Restrict github token (#140)

entry

@@ -119192,9 +119192,6 @@ function filterEnv(isPublicRepo) {
     if (isPublicRepo && isSensitive(key)) continue;
     filtered[key] = value2;
   }
-  if (process.env.ORIGINAL_GITHUB_TOKEN) {
-    filtered.GITHUB_TOKEN = process.env.ORIGINAL_GITHUB_TOKEN;
-  }
   return filtered;
 }
 function spawnSandboxed(params) {
@@ -120772,10 +120769,11 @@ var PushBranch = type({
   branchName: type.string.describe("The branch name to push (defaults to current branch)").optional(),
   force: type.boolean.describe("Force push (use with caution)").default(false)
 });
-function PushBranchTool(_ctx) {
+function PushBranchTool(ctx) {
+  const defaultBranch = ctx.repo.repo.default_branch || "main";
   return tool({
     name: "push_branch",
-    description: "Push the current branch (or specified branch) to the remote repository. Git automatically determines the correct remote based on branch config (set by checkout_pr for fork PRs). Never force push unless explicitly requested.",
+    description: "Push the current branch (or specified branch) to the remote repository. Git automatically determines the correct remote based on branch config (set by checkout_pr for fork PRs). Never force push unless explicitly requested. Pushes to the default branch are blocked.",
     parameters: PushBranch,
     execute: execute(async ({ branchName, force }) => {
       const branch = branchName || $("git", ["rev-parse", "--abbrev-ref", "HEAD"], { log: false });
@@ -120790,6 +120788,11 @@ function PushBranchTool(_ctx) {
         remoteBranch = mergeRef.replace("refs/heads/", "");
       } catch {
       }
+      if (remoteBranch === defaultBranch) {
+        throw new Error(
+          `Push blocked: cannot push directly to default branch '${remoteBranch}'. Create a feature branch and open a PR instead.`
+        );
+      }
       const refspec = branch === remoteBranch ? branch : `${branch}:${remoteBranch}`;
       const args3 = force ? ["push", "--force", "-u", remote, refspec] : ["push", "-u", remote, refspec];
       log.debug(`pushing ${branch} to ${remote}/${remoteBranch}`);
@@ -140600,14 +140603,15 @@ async function setupGit(params) {
   } catch {
     log.debug("\xBB no existing authentication headers to remove");
   }
+  const originToken = params.bashPermission === "enabled" ? params.token : params.originalToken || params.token;
   if (params.event.is_pr !== true || !params.event.issue_number) {
-    const originUrl2 = `https://x-access-token:${params.token}@github.com/${params.owner}/${params.name}.git`;
+    const originUrl2 = `https://x-access-token:${originToken}@github.com/${params.owner}/${params.name}.git`;
     $("git", ["remote", "set-url", "origin", originUrl2], { cwd: repoDir });
     log.info("\xBB updated origin URL with authentication token");
     return;
   }
   const prNumber = params.event.issue_number;
-  const originUrl = `https://x-access-token:${params.token}@github.com/${params.owner}/${params.name}.git`;
+  const originUrl = `https://x-access-token:${originToken}@github.com/${params.owner}/${params.name}.git`;
   $("git", ["remote", "set-url", "origin", originUrl], { cwd: repoDir });
   const prContext = await checkoutPrBranch({
     octokit: params.octokit,
@@ -140693,6 +140697,8 @@ async function main() {
         });
         await setupGit({
           token: tokenRef.token,
+          originalToken: process.env.ORIGINAL_GITHUB_TOKEN,
+          bashPermission: payload.bash,
           owner: repo.owner,
           name: repo.name,
           event: payload.event,

main.ts

@@ -62,6 +62,8 @@ export async function main(): Promise<MainResult> {
 
     await setupGit({
       token: tokenRef.token,
+      originalToken: process.env.ORIGINAL_GITHUB_TOKEN,
+      bashPermission: payload.bash,
       owner: repo.owner,
       name: repo.name,
       event: payload.event,

mcp/bash.ts

@@ -30,11 +30,9 @@ function filterEnv(isPublicRepo: boolean): Record<string, string> {
     if (isPublicRepo && isSensitive(key)) continue;
     filtered[key] = value;
   }
-  // restore original GITHUB_TOKEN (the one set by GitHub Actions, not our installation token)
-  // this allows git operations in subprocesses to work while keeping our installation token secure
-  if (process.env.ORIGINAL_GITHUB_TOKEN) {
-    filtered.GITHUB_TOKEN = process.env.ORIGINAL_GITHUB_TOKEN;
-  }
+  // never restore GITHUB_TOKEN - agents must use MCP tools for git/gh operations
+  // this ensures all git operations go through auditable MCP tools where we can
+  // enforce branch protection, scan for secrets, etc.
   return filtered;
 }
 

mcp/git.ts

@@ -1,8 +1,8 @@
 import { type } from "arktype";
-import type { ToolContext } from "./server.ts";
 import { log } from "../utils/cli.ts";
 import { containsSecrets } from "../utils/secrets.ts";
 import { $ } from "../utils/shell.ts";
+import type { ToolContext } from "./server.ts";
 import { execute, tool } from "./shared.ts";
 
 export function CreateBranchTool(ctx: ToolContext) {
@@ -141,11 +141,13 @@ export const PushBranch = type({
   force: type.boolean.describe("Force push (use with caution)").default(false),
 });
 
-export function PushBranchTool(_ctx: ToolContext) {
+export function PushBranchTool(ctx: ToolContext) {
+  const defaultBranch = ctx.repo.repo.default_branch || "main";
+
   return tool({
     name: "push_branch",
     description:
-      "Push the current branch (or specified branch) to the remote repository. Git automatically determines the correct remote based on branch config (set by checkout_pr for fork PRs). Never force push unless explicitly requested.",
+      "Push the current branch (or specified branch) to the remote repository. Git automatically determines the correct remote based on branch config (set by checkout_pr for fork PRs). Never force push unless explicitly requested. Pushes to the default branch are blocked.",
     parameters: PushBranch,
     execute: execute(async ({ branchName, force }) => {
       const branch = branchName || $("git", ["rev-parse", "--abbrev-ref", "HEAD"], { log: false });
@@ -168,6 +170,14 @@ export function PushBranchTool(_ctx: ToolContext) {
         // no configured merge ref, use local branch name
       }
 
+      // block pushes to default branch
+      if (remoteBranch === defaultBranch) {
+        throw new Error(
+          `Push blocked: cannot push directly to default branch '${remoteBranch}'. ` +
+            `Create a feature branch and open a PR instead.`
+        );
+      }
+
       // use refspec when local and remote branch names differ
       const refspec = branch === remoteBranch ? branch : `${branch}:${remoteBranch}`;
       const args = force

mcp/reviewComments.ts

@@ -8,6 +8,9 @@ import { execute, tool } from "./shared.ts";
 // fragment for nested replyTo (5 levels deep covers most threads)
 // because in_reply_to_id generally points to the top-level comment
 // this doesn't actually work as expected
+// TOD: implement an API endpoint with aggressive caching that fetches the PR's reviewThreads via graphql
+// separately fetch all the comments associated with the particular review
+// merge them, then construct the full thread context
 const REPLY_TO_FRAGMENT = `
   replyTo {
     databaseId

utils/setup.ts

@@ -2,7 +2,7 @@ import { execSync } from "node:child_process";
 import { mkdtempSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
-import type { PayloadEvent } from "../external.ts";
+import type { BashPermission, PayloadEvent } from "../external.ts";
 import { checkoutPrBranch } from "../mcp/checkout.ts";
 import type { ToolState } from "../mcp/server.ts";
 import { log } from "./cli.ts";
@@ -44,6 +44,8 @@ export function setupTestRepo(options: SetupOptions): void {
 
 interface SetupGitParams {
   token: string;
+  originalToken: string | undefined;
+  bashPermission: BashPermission;
   owner: string;
   name: string;
   event: PayloadEvent;
@@ -127,9 +129,18 @@ export async function setupGit(params: SetupGitParams): Promise<void> {
     log.debug("» no existing authentication headers to remove");
   }
 
+  // choose token for origin based on bash permission:
+  // - enabled: installation token (full access)
+  // - restricted/disabled: workflow token (limited by permissions block)
+  // this protects the base repo while allowing fork PR edits via fork remote
+  const originToken =
+    params.bashPermission === "enabled"
+      ? params.token
+      : (params.originalToken || params.token);
+  
   // non-PR events: set up origin with token, stay on default branch
   if (params.event.is_pr !== true || !params.event.issue_number) {
-    const originUrl = `https://x-access-token:${params.token}@github.com/${params.owner}/${params.name}.git`;
+    const originUrl = `https://x-access-token:${originToken}@github.com/${params.owner}/${params.name}.git`;
     $("git", ["remote", "set-url", "origin", originUrl], { cwd: repoDir });
     log.info("» updated origin URL with authentication token");
     return;
@@ -139,7 +150,7 @@ export async function setupGit(params: SetupGitParams): Promise<void> {
   const prNumber = params.event.issue_number;
 
   // ensure origin is configured with auth token before checkout
-  const originUrl = `https://x-access-token:${params.token}@github.com/${params.owner}/${params.name}.git`;
+  const originUrl = `https://x-access-token:${originToken}@github.com/${params.owner}/${params.name}.git`;
   $("git", ["remote", "set-url", "origin", originUrl], { cwd: repoDir });
 
   // use shared checkout helper (handles fork remotes, push config, etc.)