Interception
Decoding the Flow: Security through interception
Hey there, welcome to another edition of Git Checkout! As API developers, we often seek tools to validate and debug API functionalities in external environments. Utilising command-line tools for this purpose proves incredibly beneficial. Recently, I stumbled upon
’s newsletter discussing his journey in creating curl2url (definitely worth a read here). This sparked an idea: while converting a curl command to a URL is undeniably useful, having a tool to generate a curl command from code is equally valuable. My search led me to a repository that does exactly that. Despite its modest size, the utility it offers is substantial. As always, I'll dive into the repo highlighting sections of interest and how you can contribute.Let's dive in. Today, we're exploring:
- The repository
- Opportunities for contribution
- A thought-provoking quote on traffic interception
The repository
The curl2axios repository offers a practical utility for developers working with Axios to easily convert, replicate, and share their HTTP requests in the form of cURL commands. It enhances debugging capabilities, aids in learning and supports collaboration and testing efforts across diverse development environments.
Client URL (cURL, pronounced “curl”) is a command line tool that enables data exchange between a device and a server through a terminal. Using this command line interface (CLI), a user specifies a server URL (the location where they want to send a request) and the data they want to send to that server URL. (Read…)
Axios is a promise-based HTTP library that lets developers make requests to either their own or a third-party server to fetch data. It offers different ways of making requests such as GET, POST, PUT/PATCH, and DELETE. (Read…)
The repo: curl2axios
Let’s look at some of the key sections:
Generate cURL command: The `generateCurlCommand` function in the `curl2axios` library converts an Axios request configuration into an equivalent cURL command.
An Axios request configuration is a set of instructions that tells Axios, a popular JavaScript library used for making HTTP requests, exactly how to make those requests. It includes several important details like the URL (the address of the server you want to talk to), the method (such as GET for fetching data or POST for sending data), headers (additional information like passwords or tokens for security), and data (the actual information you want to send or request). By setting up this configuration, you ensure that Axios knows precisely what you're asking for.
The function begins by initialising a `curlCommand` string with the base cURL command. The function then checks for query parameters in the Axios request, appending them to the URL if present. The HTTP method is added next, followed by any headers specified in the request configuration. If provided, the function also appends the `baseURL`, serialises and includes any request data with the `--data-raw` flag, and adds authentication credentials using the `--user` flag. The constructed cURL command, which represents the Axios request as a cURL command, is then returned. (code…)
This function can be a great real time use case to learn some of the key concepts in developing in Javascript. It demonstrates the principles of abstraction and reusability by encapsulating the conversion of Axios requests into cURL commands. Through its implementation, it showcases Javascript object manipulation, string handling, and conditional logic. It also offers insights into web development fundamentals, including the structure of HTTP requests and URL management.
Curl Interceptor : The function `curlInterceptor` implemented in the `curl2axios` library acts as an Axios interceptor designed to generate and handle cURL commands derived from Axios requests.
An Axios interceptor is like a checkpoint or a filter for all the requests and responses made using Axios. When you send out a request to get data from a server or send data to a server, Axios interceptors can check and modify these requests and responses before they continue to their final destination.
Upon intercepting a request, it constructs an Axios request configuration object by extracting and structuring necessary details like baseURL, method, headers, data, URL, and authentication from the intercepted request. This configuration is then passed to the `generateCurlCommand` function, which returns a cURL command string. (code…)
This module offers a learning opportunity on how to effectively intercept and manipulate HTTP requests and responses. Through this implementation, developers can learn about the intricacies of Axios request configurations, the process of extending functionality within a third-party library, and the strategic insertion of custom logic into the request/response flow.
I hope this was helpful.
Contribution opportunities
Typically, I share potential open-source contribution opportunities within various repositories. However, this time around, I'm steering towards recommending opportunities for creating similar software or tools that could significantly benefit the developer community. Not only does this pave the way for you to carve out a reputation in the open-source software (OSS) realm, but it also positions you as an innovator and creator. With that in mind, here are a few ideas worth exploring:
Request Replay Tool: This could be an extension or library that captures outgoing HTTP requests from a web application and allows developers to replay them with modifications. This could be invaluable for testing how slight changes in requests affect the response without having to manually replicate the request setup each time.
First, you'd integrate an interceptor with your HTTP client library (like Axios) to catch every outgoing request and log its details such as the URL, method, headers, and body. These details could be stored in a structured format in a database or a local file. Next, you'd develop a user interface or a command-line tool that lists these saved requests and allows developers to select any request for replay. This interface would also permit modifications to the request's details, enabling developers to tweak parameters, headers, or the body content before resending. Finally, the tool sends the request to the original or a specified endpoint and displays the response. This setup would be incredibly useful for debugging, testing API integrations, or replicating and solving issues encountered in production environments.
Automated API Documentation: This could be a tool that intercepts API requests and responses to automatically generate documentation. By analysing the structure and parameters of requests along with their corresponding responses, it could produce up-to-date API documentation.
First, you could integrate an interceptor with your backend framework or API gateway that captures details of all API interactions, including endpoints, request methods (GET, POST, etc.), request bodies, query parameters, response structures, and status codes. Next, employ a documentation generator tool or script that takes this structured data as input and formats it into readable documentation. This tool could leverage templates to ensure consistency and clarity in the final documentation output. This automated process could immensely simplify API documentation creation thereby helping developers.
Hopefully this will get you started as a creator and an open source contributor.
A quote on traffic interception
"In the realm of security, intercepting traffic is not about eavesdropping; it's about understanding the anatomy of threats and preemptively fortifying our defences." - Bruce Schneier, Security Expert
Intercepting traffic offers valuable insight into the working of web requests, including their content and how they influence responses. It's an excellent method for enhancing your skills in developing security tools, providing a practical learning experience in understanding and securing digital communications.
That's a wrap for today's issue. As always, I value your thoughts and ideas! Should you have a specific repository or topic in mind that you're eager to delve into, I'm here to listen!
I want to make this newsletter a shared adventure. Your suggestions are more than welcome and it might just be the focus of our next discussion.
If you liked what you read, please do not hesitate to share the love.
Until the next issue,
Cheers,
– Krish
Good post Krish! And thanks for the mention.
I didn't know about curl2axios, I like their feature to generate curl commands as an Axios interceptor.
One tool that I find resonance with your idea of a request replay tool is Burp Suite, there you can replay, modify and make several interesting things.