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relay-guard: work when the plugin is reached through a symlinked folder #57

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relay-guard: work when the plugin is reached through a symlinked folder #57

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12 changes: 10 additions & 2 deletions plugins/relay/scripts/hooks/relay-guard.mjs
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,14 @@ import { SCHEMA_SENTENCE } from "../lib/harness/workflow.mjs";
const SCRIPT_DIR = path.dirname(fileURLToPath(import.meta.url));
const PLUGIN_ROOT = path.resolve(SCRIPT_DIR, "../..");
const COMPANION = path.join(SCRIPT_DIR, "..", "companion.mjs");

/**
* A path with its symlinks resolved. Node gives this module its real path, while Claude Code may run the hook and
* the relay may name the companion through a symlinked plugin folder; paths are compared resolved.
*/
function realPath(file) {
try { return fs.realpathSync(file); } catch { return path.resolve(file); }
}
const SUBCOMMANDS = new Set(["start", "wait", "result", "status", "cancel"]);
const JOB_ID = /^[0-9A-Za-z][0-9A-Za-z._-]*$/;
const SHOWN = 'node "${CLAUDE_PLUGIN_ROOT}/scripts/companion.mjs"';
Expand Down Expand Up @@ -112,7 +120,7 @@ export function parseCompanionCommand(command) {
return null;
}
const script = tokens[1].replace("${CLAUDE_PLUGIN_ROOT}", PLUGIN_ROOT);
if (path.resolve(script) !== COMPANION) {
if (realPath(script) !== realPath(COMPANION)) {
return null;
}
const subcommand = tokens[2];
Expand Down Expand Up @@ -465,7 +473,7 @@ async function main() {
}
}

if (process.argv[1] && path.resolve(process.argv[1]) === fileURLToPath(import.meta.url)) {
if (process.argv[1] && realPath(process.argv[1]) === realPath(fileURLToPath(import.meta.url))) {
main().catch((error) => {
// Fail open: a broken hook must never trap the relay or any other agent.
process.stderr.write(`relay guard: ${error instanceof Error ? error.stack ?? error.message : String(error)}\n`);
Expand Down
16 changes: 16 additions & 0 deletions tests/relay-guard.test.mjs
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Expand Up @@ -1287,3 +1287,19 @@ test("a relay that never runs start gets its job started by the hook: at its han
assert.equal(updated(handback).message, resultOf(ctx, jobId), `${what}: the hand-back is the job's result`);
}
});

test("a plugin reached through a symlinked folder: the hook runs, and knows the companion by either path", () => {
// Claude Code can install a plugin through a symlinked config folder. Node gives the hook its real path, while the
// hook is run and the relay names the companion through the symlink.
const link = path.join(makeTempDir("relay-link-"), "plugin");
fs.symlinkSync(PLUGIN_ROOT, link);
assert.deepEqual(parseCompanionCommand(`node "${path.join(link, "scripts", "companion.mjs")}" start --from-relay`),
{ subcommand: "start", jobId: null, fromRelay: true });

const ctx = relayContext("job");
const input = hookInput(ctx, "PreToolUse", { tool_name: "Bash", tool_input: { command: "sw_vers -productVersion" } });
const r = spawnSync("node", [path.join(link, "scripts", "hooks", "relay-guard.mjs")],
{ input: JSON.stringify(input), env: ctx.env, encoding: "utf8" });
assert.equal(r.status, 0, r.stderr);
assert.equal(JSON.parse(r.stdout).hookSpecificOutput.permissionDecision, "deny");
});
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