solved 1

4/level1/level1.c

@@ -0,0 +1,58 @@
+// gcc -o level1 -no-pie -fno-stack-protector level1.c
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+struct topic {
+  char question[64];
+  char answer[32];
+  int (*check_response)(struct topic *topic);
+};
+
+void win() {
+  char *argv[2];
+  argv[0] = "/bin/sh";
+  argv[1] = NULL;
+  execve(argv[0], argv, NULL);
+}
+
+int check_math_response(struct topic *topic) {
+  int answer = atoi(topic->answer);
+  if (answer == 0x7a69) {
+    puts("You got it.");
+    return 0;
+  } else {
+    puts("Try again.");
+    return 1;
+  }
+}
+
+int check_weather_response(struct topic *topic) {
+  if (!strcmp(topic->answer, "Yes\n")) {
+    puts("It's inevitable.");
+    return 0;
+  } else {
+    puts("Are you sure about that?");
+    return 1;
+  }
+}
+
+int main(int argc, char **argv) {
+  // Disable output buffering. Not part of the challenge.
+  setvbuf(stdout, NULL, _IONBF, 0);
+  setvbuf(stdin, NULL, _IONBF, 0);
+
+  struct topic topics[] = {
+      {"What is 3077 * 10 + 567?", "", check_math_response},
+      {"Will it ever rain this year?", "", check_weather_response}};
+
+  srand(time(NULL));
+  struct topic *topic = &topics[rand() % 2];
+
+  puts(topic->question);
+  fgets(topic->answer, sizeof(*topic), stdin);
+  printf("addr: %X\n", topic->check_response);
+  return topic->check_response(topic);
+}