Re: [PATCH v3 20/25] security: Introduce key_post_create_or_update hook

Roberto Sassu
2023-09-26T11:16:37Z

On Mon, 2023-09-04 at 15:40 +0200, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> the key_post_create_or_update hook.
>
> It is useful for IMA to measure the key content after creation or update,
> so that remote verifiers are aware of the operation.
>
> LSMs can benefit from this hook to make their decision on the new or
> successfully updated key content. The new hook cannot return an error and
> cannot cause the operation to be reverted.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> include/linux/lsm_hook_defs.h | 3 +++
> include/linux/security.h | 11 +++++++++++
> security/keys/key.c | 7 ++++++-

Hi David, Jarkko

could you please review and ack this patch?

Thanks a lot!

Roberto

> 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 554f4925323d..957e53ba904f 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