git-credential-oauth

README

git-credential-oauth

No more passwords! No more personal access tokens! No more SSH keys!

git-credential-oauth is a Git credential helper that securely authenticates to GitHub, GitLab, BitBucket and Gerrit using OAuth.

The first time you authenticate, the helper opens a browser window to the host. Subsequent authentication within storage lifetime is non interactive.

Motivation

Git assumes users can type a password from memory, but hosts such as GitHub no longer accept passwords without two-factor authentication. Personal access tokens are easy enough to copy and paste but awkward to store securely. git-credential-cache works well for passwords but not personal access tokens because the token is lost when the cache expires. All in all, the usability is so poor that the most popular advice on StackOverflow is to insecurely save credentials in plaintext!

OAuth has multiple advantages over personal access tokens or SSH:

Advantage	OAuth	Personal access token	SSH
Clone public repo without setup	✓	✓	🗙
Authenticate to popular hosts without setup	✓	🗙	🗙
Server authenticity verified automatically	✓	✓	🗙
Protections against token theft[^1]	✓	🗙	only if key has passphrase

[^1]: Scenario: an old disk backup is leaked.

Installation

All platforms

Download binary from https://github.com/hickford/git-credential-oauth/releases.

Then test that Git can find the application:

git credential-oauth

If you have problems, make sure that the binary is located in the path and is executable.

Linux

Several Linux distributions include a git-credential-oauth package including Fedora, Debian and Ubuntu. Ubuntu users can also use PPA hickford/git-credential-oauth to install the latest release.

macOS

Homebrew

macOS users can install from Homebrew:

brew install git-credential-oauth

MacPorts

macOS users can alternatively install via MacPorts:

sudo port install git-credential-oauth

Windows

Install with winget:

winget install hickford.git-credential-oauth

Go users

Go users can install the latest release to ~/go/bin with:

go install github.com/hickford/git-credential-oauth@latest

Configuration

As a convenience, you can run:

git credential-oauth configure

This uses the recommended config below.

How it works

Git is cleverly designed to support multiple credential helpers. To fill credentials, Git calls each helper in turn until it has the information it needs. git-credential-oauth is a read-only credential-generating helper, designed to be configured in combination with a storage helper.

To configure together with git-credential-cache:

git config --global --unset-all credential.helper
git config --global --add credential.helper "cache --timeout 7200" # two hours
git config --global --add credential.helper oauth

You may choose a different storage helper such as osxkeychain, wincred or libsecret, but git-credential-oauth must be configured last. This ensures Git checks for stored credentials before generating new credentials.

Windows users must use storage helper wincred because git-credential-cache isn't available on Windows.

Manual config

Edit your global git config ~/.gitconfig to include the following lines:

[credential]
	helper = cache --timeout 7200	# two hours
	helper = oauth

Browserless systems

On systems without a web browser, set the -device flag to authenticate on another device using OAuth device flow.

[credential]
	helper = cache --timeout 7200	# two hours
	helper = oauth -device

Currently only GitHub supports this flow. See GitLab feature request #332682.

Unconfiguration

Edit ~/.gitconfig manually, or run:

git config --global --unset-all credential.helper oauth

Custom hosts

To use with a custom host, eg. gitlab.example.com:

1. Register an OAuth application on the host. The GitLab instructions are typical.
   • Specify name git-credential-oauth
   • Specify redirect URI http://127.0.0.1.
   • Select scopes for read and write Git operations.
2. Adjust the config commands below with the generated client id and space-separated scopes.
3. Share the config commands with colleagues so they can skip the registration step.

git config --global credential.https://gitlab.example.com.oauthClientId <CLIENTID>
git config --global credential.https://gitlab.example.com.oauthScopes read_repository write_repository
git config --global credential.https://gitlab.example.com.oauthAuthURL /oauth/authorize
git config --global credential.https://gitlab.example.com.oauthTokenURL /oauth/token

Would you like to see universal GitLab support? *Vote for GitLab issue #374172.

Philosophy

• Do one thing well, namely OAuth authentication.
• Interoperate with other credential helpers.
• Contribute upstream to improve the ecosystem.

Comparison with Git Credential Manager

Git Credential Manager (GCM) is an excellent credential helper with broader functionality. However because it's developed in .NET, GCM is prohibitively difficult for Linux distributions to package.

	Git Credential Manager	git-credential-oauth
Cross platform	✓	✓
Linux arm64 support	🗙	✓
Packaged in Linux distributions	🗙	✓ (many)
Installation size (Linux)	82 MB	5 MB
Installation size (Windows)	4 MB	5 MB
Ships with Git for Windows	✓	🗙
Credential storage	In built	Used together with any storage helper
Development	.NET	Go
Lines of code	40,000	400
Minimum HTTP requests	1	0
Authentication to Azure DevOps	✓	🗙 (try git-credential-azure)
Hosts with default config	4	12

The maintainer personally uses GCM on Windows and git-credential-oauth on Linux.

Development

Install locally with go install ..

Debugging

Use the -verbose flag to print more details:

git config --global --unset-all credential.helper oauth
git config --global --add credential.helper "oauth -verbose"

You can also test git-credential-oauth in isolation:

echo host=gitlab.com\nprotocol=https | git-credential-oauth -verbose get

You can test configured helpers in combination with git credential fill, eg.

echo url=https://gitlab.com | git credential fill

To see which helpers Git calls, set export GIT_TRACE=1.

See also

• git-credential-azure: a Git credential manager that authenticates to Azure Repos
• Git Credential Manager

Documentation

Overview

Copyright 2022 Google LLC

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.