check-sni.sh

gistfile1.txt

#!/bin/bash

# This script uses curl / tshark to check if a server accepts
# and responds with SNI (server_name) in server hello
# exits 1 if not SNI, exits 0 if SNI

set -eu
hostname=$1

# Tempfile for formatted output
tmpfile="$(mktemp)"

tshark -V -f "(host $hostname and port 443)" \
  -Y "ssl.handshake.type == 2" 2>/dev/null 1>"$tmpfile" &
pid=$!

# Wait for tshark setup
sleep 1

# Send a request to get a server hello
curl --silent "https://${hostname}" 2> /dev/null 1>&2

# Make sure tshark has time to read it
sleep 1

# Check if server_name is set
res=$(grep server_name "$tmpfile")

# Kill our tshark
kill "$pid"
# Remove our temp file
rm "$tmpfile"
if [ "$res" ] ; then
  echo "$hostname"
  exit 0
fi
exit 1