keyctl_watch_key(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | LINKING | SEE ALSO | COLOPHON

KEYCTL_GRANT_PERMISSION(3)ux Key Management CallsCTL_GRANT_PERMISSION(3)

NAME         top

       keyctl_watch_key - Watch for changes to a key

SYNOPSIS         top

       #include <keyutils.h>

       long keyctl_watch_key(key_serial_t key,
                             int watch_queue_fd
                             int watch_id);

DESCRIPTION         top

       keyctl_watch_key() sets or removes a watch on key.

       watch_id specifies the ID for a watch that will be included in
       notification messages.  It can be between 0 and 255 to add a key;
       it should be -1 to remove a key.

       watch_queue_fd is a file descriptor attached to a watch_queue
       device instance.  Multiple openings of a device provide separate
       instances.  Each device instance can only have one watch on any
       particular key.

   Notification Record
       Key-specific notification messages that the kernel emits into the
       buffer have the following format:

           struct key_notification {
                struct watch_notification watch;
                __u32     key_id;
                __u32     aux;
           };

       The watch.type field will be set to WATCH_TYPE_KEY_NOTIFY and the
       watch.subtype field will contain one of the following constants,
       indicating the event that occurred and the watch_id passed to
       keyctl_watch_key() will be placed in watch.info in the ID field.
       The following events are defined:

       NOTIFY_KEY_INSTANTIATED
              This indicates that a watched key got instantiated or
              negatively instantiated.  key_id indicates the key that
              was instantiated and aux is unused.

       NOTIFY_KEY_UPDATED
              This indicates that a watched key got updated or
              instantiated by update.  key_id indicates the key that was
              updated and aux is unused.

       NOTIFY_KEY_LINKED
              This indicates that a key got linked into a watched
              keyring.  key_id indicates the keyring that was modified
              aux indicates the key that was added.

       NOTIFY_KEY_UNLINKED
              This indicates that a key got unlinked from a watched
              keyring.  key_id indicates the keyring that was modified
              aux indicates the key that was removed.

       NOTIFY_KEY_CLEARED
              This indicates that a watched keyring got cleared.  key_id
              indicates the keyring that was cleared and aux is unused.

       NOTIFY_KEY_REVOKED
              This indicates that a watched key got revoked.  key_id
              indicates the key that was revoked and aux is unused.

       NOTIFY_KEY_INVALIDATED
              This indicates that a watched key got invalidated.  key_id
              indicates the key that was invalidated and aux is unused.

       NOTIFY_KEY_SETATTR
              This indicates that a watched key had its attributes
              (owner, group, permissions, timeout) modified.  key_id
              indicates the key that was modified and aux is unused.

   Removal Notification
       When a watched key is garbage collected, all of its watches are
       automatically destroyed and a notification is delivered to each
       watcher.  This will normally be an extended notification of the
       form:

           struct watch_notification_removal {
                struct watch_notification watch;
                __u64     id;
           };

       The watch.type field will be set to WATCH_TYPE_META and the
       watch.subtype field will contain WATCH_META_REMOVAL_NOTIFICATION.
       If the extended notification is given, then the length will be 2
       units, otherwise it will be 1 and only the header will be
       present.

       The watch_id passed to keyctl_watch_key() will be placed in
       watch.info in the ID field.

       If the extension is present, id will be set to the ID of the
       destroyed key.

RETURN VALUE         top

       On success keyctl_watch_key() returns 0 .  On error, the value -1
       will be returned and errno will have been set to an appropriate
       error.

ERRORS         top

       ENOKEY The specified key does not exist.

       EKEYEXPIRED
              The specified key has expired.

       EKEYREVOKED
              The specified key has been revoked.

       EACCES The named key exists, but does not grant view permission
              to the calling process.

       EBUSY  The specified key already has a watch on it for that
              device instance (add only).

       EBADSLT
              The specified key doesn't have a watch on it (removal
              only).

LINKING         top

       This is a library function that can be found in libkeyutils.
       When linking, -lkeyutils should be specified to the linker.

SEE ALSO         top

       keyctl(1), add_key(2), keyctl(2), request_key(2), keyctl(3),
       keyrings(7), keyutils(7)

COLOPHON         top

       This page is part of the keyutils (key management utilities)
       project.  Information about the project can be found at [unknown
       -- if you know, please contact man-pages@man7.org] If you have a
       bug report for this manual page, send it to
       keyrings@linux-nfs.org.  This page was obtained from the
       project's upstream Git repository
       ⟨http://git.kernel.org/pub/scm/linux/kernel/git/dhowells/keyutils.git⟩
       on 2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2020-07-07.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

Linux                          28 Aug 2019    KEYCTL_GRANT_PERMISSION(3)

Pages that refer to this page: keyctl(3)