TCP Proxy Authentication for SYN Flood Mitigation
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Solution Overview
Problem
Current TCP protocols are vulnerable to SYN flood attacks, which lead to high interrupt rates and CPU starvation due to incomplete TCP connections, and IP address management is inefficient, especially when dealing with dynamic client IP addresses.
Innovation Solution
A transparent TCP proxy intercepts and manages TCP connections by acting as a middleman between clients and servers, using SYN cookies and cryptographic authentication to validate connections and manage IP addresses, thereby reducing the impact of SYN flood attacks and improving IP address management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the server maintains state for all half-open connections to ensure reliable TCP connection establishment, then connection reliability is improved, but memory resources are consumed and the state table may overflow during SYN flood attacks
Solution Approach 1:
The patent extracts the authentication verification from the traditional TCP handshake process by implementing a separate authentication protocol that runs independently of the standard three-way handshake. This allows the server to verify client identity without maintaining full connection state in the traditional state table, thereby reducing memory consumption while preserving connection reliability.
Solution Approach 2:
The patent introduces an authentication token as an intermediary mechanism between the client and server. Instead of directly maintaining connection state, the server uses authentication tokens to verify client identity during the handshake process. This intermediary approach allows the server to validate connections without storing extensive connection information in the state table, thus resolving the contradiction between reliability and memory resource consumption.
2Reliability
If the server processes each incoming TCP segment by verifying checksums and updating state to ensure data integrity, then data integrity is improved, but CPU time is consumed and interrupt rate increases during high connection rates
Solution Approach 1:
The patent performs authentication verification as a preliminary action before the server commits to maintaining full connection state. By verifying client identity through authentication tokens during the initial handshake phase, the server can quickly reject unauthorized connection attempts without investing CPU resources in subsequent connection processing, thereby reducing overall CPU time consumption while maintaining data integrity for legitimate connections.
Solution Approach 2:
The patent implements partial connection state maintenance by only storing essential authentication information rather than complete connection state for all half-open connections. This partial approach allows the server to verify data integrity for authenticated connections while avoiding the full CPU overhead of traditional TCP state maintenance for potentially malicious connections, thus reducing interrupt rate and CPU time usage.
3Adaptability or versatility
If the server accepts connections from any client IP address to maintain openness and accessibility, then network accessibility is improved, but vulnerability to SYN flood attacks and unauthorized access increases
Solution Approach 1:
The patent implements a self-service authentication mechanism where clients must present valid authentication tokens to establish connections. This self-service approach allows the server to maintain openness by accepting connections from any IP address while simultaneously protecting against attacks, as the authentication token verification is performed automatically without requiring the server to pre-approve specific IP addresses, thus resolving the contradiction between accessibility and vulnerability.
Data Source
AI summary
A Transmission Control Protocol (TCP) receiver receives a SYN segment from a TCP initiator that initiates a TCP handshake between the TCP initiator and a TCP server. A first value is extracted from a predefined portion of the SYN segment. A second value is computed using an authentication algorithm that includes at least using a cryptographic hash function that takes as input at least the source IP address of the encapsulating IP packet of the SYN segment and a shared secret between the TCP initiator and the TCP receiver. If the computed second value matches the extracted first value, then the TCP handshake is allowed to continue. If the computed second value does not match the extracted first value, then the TCP handshake is not allowed to continue.