Asked 1 month ago by MeteoricRover993
How can I authenticate to Azure Key Vault without creating a circular dependency on certificates?
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We have several internal APIs that now need to be exposed externally, and I’ve been tasked with securing them. Our current approach is based on Microsoft’s recommendation to use certificates for authentication. Internally, we distribute certificates via our load-balanced servers using our own CAs and authenticate applications through Azure app registration.
I’m now facing a challenge with securely managing and cycling these certificates. For example, one of our externally exposed APIs is used by a mobile app, and I can’t embed the certificate in the mobile package due to security and renewal concerns.
My potential solution involves using Azure Key Vault to secure and cycle the certificates. However, I’m unsure how to authenticate to Key Vault without adding another layer of certificates that would also require secure management and rotation. I’ve seen suggestions to use an intermediary app service, but then that service still needs to authenticate (via a client secret or certificate), which doesn’t solve the problem.
How can I authenticate to Azure Key Vault without introducing a circular dependency where I need to secure and cycle additional certificates?
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2 Answers
Answer by 
TychoAI Agent • 1 month ago
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Below is one approach recommended by Microsoft that avoids the circular dependency of needing a certificate to access Key Vault while having to store and cycle that certificate.
Use Managed Identities or a Secure Backend Service
Rather than embedding or distributing certificates in your mobile app, you can delegate Key Vault access to a secure backend that uses one of these approaches:
-
Managed Identities for Azure Resources:
If your backend runs in Azure (for example, on App Service, Azure Functions, or Virtual Machines), you can enable a managed identity (system-assigned or user-assigned). Managed identities let your service obtain an Azure AD token for Key Vault without storing any credentials or certificates in your application code. This removes the need for a certificate stored outside of Key Vault, because Azure automatically manages the lifecycle of that identity’s credentials. -
Secure Backend API as an Intermediary:
For clients like mobile apps that cannot safely host sensitive credentials, the best practice is to have them call your secure backend service. This backend service is the only component that communicates with Key Vault (using managed identities or other secure methods such as a client secret kept in a secure location). The mobile app never directly accesses Key Vault.
Why This Works
Using managed identities or a backend intermediary means your mobile app doesn’t have to be entrusted with any long-lived secrets or certificates. The authentication flow is:
- The mobile app authenticates to your backend through secure channels (using standard approaches like OAuth 2.0).
- The backend, leveraging its managed identity, obtains an Azure AD token automatically for Key Vault access.
- The backend accesses Key Vault to retrieve or manage the certificates/secrets needed for your internal APIs.
- The backend then performs operations on behalf of the mobile app.
This separation minimizes the risk of certificate leakage and simplifies certificate cycling since the lifecycle of the certificate used to access Key Vault is managed by Azure.
Summary
- Avoid embedding certificates in distributed apps like mobile clients.
- Use a backend service (API gateway, web API, etc.) to abstract Key Vault access.
- Leverage managed identities in Azure so that credential management is handled by the platform, relieving you from having to secure and rotate additional certificates.
By following these practices, you adhere to Microsoft’s recommendations for certificate authentication while keeping your application secure and reducing operational overhead for certificate rotation.
Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?
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Answer by StarPathfinder823 • 1 month ago
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Note: Managed Identity can be used to authenticate services (like APIs or applications) to Azure Key Vault. Managed Identity allows you to avoid managing certificates or secrets for authentication.
- Managed identity will automatically authenticate to Azure resources (like Key Vault) without needing any additional credentials or certificates.
- You can enable the managed identity in Azure App service and call Azure key vault. Refer this SO Thread by me.
Enable Managed Identity in your Azure App Service and grant it Get/List permissions in Key Vault. Use the Azure SDK to authenticate and access certificates in your app.
CSHARPvar credential = new DefaultAzureCredential(); var client = new SecretClient(new Uri("https://<your-keyvault-name>.vault.azure.net/"), credential); KeyVaultCertificate certificate = client.GetCertificate("<certificate-name>");
Otherwise, you can make use of app registration and make use of client secret:
For sample, I generated access token:
https://login.microsoftonline.com/TenantID/oauth2/v2.0/token
client_id: ClientID
client_secret: XXX
scope: https://vault.azure.net/.default
grant_type: client_credentials
By using the above access token, you can call and access Key vault.
Reference:
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