Install google-authenticator-libpam with Homebrew, zypper, apk, apt, dnf, Nix

Project links

• Homepage
• Upstream docs
• Package manager page

Commands and aliases

• google-authenticator

Project history

The project implements a PAM module named pam_google_authenticator and a google-authenticator setup binary. The README describes it as an example PAM module for two-factor authentication to servers via SSH, OpenVPN, and similar services, and explicitly scopes it away from logging into Google or other TOTP/HOTP services.

The implementation is grounded in the HOTP and TOTP standards. RFC 4226 defined HMAC-based one-time passwords in 2005, and RFC 6238 extended HOTP with a time-based moving factor in 2011. The project's README cites both standards as the algorithms behind its one-time codes.

The GitHub repository was created in November 2016 under Google's organization, and Git tags show 1.03 through 1.11 release labels. The man page documents the PAM module interface, default secret-file behavior, security notes, and deployment options.

Adoption history

The package is widely packaged under names such as google-authenticator-libpam, google-authenticator, and libpam-google-authenticator. The batch metadata records Homebrew, Alpine, Debian, Fedora, Nix, Ubuntu, and openSUSE-family package names, and Homebrew's formula page documents SSH PAM configuration snippets.

Its adoption comes from fitting an existing Unix security boundary: administrators can add an auth required pam_google_authenticator.so line to PAM configuration and let users enroll per-account secrets, rather than deploying a separate authentication server.

Because PAM is distribution- and service-sensitive, the project also exposes rollout controls such as nullok for users without a secret file, secret= for nonstandard secret locations, user= for alternate file access, owner and permission checks, time-skew handling, HOTP counter behavior, and combined password-code prompting.

How it is used

A user typically runs google-authenticator to create ~/.google_authenticator. The setup can display a QR code when libqrencode is available, or provide a URL or alphanumeric secret that can be entered into an authenticator app.

An administrator enables the PAM module in a service configuration, commonly with an auth line for pam_google_authenticator.so. The module then prompts for a one-time code in addition to the normal password, using either time-based TOTP or counter-based HOTP depending on user setup and options.

The man page emphasizes that the secret file is per account, defaults to .google_authenticator in the user's home directory, and must satisfy ownership and permission checks unless explicitly relaxed.

Why package nerds care

For package nerds, google-authenticator-libpam is a classic example of a small library package with outsized operational consequences. Packaging has to put a PAM shared object in the right security module path, install a user enrollment binary, and often provide service-specific post-install guidance.

It is also a good reminder that authentication packages are not just CLIs. Their paths, file permissions, PAM control flags, and distro integration details can determine whether users are protected, locked out, or silently bypassing a second factor.

Timeline

• 2005: RFC 4226 publishes HOTP.
• 2011: RFC 6238 publishes TOTP as a time-based extension of HOTP.
• 2016-11: Google GitHub repository created.
• 2016-2026: Git tags show 1.03 through 1.11 release labels.
• 2026: README and man page document PAM setup, ~/.google_authenticator secrets, HOTP/TOTP behavior, and security-sensitive module options.

Related projects

• Google Authenticator mobile apps generate compatible one-time codes for enrolled secrets.
• Linux-PAM and service PAM configurations such as sshd and OpenVPN are the integration surfaces for the module.
• pam_oath, FreeOTP, oathtool, and other OATH-compatible tooling occupy adjacent HOTP/TOTP authentication space.

Sources

• https://api.github.com/repos/google/google-authenticator-libpam
• https://formulae.brew.sh/formula/google-authenticator-libpam
• https://github.com/google/google-authenticator-libpam
• https://raw.githubusercontent.com/google/google-authenticator-libpam/master/README.md
• https://raw.githubusercontent.com/google/google-authenticator-libpam/master/man/pam_google_authenticator.8.md
• https://sources.debian.org/src/google-authenticator/
• https://www.rfc-editor.org/rfc/rfc4226
• https://www.rfc-editor.org/rfc/rfc6238