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148 lines
4.7 KiB
Markdown
148 lines
4.7 KiB
Markdown
#### Current test status
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[](https://godoc.org/github.com/1f349/twofactor/)
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## `totp`
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This package implements the RFC 6238 OATH-TOTP algorithm;
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### Installation
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```go get github.com/1f349/twofactor```
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### Features
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* Built-in support for secure crypto keys generation
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* Built-in back-off time when a user fails to authenticate more than 3 times
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* Bult-in serialization and deserialization to store the one time token struct in a persistence layer
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* Automatic re-synchronization with the client device
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* Built-in generation of a PNG QR Code for adding easily the secret key on the user device
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* Supports 6, 7, 8 digits tokens
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* Supports HMAC-SHA1, HMAC-SHA256, HMAC-SHA512
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### Storing Keys
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> The key is created using Golang crypto random function. It's a **secret key** and therefore
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> it needs to be **protected against unauthorized access**. The key cannot be leaked, otherwise the security is completely compromised.
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> The key is presented to the user in a form of QR Code. Once scanned the key should never be revealed again.
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> In addition when the QR code is shared with the client for scanning, the connection used must be secured (HTTPS).
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The `totp` struct can be easily serialized using the `ToBytes()` function.
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The bytes can then be stored on a persistent layer (database for example). The bytes are encrypted using `cryptoengine` library (NaCl)
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You can then retrieve the object back with the function: `TOTPFromBytes`
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> 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.
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The struct needs to be stored in a persistent layer because its values, like last token verification time,
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max user authentication failures, etc.. need to be preserved.
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The secret key needs to be preserved too, between the user account and the user device.
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The secret key is in fact used to derive tokens.
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### Upcoming features
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* Generation of recovery tokens.
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* Integration with Twilio for sending the token via SMS, in case the user loses its entry in the Google authenticator app.
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### Example Usages
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#### Case 1: Google Authenticator
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* How to use the library
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1- Import the library
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```
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import github.com/1f349/twofactor
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```
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2- Instanciate the `totp` object via:
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```
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otp, err := twofactor.NewTOTP("info@sec51.com", "Sec51", crypto.SHA1, 8)
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if err != nil {
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return err
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}
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```
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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
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```
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qrBytes, err := otp.QR()
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if err != nil {
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return err
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}
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```
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4- Verify the user provided token, coming from the google authenticator app
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```
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err := otp.Validate(USER_PROVIDED_TOKEN)
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if err != nil {
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return err
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}
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// if there is an error, then the authentication failed
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// if it succeeded, then store this information and do not display the QR code ever again.
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```
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5- All following authentications should display only a input field with no QR code.
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#### Case 2: Calculate OTP from secret
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If you used the totp.Secret() function, you got a string, so first we have to convert it back into an []byte
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object and after start to initialize the object.
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```go
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secretBytes, err := base32.StdEncoding.DecodeString(reqSecret.TwofactorSecret)
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if err != nil {
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panic(fmt.Errorf("couldn't convert base32 secret to string: %w", err))
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}
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totp, err := twofactor.NewTOTPWithKey(secretBytes, "YOUR_USER_ACCOUNT", "YOUR_ISSUER", crypto.SHA256, 6)
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if err != nil {
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panic(fmt.Errorf("couldn't create TOTP object: %w", err))
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}
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otp := twofactor.CalculateTOTP(totp, 0)
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fmt.Printf("OTP: %v\n", otp)
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```
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### References
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* [RFC 6238 - *TOTP: Time-Based One-Time Password Algorithm*](https://tools.ietf.org/rfc/rfc6238.txt)
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* The [Key URI Format](https://github.com/google/google-authenticator/wiki/Key-Uri-Format)
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### Author
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Initialliy `totp` was written by Sec51 <info@sec51.com> and the further development was made by dnnspaul <dennis@blaumedia.com> and 1f349.
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### License
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```
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Copyright (c) 2015 Sec51.com <info@sec51.com>
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Permission to use, copy, modify, and distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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```
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