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

Roberto Sassu
2023-09-04T13:42:27Z

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 ++++++-
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
--
2.34.1