1.\"- 2.\" Copyright (c) 2006 nCircle Network Security, Inc. 3.\" All rights reserved. 4.\" 5.\" This software was developed by Robert N. M. Watson for the TrustedBSD 6.\" Project under contract to nCircle Network Security, Inc. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR, NCIRCLE NETWORK SECURITY, 21.\" INC., OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED 23.\" TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 24.\" PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 25.\" LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 26.\" NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 27.\" SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28.\" 29.Dd December 19, 2018 30.Dt PRIV 9 31.Os 32.Sh NAME 33.Nm priv 34.Nd kernel privilege checking API 35.Sh SYNOPSIS 36.In sys/priv.h 37.Ft int 38.Fn priv_check "struct thread *td" "int priv" 39.Ft int 40.Fn priv_check_cred "struct ucred *cred" "int priv" 41.Sh DESCRIPTION 42The 43.Nm 44interfaces check to see if specific system privileges are granted to the 45passed thread, 46.Fa td , 47or credential, 48.Fa cred . 49This interface replaces the now removed 50.Xr suser 9 51privilege checking interface. 52Privileges typically represent rights in one of two categories: the right to 53manage a particular component of the system, or an exemption to a specific 54policy or access control list. 55The caller identifies the desired privilege via the 56.Fa priv 57argument. 58.Ss Privilege Policies 59Privileges are typically granted based on one of two base system policies: 60the superuser policy, which grants privilege based on the effective (or 61sometimes real) UID having a value of 0, and the 62.Xr jail 2 63policy, which permits only certain privileges to be granted to processes in a 64jail. 65The set of available privileges may also be influenced by the TrustedBSD MAC 66Framework, described in 67.Xr mac 9 . 68.Sh IMPLEMENTATION NOTES 69When adding a new privilege check to a code path, first check the complete 70list of current privileges in 71.Pa sys/priv.h 72to see if one already exists for the class of privilege required. 73Only if there is not an exact match should a new privilege be added to the 74privilege list. 75As privilege numbers becomes encoded in the kernel module ABI, privilege 76constants must not be changed as any kernel modules depending on privileges 77will then need to be recompiled. 78When adding a new privilege, be certain to also determine whether it should 79be listed in 80.Fn prison_priv_check , 81which includes a complete list of privileges granted to the root user in 82.Xr jail 2 . 83.Pp 84Certain catch-all privileges exist, such as 85.Dv PRIV_DRIVER , 86intended to be used by device drivers, rather than adding a new 87driver-specific privilege. 88.Sh RETURN VALUES 89Typically, 0 will be returned for success, and 90.Er EPERM 91will be returned on failure. 92Most consumers of 93.Nm 94will wish to directly return the error code from a failed privilege check to 95user space; a small number will wish to translate it to another error code 96appropriate to a specific context. 97.Pp 98When designing new APIs, it is preferable to return explicit errors from a 99call if privilege is not granted rather than changing the semantics of the 100call but returning success. 101For example, the behavior exhibited by 102.Xr stat 2 , 103in which the generation field is optionally zero'd out when there is 104insufficient privilege is highly undesirable, as it results in frequent 105privilege checks, and the caller is unable to tell if an access control 106failure occurred. 107.Sh SEE ALSO 108.Xr jail 2 , 109.Xr mac 9 , 110.Xr ucred 9 111.Sh AUTHORS 112The 113.Nm 114API and implementation were created by 115.An Robert Watson 116under contract to 117nCircle Network Security, Inc. 118