Check password against pwnedpasswords repo.

checkpass.sh

#!/bin/bash

# Original:
# https://blog.cloudflare.com/validating-leaked-passwords-with-k-anonymity

echo -n Password:
read -s password
echo
hash="$(echo -n $password | openssl dgst -sha1 -binary | xxd -p)"
upperCase="$(echo $hash | tr '[a-z]' '[A-Z]')"
prefix="${upperCase:0:5}"
response=$(curl -s https://api.pwnedpasswords.com/range/$prefix)
while read -r line; do
  lineOriginal="$prefix$line"
  if [ "${lineOriginal:0:40}" == "$upperCase" ]; then
    howmany=$(echo $lineOriginal | cut -d":" -f2 | tr -d "\n\r")
    echo "Password breached $howmany times!"
    exit 1
  fi
done <<< "$response"

echo "Password not found in breached database."
exit 0

See https://www.troyhunt.com/ive-just-launched-pwned-passwords-version-2/

Changed the openssl oneliner to support modern versions.