fix(selfhost): bound config lint file reads

scripts/gittensory-config-lint.ts

@@ -2,9 +2,10 @@
 // Wires up the previously-unwired src/selfhost/config-lint.ts validator (#2906): a self-hoster (or the
 // maintainer, dogfooding on JSONbored/gittensory) can now actually run it against a real .gittensory.yml or
 // private-config file and get actionable feedback, instead of the validator existing only in its own test suite.
-import { existsSync, readFileSync } from "node:fs";
+import { lstatSync, readFileSync } from "node:fs";
 import { pathToFileURL } from "node:url";
 import { lintManifestText, type SelfHostConfigLintResult } from "../src/selfhost/config-lint";
+import { MAX_FOCUS_MANIFEST_BYTES } from "../src/signals/focus-manifest";
 
 function usage(): string {
   return `Usage: npm run selfhost:config-lint -- [path]
@@ -17,6 +18,24 @@ Options:
   path   Manifest file to lint. Defaults to ".gittensory.yml" in the current directory.`;
 }
 
+export function readManifestTextForLint(path: string): string {
+  let stat;
+  try {
+    stat = lstatSync(path);
+  } catch (error) {
+    if (error && typeof error === "object" && "code" in error && error.code === "ENOENT") {
+      throw new Error(`no such file: ${path}`);
+    }
+    throw error;
+  }
+  if (stat.isSymbolicLink()) throw new Error(`refusing to read symlink: ${path}`);
+  if (!stat.isFile()) throw new Error(`not a regular file: ${path}`);
+  if (stat.size > MAX_FOCUS_MANIFEST_BYTES) {
+    throw new Error(`file exceeds ${MAX_FOCUS_MANIFEST_BYTES} bytes: ${path}`);
+  }
+  return readFileSync(path, "utf8");
+}
+
 export function formatLintReport(path: string, result: SelfHostConfigLintResult): string {
   const lines = [`${path}: ${result.summary}`];
   if (result.recognizedFields.length > 0) lines.push(`  recognized fields: ${result.recognizedFields.join(", ")}`);
@@ -32,11 +51,14 @@ function main(): void {
     return;
   }
   const path = args[0] ?? ".gittensory.yml";
-  if (!existsSync(path)) {
-    console.error(`gittensory-config-lint: no such file: ${path}\n\n${usage()}`);
+  let text;
+  try {
+    text = readManifestTextForLint(path);
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    console.error(`gittensory-config-lint: ${message}\n\n${usage()}`);
     process.exit(1);
   }
-  const text = readFileSync(path, "utf8");
   const result = lintManifestText(text);
   console.log(formatLintReport(path, result));
   if (!result.ok) process.exit(1);

test/unit/gittensory-config-lint-script.test.ts

@@ -1,6 +1,10 @@
+import { mkdtempSync, mkdirSync, rmSync, symlinkSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import { describe, expect, it } from "vitest";
-import { formatLintReport } from "../../scripts/gittensory-config-lint";
+import { formatLintReport, readManifestTextForLint } from "../../scripts/gittensory-config-lint";
 import { lintManifestText } from "../../src/selfhost/config-lint";
+import { MAX_FOCUS_MANIFEST_BYTES } from "../../src/signals/focus-manifest";
 
 describe("formatLintReport (#2906)", () => {
   it("reports a valid manifest's summary and recognized fields, no warnings", () => {
@@ -34,3 +38,60 @@ describe("formatLintReport (#2906)", () => {
     );
   });
 });
+
+describe("readManifestTextForLint (#2923 regression)", () => {
+  function withTempDir(run: (dir: string) => void): void {
+    const dir = mkdtempSync(join(tmpdir(), "gittensory-config-lint-"));
+    try {
+      run(dir);
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  }
+
+  it("reads a regular manifest file at or below the parser byte limit", () => {
+    withTempDir((dir) => {
+      const path = join(dir, "manifest.yml");
+      writeFileSync(path, "wantedPaths:\n  - src/\n");
+
+      expect(readManifestTextForLint(path)).toBe("wantedPaths:\n  - src/\n");
+    });
+  });
+
+  it("rejects missing paths before attempting to read", () => {
+    withTempDir((dir) => {
+      const path = join(dir, "missing.yml");
+
+      expect(() => readManifestTextForLint(path)).toThrow(`no such file: ${path}`);
+    });
+  });
+
+  it("rejects symlinks so repository-controlled manifests cannot target special files", () => {
+    withTempDir((dir) => {
+      const target = join(dir, "target.yml");
+      const link = join(dir, "manifest.yml");
+      writeFileSync(target, "wantedPaths:\n  - src/\n");
+      symlinkSync(target, link);
+
+      expect(() => readManifestTextForLint(link)).toThrow(`refusing to read symlink: ${link}`);
+    });
+  });
+
+  it("rejects non-regular files before reading", () => {
+    withTempDir((dir) => {
+      const manifestDir = join(dir, "manifest.yml");
+      mkdirSync(manifestDir);
+
+      expect(() => readManifestTextForLint(manifestDir)).toThrow(`not a regular file: ${manifestDir}`);
+    });
+  });
+
+  it("rejects oversized regular files before loading their contents", () => {
+    withTempDir((dir) => {
+      const path = join(dir, "manifest.yml");
+      writeFileSync(path, "a".repeat(MAX_FOCUS_MANIFEST_BYTES + 1));
+
+      expect(() => readManifestTextForLint(path)).toThrow(`file exceeds ${MAX_FOCUS_MANIFEST_BYTES} bytes: ${path}`);
+    });
+  });
+});