feat: ssh transport providers, core ssh relay and plugin folders api

src/backend/hosts/ssh-relay.ts

@@ -0,0 +1,110 @@
+/**
+ * A relay to a host's SSH port, for another Termix server that manages this
+ * one. It opens a WebSocket at /plugin-ws/core/ssh-relay with an API key
+ * ticket, names a host, and the bytes of an SSH connection run through it.
+ * This server reaches the host the way it always does, jump hosts, proxy and
+ * port knocking included, so the other server never needs a route to it. The
+ * SSH session itself stays between that server and the host.
+ *
+ * The caller needs connect access to the host, the same as for a session.
+ */
+
+import net from "node:net";
+import type { Duplex } from "node:stream";
+import { createWebSocketStream, type WebSocket } from "ws";
+import type { PluginWebSocketConnection } from "@termix-ssh/plugin-sdk/backend";
+import { resolveHostById } from "./host-resolver.js";
+import { openSshTransport } from "./connect/transport.js";
+import type { MutableConnectConfig, SshConnectHost } from "./connect/types.js";
+import { sshLogger } from "../utils/logger.js";
+import { registerCoreWsRoute } from "../plugins/ws.js";
+
+const MAX_RELAYS_PER_USER = 100;
+const open = new Map<string, number>();
+
+function close(ws: WebSocket, code: number, reason: string): void {
+  try {
+    ws.close(code, reason);
+  } catch {
+    // Already closed.
+  }
+}
+
+async function handleRelay(
+  connection: PluginWebSocketConnection,
+): Promise<void> {
+  const ws = connection.socket as WebSocket;
+  const url = String((connection.request as { url?: string }).url ?? "");
+  const hostId = Number(
+    new URL(url, "http://relay").searchParams.get("hostId"),
+  );
+  const userId = connection.userId;
+
+  if (!userId || !Number.isSafeInteger(hostId) || hostId <= 0) {
+    close(ws, 1008, "A host is required");
+    return;
+  }
+  if ((open.get(userId) ?? 0) >= MAX_RELAYS_PER_USER) {
+    close(ws, 1013, "Too many connections");
+    return;
+  }
+
+  const host = await resolveHostById(hostId, userId);
+  if (!host) {
+    close(ws, 1008, "Host not found or access denied");
+    return;
+  }
+
+  open.set(userId, (open.get(userId) ?? 0) + 1);
+  let stream: Duplex | null = null;
+  let jumpEnd: (() => void) | null = null;
+  let done = false;
+  const finish = () => {
+    if (done) return;
+    done = true;
+    open.set(userId, Math.max(0, (open.get(userId) ?? 1) - 1));
+    stream?.destroy();
+    jumpEnd?.();
+    close(ws, 1000, "Closed");
+  };
+  ws.once("close", finish);
+
+  try {
+    const sshHost = host as unknown as SshConnectHost;
+    const config = {
+      host: sshHost.ip,
+      port: sshHost.port || 22,
+    } as MutableConnectConfig;
+    const { jumpClient } = await openSshTransport(sshHost, config);
+    jumpEnd = () => jumpClient?.end();
+    stream = (config.sock as Duplex | undefined) ?? null;
+    if (!stream) {
+      stream = net.connect({
+        host: String(config.host),
+        port: Number(config.port),
+      });
+    }
+    const pipe = createWebSocketStream(ws);
+    stream.once("error", finish);
+    stream.once("close", finish);
+    pipe.once("error", finish);
+    stream.pipe(pipe);
+    pipe.pipe(stream);
+  } catch (error) {
+    sshLogger.warn("A relay could not reach its host", {
+      operation: "ssh_relay_open",
+      hostId,
+      error: error instanceof Error ? error.message : String(error),
+    });
+    finish();
+  }
+}
+
+let registered = false;
+
+/** Mounts the relay once, for servers that other Termix servers manage. */
+export function registerSshRelay(): void {
+  if (registered) return;
+  registered = true;
+  registerCoreWsRoute("/ssh-relay", handleRelay);
+}