#!/bin/sh
#
# capture-sample.sh, Copyright © 2011 Matteo Cypriani <mcy@lm7.fr>
#
########################################################################
# This program is licensed under the terms of the Expat license.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
########################################################################
#
# Captures a few packets on a Wi-Fi interface, using Tcpdump, and
# writes them to a Pcap file along with some information about the
# system. A tarball containing all these files is finally created.

#set -x
set -e


## Parameters (tune them if you want) ##

# Number of packet to capture:
NB_PKT=10
# Maximal time of a capture on a given channel:
TIMEOUT=15
# Temporary directory:
TMP=/tmp
# Name of the capture file:
FILE=capture.pcap
# First channel to scan:
CHANNEL=1


## Functions ##

# Displays the message in argument on the error output and exits
error()
{
	printf '%s\n' "$1" >&2
	clean
	exit 1
}

# Deletes the temporary files
clean()
{
	rm -fr "$DESTDIR"
}

# Verifies the presence of the needed programs
check_dependencies()
{
	command -v tcpdump >/dev/null \
		|| error "tcpdump is required to run this program!"

	if [ "$OS" = Linux ] ; then
		[ -x /sbin/iwconfig ] \
			|| error "iwconfig is required to run this program on Linux!"
	fi
}

# Switches the capture interface to monitor mode, on the channel in
# argument
iface_set_channel()
{
	echo "Setting interface $IFACE on channel $1..."
	case "$OS" in
		Linux)
			iface_down
			iwconfig "$IFACE" mode managed
			iface_up
			iwconfig "$IFACE" channel "$1"
			;;
		NetBSD | OpenBSD)
			iface_down
			ifconfig "$IFACE" media autoselect chan "$1"
			iface_up
			;;
		*)
			error "Your OS is not supported."
			;;
	esac \
		|| error "Cannot set the channel!"

	echo "Channel set."
	iface_monitor
}

# Switches the capture interface to monitor mode
iface_monitor()
{
	iface_down

	printf 'Switching interface %s to monitor mode... ' "$IFACE"
	case "$OS" in
		Linux)
			iwconfig "$IFACE" mode monitor
			;;
		NetBSD | OpenBSD)
			ifconfig "$IFACE" media autoselect mediaopt monitor
			;;
		*)
			error "Your OS is not supported."
			;;
	esac \
		|| error "Cannot switch the interface to monitor mode!"

	echo "OK."
	iface_up
}

# Shuts down the capture interface
iface_down()
{
	printf 'Shuting down interface %s... ' "$IFACE"
	ifconfig "$IFACE" down \
		|| error "Cannot shut down the interface!"
	echo "OK."
}

# Turns on the capture interface
iface_up()
{
	printf 'Turning up interface %s... ' "$IFACE"
	ifconfig "$IFACE" up \
		|| error "Cannot turn the interface up!"
	echo "OK."
}

# Invokes tcpdump and displays the number of packets captured
invoke_tcpdump()
{
	NCAP=$(tcpdump -i "$IFACE" -c "$NB_PKT" -w "$FILE" 2>&1 \
		| sed -nr 's/([[:digit:]]+) packets received by filter$/\1/p')
	[ -z "$NCAP" ] \
		&& error "Error parsing the tcpdump messages! (NCAP=\"$NCAP\")"
	echo "$NCAP"
}

# Waits for a number of seconds, then kills any tcpdump process
wait_tcpdump()
{
	sleep "$1"
	echo "$1 seconds passed, killing all tcpdump processes..."
	pkill tcpdump
}

# Gets some information about the running system
gather_system_information()
{
	printf "Gathering system information... "
	# Kernel & other information:
	uname -a >"$DESTDIR"/uname-a
	# Wi-Fi interface information:
	ifconfig "$IFACE" >"$DESTDIR/ifconfig_$IFACE"
	[ "$OS" = Linux ] \
		&& iwconfig "$IFACE" >"$DESTDIR/iwconfig_$IFACE"
	# PCI devices:
	command -v lspci >/dev/null \
		&& lspci >"$DESTDIR"/lspci \
		|| echo "lspci not available! Please install pciutils. "
	# USB devices:
	gather_usb_devices
	# Loaded kernel modules:
	gather_kernel_modules
	echo "OK."
}

# Gets information about the plugged usb devices
gather_usb_devices()
{
	case "$OS" in
		Linux)
			command -v lsusb >/dev/null \
				&& lsusb >"$DESTDIR"/lsusb \
				|| echo "lsusb not available! Please install usbutils. "
			;;
		NetBSD | OpenBSD | DragonFly)
			command -v usbstats >/dev/null \
				&& usbstats >"$DESTDIR"/usbstats \
				|| echo "usbstats not available! Please install usbutil. "
			;;
	esac
}

# Gets information about the loaded kernel modules
gather_kernel_modules()
{
	case "$OS" in
		Linux)
			lsmod >"$DESTDIR"/lsmod
			;;
		NetBSD | OpenBSD)
			modstat >"$DESTDIR"/modstat
			;;
		DragonFly)
			kldstat >"$DESTDIR"/kldstat
			;;
	esac
}

# Compresses the destination directory to a tarball
create_archive()
{
	TARBALL="${DESTDIR}.tar.gz"
	DIR=$(basename "$DESTDIR")
	tar -C "$TMP" -czf "$TARBALL" "$DIR"
	echo "Archive \"$TARBALL\" created."
}


## Main program ##

[ $# -eq 1 ] \
	|| error "Usage: $0 <wifi_interface>"

# Interface to capture from:
IFACE=$1
# Machine information:
OS=$(uname)
OS_RELEASE=$(uname -r)
HOSTNAME=$(uname -n)
# Current date:
DATE=$(date +%FT%H%M%S)
# Temporary destination directory:
DESTDIR=$(mktemp -d \
	"$TMP/capture_${OS}-${OS_RELEASE}_${IFACE}_${HOSTNAME}_${DATE}_XXX")
# Update capture file with full path:
FILE="$DESTDIR/$FILE"

check_dependencies

echo "Trying to capture $NB_PKT packets..."
CAPTURED=0
while [ "$CAPTURED" -eq 0 ] && [ "$CHANNEL" -le 14 ] ; do
	echo
	iface_set_channel "$CHANNEL"
	wait_tcpdump "$TIMEOUT" &
	CAPTURED=$(invoke_tcpdump)
	[ "$CAPTURED" -eq 0 ] \
		&& echo "No packet captured on channel $CHANNEL." \
		|| echo "$CAPTURED packets captured on channel $CHANNEL."
	CHANNEL=$((CHANNEL + 1))
done

echo
[ "$CAPTURED" -gt 0 ] \
	|| error "Failed to capture any packet!"
echo "Capture file \"$FILE\" created."

gather_system_information
create_archive
clean

printf '\nYou can now shut down the interface %s if you would like:\n' "$IFACE"
printf '\tifconfig %s down\n' "$IFACE"