Connect to cloud services

• CI_JOB_JWT variable for reading secrets from Vault introduced in GitLab 12.10.
• CI_JOB_JWT_V2 variable to support additional OIDC providers introduced in GitLab 14.7.

GitLab CI/CD supports OpenID Connect (OIDC) that allows your build and deployment job access to cloud credentials and services. Historically, teams stored secrets in projects or applied permissions on the GitLab Runner instance to build and deploy. To support this, a predefined variable named CI_JOB_JWT_V2 is included in the CI/CD job allowing you to follow a scalable and least-privilege security approach.

Requirements

• Account on GitLab.
• Access to a cloud provider that supports OIDC to configure authorization and create roles.

The original implementation of CI_JOB_JWT supports HashiCorp Vault integration. The updated implementation of CI_JOB_JWT_V2 supports additional cloud providers with OIDC including AWS, GCP, and Vault.

WARNING: The CI_JOB_JWT_V2 variable is under development (alpha) and is not yet suitable for production use.

Use cases

• Removes the need to store secrets in your GitLab group or project. Temporary credentials can be retrieved from your cloud provider through OIDC.
• Provides temporary access to cloud resources with granular GitLab conditionals including a group, project, branch, or tag.
• Enables you to define separation of duties in the CI/CD job with conditional access to environments. Historically, apps may have been deployed with a designated GitLab Runner that had only access to staging or production environments. This led to Runner sprawl as each machine had dedicated permissions.
• Allows shared runners to securely access multiple cloud accounts. The access is determined by the JWT token, which is specific to the user running the pipeline.
• Removes the need to create logic to rotate secrets by retrieving temporary credentials by default.

How it works

Each job has a JSON web token (JWT) provided as a CI/CD predefined variable named CI_JOB_JWT or CI_JOB_JWT_V2. This JWT can be used to authenticate with the OIDC-supported cloud provider such as AWS, GCP, or Vault.

The following fields are included in the JWT:

{
  "jti": "c82eeb0c-5c6f-4a33-abf5-4c474b92b558",
  "iss": "https://gitlab.example.com",
  "aud": "https://gitlab.example.com",
  "iat": 1585710286,
  "nbf": 1585798372,
  "exp": 1585713886,
  "sub": "project_path:mygroup/myproject:ref_type:branch:ref:main",
  "namespace_id": "1",
  "namespace_path": "mygroup",
  "project_id": "22",
  "project_path": "mygroup/myproject",
  "user_id": "42",
  "user_login": "myuser",
  "user_email": "myuser@example.com",
  "pipeline_id": "1212",
  "pipeline_source": "web",
  "job_id": "1212",
  "ref": "auto-deploy-2020-04-01",
  "ref_type": "branch",
  "ref_protected": "true",
  "environment": "production",
  "environment_protected": "true"
}

Authorization workflow

sequenceDiagram
    participant GitLab
    Note right of Cloud: Create OIDC identity provider
    Note right of Cloud: Create role with conditionals
    Note left of GitLab: CI/CD job with CI_JOB_JWT_V2
    GitLab->>+Cloud: Call cloud API with CI_JOB_JWT_V2
    Note right of Cloud: Decode & verify JWT with public key (https://gitlab/-/jwks)
    Note right of Cloud: Validate audience defined in OIDC
    Note right of Cloud: Validate conditional (sub, aud) role
    Note right of Cloud: Generate credential or fetch secret 
    Cloud->>GitLab: Return temporary credential
    Note left of GitLab: Perform operation 

1. Create an OIDC identity provider in the cloud (for example, AWS, GCP, Vault).
2. Create a conditional role in the cloud service that filters to a group, project, branch, or tag.
3. The CI/CD job includes a predefined variable CI_JOB_JWT_V2 that is a JWT token. You can use this token for authorization with your cloud API.
4. The cloud verifies the token, validates the conditional role from the payload, and returns a temporary credential.

Configure a conditional role with OIDC claims

To configure the trust between GitLab and OIDC, you must create a conditional role in the cloud provider that checks against the JWT token. The condition is validated against the JWT to create a trust specifically against two claims, the audience and subject.

• Audience or aud: The URL of the GitLab instance. This is defined when the identity provider is first configured in your cloud provider.
• Subject or sub: A concatenation of metadata describing the GitLab CI/CD workflow including the group, project, branch, and tag. The sub field is in the following format:
  • project_path:{group}/{project}:ref_type:{type}:ref:{branch_name}

OIDC authorization with your cloud provider

To connect with your cloud provider, see the following tutorials:

• Configure OpenID Connect in AWS