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Commit c7694036 authored by Mohamed Heikal's avatar Mohamed Heikal
Browse files

Resource Path Obfuscation 

This CL allows aapt2 to obfuscate resource paths within the output apk
and move resources to shorter obfuscated paths. This reduces apk size
when there is a large number of resources since the path metadata exists
in 4 places in the apk.

This CL adds two arguments to aapt2, one to enable resource path
obfuscation and one to point to a path to output the path map to (for
later debugging).

Test: make aapt2_tests
Bug: b/75965637

Change-Id: I9cacafe1d17800d673566b2d61b0b88f3fb8d60c
parent 9da2ff0f

tools/aapt2/Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ cc_library_host_static { 
        "optimize/MultiApkGenerator.cpp",

        "optimize/ResourceDeduper.cpp",

        "optimize/ResourceFilter.cpp",

        "optimize/ResourcePathShortener.cpp",

        "optimize/VersionCollapser.cpp",

        "process/SymbolTable.cpp",

        "split/TableSplitter.cpp",

tools/aapt2/LoadedApk.cpp

+12 −2
Original line number Diff line number Diff line
@@ -223,8 +223,17 @@ bool LoadedApk::WriteToArchive(IAaptContext* context, ResourceTable* split_table 
    io::IFile* file = iterator->Next();

    std::string path = file->GetSource().path;



    std::string output_path = path;

    bool is_resource = path.find("res/") == 0;

    if (is_resource) {

      auto it = options.shortened_path_map.find(path);

      if (it != options.shortened_path_map.end()) {

        output_path = it->second;

      }

    }



    // Skip resources that are not referenced if requested.

    if (path.find("res/") == 0 && referenced_resources.find(path) == referenced_resources.end()) {

    if (is_resource && referenced_resources.find(output_path) == referenced_resources.end()) {

      if (context->IsVerbose()) {

        context->GetDiagnostics()->Note(DiagMessage()

                                        << "Removing resource '" << path << "' from APK.");
@@ -283,7 +292,8 @@ bool LoadedApk::WriteToArchive(IAaptContext* context, ResourceTable* split_table 
        return false;

      }

    } else {

      if (!io::CopyFileToArchivePreserveCompression(context, file, path, writer)) {

      if (!io::CopyFileToArchivePreserveCompression(

              context, file, output_path, writer)) {

        return false;

      }

    }

tools/aapt2/cmd/Optimize.cpp

+26 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ 
#include "optimize/MultiApkGenerator.h"

#include "optimize/ResourceDeduper.h"

#include "optimize/ResourceFilter.h"

#include "optimize/ResourcePathShortener.h"

#include "optimize/VersionCollapser.h"

#include "split/TableSplitter.h"

#include "util/Files.h"
@@ -52,6 +53,7 @@ using ::android::ConfigDescription; 
using ::android::ResTable_config;

using ::android::StringPiece;

using ::android::base::ReadFileToString;

using ::android::base::WriteStringToFile;

using ::android::base::StringAppendF;

using ::android::base::StringPrintf;
@@ -143,6 +145,21 @@ class Optimizer { 
      return 1;

    }



    if (options_.shorten_resource_paths) {

      ResourcePathShortener shortener(options_.table_flattener_options.shortened_path_map);

      if (!shortener.Consume(context_, apk->GetResourceTable())) {

        context_->GetDiagnostics()->Error(DiagMessage() << "failed shortening resource paths");

        return 1;

      }

      if (options_.shortened_paths_map_path

          && !WriteShortenedPathsMap(options_.table_flattener_options.shortened_path_map,

                                      options_.shortened_paths_map_path.value())) {

        context_->GetDiagnostics()->Error(DiagMessage()

                                          << "failed to write shortened resource paths to file");

        return 1;

      }

    }



    // Adjust the SplitConstraints so that their SDK version is stripped if it is less than or

    // equal to the minSdk.

    options_.split_constraints =
@@ -264,6 +281,15 @@ class Optimizer { 
                                        ArchiveEntry::kAlign, writer);

  }



  bool WriteShortenedPathsMap(const std::map<std::string, std::string> &path_map,

                               const std::string &file_path) {

    std::stringstream ss;

    for (auto it = path_map.cbegin(); it != path_map.cend(); ++it) {

      ss << it->first << " -> " << it->second << "\n";

    }

    return WriteStringToFile(ss.str(), file_path);

  }



  OptimizeOptions options_;

  OptimizeContext* context_;

};

tools/aapt2/cmd/Optimize.h

+16 −1
Original line number Diff line number Diff line
@@ -55,6 +55,12 @@ struct OptimizeOptions { 
  // Set of artifacts to keep when generating multi-APK splits. If the list is empty, all artifacts

  // are kept and will be written as output.

  std::unordered_set<std::string> kept_artifacts;



  // Whether or not to shorten resource paths in the APK.

  bool shorten_resource_paths;



  // Path to the output map of original resource paths to shortened paths.

  Maybe<std::string> shortened_paths_map_path;

};



class OptimizeCommand : public Command {
@@ -100,6 +106,12 @@ class OptimizeCommand : public Command { 
    AddOptionalSwitch("--enable-resource-obfuscation",

        "Enables obfuscation of key string pool to single value",

        &options_.table_flattener_options.collapse_key_stringpool);

    AddOptionalSwitch("--enable-resource-path-shortening",

        "Enables shortening of the path of the resources inside the APK.",

        &options_.shorten_resource_paths);

    AddOptionalFlag("--resource-path-shortening-map",

        "Path to output the map of old resource paths to shortened paths.",

        &options_.shortened_paths_map_path);

    AddOptionalSwitch("-v", "Enables verbose logging", &verbose_);

  }
@@ -108,6 +120,9 @@ class OptimizeCommand : public Command { 
 private:

  OptimizeOptions options_;



  bool WriteObfuscatedPathsMap(const std::map<std::string, std::string> &path_map,

                               const std::string &file_path);



  Maybe<std::string> config_path_;

  Maybe<std::string> whitelist_path_;

  Maybe<std::string> resources_config_path_;

tools/aapt2/format/binary/TableFlattener.h

+3 −0
Original line number Diff line number Diff line
@@ -46,6 +46,9 @@ struct TableFlattenerOptions { 


  // When true, sort the entries in the values string pool by priority and configuration.

  bool sort_stringpool_entries = true;



  // Map from original resource paths to shortened resource paths.

  std::map<std::string, std::string> shortened_path_map;

};



class TableFlattener : public IResourceTableConsumer {