SOLID Principles of Software Architecture

The SOLID principles of software architecture consist of a collection of guidelines that can help programmers build better software. These principles help developers build loosely coupled, cohesive systems that have high cohesion and low coupling.

What are SOLID Principles of Software Architecture?

• Single Responsibility Principle
• Open/Closed Principle
• Liskov Substitution Principle
• Interface Segregation Principle
• Dependency Inversion Principle

These principles can help you build resilient, maintainable, and extendable applications. Some of the benefits of adhering to the solid principles of software architecture include:

More robust systems: By following solid principles, developers can create systems that are more resistant to change and less likely to break when modifications are made.

Better Reusability: By adhering to these principles, you can build reusable components.

Easier maintenance: Solid principle-based systems are typically easier to maintain and understand, making them less time-consuming and expensive to keep up-to-date.

Better scalability: Another advantage of using solid principles is that systems designed this way are often more scalable, meaning they can be extended over time if needed.

The Single Responsibility Principle

As per the Single Responsibility Principle, every class should not have more than one responsibility, (i.e., it should have one and only one purpose). If you have multiple responsibilities, the functionality of the class should be split into multiple classes, with each of them handling a specific responsibility.

Types with many responsibilities tend to be coupled with one another. This coupling can lead to fragile designs and such classes become difficult to manage and maintain over time.

If you adhere to this principle, here are the benefits of the Single Responsibility Principle:

Simplicity: The code is easier to understand since the functionality is not spread across multiple classes. This will help you keep your simple, manageable and clean.

Maintainability: This reduces the complexity and increases the maintainability of your code since each class has a single responsibility only.

Reusability: Since there are no dependencies between different parts of the system, you can reuse components across the application without worrying about breaking anything else.

The Open Closed Principle

According to the Open Closed Principle, classes should be open for extension, (i.e., they can be extended but closed for modification and they should not be modifiable). When classes are open for extension but closed for modification, developers can extend the functionality of a class without having to modify the existing code in that class. In other words, programmers should make sure their code can handle new requirements without compromising on the existing functionality.

Here are the benefits of the Open Closed Principle at a glance:

• You can add new features without changing existing code
• Your application will be more flexible because it can evolve over time
• It reduces the time and effort required to add new features to an application
• It increases the maintainability of the source code

Liskov Substitution Principle

It states that a child class should be able to be used in place of a parent class without any errors. This principle is essential for ensuring that software components are interchangeable and can be easily replaced without affecting the rest of the code.

It follows that if B is a subtype of A, then objects of type B can be used as substitutes for objects of type A. In other words, if you have a class A and a class B, with B being a subclass of A, then you can replace any instance of B with an instance of A.

The Interface Segregation Principle

An interface should be designed so that clients only have to know about the methods they need to use. This principle is fundamental in object-oriented programming (OOP), where interfaces are used to define the contracts between objects.

the benefits of the Interface Segregation Principle at a glance:

• Reduces coupling between components because they don’t share the same interface
• Encourages loose coupling between components, which makes them easier to change, maintain and testable
• Allows components to be replaced with alternative implementations

Dependency Inversion Principle

The Dependency Inversion Principle (DIP) is one of the SOLID principles of object-oriented programming (OOP), originally introduced by Robert C. Martin. It emphasizes two main concepts: dependency inversion and decoupling.

• Dependency Inversion: This principle states that high-level modules or components should not depend on low-level modules but should instead depend on abstractions. In other words, the direction of dependency should be inverted. Abstractions should not depend on details; details should depend on abstractions.
• Decoupling: By adhering to the Dependency Inversion Principle, classes and modules become decoupled, meaning they are not tightly bound to specific implementations. This promotes flexibility, extensibility, and ease of maintenance in software systems.

Here are some key points and benefits of applying the Dependency Inversion Principle:

Flexibility: By depending on abstractions rather than concrete implementations, components become more flexible and interchangeable. This allows for easier modification and extension of the system without requiring changes to high-level modules.

Testability: Dependency inversion facilitates unit testing by enabling the use of mock objects or stubs in place of real dependencies. This makes it easier to isolate and test individual components in isolation, improving overall code quality and reliability.

Reduced Coupling: Dependency inversion reduces coupling between modules, leading to a more modular and loosely coupled design. This makes it easier to understand, maintain, and evolve the software system over time.

Reusability: Abstractions and interfaces defined as part of the dependency inversion process can be reused across different parts of the system, promoting code reuse and modularity.

What is multi-factor authentication?

 Multi-factor authentication (MFA) is a security mechanism that requires users to provide multiple forms of verification to access an account or system. It adds an extra layer of protection beyond just a username and password, making it more difficult for unauthorized individuals to gain access.

Here's how multi-factor authentication typically works:

1. Something You Know: This is typically a password or PIN that the user knows. It's the most common form of authentication but is vulnerable to breaches if the password is weak or compromised.

2. Something You Have: This involves a physical device or token that the user possesses, such as a smartphone, security key, or smart card. The device generates a one-time passcode (OTP) or responds to a challenge to authenticate the user.

3. Something You Are: This refers to biometric factors, such as fingerprint scans, facial recognition, or iris scans. Biometric authentication relies on unique physical characteristics of the user to verify their identity.

By combining multiple factors from these categories, MFA significantly increases the security of authentication processes. Even if one factor is compromised (e.g., a stolen password), the attacker would still need access to the other factor(s) to gain unauthorized access.

Common implementations of MFA include:

• One-Time Passcodes (OTP): Users receive a temporary passcode via SMS, email, or authenticator apps (like Google Authenticator or Authy) after entering their username and password. They must enter this passcode to complete the login process.

• Hardware Security Keys: Users plug in a physical USB security key or tap it against a device (for NFC-enabled keys) to authenticate themselves. These keys store cryptographic keys and generate unique codes for each authentication attempt.

• Biometric Authentication: Users provide biometric data, such as fingerprints, facial scans, or iris scans, to verify their identity. This method is often used in conjunction with other factors for added security.

MFA is widely recommended as a best practice for securing online accounts, especially for sensitive services like online banking, email, and cloud storage. It significantly reduces the risk of unauthorized access, data breaches, and identity theft by adding an extra layer of defense against various attack vectors, including phishing, credential stuffing, and brute-force attacks.

How to stop SQL injection?

 SQL injection is a common web security vulnerability that occurs when an attacker inserts malicious SQL queries into input fields or parameters, exploiting vulnerabilities in the application's SQL query construction. Here are some measures to prevent SQL injection attacks:

1. Use Parameterized Queries (Prepared Statements): Instead of concatenating user input directly into SQL queries, use parameterized queries or prepared statements provided by your programming language or ORM (Object-Relational Mapping) library. Parameterized queries separate SQL logic from data, preventing attackers from injecting malicious SQL code.

2. Input Validation and Sanitization: Validate and sanitize all user input on the server-side before using it in SQL queries. Ensure that input conforms to expected formats, lengths, and data types, and reject input that contains suspicious characters or patterns indicative of SQL injection attempts.

3. Least Privilege Principle: Limit the permissions and privileges granted to database users and application accounts to the minimum required for their respective roles. Avoid using highly privileged accounts, such as database superusers, in application code, as they increase the impact of successful SQL injection attacks.

4. Escape Special Characters: If parameterized queries are not feasible or practical, escape special characters (e.g., quotes, semicolons) in user input before incorporating it into SQL queries. Use built-in escape functions or libraries provided by your programming language or framework to perform secure string escaping.

5. Use Stored Procedures: Encapsulate database logic within stored procedures or database functions whenever possible. Stored procedures provide a layer of abstraction between the application and the database, reducing the risk of SQL injection by limiting direct access to SQL statements.

6. Input Length Limitations: Enforce reasonable length limitations on input fields and parameters to prevent attackers from exploiting buffer overflow vulnerabilities or launching denial-of-service attacks by submitting excessively long inputs.

7. Regular Security Audits: Conduct regular security audits and code reviews to identify and remediate SQL injection vulnerabilities in your application code. Use automated scanning tools and manual testing techniques to simulate common attack scenarios and identify potential weaknesses.

8. Web Application Firewall (WAF): Deploy a web application firewall that can inspect and filter incoming HTTP requests for malicious SQL injection patterns. WAFs can provide an additional layer of defense against SQL injection attacks by blocking suspicious requests before they reach your application servers.

9. Error Handling and Logging: Implement robust error handling and logging mechanisms to capture and analyze SQL errors and exceptions. Monitor database logs for unusual or suspicious query patterns that may indicate attempted SQL injection attacks.

By implementing these preventive measures and following secure coding practices, you can significantly reduce the risk of SQL injection vulnerabilities in your web applications and protect sensitive data stored in your databases.

how to stop Script injection?

 Script injection, also known as cross-site scripting (XSS), occurs when an attacker injects malicious scripts into web pages viewed by other users. These scripts can then execute in the context of the victim's browser, potentially leading to various security vulnerabilities, such as session hijacking, data theft, or malware distribution. Here are some measures to prevent script injection.

Input Validation: Validate and sanitize all user input on the server-side before processing or storing it. Use input validation libraries or frameworks to ensure that user-supplied data conforms to expected formats and does not contain malicious content.

Output Encoding: Encode user-generated content properly before rendering it in HTML, JavaScript, CSS, or other contexts. Use encoding functions specific to the context in which the data will be used (e.g., HTML entities encoding for HTML content, JavaScript string escaping for JavaScript content).

Content Security Policy (CSP): Implement a Content Security Policy (CSP) on your website to control which resources are allowed to be loaded and executed. CSP can help mitigate the impact of XSS attacks by restricting the execution of inline scripts, evaluating trusted sources for content, and blocking unauthorized scripts.

HTTP Headers: Use HTTP security headers, such as X-XSS-Protection and X-Content-Type-Options, to enhance browser security and prevent common attack vectors. These headers can instruct the browser to enable built-in XSS protection mechanisms and enforce certain security policies.

Escape HTML Output: When dynamically generating HTML content, escape special characters such as <, >, ", ', and & to prevent them from being interpreted as HTML tags or attributes. Use libraries or functions provided by your programming language or web framework to perform HTML escaping safely.

Use Frameworks and Libraries: Use web development frameworks and libraries that offer built-in protection against XSS attacks. Many modern frameworks provide features such as automatic output encoding, CSRF protection, and session management to help developers build secure web applications more easily.

Security Audits and Testing: Regularly audit your codebase for security vulnerabilities, including XSS vulnerabilities, using automated scanning tools and manual code reviews. Perform comprehensive security testing, including penetration testing and vulnerability assessments, to identify and remediate potential security risks.

User Education: Educate users about the risks of XSS attacks and encourage them to be cautious when interacting with web content, especially user-generated content or links from untrusted sources. Provide guidance on how to recognize and avoid suspicious or malicious content.

By implementing these preventive measures and adopting security best practices, you can significantly reduce the risk of script injection vulnerabilities and protect your web application and its users from XSS attacks.

How to Stop Web Scraping?

 Stopping web scraping entirely can be challenging, as determined individuals or entities may find ways to circumvent measures put in place to prevent scraping. However, there are several strategies that can help mitigate and deter scraping activities:

1. Robust Terms of Service (ToS): Clearly outline in your website's terms of service that web scraping is prohibited without explicit permission. This can serve as a legal deterrent and provide grounds for taking action against scrapers if necessary.

2. Rate Limiting and Throttling: Implement rate limiting and throttling mechanisms on your server to restrict the number of requests that can be made within a certain time frame. This can help prevent scraping bots from overwhelming your server with requests.

3. CAPTCHA Challenges: Integrate CAPTCHA challenges into your website to verify that users are human. CAPTCHAs can make scraping more difficult for automated bots by requiring interaction that is difficult for bots to simulate accurately.

4. User-Agent Whitelisting/Blacklisting: Monitor incoming requests and filter them based on User-Agent headers. Whitelist legitimate user agents (e.g., browsers) while blacklisting known scraping bots and tools.

5. IP Address Blocking: Identify and block IP addresses associated with scraping activity. However, be cautious with this approach as it may inadvertently block legitimate users sharing the same IP address (e.g., users behind a proxy or NAT).

6. Honeypot Technique: Introduce hidden links or elements on your web pages that are not visible to regular users but are detectable by web scrapers. If a scraper follows these links, it can be identified and blocked.

7. Dynamic Content Loading: Load content dynamically using JavaScript instead of serving it directly in the HTML markup. Scrapers that do not execute JavaScript will have difficulty accessing dynamically loaded content.

8. Obfuscation Techniques: Employ techniques such as obfuscating HTML markup, encrypting data, or using client-side rendering to make it more challenging for scrapers to extract information from your website.

9. Monitoring and Analytics: Use web analytics tools to monitor traffic patterns and detect suspicious behavior indicative of scraping activity. Set up alerts for unusual spikes in traffic or patterns consistent with scraping bots.

10. Legal Action: As a last resort, consider taking legal action against individuals or organizations engaged in unauthorized web scraping activities. Consult with legal experts to understand your rights and options in such situations.

API Security Concern

 What is an API 

A software bridge that enables communication between apps is called an Application Programming Interface (API). In addition to facilitating the accessible extraction and sharing of data, it offers developers routines, protocols, and tools for creating software applications.

Applications can be connected to other platforms or services, including social networks, games, databases, and devices, via web APIs.

There are two common methods for establishing APIs: SOAP and REST.

        SOAP (Simple Object Access Protocol)

        REST (Representational State Transfer)

API Security Threats:

An attacker can modify an API's functions, data, or processes for malicious purposes through business logic assaults, which are the most prevalent sort of security issue connected to APIs. The top security risks to APIs are listed below.

Broken Object-Level Authorization

This vulnerability in authorization system, API doesn't check the Authorization of the requested user and allowed them at access the resources.

It can be prevented by a secure AAPM(Authentication, Authorization and permission Management System).

Broken User Authentication 

This vulnerability occurs in system, when API doesn't verify the users before granting them access.

it can be prevented by secure authentication method, proper password policy, Monitored failed login attempts.

Excessive Data Exposure

Excessive data responses more data than the requeste.it can be security risk because reveals the more data to unauthorized users. it will also compromise with the performance of API.

For this, review and limit the data that is exposed through an API, use selective data exposure, Maintain an API inventory and labeled the as per sensitivity and criticality.

Broken Function-Level Authorization

Mass Assignment

Security Misconfiguration

Injection Flaws

Improper Asset Management

Inadequate Logging and Monitoring

 

Key point refence for Low level Design of Software System

 

Low-Level Design Document

Project Title:

Document Version:

Date:

Prepared by: Ritesh Roushan

Table of Contents

1. Introduction
2. System Overview
3. Detailed Module/Component Design
4. Class/Component Diagrams
5. Database Schema
6. User Interface Design
7. Security Design
8. Integration Details
9. Algorithms and Data Structures
10. Error Handling
11. Logging Mechanisms
12. Testing and Quality Assurance
13. Deployment Considerations

 

1. Introduction

Provide a brief overview of the purpose and scope of the Low-Level Design document. Explain the intended audience and the objectives of the document.

2. System Overview

Reiterate the high-level system overview provided in the HLD and describe the focus of this document on detailed design aspects.

3. Detailed Module/Component Design

Provide detailed design descriptions for each module or component identified in the HLD. Include:

• Functionalities and responsibilities of each module/component.
• Inputs, outputs, and interfaces.
• Algorithms or business logic implemented within each module/component.

4. Class/Component Diagrams

Present class/component diagrams depicting the relationships between classes/components, inheritance, and dependencies. Explain the design patterns and principles used.

5. Database Schema

Detail the database schema design, including tables, fields, relationships, indexes, and constraints. Explain the rationale behind the schema design decisions.

6. User Interface Design

Describe the user interface design in detail, including wireframes, mockups, or screen layouts. Discuss user interactions, navigation flows, and usability considerations.

7. Security Design

Outline the security mechanisms and measures implemented in the system, covering authentication, authorization, encryption, and compliance with security standards.

8. Integration Details

Provide specifics on how the system integrates with external systems or services, including APIs, protocols, data formats, and error handling mechanisms.

9. Algorithms and Data Structures

Explain the algorithms and data structures used within the system, highlighting their efficiency, complexity, and implementation details.

10. Error Handling

Detail the error handling mechanisms employed within the system, including exception handling, error codes, error logging, and recovery strategies.

11. Logging Mechanisms

Describe the logging mechanisms utilized to track system behavior, debug issues, and monitor performance. Specify log levels, log formats, and log storage.

12. Testing and Quality Assurance

Discuss the testing approach, methodologies, and tools used for unit testing, integration testing, and system testing. Address quality assurance processes and standards.

13. Deployment Considerations

Explain considerations for deploying the system, including deployment architecture, deployment scripts, environment setup, and rollback procedures.

 

API Life Cycle

 There are eight stages of API Life Cycle.

1. Define
2. Design
3. Develop
4. Test
5. Secure
6. Deploy
7. Observe
8. Distribute

Version control is the major part of API design and development. Using this can improve the ability of API without braking the client's applications when new updates are rolled out. 

There are four strategy for versioning -API.

1. Versioning through URL path
2. Versioning through Parameter
3. Version though Custom Header
4. Version through Content Negotiation.