[PATCH v1 6/6] KEYS: measure keys when they are created or updated

Lakshmi Ramasubramanian
2019-10-23T00:18:39Z

A new LSM function namely, security_key_create_or_update, has
been added. This function is called by key_create_or_update
function when a new key is created or an existing key is updated.
This call is made when the key has been instantiated and linked
to the target keyring.

security_key_create_or_update is passed the target keyring, key,
key creation flags, and a boolean flag indicating whether
the key was newly created or an existing key was updated.
This function calls the ima function ima_post_key_create_or_update
to measure the key.

Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
---
include/linux/ima.h | 15 +++++++-
include/linux/security.h | 13 ++++++-
security/keys/key.c | 78 +++++++++++++++++++++++++++++++++++-----
security/security.c | 10 ++++++
4 files changed, 105 insertions(+), 11 deletions(-)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index a20ad398d260..ce763901380d 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -24,7 +24,11 @@ extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
enum kernel_read_file_id id);
extern void ima_post_path_mknod(struct dentry *dentry);
extern void ima_kexec_cmdline(const void *buf, int size);
-
+extern int ima_post_key_create_or_update(struct key *keyring,
+ struct key *key,
+ const struct cred *cred,
+ unsigned long flags,
+ bool create);
#ifdef CONFIG_IMA_KEXEC
extern void ima_add_kexec_buffer(struct kimage *image);
#endif
@@ -91,6 +95,15 @@ static inline void ima_post_path_mknod(struct dentry *dentry)
}

static inline void ima_kexec_cmdline(const void *buf, int size) {}
+
+static inline int ima_post_key_create_or_update(struct key *keyring,
+ struct key *key,
+ const struct cred *cred,
+ unsigned long flags,
+ bool create)
+{
+ return 0;
+}
#endif /* CONFIG_IMA */

#ifndef CONFIG_IMA_KEXEC
diff --git a/include/linux/security.h b/include/linux/security.h
index 5f7441abbf42..c8348da3db2e 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1677,7 +1677,9 @@ void security_key_free(struct key *key);
int security_key_permission(key_ref_t key_ref,
const struct cred *cred, unsigned perm);
int security_key_getsecurity(struct key *key, char **_buffer);
-
+int security_key_create_or_update(struct key *keyring, struct key *key,
+ const struct cred *cred,
+ unsigned long flags, bool create);
#else

static inline int security_key_alloc(struct key *key,
@@ -1704,6 +1706,15 @@ static inline int security_key_getsecurity(struct key *key, char **_buffer)
return 0;
}

+static inline int security_key_create_or_update(struct key *keyring,
+ struct key *key,
+ const struct cred *cred,
+ unsigned long flags,
+ bool create)
+{
+ return 0;
+}
+
#endif
#endif /* CONFIG_KEYS */

diff --git a/security/keys/key.c b/security/keys/key.c
index 764f4c57913e..b913feaf196e 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -781,7 +781,7 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
}

/**
- * key_create_or_update - Update or create and instantiate a key.
+ * __key_create_or_update - Update or create and instantiate a key.
* @keyring_ref: A pointer to the destination keyring with possession flag.
* @type: The type of key.
* @description: The searchable description for the key.
@@ -789,6 +789,8 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
* @plen: The length of @payload.
* @perm: The permissions mask for a new key.
* @flags: The quota flags for a new key.
+ * @create: Set to true if the key was newly created.
+ * Set to false if the key was updated.
*
* Search the destination keyring for a key of the same description and if one
* is found, update it, otherwise create and instantiate a new one and create a
@@ -805,13 +807,14 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
* On success, the possession flag from the keyring ref will be tacked on to
* the key ref before it is returned.
*/
-key_ref_t key_create_or_update(key_ref_t keyring_ref,
- const char *type,
- const char *description,
- const void *payload,
- size_t plen,
- key_perm_t perm,
- unsigned long flags)
+static key_ref_t __key_create_or_update(key_ref_t keyring_ref,
+ const char *type,
+ const char *description,
+ const void *payload,
+ size_t plen,
+ key_perm_t perm,
+ unsigned long flags,
+ bool *create)
{
struct keyring_index_key index_key = {
.description = description,
@@ -936,6 +939,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
goto error_link_end;
}

+ *create = true;
key_ref = make_key_ref(key, is_key_possessed(keyring_ref));

error_link_end:
@@ -948,7 +952,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
error:
return key_ref;

- found_matching_key:
+found_matching_key:
/* we found a matching key, so we're going to try to update it
* - we can drop the locks first as we have the key pinned
*/
@@ -964,9 +968,65 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
}
}

+ *create = false;
key_ref = __key_update(key_ref, &prep);
goto error_free_prep;
}
+
+/**
+ * key_create_or_update - Update or create and instantiate a key.
+ * @keyring_ref: A pointer to the destination keyring with possession flag.
+ * @type: The type of key.
+ * @description: The searchable description for the key.
+ * @payload: The data to use to instantiate or update the key.
+ * @plen: The length of @payload.
+ * @perm: The permissions mask for a new key.
+ * @flags: The quota flags for a new key.
+ *
+ * Calls the internal function __key_create_or_update.
+ * If successful calls the security LSM hook.
+ */
+key_ref_t key_create_or_update(key_ref_t keyring_ref,
+ const char *type,
+ const char *description,
+ const void *payload,
+ size_t plen,
+ key_perm_t perm,
+ unsigned long flags)
+{
+ key_ref_t key_ref;
+ struct key *keyring, *key = NULL;
+ int ret = 0;
+ bool create = false;
+
+ key_ref = __key_create_or_update(keyring_ref, type, description,
+ payload, plen, perm, flags,
+ &create);
+ if (IS_ERR(key_ref))
+ goto out;
+
+ keyring = key_ref_to_ptr(keyring_ref);
+ key = key_ref_to_ptr(key_ref);
+
+ /* let the security module know about
+ * the created or updated key.
+ */
+ ret = security_key_create_or_update(keyring, key,
+ current_cred(),
+ flags, create);
+ if (ret < 0)
+ goto security_error;
+ else
+ goto out;
+
+security_error:
+ key_unlink(keyring, key);
+ key_put(key);
+ key_ref = ERR_PTR(ret);
+
+out:
+ return key_ref;
+}
EXPORT_SYMBOL(key_create_or_update);

/**
diff --git a/security/security.c b/security/security.c
index 250ee2d76406..707a9e7fa94d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -2303,6 +2303,16 @@ int security_key_getsecurity(struct key *key, char **_buffer)
return call_int_hook(key_getsecurity, 0, key, _buffer);
}

+int security_key_create_or_update(struct key *keyring,
+ struct key *key,
+ const struct cred *cred,
+ unsigned long flags,
+ bool create)
+{
+ return ima_post_key_create_or_update(keyring, key, cred,
+ flags, create);
+}
+
#endif /* CONFIG_KEYS */

#ifdef CONFIG_AUDIT
--
2.17.1