[u-boot-mgr]: Initial u-boot mgr hardening intf

Initial u-boot mgr to harden interface and usage. This
exposes method in D-Bus which other daemon can use to update
U-Boot environment variables, instead of directly using
fw_printenv  or fw_setenv tools.

Tested:
Verified able to query the ReadAll, Read and Write
method exposed in this interface.

Signed-off-by: Richard Marian Thomaiyar <richard.marian.thomaiyar@linux.intel.com>
Change-Id: I21772c8f30b7c68f5c9a2da3d44217ea2f533014
diff --git a/src/u-boot-env-mgr.cpp b/src/u-boot-env-mgr.cpp
new file mode 100644
index 0000000..30c8656
--- /dev/null
+++ b/src/u-boot-env-mgr.cpp
@@ -0,0 +1,110 @@
+/*
+// Copyright (c) 2019 Intel Corporation
+//
+// 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.
+*/
+
+#include "u-boot-env-mgr.hpp"
+#include <phosphor-logging/log.hpp>
+#include <phosphor-logging/elog-errors.hpp>
+#include <boost/process/child.hpp>
+#include <boost/process/io.hpp>
+#include <vector>
+#include <unordered_map>
+#include <xyz/openbmc_project/Common/error.hpp>
+
+template <typename... ArgTypes>
+static std::vector<std::string> executeCmd(const char* path,
+                                           ArgTypes&&... tArgs)
+{
+    std::vector<std::string> stdOutput;
+    boost::process::ipstream stdOutStream;
+    boost::process::child execProg(path, const_cast<char*>(tArgs)...,
+                                   boost::process::std_out > stdOutStream);
+    std::string stdOutLine;
+
+    while (stdOutStream && std::getline(stdOutStream, stdOutLine) &&
+           !stdOutLine.empty())
+    {
+        stdOutput.emplace_back(stdOutLine);
+    }
+
+    execProg.wait();
+
+    int retCode = execProg.exit_code();
+    if (retCode)
+    {
+        phosphor::logging::log<phosphor::logging::level::ERR>(
+            "Command execution failed",
+            phosphor::logging::entry("PATH=%d", path),
+            phosphor::logging::entry("RETURN_CODE:%d", retCode));
+        phosphor::logging::elog<
+            sdbusplus::xyz::openbmc_project::Common::Error::InternalFailure>();
+    }
+
+    return stdOutput;
+}
+
+UBootEnvMgr::UBootEnvMgr(boost::asio::io_service& io_,
+                         sdbusplus::asio::object_server& srv_,
+                         std::shared_ptr<sdbusplus::asio::connection>& conn_) :
+    io(io_),
+    server(srv_), conn(conn_)
+{
+    iface = server.add_interface(uBootEnvMgrPath, uBootEnvMgrIface);
+    iface->register_method("ReadAll", [this]() { return readAllVariable(); });
+    iface->register_method("Read", [this](const std::string& key) {
+        std::unordered_map<std::string, std::string> env = readAllVariable();
+        auto it = env.find(key);
+        if (it != env.end())
+        {
+            return it->second;
+        }
+        return std::string{};
+    });
+
+    iface->register_method(
+        "Write", [this](const std::string& key, const std::string& value) {
+            writeVariable(key, value);
+        });
+    iface->initialize(true);
+}
+
+std::unordered_map<std::string, std::string> UBootEnvMgr::readAllVariable()
+{
+    std::unordered_map<std::string, std::string> env;
+    std::vector<std::string> output = executeCmd("/sbin/fw_printenv");
+    for (const auto& entry : output)
+    {
+        size_t pos = entry.find("=");
+        if (pos + 1 >= entry.size())
+        {
+            phosphor::logging::log<phosphor::logging::level::ERR>(
+                "Invalid U-Boot environment",
+                phosphor::logging::entry("ENTRY=%s", entry.c_str()));
+            continue;
+        }
+        // using string instead of string_view for null termination
+        std::string key = entry.substr(0, pos);
+        std::string value = entry.substr(pos + 1);
+        env.emplace(key, value);
+    }
+    return env;
+}
+
+void UBootEnvMgr::writeVariable(const std::string& key,
+                                const std::string& value)
+{
+    executeCmd("/sbin/fw_setenv", key.c_str(), value.c_str());
+    return;
+}