Revert "Revert "Weaver HAL""

This reverts commit 66d499a26faa4603af9b8140cb1d620431b036a5.
Test: It builds

Change-Id: I204e46e7ab7c91454a4561ff44bf9920ca78d6a5
diff --git a/weaver/1.0/IWeaver.hal b/weaver/1.0/IWeaver.hal
new file mode 100644
index 0000000..2362c29
--- /dev/null
+++ b/weaver/1.0/IWeaver.hal
@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+package android.hardware.weaver@1.0;
+
+/**
+ * Weaver provides secure storage of secret values that can only be read if the
+ * corresponding key has been presented.
+ *
+ * The storage must be secure as the device's user authentication and encryption
+ * relies on the security of these values. The cardinality of the domains of the
+ * key and value must be suitably large such that they cannot be easily guessed.
+ *
+ * Weaver is structured as an array of slots, each containing a key-value pair.
+ * Slots are uniquely identified by an ID in the range [0, `getConfig().slots`).
+ */
+interface IWeaver {
+    /**
+     * Retrieves the config information for this implementation of Weaver.
+     *
+     * The config is static i.e. every invocation returns the same information.
+     *
+     * @return status is OK if the config was successfuly obtained.
+     * @return config data for this implementation of Weaver if status is OK,
+     *         otherwise undefined.
+     */
+    getConfig() generates (WeaverStatus status, WeaverConfig config);
+
+    /**
+     * Overwrites the identified slot with the provided key and value.
+     *
+     * The new values are written regardless of the current state of the slot in
+     * order to remain idempotent.
+     *
+     * @param slotId of the slot to write to.
+     * @param key to write to the slot.
+     * @param value to write to slot.
+     * @return status is OK if the write was successfully completed.
+     */
+    write(uint32_t slotId, vec<uint8_t> key, vec<uint8_t> value)
+                generates (WeaverStatus status);
+
+    /**
+     * Attempts to retrieve the value stored in the identified slot.
+     *
+     * The value is only returned if the provided key matches the key stored in
+     * the slot. The value is never returned if the wrong key is provided.
+     *
+     * Throttling is used to limit the frequency of failed read attempts. The
+     * value is only returned when throttling is not active, even if the correct
+     * key is provided. If called when throttling is active, the time until the
+     * next attempt can be made is returned.
+     *
+     * @param slotId of the slot to read from.
+     * @param key that is stored in the slot.
+     * @return status is OK if the value was successfully read, INCORRECT_KEY if
+     *         the key does not match the key in the slot or THROTTLE if
+     *         throttling is active.
+     * @return readResponse contains the value read and the timeout to wait
+     *         before making the next request. The value is undefined if the
+     *         status is not OK and the timeout is undefined if the status is
+     *         FAILED.
+     */
+    read(uint32_t slotId, vec<uint8_t> key)
+                generates (WeaverReadStatus status,
+                           WeaverReadResponse readResponse);
+};