.\"
.\" Copyright (c) 2012 The FreeBSD Foundation
.\" All rights reserved.
.\"
.\" This documentation was written by Pawel Jakub Dawidek under sponsorship
.\" the FreeBSD Foundation.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd May 5, 2020
.Dt CAP_IOCTLS_LIMIT 2
.Os
.Sh NAME
.Nm cap_ioctls_limit ,
.Nm cap_ioctls_get
.Nd manage allowed ioctl commands
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/capsicum.h
.Ft int
.Fn cap_ioctls_limit "int fd" "const unsigned long *cmds" "size_t ncmds"
.Ft ssize_t
.Fn cap_ioctls_get "int fd" "unsigned long *cmds" "size_t maxcmds"
.Sh DESCRIPTION
If a file descriptor is granted the
.Dv CAP_IOCTL
capability right, the list of allowed
.Xr ioctl 2
commands can be selectively reduced (but never expanded) with the
.Fn cap_ioctls_limit
system call.
The
.Fa cmds
argument is an array of
.Xr ioctl 2
commands and the
.Fa ncmds
argument specifies the number of elements in the array.
There can be up to
.Va 256
elements in the array.
Including an element that has been previously revoked will generate an error.
After a successful call only those listed in the array may be used.
.Pp
The list of allowed ioctl commands for a given file descriptor can be obtained
with the
.Fn cap_ioctls_get
system call.
The
.Fa cmds
argument points at memory that can hold up to
.Fa maxcmds
values.
The function populates the provided buffer with up to
.Fa maxcmds
elements, but always returns the total number of ioctl commands allowed for the
given file descriptor.
The total number of ioctls commands for the given file descriptor can be
obtained by passing
.Dv NULL as the
.Fa cmds
argument and
.Va 0
as the
.Fa maxcmds
argument.
If all ioctl commands are allowed
.Dv ( CAP_IOCTL
capability right is assigned to the file descriptor and the
.Fn cap_ioctls_limit
system call was never called for this file descriptor), the
.Fn cap_ioctls_get
system call will return
.Dv CAP_IOCTLS_ALL
and will not modify the buffer pointed to by the
.Fa cmds
argument.
.Sh RETURN VALUES
.Rv -std cap_ioctls_limit
.Pp
The
.Fn cap_ioctls_get
function, if successful, returns the total number of allowed ioctl commands or
the value
.Dv CAP_IOCTLS_ALL
if all ioctls commands are allowed.
On failure the value
.Va -1
is returned and the global variable errno is set to indicate the error.
.Sh ERRORS
.Fn cap_ioctls_limit
succeeds unless:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid descriptor.
.It Bq Er EFAULT
The
.Fa cmds
argument points at an invalid address.
.It Bq Er EINVAL
The
.Fa ncmds
argument is greater than
.Va 256 .
.It Bq Er ENOTCAPABLE
.Fa cmds
would expand the list of allowed
.Xr ioctl 2
commands.
.El
.Pp
.Fn cap_ioctls_get
succeeds unless:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid descriptor.
.It Bq Er EFAULT
The
.Fa cmds
argument points at invalid address.
.El
.Sh SEE ALSO
.Xr cap_fcntls_limit 2 ,
.Xr cap_rights_limit 2 ,
.Xr ioctl 2
.Sh HISTORY
The
.Fn cap_ioctls_get
and
.Fn cap_ioctls_limit
system calls first appeared in
.Fx 8.3 .
Support for capabilities and capabilities mode was developed as part of the
.Tn TrustedBSD
Project.
.Sh AUTHORS
This function was created by
.An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net
under sponsorship of the FreeBSD Foundation.