Google Authenticator

A Clojure program to compute your google authenticator otp. I personally use this to automate connecting to VPNs along with apple script. But you could find other use cases where you would want to automate the computation and submission of the OTP.

TOTP

Google authenticator uses Totp (Time based One Time Password) for 2 factor authentication. When you/your app registers with google authenticator, google gives you a shared secret key (could be in the form of QR code). The shared key is a Base32Encoded String that looks like this JBSWY3DPEHPK3PXP

TOTP algorithm computes the Otp by doing a HMAC of the secret key and current time stamp (expressed as steps of 30 seconds from EPOCH). So, the OTP changes every 30 seconds. You can read more about the algorithm here.

Usage (JVM)

This program takes in a file containing your secret key (base32 encoded) as an argument and an optional argument specifying the path of the file where the otp will be written to. If the second argument is not specified it prints the otp to console.

make apply-patch
lein compile
lein uberjar
cd target

Since we are using cli-matic, we can see the ways to run this program by giving

java -jar target/google_authenticator-0.1.0-SNAPSHOT-standalone.jar p --help

You should see an output similar to this

NAME:
 google-authenticator gen-otp - Generates google authenticator otp and prints it to the console

USAGE:
 google-authenticator [gen-otp|p] [command options] [arguments...]

OPTIONS:
   -sk, --secret-key S  Parameter A
   -?, --help

Example 1 - Print OTP on to the console

java -jar target/google_authenticator-0.1.0-SNAPSHOT-standalone.jar p --secret-key j4ok7qmclj23gwa336rrjrv123456789

Example 2 - Read secret key from a file and write otp to a file

java -jar target/google_authenticator-0.1.0-SNAPSHOT-standalone.jar o --secret-key-file-path ~/.secret_key --output-file ~/.otp

Usage (GraalVM)

Please follow the instruction here to generate a native image - https://www.graalvm.org/docs/reference-manual/native-image/

Commands executed to generate native image via GraalVM-19.2.1

1. Download graalvm-19.2.1

2. Install native image component by executing

   gu install native-image

3. Copy the standalone jar generated by lein uberjar to the bin directory inside graalvm.

4. Run the following command to generate a native image (assuming your jar is named google_authenticator.jar)

./native-image --report-unsupported-elements-at-runtime --initialize-at-build-time -jar google_authenticator.jar -H:Name=google_authenticator --no-fallback --enable-all-security-services

Example 1 - Print OTP on to the console

./google_authenticator p --secret-key j4ok7qmclj23gwa336rrjrv123456789

Example 2 - Read secret key from a file and write otp to a file

./google_authenticator o --secret-key-file-path ~/.secret_key --output-file ~/.otp