How to Update Azure Managed Application Deny Assignments Without Redeployment

INTRODUCTION

While working on a B2B FinTech SaaS platform distributed via the Azure Marketplace, our engineering team rolled out a crucial security auditing feature. The architecture relied on Azure Managed Applications (AMA) deployed directly into our enterprise clients’ subscriptions. To support the new auditing feature, we deployed an Azure Function App inside the managed environment that needed to scan and read metadata from an Azure Key Vault.

The rollout went perfectly in our internal testing environments. However, when we pushed the update to existing customer environments, the Function App immediately failed. The issue? A strict Azure Deny Assignment on the managed resource group blocked the Function App from executing the required Key Vault metadata read action.

In a multi-tenant or distributed enterprise ecosystem, configuration lock-ins like this can halt feature rollouts entirely. This challenge inspired this article, detailing how we safely updated deny assignment exclusions for existing customer managed resource groups without forcing them to tear down and redeploy their mission-critical infrastructure.

PROBLEM CONTEXT

Azure Managed Applications are an excellent mechanism for Independent Software Vendors (ISVs) to deliver software into a customer’s Azure environment while retaining administrative control. When a customer provisions the application, Azure creates a Managed Resource Group (MRG). To prevent the customer from accidentally modifying or deleting the managed resources, Azure automatically applies a Deny Assignment to the MRG.

In our FinTech use case, the MRG contained various compute resources, databases, and an Azure Key Vault. Our new Function App needed to verify secret rotation compliance, which required a specific RBAC action:

Microsoft.KeyVault/vaults/secrets/readMetadata/action

Because this action was not explicitly excluded in the original Deny Assignment, Azure blocked the Function App from reading the metadata, despite the Function App having the correct Role-Based Access Control (RBAC) role assigned.

WHAT WENT WRONG

The symptoms surfaced immediately after our automated deployment pipelines pushed the new Function App code to existing customers. Our telemetry systems flooded with AuthorizationFailed errors.

Our initial diagnostic steps confirmed that the Managed Identity attached to the Function App had the correct Key Vault Reader roles. However, Azure’s authorization evaluation logic explicitly prioritizes Deny Assignments over Allow assignments. Because the Deny Assignment placed on the MRG inherited down to the Key Vault, our RBAC permissions were effectively nullified.

We quickly adjusted the technical configuration of our Managed Application package in the Azure Partner Center. By adding the read metadata action to the deny assignment exclusions in the ARM template, we ensured all new customers received the correct permissions. But this left a critical architectural oversight: modifying the marketplace configuration did not automatically propagate the new deny assignment rules to existing customer deployments.

HOW WE APPROACHED THE SOLUTION

Tearing down and redeploying the Managed Application for existing clients was out of the question. This was a FinTech platform; redeployment meant unacceptable downtime, potential data migration risks, and severe friction for our enterprise clients.

We needed an in-place upgrade strategy. When organizations hire azure developers for enterprise modernization, one of the primary expectations is the ability to handle complex lifecycle management without disrupting production services.

We investigated the lifecycle hooks of Azure Managed Applications. We discovered that the Deny Assignment on an MRG is evaluated and applied by the Azure Resource Manager (ARM) during the provisioning state of the Managed Application resource itself. If we could trigger an update operation on the existing Managed Application instance—pointing it to the newly published marketplace version or an updated ARM definition—Azure’s control plane would reconcile the state, reapplying the Deny Assignment with the new exclusions while leaving the underlying data and compute resources intact.

FINAL IMPLEMENTATION

Our solution required a two-step approach: updating the application definition in the Azure Marketplace and then executing an in-place update for existing tenants.

1. Updating the Application Definition

First, we updated our mainTemplate.json and createUiDefinition.json to ensure the publisher authorizations included the necessary exclusions. In the authorization configuration, we explicitly added the Key Vault action to the exclusions list.

{
  "type": "Microsoft.Solutions/applications",
  "apiVersion": "2021-04-01",
  "name": "[parameters('applicationName')]",
  "location": "[resourceGroup().location]",
  "kind": "ServiceCatalog",
  "properties": {
    "managedResourceGroupId": "[variables('managedGroupId')]",
    "applicationDefinitionId": "[variables('appDefinitionId')]",
    "parameters": { ... },
    "authorizations": [
      {
        "principalId": "[variables('publisherPrincipalId')]",
        "roleDefinitionId": "[variables('contributorRoleId')]"
      }
    ],
    "manageAuthorizationPolicy": {
      "excludedActions": [
        "Microsoft.KeyVault/vaults/secrets/readMetadata/action"
      ]
    }
  }
}

We published this updated package as a new minor version in the Azure Partner Center.

2. Triggering the In-Place Update

Once the new version was live, we utilized a script to iterate through our existing client deployments and trigger an update. Because the Managed Application resource resides in the customer’s subscription, we coordinated with our clients to run a seamless update command, or utilized our delegated access where permitted.

The update was triggered using the Azure CLI, explicitly pointing the existing application to the new version:

az managedapp update 
  --name "fintech-managed-app" 
  --resource-group "customer-rg" 
  --application-definition-id "/subscriptions/{sub-id}/resourceGroups/{rg}/providers/Microsoft.Solutions/applicationDefinitions/{new-def-id}"

Validation: The ARM fabric initiated a PUT request against the Managed Application. It evaluated the new template, recognized the updated manageAuthorizationPolicy, and successfully modified the Deny Assignment on the Managed Resource Group. The operation completed in minutes, no resources were recreated, and our Function App instantly began reading the Key Vault metadata.

LESSONS FOR ENGINEERING TEAMS

When you hire software developer teams to build scalable cloud architectures, they must look beyond day-one deployment and design for day-two operations. Here are the key takeaways from this incident:

• Design Deny Exclusions Early: Anticipate the actions your internal operational tools and managed identities will need. Key Vault access, metrics emission, and diagnostic log configurations are commonly blocked by default Deny Assignments.
• Understand Authorization Hierarchy: Always remember that in Azure, Deny Assignments trump explicit Allow RBAC assignments. If a service has the right role but still fails, check the MRG or Blueprint Deny Assignments.
• Master In-Place Upgrades: Avoid architectural patterns that require teardowns for minor configuration changes. Understand how ARM processes PUT requests for state reconciliation.
• Version Control Marketplace Offers: Keep strict versioning for your Azure Managed Application packages. This allows you to roll out configuration changes like Deny Assignment exclusions incrementally.
• Automate Tenant Updates: When you hire cloud developers for managed applications, ensure they build automation scripts for tenant upgrades early in the project lifecycle to seamlessly push non-destructive updates.

WRAP UP

Managing strict security boundaries in distributed cloud environments requires a deep understanding of resource management lifecycles. By leveraging the state-reconciliation behavior of Azure Resource Manager, we were able to update the Deny Assignment exclusions safely, unblocking our new security feature without any disruption to our existing FinTech customers. If your organization is facing complex cloud architecture challenges or needs to scale a robust engineering team, contact us to learn how our experts can help.

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