misc/miracle

miracle/Dockerfile

@@ -0,0 +1,15 @@
+FROM node:20.14
+
+RUN apt-get update && apt-get install -y curl gcc wget && apt-get clean && rm -rf /var/lib/apt/lists/* \
+    && wget -O ynetd.c https://raw.githubusercontent.com/johnsonjh/ynetd/e6fd08f8f5d0c6b8c18d645957e30ce012536ed4/ynetd.c \
+    && echo "ec7509dec7737da54f8b18e1b5ba935d657f9f016c36cfc9ac08f9952373226f  ynetd.c" | sha256sum -c \
+    && gcc -o ynetd ynetd.c && chmod +x ./ynetd && mv ynetd /usr/local/bin/ynetd && rm ynetd.c \
+    && export PATH=$PATH:/usr/local/bin
+
+WORKDIR /app
+
+COPY . /app/
+
+EXPOSE 8898
+
+ENTRYPOINT ["ynetd", "-p", "8898", "node main.js"]

miracle/chall.yaml

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+name: Miracle 
+categories:
+  - misc
+value: 50
+flag:
+  file: ./flag.txt
+description: |-
+  You'll need a miracle to get this flag. The server requires you to solve an easy addition problem, but you only
+  get the flag if the bits magically flip to form another answer.
+hints: []
+files:
+  - src: ./main.js
+  - src: ./eslint.config.mjs
+authors:
+  - Mudasir
+visible: true
+deploy:
+  nc:
+    build: .
+    expose: 8898/tcp

miracle/eslint.config.mjs

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+import globals from "globals";
+import pluginJs from "@eslint/js";
+
+
+export default [
+  {files: ["**/*.js"], languageOptions: {sourceType: "commonjs"}},
+  {languageOptions: { globals: globals.browser }},
+  pluginJs.configs.recommended,
+  {
+    rules: {
+        "no-unused-vars": "error",
+        "no-octal": "error",
+        "for-direction": "error",
+        "getter-return": "error",
+        "no-async-promise-executor": "error",
+        "no-compare-neg-zero": "error",
+        "no-cond-assign": "error",
+        "no-constant-condition": "error",
+        "no-control-regex": "error",
+        "no-dupe-args": "error",
+        "no-dupe-keys": "error",
+        "no-duplicate-case": "error",
+        "no-empty": "error",
+        "no-empty-character-class": "error",
+        "no-ex-assign": "error",
+        "no-extra-boolean-cast": "error",
+        "no-extra-semi": "error",
+        "no-invalid-regexp": "error",
+    }
+  }
+];

miracle/flag.txt

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+bcactf{j$_is_W3Ird_?rfuhie4923}

miracle/main.js

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+const readline = require("readline");
+const fs = require("fs");
+
+async function sleep(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+// thanks chatgpt
+function printWithoutNewline(text) {
+  process.stdout.write(text);
+}
+
+function prompt(question) {
+  const rl = readline.createInterface({
+    input: process.stdin,
+    output: process.stdout,
+  });
+
+  return new Promise((resolve) => {
+    rl.question(question, (answer) => {
+      rl.close();
+      resolve(answer);
+    });
+  });
+}
+//end thanks chatgpt
+
+const flag = fs.readFileSync("flag.txt", "utf8");
+
+async function run() {
+  const name = await prompt("What is your name?\n") ?? "Harry";
+  const ans = await prompt("What is 55+22?\n") ?? "0";
+  if (eval("Number(ans)") === 77) {
+    console.log("Correct!");
+    console.log("Waiting for bits to flip...");
+    for (let i = 0; i < 10; i++) {
+      printWithoutNewline("...");
+      await sleep(300);
+    }
+    console.log("\n");
+    if (eval(ans) === 63) {
+      console.log(`You made those bits flip?? You're a wizard ${name}! `);
+      console.log(`Here's your flag: ${flag}`);
+    } else {
+        console.log("You didn't make the bits flip. Too bad ");
+    }
+  } else {
+    console.log("wow you suck at math.");
+  }
+  process.exit(1);
+}
+
+run();