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Add an OS X startup item to set the permissions and/or ownership of the

BPF devices, and add a README.macosx file to explain how to install and
use that startup item.
This commit is contained in:
guy 2004-10-18 09:51:02 +00:00
parent 59f566ecfb
commit 4b1ac36c83
5 changed files with 87 additions and 1 deletions

33
ChmodBPF/ChmodBPF Executable file
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@ -0,0 +1,33 @@
#! /bin/sh
. /etc/rc.common
StartService ()
{
#
# Unfortunately, Mac OS X's devfs is based on the old FreeBSD
# one, not the current one, so there's no way to configure it
# to create BPF devices with particular owners or groups.
# This startup item will make it owned by the admin group,
# with permissions rw-rw----, so that anybody in the admin
# group can use programs that capture or send raw packets.
#
# Change this as appropriate for your site, e.g. to make
# it owned by a particular user without changing the permissions,
# so only that user and the super-user can capture or send raw
# packets, or give it the permissions rw-r-----, so that
# only the super-user can send raw packets but anybody in the
# admin group can capture packets.
#
chgrp admin /dev/bpf*
chmod g+rw /dev/bpf*
}
StopService ()
{
return 0;
}
RestartService () { StartService; }
RunService "$1"

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{
Description = "Change BPF permissions";
Provides = ("Non-root permission to capture or send raw packets");
}

3
FILES
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@ -1,4 +1,6 @@
CHANGES
ChmodBPF/ChmodBPF
ChmodBPF/StartupParameters.plist
CREDITS
FILES
INSTALL.txt
@ -9,6 +11,7 @@ README.aix
README.dag
README.hpux
README.linux
README.macosx
README.tru64
README.Win32
SUNOS4/nit_if.o.sparc

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@ -1,4 +1,4 @@
@(#) $Header: /tcpdump/master/libpcap/INSTALL.txt,v 1.10 2004-04-05 22:43:50 guy Exp $ (LBL)
@(#) $Header: /tcpdump/master/libpcap/INSTALL.txt,v 1.11 2004-10-18 09:51:02 guy Exp $ (LBL)
To build libpcap, run "./configure" (a shell script). The configure
script will determine your system attributes and generate an
@ -295,6 +295,8 @@ timestamp resolution if it finds it's running on a SS-1).
FILES
-----
CHANGES - description of differences between releases
ChmodBPF/* - Mac OS X startup item to set ownership and permissions
on /dev/bpf*
CREDITS - people that have helped libpcap along
FILES - list of files exported as part of the distribution
INSTALL.txt - this file
@ -305,6 +307,7 @@ README.aix - notes on using libpcap on AIX
README.dag - notes on using libpcap to capture on Endace DAG devices
README.hpux - notes on using libpcap on HP-UX
README.linux - notes on using libpcap on Linux
README.macosx - notes on using libpcap on Mac OS X
README.tru64 - notes on using libpcap on Digital/Tru64 UNIX
README.Win32 - notes on using libpcap on Win32 systems (with WinPcap)
SUNOS4 - pre-SunOS 4.1 replacement kernel nit modules

43
README.macosx Normal file
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As with other systems using BPF, Mac OS X allows users with read access
to the BPF devices to capture packets with libpcap and allows users with
write access to the BPF devices to send packets with libpcap.
On some systems that use BPF, the BPF devices live on the root file
system, and the permissions and/or ownership on those devices can be
changed to give users other than root permission to read or write those
devices.
On newer versions of FreeBSD, the BPF devices live on devfs, and devfs
can be configured to set the permissions and/or ownership of those
devices to give users other than root permission to read or write those
devices.
On Mac OS X, the BPF devices live on devfs, but the OS X version of
devfs is based on an older (non-default) FreeBSD devfs, and that version
of devfs cannot be configured to set the permissions and/or ownership of
those devices.
Therefore, we supply a "startup item" for OS X that will change the
ownership of the BPF devices so that the "admin" group owns them, and
will change the permission of the BPF devices to rw-rw----, so that all
users in the "admin" group - i.e., all users with "Allow user to
administer this computer" turned on - have both read and write access to
them.
The startup item is in the ChmodBPF directory in the source tree. A
/Library/StartupItems directory should be created if it doesn't already
exist, and the ChmodBPF directory should be copied to the
/Library/StartupItems directory (copy the entire directory, so that
there's a /Library/StartupItems/ChmodBPF directory, containing all the
files in the source tree's ChmodBPF directory; don't copy the individual
items in that directory to /Library/StartupItems).
If you want to give a particular user permission to access the BPF
devices, rather than giving all administrative users permission to
access them, you can have the ChmodBPF/ChmodBPF script change the
ownership of /dev/bpf* without changing the permissions. If you want to
give a particular user permission to read and write the BPF devices and
give the administrative users permission to read but not write the BPF
devices, you can have the script change the owner to that user, the
group to "admin", and the permissions to rw-r-----. Other possibilities
are left as an exercise for the reader.