fskeyring & userspace reboot: support CE keys
During userspace reboot /data might be unmounted & remounted, meaning
that CE keys stored in fs-level keyring will be lost. In order to be
able to restore them, when installing new key to fs-level keyring, it's
also added to session-level keyring with type "fscrypt-provisioning".
Then when init_user0 is called during userspace reboot, vold will try to
load CE keys from the session-level keyring back into fs-level keyring
for all the users that were unlocked before the reboot.
If for any user vold fails to install the key, init_user0 will fail and
fallback to hard reboot will be triggered.
Test: set a pin pattern
Test: adb shell setprop sys.init.userdata_remount.force_umount 1
Test: adb shell svc power reboot userspace
Test: atest CtsUserspaceRebootHostSideTestCases
Bug: 143970043
Change-Id: I37603dc136c7ededc7b0381e4d730cb0ffd912b4
diff --git a/KeyUtil.h b/KeyUtil.h
index dcb1dc7..23278c1 100644
--- a/KeyUtil.h
+++ b/KeyUtil.h
@@ -51,11 +51,16 @@
// on the specified filesystem using the specified encryption policy version.
//
// 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.
+// Otherwise we add the key to the global session keyring as a "logon" key.
//
// For v2 policies, we always use FS_IOC_ADD_ENCRYPTION_KEY; it's the only way
// the kernel supports.
//
+// If kernel supports FS_IOC_ADD_ENCRYPTION_KEY, also installs key of
+// fscrypt-provisioning type to the global session keyring. This makes it
+// possible to unmount and then remount mountpoint without losing the file-based
+// key.
+//
// Returns %true on success, %false on failure. On success also sets *policy
// to the EncryptionPolicy used to refer to this key.
bool installKey(const std::string& mountpoint, const EncryptionOptions& options,
@@ -63,16 +68,20 @@
// Evict a file-based encryption key from the kernel.
//
-// We use FS_IOC_REMOVE_ENCRYPTION_KEY if the kernel supports it. Otherwise we
-// remove the key from the legacy global session keyring.
+// This undoes the effect of installKey().
//
-// In the latter case, the caller is responsible for dropping caches.
+// If the kernel doesn't support the filesystem-level keyring, the caller is
+// responsible for dropping caches.
bool evictKey(const std::string& mountpoint, const EncryptionPolicy& policy);
bool retrieveOrGenerateKey(const std::string& key_path, const std::string& tmp_path,
const KeyAuthentication& key_authentication, const KeyGeneration& gen,
KeyBuffer* key, bool keepOld = true);
+// Re-installs a file-based encryption key of fscrypt-provisioning type from the
+// global session keyring back into fs keyring of the mountpoint.
+bool reloadKeyFromSessionKeyring(const std::string& mountpoint, const EncryptionPolicy& policy);
+
} // namespace vold
} // namespace android