Document the sysctl Casper service.
PR: 226102 Reviewed by: bcr@ Differential Revision: https://reviews.freebsd.org/D14606
This commit is contained in:
Mariusz Zaborski
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54442b3cfa
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edd09a2599
@ -24,4 +24,9 @@ CFLAGS+=-I${.CURDIR}
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HAS_TESTS=
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SUBDIR.${MK_TESTS}+= tests
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MAN+= cap_sysctl
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MLINKS+=cap_sysctl.3 libcap_sysctl.3
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MLINKS+=cap_sysctl.3 cap_sysctlbyname.3
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.include <bsd.lib.mk>
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143
lib/libcasper/services/cap_sysctl/cap_sysctl.3
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143
lib/libcasper/services/cap_sysctl/cap_sysctl.3
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@ -0,0 +1,143 @@
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.\" Copyright (c) 2018 Mariusz Zaborski <oshogbo@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd March 18, 2018
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.Dt CAP_SYSCTL 3
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.Os
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.Sh NAME
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.Nm cap_sysctlbyname
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.Nd "library for getting or setting system information in capability mode"
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.Sh LIBRARY
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.Lb libcap_sysctl
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.Sh SYNOPSIS
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.In sys/nv.h
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.In libcasper.h
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.In casper/cap_sysctl.h
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.Ft int
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.Fn cap_sysctlbyname "cap_channel_t *chan" " const char *name" " void *oldp" " size_t *oldlenp" " const void *newp" " size_t newlen"
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.Sh DESCRIPTION
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The function
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.Fn cap_sysctlbyname
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is equivalent to
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.Xr sysctlbyname 3
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except that the connection to the
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.Nm system.sysctl
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service needs to be provided.
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.Sh LIMITS
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The service can be limited using
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.Xr cap_limit_set 3
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function.
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The
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.Xr nvlist 9
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for that function can contain the following values and types:
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.Bl -ohang -offset indent
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.It ( NV_TYPE_NUMBER )
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The name of the element with type number will be treated as the limited sysctl.
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The value of the element will describe the access rights for given sysctl.
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There are four different rights
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.Dv CAP_SYSCTL_READ ,
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.Dv CAP_SYSCTL_WRITE ,
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.Dv CAP_SYSCTL_RDWR ,
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and
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.Dv CAP_SYSCTL_RECURSIVE .
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The
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.Dv CAP_SYSCTL_READ
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flag allows to fetch the value of a given sysctl.
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The
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.Dv CAP_SYSCTL_WIRTE
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flag allows to override the value of a given sysctl.
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The
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.Dv CAP_SYSCTL_RDWR
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is combination of the
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.Dv CAP_SYSCTL_WIRTE
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and
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.Dv CAP_SYSCTL_READ
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and allows to read and write the value of a given sysctl.
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The
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.Dv CAP_SYSCTL_RECURSIVE
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allows access to all children of a given sysctl.
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This right must be combined with at least one other right.
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.Sh EXAMPLES
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The following example first opens a capability to casper and then uses this
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capability to create the
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.Nm system.sysctl
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casper service and uses it to get the value of
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.Dv kern.trap_enotcap .
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.Bd -literal
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cap_channel_t *capcas, *capsysctl;
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const char *name = "kern.trap_enotcap";
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nvlist_t *limits;
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int value;
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size_t size;
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/* Open capability to Casper. */
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capcas = cap_init();
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if (capcas == NULL)
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err(1, "Unable to contact Casper");
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/* Enter capability mode sandbox. */
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if (cap_enter() < 0 && errno != ENOSYS)
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err(1, "Unable to enter capability mode");
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/* Use Casper capability to create capability to the system.sysctl service. */
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capsysctl = cap_service_open(capcas, "system.sysctl");
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if (capsysctl == NULL)
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err(1, "Unable to open system.sysctl service");
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/* Close Casper capability, we don't need it anymore. */
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cap_close(capcas);
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/* Create limit for one MIB with read access only. */
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limits = nvlist_create(0);
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nvlist_add_number(limits, name, CAP_SYSCTL_READ);
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/* Limit system.sysctl. */
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if (cap_limit_set(capsysctl, limits) < 0)
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err(1, "Unable to set limits");
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/* Fetch value. */
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if (cap_sysctlbyname(capsysctl, name, &value, &size, NULL, 0) < 0)
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err(1, "Unable to get value of sysctl");
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printf("The value of %s is %d.\\n", name, value);
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cap_close(capsysctl);
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.Ed
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.Sh SEE ALSO
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.Xr cap_enter 2 ,
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.Xr err 3 ,
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.Xr sysctlbyname 3,
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.Xr capsicum 4 ,
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.Xr nv 9
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.Sh AUTHORS
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The
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.Nm cap_sysctl
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service was implemented by
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.An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net
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under sponsorship from the FreeBSD Foundation.
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.Pp
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This manual page was written by
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.An Mariusz Zaborski Aq Mt oshogbo@FreeBSD.org .
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