SSTP VPN

Introduction

A Virtual Private Network (VPN) has become an essential tool for protecting one’s privacy and security while using public internet connections. Among the various VPN protocols, Secure Socket Tunneling Protocol (SSTP) is steadily gaining popularity among Windows users for creating encrypted VPN connections.

SSTP is a proprietary VPN protocol introduced and trademarked by Microsoft. As the name suggests, it relies on the highly secure SSL/TLS protocol for establishing a secured VPN tunnel. Traffic passing through an SSTP tunnel benefits from encapsulation within HTTPS, providing effective defense against threats.

With native integration into Microsoft’s Windows OS and inbuilt encryption capabilities, SSTP offers Windows users a fast and convenient way for creating VPN links to access remote private networks or evade internet restrictions and blocking.

What is SSTP VPN?

Introduced in Windows Vista Service Pack 1, Secure Socket Tunneling Protocol or SSTP is a VPN protocol developed by Microsoft that uses the SSL (Secure Sockets Layer) or TLS (Transport Layer Security) protocol to provide a secured connection between a client and VPN server for Windows PCs.

It enables the encapsulation of Point to Point Protocol (PPP) traffic over SSL channels providing a mechanism to bypass internet censorship and geo-blocked access.

Development and Working

In 2005, Microsoft began work for a new VPN tunneling protocol after acknowledging vulnerabilities in commonly used protocols like PPTP. They conceptualized SSTP as a successor to Microsoft’s aging PPTP and the prevalent L2TP IPsec protocol.

The SSTP protocol was designed to offer the protection and authentication of L2TP/IPsec through the highly secure encryption channels offered by the SSL protocol over TCP port 443. This allowed easier traversal of NAT gateways and firewalls compared to L2TP/IPsec.

By encapsulating PPP traffic over SSL – protected channels, SSTP enables the secure transport of data across public internet infrastructure. Servers only require TCP port 443 enabled instead of multiple ports like other protocols.

Comparison with PPTP and L2TP

Unlike PPTP tunnels which have proven vulnerable to security threats, SSTP data channels rely on strong 256-bit SSL encryption between VPN peers. Authentication uses SSL certificates compared to the preshared key model of PPTP.

And while L2TP/IPsec may seem comparably secure on paper, SSTP enjoys wider accessibility through firewalls and offers better speeds over long distances. No additional client software installation is required beyond SSL libraries as SSTP uses native Windows PPP drivers.

Security of SSTP VPN

Microsoft’s SSTP protocol combines the security capabilities of L2TP IPsec VPNs with the intense encryption strengths of SSL VPNs. Some core security features include:

SSL Layer Security

SSTP rides its VPN connections over SSL 3.0 thereby gaining immediate access through common HTTPS ports. The TLS transport layer encrypts packets preventing deep packet analysis attacks.

Server Authentication

SSTP authenticates VPN servers using standard PKI SSL certificates. 2048-bit RSA certificates secure the handshake and key setup process between an SSTP client and server.

Data Authentication

Once security keys are exchanged, the SSL layer additionally protects encapsulated data from tampering by attackers using SHA-1 based hashes for traffic authentication and integrity checks.

Encryption

SSTP uses cipher suites like RC4-SHA and AES-256 to enable robust SSL encryption with up to 256-bit keys for PPP payload protection. MS-CHAPv2 and EAP ensure user data privacy.

This layered security model prevents SSTP tunnels being compromised through spoofing, tampering or sniffing attempts. Bypassing SSL protection is rendered nearly impossible if sufficiently long keys are used.

Advantages of SSTP VPN

• Seamlessly integrated into Microsoft Windows
• Supports SSL encryption up to 256-bit strength
• Uses single well-known HTTPS port for connections
• Compatible with firewalls and web proxies
• Provides data authentication checks
• Offers good speeds over high latency networks
• No additional client software installation needed

For Windows users, SSTP brings VPN capabilities built into the OS without resorting to third party tools. It avoids dependencies on IPsec associations or infrastructure not easily available on public internet. Reliance on widely used SSL libraries and certificates ensures broader interoperability.

Disadvantages of SSTP VPN

• Not open-source, fully controlled by Microsoft
• SSL overhead causes up to 10% performance hit
• Often blocked in countries upholding internet censorship
• Can only run on Vista SP1 onwards Windows versions
• SSL credentials may not validate on some projects
• Lacks perfect forward secrecy of protocols like OpenVPN

While perfectly fine for secure remote access, SSTP has limitations when used outside controlled environments. It works best alongside SSL inspection tools with access to certificate authorities and suffers issues in restricted regions. Non-Windows clients lack native support as well.

Applications of SSTP VPN

Microsoft promotes SSTP’s use for connecting enterprise or small business networks over public internet infrastructure avoiding the costs of dedicated leased lines.

Secure Remote Access

For organizations, SSTP offers an inexpensive way to enable remote employees to securely access internal corporate networks from external connections including homes, hotels and hotspots.

It requires only minor infrastructure adjustments compared to traditional IPSec setups. Especially suitable for virtualized environments, MS Azure VPN gateways primarily use SSTP for such access.

Smart Grid Networks

In energy delivery systems like smart grids, SSTP provides robust site-to-site connectivity of advanced metering infrastructure over large areas utilizing existing internet networks instead of private links. Data analytics, distribution management and load balancing applications utilize SSTP VPN connectivity.

How to Setup SSTP VPN

Here is a step-by-step guide to setting up SSTP VPN manually on supported Windows and Linux distributions:

On Windows OS

1. Enable Routing and Remote Access from Control Panel > Programs > Turn Windows features on or off
2. Open Routing and Remote Access console, right click VPN server and choose Configure and Enable.
3. Add user accounts and groups that require remote VPN access under Dial-in tab and access permission rights. Click Ok.
4. Right click Network Interfaces > New Demand Dial Interface > Select VPN connection.
5. Set IP address pool for VPN clients. Confirm configurations.
6. Click Apply to create an SSTP VPN connection which now shows under VPN Connections list.

On Linux

1. Install Microsoft’s sstp-client package on kernel 3.6+ Linux distribution using terminal:

2. Create a new configuration file:

3. Set sstp server address, authentication details

4. Apply the config and start the connection:

This creates an active SSTP VPN tunnel rerouting traffic over the SSL link.

For improved security however, SSTP is best used on Windows platforms offering native integration with certificate authorities ensuring reliable server authentication and network endpoint identification.

Conclusion

Microsoft’s proprietary SSTP brings effective VPN capabilities to Windows networks through widespread SSL libraries and native OS support. TLS-based encryption, server authentication using PKI certificates and integrated PPP handling give SSTP VPN definite advantages over legacy PPTP.

It avoids complex IPsec infrastructure and provides better Nat/firewall traversal than L2TP. 2048-bit RSA keys secure traffic integrity checks between endpoints. For Windows environments, SSTP is easier to setup than OpenVPN.

However for open-source Linux networks, SoftEther VPN with SSL-VPN capabilities offers a full-featured cross-platform SSTP alternative. As Microsoft limits SSTP for Windows and Azure users only, better future exists for emerging VPN protocols building in SSL and Elliptic curve cryptography support.

SSTP fills an important niche securing remote access and distributed network links across enterprises. It promises better speeds than OpenVPN but lacks advanced configurations beyond Microsoft’s proprietary solution. For privacy-centric users, OpenVPN still ranks higher while SSTP best serves Windows server links.