Storebox Security - Swisscom · Folder Key (EFK). 7. In order to decrypt the backup data, the Storebox client first of all requests the EFK from the Storebox portal for a specific

Storebox Security

WhitepaperStefan Lengacher

Whitepaper Swisscom Storebox Security

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Swisscom products include the functions that are required to ensure customer data can be managed and stored safely. In doing so, Swisscom relies on the tried-and-tested “Standard of Good Practice” security. The Chief Security Officer of Swisscom reports directly to the CEO of Swisscom, in order to ensure that the necessary security processes and security functions can be implemented. Hundreds of employees handle a wide variety of security functions to ensure the security of customer data. Swisscom is certified in accordance with ISO27001:2013.

The Swisscom Data Centres for the Storebox service meet the highest require-ments with regard to availability and confidentiality. These measures include the requisite physical protection measures, such as a 24-hour lobby with security personnel, video surveillance, fire prevention, UPS and separate entrances for people and material deliveries. The data centres also have the ISO27001:2013 certification from Swisscom (Switzerland) Ltd.

Summary fordecision-makers


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Content

The Components of Storebox 4

The Storebox Portal 4

Storebox Storage 4

Storebox Client 4

Storebox Mobile Apps 4

Storebox NAS-Gateways 4

The Components of the Storebox Portal 5

Main Database 5

Front-End Application Server 5

Storage Infrastructure 6

The Security Features 6

The Storebox Portal X.509 Certificate 6

Client Capability of the Storebox Portal 7

Storebox Portal Access Control 7

CTERA Transport Protocol 9

Storebox Audit Log 10

Storebox Portal – Additional Security 10

Session Management 11

Storebox NAS Gateway Security 11

Two-Factor Authentication 11

Supplier Access 12


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The Components of Storebox

The Storebox Portal

The Storebox Portal is a scalable platform, which enables cloud storage applica-tions to be created, managed and made available. It includes solutions such as file sharing and synchronisation, backup and mobile collaboration. These act as middleware, which enables Swisscom Storage (see next chapter) to be connected to the Storebox clients / end devices.

The portal infrastructure (servers) is operated completely by Swisscom. Any external access by a manufacturer, in relation to the provision of operating services for example, takes place under the controlled supervision of Swisscom personnel.

Storebox Storage

The Storebox Storage obtains its service from Swisscom Dynamic Storage. This object storage, based on EMC Atmos, is divided up into multiple storage nodes, which are distributed across various data centres of Swisscom throughout Switzerland, meaning they are highly redundant. Data stored in this storage system never leaves Switzerland, and Swisscom alone is responsible for operation.

Storebox Client

Storebox clients are software clients, which can be installed on workstations or servers. They can either be operated in so-called “Local Mode”, which enables hybrid file-level and disk-level backups via a NAS gateway, or in so-called “Cloud Mode”, which enables file synchronisation and shares and backups directly via the Storebox portal.

Storebox Mobile Apps

The Storebox mobile applications are smartphone applications, which provide secure access to the data in the Storebox portal and enable collaboration with external persons with this data. The security of these mobile apps is checked and verified by Swisscom. New versions are tested by Swisscom based on risk.

Storebox NAS Gateways

Storebox NAS gateways are hardware appliances, which can be installed locally in remote branches or offices. They act as local, cloud-integrated data storage (NAS). They enable the aggregation of data for multiple users, the synchronisation of this data and optimised backups and restores via the Storebox portal.


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The following diagram shows how these components fit together within the overall Storebox solution:

The Components of the Storebox PortalThe Storebox portal consists of the following components:

Main Database

The Storebox portal uses a main database to store all system-relevant information such as user accounts, Storebox clients, etc. This main database also stores sensitive meta data like user names and secret keys. Only the application server has a connection to this high security zone, as this database server is located within a private network without direct Internet access. The database server acts as a so-called “Catalogue Node”, which contains the object-relevant information on files and blocks of the backups.

Front-End Application Server

The Storebox portal uses a web server to provide users with access to their Storebox via a web interface (in the browser) and via mobile applications. In doing so, the web server also acts as the end point for communication with the Storebox clients. The application server only uses encrypted connections for communica-tion (HTTPS and TLS) with AES (Advanced Encryption Standard) and authenticates using a 2048 bit RSA X.509 certificate. To ensure availability and load balancing, at least 2 such servers are in operation at Swisscom. These are located in a so-called DMZ (Demilitarised Zone) and they are protected and monitored via an “Applica-tion Delivery Controller” (ADC) and an IDS/IPS system.


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Storage Infrastructure

All saved data (data at rest) on the storage nodes is encrypted using symmetrical AES-256. This encryption mechanism is used on the entire Storebox storage area (backup directories and “Cloud Drive” directories). No text whatsoever is stored as clear text in the storage system. Even in the unlikely case that an attacker obtains read access to the storage system, they will still be unable to view the content of the data.

In order to protect against tampering or corruption by people with access to the storage infrastructure, each individual file is signed using HMAC-SHA-1. Further-more, an MD5 hash protects each individual data block against corruption. This also serves as an additional integrity check, which can also be applied without the encryption key.

The Security Features

The Storebox Portal X.509 Certificate

The Storebox portal uses a 2048-bit X.509 security certificate to authenticate web browsers, NAS gateways and Storebox clients vis-à-vis the Storebox portal. NAS gateways and Storebox clients use TLS connections for this purpose, whereas web browsers use HTTPS.


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Client Capability of the Storebox Portal

Client capability means that multiple customers, or so-called tenants, can be managed with a single instance of the software. The client capability of the Storebox portal allows various service delivery aspects to be delegated for customers and partners by using virtual portal instances (tenants) of the Storebox portal. Each of these virtual portals is completely isolated from the other instances. The Storebox portal supports virtual portal instances (tenants), which are referred to as team portals. User accounts from different instances are completely separated from one another, as well as the associated saved data.

Storebox Portal Access Control

The Storebox portal supports 2 methods for restricting access:

1. IP-Based Access Control (only available for dedicated Storeboxes)

A list of specific IP address ranges can be defined, which can be used by administrators to dial-in to the portal.


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2. Role-based Access Control

Each user account in the Storebox portal is assigned a role, which defines the level of authorisation in the system. Each administrator is also assigned an appropriate role (e.g. Read/Write vs. Read-only). It is also possible to define individual permis-sions yourself. Irrespective of the role, administrators cannot simply dial-in as a user or perform actions that would be allocated to a user. The Storebox service is configured in such a way that Storebox administrators cannot access user data by default. All administrator activities are limited to the role-based definition and logged in full (together with the identity of the administrator) in the audit log.


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CTERA Transport Protocol

For maximum security of read/write operations between the Storebox client s and the Storebox portal, a highly efficient, WAN-optimised file transfer protocol was developed, the CTERA Transport Protocol (CTTP). CTTP is a TCP-based protocol, which encrypts communication “in transit” using the industry standard TLS with a configurable cipher (default is AES-256). Backup, restore and synchroni-sation data are transmitted using CTTP via TCP port 995 as follows:

1. As already mentioned, the Storebox portal uses a 2048-bit X.509 certificate, which authenticates the Storebox clients and web browser connections to the portal.

2. For the initial registration, the Storebox client establishes a connection to the portal using the username and password authentication. Following this a unique 256-bit authentication key is provided, which is then used for all subsequent connections instead of the username/password combination.

3. Prior to transmission, the Storebox client encrypts all file fragments using AES-256 CBC.

4. The keys required for this purpose are never stored permanently in the client. The Storebox portal serves as a key server and provides the client with a Data Encryption Key (DEK) as soon as they request access to a cloud folder.

5. An individual password can be created in the Storebox client for the backup function, if required. This password is used by the Storebox client to derive the so-called “Key Encryption Key” (KEK) using the PBKDF2 key derivation algorithm. For the NAS gateway, this KEK is stored permanently in flash memory.

6. The Storebox portal receives neither the KEK nor the DEK. Instead, the KEK is used to encrypt the DEK using the AES-256 key wrapping algorithm (as defined in RFC-3394). The result is then stored in the Storebox portal as an Encrypted Folder Key (EFK).

7. In order to decrypt the backup data, the Storebox client first of all requests the EFK from the Storebox portal for a specific folder.

8. The Storebox portal first checks whether the Storebox client possesses the required authorisation for accessing this folder and then returns the EFK if this is the case.

9. The Storebox client then decrypts the EFK using the KEK to receive the DEK. This is then used to save data in the folder (backup) or restore data.


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Storebox Audit Log

Both the Storebox portal and the Storebox NAS gateway web interfaces produce detailed log files with all configuration and data changes. One of the log files is the so-called “Audit Log”, which logs the various configuration changes (usually carried out by the administrators). “Audit Logs” include information on the type of change, the account names, the date, a time stamp, the elements that were influenced, etc. The Storebox portal can also log all data changes and data access.

The Audit Log can be accessed in the Storebox portal by the Storebox administrator(s).

A dedicated Storebox also allows log files to be forwarded to a syslog server for further processing, etc.

Storebox Portal – Additional Security

The Storebox portal uses “best practices” to protect its data: for example, the system automatically checks for and recognises so-called “buffer overruns”, and it includes HTML verification technologies, which prevent cross-site-scripting attacks (XSS) and carry out specific checks, in order to identify and block potential attacks, such as Cross-Site Request Forgery (CSRF), XEE, ClickJacking, etc.

The Storebox environments are so-called “hardened virtual appliances”. Only minimal configuration information (like the IP address) is saved in their file system, and access to these files is protected using SSH passwords and certifi-cates. The rest of the configuration is stored in the main database and protected using appropriate security mechanisms. Configuration changes are logged in the Storebox audit log together with the username that completed the changes.

All access (whether successful or unsuccessful) is logged. Furthermore, the system can also send the administrator e-mail alerts based on the log file entries. If a Storebox client has 3 unsuccessful login attempts, because an incorrect user-name/password combination was entered, all further login attempts from this address will be blocked for 5 minutes. This mechanism drastically reduces the risk of so-called “Password Guessing Attacks”.


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Session Management

Storebox session management focuses on preventing session prediction, capture and hijacking. Session prediction refers to the attempt to guess valid session identifiers. Session identifiers cannot be guessed on the Storebox portal, as the session ID is generated using a secure random number generator. Session capture is prevented by ensuring only encrypted communication channels are used (the Storebox portal never sends the session ID in clear text). Session hijacking is prevented by using a special “CSRF Protector Header” and by changing the session identifier for each login. This also prevents “Session Fixation Attacks”. If a user has been inactive for 30 minutes, they are logged off automatically.

Storebox NAS Gateway Security

The Storebox NAS gateway is based on a minimal version of Linux that has been subjected to security hardening. In this version, all standard services are deacti-vated to prevent potential attacks.

The Storebox NAS gateway supports the creation of encrypted volumes. If an administrator activates encryption for the content of a volume, they have to enter a password. And this is protected using “Password-Based Key Derivation Function 2” (PBKDF2). The password is then used to encrypt the encryption key using AES-256. “Volume Encryption” is based on “Linux Unified Key Setup” (LUKS), and the method makes use of the “TKS1 Key Setup” schema.

Two-Factor Authentication

Storebox supports the joint use of data by enabling users to invite guests via a public link. These invitations are URLs with an expiry time, which include a security code. They enable the guest to view the contents of a folder or file or to change these.

The Storebox administrator can define which users are authorised to create and send such invitations (possible for individual users or user groups).

Storebox allows two-factor authentication for such invitations based on a random number code (6-digit), so-called “challenges”. These are sent to the invited guest per e-mail as soon as they open the URL in a browser. This characteristic helps to ensure invitations cannot be forwarded to or accessed by unauthorised third-par-ties. The two-factor authentication protects against brute force attacks: If the code is entered incorrectly five times, it automatically becomes invalid. Further-more, so-called rate limits are used to limit the number of authentication requests and prevent “Denial of Service” attacks.

Following successful two—factor authentication on private computers, the user has the option of defining his/her computer as “trusted”. If this option is selected, a random, unique 256-bit key is saved on this computer. During the next 30 days, no further code needs to be entered from this device for access (via a public link).

All access via the public link, whether successful or not, is logged in the Storebox portal.


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Supplier Access

Swisscom offers Storebox in combination with various services provided by suppliers of Swisscom. No suppliers have access to the productive systems of Swisscom and the data they contain. Their access is limited to development and test systems, in order to analyse errors or install software fixes. All of this kind of access is limited to a specific period of time and also monitored by Swisscom employees.

Swisscom (Switzerland) Ltd, Enterprise Customers, P.O. Box, CH-3050 Berne, tel. 0800 800 900, www.swisscom.ch/enterprise

Documents

Storebox Security - Swisscom · Folder Key (EFK). 7. In order to decrypt the backup data, the Storebox client first of all requests the EFK from the Storebox portal for a specific