Tshark Scripts

Collect SNIs without using up a lot of memory

get-snis-via-tshark.sh

#!/bin/bash
set -eu
sleep=5
duration=90
interface=internal
pmatch=tshark
snimatch=example.com
sleep_secs=5
get_sni() {

  ts=$(date +"%Y-%m-%dT%T.%3N%z")
  # echo "I: Running tshark instance to get sni info. ${ts}"
  # sleep 1
  # tshark -l -i $interface -a duration:$duration -f 'dst port ( 443 )' -Y 'ssl.handshake.extension.type == "server_name" || http.host' -T fields -e ip.src -e ip.dst -e tcp.dstport -e http.host -e ssl.handshake.extensions_server_name 2>&1 >> sni.log  &
  tshark -l -i $interface -a duration:$duration -f 'dst port ( 443 )' -Y 'ssl.handshake.extension.type == "server_name" || http.host' -T fields -e ip.src -e ip.dst -e tcp.dstport -e http.host -e ssl.handshake.extensions_server_name | grep $snimatch 2>&1 >> sni.log  &
}

test_interface_exists() {
  if ! tshark -D | grep $interface; then
    echo E: Interface $interface does not exist!
    exit 1
  fi
}

is_tshark_running() {
  echo foo
}

main() {
  test_interface_exists
  start_ts=$(date +"%Y-%m-%dT%T.%3N%z")
  echo "I: Starting tshark looper for interfarce: $interface and SNImatch: $snimatch at $start_ts"
  while true; do
    if ! pgrep -x "$pmatch" > /dev/null; then
      get_sni
    else
      # echo "$pmatch command is already running."
      true
    fi
    sleep $sleep_secs
  done
}

main

nohup get-snis.sh &

Watch memory usage of tshark command

top | grep tshark

ps | grep snis
kill id
pkill tshark