decrypt: AOSP 10 requires the use of fscrypt
fscrypt aosp doc: https://source.android.com/security/encryption/file-based
kernel fscrypt doc: https://www.kernel.org/doc/html/v4.18/filesystems/fscrypt.html
This commit implements the ability for TWRP to use fscrypt to decrypt
files on the fscrypt implementation. It has been implemented mostly
in a new successor library to e4crypt called libtwrpfscrypt. Most of the
code was ported from AOSP vold.
Notable updates include:
- updated policy storage by libtar
- lookup of fbe policies by libtwrpfscrypt
- threaded keystore operations
Big thanks to Dees_Troy for the initial trailblazing
of encryption in TWRP.
Change-Id: I69cd2eba3693a9914e00213d4943229635d0cdae
diff --git a/crypto/fscrypt/KeyStorage.h b/crypto/fscrypt/KeyStorage.h
new file mode 100755
index 0000000..276b6b9
--- /dev/null
+++ b/crypto/fscrypt/KeyStorage.h
@@ -0,0 +1,74 @@
+/*
+ * 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.
+ */
+
+#ifndef ANDROID_VOLD_KEYSTORAGE_H
+#define ANDROID_VOLD_KEYSTORAGE_H
+
+#include "KeyBuffer.h"
+
+#include <string>
+
+namespace android {
+namespace vold {
+
+// Represents the information needed to decrypt a disk encryption key.
+// If "token" is nonempty, it is passed in as a required Gatekeeper auth token.
+// If "token" and "secret" are nonempty, "secret" is appended to the application-specific
+// binary needed to unlock.
+// If only "secret" is nonempty, it is used to decrypt in a non-Keymaster process.
+class KeyAuthentication {
+ public:
+ KeyAuthentication(const std::string& t, const std::string& s) : token{t}, secret{s} {};
+
+ bool usesKeymaster() const { return !token.empty() || secret.empty(); };
+
+ const std::string token;
+ const std::string secret;
+};
+
+extern const KeyAuthentication kEmptyAuthentication;
+
+// Checks if path "path" exists.
+bool pathExists(const std::string& path);
+
+bool createSecdiscardable(const std::string& path, std::string* hash);
+bool readSecdiscardable(const std::string& path, std::string* hash);
+
+// Create a directory at the named path, and store "key" in it,
+// in such a way that it can only be retrieved via Keymaster and
+// can be securely deleted.
+// It's safe to move/rename the directory after creation.
+bool storeKey(const std::string& dir, const KeyAuthentication& auth, const KeyBuffer& key);
+
+// Create a directory at the named path, and store "key" in it as storeKey
+// This version creates the key in "tmp_path" then atomically renames "tmp_path"
+// to "key_path" thereby ensuring that the key is either stored entirely or
+// not at all.
+bool storeKeyAtomically(const std::string& key_path, const std::string& tmp_path,
+ const KeyAuthentication& auth, const KeyBuffer& key);
+
+// Retrieve the key from the named directory.
+bool retrieveKey(const std::string& dir, const KeyAuthentication& auth, KeyBuffer* key,
+ bool keepOld = false);
+
+// Securely destroy the key stored in the named directory and delete the directory.
+bool destroyKey(const std::string& dir);
+
+bool runSecdiscardSingle(const std::string& file);
+} // namespace vold
+} // namespace android
+
+#endif