🧯 fix: Harden Code Env Filepath Uploads (#12936)

* fix: Harden code env filepath uploads

* test: Cover code env filepath edge cases

* fix: Scrub code env fallback filenames

packages/api/src/files/code/form.spec.ts

@@ -31,6 +31,13 @@ describe('code env FormData filenames', () => {
     expect(disposition).toContain('filename="pptx/pptx.py"');
   });
 
+  it('uses filepath for deeply nested safe filenames', () => {
+    expect(getCodeEnvFileOptions('a/b/c/d.py')).toEqual({
+      filename: 'd.py',
+      filepath: 'a/b/c/d.py',
+    });
+  });
+
   it('documents the form-data string overload regression', async () => {
     const disposition = await renderMultipartDisposition((form) => {
       form.append('file', Readable.from(['x']), 'pptx/pptx.py');
@@ -49,4 +56,47 @@ describe('code env FormData filenames', () => {
       filepath: 'pptx/pptx.py',
     });
   });
+
+  it('does not preserve traversal paths as filepath options', async () => {
+    expect(getCodeEnvFileOptions('../../evil.py')).toEqual({ filename: 'evil.py' });
+    expect(getCodeEnvFileOptions('..\\..\\evil.py')).toEqual({ filename: 'evil.py' });
+
+    const disposition = await renderMultipartDisposition((form) => {
+      appendCodeEnvFile(form, Readable.from(['x']), '../../evil.py');
+    });
+
+    expect(disposition).toContain('filename="evil.py"');
+    expect(disposition).not.toContain('../');
+  });
+
+  it('does not preserve absolute paths as filepath options', () => {
+    expect(getCodeEnvFileOptions('/tmp/evil.py')).toEqual({ filename: 'evil.py' });
+    expect(getCodeEnvFileOptions('C:\\tmp\\evil.py')).toEqual({ filename: 'evil.py' });
+  });
+
+  it('does not preserve empty or dot path segments as filepath options', () => {
+    expect(getCodeEnvFileOptions('pptx//pptx.py')).toEqual({ filename: 'pptx.py' });
+    expect(getCodeEnvFileOptions('pptx/./pptx.py')).toEqual({ filename: 'pptx.py' });
+    expect(getCodeEnvFileOptions('pptx/..')).toEqual({ filename: 'file' });
+    expect(getCodeEnvFileOptions('pptx/')).toEqual({ filename: 'pptx' });
+  });
+
+  it('uses safe fallback names for empty or degenerate filenames', () => {
+    expect(getCodeEnvFileOptions('')).toEqual({ filename: 'file' });
+    expect(getCodeEnvFileOptions('.')).toEqual({ filename: 'file' });
+    expect(getCodeEnvFileOptions('..')).toEqual({ filename: 'file' });
+  });
+
+  it('keeps unsafe flat filenames flat instead of rewriting user-visible names', () => {
+    expect(getCodeEnvFileOptions('my notes @ draft.py')).toEqual({
+      filename: 'my notes @ draft.py',
+    });
+  });
+
+  it('scrubs control characters from fallback filenames', () => {
+    expect(getCodeEnvFileOptions('report\nContent-Disposition.py')).toEqual({
+      filename: 'report_Content-Disposition.py',
+    });
+    expect(getCodeEnvFileOptions('../evil\r.py')).toEqual({ filename: 'evil_.py' });
+  });
 });

packages/api/src/files/code/form.ts

@@ -7,16 +7,46 @@ export interface CodeEnvFileOptions {
   filepath?: string;
 }
 
+const CODE_ENV_SAFE_FILEPATH_PATTERN = /^[a-zA-Z0-9._\-/]+$/;
+const CODE_ENV_FILENAME_CONTROL_CHARS_PATTERN = /[\x00-\x1f\x7f]/g;
+
+function isSafeCodeEnvFilepath(filepath: string): boolean {
+  if (!filepath || filepath.startsWith('/') || !CODE_ENV_SAFE_FILEPATH_PATTERN.test(filepath)) {
+    return false;
+  }
+
+  const segments = filepath.split('/');
+  return segments.every((segment) => segment !== '' && segment !== '.' && segment !== '..');
+}
+
+function getCodeEnvBasename(filepath: string): string {
+  const basename = getSafeCodeEnvFilename(path.posix.basename(filepath));
+
+  if (!basename || basename === '.' || basename === '..') {
+    return 'file';
+  }
+
+  return basename;
+}
+
+function getSafeCodeEnvFilename(filename: string): string {
+  return filename.replace(CODE_ENV_FILENAME_CONTROL_CHARS_PATTERN, '_');
+}
+
 /**
  * Uses `filepath` for nested names because `form-data` strips directories from
- * the bare string filename overload before codeapi can preserve them.
+ * the bare string filename overload before codeapi can preserve safe paths.
  */
 export function getCodeEnvFileOptions(filename: string): CodeEnvFileOptions {
   const normalized = filename.replace(/\\/g, '/');
-  const basename = path.posix.basename(normalized);
+  const basename = getCodeEnvBasename(normalized);
 
-  if (normalized === basename) {
-    return { filename };
+  if (normalized === filename && filename === basename) {
+    return { filename: getSafeCodeEnvFilename(filename) };
+  }
+
+  if (!isSafeCodeEnvFilepath(normalized)) {
+    return { filename: basename };
   }
 
   return { filename: basename, filepath: normalized };