Generate a separate fstab file for FIPS mode

Add a file "fstab.gs201-fips" alongside the existing "fstab.gs201" in
order to specify different encryption settings in FIPS mode.

"androidboot.fstab_suffix=gs201-fips" on the kernel command line will be
used to select the FIPS fstab when needed.

As the two fstabs should be otherwise identical, generate them from a
template file so that they will stay in sync.

Note that generating the fstabs requires that they be installed as build
system modules rather than via PRODUCT_COPY_FILES, which results in the
vendor_ramdisk copy of the fstabs being installed to system/etc rather
than /.  This shouldn't cause any problem, now that Android has been
updated to look for the fstab in this location too.

(cherry-pick from device/google/gs101)
Test: Boot to home screen with/without fips mode
Bug: 202417706
Signed-off-by: Konstantin Vyshetsky <vkon@google.com>
Change-Id: I8fdc1c9a91399816fa2d4c53f282d63e988ce7d5

conf/Android.bp

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+// By default this device uses hardware-wrapped keys for storage encryption,
+// which is intended to offer increased security over the traditional method
+// (software keys).  However, hardware-wrapped keys aren't compatible with
+// FIPS-140 certification of the encryption hardware, and hence we have to
+// disable the use of them in FIPS mode.  This requires having two fstab files:
+// one for the default mode, and one for FIPS mode selectable via
+// androidboot.fstab_suffix on the kernel command line.  These fstabs should be
+// identical with the exception of the encryption settings, so to keep them in
+// sync the rules below generate them from a template file.
+
+genrule {
+    name: "gen_fstab.gs201",
+    srcs: ["fstab.gs201.in"],
+    out: ["fstab.gs201"],
+    cmd: "sed -e s/@fileencryption@/::inlinecrypt_optimized+wrappedkey_v0/" +
+        " -e s/@metadata_encryption@/:wrappedkey_v0/ $(in) > $(out)",
+}
+
+genrule {
+    name: "gen_fstab.gs201-fips",
+    srcs: ["fstab.gs201.in"],
+    out: ["fstab.gs201-fips"],
+    cmd: "sed -e s/@fileencryption@/aes-256-xts/" +
+        " -e s/@metadata_encryption@/aes-256-xts/ $(in) > $(out)",
+}
+
+prebuilt_etc {
+    name: "fstab.gs201",
+    src: ":gen_fstab.gs201",
+    vendor: true,
+    vendor_ramdisk_available: true,
+}
+
+prebuilt_etc {
+    name: "fstab.gs201-fips",
+    src: ":gen_fstab.gs201-fips",
+    vendor: true,
+    vendor_ramdisk_available: true,
+}