Set LastKnownGoodTime using UTC via python-generated header (#28668)

* WIP: set LKGT using UTC via python

* appease the linter

* Changes from review

* Remove header guard cruft

build/chip/write_build_time_header.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python
+# Copyright (c) 2023 Project CHIP Authors
+#
+# 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.
+
+import argparse
+import os
+from datetime import datetime, timezone
+
+
+def utc_time_in_matter_epoch_s():
+    """ Returns the time in matter epoch in s. """
+    # Matter epoch is 0 hours, 0 minutes, 0 seconds on Jan 1, 2000 UTC
+    utc_matter = datetime.now(tz=timezone.utc) - datetime(2000, 1, 1, 0, 0, 0, 0, timezone.utc)
+    return int(utc_matter.total_seconds())
+
+
+class Options:
+    def __init__(self, output, define_name, define_val):
+        self.output = output
+        self.define_name = define_name
+        self.define_val = define_val
+
+
+def GetOptions():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--output', help="Output header name (inside gen dir)")
+    parser.add_argument('--gen-dir',
+                        help="Path to root of generated file directory tree.")
+    cmdline_options = parser.parse_args()
+
+    # The actual output file is inside the gen dir.
+    output = os.path.join(cmdline_options.gen_dir, cmdline_options.output)
+
+    define_name = 'CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_TIME_MATTER_EPOCH_S'
+    build_time = utc_time_in_matter_epoch_s()
+
+    return Options(output=output,
+                   define_name=define_name,
+                   define_val=str(build_time))
+
+
+def WriteHeader(options):
+    with open(options.output, "w") as output_file:
+        output_file.write("// Generated by write_build_time_header.py\n")
+        output_file.write('#pragma once\n\n')
+
+        output_file.write(f'#define {options.define_name} {options.define_val}\n')
+
+
+options = GetOptions()
+WriteHeader(options)

src/credentials/BUILD.gn

@@ -16,11 +16,32 @@ import("//build_overrides/chip.gni")
 import("//build_overrides/nlassert.gni")
 import("${chip_root}/src/crypto/crypto.gni")
 import("${chip_root}/src/platform/device.gni")
-
 declare_args() {
   chip_build_example_creds = true
 }
 
+action("gen_build_time_header") {
+  script = "${chip_root}/build/chip/write_build_time_header.py"
+
+  header_file = "FirmwareBuildTime.h"
+  include_dir = "${root_gen_dir}/include"
+  outputs = [ "${include_dir}/${header_file}" ]
+
+  args = [
+    "--output",
+    header_file,
+    "--gen-dir",
+    rebase_path(include_dir, root_build_dir),
+  ]
+
+  visibility = [ ":build_time_header" ]
+}
+
+source_set("build_time_header") {
+  sources = get_target_outputs(":gen_build_time_header")
+  deps = [ ":gen_build_time_header" ]
+}
+
 static_library("credentials") {
   output_name = "libCredentials"
 
@@ -87,6 +108,7 @@ static_library("credentials") {
   cflags = [ "-Wconversion" ]
 
   public_deps = [
+    ":build_time_header",
     "${chip_root}/src/crypto",
     "${chip_root}/src/lib/asn1",
     "${chip_root}/src/lib/core",

src/include/platform/internal/GenericConfigurationManagerImpl.ipp

@@ -26,6 +26,7 @@
 #ifndef GENERIC_CONFIGURATION_MANAGER_IMPL_CPP
 #define GENERIC_CONFIGURATION_MANAGER_IMPL_CPP
 
+#include <FirmwareBuildTime.h>
 #include <ble/CHIPBleServiceData.h>
 #include <crypto/CHIPCryptoPAL.h>
 #include <crypto/RandUtils.h>
@@ -290,6 +291,12 @@ CHIP_ERROR GenericConfigurationManagerImpl<ConfigClass>::GetFirmwareBuildChipEpo
         chipEpochTime = sFirmwareBuildChipEpochTime.Value();
         return CHIP_NO_ERROR;
     }
+#ifdef CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_TIME_MATTER_EPOCH_S
+    {
+        chipEpochTime = chip::System::Clock::Seconds32(CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_TIME_MATTER_EPOCH_S);
+        return CHIP_NO_ERROR;
+    }
+#endif
     // Else, attempt to read the hard-coded values.
     VerifyOrReturnError(!BUILD_DATE_IS_BAD(CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_DATE), CHIP_ERROR_INTERNAL);
     VerifyOrReturnError(!BUILD_TIME_IS_BAD(CHIP_DEVICE_CONFIG_FIRMWARE_BUILD_TIME), CHIP_ERROR_INTERNAL);

src/platform/BUILD.gn

@@ -452,6 +452,7 @@ if (chip_device_platform != "none") {
       ":platform_base",
       "${chip_root}/src/app:app_config",
       "${chip_root}/src/app/common:cluster-objects",
+      "${chip_root}/src/credentials:build_time_header",
       "${chip_root}/src/crypto",
       "${chip_root}/src/lib/support",
     ]