bd1da0a002
Change the nvlist_recv() function to take additional argument that specifies flags expected on the received nvlist. Receiving a nvlist with different set of flags than the ones we expect might lead to undefined behaviour, which might be potentially dangerous. Update consumers of this and related functions and update the tests. Approved by: pjd (mentor) Update man page for nvlist_unpack, nvlist_recv, nvlist_xfer, cap_recv_nvlist and cap_xfer_nvlist. Reviewed by: AllanJude Approved by: pjd (mentor)
301 lines
7.7 KiB
Groff
301 lines
7.7 KiB
Groff
.\" Copyright (c) 2013 The FreeBSD Foundation
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.\" All rights reserved.
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.\"
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.\" This documentation was written by Pawel Jakub Dawidek under sponsorship
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.\" from the FreeBSD Foundation.
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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 May 2, 2015
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.Dt LIBCAPSICUM 3
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.Os
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.Sh NAME
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.Nm cap_init ,
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.Nm cap_wrap ,
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.Nm cap_unwrap ,
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.Nm cap_sock ,
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.Nm cap_clone ,
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.Nm cap_close ,
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.Nm cap_limit_get ,
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.Nm cap_limit_set ,
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.Nm cap_send_nvlist ,
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.Nm cap_recv_nvlist ,
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.Nm cap_xfer_nvlist ,
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.Nm cap_service_open
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.Nd "library for handling application capabilities"
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.Sh LIBRARY
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.Lb libcapsicum
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.Sh SYNOPSIS
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.In libcapsicum.h
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.In nv.h
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.Ft "cap_channel_t *"
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.Fn cap_init "void"
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.Ft "cap_channel_t *"
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.Fn cap_wrap "int sock"
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.Ft "int"
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.Fn cap_unwrap "cap_channel_t *chan"
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.Ft "int"
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.Fn cap_sock "const cap_channel_t *chan"
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.Ft "cap_channel_t *"
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.Fn cap_clone "const cap_channel_t *chan"
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.Ft "void"
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.Fn cap_close "cap_channel_t *chan"
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.Ft "int"
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.Fn cap_limit_get "const cap_channel_t *chan" "nvlist_t **limitsp"
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.Ft "int"
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.Fn cap_limit_set "const cap_channel_t *chan" "nvlist_t *limits"
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.Ft "int"
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.Fn cap_send_nvlist "const cap_channel_t *chan" "const nvlist_t *nvl"
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.Ft "nvlist_t *"
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.Fn cap_recv_nvlist "const cap_channel_t *chan" "int flags"
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.Ft "nvlist_t *"
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.Fn cap_xfer_nvlist "const cap_channel_t *chan" "nvlist_t *nvl" "int flags"
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.In libcapsicum_service.h
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.Ft "cap_channel_t *"
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.Fn cap_service_open "const cap_channel_t *chan" "const char *name"
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.Sh DESCRIPTION
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The
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.Nm libcapsicum
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library allows to manage application capabilities through the
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.Xr casperd 8
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daemon.
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.Pp
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The application capability (represented by the
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.Vt cap_channel_t
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type) is a communication channel between the caller and the
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.Xr casperd 8
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daemon or an instance of one of its services.
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A capability to the
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.Xr casperd 8
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daemon obtained with the
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.Fn cap_init
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function allows to create capabilities to casper's services via the
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.Fn cap_service_open
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function.
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.Pp
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The
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.Fn cap_init
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function opens capability to the
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.Xr casperd 8
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daemon.
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.Pp
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The
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.Fn cap_wrap
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function creates
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.Vt cap_channel_t
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based on the given socket.
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The function is used when capability is inherited through
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.Xr execve 2
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or send over
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.Xr unix 4
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domain socket as a regular file descriptor and has to be represented as
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.Vt cap_channel_t
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again.
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.Pp
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The
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.Fn cap_unwrap
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function is the opposite of the
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.Fn cap_wrap
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function.
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It frees the
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.Vt cap_channel_t
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structure and returns
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.Xr unix 4
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domain socket associated with it.
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.Pp
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The
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.Fn cap_clone
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function clones the given capability.
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.Pp
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The
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.Fn cap_close
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function closes the given capability.
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.Pp
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The
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.Fn cap_sock
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function returns
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.Xr unix 4
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domain socket descriptor associated with the given capability for use with
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system calls like
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.Xr kevent 2 ,
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.Xr poll 2
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and
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.Xr select 2 .
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.Pp
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The
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.Fn cap_limit_get
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function stores current limits of the given capability in the
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.Fa limitsp
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argument.
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If the function return
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.Va 0
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and
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.Dv NULL
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is stored in
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.Fa limitsp
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it means there are no limits set.
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.Pp
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The
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.Fn cap_limit_set
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function sets limits for the given capability.
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The limits are provided as nvlist.
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The exact format depends on the service the capability represents.
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.Pp
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The
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.Fn cap_send_nvlist
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function sends the given nvlist over the given capability.
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This is low level interface to communicate with casper services.
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Most services should provide higher level API.
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.Pp
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The
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.Fn cap_recv_nvlist
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function receives the given nvlist over the given capability.
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The
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.Fa flags
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argument defines what type the top nvlist is expected to be.
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If the nvlist flags do not match the flags passed to
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.Fn cap_recv_nvlist ,
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the nvlist will not be returned.
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.Pp
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The
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.Fn cap_xfer_nvlist
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function sends the given nvlist, destroys it and receives new nvlist in
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response over the given capability.
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The
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.Fa flags
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argument defines what type the top nvlist is expected to be.
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If the nvlist flags do not match the flags passed to
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.Fn cap_xfer_nvlist ,
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the nvlist will not be returned.
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It does not matter if the function succeeds or fails, the nvlist given
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for sending will always be destroyed once the function returns.
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.Pp
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The
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.Fn cap_service_open
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function opens casper service of the given name through casper capability
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obtained via the
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.Fn cap_init
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function.
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The function returns capability that provides access to opened service.
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.Sh RETURN VALUES
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The
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.Fn cap_clone ,
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.Fn cap_init ,
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.Fn cap_recv_nvlist ,
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.Fn cap_service_open ,
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.Fn cap_wrap
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and
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.Fn cap_xfer_nvlist
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functions return
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.Dv NULL
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and set the
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.Va errno
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variable on failure.
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.Pp
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The
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.Fn cap_limit_get ,
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.Fn cap_limit_set
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and
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.Fn cap_send_nvlist
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functions return
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.Dv -1
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and set the
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.Va errno
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variable on failure.
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.Pp
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The
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.Fn cap_close ,
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.Fn cap_sock
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and
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.Fn cap_unwrap
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functions always succeed.
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.Sh EXAMPLES
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The following example first opens capability to the
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.Xr casperd 8
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daemon, then using this capability creates new capability to the
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.Nm system.dns
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casper service and uses the latter capability to resolve IP address.
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.Bd -literal
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cap_channel_t *capcas, *capdns;
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nvlist_t *limits;
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const char *ipstr = "127.0.0.1";
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struct in_addr ip;
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struct hostent *hp;
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/* Open capability to the Casper daemon. */
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capcas = cap_init();
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if (capcas == NULL)
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err(1, "Unable to contact Casper daemon");
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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.dns service. */
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capdns = cap_service_open(capcas, "system.dns");
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if (capdns == NULL)
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err(1, "Unable to open system.dns 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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/* Limit system.dns to reverse DNS lookups and IPv4 addresses. */
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limits = nvlist_create(0);
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nvlist_add_string(limits, "type", "ADDR");
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nvlist_add_number(limits, "family", (uint64_t)AF_INET);
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if (cap_limit_set(capdns, limits) < 0)
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err(1, "Unable to limit access to the system.dns service");
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/* Convert IP address in C-string to in_addr. */
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if (!inet_aton(ipstr, &ip))
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errx(1, "Unable to parse IP address %s.", ipstr);
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/* Find hostname for the given IP address. */
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hp = cap_gethostbyaddr(capdns, (const void *)&ip, sizeof(ip), AF_INET);
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if (hp == NULL)
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errx(1, "No name associated with %s.", ipstr);
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printf("Name associated with %s is %s.\\n", ipstr, hp->h_name);
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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 execve 2 ,
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.Xr kevent 2 ,
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.Xr poll 2 ,
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.Xr select 2 ,
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.Xr cap_gethostbyaddr 3 ,
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.Xr err 3 ,
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.Xr gethostbyaddr 3 ,
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.Xr inet_aton 3 ,
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.Xr nv 3 ,
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.Xr capsicum 4 ,
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.Xr unix 4 ,
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.Xr casperd 8
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.Sh AUTHORS
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The
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.Nm libcapsicum
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library 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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