OpenBao CLI: Feature Request For Custom HTTP Headers

This article discusses a feature request for the OpenBao CLI, focusing on the need for custom HTTP header support. The current limitations faced when using OpenBao behind a proxy that requires specific headers are examined, along with a proposed solution and alternative considerations. This enhancement would significantly improve the usability of the OpenBao CLI in various network environments, especially those with strict security policies or web application firewalls.

The Problem: OpenBao Behind a Proxy

When running OpenBao behind a proxy, a common issue arises: the proxy often requires specific HTTP headers for authentication or routing. These headers, such as Authorization: Basic or custom routing keys, are essential for the proxy to allow traffic through to the OpenBao server. The current OpenBao CLI lacks a native mechanism to include these custom headers in its requests. This absence means that CLI requests are often blocked by the proxy before they even reach the OpenBao instance, rendering the CLI unusable in such environments. This limitation poses a significant challenge for users who rely on OpenBao in secured network infrastructures.

To illustrate, consider a scenario where an organization employs a proxy server to manage and secure network traffic. This proxy might require all requests to include a specific Authorization header containing authentication credentials or a custom routing key to direct traffic to the appropriate backend service. Without the ability to add these headers, the OpenBao CLI cannot communicate with the OpenBao server, effectively isolating it from the network. This situation necessitates a workaround, such as using curl with custom scripts, which is less efficient and harder to maintain than using the CLI directly. The core issue here is the CLI's inability to adapt to common network security practices, hindering its adoption in environments where proxies are mandatory.

Furthermore, the problem extends beyond simple authentication. Some proxies may implement more complex routing rules based on custom headers, such as those indicating the target environment (e.g., development, staging, production) or the application context. In these cases, the absence of custom header support in the OpenBao CLI becomes even more critical, as it prevents the CLI from interacting with the OpenBao server in a context-aware manner. This lack of flexibility can significantly impede automation efforts and operational workflows, as users are forced to resort to manual workarounds or alternative tools that support custom headers.

Proposed Solution: Custom HTTP Header Support

The ideal solution to this problem is to add a global flag or an environment variable to the OpenBao CLI that allows users to pass a list of custom HTTP headers with every command. This approach would provide the necessary flexibility to integrate the CLI seamlessly into environments that require specific headers for proxy communication. A global flag, such as -custom-https-headers, or an environment variable, such as BAO_CUSTOM_HTTP_HEADERS, would enable users to specify the required headers, ensuring that they are included in every request made by the CLI. Whether it's a simple login command (bao login) or a more complex data retrieval operation (bao read), the custom headers would be appended to the request, allowing the proxy to forward it to the OpenBao server.

Implementing this solution would involve modifying the CLI to read the custom headers from the specified flag or environment variable and include them in the HTTP requests it generates. The flag could accept a comma-separated list of headers, while the environment variable could contain a JSON-formatted string or a similar structured representation. This flexibility would allow users to easily configure the CLI to work with different proxy configurations and authentication schemes. The advantage of using a global flag is that it provides a clear and explicit way to specify the headers for each command invocation, while the environment variable approach allows for a more persistent configuration that applies to all CLI sessions. A combination of both, where the flag overrides the environment variable, could provide the best of both worlds.

By introducing this functionality, the OpenBao CLI would become significantly more versatile and user-friendly, particularly in environments with strict network security policies. Users would no longer need to resort to cumbersome workarounds or custom scripts to interact with their OpenBao instances. This enhancement would also align the OpenBao CLI with other tools, such as curl, that already support custom HTTP headers, making it easier for users to integrate OpenBao into their existing workflows. The addition of custom header support would not only solve the immediate problem of proxy communication but also open up new possibilities for using the OpenBao CLI in a wider range of scenarios, such as those involving web application firewalls or multi-tenant environments.

Alternatives Considered

Before proposing the addition of a global flag or environment variable, alternative solutions were considered. One such alternative was to modify the CLI to read custom headers from a configuration file. While this approach would provide a persistent way to store the headers, it might be less convenient for users who need to switch between different configurations frequently. Another alternative was to implement a command-specific flag for each command that requires custom headers. However, this approach would add significant complexity to the CLI and could lead to inconsistencies in how headers are handled across different commands. The chosen solution of a global flag or environment variable was deemed the most flexible and user-friendly option.

Another alternative considered was the use of a proxy configuration file, where users could specify the proxy settings, including the necessary headers. This approach would centralize the proxy configuration and potentially simplify the CLI's handling of proxy communication. However, it would also require the CLI to parse and interpret the configuration file, adding complexity to the implementation. Moreover, it might not be suitable for users who prefer to manage their proxy settings using environment variables or command-line flags. Therefore, the global flag or environment variable approach was favored for its simplicity and flexibility.

It's also worth noting that some users have attempted to work around the lack of custom header support by writing their own bash scripts using curl. While this approach is feasible, it is not ideal for several reasons. First, it requires users to have a good understanding of curl and HTTP headers. Second, it introduces additional maintenance overhead, as the scripts need to be updated whenever the proxy configuration changes. Third, it deviates from the standard CLI usage pattern, making it harder for new users to learn and use the OpenBao CLI. For these reasons, a native solution within the CLI is the preferred approach.

Additional Use Cases

The ability to add custom HTTP headers to the OpenBao CLI has use cases beyond just proxy communication. One significant use case is in environments with Web Application Firewalls (WAFs). Some WAFs block traffic from non-browser clients unless specific headers are present to whitelist the request. For example, a WAF might require a User-Agent header or a custom header indicating the client's identity. By allowing users to add custom headers, the OpenBao CLI can seamlessly integrate with these WAFs, ensuring that CLI requests are not blocked.

Another use case is in multi-tenant environments where different tenants require different headers for authentication or routing. In such environments, the ability to add custom headers to the OpenBao CLI allows administrators to configure the CLI to work with each tenant's specific requirements. This flexibility is crucial for managing OpenBao instances in large-scale deployments where multiple tenants share the same infrastructure.

Furthermore, custom headers can be used for advanced routing and traffic management scenarios. For example, a custom header could be used to direct requests to specific OpenBao instances based on their geographic location or performance characteristics. This capability would enable administrators to optimize the performance and availability of their OpenBao deployments by intelligently routing traffic based on custom criteria. The use of custom headers also facilitates integration with other systems and services, such as monitoring tools and logging platforms. By including custom headers in CLI requests, administrators can correlate OpenBao operations with events in other systems, providing valuable insights into the overall health and performance of their infrastructure.

Conclusion

The addition of custom HTTP header support to the OpenBao CLI would significantly enhance its usability and flexibility, particularly in environments with proxies, WAFs, or multi-tenant configurations. The proposed solution of a global flag or environment variable provides a simple and effective way for users to specify the necessary headers for their CLI requests. This enhancement would not only solve the immediate problem of proxy communication but also open up new possibilities for using the OpenBao CLI in a wider range of scenarios. By aligning the CLI with other tools that support custom headers, OpenBao can become an even more valuable tool for managing secrets and sensitive data in complex network environments.

For more information on HTTP headers and their uses, you can visit the Mozilla Developer Network. This external resource provides comprehensive documentation and examples related to HTTP headers, which can help you understand the importance and versatility of this feature in the OpenBao CLI.