dsh-trusted-host-proxy-403-fix

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A standalone DeepSeek Harness plugin bundle for the web profile. Compatible with @deepseek-ai/dsh@0.1.0-rc.6.

dsh web (dsh --profile web) listens on the loopback interface. You can repeat --trusted-host to add trusted host entries that pass the /api browser request security checks. Requests to non-privileged API methods then succeed when their Host matches one of those entries.

The Node.js /api handler applies a second check to the privileged method set with an empty trustedHosts list, which restricts these methods to loopback. As a result, a reverse proxy can reach other API methods through a configured host, while these 15 methods remain unavailable. When the proxy preserves the public Host header, Settings → Models fails with:

transport failure for /api/settings.describe: HTTP 403

This plugin registers an exact /api/<method> route for each privileged method and validates those requests against the same trustedHosts list as the rest of /api. It keeps the official connection plugin in place and does not provide authentication. The official host checks control which hostnames may reach the API; they do not verify user identity. The Web transport has no built-in authentication.

Before you install

After installation, requests using any host listed in trustedHosts can call the methods below. These methods can read and change settings and credentials, open native directory dialogs, manage agent presets, and make the DSH host send a model discovery request to a URL supplied by the caller.

Install this plugin only when those hosts are already protected by authentication or equivalent network isolation.

1. Add only the hosts that clients use to --trusted-host. Each entry must be a canonical host[:port] value without a scheme, path, user information, or wildcard.
2. Protect those hosts with authentication or network isolation. Do not expose dsh web directly to the public internet with this plugin as the only protection. The official CLI still rejects --host 0.0.0.0.
3. For browser requests, the host and port in Origin must match the Host header. Requests with sec-fetch-site: cross-site or Origin: null are rejected.
4. Do not rewrite Host to a loopback address while keeping the public HTTPS origin. That mismatch also causes the rest of /api to return 403.
5. User authentication and authorization remain outside this plugin.

Privileged methods

This is the complete official PRIVILEGED_METHODS list in @deepseek-ai/dsh-client-connection 0.1.0-rc.6. All other /api routes keep the default dsh-web-app behavior.

Method	Purpose
/api/settings.describe	Read all exposed settings namespaces
/api/settings.openDocument	Open the settings document
/api/settings.update	Update settings
/api/settings.replace	Replace a settings document
/api/settings.mutate	Modify settings
/api/credentials.describe	Check whether a credential is configured and where it comes from
/api/credentials.set	Save a credential
/api/credentials.unset	Remove a credential
/api/llm.discoverModels	Send a model discovery request from the DSH host using credentials supplied by the caller
/api/host.pickDirectory	Open the native directory picker
/api/host.openPath	Open a path on the DSH host
/api/agentPreset.read	Read an agent preset definition
/api/agentPreset.copy	Copy an agent preset
/api/agentPreset.remove	Remove an agent preset
/api/agentPreset.openDocument	Open an agent preset document

The following methods are not part of this list and remain unchanged: /api/llm.providers, /api/llm.models, /api/host.describe, /api/agentPreset.list, /api/agentPreset.select, session.create, /api/events.mux, and /api/events.host.

Release an updated plugin version if the official privileged method list changes.

Install

This package uses ESM and has no prepare script, so installing it from Git does not require allowBuilds.

dsh plugin --profile web add github:roojay/dsh-trusted-host-proxy-403-fix#v0.1.0

Install from npm:

dsh plugin --profile web add dsh-trusted-host-proxy-403-fix@0.1.0

Install from a GitHub Release tarball:

dsh plugin --profile web add https://github.com/roojay/dsh-trusted-host-proxy-403-fix/releases/download/v0.1.0/dsh-trusted-host-proxy-403-fix-0.1.0.tgz

Install from a local directory:

cd /absolute/path/to/dsh-trusted-host-proxy-403-fix
pnpm install --ignore-scripts
dsh plugin --profile web add "$PWD"

The dependency installation is required for a local-directory link. Without it, DSH cannot resolve the plugin's peer dependencies when the Web process starts.

dsh web is equivalent to dsh --profile web. Restart the Web process after installation and continue passing the public host when starting it:

dsh web --port 3080 --trusted-host app.example.com

Do not hard-code a host in cordis.patch.yml. Keep trustedHosts set to !!js ctx.webRuntime.trustedHosts.

Remove the plugin:

dsh plugin --profile web remove dsh-trusted-host-proxy-403-fix

Verify

dsh --profile web --dump-config

The merged configuration should contain a # == dsh-trusted-host-proxy-403-fix section. Its trusted-host-proxy-403-fix entry should read trustedHosts from ctx.webRuntime.trustedHosts.

Send a request to the loopback address using the same host passed to --trusted-host:

# before: 403 forbidden
# after:  200 (the RPC response may be invalid-request, but it must not be forbidden)
curl -sS -D- -o /tmp/dsh-body -X POST http://127.0.0.1:3080/api/settings.describe \
  -H 'Host: app.example.com' \
  -H 'Origin: https://app.example.com' \
  -H 'content-type: application/json' \
  -d '{}'

After passing the authentication configured in front of DSH, open Settings → Models in the browser. The privileged method should no longer return 403.

How it works

dsh-host-webserver checks exact routes before prefix routes. This plugin registers one exact /api/<method> route for every privileged method, so those requests bypass the empty trustedHosts check in the official /api handler.

The plugin is pinned to @deepseek-ai/dsh@0.1.0-rc.6. It depends on the official connection service and creates its Fetch handler with createSharedFetchHandler, so its privileged routes are removed whenever the official /api route is removed. API_PATH and Config come from official exports. The request security logic and privileged method list are copied locally because rc.6 does not export them. The request body limit matches the official 160 MiB default, and errors propagate to the official WebServer error handler.

Develop

npm test

License

MIT. The request validation logic is based on @deepseek-ai/dsh-client-connection.