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Verify SLSA with Harness GitLab CI/CD

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Modern software supply chains often rely on provenance to establish how software artifacts were built and where they originated. However, simply generating provenance is not enough. Without verifying its authenticity, organizations cannot determine whether an artifact was produced by a trusted build process or whether its provenance has been modified or forged before deployment.

Harness Supply Chain Security (SCS) integrates with GitLab CI/CD to automate SLSA provenance verification as part of your GitLab workflow. It enables you to verify the provenance associated with container images or local artifacts during pipeline execution before they are promoted or deployed. By validating the provenance against trusted signing identities, you can establish confidence in your software artifacts and strengthen software supply chain security.

What will you learn in this topic?​

By the end of this topic, you will be able to:

  • Set up Harness GitLab CI/CD integration from your SCS project.
  • Configure SLSA provenance verification in your GitLab workflow using the SLSA Verification component.
  • Configure provenance verification using keyless, key-based, or Secret Manager verification methods.
  • Verify SLSA provenance before promoting or deploying software artifacts.

Before you begin​

Make a note of the following before you proceed with verifying SLSA provenance using GitLab CI/CD:

  • Understand how to create Harness API keys using Personal API Keys or Service Account API Keys. For more information, go to Manage API Keys and Service Account API Keys, respectively.
  • If you're using key-based or Secret Manager signing or verification, create or configure a Cosign key pair before configuring the pipeline. For step-by-step instructions, see Quickstart Signing and Verifying with Cosign, which explains how to generate a local key pair or create one using a supported KMS provider. The key should be generated using Cosign of type ecdsa-P256. You don't need to install Cosign on your GitLab runner. The harness/ssca-plugin container image used by the Harness GitLab CI/CD components includes Cosign, so no additional installation is required.
  • If you plan to use Secret Manager attestation, store your verification key in a supported secret manager. Currently, Harness supports HashiCorp Vault. For GitLab CI/CD, you point the component at the key through pipeline variables such as KMS_KEY (and VAULT_ADDR when the key is stored in HashiCorp Vault), so you don't need to configure a Harness Secret Manager connector. For setup steps specific to HashiCorp Vault, see the Add a HashiCorp Vault secret manager.
  • Ensure that your GitLab runners support Docker-in-Docker (DinD). The component runs using the docker:24-dind service. For more information, go to Use Docker-in-Docker.

Understand SLSA verification with Harness GitLab CI/CD​

Harness SCS integrates with GitLab CI/CD through reusable GitLab CI/CD components. These components enable you to automate software supply chain security tasks in your GitLab pipelines, helping you build, verify, and govern software artifacts without adding custom implementation to your CI/CD workflow.

The SLSA Verification component validates the SLSA provenance associated with a container image or local artifact during pipeline execution. It confirms that the artifact originated from a trusted build process and that the associated provenance has not been modified before the artifact proceeds through your delivery pipeline. It supports keyless, key-based, and Secret Manager verification methods to verify the provenance against a trusted identity or verification key. It verifies that the artifact originated from the expected build process before allowing it to proceed through subsequent stages of the pipeline. By verifying provenance as part of your GitLab workflow, you can establish trust in software artifacts, strengthen software supply chain security, and ensure that only artifacts with valid provenance are promoted or deployed.

Why use it?When to use it?How can you leverage it?
Verify the authenticity and integrity of software artifacts using SLSA provenance.When you want to ensure that artifacts originate from a trusted build process before promotion or deployment.Use provenance verification to strengthen software supply chain security and prevent untrusted artifacts from progressing through your delivery pipeline.

Set up Harness GitLab CI/CD​

Before configuring SLSA verification in your GitLab pipeline, set up Harness GitLab CI/CD from your SCS project. The setup guides you through creating or selecting a Harness API key and generates a project-specific YAML configuration with your Harness account ID, organization ID, project ID, and account URL already populated. You can copy this configuration into your GitLab workflow and update the remaining inputs as needed.

Complete the following steps to set up Harness GitLab CI/CD:

  1. Navigate to the Integrations page under the Manage section from the sidebar navigation of your SCS account.
  2. Click the Add Integration button to go to the Configure Integration page.
    Alternatively, you can access this page by clicking Get Started > Get Started from the sidebar navigation of your SCS account.
  3. Scroll down to the GitLab collapsible and click it to expand.
  4. Click the Configure button under Configure GitLab CI/CD in your pipeline to generate SBOM and SLSA, and sign artifacts to open the Configure Integration page, where the Artifact Security feature cards are displayed.
  5. Click the Verify SLSA card to open the SLSA Verification sidepanel.
  6. Click the Go to Key Generation button to create the Harness API key required to configure Harness GitLab CI/CD.
    • Select Using Service Account from the dropdown to create the API key using a service account. For more information, see Service Account API Keys.
    • Select Using Personal Account from the dropdown to create a personal API key. Personal API keys are created at the account level and inherit the permissions assigned to your user account. For more information, see Manage API Keys.
  7. Click Copy in the upper-right corner of the code block to copy the generated GitLab CI/CD configuration, and then paste it into your GitLab workflow file.

Configure SLSA verification in GitLab CI/CD​

After setting up Harness GitLab CI/CD, configure the SLSA Verification component in your GitLab workflow file. Add the required GitLab CI/CD variables to your GitLab project, configure the component inputs, configure the provenance verification settings, and run the pipeline. During pipeline execution, the component verifies the provenance associated with the specified artifact before allowing the pipeline to proceed. For the authoritative list of component inputs and defaults, see the CI/CD Catalog at SCS GitLab Plugins.

Complete the following steps to configure SLSA verification:

  1. Add the required GitLab CI/CD variables
  2. Include the SLSA Verification component
  3. Configure SLSA provenance verification in the workflow
  4. Review the workflow
  5. Run the pipeline

Step 1 - Add the required GitLab CI/CD variables​

Before configuring the SLSA Verification component, add the following variables to your GitLab project. For step-by-step instructions, see Define a CI/CD Variable for a project.

VariableDescriptionRequiredExampleMasked?
HARNESS_API_KEYHarness Personal API Key or Service Account API Key used to authenticate with Harness.Yespat.xxxxxxxxxYes
HARNESS_ACCOUNT_IDHarness account identifier.YesAbCdEf123456No
HARNESS_ORG_IDHarness organization identifier.YesSCS_OrgNo
HARNESS_PROJECT_IDHarness project identifier.YesSCSNo
HARNESS_ACCOUNT_URLHarness account URL.Yeshttps://example.harness.ioNo
note

Masked GitLab CI/CD variables cannot be passed through component inputs. For this reason, the Harness scope variables (HARNESS_ACCOUNT_ID, HARNESS_ORG_ID, HARNESS_PROJECT_ID, and HARNESS_ACCOUNT_URL) must remain unmasked so that they can be wired through the component inputs. HARNESS_API_KEY remains masked and is consumed directly from the job environment, not passed as a component input. These values are included in the generated YAML provided during the Set up Harness GitLab CI/CD workflow.

Step 2 - Include the SLSA Verification component​

Add an scs stage to your GitLab workflow file, or set the stage input on the component to an existing stage. Then, include the Harness SLSA Verification component in your GitLab workflow file.

The following code snippet demonstrates how to add the scs stage and include the SLSA Verification component in your GitLab workflow file. The snippet includes the minimum required component inputs because the component requires the Harness scope variables and the target artifact to run.

stages: [scs]

include:
  - component: gitlab.com/harness-scs/gitlab-plugins/slsa-verification@1.0.0
    inputs:
      HARNESS_ACCOUNT_ID: $HARNESS_ACCOUNT_ID
      HARNESS_ORG_ID: $HARNESS_ORG_ID
      HARNESS_PROJECT_ID: $HARNESS_PROJECT_ID
      HARNESS_ACCOUNT_URL: $HARNESS_ACCOUNT_URL
      TARGET: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

Configure the component using the GitLab CI/CD variables created in the previous step and the following component inputs.

InputDescriptionRequiredDefaultExample
HARNESS_ACCOUNT_IDHarness account ID. Pass a non-masked CI/CD variable reference.YesN/A$HARNESS_ACCOUNT_ID
HARNESS_ORG_IDHarness organization ID. Pass a non-masked CI/CD variable reference.YesN/A$HARNESS_ORG_ID
HARNESS_PROJECT_IDHarness project ID. Pass a non-masked CI/CD variable reference.YesN/A$HARNESS_PROJECT_ID
HARNESS_ACCOUNT_URLHarness base URL with scheme. Pass a non-masked CI/CD variable reference.YesN/A$HARNESS_ACCOUNT_URL
TARGETContainer image reference when SOURCE is container, or artifact file path when SOURCE is local.YesN/A$CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
VERIFYVerifies the SLSA provenance attestation.Nofalsetrue
SOURCEArtifact source. Supported values are container and local.Nocontainerlocal
ARTIFACT_NAMEDisplay name for a local artifact. Applicable when SOURCE is local.NoFile name from TARGETpayment-service
ARTIFACT_VERSIONArtifact version. Applicable when SOURCE is local.NoN/A$CI_COMMIT_SHORT_SHA
stageGitLab pipeline stage in which the component runs.Noscssecurity
job-nameName of the GitLab job created by the component.Noscs-slsa-verificationverify-slsa
note

By default, the component verifies the SLSA provenance associated with a container image. To verify the SLSA provenance associated with a local artifact, set SOURCE to local. When using a local artifact, specify the artifact path in TARGET and provide an ARTIFACT_VERSION.

To verify the SLSA provenance attestation, configure the verification inputs (VERIFY_WITH, OIDC_PROVIDER, FULCIO_URL, KMS_KEY, and VAULT_ADDR) as described in Step 3 - Configure provenance verification.

Override the generated job​

Standard GitLab job keywords, such as needs, before_script, script, after_script, allow_failure, and tags, are not component inputs. To set them, redeclare the generated job (default name scs-slsa-verification, or the value of job-name) in your workflow file. GitLab merges your keys into the generated job.

scs-slsa-verification:
  needs: [build-image]
  tags: [docker, linux]
  before_script:
    - echo "Starting provenance verification"
  after_script:
    - echo "Verification complete"
note

If you are verifying provenance for an image in a private registry that is not the GitLab container registry, provide the registry credentials as masked GitLab CI/CD variables so that the component can access the image.

Step 3 - Configure provenance verification​

Harness supports the following verification methods:

  • Keyless verification – Uses OpenID Connect (OIDC) identities to verify the signed SLSA provenance without managing long-lived signing keys.
  • Key-based verification – Uses a cryptographic key managed through your organization's key management solution.
  • Secret Manager – Uses verification keys stored in a supported secret manager.
note
  • SLSA verification is disabled by default (VERIFY: false). When verification is disabled, the component skips Cosign verification and does not require the VERIFY_WITH, KMS_KEY, or VAULT_ADDR inputs.
  • To verify the signed SLSA provenance, set VERIFY: true. The VERIFY_WITH input specifies the verification method and defaults to secret-manager, which requires KMS_KEY and VAULT_ADDR.

Configure the appropriate verification inputs based on the verification method you want to use.

If you enable SLSA verification, you can configure keyless verification to verify the signed SLSA provenance using an OpenID Connect (OIDC) identity. For GitLab CI/CD, set OIDC_PROVIDER to non-harness. The harness OIDC provider is not supported as of now. Keyless verification requires GitLab 15.7 or later, because it depends on GitLab id_tokens. Configure the following inputs.

InputDescriptionRequired
VERIFY_WITHSpecifies the verification method. Set the value to keyless.Yes
OIDC_PROVIDEROIDC provider used to obtain the verification identity. For GitLab CI/CD, set the value to non-harness.Yes
FULCIO_URLFulcio certificate authority endpoint. Used when OIDC_PROVIDER is non-harness. Defaults to https://fulcio.sigstore.dev.No

Provide the OIDC token to the generated job using id_tokens. The component reads the token from PLUGIN_NON_HARNESS_OIDC_TOKEN.

stages: [scs]
 
include:
  - component: gitlab.com/harness-scs/gitlab-plugins/slsa-verification@1.0.0
    inputs:
      HARNESS_ACCOUNT_ID: $HARNESS_ACCOUNT_ID
      HARNESS_ORG_ID: $HARNESS_ORG_ID
      HARNESS_PROJECT_ID: $HARNESS_PROJECT_ID
      HARNESS_ACCOUNT_URL: $HARNESS_ACCOUNT_URL
      TARGET: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
      VERIFY: true
      VERIFY_WITH: keyless
      OIDC_PROVIDER: non-harness
 
scs-slsa-verification:
  id_tokens:
    PLUGIN_NON_HARNESS_OIDC_TOKEN:
      aud: sigstore

Step 4 - Review the workflow​

After configuring the required GitLab CI/CD variables and component inputs, your GitLab workflow file should resemble the following example. This example verifies the SLSA provenance for a container image in Harness SCS using Cosign with a verification key stored in HashiCorp Vault. The Harness scope variables are wired through inputs, HARNESS_API_KEY remains a masked GitLab CI/CD variable, and the Vault variables (KMS_KEY and VAULT_ADDR) are provided because verification is enabled.

include:
  - component: gitlab.com/harness-scs/gitlab-plugins/slsa-verification@1.0.0
    inputs:
      HARNESS_ACCOUNT_ID: $HARNESS_ACCOUNT_ID
      HARNESS_ORG_ID: $HARNESS_ORG_ID
      HARNESS_PROJECT_ID: $HARNESS_PROJECT_ID
      HARNESS_ACCOUNT_URL: $HARNESS_ACCOUNT_URL
      TARGET: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
      VERIFY: true
      VERIFY_WITH: secret-manager
      KMS_KEY: hashivault://cosign
      VAULT_ADDR: $VAULT_ADDR

Step 5 - Run the pipeline​

Commit and push your changes to trigger the GitLab pipeline. During pipeline execution, the SLSA Verification component verifies the provenance associated with the specified artifact. Based on the verification results, the pipeline determines whether the artifact can proceed to subsequent stages. For more information on running a GitLab pipeline, see Tutorial: Create and run your first GitLab CI/CD pipeline.

After the pipeline completes, open the job execution logs and click the Harness Artifact Details link to view the generated artifact in SCS. For more information on viewing the status of a job and details of the pipeline, see View the status of your pipeline and jobs.

The Artifact Details page displays the SLSA verification results for the artifact. The verification results are also recorded in the Chain of Custody, providing an immutable audit trail of the artifact lifecycle and the associated GitLab CI/CD pipeline execution. For more information on navigating through artifacts, see Artifact Overview.

Example SLSA verification workflow​

Example SLSA verification workflow for a container image

The following example demonstrates how to configure the SLSA Verification component in a GitLab workflow to verify the provenance associated with a container image. The example uses a verification key stored in HashiCorp Vault to validate the provenance before the pipeline proceeds.

stages:
  - build
  - scs
 
build-image:
  stage: build
  image: docker:24.0.5
  services:
    - docker:24.0.5-dind
  script:
    - docker build -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA .
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
 
include:
  - component: gitlab.com/harness-scs/gitlab-plugins/slsa-verification@1.0.0
    inputs:
      stage: scs
      job-name: verify-slsa
      HARNESS_ACCOUNT_ID: $HARNESS_ACCOUNT_ID
      HARNESS_ORG_ID: $HARNESS_ORG_ID
      HARNESS_PROJECT_ID: $HARNESS_PROJECT_ID
      HARNESS_ACCOUNT_URL: $HARNESS_ACCOUNT_URL
 
      TARGET: $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA
 
      VERIFY: true
      VERIFY_WITH: secret-manager
      KMS_KEY: hashivault://cosign
      VAULT_ADDR: $VAULT_ADDR
Example SLSA verification workflow for a local artifact

The following example verifies provenance for a local artifact. It builds the artifact in an earlier job, passes it forward with artifacts, and uses needs so the verification job runs after the artifact is available. When SOURCE is local, TARGET is the artifact file path and ARTIFACT_VERSION is required.

stages:
  - build
  - scs
 
build-artifact:
  stage: build
  script:
    - ./build.sh -o $CI_PROJECT_DIR/target/myapp.jar
  artifacts:
    paths:
      - target/myapp.jar
 
scs-slsa-verification:
  needs: [build-artifact]
 
include:
  - component: gitlab.com/harness-scs/gitlab-plugins/slsa-verification@1.0.0
    inputs:
      HARNESS_ACCOUNT_ID: $HARNESS_ACCOUNT_ID
      HARNESS_ORG_ID: $HARNESS_ORG_ID
      HARNESS_PROJECT_ID: $HARNESS_PROJECT_ID
      HARNESS_ACCOUNT_URL: $HARNESS_ACCOUNT_URL
 
      SOURCE: local
      TARGET: $CI_PROJECT_DIR/target/myapp.jar
      ARTIFACT_VERSION: $CI_COMMIT_SHORT_SHA
      VERIFY: true
      VERIFY_WITH: secret-manager
      KMS_KEY: hashivault://cosign
      VAULT_ADDR: $VAULT_ADDR

Next steps​