diff --git a/FsCrypt.cpp b/FsCrypt.cpp index e28002f..bea9328 100644 --- a/FsCrypt.cpp +++ b/FsCrypt.cpp @@ -57,6 +57,7 @@ #include #include #include +#include #include 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& 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; + get_data_file_encryption_options(&device_ref); + if (!android::vold::retrieveAndInstallKey(true, kEmptyAuthentication, device_key_path, - device_key_temp, "", &device_ref.key_raw_ref)) + device_key_temp, "", device_ref.policy_version, + &device_ref.key_raw_ref)) return false; - get_data_file_encryption_modes(&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; + 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; diff --git a/KeyUtil.cpp b/KeyUtil.cpp index c1a82fb..f822377 100644 --- a/KeyUtil.cpp +++ b/KeyUtil.cpp @@ -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; } diff --git a/KeyUtil.h b/KeyUtil.h index 146f4d3..f6799d9 100644 --- a/KeyUtil.h +++ b/KeyUtil.h @@ -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);