Fix: Multiple Auth Headers Sent In Elastic Stack Provider

by SLV Team 58 views
Bug: Multiple Authorization Headers Sent in Some Cases

Hey everyone, let's dive into a tricky bug that some of you might have encountered while working with the Elastic Stack provider. This issue involves multiple Authorization headers being sent, which can lead to unexpected problems, especially when dealing with proxies. So, let's break down what's happening, how to reproduce it, and what the expected behavior should be.

Understanding the Issue: Multiple Authorization Headers

The core of the problem lies in how the Elastic Stack provider handles authorization when Kibana or Fleet is configured with a different authentication mechanism than Elasticsearch. Specifically, if you're using API keys for Elasticsearch and basic authentication for Kibana, you might run into this bug. This can cause issues because sending multiple Authorization headers violates RFC 7230, which states that a single header field should not appear multiple times in a message.

When Elasticsearch is behind certain proxies, this violation can trigger 400 responses, making it crucial to address this issue. The problem occurs because the provider incorrectly adds both the API key and basic authentication headers to the same request, leading to the multiple Authorization headers.

Having a solid grasp of the underlying problem is essential, guys. It’s not just about fixing the bug; it’s about understanding the potential impact on your infrastructure. When multiple authorization headers are sent, the server might get confused about which authentication method to use. This confusion can result in authentication failures, unexpected errors, or even security vulnerabilities. Therefore, understanding this issue deeply helps us appreciate the significance of the fix and the importance of adhering to HTTP standards.

To add more context, think about how different components within your Elastic Stack environment interact. Elasticsearch, Kibana, and Fleet might each require unique authentication setups. Elasticsearch might use API keys for secure access, while Kibana could be configured with basic authentication (username and password). When the Elastic Stack provider attempts to manage these components, it needs to handle these different authentication methods correctly. The bug arises when the provider doesn’t properly segregate these methods, leading to a mix-up in the headers.

Consider also the role of proxies in your infrastructure. Proxies often act as intermediaries between clients and servers, enforcing security policies and managing traffic. If a proxy is configured to strictly adhere to HTTP standards (like RFC 7230), it might reject requests containing multiple authorization headers. This rejection can manifest as 400 errors, effectively blocking legitimate requests and disrupting your workflow.

How to Reproduce the Bug

To really nail down this issue, let's walk through the steps to reproduce it. This way, you can see the bug in action and verify the fix once it's applied.

Steps to Reproduce

  1. Configure the Provider:

    • Set up your elasticstack provider to use Elasticsearch with an API key and Kibana with basic authentication. Your Terraform configuration should look something like this:
    provider "elasticstack" {
  elasticsearch {
    endpoints = ["https://<redacted-es-endpoint>:9200"]
    api_key   = var.elasticsearch_api_key
  }
  kibana {
    endpoints = ["https://<redacted-kibana-endpoint>"]
    username = "elastic"
    password = "<redacted>"
  }
}

  2. Apply the Plan:

    • Run terraform apply with debug logs enabled (TF_LOG=debug terraform apply). This will give you detailed output to examine.

  3. Verify the Logs:

    • Check the debug logs for multiple Authorization headers in requests to Kibana. You should see something similar to the following:
    2025-10-21T16:57:42.860+0200 [DEBUG] provider.terraform-provider-elasticstack_v0.12.0: Fleet API Request Details:
---[ REQUEST ]---------------------------------------
POST /api/fleet/outputs HTTP/1.1
Host: <redacted>
User-Agent: Go-http-client/1.1
Content-Length: 4611
Authorization: ***************************************************
Authorization: ********************************************************************
Content-Type: application/json
Kbn-Xsrf: true
Accept-Encoding: gzip
...
    • Notice the two Authorization headers? That's the bug right there!

It's worth noting that if you exclude the username and password from the Kibana block, only a single Authorization header is sent. This observation gives us a clue about the source of the problem – it's likely related to how the provider combines different authentication methods.

To really understand the impact, let’s break down what happens behind the scenes when you run terraform apply. Terraform reads your configuration files and figures out what changes need to be made to your infrastructure. When the elasticstack provider is involved, it communicates with Elasticsearch and Kibana APIs to create, update, or delete resources. During this communication, the provider needs to authenticate with these services.

The configuration we've described sets up a scenario where the provider has to handle two different authentication schemes: API keys for Elasticsearch and basic authentication for Kibana. The bug occurs because the provider mistakenly includes both sets of credentials in the same request. This is like showing two different IDs at the same time – it confuses the server, especially if it's sitting behind a strict proxy.

By following these steps, you can clearly see the bug in action. This not only helps in confirming the issue but also provides a baseline for testing the fix. Once the fix is implemented, you can repeat these steps to ensure that the multiple Authorization headers are no longer being sent.

Expected Behavior: A Single Authorization Header

According to RFC 7230, a single Authorization header should be sent per request. This is the expected behavior, and it's crucial for ensuring compatibility with proxies and other HTTP intermediaries. The fix should ensure that only the necessary authorization header for the specific service being accessed (Elasticsearch or Kibana) is included in the request.

To emphasize this point, let’s dive deeper into the reasons why adhering to HTTP standards is so important. HTTP (Hypertext Transfer Protocol) is the foundation of data communication on the web. It defines a set of rules for how messages are formatted and transmitted between clients and servers. RFC 7230, specifically, deals with the syntax and semantics of HTTP messages. By sticking to these standards, we ensure that our applications and services can communicate smoothly with each other, regardless of the underlying infrastructure.

When we violate these standards, we risk introducing compatibility issues. In the case of multiple authorization headers, some servers or proxies might not know how to handle the request. They might choose to reject it outright, leading to failed operations. Others might try to interpret the headers but do so incorrectly, leading to unpredictable behavior. In either case, we end up with a less reliable and more fragile system.

Imagine a scenario where you’re trying to automate deployments using Terraform and the Elastic Stack provider. If the provider is sending multiple authorization headers, your deployment might fail intermittently, depending on the specific proxy configuration in place. This can be incredibly frustrating and time-consuming to troubleshoot. By ensuring that we send only a single, correct authorization header, we can avoid these headaches and create a more robust automation workflow.

Furthermore, security is a key consideration here. Sending unnecessary authorization information can potentially expose sensitive credentials. If a request includes both an API key and basic authentication credentials, there’s a risk that one of them could be intercepted or mishandled. By sending only the required credentials, we minimize the attack surface and improve the overall security posture of our systems.

In summary, the expected behavior is not just a matter of technical correctness; it’s about ensuring reliability, compatibility, and security. By adhering to the single authorization header rule, we can build more robust and trustworthy systems.

Debug Output: Spotting the Issue in the Logs

When debugging this issue, the logs are your best friend. The debug output clearly shows the multiple Authorization headers being sent:

2025-10-21T16:57:42.860+0200 [DEBUG] provider.terraform-provider-elasticstack_v0.12.0: Fleet API Request Details:
---[ REQUEST ]---------------------------------------
POST /api/fleet/outputs HTTP/1.1
Host: <redacted>
User-Agent: Go-http-client/1.1
Content-Length: 4611
Authorization: ***************************************************
Authorization: ********************************************************************
Content-Type: application/json
Kbn-Xsrf: true
Accept-Encoding: gzip
...

This snippet is a smoking gun. It confirms that the provider is indeed sending two Authorization headers, which violates the standard and can cause problems.

To really dissect this, let’s walk through how to interpret this debug output. When you enable debug logging in Terraform (by setting the TF_LOG=debug environment variable), Terraform and its providers produce a stream of detailed messages about their operations. These messages can be invaluable for troubleshooting issues.

In this specific log excerpt, we’re looking at the details of an HTTP request made by the elasticstack provider to the Fleet API. The ---[ REQUEST ]--------------------------------------- marker indicates the start of the request details. Below this, we see a breakdown of the HTTP headers and the request body.

The critical part here is the Authorization headers. We see two of them, each with a different value. One likely corresponds to the API key for Elasticsearch, while the other corresponds to the basic authentication credentials for Kibana. The presence of two such headers in the same request is a clear indication of the bug.

By examining the other headers, we can get a better sense of the context. The POST /api/fleet/outputs HTTP/1.1 line tells us that this is a POST request to the /api/fleet/outputs endpoint. The Host header indicates the target server. The Content-Type header specifies that the request body is in JSON format.

The request body itself (the JSON payload) contains the configuration details for a Fleet output. This might include information about the hosts, SSL certificates, and other settings.

When you’re troubleshooting issues like this, it’s helpful to look at the entire request and response. The response from the server can often provide additional clues about what went wrong. For example, if the server returns a 400 error (Bad Request), it’s likely because it couldn’t handle the multiple authorization headers.

By carefully examining the debug output, you can pinpoint the exact point where the bug occurs. This makes it much easier to understand the problem and devise a solution. It’s like having a magnifying glass that allows you to see the inner workings of your Terraform deployments.

Versions Affected: Identifying the Scope

This bug has been observed in the following versions:

  • OS: MacOS
  • Terraform Version: v1.9.3
  • Provider Version: v0.12.1
  • Elasticsearch Version: 9.1.5

Knowing the affected versions helps narrow down the scope of the issue and ensures that the fix is applied to the correct environments. If you're running these versions, it's crucial to be aware of this bug and take steps to mitigate it.

To fully appreciate the importance of version information, let’s think about how software development and maintenance work. Software is constantly evolving, with new features, bug fixes, and security patches being released regularly. Each version of a piece of software (whether it’s an operating system, a programming language, a library, or a provider like elasticstack) represents a specific state of that software.

When we encounter a bug, the version information helps us understand whether the bug is a known issue in that version. It allows us to check the release notes, bug trackers, and other resources to see if a fix is already available or if a workaround has been documented.

In the case of this multiple authorization headers bug, knowing that it affects elasticstack provider version v0.12.1 is crucial. If you’re using this version, you know that you’re potentially vulnerable and should consider upgrading to a newer version or applying a workaround. If you’re using an older version, you might not be affected by this particular bug, but you might be exposed to other issues that have been fixed in later releases.

Similarly, knowing the versions of Terraform and Elasticsearch involved helps us understand the context of the bug. Terraform version v1.9.3 might have certain behaviors or dependencies that interact with the elasticstack provider in specific ways. Elasticsearch version 9.1.5 might have security policies or authentication mechanisms that are relevant to the issue.

In a professional environment, version management is a critical practice. It involves tracking the versions of all the software components used in your infrastructure and applications. This allows you to quickly identify potential compatibility issues, security vulnerabilities, and bug fixes. It also helps you plan upgrades and migrations in a systematic way.

Sample Terraform Configuration: A Practical Example

Here's a sample Terraform configuration that reproduces the bug:

provider "elasticstack" {
  elasticsearch {
    endpoints = ["$var.es_https_endpoint"]
    api_key = "xxxxxxxxxx=="
  }

  kibana {
    endpoints = ["${var.kibana_https_endpoint}"]
    username  = "elastic"
    password  = "<redacted>"
  }
}

resource "elasticstack_fleet_output" "logstash" {
  name = "Logstash"
  type = "logstash"

  default_integrations = false
  default_monitoring   = false

  hosts = [
    "foo.example.com:5444"
  ]
}

This configuration sets up the elasticstack provider with Elasticsearch using an API key and Kibana using basic authentication. It then creates a Fleet output resource, which triggers the bug when applied.

To understand why this configuration triggers the bug, let’s break it down piece by piece. The provider "elasticstack" block configures the Elastic Stack provider, which is the component responsible for interacting with Elasticsearch, Kibana, and other Elastic Stack services. Within this block, we have two nested blocks: elasticsearch and kibana.

The elasticsearch block configures the connection to Elasticsearch. It specifies the endpoint (the URL where Elasticsearch is running) and the API key used for authentication. API keys are a secure way to authenticate with Elasticsearch, as they don’t require transmitting usernames and passwords.

The kibana block configures the connection to Kibana. It also specifies the endpoint and uses basic authentication, which involves providing a username and password. Basic authentication is a common method for securing web applications, but it’s generally considered less secure than API keys, as the credentials are sent in an encoded form that can be intercepted.

The resource "elasticstack_fleet_output" "logstash" block defines a Fleet output resource. Fleet is a component of the Elastic Stack that allows you to manage and monitor agents (like Beats) that collect data from your systems. A Fleet output specifies where the collected data should be sent. In this case, we’re creating an output named “Logstash” that sends data to a Logstash instance.

The critical thing to note here is that this configuration requires the elasticstack provider to interact with both Elasticsearch and Kibana, each using a different authentication method. When Terraform applies this configuration, the provider makes API calls to both services. The bug arises because the provider incorrectly includes both the API key and the basic authentication credentials in the same request, leading to the multiple authorization headers issue.

By providing this sample configuration, we make it easier for others to reproduce the bug and test the fix. It also serves as a clear example of how the bug manifests in a real-world scenario. This practical example helps to bridge the gap between the theoretical description of the bug and its actual impact on users.

Conclusion

Multiple Authorization headers being sent is a significant bug that can cause compatibility issues and authentication failures. By understanding the steps to reproduce the bug, the expected behavior, and the affected versions, you can effectively troubleshoot and mitigate this issue. Keep an eye out for updates to the elasticstack provider that address this bug, and in the meantime, consider workarounds such as ensuring consistent authentication mechanisms across your Elastic Stack components. Let's keep our systems running smoothly, guys!