Merge changes from topic "fscrypt-key-mgmt-improvements"
am: 22d50012b0
Change-Id: I97a1990aa2f0bdaf2a622555774b737bfc6d26ab
diff --git a/FsCrypt.cpp b/FsCrypt.cpp
index e28002f..bea9328 100644
--- a/FsCrypt.cpp
+++ b/FsCrypt.cpp
@@ -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 @@
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 @@
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 @@
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 @@
}
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 @@
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 @@
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 @@
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 @@
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 @@
}
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 @@
// 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 @@
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 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 @@
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 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);