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HLDsystem_design~12 mins

SQL injection and XSS prevention in HLD - Architecture Diagram

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System Overview - SQL injection and XSS prevention

This system protects a web application from SQL injection and Cross-Site Scripting (XSS) attacks. It ensures that user inputs are safely handled before reaching the database or being displayed on web pages. The key requirements are to validate and sanitize inputs, use secure query methods, and encode outputs to prevent malicious code execution.

Architecture Diagram
User
  |
  v
Web Application Firewall (WAF)
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Input Validation & Sanitization Service
  |
  +---------------------+
  |                     |
  v                     v
Parameterized Query Service  Output Encoding Service
  |                     |
  v                     v
Database               Web Server
  |                     |
  +----------+----------+
             |
             v
           Cache
Components
User
user
Sends requests with inputs to the web application
Web Application Firewall (WAF)
firewall
Filters malicious traffic and blocks common attack patterns
Load Balancer
load_balancer
Distributes incoming requests evenly to backend services
API Gateway
api_gateway
Routes requests to appropriate backend services and enforces security policies
Input Validation & Sanitization Service
service
Checks and cleans user inputs to remove harmful content
Parameterized Query Service
service
Executes database queries using safe parameterized statements to prevent SQL injection
Output Encoding Service
service
Encodes data before sending to the web server to prevent XSS attacks
Database
database
Stores application data securely
Web Server
service
Delivers web pages to users with encoded safe content
Cache
cache
Stores frequently accessed data to improve response time
Request Flow - 12 Hops
User → Web Application Firewall (WAF)
Web Application Firewall (WAF) → Load Balancer
Load Balancer → API Gateway
API Gateway → Input Validation & Sanitization Service
Input Validation & Sanitization Service → Parameterized Query Service
Parameterized Query Service → Cache
Cache → Parameterized Query Service
Parameterized Query Service → Database
Database → Parameterized Query Service
Parameterized Query Service → Output Encoding Service
Output Encoding Service → Web Server
Web Server → User
Failure Scenario
Component Fails:Input Validation & Sanitization Service
Impact:Malicious inputs may reach the database or web server, causing SQL injection or XSS attacks.
Mitigation:Use Web Application Firewall (WAF) as a secondary filter and implement parameterized queries and output encoding as defense-in-depth.
Architecture Quiz - 3 Questions
Test your understanding
Which component ensures that user inputs do not contain harmful SQL code?
AInput Validation & Sanitization Service
BOutput Encoding Service
CCache
DWeb Server
Design Principle
This architecture uses multiple layers of defense including input validation, parameterized queries, output encoding, and caching to prevent SQL injection and XSS attacks while maintaining performance and security.