dsh-relay: use your local DSH from a phone, through a relay you run

[ebhrz]

I wanted DSH available while away from the keyboard — approve a tool call, answer a
question, check a long run — without exposing the machine that runs dsh to the
internet and without routing prompts through a cloud service.

What it is: a plugin (dsh-relay-phone) and a small relay (dsh-relay-server).

• The plugin runs inside a DSH profile and dials out to the relay over WSS, so the
  host needs no inbound port, no public DNS and no tunnel.
• The phone opens a per-tenant entry URL and pairs by QR. It then gets a phone-shaped
  page: chat, approvals, questions, streaming output, terminals, file attachments.
• Requests that carry a body are sealed end to end with a key derived from the
  pairing secret. The relay forwards ciphertext and learns only device ids, sizes and
  timing.
• The relay is self-hosted. A small public one exists for trying it (50 MB/day keys,
  rate-limited), and the plugin works with any relay.

Install

dsh plugin --profile web add dsh-relay-phone
npm install -g dsh-relay-server
dsh-relay-server --port 8889 --agent-port 9000 --data-dir ~/.dsh-relay
dsh-relay-server tenant add --name alice --quota 50MB

Try it without a server: https://dshrelay.com:8443/ hands out a few trial keys a
day; the page states its limits up front.

Security model (the README has the full table):

• Defends: a curious or compromised relay operator (payloads are sealed), passive
  network observers, scanner noise (no key → no agent; no gate → no routing), replay
  against the pairing handshake.
• Does not defend: someone who can rewrite the page itself (HTML has to reach the
  browser in the clear, so pairing means trusting the operator), a compromised phone
  or desktop, or denial of service against the relay. Those limits are written into
  the README rather than left implied.

The project went through four rounds of adversarial review. The cross-tenant routing
bugs it turned up — a reverse-proxy connection-pool leak, then a request-smuggling
desync in the scanner I wrote to fix that — are fixed, and each one has a regression
test that reproduces it.

Links: repo https://github.com/ebhrz/dsh-relay (Apache-2.0), npm
dsh-relay-phone 0.18.6 / dsh-relay-server 0.11.3.

Feedback welcome, especially from anyone running DSH headless on a box they cannot sit
in front of.

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（中文）插件装在自己跑 DSH 的机器上，向自建中继外连，本机不用开任何入站端口；手机扫码后就能用聊天/审批/提问/流式输出/终端。带正文的请求端到端加密，中继只看到密文。安全模型的边界（页面完整性、设备被控、DoS）在 README 里写清楚了。