feat: add Application ID URI parameter and update policies for JWT audience validation

Author: Justrebl

labs/mcp-prm-oauth/main.bicep

@@ -234,6 +234,8 @@ module mcpEntraAppModule 'src/bicep/identity/mcp-entra-app.bicep' = if (empty(mc
     tenantId: subscription().tenantId
     userAssignedIdentityPrincipleId: managedIdentityModule.outputs.identityPrincipalId
     webAppName: mcpServerContainerApp.name
+    // Application ID URI == PRM resource == JWT audience (all resolve to https://<apim>.azure-api.net/<mcpPrmPath>)
+    applicationIdUri: '${apimModule.outputs.gatewayUrl}/${mcpPrmPath}'
   }
 }
 

labs/mcp-prm-oauth/src/bicep/apim-mcp/mcp-api.policy.xml

@@ -9,7 +9,9 @@
         <!-- Validate Azure AD JWT Token -->
         <validate-azure-ad-token tenant-id="{{McpTenantId}}" failed-validation-httpcode="401" failed-validation-error-message="Unauthorized">
             <audiences>
+                <!-- v2 tokens carry the appId (GUID) as aud; the Application ID URI is accepted too. -->
                 <audience>{{McpClientId}}</audience>
+                <audience>{{APIMGatewayURL}}/{{McpApiPath}}</audience>
             </audiences>
         </validate-azure-ad-token>
     </inbound>

labs/mcp-prm-oauth/src/bicep/apim-mcp/mcp-prm.policy.xml

@@ -25,7 +25,7 @@
                         "header"
                     },
                     scopes_supported = new[] {
-                        "{{McpClientId}}/user_impersonate"
+                        "{{APIMGatewayURL}}/{{McpApiPath}}/user_impersonate"
                     }
                 });
             }</set-body>

labs/mcp-prm-oauth/src/bicep/identity/mcp-entra-app.bicep

@@ -15,6 +15,9 @@ param userAssignedIdentityPrincipleId string
 @description('The container app name for callback URL configuration')
 param webAppName string
 
+@description('The Application ID URI to expose (must match the PRM resource and the JWT audience). Example: https://<apim>.azure-api.net/mcp')
+param applicationIdUri string
+
 var loginEndpoint = environment().authentication.loginEndpoint
 var issuer = '${loginEndpoint}${tenantId}/v2.0'
 
@@ -26,6 +29,10 @@ resource containerApp 'Microsoft.App/containerApps@2023-11-02-preview' existing
 resource mcpEntraApp 'Microsoft.Graph/applications@v1.0' = {
   displayName: mcpAppDisplayName
   uniqueName: mcpAppUniqueName
+  // Application ID URI. Aligns with the PRM 'resource' and the validate-jwt audience.
+  identifierUris: [
+    applicationIdUri
+  ]
   api: {
     oauth2PermissionScopes: [
       {
@@ -65,6 +72,14 @@ resource mcpEntraApp 'Microsoft.Graph/applications@v1.0' = {
       'https://${containerApp.properties.configuration.ingress.fqdn}/auth/callback'
     ]
   }
+  // Public client (Authorization Code + PKCE, no client secret) for MCP Inspector.
+  // Registering these as public-client (not SPA) redirect URIs avoids AADSTS9002327.
+  publicClient: {
+    redirectUris: [
+      'http://localhost:6274/oauth/callback'
+      'http://localhost:6274/oauth/callback/debug'
+    ]
+  }
 
   resource fic 'federatedIdentityCredentials@v1.0' = {
     name: '${mcpEntraApp.uniqueName}/msiAsFic'