Re: [PATCH v3 3/3] ima: enable loading of build time generated key on .ima keyring

[Stefan Berger <stefanb@xxxxxxxxxxxxx>]

On 3/30/21 9:16 AM, Nayna Jain wrote:
> The kernel currently only loads the kernel module signing key onto the
> builtin trusted keyring. Load the module signing key onto the IMA keyring
> as well.
>
> Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
Acked-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> ---
>   certs/system_certificates.S   | 13 +++++++++-
>   certs/system_keyring.c        | 47 +++++++++++++++++++++++++++--------
>   include/keys/system_keyring.h |  7 ++++++
>   security/integrity/digsig.c   |  2 ++
>   4 files changed, 58 insertions(+), 11 deletions(-)
>
> diff --git a/certs/system_certificates.S b/certs/system_certificates.S
> index 8f29058adf93..dcad27ea8527 100644
> --- a/certs/system_certificates.S
> +++ b/certs/system_certificates.S
> @@ -8,9 +8,11 @@
>   	.globl system_certificate_list
>   system_certificate_list:
>   __cert_list_start:
> -#ifdef CONFIG_MODULE_SIG
> +__module_cert_start:
> +#if defined(CONFIG_MODULE_SIG) || defined(CONFIG_IMA_APPRAISE_MODSIG)
>   	.incbin "certs/signing_key.x509"
>   #endif
> +__module_cert_end:
>   	.incbin "certs/x509_certificate_list"
>   __cert_list_end:
>   
> @@ -35,3 +37,12 @@ system_certificate_list_size:
>   #else
>   	.long __cert_list_end - __cert_list_start
>   #endif
> +
> +	.align 8
> +	.globl module_cert_size
> +module_cert_size:
> +#ifdef CONFIG_64BIT
> +	.quad __module_cert_end - __module_cert_start
> +#else
> +	.long __module_cert_end - __module_cert_start
> +#endif
> diff --git a/certs/system_keyring.c b/certs/system_keyring.c
> index 4b693da488f1..bb122bf4cc17 100644
> --- a/certs/system_keyring.c
> +++ b/certs/system_keyring.c
> @@ -27,6 +27,7 @@ static struct key *platform_trusted_keys;
>   
>   extern __initconst const u8 system_certificate_list[];
>   extern __initconst const unsigned long system_certificate_list_size;
> +extern __initconst const unsigned long module_cert_size;
>   
>   /**
>    * restrict_link_to_builtin_trusted - Restrict keyring addition by built in CA
> @@ -132,19 +133,11 @@ static __init int system_trusted_keyring_init(void)
>    */
>   device_initcall(system_trusted_keyring_init);
>   
> -/*
> - * Load the compiled-in list of X.509 certificates.
> - */
> -static __init int load_system_certificate_list(void)
> +static __init int load_cert(const u8 *p, const u8 *end, struct key *keyring)
>   {
>   	key_ref_t key;
> -	const u8 *p, *end;
>   	size_t plen;
>   
> -	pr_notice("Loading compiled-in X.509 certificates\n");
> -
> -	p = system_certificate_list;
> -	end = p + system_certificate_list_size;
>   	while (p < end) {
>   		/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
>   		 * than 256 bytes in size.
> @@ -159,7 +152,7 @@ static __init int load_system_certificate_list(void)
>   		if (plen > end - p)
>   			goto dodgy_cert;
>   
> -		key = key_create_or_update(make_key_ref(builtin_trusted_keys, 1),
> +		key = key_create_or_update(make_key_ref(keyring, 1),
>   					   "asymmetric",
>   					   NULL,
>   					   p,
> @@ -186,6 +179,40 @@ static __init int load_system_certificate_list(void)
>   	pr_err("Problem parsing in-kernel X.509 certificate list\n");
>   	return 0;
>   }
> +
> +__init int load_module_cert(struct key *keyring)
> +{
> +	const u8 *p, *end;
> +
> +	if (!IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG))
> +		return 0;
> +
> +	pr_notice("Loading compiled-in module X.509 certificates\n");
> +
> +	p = system_certificate_list;
> +	end = p + module_cert_size;
> +
> +	return load_cert(p, end, keyring);
> +}
> +
> +/*
> + * Load the compiled-in list of X.509 certificates.
> + */
> +static __init int load_system_certificate_list(void)
> +{
> +	const u8 *p, *end;
> +
> +	pr_notice("Loading compiled-in X.509 certificates\n");
> +
> +#ifdef CONFIG_MODULE_SIG
> +	p = system_certificate_list;
> +#else
> +	p = system_certificate_list + module_cert_size;
> +#endif
> +
> +	end = p + system_certificate_list_size;
> +	return load_cert(p, end, builtin_trusted_keys);
> +}
>   late_initcall(load_system_certificate_list);
>   
>   #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
> diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
> index fb8b07daa9d1..f954276c616a 100644
> --- a/include/keys/system_keyring.h
> +++ b/include/keys/system_keyring.h
> @@ -16,9 +16,16 @@ extern int restrict_link_by_builtin_trusted(struct key *keyring,
>   					    const struct key_type *type,
>   					    const union key_payload *payload,
>   					    struct key *restriction_key);
> +extern __init int load_module_cert(struct key *keyring);
>   
>   #else
>   #define restrict_link_by_builtin_trusted restrict_link_reject
> +
> +static inline __init int load_module_cert(struct key *keyring)
> +{
> +	return 0;
> +}
> +
>   #endif
>   
>   #ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
> diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
> index 250fb0836156..3b06a01bd0fd 100644
> --- a/security/integrity/digsig.c
> +++ b/security/integrity/digsig.c
> @@ -111,6 +111,8 @@ 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_IMA)
> +			load_module_cert(keyring[id]);
>   	}
>   
>   	return err;