Magisk/native/jni/systemproperties/contexts_serialized.cpp
2018-09-27 03:30:16 -04:00

173 lines
5.6 KiB
C++

/*
* Copyright (C) 2017 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "system_properties/contexts_serialized.h"
#include <fcntl.h>
#include <limits.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <new>
#include <async_safe/log.h>
#include "system_properties/system_properties.h"
bool ContextsSerialized::InitializeContextNodes() {
auto num_context_nodes = property_info_area_file_->num_contexts();
auto context_nodes_mmap_size = sizeof(ContextNode) * num_context_nodes;
// We want to avoid malloc in system properties, so we take an anonymous map instead (b/31659220).
void* const map_result = mmap(nullptr, context_nodes_mmap_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (map_result == MAP_FAILED) {
return false;
}
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, map_result, context_nodes_mmap_size,
"System property context nodes");
context_nodes_ = reinterpret_cast<ContextNode*>(map_result);
num_context_nodes_ = num_context_nodes;
context_nodes_mmap_size_ = context_nodes_mmap_size;
for (size_t i = 0; i < num_context_nodes; ++i) {
new (&context_nodes_[i]) ContextNode(property_info_area_file_->context(i), filename_);
}
return true;
}
bool ContextsSerialized::MapSerialPropertyArea(bool access_rw, bool* fsetxattr_failed) {
char filename[PROP_FILENAME_MAX];
int len = async_safe_format_buffer(filename, sizeof(filename), "%s/properties_serial", filename_);
if (len < 0 || len >= PROP_FILENAME_MAX) {
serial_prop_area_ = nullptr;
return false;
}
if (access_rw) {
serial_prop_area_ =
prop_area::map_prop_area_rw(filename, "u:object_r:properties_serial:s0", fsetxattr_failed);
} else {
serial_prop_area_ = prop_area::map_prop_area(filename);
}
return serial_prop_area_;
}
bool ContextsSerialized::InitializeProperties() {
if (!property_info_area_file_.LoadDefaultPath()) {
return false;
}
if (!InitializeContextNodes()) {
FreeAndUnmap();
return false;
}
return true;
}
bool ContextsSerialized::Initialize(bool writable, const char* filename, bool* fsetxattr_failed) {
filename_ = filename;
if (!InitializeProperties()) {
return false;
}
if (writable) {
mkdir(filename_, S_IRWXU | S_IXGRP | S_IXOTH);
bool open_failed = false;
if (fsetxattr_failed) {
*fsetxattr_failed = false;
}
for (size_t i = 0; i < num_context_nodes_; ++i) {
if (!context_nodes_[i].Open(true, fsetxattr_failed)) {
open_failed = true;
}
}
if (open_failed || !MapSerialPropertyArea(true, fsetxattr_failed)) {
FreeAndUnmap();
return false;
}
} else {
if (!MapSerialPropertyArea(false, nullptr)) {
FreeAndUnmap();
return false;
}
}
return true;
}
prop_area* ContextsSerialized::GetPropAreaForName(const char* name) {
uint32_t index;
property_info_area_file_->GetPropertyInfoIndexes(name, &index, nullptr);
if (index == ~0u || index >= num_context_nodes_) {
async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Could not find context for property \"%s\"",
name);
return nullptr;
}
auto* context_node = &context_nodes_[index];
if (!context_node->pa()) {
// We explicitly do not check no_access_ in this case because unlike the
// case of foreach(), we want to generate an selinux audit for each
// non-permitted property access in this function.
context_node->Open(false, nullptr);
}
return context_node->pa();
}
void ContextsSerialized::ForEach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
for (size_t i = 0; i < num_context_nodes_; ++i) {
if (context_nodes_[i].CheckAccessAndOpen()) {
context_nodes_[i].pa()->foreach (propfn, cookie);
}
}
}
void ContextsSerialized::ResetAccess() {
for (size_t i = 0; i < num_context_nodes_; ++i) {
context_nodes_[i].ResetAccess();
}
}
void ContextsSerialized::FreeAndUnmap() {
property_info_area_file_.Reset();
if (context_nodes_ != nullptr) {
for (size_t i = 0; i < num_context_nodes_; ++i) {
context_nodes_[i].Unmap();
}
munmap(context_nodes_, context_nodes_mmap_size_);
context_nodes_ = nullptr;
}
prop_area::unmap_prop_area(&serial_prop_area_);
serial_prop_area_ = nullptr;
}