TLS - add server name reader

Author: Zainullin Damir

src/plugins/process/common/tlsParser/extensionReaders/serverNameReader.hpp

@@ -0,0 +1,70 @@
+/**
+ * @file
+ * @brief Prefixed length string reader.
+ * @author Damir Zainullin <[email protected]>
+ * @date 2025
+ *
+ * @copyright Copyright (c) 2025 CESNET, z.s.p.o.
+ */
+
+#pragma once
+
+#include "../../readers/rangeReader/generator.hpp"
+#include "../../readers/rangeReader/rangeReader.hpp"
+
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <ranges>
+#include <span>
+
+#include <arpa/inet.h>
+
+namespace ipxp {
+
+/**
+ * @struct PrefixedLengthStringReader
+ * @brief Reader for strings prefixed with their length.
+ *
+ * This reader extracts strings from a byte span where each string is prefixed
+ * by its length of type `LengthType`. It generates a range of strings until
+ * it encounters an end or fails to parse a string.
+ *
+ * @tparam LengthType The type used for the length prefix (e.g., uint8_t, uint16_t).
+ */
+
+struct [[gnu::packed]] ServerNameExtension {
+	uint8_t type;
+	uint16_t length;
+};
+
+struct ServerNameReader : public RangeReader {
+	auto getRange(std::span<const std::byte> extension) noexcept
+	{
+		return Generator([this, extension]() mutable -> std::optional<std::string_view> {
+			if (extension.empty()) {
+				setSuccess();
+				return std::nullopt;
+			}
+
+			if (extension.size() < sizeof(ServerNameExtension)) {
+				return std::nullopt;
+			}
+
+			const ServerNameExtension* serverNameExtension
+				= reinterpret_cast<const ServerNameExtension*>(extension.data());
+			const uint16_t length = ntohs(serverNameExtension->length);
+			if (extension.size() < length + sizeof(ServerNameExtension)) {
+				return std::nullopt;
+			}
+
+			const auto label
+				= reinterpret_cast<const char*>(extension.data() + sizeof(ServerNameExtension));
+			extension = extension.subspan(length + sizeof(ServerNameExtension));
+
+			return std::string_view(label, length);
+		});
+	}
+};
+
+} // namespace ipxp