This explanation is based on AWS documentation and best practices but is paraphrased, not a literal extract.

The current CI/CD pipeline uses an IAM user with long-lived access keys stored in GitHub Actions. The new requirement is that pipelines must not use long-lived secret keys. Instead, the solution should provide short-lived credentials with minimal operational overhead.

GitHub Actions natively supports integration with cloud providers using OpenID Connect (OIDC). With OIDC, GitHub acts as an identity provider that can issue OIDC tokens to workflows. On the AWS side, IAM supports configuring an OIDC identity provider and roles that can be assumed by principals presenting valid OIDC tokens through the sts:AssumeRoleWithWebIdentity API. This pattern enables short-lived, automatically rotated credentials for CI/CD jobs without storing long-lived secrets.

In the correct solution (option B), you configure an IAM OIDC identity provider for GitHub in the AWS account. You then create a new IAM role with a trust policy that allows the Github OIDC provider to call sts:AssumeRoleWithWebIdentity, with conditions that restrict which repositories or workflows can assume the role. The existing IAM policy that grants deployment permissions is attached to that role. In GitHub Actions, you update the pipeline configuration to request an OIDC token and assume the IAM role at runtime. Each workflow run receives short-lived credentials without storing static keys, and AWS automatically handles the token verification and temporary credential issuance. This approach is the AWS-recommended pattern for integrating GitHub Actions with AWS without long-lived secrets and has low operational overhead once configured.

Option A uses SAML 2.0, which is typically used for enterprise single sign-on for users, not for GitHub Actions workflows. GitHub does not natively use SAML to obtain AWS credentials for CI/CD pipelines in the same streamlined way as OIDC, and implementing a SAML-based integration would add unnecessary complexity.

Option C introduces Amazon Cognito as an indirection layer. Although Cognito can federate with external identity providers, including social providers, using it as an intermediary to obtain temporary AWS credentials for a machine-to-machine CI/CD pipeline is not necessary when IAM OIDC federation with GitHub is directly supported. This adds additional configuration and operational overhead.

Option D uses IAM Roles Anywhere with client certificates from AWS Private CA. Roles Anywhere is designed for workloads running outside AWS that need to assume IAM roles using X.509 certificates instead of access keys. While technically possible, it requires managing private certificates, trust anchors, and a credential helper tool, which is more complex and operationally heavier than the direct OIDC integration specifically designed for GitHub Actions.

Therefore, configuring an IAM OIDC identity provider for GitHub and creating an IAM role to be assumed via sts:AssumeRoleWithWebIdentity (option B) meets the requirement to replace long-lived secret keys with short-lived credentials with the least operational overhead.