Fix: API Fails To Detect Reverse Proxy With SSL Termination

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API Doesn't Detect Reverse Proxy with SSL Termination

Hey guys, let's dive into a tricky issue where the API isn't playing nice with reverse proxies when SSL termination is in the mix. This can lead to some frustrating problems, especially when your application is relying on secure connections. We'll break down the problem, explore why it happens, and then look at some solid solutions to get things working smoothly.

The Problem: Mixed Content and Incorrect URLs

So, what exactly is the issue? Imagine you've set up Kyoo behind a reverse proxy that's handling the SSL termination. This means the proxy is decrypting the HTTPS traffic before forwarding it to Kyoo. Now, when Kyoo generates URLs for things like pagination in the API, it's creating HTTP URLs instead of HTTPS. This is where the browser throws a Mixed Content error because it's trying to load resources over an insecure connection from a page served over HTTPS.

This mixed content issue is a common headache when dealing with reverse proxies and SSL. Browsers are increasingly strict about security, and they'll block these insecure requests to protect users. This can lead to broken functionality and a poor user experience. The error message you might see in the console looks something like this:

Mixed Content: The page at 'https://kyoo.domain.tld/browse' was loaded over HTTPS, but requested an insecure resource 'http://kyoo.domain.tld/api/shows?sort=name&filter=&query=&after=...'. This request has been blocked; the content must be served over HTTPS.

Essentially, the API is sending the wrong URLs, and the browser is right to be suspicious. To fix this, we need to tell the API that it's behind a secure proxy and should generate HTTPS URLs.

Why This Happens: A Matter of Perspective

To understand why this happens, think about it from the API's perspective. Kyoo, in this case, sees the connection coming from the reverse proxy, which is likely on the same network. The connection between Kyoo and the proxy is probably using HTTP, not HTTPS. Kyoo doesn't inherently know that the client's original request was over HTTPS. It just sees the connection from the proxy.

This is where the X-Forwarded-Proto header comes into play. This header is a standard way for reverse proxies to tell the backend server (in this case, Kyoo) what protocol the client used to connect to the proxy. The proxy adds this header to the request before forwarding it, and the backend can then use this information to generate the correct URLs.

Without this information, Kyoo assumes the connection is HTTP and generates URLs accordingly. This is a common issue in setups involving reverse proxies, load balancers, and SSL termination. It's crucial to have a mechanism for the backend to understand the original client's protocol.

Solution 1: Utilizing the X-Forwarded-Proto Header

The first approach to solving this is to have the API recognize and use the X-Forwarded-Proto header. This header, as we discussed, is set by the reverse proxy to indicate the protocol used by the client when connecting to the proxy. The API can then inspect this header and generate URLs with the appropriate protocol (HTTP or HTTPS).

Here's how it works:

  1. Reverse Proxy Configuration: Ensure your reverse proxy is configured to send the X-Forwarded-Proto header. Most proxies, like Nginx or Apache, have options to enable this. For example, in Nginx, you might use the proxy_set_header directive.
  2. API Implementation: Modify the API code to check for the X-Forwarded-Proto header. If the header is present and its value is https, the API should generate HTTPS URLs. Otherwise, it should generate HTTP URLs.

This approach is generally considered the preferred way to handle this issue. It's a standard practice, and many frameworks and libraries have built-in support for the X-Forwarded-Proto header. It's also flexible because it can handle different scenarios, such as when the API is accessed directly (without a proxy) or through a proxy that doesn't terminate SSL.

Solution 2: Using a Base URL Environment Variable

Another way to tackle this is to define a base URL via an environment variable. This allows you to explicitly tell the API what the base URL should be, including the protocol. This can be useful if you have a fixed deployment environment and want a simpler configuration.

Here's how this works:

  1. Define an Environment Variable: Set an environment variable, for example, API_BASE_URL, with the base URL of your API, including the protocol (e.g., https://kyoo.domain.tld).
  2. API Implementation: Modify the API code to read this environment variable and use it as the base URL for generating URLs.If the environment variable is present, construct the URLs using its value, ensuring the protocol matches.

While this approach is simpler to implement in some cases, it's less flexible than using the X-Forwarded-Proto header. It requires you to explicitly configure the base URL for each environment, which can be cumbersome if you have multiple environments (e.g., development, staging, production).

Choosing the Right Solution

Both solutions have their merits, but the X-Forwarded-Proto approach is generally recommended for its flexibility and adherence to standards. It's the more robust solution and can handle various deployment scenarios without requiring manual configuration changes. The environment variable approach is a viable option when simplicity is paramount and the deployment environment is fixed.

Consider these factors when making your decision:

  • Flexibility: How likely are you to change your deployment environment or add more proxies?
  • Complexity: How much effort will it take to implement each solution?
  • Maintainability: Which solution will be easier to maintain in the long run?

In most cases, the X-Forwarded-Proto approach provides the best balance of flexibility, robustness, and maintainability.

Kyoo Version and Implementation Details

This issue was observed in Kyoo version master, highlighting the importance of addressing it for users who deploy Kyoo behind reverse proxies with SSL termination. When implementing a solution, consider the specific framework and libraries Kyoo uses. Many frameworks offer middleware or utilities that simplify working with the X-Forwarded-Proto header.

For example, if Kyoo uses Express.js, you can use the proxy-addr package or similar middleware to reliably determine the client's IP address and protocol. These tools often handle edge cases and security considerations, making your implementation more robust.

Conclusion: Ensuring Secure and Correct URLs

In conclusion, the API's failure to detect reverse proxies with SSL termination can lead to mixed content errors and broken functionality. By either utilizing the X-Forwarded-Proto header or setting a base URL environment variable, you can ensure that your API generates correct and secure URLs. Remember that the X-Forwarded-Proto approach is generally preferred due to its flexibility and adherence to standards. By implementing one of these solutions, you'll provide a better user experience and maintain the security of your application.

So, next time you're setting up a reverse proxy with SSL termination, remember to consider how your backend API will handle protocol detection. A little bit of configuration can save you a lot of headaches down the road!