9761e3fdaf
Submitted by: amdmi3 PR: 165431 MFC after: 1 week
103 lines
3.6 KiB
Groff
103 lines
3.6 KiB
Groff
.\"
|
|
.\" Copyright (c) 2008-2009 Robert N. M. Watson
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" This software was developed at the University of Cambridge Computer
|
|
.\" Laboratory with support from a grant from Google, Inc.
|
|
.\"
|
|
.\" 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 February 25, 2012
|
|
.Dt CAP_ENTER 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm cap_enter ,
|
|
.Nm cap_getmode
|
|
.Nd Capability mode system calls
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/capability.h
|
|
.Ft int
|
|
.Fn cap_enter "void"
|
|
.Ft int
|
|
.Fn cap_getmode "u_int *modep"
|
|
.Sh DESCRIPTION
|
|
.Fn cap_enter
|
|
places the current process into capability mode, a mode of execution in which
|
|
processes may only issue system calls operating on file descriptors or
|
|
reading limited global system state.
|
|
Access to global name spaces, such as file system or IPC name spaces, is
|
|
prevented.
|
|
If the process is already in a capability mode sandbox, the system call is a
|
|
no-op.
|
|
Future process descendants create with
|
|
.Xr fork 2
|
|
or
|
|
.Xr pdfork 2
|
|
will be placed in capability mode from inception.
|
|
.Pp
|
|
When combined with capabilities created with
|
|
.Xr cap_new 2 ,
|
|
.Fn cap_enter
|
|
may be used to create kernel-enforced sandboxes in which
|
|
appropriately-crafted applications or application components may be run.
|
|
.Pp
|
|
.Fn cap_getmode
|
|
returns a flag indicating whether or not the process is in a capability mode
|
|
sandbox.
|
|
.Sh CAVEAT
|
|
Creating effective process sandboxes is a tricky process that involves
|
|
identifying the least possible rights required by the process and then
|
|
passing those rights into the process in a safe manner.
|
|
See the CAVEAT
|
|
section of
|
|
.Xr cap_new 2
|
|
for why this is particularly tricky with UNIX file descriptors as the
|
|
canonical representation of a right.
|
|
Consumers of
|
|
.Fn cap_enter
|
|
should also be aware of other inherited rights, such as access to VM
|
|
resources, memory contents, and other process properties that should be
|
|
considered.
|
|
It is advisable to use
|
|
.Xr fexecve 2
|
|
to create a runtime environment inside the sandbox that has as few implicitly
|
|
acquired rights as possible.
|
|
.Sh RETURN VALUES
|
|
.Rv -std cap_enter cap_getmode
|
|
.Sh SEE ALSO
|
|
.Xr cap_new 2 ,
|
|
.Xr fexecve 2 ,
|
|
.Xr capsicum 4
|
|
.Sh HISTORY
|
|
Support for capabilities and capabilities mode was developed as part of the
|
|
.Tn TrustedBSD
|
|
Project.
|
|
.Sh AUTHORS
|
|
These functions and the capability facility were created by
|
|
.An "Robert N. M. Watson"
|
|
at the University of Cambridge Computer Laboratory with support from a grant
|
|
from Google, Inc.
|