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https://github.com/pyauth/pyotp

Python One-Time Password Library
https://github.com/pyauth/pyotp

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Python One-Time Password Library

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README 

        
PyOTP - The Python One-Time Password Library

============================================



PyOTP is a Python library for generating and verifying one-time passwords. It can be used to implement two-factor (2FA)

or multi-factor (MFA) authentication methods in web applications and in other systems that require users to log in.



Open MFA standards are defined in `RFC 4226 `_ (HOTP: An HMAC-Based One-Time

Password Algorithm) and in `RFC 6238 `_ (TOTP: Time-Based One-Time Password

Algorithm). PyOTP implements server-side support for both of these standards. Client-side support can be enabled by

sending authentication codes to users over SMS or email (HOTP) or, for TOTP, by instructing users to use `Google

Authenticator `_, `Authy `_, or another

compatible app. Users can set up auth tokens in their apps easily by using their phone camera to scan `otpauth://

`_ QR codes provided by PyOTP.



Implementers should read and follow the `HOTP security requirements `_

and `TOTP security considerations `_ sections of the relevant RFCs. At

minimum, application implementers should follow this checklist:



- Ensure transport confidentiality by using HTTPS

- Ensure HOTP/TOTP secret confidentiality by storing secrets in a controlled access database

- Deny replay attacks by rejecting one-time passwords that have been used by the client (this requires storing the most

  recently authenticated timestamp, OTP, or hash of the OTP in your database, and rejecting the OTP when a match is

  seen)

- Throttle (rate limit) brute-force attacks against your application's login functionality (see RFC 4226, section 7.3)

- When implementing a "greenfield" application, consider supporting

  `FIDO U2F `_/`WebAuthn `_ in

  addition to or instead of HOTP/TOTP. U2F uses asymmetric cryptography to avoid using a shared secret design, which

  strengthens your MFA solution against server-side attacks. Hardware U2F also sequesters the client secret in a

  dedicated single-purpose device, which strengthens your clients against client-side attacks. And by automating scoping

  of credentials to relying party IDs (application origin/domain names), U2F adds protection against phishing attacks.

  One implementation of FIDO U2F/WebAuthn is PyOTP's sister project, `PyWARP `_.



We also recommend that implementers read the

`OWASP Authentication Cheat Sheet

`_ and

`NIST SP 800-63-3: Digital Authentication Guideline `_ for a high level overview of

authentication best practices.



Quick overview of using One Time Passwords on your phone

--------------------------------------------------------



* OTPs involve a shared secret, stored both on the phone and the server

* OTPs can be generated on a phone without internet connectivity

* OTPs should always be used as a second factor of authentication (if your phone is lost, you account is still secured

  with a password)

* Google Authenticator and other OTP client apps allow you to store multiple OTP secrets and provision those using a QR

  Code



Installation

------------

::



    pip install pyotp



Usage

-----



Time-based OTPs

~~~~~~~~~~~~~~~

::



    import pyotp

    import time



    totp = pyotp.TOTP('base32secret3232')

    totp.now() # => '492039'



    # OTP verified for current time

    totp.verify('492039') # => True

    time.sleep(30)

    totp.verify('492039') # => False



Counter-based OTPs

~~~~~~~~~~~~~~~~~~

::



    import pyotp

    

    hotp = pyotp.HOTP('base32secret3232')

    hotp.at(0) # => '260182'

    hotp.at(1) # => '055283'

    hotp.at(1401) # => '316439'



    # OTP verified with a counter

    hotp.verify('316439', 1401) # => True

    hotp.verify('316439', 1402) # => False



Generating a Secret Key

~~~~~~~~~~~~~~~~~~~~~~~

A helper function is provided to generate a 32-character base32 secret, compatible with Google Authenticator and other

OTP apps::



    pyotp.random_base32()



Some applications want the secret key to be formatted as a hex-encoded string::



    pyotp.random_hex()  # returns a 40-character hex-encoded secret



Google Authenticator Compatible

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



PyOTP works with the Google Authenticator iPhone and Android app, as well as other OTP apps like Authy. PyOTP includes

the ability to generate provisioning URIs for use with the QR Code scanner built into these MFA client apps::



    pyotp.totp.TOTP('JBSWY3DPEHPK3PXP').provisioning_uri(name='[email protected]', issuer_name='Secure App')



    >>> 'otpauth://totp/Secure%20App:alice%40google.com?secret=JBSWY3DPEHPK3PXP&issuer=Secure%20App'



    pyotp.hotp.HOTP('JBSWY3DPEHPK3PXP').provisioning_uri(name="[email protected]", issuer_name="Secure App", initial_count=0)



    >>> 'otpauth://hotp/Secure%20App:alice%40google.com?secret=JBSWY3DPEHPK3PXP&issuer=Secure%20App&counter=0'



This URL can then be rendered as a QR Code (for example, using https://github.com/soldair/node-qrcode) which can then be

scanned and added to the users list of OTP credentials.



Parsing these URLs is also supported::



    pyotp.parse_uri('otpauth://totp/Secure%20App:alice%40google.com?secret=JBSWY3DPEHPK3PXP&issuer=Secure%20App')



    >>> 



    pyotp.parse_uri('otpauth://hotp/Secure%20App:alice%40google.com?secret=JBSWY3DPEHPK3PXP&issuer=Secure%20App&counter=0'



    >>> 



Working example

~~~~~~~~~~~~~~~



Scan the following barcode with your phone's OTP app (e.g. Google Authenticator):



.. image:: https://chart.apis.google.com/chart?cht=qr&chs=250x250&chl=otpauth%3A%2F%2Ftotp%2Falice%40google.com%3Fsecret%3DJBSWY3DPEHPK3PXP



Now run the following and compare the output::



    import pyotp

    totp = pyotp.TOTP("JBSWY3DPEHPK3PXP")

    print("Current OTP:", totp.now())



Third-party contributions

~~~~~~~~~~~~~~~~~~~~~~~~~

The following third-party contributions are not described by a standard, not officially supported, and provided for

reference only:



* ``pyotp.contrib.Steam()``: An implementation of Steam TOTP. Uses the same API as `pyotp.TOTP()`.



Links

~~~~~



* `Project home page (GitHub) `_

* `Documentation `_

* `Package distribution (PyPI) `_

* `Change log `_

* `RFC 4226: HOTP: An HMAC-Based One-Time Password `_

* `RFC 6238: TOTP: Time-Based One-Time Password Algorithm `_

* `ROTP `_ - Original Ruby OTP library by `Mark Percival `_

* `OTPHP `_ - PHP port of ROTP by `Le Lag `_

* `OWASP Authentication Cheat Sheet `_

* `NIST SP 800-63-3: Digital Authentication Guideline `_



For new applications:



* `WebAuthn `_

* `PyWARP `_



Versioning

~~~~~~~~~~

This package follows the `Semantic Versioning 2.0.0 `_ standard. To control changes, it is

recommended that application developers pin the package version and manage it using `pip-tools

`_ or similar. For library developers, pinning the major version is

recommended.



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