Azure App Service, Private Endpoint, and Application Gateway/WAF

In this post, I will share how to configure an Azure Web App (or App Service) with Private Endpoint, and securely share that HTTP/S service using the Azure Application Gateway, with the optional Web Application Firewall (WAF) feature. Whew! That’s lots of feature names!

Background

Azure Application (App) Services or Web Apps allows you to create and host a web site or web application in Azure without (directly) dealing with virtual machines. This platform service makes HTTP/S services easy. By default, App Services are shared behind a public/ & shared frontend (actually, load-balanced frontends) with public IP addresses.

Earlier this year, Microsoft released Private Link, a service that enables an Azure platform resource (or service shared using a Standard Tier Load Balancer) to be connected to a virtual network subnet. The resource is referred to as the linked resource. The linked resource connects to the subnet using a Private Endpoint. There is a Private Endpoint resource and a special NIC; it’s this NIC that shares the resource with a private IP address, obtained from the address space of the subnet. You can then connect to the linked resource using the Private Endpoint IPv4 address. Note that the Private Endpoint can connect to many different “subresources” or services (referred to as serviceGroup in ARM) that the linked resource can offer. For example, a storage account has serviceGroups such as file, blob, and web.

Notes: Private Link is generally available. Private Endpoint for App Services is still in preview. App Services Premium V2 is required for Private Endpoint.

The Application Gateway allows you to share/load balance a HTTP/S service at the application layer with external (virtual network, WAN, Internet) clients. This reverse proxy also offers an optional Web Application Firewall (WAF), at extra cost, to protect the HTTP/S service with the OWASP rule set and bot protection. With the Standard Tier of DDoS protection enabled on the Application Gateway virtual network, the WAF extends this protection to Layer-7.

Design Goal

The goal of this design is to ensure that all HTTP/S (HTTPS in this example) traffic to the Web App must:

  • Go through the WAF.
  • Reverse proxy to the App Service via the Private Endpoint private IPv4 address only.

The design will result in:

  • Layer-4 protection by an NSG associated with the WAF subnet. NSG Traffic Analytics will send the data to Log Analytics (and optionally Azure Sentinel for SIEM) for logging, classification, and reporting.
  • Layer-7 protection by the WAF. If the Standard Tier of DD0S protection is enabled, then the protection will be at Layer-4 (Application Gateway Public IP Address) and Layer-7 (WAF). Logging data will be sent to Log Analytics (and optionally Azure Sentinel for SIEM) for logging and reporting.
  • Connections directly to the web app will fail with a “HTTP Error 403 – Forbidden” error.

Note: If you want to completely prevent TCP connections to the web app then you need to consider App Service Environment/Isolated Tier or a different Azure platform/IaaS solution.

Design

Here is the design – you will want to see the original image:

There are a number of elements to the design:

Private DNS Zone

You must be able to resolve the FQDNs of your services using the per-resource type domain names. App Services use a private DNS zone called privatelink.azurewebsites.net. There are hacks to get this to work. The best solution is to create a central Azure Private DNS Zone called privatelink.azurewebsites.net.

If you have DNS servers configured on your virtual network(s), associate the Private DNS Zone with your DNS servers’ virtual network(s). Create a conditional forwarder on the DNS servers to forward all requests to privatelink.azurewebsites.net to 168.63.129.16 (https://docs.microsoft.com/en-us/azure/virtual-network/what-is-ip-address-168-63-129-16). This will result in:

  1. A network client sending a DNS resolution request to your DNS servers for *.privatelink.azurewebsites.net.
  2. The DNS servers forwarding the requests for *.privatelink.azurewebsites.net to 168.63.129.16.
  3. The Azure Private DNS Zone will receive the forwarded request and respond to the DNS servers.
  4. The DNS servers will respond to the client with the answer.

App Service

As stated before the App Service must be hosted on a Premium v2 tier App Service Plan. In my example, the app is called myapp with a default URI of https://myapp.azurewebsites.net. A virtual network access rule is added to the App Service to permit access from the subnet of the Application Gateway. Don’t forget to figure out what to do with the SCM URI for DevOps/GitHub integration.

Private Endpoint

A Private Endpoint was added to the App Service. The service/subresource/serviceGroup is sites. Automatically, Microsoft will update their DNS to modify the name resolution of myapp.azurewebsites.net to resolve to myapp.privatelink.azurewebsites.net. In the above example, the NIC for the Private Endpoint gets an IP address of 10.0.64.68 from the AppSubnet that the App Service is now connected to.

Add an A record to the Private DNS Zone for the App Service, resolving to the IPv4 address of the Private Endpoint NIC. In my case, myapp.privatelink.azurewebsites.net will resolve to 10.0.64.68. This in turn means that myapp.azurewebsites.net > myapp.privatelink.azurewebsites.net > 10.0.64.68.

Application Gateway/WAF

  1. Add a new Backend Pool with the IPv4 address of the Private Endpoint NIC, which is 10.0.64.68 in my example.
  2. Create a multisite HTTPS:443 listener for the required public URI, which will be myapp.joeelway.com in my example, adding the certificate, ideally from an Azure Key Vault. Use the public IP address (in my example) as the frontend.
  3. Set up a Custom Probe to test https://myapp.azurewebsites.net:443 (using the hostname option) with acceptable responses of 200-399.
  4. Create an HTTP Setting (the reverse proxy) to forward traffic to https://myapp.azurewebsites.net:443 (using the hostname option) using a well-known certificate (accepting the default cert of the App Service) for end-to-end encryption.
  5. Bind all of the above together with a routing rule.

Public DNS

Now you need to get traffic for https://myapp.joeelway.com to go to the (public, in my example) frontend IP address of the Application Gateway/WAF. There are lots of ways to do this, including Azure Front Door, Azure Traffic Manager, and third-party solutions. The easy way is to add an A record to your public DNS zone (joeelway.com, in my example) that resolves to the public IP address of the Application Gateway.

The Result

  1. A client browses https://myapp.joeelway.com.
  2. The client name resolution goes to public DNS which resolves myapp.joeelway.com to the public IP address of the Application Gateway.
  3. The client connects to the Application Gateway, requesting https://myapp.joeelway.com.
  4. The Listener on the Application Gateway receives the connection.
    • Any WAF functionality inspects and accepts/rejects the connection request.
  5. The Routing Rule in the Application Gateway associates the request to https://myapp.joeelway.com with the HTTP Setting and Custom Probe for https://myapp.azurewebsites.net.
  6. The Application Gateway routes the request for https://myapp.joeelway.com to https://myapp.azurewebsites.net at the IPv4 address of the Private Endpoint (documented in the Application Gateway Backend Pool).
  7. The App Service receives and accepts the request for https://myapp.azurewebsites.net and responds to the Application Gateway.
  8. The Application Gateway reverse-proxies the response to the client.

For Good Measure

If you really want to secure things:

  • Deploy the Application Gateway as WAFv2 and store SSL certs in a Key Vault with limited Access Policies
  • The NSG on the WAF subnet must be configured correctly and only permit the minimum traffic to the WAF.
  • All resources will send all logs to Log Analytics.
  • Azure Sentinel is associated with the Log Analytics workspace.
  • Azure Security Center Standard Tier is enabled on the subscription and the Log Analytics Workspace.
  • If you can justify the cost, DDoS Standard Tier is enabled on the virtual network with the public IP address(es).

And that’s just the beginning 🙂

Rethinking Firewall Management With Azure Firewall Manager

Microsoft has just announced the general availability a feature that I’ve been waiting for since I first learned about it last Autumn, called Azure Firewall Manager. Azure Firewall Manager allows you to centrally manage one or more Azure Firewall instances through a central, policy-driven, user interface. And it’s those policies, Azure Firewall Policies, that made me re-think Azure Firewall management a few months ago when I was writing my Cloud Mechanix course (running next ONLINE on July 30th) “Securing Azure Services & Data Through Azure Networking”.

Azure Firewall Policy

This is a new resource type that is generally available today. Azure Firewall Policy outsources the configuration and management of the firewall to a policy resource; that means that the usual settings in the Azure Firewall for things like rules and Threat Intelligence move from the firewall resource to a policy when a policy is associated with the firewall.

Policies can be created in a hierarchy. You can create a parent/global policy that will contain configurations and rules that will apply to all/a number of firewall instances. Then you create a child policy that inherits from the parent; note that rules changes in the parent instantly appear in the child. The child is associated with a firewall and applies configurations/rules from the parent policy and the child policy instantly to the firewall.

Problem

I’ve deployed and configured multiple customers where we have virtual data centers (VDCs, which are governed & secured hub and spoke architectures) across multiple regions. Creating rules configurations to allow flows from a spoke/service in one region to another spoke/service in another region is a royal pain in the tushie. Here’s the network flow (as I documented with routing here):

  1. Source device
  2. Outbound NSG rules in source spoke
  3. Firewall in source hub
  4. Firewall in destination hub
  5. Inbound NSG rules at destination spoke
  6. Destination device

There are potentially 4 sets of rules to configure for a simple service running on a single protocol/port. Today I configured Microsoft Identity Management for this scenario and there were dozens of protocol/port combinations across three spokes. The work took hours to complete – which I did in code and it provided a working result for the identity consulting team.

I minimise the work by controlling outbound flows in the local hub firewall, not in the NSG. So the NSGs do not control outbound flows at all. I could allow all via the firewall, even to other private networks, but that goes against the idea of compartmentalisation or micro-segmentation to combat modern network threats – so I need to configure both firewalls for a flow.

Solution

Re-think the firewall for a moment. Imagine you had one virtual firewall that spanned all of your Azure regional deployments. You can control all global flows with one configuration in that global virtual firewall. The global virtual firewall has instances in each Azure region. Any local flows can be configured just in that instance. That’s what Firewall Policy allows.

  • Parent Policy: Place all your global configurations in here. Some configurations will be company-wide, such as Threat Intelligence. Some rules, like allowing access to Microsoft URIs or Azure services (service tags) will be global too. And this is where you put the rules to allow flows between one regional deployment and another. This global management takes all your local Azure Firewall resources and treats them as a single security service.
  • Child Policies: A child policy will be created for each Azure Firewall instance. This policy will inherit the above from the parent applying the global configuration. Local rules, to allow north-south access to/from local services (Internet or on-prem) or east-west (spoke-to-spoke in the same regional deployment) will be configured here. RBAC can be enabled to allow local network admins to do their own thing, but unable to undo what the parent has done.

I haven’t had a chance to test Azure Firewall Policy out yet since the GA announcement, but I’m hoping that the third tier in rules (Rules Groups) made it from preview to GA. I do have groupings of rules collections based on buckets of priorities. This organisation would be awesome in my vision of Azure Firewall management.

Speaking Today At Global Azure Virtual (ONLINE)

I am presenting at 14:00 UK/Ireland, 3PM central Europe, 9am Eastern US in the Global Azure virtual/online Bootcamp. You can find the link to the session here on Day 3. Here is the session information that is missing from the event site:

Trust No-One Architecture For Services And Data

Security is always one of the top 3 fears of Cloud customers. In The Cloud, the customer is responsible for their network security design and operation. This session will walk you through the components of Azure network security, and how to architect a secure network for Azure virtual machines or platform services, including VNets, network security groups, routing tables, Private Link, VNet peering, web application gateway, DDoS protection, and firewall appliances.

Free Online Training – Azure Network Security

On June 19th, I will be teaching a FREE online class called Securing Azure Services & Data Through Azure Networking.

I’ve run a number of Cloud Mechanix training classes and I’ve had several requests asking if I would ever consider doing something online because I wasn’t doing the classes outside of Europe. Well … here’s your opportunity. Thanks to the kind folks at European Cloud Conference, I will be doing a 1-day training course online and for free for 20 lucky attendees.

The class, relevant to PaaS and IaaS, takes the best practices from Microsoft for securing services and data in Microsoft Azure, and teaches them based on real-world experience. I’ve been designing and implementing this stuff for enterprises and have learned a lot. The class contains stuff that people who live only in labs will not know … and sadly, based on my googling/reading, a lot of bloggers & copy/pasters fall into that bucket. I’ve learned that the basics of Azure virtual networking must be thoroughly understood before you can even attempt security. So I teach that stuff – don’t assume that you know this stuff already because I know that few really do. Then I move into the fun stuff, like firewalls, WAFs, Private Link/Private Endpoint, and more. The delivery platform will allow an interactive class – this will not be a webinar – I’ve been talking to different people to get advice on choosing the best platform for delivering this class.  I’ve some testing to do, but I think I’m set.

Here’s the class description:

Security is always number 1 or 2 in any survey on the fears of cloud computing. Networking in The Cloud is very different from traditional physical networking … but in some ways, it is quite similar. The goal of this workshop is to teach you how to secure your services and data in Microsoft Azure using techniques and designs that are advocated by Microsoft Azure. Don’t fall into the trap of thinking that networking means just virtual machines; Azure networking plays a big (and getting bigger) role in offering security and compliance with platform and data services in The Cloud.

This online class takes you all the way back to the basics of Azure networking so you really understand the “wiring” of a secure network in the cloud. Only with that understanding do you understand that small is big. The topics covered in this class will secure small/mid businesses, platform deployments that require regulatory compliance, and large enterprises:

  • The Microsoft global network
  • Availability & SLA
  • Virtual network basics
  • Virtual network adapters
  • Peering
  • Service endpoints
  • Public IP Addresses
  • VNet gateways: VPN & ExpressRoute
  • Network Security Groups
  • Application Firewall
  • Route Tables
  • Platform services & data
  • Private Link & Private Endpoint
  • Third-Party Firewalls
  • Azure Firewall
  • Monitoring
  • Troubleshooting
  • Security management
  • Micro-Segmentation
  • Architectures

Level: 400

Topic: Security

Category: IT Professionals

Those of you who have seen the 1-hour (and I rarely stuck to that time limit) conference version of this class will know what to expect. An older version of the session scored 99% at NIC 2020 in Oslo in February with a room packed to capacity. Now imagine that class where I had enough time to barely mention things and give me a full day to share my experience … that’s what we’re talking about here!

This class is one of 4 classes being promoted by the European Cloud Conference:

If you’re serious about participating, register your interest and a lucky few will be selected to join the classes.

I’m Presenting Two Sessions At NIC 20/20 Vision in Oslo

I will be presenting two Azure sessions at the (NICCONF) NIC 20/20 Vision conference in Oslo on February 6th.

The content I’m presenting on is inspired by the work I have been doing with Innofactor Norway for customers in Norway. So it will be kind of cool to stand (once again) on a stage in Oslo and share what I’ve learned. I have two sessions on the afternoon of the 6th.

Secure Azure Network Architecture

Azure networking & security has become my focus area. I enjoy the organic nature of how Azure’s software-defined networking functions. I enjoy the scale, the possibilities, and the variety of options. And most of all, I appreciate how the near-universally overlooked fundamentals play a bigger role in network security than people realise. It’s a huge area to cover, but I will do my best in the hour that I have:

This session will walk you through the components of Azure network security, and how to architect a secure network for Azure virtual machines or platform services, including VNets, network security groups, routing tables, VNet peering, web application gateway, DDoS protection, and firewall appliances.

Auditing Azure – Compliance, Oversight, Governance, and Protection

An important part of governance is recording what is going on in Azure and being able to retain, query, and report on that data. This is an area I had a cool solution for this time last year, but Microsoft blew that up. Recently I revisited this space and found cool new things that I could do. And in preparing for this session, I found more stuff that I could talk about. I’ve enjoyed preparing this session and it has contributed back to my work. This session is late in the day for most Norwegians, but I hope that attendees stick around.

Auditing isn’t the most glamorous subject, but in a self-service environment, it becomes important to protect assets, the company, and even your job. In this session, you’ll learn how Azure provides auditing functionality that you can query, report on, and store securely for as long as you need it in cost-efficient ways.

Hopefully, I will see some of you there at the event!

Back Teaching – Implementing Secure Azure Networks

After a quiet 2019, I am getting back into Azure training starting in March in Brussels, Belgium, with a new hands-on course called Implementing Secure Azure Networks.

2019 was a year of (good) upheaval. I started a new job with big responsibilities and a learning curve. Family-wise, we had a lot of good things going on. So I decided to put our (my wife and I) Cloud Mechanix training on the shelf for a while. All last year, I’ve been putting a lot of cool Azure networking & security things into practice with larger enterprises so I’ve been learning … new things, good practices, what works, what doesn’t, and so on. That put the seed into my head for the next class that I would write. Then along came Workshop Summit and asked if I would like to submit a 1-day practical training course. So I did, and they accepted.

The Course

Security is always number 1 or 2 in any survey on the fears of cloud computing. Networking in The Cloud is very different to traditional physical networking … but in some ways it is quite similar. The goals of this workshop are:

  • To teach you the fundamentals, the theory, of how Azure networking functions so you can understand the practical design and application
  • Do hands-on deployments of secure networks

As a result, this workshop takes you all the way back to the basics of Azure networking so you really understand the “wiring” of a secure network in the cloud. Only with that understanding do you understand that small is big. The topics covered in this class will secure small/mid businesses, platform deployments that require regulatory compliance, and large enterprises:

  • The Microsoft global network
  • Availability & SLA
  • Virtual network basics
  • Virtual network adapters
  • Peering
  • Service endpoints
  • Private Link & Private Endpoints
  • Public IP Addresses
  • VNet gateways: VPN & ExpressRoute
  • Network Security Groups
  • Application Firewall
  • Route Tables
  • Third-Party Firewalls
  • Azure Firewall
  • Architectures

Attendees will require an Azure subscription capable of deploying multiple 4 x single-core virtual machines, 1 x Azure Firewall, 1 x Web Application Gateway, and 1 x per GB Log Analytics Workspace for 1 day.

When

Tuesday, 3rd March

Where

Venue: the Hackages Lab, located at Avenue des Arts 3-4-5 in Brussels

Organisers & Registration

This event is being run by The Workshop Summit. All registration and payments are handled by that event.

Who Should Attend

You don’t need to be a networking guru to attend this class. I always start my Azure networking training by explaining that I have never set up a VLAN; I’m proud of that! But I can out-network most people in Azure. Azure networking requires some learning, especially to do it correctly and securely, and that starts with re-learning some fundamentals. Those who understand basic concepts like a route, a firewall rule, network addressing (CIDR blocks), and so on will do fine on this course.

Who will benefit? Anyone planning on working with Azure. If you’re the person building the first “landing zone” for a migration, setting up the infrastructure for a new cloud-based service, working with IaaS VMs or platform (PaaS – yes network security plays a big role here!) then this course is for you. Get this stuff right early on and you’ll look like a genius. Or maybe you’ve already got an infrastructure and it’s time to learn how to mature it? We will start with the basics, cover them deeply, and then dive deep, focusing on security in ways that a typical Azure introduction course cannot do.

Why A Bastion Host Is Necessary For Remote VM Administration (Including Azure)

This post will explain why you should use a “Bastion Host” or a “Jump Box” to securely remote into Linux (SSH) or Windows (Remote Desktop) virtual machines. And this advice also includes machines that you run in a cloud, such as Microsoft Azure.

For the Fundamentalists on Social Media

Some people are going to make some comments like:

“This is why you should use remote Bash|PowerShell scripting”

Or maybe:

“You should be using Windows Admin Center”.

Windows Admin Center – great! Genuinely. But it does not do everything.

There are still many times when you need to directly log into a machine and do something; that’s real life, and not some blogger’s lab life.

Security Center JIT VM Access?

I was a fan of this feature. That was until they changed how the allow (RDP, SSH, etc) rules were added to an NSG. In my work, every subnet is micro-segmented. That means that the last user-defined NSG rule is Deny All from * to *. Since JIT VM Access was changed, it moves the last rule (if necessary) and puts in the allow-RDP or all-SSH (or whatever) rule after the DenyAll rule which is useless. Feedback on this has been ignored.

Why Are SSH and RDP Insecure?

I can’t comment too much on SSH because I’m allergic to penguins. But I can comment on RDP. Over the last few months, I can think of 3 security alerts that have been released about pre-authentication vulnerabilities that have been found in Remote Desktop. What does that mean?

Let’s say that you have a PC on your WAN that is infected by malware that leverages a known or zero-day pre-authentication remote desktop vulnerability. If that PC has the ability to communicate with a remote VM, such as an Azure Windows/Linux VM, via SSH or RDP then that remote machine is vulnerable to a pre-authentication attack. That means that if malware gets onto your network, and that malware scans the network for open TCP 22 or TCP 3389 ports, it will attempt to use the vulnerability to compromise the remote VM. It does not require the user of the PC to SSH or RDP into the remote VM, or to even have any guest OS access! You can put a firewall in front of the remote virtual machines, but it will do no good; it’s still allowing TCP 3389 or TCP 22 directly into the virtual machines and all it will offer is logging of the attack.

A Bastion Host

You might have heard the term “bastion” in the Azure world recently. However, the terms Bastion Host or Jump Box are far from new. They’re an old concept that allows you to isolate valuable machines and services behind a firewall but still have a way to remote into them.

The valuable remote virtual machines are placed behind a firewall. In Azure, that could be a firewall appliance, such as Azure Firewall, and/or Network Security Groups. Now to connect to the remote VMs, you must first remote into the Bastion Host. And from that machine, you will remote further into the network through the isolation of the firewall/NSGs.

But that’s still not perfect, is it? If we do simple SSH or RDP to the Bastion Host, then it is vulnerable to pre-authentication attacks. And that means once that machine is compromised, it can attack further into the remote network. What we need is some kind of transformation.

Remote Desktop Gateway

My preferred solution is to deploy a Remote Desktop Gateway (RDGW) as the bastion host – this does not require RDP licensing for administrative access to the remote virtual machines! The Bastion Host is deployed as one virtual machine or 2+ load-balanced virtual machines that allow in HTTPS connections via firewall/NSG rules. When an administrator/developer/operator needs to log into a remote VM, their Remote Desktop client is configured to connect to this gateway using HTTPS instead of RDP. Once the connection is authenticated by the RDGW, it reverse proxies the connection through to the desired virtual machine, further protected by firewall/NSG rules. Now the malware that is on the WAN cannot probe any machines in the remote network; there is no opening across the network to TCP 3389 or TCP 22. Instead, the only port open for remote connections is HTTPS which requires authentication. And internally, that transforms to connections from the RDGW to the remote VMs via TCP 3389.

Some sharp-eyed observers might notice that the recently announced CVE-2020-0609  is a pre-authentication attack on RDGW! Yes, unpatched RDGW deployments are vulnerable, but they are smaller in number and easier to manage patches for than a larger number of other machines. Best practice for any secure network is to limit all external ports. Transforming the protocol in some way, like an RDGW, further reduces the threat of that single opening to a single service that forwards the connection.

If you want to add bells and whistles, you can deploy Network Policy Server(s) to centrally manage RDGW policy and even add multi-factor authentication (MFA) via Azure AD.

This is great for Windows, but what about Linux? I’m told that Guacamole does a nice job there. However, Guacamole is not suitable for recent releases of Windows because of how it must have hardcoded admin credentials for Network Layer Authentication (NLA).

Azure Bastion

Azure Bastion made lots of noise in IT news sites, and on blogs and social media when it went into preview last year, and eventually it went GA at Ignite in November of last year. Azure Bastion is a platform-based RDGW. Today (January 2020), I find it way too limited to use in anything but the simplest of Azure deployments:

  • The remote desktop authentication/connection are both driven via the Azure Portal, which assumes that the person connecting into the guest OS even has rights to the Azure resources.
  • It does not support desktop Remote Desktop/SSH clients.
  • It does not offer MFA support for the guest OS login, only for the Azure Portal login (see above).
  • VNet peering is not supported, limiting Azure Bastion to pretty simple Virtual Network designs.

If Azure Bastion adds VNet peering, it will make it usable for many more customers. If it understands that guest OS/Azure resource rights OS/Azure Portal logins can be different, then it will be ready for mid-large enterprise.

 

Setting Up Azure – The Three Permissions You Will Need

You need to have rights to configure certain things in Microsoft Azure when you are setting it up for the first time. I will list those three permissions and the reasons for them in this post.

1. Global Admin Rights

You are going to need rights to configure things in Azure AD. For example, you should be creating security groups and using those for role-based access control of things like management groups, subscriptions, and maybe even resource groups – the higher in the hierarchy, the better, in my opinion.

This will require that you have Global Admin Rights. This is the equivalent of being a domain admin in Azure AD, and will impact all services attached to your directory such as Office 365. This right should be limited to just a few people. In a very large organisation, someone else might be doing these tasks for you because you will not be granted the necessary rights.

This role is easily added to the user account in Azure AD, either at the time of creation or later by opening the user account and selecting Assigned Roles.

2. Access Management For Azure Resources

This is an easy right to miss! It is also known as Elevated Access. This right gives you access to all subscriptions and management groups in your directory (tenant) and therefore grants you superuser powers that should be limited to a very small group of capable people. Here’s how I learned about the right: I was cleaning up management groups that I created using a service principal. I knew the management groups were there, and I could see them, but my Global Admin user couldn’t remove them. It was only when I elevated my account that I was able to move the subscriptions and remove the management groups.

Part of the reason this right is so hidden is that it is not configured in the user account screen in the Azure Portal. Instead, sign in to the Portal with your Global Admin-enabled user, open Azure AD, and then go to Properties. Now click “Yes” under Access Management For Azure Resources. Now you will have rights to everything in Azure even if you weren’t granted them originally – this is why this superpower should be tightly controlled!

3. Role-Based Access

The typical person working with Azure should have only the rights that they need to do their job. The two big reasons are:

  • External threats: Prevent someone from compromising a dev/ops employee’s account and using their rights to compromise the entire system.
  • Internal threats: Limit access that a single employee has, either for security or compliance reasons.

For example, one should not be made a subscription owner just “because”. Typically, being made a Contributor will give you more than enough rights to do your job in a subscription. And maybe a lesser right is necessary – an auditor might only be made a Reader or you might use/create a more specialised role.

One should start the RBAC design using management groups. As with organisational units in Active Directory Domain Services, management groups should model the administrative model, not the HR org chart. Permissions and policy association should start at the top and become more granular as you work your way down. Eventually, you will grant dev/ops rights often at the subscription or even resource group level.

Another Consideration: Privileged Identity Management

PIM is a solution in the Azure AD per-user licensing SKUs that is sometimes used in large enterprises. It allows you to deploy just-in-time access to Azure resources/rights. There are a bunch of features in PIM that make it a useful feature to limit any one person’s access to what they need, when they need it, and for only as long as they need it, with MFA, oversight, and auditing.

Failed to add new rule: IpSecurityRestriction.VnetSubnetResourceId is invalid.

This post is focused on a scenario where you are creating an Access Restriction rule in an Azure App Service to allow client requests from a subnet in a Virtual Network (VNET) and you get this error:

Failed to add new rule: IpSecurityRestriction.VnetSubnetResourceId is invalid. For request GET https://management.azure.com/subscriptions/xxxxxx/resourceGroups/xxxxxx/providers/Microsoft.Network/virtualNetworks/xxxxxx/taggedTrafficConsumers?api-version=2018-01-01 with clientRequestId xxxxxx and correlationRequestId xxxxxx, received a response with status code Forbidden, error code AuthorizationFailed, and response content: {“error”:{“code”:”AuthorizationFailed”,”message”:”The client ‘xxxxxx’ with object id ‘xxxxxx’ does not have authorization to perform action ‘Microsoft.Network/virtualNetworks/taggedTrafficConsumers/read’ over scope ‘/subscriptions/xxxxxx/resourceGroups/xxxxxx/providers/Microsoft.Network/virtualNetworks/xxxxxx’ or the scope is invalid. If access was recently granted, please refresh your credentials.”}}.

The Scenario

The customer wanted to deploy Standard Tier Azure App Services with some level of security in a hub and spoke architecture. The hub is in Subscription A. There a virtual network with an Azure Application Gateway (WAG)/Web Application Firewall(WAF) is deployed into a VNET/subnet. The WAF subnet has the Microsoft.Web Service Endpoint enabled, allowing the WAF to reverse proxy web requests via the direct path of the Service Endpoint to the App Service(s).

The App Service Plan and App Services are in Subscription B. The goal is to only allow traffic to the App Services via the WAF. All the necessary DNS/SSL stuff was done and the WAF was configured to route traffic. Now, the customer wanted to prevent requests from coming in directly to the App Service – an Access Restriction rule would be created with the Virtual Network type. However, when we tried to create that rule, it failed with the above security error.

Troubleshooting

At first, we thought there was an error with Azure Privileged Identity Management (PIM), but we soon ruled that out. The customer had Contributor rights and I had Owner rights over both subscriptions and we verified access. While doing a Teams screen share the customer read an article about Azure Key Vault with a similar error that indicated an issue with Resource Providers. We both had the same idea at the same time.

Solution

In the WAF subscription, enable the Microsoft.Web resource provider. This will allow the App Service to “configure” the integration with the subnet from its own subscription and solves the security issue.