176 lines
6.7 KiB
C++
176 lines
6.7 KiB
C++
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/**
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* D++ eval command example.
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* This is dangerous and for educational use only, here be dragons!
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*/
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#include <dpp/dpp.h>
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#include <fmt/format.h>
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#include <fstream>
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#include <iostream>
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/* We have to define this to make certain functions visible */
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#ifndef _GNU_SOURCE
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#define _GNU_SOURCE
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#endif
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#include <link.h>
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#include <dlfcn.h>
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#include "eval.h"
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/* This is an example function you can expose to your eval command */
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int test_function() {
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return 42;
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}
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/* Important: This code is for UNIX-like systems only, e.g.
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* Linux, BSD, OSX. It will NOT work on Windows!
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* Note for OSX you'll probably have to change all references
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* from .so to .dylib.
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*/
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int main() {
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dpp::cluster bot("token", dpp::i_default_intents | dpp::i_message_content);
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bot.on_log(dpp::utility::cout_logger());
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/* This won't work in a slash command very well yet, as there is not yet
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* a multi-line slash command input type.
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*/
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bot.on_message_create([&bot](const auto & event) {
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if (dpp::utility::utf8substr(event.msg.content, 0, 5) == "!eval") {
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/**
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* THIS IS CRITICALLY IMPORTANT!
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* Never EVER make an eval command that isn't restricted to a specific developer by user id.
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* With access to this command the person who invokes it has at best full control over
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* your bot's user account and at worst, full control over your entire network!!!
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* Eval commands are Evil (pun intended) and could even be considered a security
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* vulnerability. YOU HAVE BEEN WARNED!
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*/
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if (event.msg.author.id != dpp::snowflake(MY_DEVELOPER)) {
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bot.message_create(dpp::message(event.msg.channel_id, "On the day i do this for you, Satan will be ice skating to work."));
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return;
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}
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/* We start by creating a string that contains a cpp program for a simple library.
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* The library will contain one exported function called so_exec() that is called
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* containing the raw C++ code to eval.
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*/
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std::string code = "#include <iostream>\n\
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#include <string>\n\
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#include <map>\n\
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#include <unordered_map>\n\
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#include <stdint.h>\n\
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#include <dpp/dpp.h>\n\
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#include <dpp/nlohmann/json.hpp>\n\
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#include <fmt/format.h>\n\
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#include \"eval.h\"\n\
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extern \"C\" void so_exec(dpp::cluster& bot, dpp::message_create_t event) {\n\
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" + dpp::utility::utf8substr(
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event.msg.content,
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6,
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dpp::utility::utf8len(event.msg.content)
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) + ";\n\
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return;\n\
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}";
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/* Next we output this string full of C++ to a cpp file on disk.
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* This code assumes the current directory is writeable. The file will have a
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* unique name made from the user's id and the message id.
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*/
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std::string source_filename = std::to_string(event.msg.author.id) + "_" + std::to_string(event.msg.id) + ".cpp";
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std::fstream code_file(source_filename, std::fstream::binary | std::fstream::out);
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if (!code_file.is_open()) {
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bot.message_create(dpp::message(event.msg.channel_id, "Unable to create source file for `eval`"));
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return;
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}
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code_file << code;
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code_file.close();
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/* Now to actually compile the file. We use dpp::utility::exec to
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* invoke a compiler. This assumes you are using g++, and it is in your path.
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*/
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double compile_start = dpp::utility::time_f();
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dpp::utility::exec("g++", {
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"-std=c++17",
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"-shared", /* Build the output as a .so file */
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"-fPIC",
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std::string("-o") + std::to_string(event.msg.author.id) + "_" + std::to_string(event.msg.id) + ".so",
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std::to_string(event.msg.author.id) + "_" + std::to_string(event.msg.id) + ".cpp",
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"-ldpp",
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"-ldl"
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}, [event, &bot, source_filename, compile_start](const std::string &output) {
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/* After g++ is ran we end up inside this lambda with the output as a string */
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double compile_time = dpp::utility::time_f() - compile_start;
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/* Delete our cpp file, we don't need it any more */
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std::string del_file = std::string(getenv("PWD")) + std::to_string(event.msg.author.id) + "_" + std::to_string(event.msg.id) + ".cpp";
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unlink(del_file.c_str());
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/* On successful compilation g++ outputs nothing, so any output here is error output */
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if (output.length()) {
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bot.message_create(dpp::message(event.msg.channel_id, "Compile error: ```\n" + output + "\n```"));
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} else {
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/* Now for the meat of the function. To actually load
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* our shared object we use dlopen() to load it into the
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* memory space of our bot. If dlopen() returns a nullptr,
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* the shared object could not be loaded. The user probably
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* did something odd with the symbols inside their eval.
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*/
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std::string dl = std::string(getenv("PWD")) + std::to_string(event.msg.author.id) + "_" + std::to_string(event.msg.id) + ".so";
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auto shared_object_handle = dlopen(dl.c_str(), RTLD_NOW);
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if (!shared_object_handle) {
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const char *dlsym_error = dlerror();
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bot.message_create(dpp::message(event.msg.channel_id, "Shared object load error: ```\n" +
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std::string(dlsym_error ? dlsym_error : "Unknown error") +"\n```"));
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return;
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}
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/* This type represents the "void so_exec()" function inside
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* the shared object library file.
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*/
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using function_pointer = void(*)(dpp::cluster&, dpp::message_create_t);
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/* Attempt to find the function called so_exec() inside the
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* library we just loaded. If we can't find it, then the user
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* did something really strange in their eval. Also note it's
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* important we call dlerror() here to reset it before trying
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* to use it a second time. It's weird-ass C code and is just
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* like that.
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*/
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dlerror();
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function_pointer exec_run = (function_pointer)dlsym(shared_object_handle, "so_exec");
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const char *dlsym_error = dlerror();
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if (dlsym_error) {
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bot.message_create(dpp::message(event.msg.channel_id, "Shared object load error: ```\n" + std::string(dlsym_error) +"\n```"));
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dlclose(shared_object_handle);
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return;
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}
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/* Now we have a function pointer to our actual exec code in
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* 'exec_run', so lets call it, and pass it a reference to
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* the cluster, and also a copy of the message_create_t.
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*/
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double run_start = dpp::utility::time_f();
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exec_run(bot, event);
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double run_time = dpp::utility::time_f() - run_start;
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/* When we're done with a .so file we must always dlclose() it */
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dlclose(shared_object_handle);
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/* We are now done with the compiled code too */
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unlink(dl.c_str());
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/* Output some statistics */
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bot.message_create(dpp::message(event.msg.channel_id,
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"Execution completed. Compile time: " + std::to_string(compile_time) +
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"s, execution time " + std::to_string(run_time) + "s"));
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}
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});
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}
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});
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bot.start(dpp::st_wait);
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return 0;
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}
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