How do you use a managed identity as a federated credential for a Microsoft Entra app registration?

How managed identity becomes a federated credential

The core idea is that Microsoft Entra accepts a token from the managed identity as an external proof of identity, then exchanges or trusts that proof for access to the app registration. That removes the need for a stored client secret and makes the trust relationship explicit, scoped, and revocable. The configuration matters more than the label: you are defining which issuer, subject, and audience are allowed to act for the app.

This is why the same pattern used for other forms of workload identity federation also applies here. The managed identity is not “logging in” in the human sense, it is presenting a token that Entra can verify against the federated credential definition on the app registration.

In practice, the most important design choice is the trust boundary. Keep the federated credential narrow enough that the managed identity can only obtain the app’s intended token, and do not broaden the subject or audience just to reduce setup friction. If the trust is too broad, the app registration can become a reusable bridge for more access than you meant to grant.

What you must verify before relying on the trust

First confirm that the managed identity you want to trust is the one actually issuing the token path in production. Microsoft Entra app registrations can accept multiple credentials and multiple trust paths, so the configuration should be checked end to end rather than assumed from the portal state. The app should receive tokens only when the expected managed identity is the caller, and only for the intended resource audience.

It is also worth checking whether the app registration still has any old secrets, certificates, or broader service principal permissions attached. If those remain in place, the federated credential may work correctly while the overall application trust remains wider than necessary. The goal is not just to add federation, but to make federation the only live path that matters.

Where you want a broader implementation reference for the surrounding Azure pattern, the Cloud Workload Identity Guide is useful because it places managed identities alongside other keyless workload trust models such as service principals and workload identity federation.

How to operationalise it without creating hidden privilege

Once the federated credential is in place, scope access at the app registration and resource layer, not just at the token issuance layer. A clean configuration still fails if the app has permissions that are broader than the workload needs, or if the managed identity can be reused by another workload with a different security profile.

That is why the Azure RBAC and Service Principals Guide is relevant here: the app registration trust and the downstream authorization model have to line up. Use least privilege on the resource side, and treat the federated credential as an authentication path, not as a substitute for authorization design.

If you are comparing this pattern with other Entra workload identity options, the Workload Identity Federation Guide helps you distinguish claim scoping, token exchange, and trust policy decisions from the separate problem of what the app is allowed to do after authentication succeeds.

Risk and Threat Considerations

Federated credentials reduce secret sprawl, but they do not remove trust abuse risk. If the managed identity is over-scoped, or if the app registration accepts a token shape that is too permissive, an attacker who gains control of the workload can turn that trust into durable access without ever stealing a long-lived secret.

Failure mechanism: A compromised workload, mis-scoped identity, or overly broad federated credential lets an unauthorized caller mint a valid token for the app registration and reuse the app’s permissions against downstream resources.

Impact: The result can be unauthorized access, lateral movement through Azure resources, and a much harder incident response because the abuse looks like legitimate token exchange rather than obvious secret theft.

Practitioner Guidance

What to verify: Confirm the managed identity, issuer, subject, and audience all match the exact workload path you intended, and test that no other identity can obtain the same token. If the app can authenticate from more than one path, document why each path exists.

What to prioritise: Remove obsolete secrets, certificates, and unused permissions once federation is live. The safest deployment is the one where the federated credential is not just enabled, but is the only credential path left standing for that app.

Practitioner takeaway: Treat managed identity federation as a replacement for secret-based authentication, not as a shortcut around authorization design. The security gain comes from narrowing trust, not merely from changing the credential type.

Related resources from NHI Mgmt Group

• How do you require a managed device for MFA registration with Microsoft Entra Conditional Access?
• How do you deactivate a compromised app registration in Microsoft Entra ID?
• How do you use group managed service accounts in Microsoft Entra Domain Services?
• How do you assign a managed identity to an application role in Microsoft Entra ID?