How can developers avoid a Git repository security risk?

Web developers increasingly rely on Git to manage their source code, but they should also consider the importance of Git repository security. Most web projects today use the Git source code control system, where Git repository metadata and packed versions of the files in the repository are stored in a hidden subdirectory named ".git".

When a web page is deployed directly from a Git repository, the Git directory and its contents may also be accessible through the web page. An attacker can use URLs like https://example.org/.git/config and access the metadata. Attackers and security scanner tools often use this configuration file to check targeted web pages for such vulnerabilities. There are also publicly available tools that enable complete downloads of the repository content if the .git directory is accessible.

While other source code version control management systems like Subversion (directory ".svn") or Mercurial (directory ".hg") are similarly exposed to this Git repository security risk, these systems are rarely used anymore.

The repository metadata and content can give an attacker helpful information for further attacks. The repository not only potentially reveals the web page source code -- passwords, secret tokens or confidential customer data could also be exposed.

A particularly risky scenario can happen if a Git repository is checked out using HTTP authentication where the username and password to access the repository are incorporated as part of the URL. This information is stored in the .git/config file and can give an attacker direct access to credentials for the repository.

To improve Git repository security and avoid these risks, developers should avoid using direct Git checkouts on web deployments. Instead, the files should be copied to the web root directory without the .git directory metadata. Alternatively, one can also prevent access to the .git directory in the server configuration. It's also good practice to not store passwords and secret tokens directly in repositories.

HTTP authentication with passwords for checkouts should be generally avoided for better Git repository security. Public key authentication with SSH public/private key pairs is much safer. Furthermore, Git accounts used for deployments should have minimum privileges without any write access to repositories.