This package implements the RFC 6238 OATH-TOTP algorithm

• Forked from sec51/twofactor
• Actively maintained, updates will be released under pilinux/twofactor

• Built-in support for secure crypto keys generation
• Built-in encryption of the secret keys when converted to bytes, so that they can be safely transmitted over the network, or stored in a DB
• Built-in back-off time when a user fails to authenticate more than 3 times
• Built-in serialization and deserialization to store the one time token struct in a persistence layer
• Automatic re-synchronization with the client device
• Built-in generation of a PNG QR Code for easily adding the secret key on the user device
• Supports 6, 7, 8 digits tokens
• Supports HMAC-SHA1, HMAC-SHA256, HMAC-SHA512
• Generation of recovery tokens

The key is created using Golang crypto random function. It's a secret key and therefore it needs to be protected against unauthorized access. The key cannot be leaked, otherwise the security is completely compromised. The key is presented to the user in a form of QR Code. Once scanned, the key should never be revealed again. In addition when the QR code is shared with the client for scanning, the connection used must be secured (HTTPS).

The totp struct can be easily serialized using the ToBytes() function. The bytes can then be stored on a persistence layer (database for example). The bytes are encrypted using cryptoengine library (NaCl) You can then retrieve the object back with the function: TOTPFromBytes

You can transfer the bytes securely via a network connection (Ex. if the database is in a different server) because they are encrypted and authenticated.

The struct needs to be stored in a persistence layer because its values, like last token verification time, max user authentication failures, etc.. need to be preserved. The secret key needs to be preserved too between the user account and the user device. The secret key is in fact used to derive tokens.

• How to use the library

  • 1. Import the library

  import github.com/pilinux/twofactor

  • 2. Instantiate the totp object via:

  otp, err := twofactor.NewTOTP("[email protected]", "Sec51", crypto.SHA1, 8)
  if err != nil {
    return err
  }

  • 3. Display the PNG QR code to the user and an input text field, so that he can insert the token generated from his device

  qrBytes, err := otp.QR()
  if err != nil {
    return err
  }

  • 4. Verify the user-provided token generating by the google authenticator app

  err := otp.Validate(USER_PROVIDED_TOKEN)
  if err != nil {
    return err
  }
  // if there is an error, then the authentication failed
  // if it succeeded, then store this information and do not display the QR code ever again.

  • 5. All following authentications should display only a input field with no QR code.

• RFC 6238 - TOTP: Time-Based One-Time Password Algorithm
• The Key URI Format

totp was written by Sec51 [email protected].

Copyright (c) 2015 Sec51.com <[email protected]>

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above 
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.