Raspberry Pi: Sniffen mit TShark, aber nicht als root User – Wenzlaff.de

Zuerst mal eine Mindmap zu TShark, dem Kommandline-Tool von Wireshark (frühe Ethereal).

Installation

Zuerste den rPi aktualisieren und das Packet installieren mit:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install tshark

sudo apt-get update

sudo apt-get upgrade

sudo apt-get install tshark

Zuerst einmal die Befehle und die Version für die Komandozeile mit

tshark -h

tshark -h

ausgeben:

TShark 1.12.1 (Git Rev Unknown from unknown)
Dump and analyze network traffic.
See http://www.wireshark.org for more information.

Copyright 1998-2014 Gerald Combs <gerald@wireshark.org> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Usage: tshark [options] ...

Capture interface:
  -i <interface>           name or idx of interface (def: first non-loopback)
  -f <capture filter>      packet filter in libpcap filter syntax
  -s <snaplen>             packet snapshot length (def: 65535)
  -p                       don't capture in promiscuous mode
  -I                       capture in monitor mode, if available
  -B <buffer size>         size of kernel buffer (def: 2MB)
  -y <link type>           link layer type (def: first appropriate)
  -D                       print list of interfaces and exit
  -L                       print list of link-layer types of iface and exit

Capture stop conditions:
  -c <packet count>        stop after n packets (def: infinite)
  -a <autostop cond.> ...  duration:NUM - stop after NUM seconds
                           filesize:NUM - stop this file after NUM KB
                              files:NUM - stop after NUM files
Capture output:
  -b <ringbuffer opt.> ... duration:NUM - switch to next file after NUM secs
                           filesize:NUM - switch to next file after NUM KB
                              files:NUM - ringbuffer: replace after NUM files
Input file:
  -r <infile>              set the filename to read from (- to read from stdin)

Processing:
  -2                       perform a two-pass analysis
  -R <read filter>         packet Read filter in Wireshark display filter syntax
  -Y <display filter>      packet displaY filter in Wireshark display filter
                           syntax
  -n                       disable all name resolutions (def: all enabled)
  -N <name resolve flags>  enable specific name resolution(s): "mntC"
  -d <layer_type>==<selector>,<decode_as_protocol> ...
                           "Decode As", see the man page for details
                           Example: tcp.port==8888,http
  -H <hosts file>          read a list of entries from a hosts file, which will
                           then be written to a capture file. (Implies -W n)
Output:
  -w <outfile|->           write packets to a pcap-format file named "outfile"
                           (or to the standard output for "-")
  -C <config profile>      start with specified configuration profile
  -F <output file type>    set the output file type, default is pcapng
                           an empty "-F" option will list the file types
  -V                       add output of packet tree        (Packet Details)
  -O <protocols>           Only show packet details of these protocols, comma
                           separated
  -P                       print packet summary even when writing to a file
  -S <separator>           the line separator to print between packets
  -x                       add output of hex and ASCII dump (Packet Bytes)
  -T pdml|ps|psml|text|fields
                           format of text output (def: text)
  -e <field>               field to print if -Tfields selected (e.g. tcp.port,
                           _ws.col.Info)
                           this option can be repeated to print multiple fields
  -E<fieldsoption>=<value> set options for output when -Tfields selected:
     header=y|n            switch headers on and off
     separator=/t|/s|<char> select tab, space, printable character as separator
     occurrence=f|l|a      print first, last or all occurrences of each field
     aggregator=,|/s|<char> select comma, space, printable character as
                           aggregator
     quote=d|s|n           select double, single, no quotes for values
  -t a|ad|d|dd|e|r|u|ud    output format of time stamps (def: r: rel. to first)
  -u s|hms                 output format of seconds (def: s: seconds)
  -l                       flush standard output after each packet
  -q                       be more quiet on stdout (e.g. when using statistics)
  -Q                       only log true errors to stderr (quieter than -q)
  -g                       enable group read access on the output file(s)
  -W n                     Save extra information in the file, if supported.
                           n = write network address resolution information
  -X <key>:<value>         eXtension options, see the man page for details
  -z <statistics>          various statistics, see the man page for details
  --capture-comment <comment>
                           add a capture comment to the newly created
                           output file (only for pcapng)

Miscellaneous:
  -h                       display this help and exit
  -v                       display version info and exit
  -o <name>:<value> ...    override preference setting
  -K <keytab>              keytab file to use for kerberos decryption
  -G [report]              dump one of several available reports and exit
                           default report="fields"
                           use "-G ?" for more help

WARNING: dumpcap will enable kernel BPF JIT compiler if available.
You might want to reset it
By doing "echo 0 > /proc/sys/net/core/bpf_jit_enable"

TShark 1.12.1 (Git Rev Unknown from unknown)

Dump and analyze network traffic.

See http://www.wireshark.org for more information.

This is free software; see the source for copying conditions. There is NO

warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Usage: tshark [options] ...

Capture interface:

-i <interface> name or idx of interface (def: first non-loopback)

-f <capture filter> packet filter in libpcap filter syntax

-s <snaplen> packet snapshot length (def: 65535)

-p don't capture in promiscuous mode

-I capture in monitor mode, if available

-B <buffer size> size of kernel buffer (def: 2MB)

-y <link type> link layer type (def: first appropriate)

-D print list of interfaces and exit

-L print list of link-layer types of iface and exit

Capture stop conditions:

-c <packet count> stop after n packets (def: infinite)

-a <autostop cond.> ... duration:NUM - stop after NUM seconds

filesize:NUM - stop this file after NUM KB

files:NUM - stop after NUM files

Capture output:

-b <ringbuffer opt.> ... duration:NUM - switch to next file after NUM secs

filesize:NUM - switch to next file after NUM KB

files:NUM - ringbuffer: replace after NUM files

Input file:

-r <infile> set the filename to read from (- to read from stdin)

Processing:

-2 perform a two-pass analysis

-R <read filter> packet Read filter in Wireshark display filter syntax

-Y <display filter> packet displaY filter in Wireshark display filter

syntax

-n disable all name resolutions (def: all enabled)

-N <name resolve flags> enable specific name resolution(s): "mntC"

-d <layer_type>==<selector>,<decode_as_protocol> ...

"Decode As", see the man page for details

Example: tcp.port==8888,http

-H <hosts file> read a list of entries from a hosts file, which will

then be written to a capture file. (Implies -W n)

Output:

-w <outfile|-> write packets to a pcap-format file named "outfile"

(or to the standard output for "-")

-C <config profile> start with specified configuration profile

-F <output file type> set the output file type, default is pcapng

an empty "-F" option will list the file types

-V add output of packet tree (Packet Details)

-O <protocols> Only show packet details of these protocols, comma

separated

-P print packet summary even when writing to a file

-S <separator> the line separator to print between packets

-x add output of hex and ASCII dump (Packet Bytes)

-T pdml|ps|psml|text|fields

format of text output (def: text)

-e <field> field to print if -Tfields selected (e.g. tcp.port,

_ws.col.Info)

this option can be repeated to print multiple fields

-E<fieldsoption>=<value> set options for output when -Tfields selected:

header=y|n switch headers on and off

separator=/t|/s|<char> select tab, space, printable character as separator

occurrence=f|l|a print first, last or all occurrences of each field

aggregator=,|/s|<char> select comma, space, printable character as

aggregator

quote=d|s|n select double, single, no quotes for values

-t a|ad|d|dd|e|r|u|ud output format of time stamps (def: r: rel. to first)

-u s|hms output format of seconds (def: s: seconds)

-l flush standard output after each packet

-q be more quiet on stdout (e.g. when using statistics)

-Q only log true errors to stderr (quieter than -q)

-g enable group read access on the output file(s)

-W n Save extra information in the file, if supported.

n = write network address resolution information

-X <key>:<value> eXtension options, see the man page for details

-z <statistics> various statistics, see the man page for details

--capture-comment <comment>

add a capture comment to the newly created

output file (only for pcapng)

Miscellaneous:

-h display this help and exit

-v display version info and exit

-o <name>:<value> ... override preference setting

-K <keytab> keytab file to use for kerberos decryption

-G [report] dump one of several available reports and exit

default report="fields"

use "-G ?" for more help

WARNING: dumpcap will enable kernel BPF JIT compiler if available.

You might want to reset it

By doing "echo 0 > /proc/sys/net/core/bpf_jit_enable"

Erst wollen wir uns die vorhandenen Interfaces anschauen und die Nummer merken.

sudo tshark -D

1	sudo tshark -D

Liefert die folgende Liste der verfügbaren Interfaces:
1. eth0 2. wlan0 3. wlan0mon 4. any 5. lo (Loopback) 6. nflog 7. nfqueue 8. usbmon1
Dann mal 10 Sekunden in die Datei traffic.pcap den Netzwerkverkehr von 1 (eth0) sichern mit:

tshark -i 1 -a duration:10 -w traffic.pcap

1	tshark -i 1 -a duration:10 -w traffic.pcap

Kommt es zu dieser Fehlermeldung:

Capturing on 'eth0'
tshark: The capture session could not be initiated on interface 'eth0' (You don't have permission to capture on that device).
Please check to make sure you have sufficient permissions, and that you have the proper interface or pipe specified.

Capturing on 'eth0'

tshark: The capture session could not be initiated on interface 'eth0' (You don't have permission to capture on that device).

Please check to make sure you have sufficient permissions, and that you have the proper interface or pipe specified.

dann nicht aus Sicherheitsgründen mit sudo starten. TShark sollte nicht als root ausgeführt werden und der aktuelle User hat nicht die Rechte auf die Schnittstellen zuzugreifen.

Abhilfe

Den aktuellen User (hier pi) für den Zugriff reconfigurieren mit:

sudo dpkg-reconfigure wireshark-common

1	sudo dpkg-reconfigure wireshark-common

Es erscheint so ein Dialog:

Dort mit Ja antworten.

Damit die Berechigung für den User (pi) gesetzt wird, und es nicht zu dieser Fehlermeldung kommt:

tshark: Couldn't run /usr/bin/dumpcap in child process: Keine Berechtigung

1	tshark: Couldn't run /usr/bin/dumpcap in child process: Keine Berechtigung

Einmal:

sudo usermod -a -G wireshark pi

1	sudo usermod -a -G wireshark pi

Dann einmal abmelden:

exit

exit

und wieder anmelden.

Schon können Dateien im PCAP Format auf dem Raspberry Pi erzeugt werden und auf einem anderen Rechner mit Wireshark ausgewertet werden.