Authentication is a critical component to your daily development. When working in open source, you need to prove that you have rights to update a branch with
git push
. Additionally when working on proprietary software, you need a way to prove that you even have read permission to access your code during
git fetch
or
git pull
.
Git currently supports two authentication mechanisms for accessing remotes. When using HTTP(S), Git sends a username and password, or a personal access token (PAT) via HTTP headers. When using SSH, Git relies on
the server knowing your machine’s public SSH key
. Though SSH-based authentication is considered most secure, setting it up correctly can often be a challenge. On the other hand, PATs are often much easier to set up, but also far less secure.
To manage all of this, Git relies on tools called
credential managers
which handle authentication to different hosting services. When first designed, these tools simply stored usernames and passwords in a secure location for later retrieval (e.g., your keychain, in an encrypted file, etc). These days, two-factor authentication (2FA) is commonly required to keep your data secure. This complicates the authentication story significantly since new and existing tools are required to meet the demands of these stricter authentication models.
Even though authentication is so critical, building a new authentication feature is hard. Hard to debug, hard to test, hard to get right. If you’re going to do something, then it is best to do it right. Even better, it is helpful to do it
once
. We’ve been hard at work laying the foundation for a single tool to unify the Git authentication experience across platforms and hosting services.
I’m pleased to announce a new credential manager is available for Windows and macOS:
Git Credential Manager (GCM) Core
! GCM Core is a free, open-source, cross-platform credential manager for Git, and currently supports authentication to GitHub, Bitbucket, and Azure Repos. We built this tool from the ground up with cross-platform and cross-host support in mind. We plan to extend this tool to include support for Linux platforms and authentication with additional hosting services.
But wait? Doesn’t this just mean we’ve made
yet another
credential helper?
Well yes, but actually no. GCM Core is in beta today, which means that we won’t be retiring GCM for Windows. Also without Linux support we won’t be retiring GCM for Mac & Linux, just yet.
However, once GCM Core has had some time in the wild, we will move to deprecate and retire both GCM for Windows and GCM for Mac & Linux.
GCM Core installs side-by-side with existing
Git Credential Manager for Windows
installations and will re-use any previously stored credentials. This means that you do not need to re-authenticate! Credentials created by GCM Core are also backwards compatible with GCM for Windows, should you wish to return to the older credential manager.
We are pleased our first release has support for authenticating with
GitHub
,
Azure Repos
, and
Bitbucket
. In particular, we would like to thank
@mminns
for helping us get the Bitbucket authentication mechanism working! We are excited to similarly extend support for other hosting services, including
planned support for GitLab
.
The
Git Credential Manager for Windows
(GCM for Windows) was created back in 2015 primarily to address the combined problem of a lack of SSH support in Azure Repos, then named Visual Studio Online, and a hard requirement for 2FA for many Azure Active Directory or Microsoft Account users – the authentication providers supported by Azure Repos. Over time GCM for Windows also gained support for GitHub and Bitbucket authentication through open-source contributions. Git for Windows initially shipped only with a C-based credential helper named wincred which just persisted a username/password, and did nothing regarding 2FA.
At the same time,
Git Credential Manager for Mac and Linux
(GCM for Mac & Linux) was created, focused on non-traditional Microsoft developers. That is, those not on Windows and those using non-Microsoft languages, runtimes, or toolchains.
These two codebases are completely separate, with GCM for Windows being written in C# and GCM for Mac & Linux being written in Java. GCM for Mac & Linux is also limited to Azure Repos and never got any support for GitHub or Bitbucket. Both projects have had their fair share of issues (remember: auth is hard). With the number of different authentication topologies typically present in enterprises means there’s been a number of dirty hacks added over the years to work around problems quickly.
After seeing the success of
moving the Windows OS monorepo to Git
, the Microsoft Office team approached our team with a desire to do the same with their monorepo. The catch: they have developers using macOS to build macOS and iOS clients. This means that they need cross-platform tools. As part of that, you can
read about our journey
to transition from the Windows-only
VFS for Git
to
Scalar
as a cross-platform solution for monorepo performance.
Scalar and VFS for Git are extensions to Git that make it easier to work with very large monorepos. Both of these technologies rely in part of the
GVFS Protocol
to receive information such as file sizes and individual objects on-demand from a remote repository. This mechanism only uses HTTP REST endpoints, and is not available via SSH. This means that it is even more important to have a proper credential manager on macOS.
We examined this landscape of credential managers and decided that they needed something better, and more sustainable. Thus, the idea of GCM Core was born.
With the release and introduction of .NET Core and .NET Standard, creating applications that work across Windows, macOS, and Linux is easy. The ability to bundle the
.NET runtime
with your application when publishing means you can distribute without worrying about runtime dependencies or mismatched versions.
