Magisk/native/jni/external/systemproperties/contexts_split.cpp
2020-12-31 15:06:19 -08:00

364 lines
10 KiB
C++
Vendored

/*
* Copyright (C) 2008 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_split.h"
#include <ctype.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <async_safe/log.h>
#include "system_properties/context_node.h"
#include "system_properties/system_properties.h"
class ContextListNode : public ContextNode {
public:
ContextListNode(ContextListNode* next, const char* context, const char* filename)
: ContextNode(strdup(context), filename), next(next) {
}
~ContextListNode() {
free(const_cast<char*>(context()));
}
ContextListNode* next;
};
struct PrefixNode {
PrefixNode(struct PrefixNode* next, const char* prefix, ContextListNode* context)
: prefix(strdup(prefix)), prefix_len(strlen(prefix)), context(context), next(next) {
}
~PrefixNode() {
free(prefix);
}
char* prefix;
const size_t prefix_len;
ContextListNode* context;
PrefixNode* next;
};
template <typename List, typename... Args>
static inline void ListAdd(List** list, Args... args) {
*list = new List(*list, args...);
}
static void ListAddAfterLen(PrefixNode** list, const char* prefix, ContextListNode* context) {
size_t prefix_len = strlen(prefix);
auto next_list = list;
while (*next_list) {
if ((*next_list)->prefix_len < prefix_len || (*next_list)->prefix[0] == '*') {
ListAdd(next_list, prefix, context);
return;
}
next_list = &(*next_list)->next;
}
ListAdd(next_list, prefix, context);
}
template <typename List, typename Func>
static void ListForEach(List* list, Func func) {
while (list) {
func(list);
list = list->next;
}
}
template <typename List, typename Func>
static List* ListFind(List* list, Func func) {
while (list) {
if (func(list)) {
return list;
}
list = list->next;
}
return nullptr;
}
template <typename List>
static void ListFree(List** list) {
while (*list) {
auto old_list = *list;
*list = old_list->next;
delete old_list;
}
}
// The below two functions are duplicated from label_support.c in libselinux.
// TODO: Find a location suitable for these functions such that both libc and
// libselinux can share a common source file.
// The read_spec_entries and read_spec_entry functions may be used to
// replace sscanf to read entries from spec files. The file and
// property services now use these.
// Read an entry from a spec file (e.g. file_contexts)
static inline int read_spec_entry(char** entry, char** ptr, int* len) {
*entry = nullptr;
char* tmp_buf = nullptr;
while (isspace(**ptr) && **ptr != '\0') (*ptr)++;
tmp_buf = *ptr;
*len = 0;
while (!isspace(**ptr) && **ptr != '\0') {
(*ptr)++;
(*len)++;
}
if (*len) {
*entry = strndup(tmp_buf, *len);
if (!*entry) return -1;
}
return 0;
}
// line_buf - Buffer containing the spec entries .
// num_args - The number of spec parameter entries to process.
// ... - A 'char **spec_entry' for each parameter.
// returns - The number of items processed.
//
// This function calls read_spec_entry() to do the actual string processing.
static int read_spec_entries(char* line_buf, int num_args, ...) {
char **spec_entry, *buf_p;
int len, rc, items, entry_len = 0;
va_list ap;
len = strlen(line_buf);
if (line_buf[len - 1] == '\n')
line_buf[len - 1] = '\0';
else
// Handle case if line not \n terminated by bumping
// the len for the check below (as the line is NUL
// terminated by getline(3))
len++;
buf_p = line_buf;
while (isspace(*buf_p)) buf_p++;
// Skip comment lines and empty lines.
if (*buf_p == '#' || *buf_p == '\0') return 0;
// Process the spec file entries
va_start(ap, num_args);
items = 0;
while (items < num_args) {
spec_entry = va_arg(ap, char**);
if (len - 1 == buf_p - line_buf) {
va_end(ap);
return items;
}
rc = read_spec_entry(spec_entry, &buf_p, &entry_len);
if (rc < 0) {
va_end(ap);
return rc;
}
if (entry_len) items++;
}
va_end(ap);
return items;
}
bool ContextsSplit::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 ContextsSplit::InitializePropertiesFromFile(const char* filename) {
FILE* file = fopen(filename, "re");
if (!file) {
return false;
}
char* buffer = nullptr;
size_t line_len;
char* prop_prefix = nullptr;
char* context = nullptr;
while (getline(&buffer, &line_len, file) > 0) {
int items = read_spec_entries(buffer, 2, &prop_prefix, &context);
if (items <= 0) {
continue;
}
if (items == 1) {
free(prop_prefix);
continue;
}
// init uses ctl.* properties as an IPC mechanism and does not write them
// to a property file, therefore we do not need to create property files
// to store them.
if (!strncmp(prop_prefix, "ctl.", 4)) {
free(prop_prefix);
free(context);
continue;
}
auto old_context = ListFind(
contexts_, [context](ContextListNode* l) { return !strcmp(l->context(), context); });
if (old_context) {
ListAddAfterLen(&prefixes_, prop_prefix, old_context);
} else {
ListAdd(&contexts_, context, filename_);
ListAddAfterLen(&prefixes_, prop_prefix, contexts_);
}
free(prop_prefix);
free(context);
}
free(buffer);
fclose(file);
return true;
}
bool ContextsSplit::InitializeProperties() {
// If we do find /property_contexts, then this is being
// run as part of the OTA updater on older release that had
// /property_contexts - b/34370523
if (InitializePropertiesFromFile("/property_contexts")) {
return true;
}
// Use property_contexts from /system & /vendor, fall back to those from /
if (access("/system/etc/selinux/plat_property_contexts", R_OK) != -1) {
if (!InitializePropertiesFromFile("/system/etc/selinux/plat_property_contexts")) {
return false;
}
// Don't check for failure here, so we always have a sane list of properties.
// E.g. In case of recovery, the vendor partition will not have mounted and we
// still need the system / platform properties to function.
if (access("/vendor/etc/selinux/vendor_property_contexts", R_OK) != -1) {
InitializePropertiesFromFile("/vendor/etc/selinux/vendor_property_contexts");
} else {
// Fallback to nonplat_* if vendor_* doesn't exist.
InitializePropertiesFromFile("/vendor/etc/selinux/nonplat_property_contexts");
}
} else {
if (!InitializePropertiesFromFile("/plat_property_contexts")) {
return false;
}
if (access("/vendor_property_contexts", R_OK) != -1) {
InitializePropertiesFromFile("/vendor_property_contexts");
} else {
// Fallback to nonplat_* if vendor_* doesn't exist.
InitializePropertiesFromFile("/nonplat_property_contexts");
}
}
return true;
}
bool ContextsSplit::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;
}
ListForEach(contexts_, [&fsetxattr_failed, &open_failed](ContextListNode* l) {
if (!l->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* ContextsSplit::GetPropAreaForName(const char* name) {
auto entry = ListFind(prefixes_, [name](PrefixNode* l) {
return l->prefix[0] == '*' || !strncmp(l->prefix, name, l->prefix_len);
});
if (!entry) {
return nullptr;
}
auto cnode = entry->context;
if (!cnode->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.
cnode->Open(false, nullptr);
}
return cnode->pa();
}
void ContextsSplit::ForEach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
ListForEach(contexts_, [propfn, cookie](ContextListNode* l) {
if (l->CheckAccessAndOpen()) {
l->pa()->foreach (propfn, cookie);
}
});
}
void ContextsSplit::ResetAccess() {
ListForEach(contexts_, [](ContextListNode* l) { l->ResetAccess(); });
}
void ContextsSplit::FreeAndUnmap() {
ListFree(&prefixes_);
ListFree(&contexts_);
prop_area::unmap_prop_area(&serial_prop_area_);
}