flutter_flutter/dev/a11y_assessments
David Bebawy 99e01e108a
fix(windows): use wcsnlen for defensive programming (CWE-126) (#180419)
## Description

This PR replaces `wcslen` with `wcsnlen` in the Windows runner template
and all example/dev/integration test files to address CWE-126 (Buffer
Over-read) flagged by static analysis tools (Semgrep/GitLab SAST).

## Changes

The `Utf8FromUtf16` function now uses `wcsnlen` with the
`UNICODE_STRING_MAX_CHARS` constant (32767) as the maximum length,
providing defensive programming against potential buffer over-reads.

**Key improvements:**
1. Calculate `input_length` **first** using `wcsnlen(utf16_string,
UNICODE_STRING_MAX_CHARS)`
2. Use that bounded length for **both** `WideCharToMultiByte` calls
(eliminates the `-1` unbounded read)
3. Remove the `-1` adjustment since explicit length excludes null
terminator
4. Use `static_cast` instead of C-style casts per Google C++ Style Guide

## Test Coverage

Added comprehensive edge case tests for `Utf8FromUtf16` in
`windows_startup_test`:
- **nullptr input**: Verifies function returns empty string
- **Empty string input**: Verifies function returns empty string  
- **Invalid UTF-16 (unpaired surrogate)**: Verifies function handles
malformed input gracefully

These tests address reviewer feedback from @loic-sharma requesting
coverage for corner cases.

## Files Updated

**Template (source of truth):**
- `packages/flutter_tools/templates/app/windows.tmpl/runner/utils.cpp`

**Integration tests (4 files):**
- `dev/integration_tests/flutter_gallery/windows/runner/utils.cpp`
- `dev/integration_tests/ui/windows/runner/utils.cpp`
- `dev/integration_tests/windowing_test/windows/runner/utils.cpp`
- `dev/integration_tests/windows_startup_test/windows/runner/utils.cpp`

**Examples and dev apps (10 files):**
- `examples/hello_world/windows/runner/utils.cpp`
- `examples/layers/windows/runner/utils.cpp`
- `examples/platform_view/windows/runner/utils.cpp`
- `examples/flutter_view/windows/runner/utils.cpp`
- `examples/platform_channel/windows/runner/utils.cpp`
- `examples/api/windows/runner/utils.cpp`
- `examples/multiple_windows/windows/runner/utils.cpp`
- `dev/manual_tests/windows/runner/utils.cpp`
- `dev/benchmarks/complex_layout/windows/runner/utils.cpp`
- `dev/a11y_assessments/windows/runner/utils.cpp`

**Test files (4 files):**
-
`dev/integration_tests/windows_startup_test/windows/runner/flutter_window.cpp`
- `dev/integration_tests/windows_startup_test/lib/main.dart`
- `dev/integration_tests/windows_startup_test/lib/windows.dart`
-
`dev/integration_tests/windows_startup_test/test_driver/main_test.dart`

## Rationale

While the Windows API guarantees null-termination for strings returned
by `CommandLineToArgvW`, using `wcsnlen` with an explicit bound is a
defensive programming best practice that:
- Satisfies static analysis tools
- Provides an extra safety layer
- Follows the principle of defense in depth

The limit of 32767 (`UNICODE_STRING_MAX_CHARS`) is the maximum length of
a `UNICODE_STRING` structure and is far beyond any realistic
command-line argument length.

## Related Issues

Fixes https://github.com/flutter/flutter/issues/180418

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and labeled this PR with
`severe: API break` if it contains a breaking change.
- [x] All existing and new tests are passing.

[Contributor Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[breaking change policy]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#breaking-changes
2026-01-16 18:21:15 +00:00
..

a11y_assessments

This app is used for internal testing.

Release a new version for Android

pre-requisite: This can and should only be done by a googler and you must also be in the flutter.dev play console account.

  1. Follow https://docs.flutter.dev/deployment/android to create a keystore file if you don't already have one.

  2. Bump the pubspec.yaml version

  3. Create a key.properties file in android/ directory following this format.

storePassword=<password>
keyPassword=<password>
keyAlias=upload
storeFile=<keystore path>
  1. Run flutter build appbundle and upload the artifact to play console

Release a new version for iOS

pre-requisite: This can and should only be done by a googler and you must also be in the FLUTTER.IO LLC developer account with iOS distribution permission.

  1. Bump the pubspec.yaml version
  2. Run flutter build ipa and upload the artifact to app store using transporter or other tools. For more information, see https://docs.flutter.dev/deployment/ios.
  3. Once the app is in TestFlight, add appropriate testers to the app so they can start testing.