NAME

       KEYCTL_SETPERM - change the permissions mask on a key

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <linux/keyctl.h>  /* Definition of KEY* constants */
       #include <sys/syscall.h>   /* Definition of SYS_* constants */
       #include <unistd.h>

       long syscall(SYS_keyctl, KEYCTL_SETPERM, key_serial_t key,
                    key_perm_t perms);

DESCRIPTION

       Change the permissions of the key with the ID provided in the key argument to the permissions provided in
       the perms argument.

       If  the  caller doesn't have the CAP_SYS_ADMIN capability, it can change permissions only for the keys it
       owns.  (More precisely: the caller's filesystem UID must match the UID of the key.)

       The key must grant setattr permission to the caller regardless of the caller's capabilities.

       The permissions in perms specify masks of available operations for each of the following user categories:

       possessor (since Linux 2.6.14)
              This is the permission granted to a process that possesses the key (has it attached searchably  to
              one of the process's keyrings); see keyrings(7).

       user   This is the permission granted to a process whose filesystem UID matches the UID of the key.

       group  This  is the permission granted to a process whose filesystem GID or any of its supplementary GIDs
              matches the GID of the key.

       other  This is the permission granted to other processes that do not match the user and group categories.

       The user, group, and other categories are exclusive: if a process matches the user category, it will  not
       receive  permissions granted in the group category; if a process matches the user or group category, then
       it will not receive permissions granted in the other category.

       The possessor category grants permissions that are cumulative with the grants from the  user,  group,  or
       other category.

       Each permission mask is eight bits in size, with only six bits currently used.  The available permissions
       are:

       view   This permission allows reading attributes of a key.

              This permission is required for the KEYCTL_DESCRIBE(2const) operation.

       The permission bits for each category are:

              KEY_POS_VIEW
              KEY_USR_VIEW
              KEY_GRP_VIEW
              KEY_OTH_VIEW

       read   This permission allows reading a key's payload.

              This permission is required for the KEYCTL_READ(2const) operation.

              The permission bits for each category are

              KEY_POS_READ
              KEY_USR_READ
              KEY_GRP_READ
              KEY_OTH_READ

       write  This  permission allows update or instantiation of a key's payload.  For a keyring, it allows keys
              to be linked and unlinked from the keyring,

              This   permission   is   required   for    the    KEYCTL_UPDATE(2const),    KEYCTL_REVOKE(2const),
              KEYCTL_CLEAR(2const), KEYCTL_LINK(2const), and KEYCTL_UNLINK(2const) operations.

              The permission bits for each category are:

              KEY_POS_WRITE
              KEY_USR_WRITE
              KEY_GRP_WRITE
              KEY_OTH_WRITE

       search This  permission  allows  keyrings to be searched and keys to be found.  Searches can recurse only
              into nested keyrings that have search permission set.

              This      permission      is      required      for       the       KEYCTL_GET_KEYRING_ID(2const),
              KEYCTL_JOIN_SESSION_KEYRING(2const),   KEYCTL_SEARCH(2const),   and   KEYCTL_INVALIDATE   (2const)
              operations.

              The permission bits for each category are:

              KEY_POS_SEARCH
              KEY_USR_SEARCH
              KEY_GRP_SEARCH
              KEY_OTH_SEARCH

       link   This permission allows a key or keyring to be linked to.

              This permission is  required  for  the  KEYCTL_LINK(2const)  and  KEYCTL_SESSION_TO_PARENT(2const)
              operations.

              The permission bits for each category are:

              KEY_POS_LINK
              KEY_USR_LINK
              KEY_GRP_LINK
              KEY_OTH_LINK

       setattr (since Linux 2.6.15)
              This permission allows a key's UID, GID, and permissions mask to be changed.

              This   permission   is   required   for   the   KEYCTL_REVOKE(2const),  KEYCTL_CHOWN(2const),  and
              KEYCTL_SETPERM (2const) operations.

              The permission bits for each category are:

              KEY_POS_SETATTR
              KEY_USR_SETATTR
              KEY_GRP_SETATTR
              KEY_OTH_SETATTR

       As a convenience, the following macros are defined as masks for all of the permission bits in each of the
       user categories:

              KEY_POS_ALL
              KEY_USR_ALL
              KEY_GRP_ALL
              KEY_OTH_ALL

RETURN VALUE

       On success, 0 is returned.

       On error, -1 is returned, and errno is set to indicate the error.

ERRORS

       EINVAL operation was KEYCTL_SETPERM and an invalid permission bit was specified in perms.

VERSIONS

       A wrapper is provided in the libkeyutils library: keyctl_setperm(3).

STANDARDS

       Linux.

HISTORY

       Linux 2.6.10.

SEE ALSO

       keyctl(2), keyctl_setperm(3)

Linux man-pages 6.16                               2025-09-21                             KEYCTL_SETPERM(2const)