chat/crauth.sh

#!/bin/sh

members_file=$1

[ "$members_file" = "" ] && echo "members file not specified" && exit 1

# read member from client
read member

# lookup user
secret=$(cat $members_file | grep $member | sed 's/;/\n/g' | sed -n 2p)

# when user does not exists, exit with message
if [ "$secret" = "" ]; then
	echo "user does not exist"
	exit 1
fi

# compute random challenge
challenge=$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 3 | head -n 1)

# communicate challenge to client
echo $challenge

# read his response
read response

# check whether response is what should be expected
if [ "$response" != "$(echo $secret$challenge | sha256sum)" ]; then
	echo "faulty"
	exit 1
fi