> For the complete documentation index, see [llms.txt](https://writeups.ayweth20.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://writeups.ayweth20.com/2023/404ctf-2023/programmation/des-mots-des-mots-des-mots.md).
# Des mots, des mots, des mots
**Catégorie:** Programmation - **Difficulté:** Difficile
**Description:**
Netcat : *`nc challenges.404ctf.fr 30980`*
**Solution:**
Pour ce challenge, nous devions dans un premier répondre à 4 "énigmes" donnant les différentes règles à implémenter dans notre script :
Après avoir répondu à toutes les règles pas simples à comprendre pour un être humain (normalement constitué :joy:), nous pouvons les donner à un outil tel que Copilot afin qu'il nous aide à créer le bon code.\
Pour ce faire, nous commençons par une base de pwntool pour récupérer et renvoyer les réponses puis ensuite générer des fonctions pour chaque règle.
Voici donc le code utilisé pour ce challenge :
```python
from pwn import *
n = remote("challenges.404ctf.fr",30980)
voyelles = "aeiouyAEIOUY"
consonnes = "bcdfghjklmnpqrstvwxzBCDFGHJKLMNPQRSTVWXZ"
alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
def isvoy(letter):
if(letter in voyelles):
return 1
return 0
def nb_consonnes(str1):
res = 0
for i in str1:
if(i in consonnes):
res += 1
return res
def find_prev_voy(letter):
ind = alphabet.index(letter)
for i in range(ind - 1,-1,-1):
if(alphabet[i] in voyelles):
return alphabet[i]
def sort_word(word):
char_counts = {}
for char in word:
char_counts[char] = char_counts.get(char, 0) + 1
sorted_word = sorted(word, key=lambda char: (-char_counts[char], ord(char)))
return ''.join(sorted_word)
def rule1(str1):
str1 = "".join([chr(i) for i in reversed(str1)])
return str1
def rule2(res):
longueur = len(res)
if longueur % 2 == 0:
moitie = longueur // 2
partie1 = res[:moitie]
partie2 = res[moitie:]
mot_modifie = partie2 + partie1
else:
lettre_centrale = longueur // 2
mot_modifie = res.replace(res[lettre_centrale], "")
return mot_modifie
def rule3(t):
gg = t.decode()
gg = [ord(i) for i in gg]
gg = rule1(gg)
gg = rule2(gg)
print(gg)
if(len(gg) >= 3):
if(gg[2] in consonnes):
voy = []
t = list(t.decode())
r = list(t)
for i in r:
if(i in voyelles):
voy.append(i)
voy.insert(len(voy),voy[0])
voy = voy[1:]
ind = 0
for i in range(0,len(t)):
if(t[i] in voyelles):
r[i] = voy[ind % len(voy)]
ind += 1
r = [ord(i) for i in r]
r = rule1(r)
r = rule2(r)
return r
else:
voy = []
t = list(t.decode())
r = list(t)
for i in r:
if(i in voyelles):
voy.append(i)
voy.insert(0,voy[len(voy)-1])
voy = voy[:len(voy)-1]
ind = 0
for i in range(0,len(t)):
if(t[i] in voyelles):
r[i] = voy[ind % len(voy)]
ind += 1
r = [ord(i) for i in r]
r = rule1(r)
r = rule2(r)
return r
else:
return gg
def rule4(t):
r = list(t)
i = 0
while(i != len(r)):
if(r[i] in consonnes):
vp = ord(find_prev_voy(r[i]))
s = 0
for j in range(i-1,-1,-1):
s += ord(r[j]) * 2**(i-j) * isvoy(r[j])
a = ((vp + s) % 95) + 32
r.insert(i+1,chr(a))
i += 1
return r
for i in range(100):
t = n.recv()
tt = t
print(t.decode("utf-8"))
if(i == 0):
n.sendline(b"cosette")
if(i == 1):
n.sendline(b"ettesoc")
if(i == 2):
t = t[t.index(b"e : ") + 5:]
t = t[:t.index(b"}\n>>")]
t = rule1(t)
t = rule2(t)
n.sendline(t.encode())
if(i == 3):
t = t[t.index(b"e : {") + 5:]
t = t[:t.index(b"}\n>>")]
t = rule3(t)
n.sendline(t.encode())
if(i == 4):
t = t[t.index(b"e : {") + 5:]
t = t[:t.index(b"}\n>>")]
r = rule3(t)
r = "".join(rule4(r))
r = sort_word(r)
n.sendline(r.encode())
print(r)
if(i == 5):
#t = t.decode("utf-8")
t = t[t.index(b"Entr") + 11:]
t = t[:t.index(b"}")]
t = t.split(b" ")
res = ""
print(t,len(t))
c = 0
for i in t:
r = rule3(i)
r = "".join(rule4(r))
r = sort_word(r)
res += r + " "
c += 1
print(c)
print(res)
res = res[:len(res)-1]
n.sendline(res.encode())
```
Une fois lancer, le script va répondre à toutes les questions du bot et nous renvoyer le flag à la fin :
Ce challenge n'était pas le plus simple étant donné la "complexité" des règles à respecter.
🚩 FLAG
```
404CTF{:T]cdeikm_)W_doprsu_nt_;adei}
```
---
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