core/libnativeloader/native_loader.cpp

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "nativeloader/native_loader.h"
#include "ScopedUtfChars.h"

#include <dlfcn.h>
#ifdef __ANDROID__
#define LOG_TAG "libnativeloader"
#include "nativeloader/dlext_namespaces.h"
#include "cutils/properties.h"
#include "log/log.h"
#endif
#include "nativebridge/native_bridge.h"

#include <algorithm>
#include <vector>
#include <string>
#include <mutex>

#include <android-base/file.h>
#include <android-base/macros.h>
#include <android-base/strings.h>

#define CHECK(predicate) LOG_ALWAYS_FATAL_IF(!(predicate),\
                                             "%s:%d: %s CHECK '" #predicate "' failed.",\
                                             __FILE__, __LINE__, __FUNCTION__)

namespace android {

#if defined(__ANDROID__)
class NativeLoaderNamespace {
 public:
  NativeLoaderNamespace()
      : android_ns_(nullptr), native_bridge_ns_(nullptr) { }

  explicit NativeLoaderNamespace(android_namespace_t* ns)
      : android_ns_(ns), native_bridge_ns_(nullptr) { }

  explicit NativeLoaderNamespace(native_bridge_namespace_t* ns)
      : android_ns_(nullptr), native_bridge_ns_(ns) { }

  NativeLoaderNamespace(NativeLoaderNamespace&& that) = default;
  NativeLoaderNamespace(const NativeLoaderNamespace& that) = default;

  NativeLoaderNamespace& operator=(const NativeLoaderNamespace& that) = default;

  android_namespace_t* get_android_ns() const {
    CHECK(native_bridge_ns_ == nullptr);
    return android_ns_;
  }

  native_bridge_namespace_t* get_native_bridge_ns() const {
    CHECK(android_ns_ == nullptr);
    return native_bridge_ns_;
  }

  bool is_android_namespace() const {
    return native_bridge_ns_ == nullptr;
  }

 private:
  // Only one of them can be not null
  android_namespace_t* android_ns_;
  native_bridge_namespace_t* native_bridge_ns_;
};

static constexpr const char* kPublicNativeLibrariesSystemConfigPathFromRoot =
                                  "/etc/public.libraries.txt";
static constexpr const char* kPublicNativeLibrariesVendorConfig =
                                  "/vendor/etc/public.libraries.txt";

// (http://b/27588281) This is a workaround for apps using custom classloaders and calling
// System.load() with an absolute path which is outside of the classloader library search path.
// This list includes all directories app is allowed to access this way.
static constexpr const char* kWhitelistedDirectories = "/data:/mnt/expand";

static bool is_debuggable() {
  char debuggable[PROP_VALUE_MAX];
  property_get("ro.debuggable", debuggable, "0");
  return std::string(debuggable) == "1";
}

class LibraryNamespaces {
 public:
  LibraryNamespaces() : initialized_(false) { }

  bool Create(JNIEnv* env,
              jobject class_loader,
              bool is_shared,
              jstring java_library_path,
              jstring java_permitted_path,
              NativeLoaderNamespace* ns,
              std::string* error_msg) {
    std::string library_path; // empty string by default.

    if (java_library_path != nullptr) {
      ScopedUtfChars library_path_utf_chars(env, java_library_path);
      library_path = library_path_utf_chars.c_str();
    }

    // (http://b/27588281) This is a workaround for apps using custom
    // classloaders and calling System.load() with an absolute path which
    // is outside of the classloader library search path.
    //
    // This part effectively allows such a classloader to access anything
    // under /data and /mnt/expand
    std::string permitted_path = kWhitelistedDirectories;

    if (java_permitted_path != nullptr) {
      ScopedUtfChars path(env, java_permitted_path);
      if (path.c_str() != nullptr && path.size() > 0) {
        permitted_path = permitted_path + ":" + path.c_str();
      }
    }

    if (!initialized_ && !InitPublicNamespace(library_path.c_str(), error_msg)) {
      return false;
    }

    bool found = FindNamespaceByClassLoader(env, class_loader, nullptr);

    LOG_ALWAYS_FATAL_IF(found,
                        "There is already a namespace associated with this classloader");

    uint64_t namespace_type = ANDROID_NAMESPACE_TYPE_ISOLATED;
    if (is_shared) {
      namespace_type |= ANDROID_NAMESPACE_TYPE_SHARED;
    }

    NativeLoaderNamespace parent_ns;
    bool found_parent_namespace = FindParentNamespaceByClassLoader(env, class_loader, &parent_ns);

    bool is_native_bridge = false;

    if (found_parent_namespace) {
      is_native_bridge = !parent_ns.is_android_namespace();
    } else if (!library_path.empty()) {
      is_native_bridge = NativeBridgeIsPathSupported(library_path.c_str());
    }

    NativeLoaderNamespace native_loader_ns;
    if (!is_native_bridge) {
      android_namespace_t* ns = android_create_namespace("classloader-namespace",
                                                         nullptr,
                                                         library_path.c_str(),
                                                         namespace_type,
                                                         permitted_path.c_str(),
                                                         parent_ns.get_android_ns());
      if (ns == nullptr) {
        *error_msg = dlerror();
        return false;
      }

      native_loader_ns = NativeLoaderNamespace(ns);
    } else {
      native_bridge_namespace_t* ns = NativeBridgeCreateNamespace("classloader-namespace",
                                                                  nullptr,
                                                                  library_path.c_str(),
                                                                  namespace_type,
                                                                  permitted_path.c_str(),
                                                                  parent_ns.get_native_bridge_ns());
      if (ns == nullptr) {
        *error_msg = NativeBridgeGetError();
        return false;
      }

      native_loader_ns = NativeLoaderNamespace(ns);
    }

    namespaces_.push_back(std::make_pair(env->NewWeakGlobalRef(class_loader), native_loader_ns));

    *ns = native_loader_ns;
    return true;
  }

  bool FindNamespaceByClassLoader(JNIEnv* env, jobject class_loader, NativeLoaderNamespace* ns) {
    auto it = std::find_if(namespaces_.begin(), namespaces_.end(),
                [&](const std::pair<jweak, NativeLoaderNamespace>& value) {
                  return env->IsSameObject(value.first, class_loader);
                });
    if (it != namespaces_.end()) {
      if (ns != nullptr) {
        *ns = it->second;
      }

      return true;
    }

    return false;
  }

  void Initialize() {
    // Once public namespace is initialized there is no
    // point in running this code - it will have no effect
    // on the current list of public libraries.
    if (initialized_) {
      return;
    }

    std::vector<std::string> sonames;
    const char* android_root_env = getenv("ANDROID_ROOT");
    std::string root_dir = android_root_env != nullptr ? android_root_env : "/system";
    std::string public_native_libraries_system_config =
            root_dir + kPublicNativeLibrariesSystemConfigPathFromRoot;

    std::string error_msg;
    LOG_ALWAYS_FATAL_IF(!ReadConfig(public_native_libraries_system_config, &sonames, &error_msg),
                        "Error reading public native library list from \"%s\": %s",
                        public_native_libraries_system_config.c_str(), error_msg.c_str());

    // For debuggable platform builds use ANDROID_ADDITIONAL_PUBLIC_LIBRARIES environment
    // variable to add libraries to the list. This is intended for platform tests only.
    if (is_debuggable()) {
      const char* additional_libs = getenv("ANDROID_ADDITIONAL_PUBLIC_LIBRARIES");
      if (additional_libs != nullptr && additional_libs[0] != '\0') {
        std::vector<std::string> additional_libs_vector = base::Split(additional_libs, ":");
        std::copy(additional_libs_vector.begin(),
                  additional_libs_vector.end(),
                  std::back_inserter(sonames));
      }
    }

    // This file is optional, quietly ignore if the file does not exist.
    ReadConfig(kPublicNativeLibrariesVendorConfig, &sonames);

    // android_init_namespaces() expects all the public libraries
    // to be loaded so that they can be found by soname alone.
    //
    // TODO(dimitry): this is a bit misleading since we do not know
    // if the vendor public library is going to be opened from /vendor/lib
    // we might as well end up loading them from /system/lib
    // For now we rely on CTS test to catch things like this but
    // it should probably be addressed in the future.
    for (const auto& soname : sonames) {
      LOG_ALWAYS_FATAL_IF(dlopen(soname.c_str(), RTLD_NOW | RTLD_NODELETE) == nullptr,
                          "Error preloading public library %s: %s",
                          soname.c_str(), dlerror());
    }

    public_libraries_ = base::Join(sonames, ':');
  }

  void Reset() {
    namespaces_.clear();
  }

 private:
  bool ReadConfig(const std::string& configFile, std::vector<std::string>* sonames,
                  std::string* error_msg = nullptr) {
    // Read list of public native libraries from the config file.
    std::string file_content;
    if(!base::ReadFileToString(configFile, &file_content)) {
      if (error_msg) *error_msg = strerror(errno);
      return false;
    }

    std::vector<std::string> lines = base::Split(file_content, "\n");

    for (auto& line : lines) {
      auto trimmed_line = base::Trim(line);
      if (trimmed_line[0] == '#' || trimmed_line.empty()) {
        continue;
      }
      size_t space_pos = trimmed_line.rfind(' ');
      if (space_pos != std::string::npos) {
        std::string type = trimmed_line.substr(space_pos + 1);
        if (type != "32" && type != "64") {
          if (error_msg) *error_msg = "Malformed line: " + line;
          return false;
        }
#if defined(__LP64__)
        // Skip 32 bit public library.
        if (type == "32") {
          continue;
        }
#else
        // Skip 64 bit public library.
        if (type == "64") {
          continue;
        }
#endif
        trimmed_line.resize(space_pos);
      }

      sonames->push_back(trimmed_line);
    }

    return true;
  }

  bool InitPublicNamespace(const char* library_path, std::string* error_msg) {
    // Ask native bride if this apps library path should be handled by it
    bool is_native_bridge = NativeBridgeIsPathSupported(library_path);

    // (http://b/25844435) - Some apps call dlopen from generated code (mono jited
    // code is one example) unknown to linker in which  case linker uses anonymous
    // namespace. The second argument specifies the search path for the anonymous
    // namespace which is the library_path of the classloader.
    initialized_ = android_init_namespaces(public_libraries_.c_str(),
                                           is_native_bridge ? nullptr : library_path);
    if (!initialized_) {
      *error_msg = dlerror();
      return false;
    }

    // and now initialize native bridge namespaces if necessary.
    if (NativeBridgeInitialized()) {
      initialized_ = NativeBridgeInitNamespace(public_libraries_.c_str(),
                                               is_native_bridge ? library_path : nullptr);
      if (!initialized_) {
        *error_msg = NativeBridgeGetError();
      }
    }

    return initialized_;
  }

  jobject GetParentClassLoader(JNIEnv* env, jobject class_loader) {
    jclass class_loader_class = env->FindClass("java/lang/ClassLoader");
    jmethodID get_parent = env->GetMethodID(class_loader_class,
                                            "getParent",
                                            "()Ljava/lang/ClassLoader;");

    return env->CallObjectMethod(class_loader, get_parent);
  }

  bool FindParentNamespaceByClassLoader(JNIEnv* env,
                                        jobject class_loader,
                                        NativeLoaderNamespace* ns) {
    jobject parent_class_loader = GetParentClassLoader(env, class_loader);

    while (parent_class_loader != nullptr) {
      if (FindNamespaceByClassLoader(env, parent_class_loader, ns)) {
        return true;
      }

      parent_class_loader = GetParentClassLoader(env, parent_class_loader);
    }

    return false;
  }

  bool initialized_;
  std::vector<std::pair<jweak, NativeLoaderNamespace>> namespaces_;
  std::string public_libraries_;


  DISALLOW_COPY_AND_ASSIGN(LibraryNamespaces);
};

static std::mutex g_namespaces_mutex;
static LibraryNamespaces* g_namespaces = new LibraryNamespaces;
#endif

void InitializeNativeLoader() {
#if defined(__ANDROID__)
  std::lock_guard<std::mutex> guard(g_namespaces_mutex);
  g_namespaces->Initialize();
#endif
}

void ResetNativeLoader() {
#if defined(__ANDROID__)
  std::lock_guard<std::mutex> guard(g_namespaces_mutex);
  g_namespaces->Reset();
#endif
}

jstring CreateClassLoaderNamespace(JNIEnv* env,
                                   int32_t target_sdk_version,
                                   jobject class_loader,
                                   bool is_shared,
                                   jstring library_path,
                                   jstring permitted_path) {
#if defined(__ANDROID__)
  UNUSED(target_sdk_version);
  std::lock_guard<std::mutex> guard(g_namespaces_mutex);

  std::string error_msg;
  NativeLoaderNamespace ns;
  bool success = g_namespaces->Create(env,
                                      class_loader,
                                      is_shared,
                                      library_path,
                                      permitted_path,
                                      &ns,
                                      &error_msg);
  if (!success) {
    return env->NewStringUTF(error_msg.c_str());
  }
#else
  UNUSED(env, target_sdk_version, class_loader, is_shared,
         library_path, permitted_path);
#endif
  return nullptr;
}

void* OpenNativeLibrary(JNIEnv* env,
                        int32_t target_sdk_version,
                        const char* path,
                        jobject class_loader,
                        jstring library_path,
                        bool* needs_native_bridge,
                        std::string* error_msg) {
#if defined(__ANDROID__)
  UNUSED(target_sdk_version);
  if (class_loader == nullptr) {
    *needs_native_bridge = false;
    return dlopen(path, RTLD_NOW);
  }

  std::lock_guard<std::mutex> guard(g_namespaces_mutex);
  NativeLoaderNamespace ns;

  if (!g_namespaces->FindNamespaceByClassLoader(env, class_loader, &ns)) {
    // This is the case where the classloader was not created by ApplicationLoaders
    // In this case we create an isolated not-shared namespace for it.
    if (!g_namespaces->Create(env, class_loader, false, library_path, nullptr, &ns, error_msg)) {
      return nullptr;
    }
  }

  if (ns.is_android_namespace()) {
    android_dlextinfo extinfo;
    extinfo.flags = ANDROID_DLEXT_USE_NAMESPACE;
    extinfo.library_namespace = ns.get_android_ns();

    void* handle = android_dlopen_ext(path, RTLD_NOW, &extinfo);
    if (handle == nullptr) {
      *error_msg = dlerror();
    }
    *needs_native_bridge = false;
    return handle;
  } else {
    void* handle = NativeBridgeLoadLibraryExt(path, RTLD_NOW, ns.get_native_bridge_ns());
    if (handle == nullptr) {
      *error_msg = NativeBridgeGetError();
    }
    *needs_native_bridge = true;
    return handle;
  }
#else
  UNUSED(env, target_sdk_version, class_loader, library_path);
  *needs_native_bridge = false;
  void* handle = dlopen(path, RTLD_NOW);
  if (handle == nullptr) {
    if (NativeBridgeIsSupported(path)) {
      *needs_native_bridge = true;
      handle = NativeBridgeLoadLibrary(path, RTLD_NOW);
      if (handle == nullptr) {
        *error_msg = NativeBridgeGetError();
      }
    } else {
      *needs_native_bridge = false;
      *error_msg = dlerror();
    }
  }
  return handle;
#endif
}

bool CloseNativeLibrary(void* handle, const bool needs_native_bridge) {
    return needs_native_bridge ? NativeBridgeUnloadLibrary(handle) :
                                 dlclose(handle);
}

#if defined(__ANDROID__)
// native_bridge_namespaces are not supported for callers of this function.
// This function will return nullptr in the case when application is running
// on native bridge.
android_namespace_t* FindNamespaceByClassLoader(JNIEnv* env, jobject class_loader) {
  std::lock_guard<std::mutex> guard(g_namespaces_mutex);
  NativeLoaderNamespace ns;
  if (g_namespaces->FindNamespaceByClassLoader(env, class_loader, &ns)) {
    return ns.is_android_namespace() ? ns.get_android_ns() : nullptr;
  }

  return nullptr;
}
#endif

}; //  android namespace