HAR Tools is a curated set of tools that aim to protect you from getting owned when sharing a HAR file. There are two main pieces of HAR Tools:
- Web Client - Sanitize generated HAR files with client-side JavaScript logic using a hosted, drag and drop web application.
- API - Sanitize generated HAR files with a request to an endpoint.
HAR files (standing for HTTP Archive) are JSON-formatted archive files used to log web browser interactions. The HAR file format is employed by various HTTP session tools for exporting recorded data. In essence, it is a JSON object structured with specific fields. It's designed to archive HTTP transactions and allow browsers to export in-depth loading performance data.
The file contains a record of a web browser's activity on a website in JSON format, typically saved with a .har extension. Most HAR files contain details like your cookie contents and the pages you accessed during the recording. But since not all fields are required, there are instances where it's ambiguous what data will be included in the file.
If someone obtains the HAR file, they can see all the submitted information, which might contain private or sensitive data. Due to the highly invasive process of recording a web browser's activity, HAR files frequently and unintentionally function as highly efficient formats for collecting and distributing large volumes of sensitive personal data.
The story of HAR's rise, fall, and the ensuing collateral damage it has wrought
How rogue browsers and an abandoned standard highlighted the hidden risks of using the platform.
Many users of the web (and even many who develop it) tend to view the platform a-historically. They assume the web has always been, and will always be, exactly as it is and could be no other way. For example, while talking to a co-worker about building this project, I wondered aloud who invented HAR files and where they came from.
His answer was something to the effect of, "may as well ask who invented bread." Not satisfied with this answer, I dug into the question myself. I quickly discovered a official document from 2012 claiming to be the file's specification.
Originally developed by the W3C's Web Performance Working Group, HAR files were designed to archive HTTP transactions. It was promoted by the Chrome DevTools team at Google as a "flexible format to record, export, and analyze network performance data" that would allow browsers to export in-depth loading performance data.
And now, all of a sudden look at this! You have all the header information. Every header that the browser appends is here, even cookies. I probably don't want to show you that... umm...
Ilya Grigorik - The HAR Show: Capturing and Analyzing performance data with HTTP Archive format (August 28, 2012)
Unfortunately, the official spec opens at the top with a large, bolded message highlighted in red which states:
DO NOT USE: This document was never published by the W3C Web Performance Working Group and has been abandoned.
You may be wondering why the heck everyone is using an abandoned format. It seems like since browser vendors are responsible and ethical stewards of the web platform, they would remove the ability to download HAR files and collaborate to develop a new and more appropriate specification.
At least that's what would happen in some lucky parallel universe. In the current universe, everyone kept using HAR files. It was even built into all the other popular web browsers. The security concerns were always known but mostly ignored until a highly visible and embarrassing security incident woke everyone up to the dangers.
The designation DO NOT USE would suggest that HAR files are not ready for production and should not be used by anyone under any circumstances, especially not you š«µ. Which naturally leads to the question, why have we continued to rely on a discontinued format invented in 2012 to the extent that it leads to a heavily publicized security incident in 2023?
Lets see what our pal ChatGPT has to say:
HAR files are widely used despite the spec being abandoned because, as a standardized format for recording HTTP transactions, they're very useful for developers. They enable the analysis of each element a webpage loads. This is a critical feature for debugging issues related to performance and application behavior. Since browsers and developer tools had already implemented the use of HAR for performance analysis, they continued to support it.
Even though the formal specification process was not completed, the practical utility for developers in real-world troubleshooting and optimization outweighed the lack of an official standard. Moreover, there hasn't been a broadly accepted alternative matching the convenience and content provided by HAR files. The warning against using the format likely pertains to its security risks from containing sensitive data.
However, developers mitigate this by using the format primarily in controlled environments and being cautious with the distribution of HAR files.
Emphasis on the final comment is mine, which is a classic ChatGPT statement. The model makes a broad and highly questionable claim that rests on a naive assumption. In this answer, it's the assumption that people generally act responsibly and cautiously while performing tasks of consequence. Naturally, the AI's assumption that developers only use HAR files within controlled, safe environments is slightly divorced from reality in light of recent evidence.
The developer-brain response to this dilemma is to include a warning somewhere in the documentation. Various versions of a disclaimer are included in documentation related to HAR files warning there will be sensitive and personally identifiable information contained in HAR files. Here's a few examples:
Before sending the HAR file to us, ensure that you remove or obfuscate any sensitive information (such as any confidential or personally identifying information as well as confidential application information) using a text editor.
After generating the
.harfile, open it in any text editor and examine the contents thoroughly to find PII and confidential information. For each value, replace it with REDACTED.
While the doc does provide a half-hearted suggestion to use a sample list of keywords they provide as a guide, using that sample list seems ill advised since the docs also go to great lengths to emphasize the sample list they're offering is incomplete and should not be fully relied upon. Here's another:
HAR files may contain sensitive information such as authentication tokens, API keys, and session cookies. We recommend that you review the HAR file contents before adding them to a repository.
Taken at face value, this recommendation sounds reasonable enough. But it ignores the widely accepted security maxim that there is a trade-off between convenience and security. Even for the responsible developer, this quote underlines the more fundamental problem of determining what exactly "sensitive information" means anyway.
Sensitive information can tautologically be defined as information that hasn't been designated as non-sensitive. Personally identifiable information can similarly be defined as information that can be used to personally identify the identity of a person. Not very useful.
Another issue with current resources is that they rarely acknowledge HAR files can extend to thousands of lines of code. Since manually examining the contents of a HAR file is wildly infeasible, how should a developer audit any given HAR file and determine what's sensitive and what's not? This is the question HAR Tools is looking to answer.
- February 2, 2011 - Jan Odvarko - HAR Viewer
- February 16, 2011 - Jan Odvarko - HAR 1.2 Spec
- February 24, 2011 - Chrome Developer Tools: Back to Basics
- August 14, 2012 - HTTP Archive (HAR) format: Historical Draft
- August 28, 2012 - The HAR Show: Capturing and Analyzing performance data with HTTP Archive format
- October 24, 2015 - Google Code Archive - harviewer
- getHAR Method for DevTools Network API
- Extending DevTools
chrome.devtools.network- Devtools API Repo
- HAR imports in the Network panel
- 1Password Security incident Report
- Tracking Unauthorized Access to Okta's Support System
- BeyondTrust Discovers Breach of Okta Support Unit
- How Cloudflare mitigated yet another Okta compromise
- Okta Support System incident and 1Password
- Introducing HAR Sanitizer: secure HAR sharing
- Unauthorized Access to Okta's Support Case Management System