API-First Data Security with Schema Validators

As the monolith dies, API-first development is grabbing hold of the modern web landscape through frameworks such as React, Node.js, and Flutter. Unlike monolithic web applications, whose server-side rendered content share validators, API-first applications are split between an API (server) and a front-end application (client). Any data-driven request a user makes through the front-end application is subject to manipulation by malicious users and must be treated as such before processing.

As developers, it’s our job to ensure the integrity of data transfers from the front-end application (client) to our API (server) remains intact. Enter schema validators. Schema validators can enhance security and ensure the integrity of all our application data in/out flows.

Schema validators validate incoming and outgoing data against our defined data structure or data contract. This data contract specifies not only the expected list of data values for a request or response but also the data types and dependencies that exist between the data values. Consistency of the data contract between client and server is critical for maintaining data integrity and preventing security vulnerabilities, such as injection attacks and data corruption. Schema validators help ensure that only valid and expected data is processed by our applications.

Benefits of Schema Validators for Web Application Security

1. Input Validation.

Injection attacks are one of the oldest and most commonly deployed exploits used by malicious users against web applications. Malicious users inject arbitrary code in instead of expected data values to gain control of an application. By using schema validators, developers can enforce strict input validation rules, ensuring that only sanitized data is passed through and used in application logic. Any request not adhering to the defined schema structure is simply rejected by the application.

2. Data Integrity

“Data contracts” is a term used to describe a consistent data structure between client and server applications. Schema validators allow developers to represent data contracts in code. A well-documented data contract ensures data integrity, preventing malformed data from being processed and minimizing application errors due to data inconsistencies.

3. Protection against Cross-Site Scripting (XXS)

Cross-Site Scripting attacks have been and will remain a security threat to web applications. Vulnerable applications are exploited by improperly validated endpoints, allowing code snippets to be injected and run. Schema validators allow developers to add character limits and data type restrictions to inputs. These prevent attackers from injecting harmful scripts that could provide unauthorized access or data leaks.

4. Defense against Denial-of-Service Attacks (DoS)

Denial-of-Service attacks are aimed to overwhelm application resources by flooding them with requests. Schema validators help mitigate this type of attack by immediately rejecting data requests that fall outside the bounds of the data contract. Though not the only countermeasure, schema validators can drastically reduce the amount of compute resources consumed during a DoS attack, helping to maintain application stability.  

Implementing Shema Validators in API-First Node.js and React Applications

1. RESTful APIs

RESTful API architecture defines a communication structure or common language to allow your server-side and front-end applications to communicate. Each request is independent of the next, where the intended CRUD (Create, Read, Update, Delete) operation is defined using HTTP method protocol (POST, GET, PUT, DELETE). The body of the request is typically a JSON document. The combination of the method protocol and JSON document is termed as our data contract. 

2. Server-Side Validation

Node.js offers various libraries for implementing schema validation of RESTful requests in our API application, such as Yup and ZOD. These libraries allow developers to define required query/body parameters and their corresponding data types. Schema validators also allow us to flag parameters as required or optional. They can even be configured to require logical dependencies between fields. The flexibility of schema validators allows strict data adherence. This reduces the drastic possibility of invalid data being processed by the server-side application.

3. Client-Side Validation

Much of our application security risk resides in the communication flow between client and server. Good application architecture should also treat data returned from server-side requests as questionable. Data flowing into our React client application should run through schema validators. Not doing so could trigger application errors due to data type mismatches or unexpected data flows. These errors could, in turn, reduce user confidence and deliver a poor overall user experience. Client-side schema validation can also help to provide rapid user feedback for invalid data submissions, returning an immediate response to users over incurring a latency-heavy API request.

4. API Documentation

Leverage your API schema definitions in conjunction with a RESTful API documentation library such as OpenAPI (formerly Swagger). Generate publicly accessible API documentation that provides API consumers with a visual documentation reference for implementing your API endpoints.

As developers, ensuring the security of API-First Node.js and React applications should be of the utmost importance. Schema validators are the first line of defense. They act as application gatekeepers, enforcing our validation rules, data flexibility constraints, and data integrity. They mitigate malicious user behavior such as Cross-Site Scripting (XXS) or Denial-of-Service attacks.

Working with a Partner That Prioritizes Security

At Soliant, we believe technology should be an asset not a liability, so we tailor the technology to fit our clients’ business needs. We optimize platforms and applications fo unique workflows and processes. Throughout every step of our work, though, security is at the forefront of our minds. We can help your business launch a custom business application built with long-term protection in mind. To learn more, contact our team to talk to a consultant today.

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