Windows Azure Security

A Peek Under the Hood

Charlie Kaufman | 06/03/2010

Agenda

Introduction

Azure™ Compute Security

Azure Storage Security

SQL Azure™ Security

Questions

3

Azure Combines Three Components

Compute – Think Stateless CPU in the Cloud

(Rented by the CPU - hour)

Storage – Like a file system, but structured differently to support scalability and parallelism

(Rented by the Gigabyte - Month)

SQL Azure – Another form of storage, accessed with SQL queries rather than file-like operations

Can be used separately, but more commonly a Compute tenant is layered atop Storage, SQL Azure, or both

There will likely be more components in the future

4

Security Threats

Azure

Customer Tenant

Customer Admin User

External Web Site

5

From Subscription Portal

• Create a Compute Tenant

• Create a Storage Account

• Create a SQL Azure Database

Once created, they are managed via separate mechanisms

Customer authenticates to Subscription Portal using LiveID

Agenda

Introduction

Azure Compute Security

Azure Storage Security

SQL Azure Security

Questions

7

Underlying Hardware

Rack-mounted servers

Each rack has a collection of identical nodes

Each node (currently) has 2 CPU chips with 4 cores each

16 Gig of memory

Disks for local storage

Network Interface to a Top-of-Rack Switch

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Hypervisor and VM Sandbox

All Guest access to network and disk is mediated by Root VM (via the Hypervisor)

Hypervisor

Network/Disk

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What Does the World Look Like to a Guest VM?

1, 2, 4, or 8 CPUs; up to 14 GB of memory

Three disk drives:

• C:\ (for temps; initially populated with config file)

• D:\ (for application code; initially as supplied by customer admin)

• E:\ (for OS code; initially as supplied by Azure)

Network connectivity to Internet via NAT and to other VMs of same tenant

Guest agent accepts incoming HTTP/RPC connections from Root OS

10

Handling Attacks by a Tenant

Not dependent on the security of Windows®

Instead, dependent on the security of the Hypervisor and the exposed network and disk drivers

C:\, D:\, and E:\ are not really disks. They are VHD files in the root OS’s file system.

Attack surface is minimized by accepting few commands and supporting only a few hardware devices

11

Root OS Services

Disk I/O remapping and bandwidth quota enforcement

Network Packet Filter and bandwidth quota enforcement

• No forging of IP address or false responses to ARPs

• Connectivity only to Internet, peer VMs within tenant, and a small set of specific services (e.g., DNS)

• Multicast blocked except for use of DHCP to get IP address

12

Azure Network Services

For scalability, customer tenants can be divided into roles

• (e.g., front end, back end)

Roles can have multiple instances

Azure will divide incoming connections among front-end role instances

When a new role instance is created, its disks (C:\, D:\, and E:\) are initialized. When a role instance is discarded, the contents of its disks are discarded. Compute holds only ephemeral data – permanent data must be kept in Azure Storage, SQL Azure, or an external customer-provided store.

High availability is achieved through fast failover. Individual VMs can be discarded and reinitialized at any time.

13

Recovery from Any Sort of Failure

If a customer VM fails, the Root VM can reboot it or – if necessary – reinitialize all of its on-disk state

If a Root VM fails or an entire node fails, the Fabric Controller can power cycle the node, reboot it from the network, and reinitialize all of its actual disks

All customer VMs can be migrated to other nodes while the node is being tested before it is returned to service or queued for manual repair

14

Handling Attacks by a Customer Administrator

Customer Administrator gets to specify:

• How many roles in a tenant, how many instances of each role, and what size VM each runs on

• The application software that runs in each VM and its configuration

• Certificates, passwords, and secret keys each VM can use to authenticate to other entities

Requests go through the Developer Portal (browser based) or Developer API (RPC over HTTP over SSL)

Authentication to Developer API uses a certificate and private key registered through the Developer Portal

15

Protecting the Fabric Controllers

Guest Agent

Guest VM

Fabric Agent

Root VM

Hypervisor

Fabric Controller

Developer API

Developer Portal

16

Handling Attacks by an End User

Azure divides incoming connections among front-end role instances

Customer has all the facilities of Windows to protect the VM against end-user attacks

Azure must deal with DDoS (bandwidth) attacks that could overwhelm all of Azure

Customer must deal with DDoS attacks that could overwhelm the customer front ends

Increasing the number of front ends is always an option

17

Internet Gateways

Gateways are shared with other Microsoft properties (e.g., Hotmail®, MSN®, Live, …)

Very high speed links at multiple locations worldwide

Not impossible to overload, but one of the highest capacity targets deployed today

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One More Problem to Worry About…

Azure could be used as a platform for attacking other Internet sites

A customer tenant could be recruited into a bot army to spread spam or participate in DDoS attacks

A customer could intentionally participate in such things

We have to be responsive to complaints from other Internet sites that they are under attack from one of our tenants

Agenda

Introduction

Azure Compute Security

Azure Storage Security

SQL Azure Security

Questions

20

Azure Storage

Runs on separate hardware with no network connectivity to compute except (logically) through Internet

Requests run over HTTP and optionally over SSL with server authentication

Storage is organized into storage accounts

A single customer may have many storage accounts

A single secret key controls all access to a storage account

• Fine-grained access controls are not implemented

• A customer wanting fine-grained access controls can implement a front-end compute tenant that has full access to the storage account but mediates access to data items

21

Azure Storage Scalability

To reduce the need for locks when dealing with a conventional file system, Azure storage implements the primitives: blobs, tables, and queues.

For backwards compatibility, it also implements an XDrive with disk semantics for applications that have not been converted.

The customer is responsible for coordinating the assignment of XDrives to VMs. An XDrive can only be open from one VM at a time.

22

Azure Storage Security

Data from many customers is mixed in a single pool

Access to data in a specific account is only granted to entities having the secret key for that account

Storage keys are randomly generated when the storage account is created (or later at the request of the customer)

A storage account may have two active keys at any given time to support key rollover

Storage keys are used to HMAC sign each access request

23

Access Control Extensions

To deal with some common cases:

• Blobs can be marked as “world readable”, which allows them to be read without authentication by anyone knowing their name

• Queries can be HMAC signed with some of their parameters unspecified. Passing such a query and its signature to a process allows it to access a subset of the data in an XStore.

Agenda

Introduction

Azure Compute Security

Azure Storage Security

SQL Azure Security

Questions

25

Azure SQL

As with storage, runs on separate hardware with no connectivity to compute except (logically) over the Internet

Subscription portal can create databases

Data from many customers is pooled in a single SQL instance, but they are treated as separate and access controlled independently

26

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