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/*
* Copyright (C) 2022 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 "androidfw/ApkParsing.h"
#include <algorithm>
#include <array>
#include <stdlib.h>
#include <string_view>
#include <sys/types.h>
const std::string_view APK_LIB = "lib/";
const size_t APK_LIB_LEN = APK_LIB.size();
const std::string_view LIB_PREFIX = "/lib";
const size_t LIB_PREFIX_LEN = LIB_PREFIX.size();
const std::string_view LIB_SUFFIX = ".so";
const size_t LIB_SUFFIX_LEN = LIB_SUFFIX.size();
static const std::array<std::string_view, 2> abis = {"arm64-v8a", "x86_64"};
namespace android::util {
const char* ValidLibraryPathLastSlash(const char* fileName, bool suppress64Bit, bool debuggable) {
// Make sure the filename is at least to the minimum library name size.
const size_t fileNameLen = strlen(fileName);
static const size_t minLength = APK_LIB_LEN + 2 + LIB_PREFIX_LEN + 1 + LIB_SUFFIX_LEN;
if (fileNameLen < minLength) {
return nullptr;
}
const char* lastSlash = strrchr(fileName, '/');
if (!lastSlash) {
return nullptr;
}
// Skip directories.
if (*(lastSlash + 1) == 0) {
return nullptr;
}
// Make sure the filename is safe.
if (!isFilenameSafe(lastSlash + 1)) {
return nullptr;
}
// Make sure file starts with 'lib/' prefix.
if (strncmp(fileName, APK_LIB.data(), APK_LIB_LEN) != 0) {
return nullptr;
}
// Make sure there aren't subdirectories by checking if the next / after lib/ is the last slash
if (memchr(fileName + APK_LIB_LEN, '/', fileNameLen - APK_LIB_LEN) != lastSlash) {
return nullptr;
}
if (!debuggable) {
// Make sure the filename starts with lib and ends with ".so".
if (strncmp(fileName + fileNameLen - LIB_SUFFIX_LEN, LIB_SUFFIX.data(), LIB_SUFFIX_LEN) != 0
|| strncmp(lastSlash, LIB_PREFIX.data(), LIB_PREFIX_LEN) != 0) {
return nullptr;
}
}
// Don't include 64 bit versions if they are suppressed
if (suppress64Bit && std::find(abis.begin(), abis.end(), std::string_view(
fileName + APK_LIB_LEN, lastSlash - fileName - APK_LIB_LEN)) != abis.end()) {
return nullptr;
}
return lastSlash;
}
bool isFilenameSafe(const char* filename) {
off_t offset = 0;
for (;;) {
switch (*(filename + offset)) {
case 0:
// Null.
// If we've reached the end, all the other characters are good.
return true;
case 'A' ... 'Z':
case 'a' ... 'z':
case '0' ... '9':
case '+':
case ',':
case '-':
case '.':
case '/':
case '=':
case '_':
offset++;
break;
default:
// We found something that is not good.
return false;
}
}
// Should not reach here.
}
}
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