// OpenVPN 3 Linux client -- Next generation OpenVPN client // // SPDX-License-Identifier: AGPL-3.0-only // // Copyright (C) 2018 - 2023 OpenVPN Inc // Copyright (C) 2018 - 2023 David Sommerseth // /** * @file resolvconf-file.hpp * * @brief This will update resolv.conf files directly, in the typical * resolv.conf format. Normally, this would be /etc/resolv.conf, but * can be used for other files as well, if there is a local * resolver service which picks these files some elsewhere. */ #pragma once #include #include #include #include using namespace openvpn; #include "netcfg/netcfg-signals.hpp" #include "netcfg/dns/resolver-settings.hpp" #include "netcfg/dns/resolver-backend-interface.hpp" namespace NetCfg { namespace DNS { /** * Simple generic file generator and parser * * This can load and save files, take backup of files being overwritten * and restore overwritten files. * * The parsing and contents generating needs to happen in classes * implementing this class. The @generate() and @parse() methods needs * to be implemented for this class to work. * */ class FileGenerator { public: /** * Construct the FileGenerator * * @param filename std::string of the filename this object is * tied to. * @param backup_filename std::string. If non-empty and a backup file * will be created if the Write() operation * will overwrite an existing file. */ FileGenerator(const std::string &filename, const std::string &backup_filename = ""); virtual ~FileGenerator(); /** * Changes the filename of the resolv.conf file to process * after initialization has completed * * @param fname std::string containing the new filename */ virtual void SetFilename(const std::string &fname) noexcept; /** * Retrieve the filename currently in use * * @return Returns a std::string containing the filename */ virtual const std::string GetFilename() const noexcept; /** * Change the filename used for the backup file after initialization * * @param bfname std::string containing the new filename of the * backup file */ virtual void SetBackupFilename(const std::string &bfname) noexcept; /** * Retrieve the filename currently in use for the backup file * * @return Returns a std::string containing the filename */ virtual const std::string GetBackupFilename() const noexcept; protected: std::vector file_contents; /** * Reads the file and saves the contents into the * protected: files_content variable */ void Read(); /** * Writes the contents of the protected: file_contents to disk. * If a backup file is requested, ensure that is arranged before * anything else is done. If a backupfile already exists with * the same filename, the old backup file is automatically removed. * */ void Write(); /** * If a file was overwritten and a backup was made, this will * restore the backup file to the currently configured main filename */ void RestoreBackup(); private: std::string filename = ""; std::string backup_filename = ""; bool backup_active = false; /** * Simple method to check if a file already exists. It does * not do any permissions or availability checks, only if a file * of some kind exists. * * @param fname std::string of filename to look for * @return Returns true if file exists, otherwise false. */ bool file_exists(const std::string &fname) noexcept; }; /** * Class able to read, parse, manipulate and write resolv.conf files. * This builds on the @FileGenerator and @ResolverSettings classes */ class ResolvConfFile : public FileGenerator, public ResolverBackendInterface { public: typedef RCPtr Ptr; /** * Instantiate a resolv.conf parser * * @param filename std::string of full path to the resolv.conf * file to parse * @param backup bool, if a backup should be made automatically * on overwrites (default: false) */ ResolvConfFile(const std::string &filename, const std::string &backup_filename = ""); ~ResolvConfFile(); /** * Retrieve information about the configured resolver backend. * Used for log events * * @return Returns a constant std::string with backend details. */ const std::string GetBackendInfo() const noexcept override; /** * Retrieve when the backend can apply the DNS resolver settings. * Normally it is applied before the tun interface configuration, * but some backends may need information about the device to * complete the configuration. * * For the ResolvConfFile implementaion, this will always return * MODE_PRE, where resolver settings will be applied before the * tun interface is configured. * * @returns NetCfg::DNS:ApplySettingsMode */ const ApplySettingsMode GetApplyMode() const noexcept override; /** * Add new DNS resolver settings. This may be called multiple times * in the order it will be processed by the resolver backend. * * @param settings A ResolverSettings::Ptr object containing the * DNS resolver configuraiton data */ void Apply(const ResolverSettings::Ptr settings) override; /** * Completes the DNS resolver configuration by performing the * changes on the system. * * @param signal Pointer to a NetCfgSignals object where * "NetworkChange" signals will be issued */ void Commit(NetCfgSignals *signal) override; /** * Restore the backup resolv.conf file if present */ void Restore(); /** * Retrieve all loaded and configured DNS servers * * @return std::vector containing list of DNS servers */ const std::vector GetNameServers(bool only_sys = false); #ifdef ENABLE_DEBUG /** * Misc debug methods used by test programs */ void Debug_Fetch(); void Debug_Write(); std::vector Debug_Get_dns_servers(); std::vector Debug_Get_search_domains(); virtual std::string Dump(); #endif private: std::mutex change_guard; std::vector unprocessed_lines; std::vector vpn_name_servers; std::vector vpn_name_servers_removed; std::vector vpn_search_domains; std::vector vpn_search_domains_removed; std::vector sys_name_servers; std::vector sys_search_domains; std::vector notification_queue; bool dns_scope_non_global = false; unsigned int modified_count = 0; /** * Extremely simplistic resolv.conf parser. It extracts the * information it needs and preserves everything else (except * comment lines) if the file gets regenerated. This parser * does not preserve any specific order between various options * in the file. */ void parse(); /** * Generates the contents needed for a file write (@Write()) * The data to be written to disk will be in the resolv.conf format */ void generate(); }; } // namespace DNS } // namespace NetCfg