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Merge changes from topic "fscrypt-key-mgmt-improvements" am: 22d50012b0 am: de5c9ad178

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am: 5a7cace2fc

Change-Id: Ibb446d5d4daa38ebd4ce8ff52fb07a34a75a179c
This commit is contained in:
Eric Biggers 2019-10-07 12:41:03 -07:00 committed by android-build-merger
commit d5c689fd48
3 changed files with 150 additions and 51 deletions
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98
FsCrypt.cpp
View file

@ -57,6 +57,7 @@
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
using android::base::StringPrintf;
@ -70,7 +71,10 @@ namespace {
struct PolicyKeyRef {
std::string contents_mode;
std::string filenames_mode;
int policy_version;
std::string key_raw_ref;
PolicyKeyRef() : policy_version(0) {}
};
const std::string device_key_dir = std::string() + DATA_MNT_POINT + fscrypt_unencrypted_folder;
@ -199,14 +203,57 @@ static bool read_and_fixate_user_ce_key(userid_t user_id,
return false;
}
// Retrieve the options to use for encryption policies on the /data filesystem.
static void get_data_file_encryption_options(PolicyKeyRef* key_ref) {
auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
if (entry == nullptr) {
return;
}
key_ref->contents_mode = entry->file_contents_mode;
key_ref->filenames_mode = entry->file_names_mode;
key_ref->policy_version = entry->file_policy_version;
}
// Retrieve the version to use for encryption policies on the /data filesystem.
static int get_data_file_policy_version(void) {
auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
if (entry == nullptr) {
return 0;
}
return entry->file_policy_version;
}
// Retrieve the options to use for encryption policies on adoptable storage.
static bool get_volume_file_encryption_options(PolicyKeyRef* key_ref) {
key_ref->contents_mode =
android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
key_ref->filenames_mode =
android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
key_ref->policy_version = 1;
std::string raw_flags = android::base::GetProperty("ro.crypto.volume.flags", "");
auto flags = android::base::Split(raw_flags, "+");
for (const auto& flag : flags) {
if (flag == "v1") {
key_ref->policy_version = 1;
} else if (flag == "v2") {
key_ref->policy_version = 2;
} else {
LOG(ERROR) << "Unknown flag in ro.crypto.volume.flags: " << flag;
return false;
}
}
return true;
}
// Install a key for use by encrypted files on the /data filesystem.
static bool install_data_key(const KeyBuffer& key, std::string* raw_ref) {
return android::vold::installKey(key, DATA_MNT_POINT, raw_ref);
return android::vold::installKey(key, DATA_MNT_POINT, get_data_file_policy_version(), raw_ref);
}
// Evict a key for use by encrypted files on the /data filesystem.
static bool evict_data_key(const std::string& raw_ref) {
return android::vold::evictKey(DATA_MNT_POINT, raw_ref);
return android::vold::evictKey(DATA_MNT_POINT, raw_ref, get_data_file_policy_version());
}
static bool read_and_install_user_ce_key(userid_t user_id,
@ -286,19 +333,10 @@ static bool lookup_key_ref(const std::map<userid_t, std::string>& key_map, useri
return true;
}
static void get_data_file_encryption_modes(PolicyKeyRef* key_ref) {
auto entry = GetEntryForMountPoint(&fstab_default, DATA_MNT_POINT);
if (entry == nullptr) {
return;
}
key_ref->contents_mode = entry->file_contents_mode;
key_ref->filenames_mode = entry->file_names_mode;
}
static bool ensure_policy(const PolicyKeyRef& key_ref, const std::string& path) {
return fscrypt_policy_ensure(path.c_str(), key_ref.key_raw_ref.data(),
key_ref.key_raw_ref.size(), key_ref.contents_mode.c_str(),
key_ref.filenames_mode.c_str()) == 0;
key_ref.filenames_mode.c_str(), key_ref.policy_version) == 0;
}
static bool is_numeric(const char* name) {
@ -354,14 +392,18 @@ bool fscrypt_initialize_systemwide_keys() {
}
PolicyKeyRef device_ref;
if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
device_key_temp, "", &device_ref.key_raw_ref))
return false;
get_data_file_encryption_modes(&device_ref);
get_data_file_encryption_options(&device_ref);
std::string modestring = device_ref.contents_mode + ":" + device_ref.filenames_mode;
std::string mode_filename = std::string("/data") + fscrypt_key_mode;
if (!android::vold::writeStringToFile(modestring, mode_filename)) return false;
if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path,
device_key_temp, "", device_ref.policy_version,
&device_ref.key_raw_ref))
return false;
std::string options_string =
StringPrintf("%s:%s:v%d", device_ref.contents_mode.c_str(),
device_ref.filenames_mode.c_str(), device_ref.policy_version);
std::string options_filename = std::string("/data") + fscrypt_key_mode;
if (!android::vold::writeStringToFile(options_string, options_filename)) return false;
std::string ref_filename = std::string("/data") + fscrypt_key_ref;
if (!android::vold::writeStringToFile(device_ref.key_raw_ref, ref_filename)) return false;
@ -560,14 +602,12 @@ static bool read_or_create_volkey(const std::string& misc_path, const std::strin
return false;
}
android::vold::KeyAuthentication auth("", secdiscardable_hash);
if (!android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp", volume_uuid,
&key_ref->key_raw_ref))
return false;
key_ref->contents_mode =
android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
key_ref->filenames_mode =
android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
return true;
if (!get_volume_file_encryption_options(key_ref)) return false;
return android::vold::retrieveAndInstallKey(true, auth, key_path, key_path + "_tmp",
volume_uuid, key_ref->policy_version,
&key_ref->key_raw_ref);
}
static bool destroy_volkey(const std::string& misc_path, const std::string& volume_uuid) {
@ -715,7 +755,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
PolicyKeyRef de_ref;
if (volume_uuid.empty()) {
if (!lookup_key_ref(s_de_key_raw_refs, user_id, &de_ref.key_raw_ref)) return false;
get_data_file_encryption_modes(&de_ref);
get_data_file_encryption_options(&de_ref);
if (!ensure_policy(de_ref, system_de_path)) return false;
if (!ensure_policy(de_ref, misc_de_path)) return false;
if (!ensure_policy(de_ref, vendor_de_path)) return false;
@ -746,7 +786,7 @@ bool fscrypt_prepare_user_storage(const std::string& volume_uuid, userid_t user_
PolicyKeyRef ce_ref;
if (volume_uuid.empty()) {
if (!lookup_key_ref(s_ce_key_raw_refs, user_id, &ce_ref.key_raw_ref)) return false;
get_data_file_encryption_modes(&ce_ref);
get_data_file_encryption_options(&ce_ref);
if (!ensure_policy(ce_ref, system_ce_path)) return false;
if (!ensure_policy(ce_ref, misc_ce_path)) return false;
if (!ensure_policy(ce_ref, vendor_ce_path)) return false;

95
KeyUtil.cpp
View file

@ -163,28 +163,80 @@ static bool installKeyLegacy(const KeyBuffer& key, const std::string& raw_ref) {
return true;
}
// Build a struct fscrypt_key_specifier for use in the key management ioctls.
static bool buildKeySpecifier(fscrypt_key_specifier* spec, const std::string& raw_ref,
int policy_version) {
switch (policy_version) {
case 1:
if (raw_ref.size() != FSCRYPT_KEY_DESCRIPTOR_SIZE) {
LOG(ERROR) << "Invalid key specifier size for v1 encryption policy: "
<< raw_ref.size();
return false;
}
spec->type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
memcpy(spec->u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
return true;
case 2:
if (raw_ref.size() != FSCRYPT_KEY_IDENTIFIER_SIZE) {
LOG(ERROR) << "Invalid key specifier size for v2 encryption policy: "
<< raw_ref.size();
return false;
}
spec->type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
memcpy(spec->u.identifier, raw_ref.c_str(), FSCRYPT_KEY_IDENTIFIER_SIZE);
return true;
default:
LOG(ERROR) << "Invalid encryption policy version: " << policy_version;
return false;
}
}
// Install a file-based encryption key to the kernel, for use by encrypted files
// on the specified filesystem.
// on the specified filesystem using the specified encryption policy version.
//
// We use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it. Otherwise we add
// the key to the legacy global session keyring.
// For v1 policies, we use FS_IOC_ADD_ENCRYPTION_KEY if the kernel supports it.
// Otherwise we add the key to the legacy global session keyring.
//
// For v2 policies, we always use FS_IOC_ADD_ENCRYPTION_KEY; it's the only way
// the kernel supports.
//
// Returns %true on success, %false on failure. On success also sets *raw_ref
// to the raw key reference for use in the encryption policy.
bool installKey(const KeyBuffer& key, const std::string& mountpoint, std::string* raw_ref) {
*raw_ref = generateKeyRef((const uint8_t*)key.data(), key.size());
if (!isFsKeyringSupported()) {
return installKeyLegacy(key, *raw_ref);
}
bool installKey(const KeyBuffer& key, const std::string& mountpoint, int policy_version,
std::string* raw_ref) {
// Put the fscrypt_add_key_arg in an automatically-zeroing buffer, since we
// have to copy the raw key into it.
KeyBuffer arg_buf(sizeof(struct fscrypt_add_key_arg) + key.size(), 0);
struct fscrypt_add_key_arg* arg = (struct fscrypt_add_key_arg*)arg_buf.data();
arg->key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
memcpy(arg->key_spec.u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
// Initialize the "key specifier", which is like a name for the key.
switch (policy_version) {
case 1:
// A key for a v1 policy is specified by an arbitrary 8-byte
// "descriptor", which must be provided by userspace. We use the
// first 8 bytes from the double SHA-512 of the key itself.
*raw_ref = generateKeyRef((const uint8_t*)key.data(), key.size());
if (!isFsKeyringSupported()) {
return installKeyLegacy(key, *raw_ref);
}
if (!buildKeySpecifier(&arg->key_spec, *raw_ref, policy_version)) {
return false;
}
break;
case 2:
// A key for a v2 policy is specified by an 16-byte "identifier",
// which is a cryptographic hash of the key itself which the kernel
// computes and returns. Any user-provided value is ignored; we
// just need to set the specifier type to indicate that we're adding
// this type of key.
arg->key_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
break;
default:
LOG(ERROR) << "Invalid encryption policy version: " << policy_version;
return false;
}
// Provide the raw key.
arg->raw_size = key.size();
memcpy(arg->raw, key.data(), key.size());
@ -195,11 +247,14 @@ bool installKey(const KeyBuffer& key, const std::string& mountpoint, std::string
}
if (ioctl(fd, FS_IOC_ADD_ENCRYPTION_KEY, arg) != 0) {
PLOG(ERROR) << "Failed to install fscrypt key with ref " << keyrefstring(*raw_ref) << " to "
<< mountpoint;
PLOG(ERROR) << "Failed to install fscrypt key to " << mountpoint;
return false;
}
if (arg->key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
// Retrieve the key identifier that the kernel computed.
*raw_ref = std::string((char*)arg->key_spec.u.identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
}
LOG(DEBUG) << "Installed fscrypt key with ref " << keyrefstring(*raw_ref) << " to "
<< mountpoint;
return true;
@ -234,8 +289,8 @@ static bool evictKeyLegacy(const std::string& raw_ref) {
// remove the key from the legacy global session keyring.
//
// In the latter case, the caller is responsible for dropping caches.
bool evictKey(const std::string& mountpoint, const std::string& raw_ref) {
if (!isFsKeyringSupported()) {
bool evictKey(const std::string& mountpoint, const std::string& raw_ref, int policy_version) {
if (policy_version == 1 && !isFsKeyringSupported()) {
return evictKeyLegacy(raw_ref);
}
@ -248,8 +303,9 @@ bool evictKey(const std::string& mountpoint, const std::string& raw_ref) {
struct fscrypt_remove_key_arg arg;
memset(&arg, 0, sizeof(arg));
arg.key_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
memcpy(arg.key_spec.u.descriptor, raw_ref.c_str(), FSCRYPT_KEY_DESCRIPTOR_SIZE);
if (!buildKeySpecifier(&arg.key_spec, raw_ref, policy_version)) {
return false;
}
std::string ref = keyrefstring(raw_ref);
@ -271,7 +327,8 @@ bool evictKey(const std::string& mountpoint, const std::string& raw_ref) {
bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
const std::string& key_path, const std::string& tmp_path,
const std::string& volume_uuid, std::string* key_ref) {
const std::string& volume_uuid, int policy_version,
std::string* key_ref) {
KeyBuffer key;
if (pathExists(key_path)) {
LOG(DEBUG) << "Key exists, using: " << key_path;
@ -286,7 +343,7 @@ bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_a
if (!storeKeyAtomically(key_path, tmp_path, key_authentication, key)) return false;
}
if (!installKey(key, BuildDataPath(volume_uuid), key_ref)) {
if (!installKey(key, BuildDataPath(volume_uuid), policy_version, key_ref)) {
LOG(ERROR) << "Failed to install key in " << key_path;
return false;
}

8
KeyUtil.h
View file

@ -30,11 +30,13 @@ bool randomKey(KeyBuffer* key);
bool isFsKeyringSupported(void);
bool installKey(const KeyBuffer& key, const std::string& mountpoint, std::string* raw_ref);
bool evictKey(const std::string& mountpoint, const std::string& raw_ref);
bool installKey(const KeyBuffer& key, const std::string& mountpoint, int policy_version,
std::string* raw_ref);
bool evictKey(const std::string& mountpoint, const std::string& raw_ref, int policy_version);
bool retrieveAndInstallKey(bool create_if_absent, const KeyAuthentication& key_authentication,
const std::string& key_path, const std::string& tmp_path,
const std::string& volume_uuid, std::string* key_ref);
const std::string& volume_uuid, int policy_version,
std::string* key_ref);
bool retrieveKey(bool create_if_absent, const std::string& key_path, const std::string& tmp_path,
KeyBuffer* key, bool keepOld = true);