Last active
September 5, 2024 16:22
-
-
Save michaelkitson/e3860a63ec3cbc574cbdd40d94d5695c to your computer and use it in GitHub Desktop.
A bash function to generate TOTP codes
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| #!/usr/bin/env bash | |
| set -euo pipefail | |
| # Dependencies: openssl, xxd, base32 (coreutils) | |
| # generate_totp key [time_sec [digits]] | |
| generate_totp() { | |
| key=$1 | |
| key_hex=$(base32 -d <<<"$key" | xxd -plain) | |
| time_sec=${2:-$(date +%s)} | |
| digits=${3:-6} | |
| time_step=$((time_sec / 30)) | |
| time_step_hex=$(printf "%016x" $time_step) | |
| hash_hex=$(xxd -revert -plain <<< "$time_step_hex" | openssl sha1 -mac HMAC -macopt "hexkey:$key_hex" -binary | xxd -plain) | |
| offset=$((16#${hash_hex:39})) | |
| offset_str="${hash_hex:$((offset * 2)):8}" | |
| byte0=$(((16#${offset_str:0:2} & 127) << 24)) | |
| byte1=$((16#${offset_str:2:2} << 16)) | |
| byte2=$((16#${offset_str:4:2} << 8)) | |
| byte3=$((16#${offset_str:6:2})) | |
| bin_code=$((byte0 + byte1 + byte2 + byte3)) | |
| printf "%0${digits}d" $((bin_code % (10 ** digits))) | |
| } | |
| generate_totp AC6ZWNRLFOG5JUQHC5YW6BXX2K675AZL | tee >(pbcopy) | |
| printf "\n" |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment