misc/endianness

misc/endianness/flag.c

@@ -0,0 +1,134 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <ctype.h>
+#include <time.h>
+
+char *find_little_endian(const char *word)
+{
+    size_t word_len = strlen(word);
+    char *little_endian = (char *)malloc((2 * word_len + 1) * sizeof(char));
+
+    for (size_t i = word_len; i-- > 0;)
+    {
+        snprintf(&little_endian[(word_len - 1 - i) * 2], 3, "%02X", (unsigned char)word[i]);
+    }
+
+    little_endian[2 * word_len] = '\0';
+    return little_endian;
+}
+
+char *find_big_endian(const char *word)
+{
+    size_t length = strlen(word);
+    char *big_endian = (char *)malloc((2 * length + 1) * sizeof(char));
+
+    for (size_t i = 0; i < length; i++)
+    {
+        snprintf(&big_endian[i * 2], 3, "%02X", (unsigned char)word[i]);
+    }
+
+    big_endian[2 * length] = '\0';
+    return big_endian;
+}
+
+char *generate_random_word()
+{
+    printf("Welcome to the Endian CTF!\n");
+    printf("You need to find both the little endian and big endian representations of a word.\n");
+    printf("If you get both correct, you will receive the flag.\n");
+    srand(time(NULL));
+
+    int word_length = 5;
+    char *word = (char *)malloc((word_length + 1) * sizeof(char));
+
+    for (int i = 0; i < word_length; i++)
+    {
+        word[i] = (rand() % 26) + 'a';
+    }
+
+    word[word_length] = '\0';
+    return word;
+}
+
+int main()
+{
+    char *challenge_word = generate_random_word();
+    printf("Word: %s\n", challenge_word);
+    fflush(stdout);
+
+    char *little_endian = find_little_endian(challenge_word);
+    size_t user_little_endian_size = strlen(little_endian);
+    char user_little_endian[user_little_endian_size + 1];
+    bool correct_flag = false;
+
+    while (!correct_flag)
+    {
+        printf("Enter the Little Endian representation: ");
+        fflush(stdout);
+        scanf("%10s", user_little_endian);
+        for (size_t i = 0; i < strlen(user_little_endian); i++)
+        {
+            user_little_endian[i] = toupper(user_little_endian[i]);
+        }
+
+        if (strncmp(user_little_endian, little_endian, user_little_endian_size) == 0)
+        {
+            printf("Correct Little Endian representation!\n");
+            fflush(stdout);
+            correct_flag = true;
+        }
+        else
+        {
+            printf("Incorrect Little Endian representation. Try again!\n");
+            fflush(stdout);
+        }
+    }
+
+    char *big_endian = find_big_endian(challenge_word);
+    size_t user_big_endian_size = strlen(big_endian);
+    char user_big_endian[user_big_endian_size + 1];
+
+    bool final_flag = false;
+    while (!final_flag)
+    {
+        printf("Enter the Big Endian representation: ");
+        fflush(stdout);
+        scanf("%10s", user_big_endian);
+        for (size_t i = 0; i < strlen(user_big_endian); i++)
+        {
+            user_big_endian[i] = toupper(user_big_endian[i]);
+        }
+
+        if (strncmp(user_big_endian, big_endian, user_big_endian_size) == 0)
+        {
+            printf("Correct Big Endian representation!\n");
+            fflush(stdout);
+            final_flag = true;
+        }
+        else
+        {
+            printf("Incorrect Big Endian representation. Try again!\n");
+            fflush(stdout);
+        }
+    }
+
+    FILE *flag = fopen("flag.txt", "r");
+    if (flag == NULL)
+    {
+        printf("Flag not found. Please run this on the server\n");
+        fflush(stdout);
+        exit(0);
+    }
+
+    char flag_content[100];
+    fgets(flag_content, sizeof(flag_content), flag);
+    printf("Congratulations! You found both endian representations correctly!\n");
+    fflush(stdout);
+    printf("Your Flag is: %s\n", flag_content);
+    fflush(stdout);
+    exit(0);
+
+    return 0;
+}

misc/endianness/solve.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -p python3 -i python3 python3Packages.pwntools
+
+from pwn import *
+
+ADDR, PORT, *_ = "titan.picoctf.net 62735".split()
+
+def main():
+  r = remote(ADDR, PORT)
+
+  r.recvuntil(b'Word: ')
+  word = r.recvline().strip()
+
+  r.recvuntil(b'Enter the Little Endian representation: ')
+  little_endian = ''.join(hex(b)[2:] for b in reversed(word))
+  r.sendline(little_endian.encode())
+
+  r.recvuntil(b'Enter the Big Endian representation: ')
+  big_endian = ''.join(hex(b)[2:] for b in word)
+  r.sendline(big_endian.encode())
+
+  r.recvuntil(b'Your Flag is: ')
+  print(r.recvline().decode())
+
+  r.close()
+
+if __name__ == "__main__":
+    main()