aapt2: Ensure shortened paths are not reserved in Windows
It is possible that the shortened resource path is a reserved name in
Windows (see:
https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file).
We rename the path to something that is guaranteed to be NOT reserved.
Bug: 276340505
Test: atest aapt2_tests
Change-Id: Ibc20f10e2e98755a18190a1ba51e0019dd5c1ba0
diff --git a/tools/aapt2/optimize/Obfuscator.cpp b/tools/aapt2/optimize/Obfuscator.cpp
index 8f12f735..903cdf8 100644
--- a/tools/aapt2/optimize/Obfuscator.cpp
+++ b/tools/aapt2/optimize/Obfuscator.cpp
@@ -40,9 +40,9 @@
collapse_key_stringpool_(optimizeOptions.table_flattener_options.collapse_key_stringpool) {
}
-std::string ShortenFileName(android::StringPiece file_path, int output_length) {
+std::string Obfuscator::ShortenFileName(android::StringPiece file_path, int output_length) {
std::size_t hash_num = std::hash<android::StringPiece>{}(file_path);
- std::string result = "";
+ std::string result;
// Convert to (modified) base64 so that it is a proper file path.
for (int i = 0; i < output_length; i++) {
uint8_t sextet = hash_num & 0x3f;
@@ -52,10 +52,33 @@
return result;
}
+static std::string RenameDisallowedFileNames(const std::string& file_name) {
+ // We are renaming shortened file names to make sure they not a reserved file name in Windows.
+ // See: https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file. We are renaming
+ // "COM" and "LPT" too because we are appending a number in case of hash collisions; "COM1",
+ // "COM2", etc. are reserved names.
+ static const char* const reserved_windows_names[] = {"CON", "PRN", "AUX", "NUL", "COM", "LPT"};
+ if (file_name.length() == 3) {
+ // Need to convert the file name to uppercase as Windows is case insensitive. E.g., "NuL",
+ // "nul", and "NUl" are also reserved.
+ std::string result_upper_cased(3, 0);
+ std::transform(file_name.begin(), file_name.end(), result_upper_cased.begin(),
+ [](unsigned char c) { return std::toupper(c); });
+ for (auto reserved_windows_name : reserved_windows_names) {
+ if (result_upper_cased == reserved_windows_name) {
+ // Simple solution to make it a non-reserved name is to add an underscore
+ return "_" + file_name;
+ }
+ }
+ }
+
+ return file_name;
+}
+
// Return the optimal hash length such that at most 10% of resources collide in
// their shortened path.
// Reference: http://matt.might.net/articles/counting-hash-collisions/
-int OptimalShortenedLength(int num_resources) {
+static int OptimalShortenedLength(int num_resources) {
if (num_resources > 4000) {
return 3;
} else {
@@ -63,8 +86,8 @@
}
}
-std::string GetShortenedPath(android::StringPiece shortened_filename,
- android::StringPiece extension, int collision_count) {
+static std::string GetShortenedPath(android::StringPiece shortened_filename,
+ android::StringPiece extension, int collision_count) {
std::string shortened_path = std::string("res/") += shortened_filename;
if (collision_count > 0) {
shortened_path += std::to_string(collision_count);
@@ -82,9 +105,9 @@
}
};
-static bool HandleShortenFilePaths(ResourceTable* table,
- std::map<std::string, std::string>& shortened_path_map,
- const std::set<ResourceName>& path_shorten_exemptions) {
+bool Obfuscator::HandleShortenFilePaths(ResourceTable* table,
+ std::map<std::string, std::string>& shortened_path_map,
+ const std::set<ResourceName>& path_shorten_exemptions) {
// used to detect collisions
std::unordered_set<std::string> shortened_paths;
std::set<FileReference*, PathComparator> file_refs;
@@ -112,7 +135,8 @@
// Android detects ColorStateLists via pathname, skip res/color*
if (util::StartsWith(res_subdir, "res/color")) continue;
- std::string shortened_filename = ShortenFileName(*file_ref->path, num_chars);
+ std::string shortened_filename =
+ RenameDisallowedFileNames(ShortenFileName(*file_ref->path, num_chars));
int collision_count = 0;
std::string shortened_path = GetShortenedPath(shortened_filename, extension, collision_count);
while (shortened_paths.find(shortened_path) != shortened_paths.end()) {