check

#!/bin/sh -eu
#
# Ugly reference implementation of Hacklab membership check based on
# email address

if test $# -ne 3; then
    echo Usage: $0 hashfile hmac email >&2
    exit 1
fi

normalized=`echo "$3" | sed -sr 's/^\s?(.*)\s?*/\1/' | tr [:upper:] [:lower:] | sed -s 's/+[^@]*@/@/'`
hmac=`echo -n "$normalized" | openssl dgst -sha256 -hmac "$2" -binary | hexdump -e '32/1 "%02x" "\n"'`
hexdump -e '32/1 "%02x" "\n"' <"$1" | if grep -q ^$hmac$; then
    echo "Special price just for you!"
else
    echo "Ordinary customer"
fi