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-rw-r--r--Documentation/security/keys/core.rst57
1 files changed, 57 insertions, 0 deletions
diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst
index 9367d0fe4a02..cdc42ccc12e4 100644
--- a/Documentation/security/keys/core.rst
+++ b/Documentation/security/keys/core.rst
@@ -1030,6 +1030,63 @@ The keyctl syscall functions are:
written into the output buffer. Verification returns 0 on success.
+ * Watch a key or keyring for changes::
+
+ long keyctl(KEYCTL_WATCH_KEY, key_serial_t key, int queue_fd,
+ const struct watch_notification_filter *filter);
+
+ This will set or remove a watch for changes on the specified key or
+ keyring.
+
+ "key" is the ID of the key to be watched.
+
+ "queue_fd" is a file descriptor referring to an open "/dev/watch_queue"
+ which manages the buffer into which notifications will be delivered.
+
+ "filter" is either NULL to remove a watch or a filter specification to
+ indicate what events are required from the key.
+
+ See Documentation/watch_queue.rst for more information.
+
+ Note that only one watch may be emplaced for any particular { key,
+ queue_fd } combination.
+
+ Notification records look like::
+
+ struct key_notification {
+ struct watch_notification watch;
+ __u32 key_id;
+ __u32 aux;
+ };
+
+ In this, watch::type will be "WATCH_TYPE_KEY_NOTIFY" and subtype will be
+ one of::
+
+ NOTIFY_KEY_INSTANTIATED
+ NOTIFY_KEY_UPDATED
+ NOTIFY_KEY_LINKED
+ NOTIFY_KEY_UNLINKED
+ NOTIFY_KEY_CLEARED
+ NOTIFY_KEY_REVOKED
+ NOTIFY_KEY_INVALIDATED
+ NOTIFY_KEY_SETATTR
+
+ Where these indicate a key being instantiated/rejected, updated, a link
+ being made in a keyring, a link being removed from a keyring, a keyring
+ being cleared, a key being revoked, a key being invalidated or a key
+ having one of its attributes changed (user, group, perm, timeout,
+ restriction).
+
+ If a watched key is deleted, a basic watch_notification will be issued
+ with "type" set to WATCH_TYPE_META and "subtype" set to
+ watch_meta_removal_notification. The watchpoint ID will be set in the
+ "info" field.
+
+ This needs to be configured by enabling:
+
+ "Provide key/keyring change notifications" (KEY_NOTIFICATIONS)
+
+
Kernel Services
===============