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/*
* Copyright (C) 2016 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 "fscrypt/fscrypt.h"
#include "fscrypt/fscrypt_init_extensions.h"
#include <dirent.h>
#include <errno.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string>
#include <vector>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <cutils/properties.h>
#include <cutils/sockets.h>
#include <keyutils.h>
#include <logwrap/logwrap.h>
#define TAG "fscrypt"
static const std::string arbitrary_sequence_number = "42";
static int set_policy_on(char const* ref_basename, char const* dir);
int fscrypt_install_keyring()
{
key_serial_t device_keyring = add_key("keyring", "fscrypt", 0, 0,
KEY_SPEC_SESSION_KEYRING);
if (device_keyring == -1) {
PLOG(ERROR) << "Failed to create keyring";
return -1;
}
LOG(INFO) << "Keyring created with id " << device_keyring << " in process " << getpid();
return 0;
}
int fscrypt_set_directory_policy(const char* dir)
{
if (!dir || strncmp(dir, "/data/", 6)) {
return 0;
}
// Special-case /data/media/obb per b/64566063
if (strcmp(dir, "/data/media/obb") == 0) {
// Try to set policy on this directory, but if it is non-empty this may fail.
set_policy_on(fscrypt_key_ref, dir);
return 0;
}
// Only set policy on first level /data directories
// To make this less restrictive, consider using a policy file.
// However this is overkill for as long as the policy is simply
// to apply a global policy to all /data folders created via makedir
if (strchr(dir + 6, '/')) {
return 0;
}
// Special case various directories that must not be encrypted,
// often because their subdirectories must be encrypted.
// This isn't a nice way to do this, see b/26641735
std::vector<std::string> directories_to_exclude = {
"lost+found",
"system_ce", "system_de",
"misc_ce", "misc_de",
"vendor_ce", "vendor_de",
"media",
"data", "user", "user_de",
"apex", "preloads", "app-staging",
"gsi",
};
std::string prefix = "/data/";
for (const auto& d: directories_to_exclude) {
if ((prefix + d) == dir) {
LOG(INFO) << "Not setting policy on " << dir;
return 0;
}
}
std::vector<std::string> per_boot_directories = {
"per_boot",
};
for (const auto& d : per_boot_directories) {
if ((prefix + d) == dir) {
LOG(INFO) << "Setting per_boot key on " << dir;
return set_policy_on(fscrypt_key_per_boot_ref, dir);
}
}
return set_policy_on(fscrypt_key_ref, dir);
}
static int set_policy_on(char const* ref_basename, char const* dir) {
std::string ref_filename = std::string("/data") + ref_basename;
std::string policy;
if (!android::base::ReadFileToString(ref_filename, &policy)) {
LOG(ERROR) << "Unable to read system policy to set on " << dir;
return -1;
}
auto type_filename = std::string("/data") + fscrypt_key_mode;
std::string modestring;
if (!android::base::ReadFileToString(type_filename, &modestring)) {
LOG(ERROR) << "Cannot read mode";
}
std::vector<std::string> modes = android::base::Split(modestring, ":");
if (modes.size() < 1 || modes.size() > 2) {
LOG(ERROR) << "Invalid encryption mode string: " << modestring;
return -1;
}
LOG(INFO) << "Setting policy on " << dir;
int result = fscrypt_policy_ensure(dir, policy.c_str(), policy.length(),
modes[0].c_str(),
modes.size() >= 2 ?
modes[1].c_str() : "aes-256-cts");
if (result) {
LOG(ERROR) << android::base::StringPrintf(
"Setting %02x%02x%02x%02x policy on %s failed!",
policy[0], policy[1], policy[2], policy[3], dir);
return -1;
}
return 0;
}
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