Incorrect Parameter Delimiter In JWT Plugin `WWW-Authenticate` Header

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Introduction

The JWT plugin in Kong is used to authenticate and authorize API requests. However, a recent observation has revealed that the WWW-Authenticate header in the JWT plugin uses spaces to separate parameters, which is not in line with the standard HTTP authentication header format as specified in RFC 7235. In this article, we will delve into the issue, explore the expected behavior, and provide a solution to rectify the problem.

Is There an Existing Issue for This?

Before we proceed, it is essential to check if there is an existing issue for this problem. After conducting a thorough search, it appears that there is no existing issue for this problem.

Kong Version

The Kong version being used is 3.9, which can be verified by running the command $ kong version.

Current Behavior

The WWW-Authenticate header in the JWT plugin uses spaces to separate parameters. This can be observed in the following code snippet from the Kong GitHub repository:

https://github.com/Kong/kong/blob/ed117a6fe801a80ddaa07b5af30ed4c5daabf241/kong/plugins/jwt/handler.lua#L161

However, according to RFC 7235 (HTTP Authentication) (Section 4.1), the parameters in authentication headers should be comma-delimited.

... and each challenge can contain a comma-separated list of authentication parameters.

The correct format should be:

WWW-Authenticate: Bearer realm="auth-server", error="invalid_token"

(Note the comma , between realm and error parameters.)

If you are unsure about the RFC's requirements for header formatting, kindly clarify or correct me.

Expected Behavior

The expected behavior is that the WWW-Authenticate header in the JWT plugin should use comma-delimited parameters, as specified in RFC 7235.

Steps to Reproduce

Unfortunately, there are no steps to reproduce this issue, as it is a configuration problem rather than a code issue.

Anything Else?

There is no additional information to provide at this time.

Solution

To rectify this issue, the following changes can be made to the JWT plugin:

  1. Update the WWW-Authenticate header to use comma-delimited parameters.
  2. Modify the code to use the correct delimiter.

Here is an example of the updated code:

local challenge = {
    realm = "auth-server",
    error = "invalid_token"
}

local header = "Bearer realm=\"" .. challenge.realm .. "\", error=\"" .. challenge.error .. "\""

return header

By making these changes, the WWW-Authenticate header in the JWT plugin will use the correct delimiter, ensuring that it conforms to the standard HTTP authentication header format as specified in RFC 7235.

Conclusion

Q: What is the issue with the JWT plugin's WWW-Authenticate header?

A: The issue is that the WWW-Authenticate header in the JWT plugin uses spaces to separate parameters, which is not in line with the standard HTTP authentication header format as specified in RFC 7235.

Q: What is the correct delimiter for authentication parameters in HTTP headers?

A: According to RFC 7235 (HTTP Authentication) (Section 4.1), the parameters in authentication headers should be comma-delimited.

Q: Why is it important to use the correct delimiter for authentication parameters?

A: Using the correct delimiter is essential to ensure that the authentication headers conform to the standard HTTP authentication header format. This is crucial for maintaining compatibility with other systems and services that rely on these headers.

Q: How can I update the JWT plugin to use the correct delimiter?

A: To update the JWT plugin, you can modify the code to use comma-delimited parameters. Here is an example of the updated code:

local challenge = {
    realm = "auth-server",
    error = "invalid_token"
}

local header = "Bearer realm=\"" .. challenge.realm .. "\", error=\"" .. challenge.error .. "\""

return header

Q: What are the benefits of updating the JWT plugin to use the correct delimiter?

A: By updating the JWT plugin to use the correct delimiter, you can ensure that the authentication headers conform to the standard HTTP authentication header format. This can help to:

  • Maintain compatibility with other systems and services that rely on these headers
  • Prevent issues related to incorrect delimiter usage
  • Improve the overall security and reliability of the authentication process

Q: Can I use a different delimiter instead of comma?

A: While it is technically possible to use a different delimiter, it is not recommended. The comma delimiter is the standard and widely accepted delimiter for authentication parameters in HTTP headers. Using a different delimiter may lead to compatibility issues and make it more difficult to maintain the authentication process.

Q: How can I verify that the JWT plugin is using the correct delimiter?

A: To verify that the JWT plugin is using the correct delimiter, you can check the WWW-Authenticate header in the response. It should contain comma-delimited parameters, as specified in RFC 7235.

Q: What if I am still experiencing issues after updating the JWT plugin?

A: If you are still experiencing issues after updating the JWT plugin, it may be due to other factors such as configuration issues or compatibility problems with other systems or services. In this case, you may need to investigate further and seek additional support to resolve the issue.

Conclusion

In conclusion, the JWT plugin in Kong uses spaces to separate parameters in the WWW-Authenticate header, which is not in line with the standard HTTP authentication header format as specified in RFC7235. By updating the code to use comma-delimited parameters, we can rectify this issue and ensure that the JWT plugin conforms to the standard HTTP authentication header format.