KAS-CREDENTIALS(1)

NAME
kas-credentials - kas credential handling

CREDENTIAL HANDLING

kas provides various mechanisms to inject credentials into the build. By using Environment Variables <#env-vars-label>, a fine grained control is possible. All credentials are made available both to KAS, as well as inside the build environment. However, not all mechanisms are natively supported by all tools. As kas might need to modify credentials and config files, these are copied into the isolated environment first.

Note:
        In general, file based credentials (e.g. .netrc) are only copied if explicitly requested by setting the corresponding environment variable. Environment variable based credentials are automatically forwarded.

For details about credential related environment variables, see kas(1).

  AWS Configuration

For AWS, conventional AWS config files, AWS SSO as well as the environment variable controlled OAuth 2.0 workflow are supported. Note, that KAS internally rewrites the AWS_* environment variables into a AWS config file to also support older versions of bitbake.

Note:
        When using AWS_CONFIG_FILE the entire content of ~/.aws/sso/cache directory is copied into the kas workspace. This might expose all active user sessions, including those not defined in the AWS_CONFIG_FILE. To mitigate security risks, log out of unnecessary profiles before starting a build or use a separate system account to run the build.

  Git Configuration

A .gitconfig file can be used to provide credentials as well as URL rewrites of git repositories (insteadof). In addition, credential helpers can be used by setting the corresponding environment variables. These are added to the .gitconfig file as well. To support the patching of git repositories, kas injects a [user] section, possibly overwriting an existing one. After patching, the original user is restored (if set).

When running in a GitHub Action or GitLab CI job, the .gitconfig file is automatically injected. Otherwise, the environment variable GITCONFIG_FILE needs to point to the .gitconfig kas should use.

  Git credential cache

You can share git credentials with the kas-container by using the Git credential cache helper. This allows credentials to be securely stored in memory via a background daemon and reused across Git operations without re-entering them or writing them to disk in plain text.

For a full description of the available options, refer to the official git-credential-cache documentation <https://git-scm.com/docs/git-credential-cache>.

Enable credential caching on your host machine with a command like:

            git config --global credential.helper 'cache --timeout=86400'

Note:
        The --timeout value (in seconds) controls how long credentials are kept in the cache after the last use. The value 86400 (24 hours) is just an example. Adjust it to fit your workflow and security requirements.

From the host, perform a Git operation that requires authentication, such as a git pull against a password-protected repository:

            git pull

After entering your credentials once, Git will store them and make them available through a background daemon that exposes a Unix socket.

You should see a running process similar to this on your host:

            /usr/lib/git-core/git credential-cache--daemon $HOME/.cache/git/credential/socket

Now you can launch the kas container passing the socket path via --git-credential-socket, or equivalently by setting the KAS_GIT_CREDENTIAL_SOCKET environment variable:

            kas-container --git-credential-socket $HOME/.cache/git/credential/socket <other options...>

Note:
        The git credential-cache daemon supports custom socket paths via the --socket flag. This allows running a separate daemon per repository, enabling credential isolation between projects. To use this, start the daemon explicitly with a custom socket path and pass that path to --git-credential-socket.

  GitHub Actions

In combination with the webfactory/ssh-agent <https://github.com/webfactory/ssh-agent> action, this automatically makes the required credentials available to kas and bitbake.

  GitLab CI

When running in the GitLab CI, the CI_JOB_TOKEN can be used to access git repositories via https. If CI_SERVER_HOST is also set, kas automatically adds this token to the .netrc file, where it is picked up by git. Further, kas configures git to automatically rewrite the URLs of the repositories to clone via https for repos stored on the same server. Technically this is achieved by adding insteadof entries to the .gitconfig file.

For backwards compatibility, the git rewrite rules are only added if .gitconfig does not exist and no SSH configuration is provided (either via the kas SSH_ variables or using .ssh/config).

If the CI_REGISTRY, CI_REGISTRY_USER and CI_JOB_TOKEN variables are set, kas automatically creates a login file for the container registry at ~/.docker/config.json. This file is compatible with docker, podman and even skopeo.

Note:
        Make sure to assign the correct permissions to the CI_JOB_TOKEN. For details, see GitLab CI/CD job token <https://docs.gitlab.com/ee/ci/jobs/ci_job_token.html>.

  Container Registry Authentication File

A file named config.json is saved as .docker/config.json in the kas home directory. It contains credentials for the container registry login. The syntax is described in the containers-auth.json specification <https://github.com/containers/image/blob/main/docs/containers-auth.json.5.md>. The authentication file is compatible with docker, podman and skopeo. When running in the GitLab CI, the CI_JOB_TOKEN is appended to automatically grant access according to the job permissions.

  Netrc File

A .netrc file can be used to provide credentials for git or the HTTP(S) / FTP fetcher. When running in the GitLab CI, the CI_JOB_TOKEN is appended to automatically grant access to repositories that can be accessed by the user that triggered the CI pipeline.

  SSH

The ssh folder of the calling user is automatically shared with kas. This is currently not controllable, as ssh does not obey the $HOME variable. This can be used to inject both credentials, as well as ssh configuration items into the kas environment.

Note:
        Modifications to the .ssh/config file are only performed if the file is not present yet. In well-known CI environments, kas also disables ssh host key checking when SSH_PRIVATE_KEY or SSH_PRIVATE_KEY_FILE is set. Because this change persists across kas invocations, kas does not apply it in local environments, starting with kas 5.4.

In addition, an external ssh-agent can be made available in the kas environment by setting the SSH_AUTH_SOCK environment variable. As an alternative, ssh private keys can be added to an internal ssh agent by setting SSH_PRIVATE_KEY or SSH_PRIVATE_KEY_FILE.

Note:
        The use of an external ssh agent cannot be combined with options that require an internal ssh agent.

KAS

Part of the kas(1) suite.

Author
Daniel Wagner, Jan Kiszka, Claudius Heine

Copyright
Siemens and contributors, 2017-2025