Reach the GitHub broker over a mounted socket instead of the network (#213)

Computers on evo could not reach the broker over TCP: the git shim
reported that evOo's GitHub connection was unreachable, so cloning
private repositories still failed. Container-to-host traffic depends on
the host firewall and on which Docker network the computer joined.

- On a Linux host the supervisor also serves the broker on a unix socket
  in a host directory (SANDBOX_GITHUB_BROKER_SOCKET_DIR, default
  ~/.rakazo/github-broker), and mounts that directory read-only into
  each new computer once the socket listens.
- The shim uses the socket when it is present and falls back to the
  network otherwise; connections time out after 5 seconds and the
  unreachable message names the curl exit code.


Claude-Session: https://claude.ai/code/session_01Tgvrj34NMnaqvtgvruYQZZ

Co-authored-by: Claude <noreply@anthropic.com>

infra/sandboxes/computer/bin/rakazo-broker

@@ -4,7 +4,7 @@ set -euo pipefail
 endpoint="$1"
 payload="$2"
 post() {
-  curl -fsS -X POST "$1/$endpoint" \
+  curl -fsS --connect-timeout 5 -X POST "$1/$endpoint" "${@:2}" \
     -H "Authorization: Bearer ${RAKAZO_GITHUB_BROKER_RUN_TOKEN}" \
     -H "Content-Type: application/json" \
     --data-binary "$payload"
@@ -26,11 +26,19 @@ sys.exit(1)
 ' "$RAKAZO_GITHUB_BROKER_URL"
 }
 unreachable() {
-  echo "evOo could not reach its GitHub connection from this computer. Tell the user GitHub access is broken on the evOo server; do not ask for a token." >&2
+  echo "evOo could not reach its GitHub connection from this computer (curl exit $status). Tell the user GitHub access is broken on the evOo server; do not ask for a token." >&2
   exit 1
 }
 status=0
-response="$(post "$RAKAZO_GITHUB_BROKER_URL" 2>/dev/null)" || status=$?
+socket=/run/rakazo-github-broker/broker.sock
+if [[ -S "$socket" ]]; then
+  response="$(post http://broker/internal/github-broker --unix-socket "$socket" 2>/dev/null)" || status=$?
+fi
+# 7: nothing listening on the socket either; then try the network.
+if [[ ! -S "$socket" || "$status" == 7 ]]; then
+  status=0
+  response="$(post "$RAKAZO_GITHUB_BROKER_URL" 2>/dev/null)" || status=$?
+fi
 # 6: unresolved host, 7: connection refused, 28: timeout. Anything else is the broker answering.
 if [[ "$status" == 6 || "$status" == 7 || "$status" == 28 ]]; then
   fallback="$(gateway_url)" || unreachable

infra/sandboxes/supervisor/src/computer-spec.test.ts

@@ -107,6 +107,30 @@ describe("graphical computer spec", () => {
     expect(options.HostConfig.NetworkMode).toBe("rakazo_default");
   });
 
+  it("mounts the GitHub broker socket read-only when the supervisor serves one", () => {
+    const base = {
+      name: "rakazo-bot-abc",
+      image: COMPUTER_IMAGE,
+      botId: "abc",
+      spaceId: "ws",
+      githubBrokerSocketDir: "/srv/rakazo/github-broker",
+    };
+    expect(
+      containerCreateOptions({ ...base, homePath: "/var/rakazo/homes/abc" }).HostConfig.Binds,
+    ).toContain("/srv/rakazo/github-broker:/run/rakazo-github-broker:ro");
+    const projectMounts = containerCreateOptions({
+      ...base,
+      homePath: "/var/rakazo/homes/abc",
+      projectWorkspacePath: "/srv/projects/evoo",
+    }).HostConfig.Mounts;
+    expect(projectMounts).toContainEqual({
+      Type: "bind",
+      Source: "/srv/rakazo/github-broker",
+      Target: "/run/rakazo-github-broker",
+      ReadOnly: true,
+    });
+  });
+
   it("still publishes host ports when NetworkMode is a per-bot isolated network", () => {
     const networkMode = computerNetworkNameFor("bot_isolation");
     const options = containerCreateOptions({

infra/sandboxes/supervisor/src/computer-spec.ts

@@ -245,8 +245,13 @@ export interface ComputerCreateInput {
   controlToken?: string;
   networkMode?: string;
   publishControlPort?: boolean;
+  /** Host directory holding the GitHub broker socket, mounted read-only into the computer. */
+  githubBrokerSocketDir?: string;
 }
 
+/** Where computers find the GitHub broker socket; the git shim prefers it over the network. */
+export const GITHUB_BROKER_SOCKET_MOUNT = "/run/rakazo-github-broker";
+
 interface PointerInput {
   kind: "pointer";
   x: number;
@@ -281,6 +286,14 @@ function computerVolumeMounts(input: ComputerCreateInput): Docker.MountSettings[
       ReadOnly: false,
     });
   }
+  if (input.githubBrokerSocketDir) {
+    mounts.push({
+      Type: "bind",
+      Source: input.githubBrokerSocketDir,
+      Target: GITHUB_BROKER_SOCKET_MOUNT,
+      ReadOnly: true,
+    });
+  }
   return mounts;
 }
 
@@ -321,6 +334,9 @@ export function containerCreateOptions(input: ComputerCreateInput) {
               ...(input.projectWorkspacePath
                 ? [`${input.projectWorkspacePath}:/home/rakazo/project`]
                 : []),
+              ...(input.githubBrokerSocketDir
+                ? [`${input.githubBrokerSocketDir}:${GITHUB_BROKER_SOCKET_MOUNT}:ro`]
+                : []),
             ],
             Mounts: undefined,
           }),

infra/sandboxes/supervisor/src/index.ts

@@ -1,13 +1,14 @@
 import { randomUUID } from "node:crypto";
-import { existsSync } from "node:fs";
+import { chmodSync, existsSync, mkdirSync, rmSync } from "node:fs";
 import { mkdir } from "node:fs/promises";
 import http from "node:http";
+import os from "node:os";
 import path from "node:path";
 import { Readable } from "node:stream";
 import { pipeline } from "node:stream/promises";
 import type { ReadableStream as NodeReadableStream } from "node:stream/web";
 import { fileURLToPath } from "node:url";
-import { serve } from "@hono/node-server";
+import { createAdaptorServer, serve } from "@hono/node-server";
 import {
   boundedSandboxCommandTimeoutMs,
   readBoundedJsonResponse,
@@ -152,6 +153,31 @@ export function needsBridgeBrokerListener(
   );
 }
 
+// A socket bind-mounted into each computer reaches the broker without crossing the host firewall.
+const githubBrokerSocketDir = path.resolve(
+  process.env.SANDBOX_GITHUB_BROKER_SOCKET_DIR ??
+    path.join(os.homedir(), ".rakazo", "github-broker"),
+);
+// Set once the socket listens, so computers only get the mount when there is something behind it.
+let githubBrokerSocketReady = false;
+
+function listenGithubBrokerSocket(logger: ReturnType<typeof createRootLogger>) {
+  mkdirSync(githubBrokerSocketDir, { recursive: true, mode: 0o755 });
+  const socketPath = path.join(githubBrokerSocketDir, "broker.sock");
+  rmSync(socketPath, { force: true });
+  const server = createAdaptorServer({ fetch: brokerApp.fetch });
+  server.on("error", (error) => {
+    logger.warn("github broker socket unavailable", { "error.message": error.message });
+  });
+  server.listen(socketPath, () => {
+    // Computers may run as a different uid; the run token is what authorizes a request.
+    chmodSync(socketPath, 0o666);
+    githubBrokerSocketReady = true;
+    logger.info("github broker listening", { "server.socket": socketPath });
+  });
+  return server;
+}
+
 async function bridgeGatewayAddress(): Promise<string | undefined> {
   const network = await docker.getNetwork("bridge").inspect();
   return network.IPAM?.Config?.find((entry: { Gateway?: string }) => entry.Gateway)?.Gateway;
@@ -293,6 +319,7 @@ app.post("/computers", async (c) => {
               networkMode,
               controlToken: randomUUID(),
               publishControlPort: controlViaLoopback,
+              ...(githubBrokerSocketReady ? { githubBrokerSocketDir } : {}),
             }),
           );
           await container.start();
@@ -875,6 +902,9 @@ function startSupervisor() {
     logger.info("supervisor listening", { "http.host": hostname, "http.port": port });
   });
   let brokerServer: ReturnType<typeof serve> | undefined;
+  const brokerSocketServer = needsBridgeBrokerListener(hostname)
+    ? listenGithubBrokerSocket(logger)
+    : undefined;
   if (needsBridgeBrokerListener(hostname)) {
     void bridgeGatewayAddress()
       .then((gateway) => {
@@ -894,6 +924,7 @@ function startSupervisor() {
     if (stopping) return;
     stopping = true;
     if (brokerServer) await closeListeningServer(brokerServer);
+    if (brokerSocketServer) await closeListeningServer(brokerSocketServer);
     await closeListeningServer(server);
     await logger.flush({ timeoutMs: 2_000 });
     process.exit(0);