NAME

     acl — virtual file system access control lists

SYNOPSIS

     #include <sys/param.h>
     #include <sys/vnode.h>
     #include <sys/acl.h>

     In the kernel configuration file:
     options UFS_ACL

DESCRIPTION

     Access control lists, or ACLs, allow fine-grained specification of rights for vnodes
     representing files and directories.  However, as there are a plethora of file systems with
     differing ACL semantics, the vnode interface is aware only of the syntax of ACLs, relying on
     the underlying file system to implement the details.  Depending on the underlying file
     system, each file or directory may have zero or more ACLs associated with it, named using
     the type field of the appropriate vnode ACL calls: VOP_ACLCHECK(9), VOP_GETACL(9), and
     VOP_SETACL(9).

     Currently, each ACL is represented in-kernel by a fixed-size acl structure, defined as
     follows:

           struct acl {
                   unsigned int            acl_maxcnt;
                   unsigned int            acl_cnt;
                   int                     acl_spare[4];
                   struct acl_entry        acl_entry[ACL_MAX_ENTRIES];
           };

     An ACL is constructed from a fixed size array of ACL entries, each of which consists of a
     set of permissions, principal namespace, and principal identifier.  In this implementation,
     the acl_maxcnt field is always set to ACL_MAX_ENTRIES.

     Each individual ACL entry is of the type acl_entry_t, which is a structure with the
     following members:

     acl_tag_t ae_tag
         The following is a list of definitions of ACL types to be set in ae_tag:

               ACL_UNDEFINED_FIELD  Undefined ACL type.
               ACL_USER_OBJ         Discretionary access rights for processes whose effective
                                    user ID matches the user ID of the file's owner.
               ACL_USER             Discretionary access rights for processes whose effective
                                    user ID matches the ACL entry qualifier.
               ACL_GROUP_OBJ        Discretionary access rights for processes whose effective
                                    group ID or any supplemental groups match the group ID of the
                                    file's owner.
               ACL_GROUP            Discretionary access rights for processes whose effective
                                    group ID or any supplemental groups match the ACL entry
                                    qualifier.
               ACL_MASK             The maximum discretionary access rights that can be granted
                                    to a process in the file group class.  This is only valid for
                                    POSIX.1e ACLs.
               ACL_OTHER            Discretionary access rights for processes not covered by any
                                    other ACL entry.  This is only valid for POSIX.1e ACLs.
               ACL_OTHER_OBJ        Same as ACL_OTHER.
               ACL_EVERYONE         Discretionary access rights for all users.  This is only
                                    valid for NFSv4 ACLs.

         Each POSIX.1e ACL must contain exactly one ACL_USER_OBJ, one ACL_GROUP_OBJ, and one
         ACL_OTHER.  If any of ACL_USER, ACL_GROUP, or ACL_OTHER are present, then exactly one
         ACL_MASK entry should be present.

     uid_t ae_id
         The ID of user for whom this ACL describes access permissions.  For entries other than
         ACL_USER and ACL_GROUP, this field should be set to ACL_UNDEFINED_ID.

     acl_perm_t ae_perm
         This field defines what kind of access the process matching this ACL has for accessing
         the associated file.  For POSIX.1e ACLs, the following are valid:

         ACL_EXECUTE            The process may execute the associated file.

         ACL_WRITE              The process may write to the associated file.

         ACL_READ               The process may read from the associated file.

         ACL_PERM_NONE          The process has no read, write or execute permissions to the
                                associated file.

         For NFSv4 ACLs, the following are valid:

         ACL_READ_DATA          The process may read from the associated file.

         ACL_LIST_DIRECTORY     Same as ACL_READ_DATA.

         ACL_WRITE_DATA         The process may write to the associated file.

         ACL_ADD_FILE           Same as ACL_ACL_WRITE_DATA.

         ACL_APPEND_DATA

         ACL_ADD_SUBDIRECTORY   Same as ACL_APPEND_DATA.

         ACL_READ_NAMED_ATTRS   Ignored.

         ACL_WRITE_NAMED_ATTRS  Ignored.

         ACL_EXECUTE            The process may execute the associated file.

         ACL_DELETE_CHILD

         ACL_READ_ATTRIBUTES

         ACL_WRITE_ATTRIBUTES

         ACL_DELETE

         ACL_READ_ACL

         ACL_WRITE_ACL

         ACL_WRITE_OWNER

         ACL_SYNCHRONIZE        Ignored.

     acl_entry_type_t ae_entry_type
         This field defines the type of NFSv4 ACL entry.  It is not used with POSIX.1e ACLs.  The
         following values are valid:

         ACL_ENTRY_TYPE_ALLOW

         ACL_ENTRY_TYPE_DENY

     acl_flag_t ae_flags
         This field defines the inheritance flags of NFSv4 ACL entry.  It is not used with
         POSIX.1e ACLs.  The following values are valid:

         ACL_ENTRY_FILE_INHERIT

         ACL_ENTRY_DIRECTORY_INHERIT

         ACL_ENTRY_NO_PROPAGATE_INHERIT

         ACL_ENTRY_INHERIT_ONLY

SEE ALSO

     acl(3), vaccess_acl_nfs4(9), vaccess_acl_posix1e(9), VFS(9), vaccess(9), VOP_ACLCHECK(9),
     VOP_GETACL(9), VOP_SETACL(9)

AUTHORS

     This manual page was written by Robert Watson.