Re: [PATCH v2 20/25] security: Introduce key_post_create_or_update hook

[Casey Schaufler]

On 8/31/2023 4:37 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the key_post_create_or_update hook.

Repeat of new LSM hook general comment:
Would you please include some explanation of how an LSM would use this hook?
You might start with a description of how it is used in IMA/EVM, and why that
could be generally useful.


>
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> ---
>  include/linux/lsm_hook_defs.h |  3 +++
>  include/linux/security.h      | 11 +++++++++++
>  security/keys/key.c           |  7 ++++++-
>  security/security.c           | 19 +++++++++++++++++++
>  4 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index eedc26790a07..7512b4c46aa8 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -399,6 +399,9 @@ LSM_HOOK(void, LSM_RET_VOID, key_free, struct key *key)
>  LSM_HOOK(int, 0, key_permission, key_ref_t key_ref, const struct cred *cred,
>  	 enum key_need_perm need_perm)
>  LSM_HOOK(int, 0, key_getsecurity, struct key *key, char **buffer)
> +LSM_HOOK(void, LSM_RET_VOID, key_post_create_or_update, struct key *keyring,
> +	 struct key *key, const void *payload, size_t payload_len,
> +	 unsigned long flags, bool create)
>  #endif /* CONFIG_KEYS */
>  
>  #ifdef CONFIG_AUDIT
> diff --git a/include/linux/security.h b/include/linux/security.h
> index e543ae80309b..f50b78481753 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -1959,6 +1959,9 @@ void security_key_free(struct key *key);
>  int security_key_permission(key_ref_t key_ref, const struct cred *cred,
>  			    enum key_need_perm need_perm);
>  int security_key_getsecurity(struct key *key, char **_buffer);
> +void security_key_post_create_or_update(struct key *keyring, struct key *key,
> +					const void *payload, size_t payload_len,
> +					unsigned long flags, bool create);
>  
>  #else
>  
> @@ -1986,6 +1989,14 @@ static inline int security_key_getsecurity(struct key *key, char **_buffer)
>  	return 0;
>  }
>  
> +static inline void security_key_post_create_or_update(struct key *keyring,
> +						      struct key *key,
> +						      const void *payload,
> +						      size_t payload_len,
> +						      unsigned long flags,
> +						      bool create)
> +{ }
> +
>  #endif
>  #endif /* CONFIG_KEYS */
>  
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 5c0c7df833f8..0f9c6faf3491 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -934,6 +934,8 @@ static key_ref_t __key_create_or_update(key_ref_t keyring_ref,
>  		goto error_link_end;
>  	}
>  
> +	security_key_post_create_or_update(keyring, key, payload, plen, flags,
> +					   true);
>  	ima_post_key_create_or_update(keyring, key, payload, plen,
>  				      flags, true);
>  
> @@ -967,10 +969,13 @@ static key_ref_t __key_create_or_update(key_ref_t keyring_ref,
>  
>  	key_ref = __key_update(key_ref, &prep);
>  
> -	if (!IS_ERR(key_ref))
> +	if (!IS_ERR(key_ref)) {
> +		security_key_post_create_or_update(keyring, key, payload, plen,
> +						   flags, false);
>  		ima_post_key_create_or_update(keyring, key,
>  					      payload, plen,
>  					      flags, false);
> +	}
>  
>  	goto error_free_prep;
>  }
> diff --git a/security/security.c b/security/security.c
> index 32c3dc34432e..e6783c2f0c65 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -5169,6 +5169,25 @@ int security_key_getsecurity(struct key *key, char **buffer)
>  	*buffer = NULL;
>  	return call_int_hook(key_getsecurity, 0, key, buffer);
>  }
> +
> +/**
> + * security_key_post_create_or_update() - Notification of key create or update
> + * @keyring: keyring to which the key is linked to
> + * @key: created or updated key
> + * @payload: data used to instantiate or update the key
> + * @payload_len: length of payload
> + * @flags: key flags
> + * @create: flag indicating whether the key was created or updated
> + *
> + * Notify the caller of a key creation or update.
> + */
> +void security_key_post_create_or_update(struct key *keyring, struct key *key,
> +					const void *payload, size_t payload_len,
> +					unsigned long flags, bool create)
> +{
> +	call_void_hook(key_post_create_or_update, keyring, key, payload,
> +		       payload_len, flags, create);
> +}
>  #endif	/* CONFIG_KEYS */
>  
>  #ifdef CONFIG_AUDIT