconst const unsigned long system_certificate_list_size;
> @@ -265,4 +268,10 @@ int verify_pkcs7_signature(const void *data, size_t len,
>  }
>  EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
>  
> +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> +void __init set_platform_trusted_keys(struct key *keyring) {
> +	platform_trusted_keys = keyring;
> +}
> +#endif
> +
>  #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
> diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
> index 359c2f936004..9e1b7849b6aa 100644
> --- a/include/keys/system_keyring.h
> +++ b/include/keys/system_keyring.h
> @@ -61,5 +61,10 @@ static inline struct key *get_ima_blacklist_keyring(void)
>  }
>  #endif /* CONFIG_IMA_BLACKLIST_KEYRING */
>  
> +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> +
> +extern void __init set_platform_trusted_keys(struct key* keyring);
> +
> +#endif /* CONFIG_INTEGRITY_PLATFORM_KEYRING */
>  
>  #endif /* _KEYS_SYSTEM_KEYRING_H */
> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> index f45d6edecf99..bfabc2a8111d 100644
> --- a/security/integrity/digsig.c
> +++ b/security/integrity/digsig.c
> @@ -89,6 +89,12 @@ static int __integrity_init_keyring(const unsigned int id, key_perm_t perm,
>  		keyring[id] = NULL;
>  	}
>  
> +#ifdef CONFIG_INTEGRITY_PLATFORM_KEYRING
> +	if (id == INTEGRITY_KEYRING_PLATFORM) {
> +		set_platform_trusted_keys(keyring[id]);
> +	}
> +#endif
> +
>  	return err;
>  }
>