safe-outputs: pre-flight workflow scope check + full-branch allowed_files validation (#42585)

Author: Copilot

actions/setup/js/copilot_harness.cjs

@@ -715,7 +715,7 @@ async function main() {
   // correct SDK endpoint URI.
   const sdkEnv = buildCopilotSDKEnv();
   const copilotSDKMode = isCopilotSDKEnabled();
-  let copilotConnectionToken;
+  let copilotConnectionToken = "";
   if (copilotSDKMode) {
     // The harness always generates the connection token when SDK mode is active.
     // The token is injected into the driver subprocess env so the harness-managed

actions/setup/js/push_to_pull_request_branch.cjs

@@ -133,17 +133,94 @@ function isWorkflowsScopeRejection(stderr) {
   return lower.includes("`workflows` scope") || lower.includes("workflow can be created or updated due to timeout");
 }
 
+/**
+ * Returns the list of unique workflow file paths (.github/workflows/**) present in the
+ * local branch history beyond the PR's base branch.  This is used as a pre-flight check
+ * before pushing a new branch ref: GitHub rejects such pushes when the token lacks the
+ * 'workflows' scope, even if the current changeset itself does not touch workflow files
+ * (the rejection is based on ALL commits reachable from the pushed ref).
+ *
+ * Uses `origin/${baseBranch}` as the exclusion baseline so that commits already on the
+ * PR's target branch (which GitHub has already accepted) are excluded.  Falls back to
+ * `origin/HEAD` when `baseBranch` is not available, and to an empty array (no workflow
+ * changes detected) when the baseline ref is not resolvable or the git command fails —
+ * in that case the push is still attempted and any real 'workflows' scope rejection will
+ * be caught and surfaced as the typed error downstream.
+ *
+ * Note: `origin/${baseBranch}` and `origin/HEAD` are intentionally different baselines
+ * for their respective layers.  `origin/${baseBranch}` limits detection to commits the
+ * agent actually introduced (correct for the PR delta).  Using `origin/HEAD` here would
+ * traverse commits on the target branch itself for PRs targeting non-default branches,
+ * producing false-positive `workflows_scope_required` errors.
+ *
+ * @param {{ getExecOutput: Function }} exec - @actions/exec module (or compatible mock)
+ * @param {Record<string, any>} gitOptions - Base git exec options (cwd, env, etc.)
+ * @param {string | undefined} baseBranch - PR base branch name (e.g. "main"); falls back to origin/HEAD when not provided
+ * @param {typeof core} coreLogger - Actions core logger used for debug output
+ * @returns {Promise<string[]>} Unique workflow file paths found in the branch history
+ */
+async function detectWorkflowFileChanges(exec, gitOptions, baseBranch, coreLogger) {
+  const baseline = baseBranch && baseBranch.trim() ? `origin/${baseBranch}` : "origin/HEAD";
+  try {
+    const result = await exec.getExecOutput("git", ["log", "--name-only", "--pretty=format:", "HEAD", "--not", baseline, "--", ".github/workflows/"], { ...gitOptions, ignoreReturnCode: true });
+    if (result.exitCode !== 0) {
+      // Non-zero exit means the baseline ref was not resolvable or git failed;
+      // treat as no workflow changes so the push proceeds and any real scope
+      // rejection surfaces downstream.
+      coreLogger.debug(`detectWorkflowFileChanges: git log exited ${result.exitCode} (baseline '${baseline}' may be unavailable); skipping pre-flight`);
+      return [];
+    }
+    return [
+      ...new Set(
+        result.stdout
+          .split("\n")
+          .map(f => f.trim())
+          .filter(Boolean)
+      ),
+    ];
+  } catch (err) {
+    coreLogger.debug(`detectWorkflowFileChanges: git log threw (baseline '${baseline}'); skipping pre-flight: ${err instanceof Error ? err.message : String(err)}`);
+    return [];
+  }
+}
+
+/**
+ * Performs a pre-flight workflow-scope check before pushing a new branch ref.
+ * Returns the typed error object when the branch history contains workflow file changes
+ * and `allowWorkflows` is false; returns null when the push may proceed.
+ *
+ * Extracts the duplicated guard that appears in both the review-branch and
+ * fallback-branch push paths so future changes only need to be made in one place.
+ *
+ * @param {{ getExecOutput: Function }} exec - @actions/exec module (or compatible mock)
+ * @param {Record<string, any>} gitOptions - Base git exec options (cwd, env, etc.)
+ * @param {boolean} allowWorkflows - Whether the push token has the 'workflows' scope
+ * @param {string | undefined} baseBranch - PR base branch name passed through to detectWorkflowFileChanges
+ * @param {string} context - Short label for the push path (e.g. "Review branch", "Fallback branch")
+ * @param {typeof core} coreLogger - Actions core logger
+ * @returns {Promise<{ success: false, error_type: string, error: string } | null>}
+ */
+async function runWorkflowScopePreflightCheck(exec, gitOptions, allowWorkflows, baseBranch, context, coreLogger) {
+  if (allowWorkflows) return null;
+  const workflowFiles = await detectWorkflowFileChanges(exec, gitOptions, baseBranch, coreLogger);
+  if (workflowFiles.length > 0) {
+    coreLogger.info(`Pre-flight check: branch history contains workflow file changes (${workflowFiles.join(", ")}). Failing before push attempt.`);
+    return buildWorkflowsScopeError(`${context} pre-flight`, coreLogger);
+  }
+  return null;
+}
+
 /**
  * Builds the typed result and logs actionable guidance when a branch push fails
  * because the token lacks the 'workflows' scope.
  *
  * @param {string} context - Short label identifying the push path (e.g. "Review branch", "Fallback branch")
- * @param {typeof core} core - Actions core logger
+ * @param {typeof core} coreLogger - Actions core logger
  * @returns {{ success: false, error_type: "workflows_scope_required", error: string }}
  */
-function buildWorkflowsScopeError(context, core) {
-  core.error(`${context} push rejected: the branch includes changes to workflow files (.github/workflows/**) that require the 'workflows' scope on the push token.`);
-  core.error("To allow this workflow to push workflow file changes, configure 'push-to-pull-request-branch.allow-workflows: true' together with a GitHub App in 'safe-outputs.github-app'.");
+function buildWorkflowsScopeError(context, coreLogger) {
+  coreLogger.error(`${context} push rejected: the branch includes changes to workflow files (.github/workflows/**) that require the 'workflows' scope on the push token.`);
+  coreLogger.error("To allow this workflow to push workflow file changes, configure 'push-to-pull-request-branch.allow-workflows: true' together with a GitHub App in 'safe-outputs.github-app'.");
   return {
     success: false,
     error_type: "workflows_scope_required",
@@ -170,6 +247,7 @@ async function main(config = {}) {
   const commitTitleSuffix = config.commit_title_suffix || "";
   const maxSizeKb = parsePositiveInteger(config.max_patch_size) ?? 4096;
   const maxCount = config.max || 0; // 0 means no limit
+  const allowWorkflows = config.allow_workflows === true;
 
   // Cross-repo support: resolve target repository from config
   // This allows pushing to PRs in a different repository than the workflow
@@ -1041,6 +1119,15 @@ async function main(config = {}) {
         // normalizeBranchName to enforce valid git ref characters + max length.
         const reviewBranchName = normalizeBranchName(`${branchName}-review`, String(Date.now()));
         try {
+          // Pre-flight: check full branch history for workflow file changes.
+          // GitHub rejects pushes of new branch refs whose commit history contains
+          // .github/workflows/** changes when the token lacks the 'workflows' scope —
+          // even if the current changeset itself does not touch workflow files.
+          // Failing here avoids leaving the local branch in a renamed state after
+          // a rejected push, and surfaces the error before any side effects.
+          const preflightError = await runWorkflowScopePreflightCheck(exec, baseGitOpts, allowWorkflows, pullRequest?.base?.ref, "Review branch", core);
+          if (preflightError) return preflightError;
+
           // Rename current local branch to review branch
           await exec.exec("git", ["checkout", "-b", reviewBranchName], baseGitOpts);
           core.info(`Created review branch: ${reviewBranchName}`);
@@ -1210,6 +1297,12 @@ async function main(config = {}) {
           const fallbackBranchName = normalizeBranchName(`${branchName}-fallback`, String(Date.now()));
           core.warning(`Non-fast-forward push detected; creating fallback pull request from '${fallbackBranchName}' to '${branchName}'`);
           try {
+            // Pre-flight: check full branch history for workflow file changes.
+            // Like the review branch path, creating a new fallback branch ref triggers
+            // GitHub's scope check on the full commit history, not just the new commits.
+            const preflightError = await runWorkflowScopePreflightCheck(exec, baseGitOpts, allowWorkflows, pullRequest?.base?.ref, "Fallback branch", core);
+            if (preflightError) return preflightError;
+
             await exec.exec("git", ["checkout", "-b", fallbackBranchName], baseGitOpts);
             // Use getExecOutput to capture stderr for 'workflows' scope diagnostics
             const fallbackPushOutput = await exec.getExecOutput("git", ["push", "origin", fallbackBranchName], {

actions/setup/js/push_to_pull_request_branch.test.cjs

@@ -1110,6 +1110,11 @@ index 0000000..abc1234
           return { exitCode: 0, stdout: "1111111111111111111111111111111111111111\trefs/heads/feature-branch\n", stderr: "" };
         }
         if (argList[0] === "log") {
+          // Pre-flight workflow check targets .github/workflows/; return empty to avoid
+          // short-circuiting the fallback path with a workflows_scope_required error.
+          if (argList.includes(".github/workflows/")) {
+            return { exitCode: 0, stdout: "", stderr: "" };
+          }
           return { exitCode: 0, stdout: "Test commit\n", stderr: "" };
         }
         if (argList[0] === "diff-tree") {
@@ -1440,6 +1445,72 @@ index 0000000..abc1234
       expect(result.error_type).toBeUndefined();
       expect(result.error).toContain("Failed to create review PR");
     });
+
+    it("should fail pre-flight with workflows_scope_required when branch history contains workflow files", async () => {
+      process.env.GH_AW_DETECTION_CONCLUSION = "warning";
+      createPatchFile("review-branch-preflight-workflow-files");
+
+      const originalGetExecOutput = mockExec.getExecOutput;
+      mockExec.getExecOutput = vi.fn().mockImplementation(async (cmd, args, options) => {
+        const argList = Array.isArray(args) ? args : [];
+        // Pre-flight git log targets .github/workflows/ directory — returns a workflow
+        // file path to simulate branch history containing .github/workflows/** changes.
+        if (cmd === "git" && argList[0] === "log" && argList.includes(".github/workflows/")) {
+          return { exitCode: 0, stdout: ".github/workflows/ci.yml\n", stderr: "" };
+        }
+        // The git push should NOT be reached — pre-flight check fires first
+        if (cmd === "git" && argList[0] === "push" && argList[1] === "origin") {
+          throw new Error("git push should not be called when pre-flight check fires");
+        }
+        return originalGetExecOutput(cmd, args, options);
+      });
+
+      const module = await loadModule();
+      // allow_workflows not set (default false) — pre-flight check is active
+      const handler = await module.main({});
+      const result = await handler({ branch: "review-branch-preflight-workflow-files" }, {});
+
+      expect(result.success).toBe(false);
+      expect(result.error_type).toBe("workflows_scope_required");
+      expect(result.error).toContain("'workflows' scope");
+      expect(result.error).toContain("allow-workflows");
+      // Pre-flight fires before checkout — no "Failed to create review PR" message
+      const errorCalls = mockCore.error.mock.calls.map(c => c[0]);
+      expect(errorCalls.some(msg => msg.includes("Failed to create review PR"))).toBe(false);
+      expect(mockCore.info).toHaveBeenCalledWith(expect.stringContaining("Pre-flight check"));
+    });
+
+    it("should skip pre-flight check and attempt push when allow_workflows is true", async () => {
+      process.env.GH_AW_DETECTION_CONCLUSION = "warning";
+      createPatchFile("review-branch-allow-workflows-skip-preflight");
+
+      let preflightCalled = false;
+      let pushCalled = false;
+      const originalGetExecOutput = mockExec.getExecOutput;
+      mockExec.getExecOutput = vi.fn().mockImplementation(async (cmd, args, options) => {
+        const argList = Array.isArray(args) ? args : [];
+        if (cmd === "git" && argList[0] === "log" && argList.includes(".github/workflows/")) {
+          preflightCalled = true;
+          return { exitCode: 0, stdout: ".github/workflows/ci.yml\n", stderr: "" };
+        }
+        if (cmd === "git" && argList[0] === "push" && argList[1] === "origin") {
+          pushCalled = true;
+          return { exitCode: 0, stdout: "", stderr: "" };
+        }
+        return originalGetExecOutput(cmd, args, options);
+      });
+
+      const module = await loadModule();
+      // allow_workflows: true — skip the pre-flight check
+      const handler = await module.main({ allow_workflows: true });
+      const result = await handler({ branch: "review-branch-allow-workflows-skip-preflight" }, {});
+
+      // Pre-flight check should NOT have run
+      expect(preflightCalled).toBe(false);
+      // Push should have been attempted
+      expect(pushCalled).toBe(true);
+      expect(result.success).toBe(true);
+    });
   });
 
   // ──────────────────────────────────────────────────────

actions/setup/js/safe_outputs_handlers.cjs

@@ -1250,6 +1250,67 @@ function createHandlers(server, appendSafeOutput, config = {}) {
       pushPinnedSha = null;
     }
 
+    // Full-branch allowed_files check: validate that ALL commits on the PR branch
+    // (relative to origin/baseBranch) only touch files permitted by allowed_files.
+    // The incremental patch check at apply-time only inspects the net diff between
+    // origin/<branch> and the local branch tip; this catches disallowed files that
+    // appear in earlier commits on the branch (e.g. a Copilot branch that also
+    // modified .github/workflows/**) and returns an actionable error to the agent
+    // before any transport artifacts are generated.
+    if (Array.isArray(pushConfig.allowed_files) && pushConfig.allowed_files.length > 0) {
+      try {
+        // Use the pinned SHA as the range head to avoid any TOCTOU window between
+        // the time the SHA was recorded and the time of the git log query.  If no
+        // pinned SHA is available (e.g. non-bundle path), skip the check so we do
+        // not race against a mutable ref; the apply-time check still enforces policy.
+        if (!pushPinnedSha) {
+          server.debug("Full-branch allowed-files check skipped: branch SHA not pinned (non-bundle path)");
+        } else {
+          const branchHistoryFiles = execGitSync(["log", "--name-only", "--pretty=format:", `origin/${baseBranch}..${pushPinnedSha}`, "--"], { cwd: pushGitCwd })
+            .toString()
+            .split("\n")
+            .map(s => s.trim())
+            .filter(Boolean);
+
+          if (branchHistoryFiles.length > 0) {
+            const allowedPatterns = pushConfig.allowed_files.map(p => globPatternToRegex(p));
+            // Files matching excluded_files are intentionally exempt: they will be stripped
+            // from the patch at generation time via :(exclude) pathspecs, so they won't be
+            // present in the final changeset applied to the branch.
+            const excludedPatterns = Array.isArray(pushConfig.excluded_files) ? pushConfig.excluded_files.map(p => globPatternToRegex(p)) : [];
+            const uniqueFiles = [...new Set(branchHistoryFiles)];
+            const disallowedFiles = uniqueFiles.filter(f => !allowedPatterns.some(re => re.test(f)) && !excludedPatterns.some(re => re.test(f)));
+
+            if (disallowedFiles.length > 0) {
+              const sample = disallowedFiles.slice(0, 5);
+              const remaining = disallowedFiles.length - sample.length;
+              const filesStr = remaining > 0 ? `${sample.join(", ")} (+${remaining} more)` : sample.join(", ");
+              server.debug(`Full-branch allowed-files check failed: ${filesStr}`);
+              return {
+                content: [
+                  {
+                    type: "text",
+                    text: JSON.stringify({
+                      result: "error",
+                      error: `Cannot push to pull request branch: the branch '${entry.branch}' history contains commits that modify files outside the allowed-files configuration: ${filesStr}. Remove the disallowed file changes from your commits and retry, or update the allowed-files configuration to include these files.`,
+                      disallowed_files: disallowedFiles,
+                    }),
+                  },
+                ],
+                isError: true,
+              };
+            }
+          }
+        }
+      } catch (fullBranchCheckError) {
+        // Non-fatal: if origin/baseBranch is not available locally or git fails,
+        // skip the full-branch check and continue.  The apply-time policy check in
+        // push_to_pull_request_branch.cjs will still enforce allowed_files against
+        // the incremental patch content.
+        server.debug(`Full-branch allowed-files check skipped (non-fatal): ${getErrorMessage(fullBranchCheckError)}`);
+      }
+    }
+
     // Always generate an incremental patch for policy enforcement (allowed-files/protected-files/excluded-files),
     // even when bundle transport is selected for apply-time commit transport.
     server.debug(`Generating incremental patch for push_to_pull_request_branch with branch: ${entry.branch}, baseBranch: ${baseBranch}`);