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PAM module for OAuth 2.0 Device Authorization Grant

PAM module for user authentication using OAuth 2.0 Device Authorization Grant.

The following instructions have been tested on Ubuntu 20.04.

Installation

Install build dependencies.

sudo apt install libldap2-dev libpam0g-dev libcurl4-openssl-dev

Clone the repository, build and install the module.

make
sudo mkdir /lib/security
sudo cp pam_oauth2_device.so /lib/security/

Create a configuration file /etc/pam_oauth2_device/config.json. See config_template.json (LDAP section is optional).

Configuration options

Edit /etc/pam_oauth2_device/config.json.

  • qr QR code encodes the authentication URL.
    • show: show (true, default) or hide (false) the QR code
    • error_correction_level: allowed correction levels are
      • 0 - low
      • 1 - medium
      • 2 - high
  • users User mapping from claim configured in username_attribute to the local account name.
  • oauth configuration for the OIDC identity provider.
    • require_mfa: if true the module will modify the requests to ask user to perform the MFA.

Example Configuration for sshd

Edit /etc/pam.d/sshd. Enable pam_oauth2_device.so and disable password authentication.

auth required pam_oauth2_device.so /etc/pam_oauth2_device/config.json

# Standard Un*x authentication.
# @include common-auth

Edit /etc/ssh/sshd_config

PasswordAuthentication no
ChallengeResponseAuthentication yes
AuthenticationMethods keyboard-interactive
UsePAM yes

It is also possible to combine multiple authentication methods. For example, with AuthenticationMethods publickey,keyboard-interactive both public key and interactive authentication are required.

For service users, an interactive method might not be desirable. Specify alternative authentication methods for selected users.

Match User ubuntu
  AuthenticationMethods publickey

Restart the service after changing the sshd configuration.

systemctl restart sshd

Development

For local development it is easier to use pamtester.

sudo apt install pamtester

Configuration

Edit /etc/pam.d/pamtester

auth required pam_oauth2_device.so

Deployment

sudo cp pam_oauth2_device.so /lib/security/
# or make a symlink so you don't need to copy the file each
# time you compile the module
sudo ln -s pam_oauth2_device.so /lib/security/

Testing

pamtester -v pamtester username authenticate

Contributing

In this project we automatically generate releases and update the changelog (for more information see, this github action). For this reason commit messages need to follow the Conventional Commits specification.

To improve both code quality and consistency, every commit needs to pass linter and formatter checks. Please follow the Google C++ style guide. You can use clang-format to automatically format your code. Formatter can be integrated with most IDEs or used from CLI, e.g. clang-format --style Google -i src/pam_oauth2_device.cpp

You can run linter (cpplint) locally with cpplint src/* src/include/*. cpplint is a Python tool and can be pip installed pip install cpplint

Make sure that unit tests are passing, see test/README.md. Add new tests if necessary.

Security review

The code has been reviewed for security vulnerabilities at the University of Basel and Swiss Institute of Bioinformatics by Louis Ruppert and Aurélien Cavelan.