Little Mix

• medium

Just a little mix, but not this one: https://www.youtube.com/watch?v=MkElfR_NPBI

nc challenges.crysys.hu 5029

author: tk

Writeup

Connecting to the service, we can see that it’s a quiz program with different questions. Most of them are constant, and can easily solved by some googling or some educated guesswork. (actually the only random ones were the XOR, witch is easily doable by hand, and RSA, witch always gave the same answer)

You can make 2 mistakes before the program disconnects and you have to start over.

After answering all the questions, you just get the flag:

Just a little mix!
A SecChallenge edition!
Just answer 3 questions in all 6 categories correctly to get the flag!

18 questions remaining!

*** Crypto section ***
1: What part of the CIA triangle an AEAD cipher does not provide?
>>> availability
✔️ 🥇

17 questions remaining!

2: The string "admin=0" is XOR encrypted, the ciphertext is the following "b546b355051e19" (in hex). Your task is to give the XOR encrypted "admin=1" string (in hex).
>>> b546b355051e18
✔️ 🥳

16 questions remaining!

3: What is the ASCII printable plaintext, which is encrypted with textbook RSA using the following parameters:
p = 97895746752372891871283422027043042061614577686530065446233616612333423604934011843200996680487677526879789179586786039582506950509293024631727783070830925085314167678657690804225291586344823854887079536113937037179906217782966484499059668578707953739801639859146969751084700674958632822922091962540104071107
q = 108719296446064498008143737396004668132941036811186871376825445279508373750934080199890641861482658544845078428030961057373250464329294016345344451097991091038538954298752426636326436299942507818022252246943632901199425784112349575799549930600155586758230625799969689251054533889726886643889939907241885966637
e = 65537
cipher= 9534253136837180343463316267358545731384733625253109532045949620182315193650675958090742196052854738610908779615078112746573354162378400699719906765433050694003554324613313237074810534764528108496909446295227457831456477267955873650135006449729874775897840044072326913892935515454141625792274255085020780255954978618532508049237577319755709709637515962534359078653590184914403962255630257139554819146009234217179432624111505682768200438271796107141098570628796900513138976107492166976162378470447447562275303831197174934445230880665933135980096360622624761929812481245950597156173863459145479543471550126911750170606
>>> textbook_rsa_is_easy
✔️ 👍

15 questions remaining!

*** Hardware section ***
4: I'm a one master, many slave protocol, I'm not a parallel protocol, I have a line called MOSI, who am I?
>>> spi
✔️ 🏆

14 questions remaining!

5: I have a direct current circuit. R2 and R3 are connected parallely to each other and R1 is connected serially to R2 and R3. R1 = 15 Ohm, R2 = 10 Ohm, R3 = 30 Ohm. A U = 15 V voltage source is connected serially to R1. What current flows through R2?
>>> 500mA
✔️ 🍻

13 questions remaining!

6: What is the version of the "busybox" software/program in the following router firmware?
Download site: https://github.com/praetorian-inc/DVRF/blob/master/Firmware/DVRF_v03.bin
You might need some firmware analysis.
>>> 1.7.2
✔️ 🤓

12 questions remaining!

*** Misc section ***
7: Which was the best CTF team in 2020?
>>> perfect blue
✔️ 💰

11 questions remaining!

8: Which software was hacked in the biggest supply chain attack in 2020?
>>> solarwinds
✔️ 🏅

10 questions remaining!

9: What is the IPv6 address of an authoritative DNS server of the "crysys.hu" domain?
>>> 2001:4c48:2:a341:204:75ff:fe7c:c901
✔️ 🏆

9 questions remaining!

*** Pwn section ***
10: Which binary cannot be used to get a shell: more, less, nmap, tail, php, vi?
>>> tail
✔️ 🍻

8 questions remaining!

11: I'm an Android LIBC allocator, a bucket allocator, and I can be used to allocate regions, who am I?
>>> jemalloc
✔️ 🏅

7 questions remaining!

12: If no optimization (e.g. stack layout modification etc.) happens during compilation, what string should be presented
 to this program, to get the flag?

#include <stdlib.h>
#include <string.h>
#include <stdio.h>

int main(int argc, char **argv)
{
    char passwd[64]={0};
    char buffer[16];

    passwd[0] = '\0';
    gets(buffer);

    if(strcmp(passwd, "ss4pdr0w") == 0) {
        printf("cd21{not_a_valid_flag}");
    } else {
        printf("No flag for you\n");
    }
    exit(0);
}

>>> AAAAAAAAAAAAAAAAss4pdr0w
✔️ 🏅

6 questions remaining!

*** Reverse section ***
13: Which tool can be used to trace library calls of an ELF binary on Linux?
>>> ltrace
✔️ 👑

5 questions remaining!

14: What is the machinecode in hex of the following snippet (x86, 32 bits)?
mov esp ebp
pop ebp
ret
>>> 89EC5DC3
✔️ 👑

4 questions remaining!

15: I've extracted the "main" function from an x86-64 ELF binary. What does it print?
554889e54883ec30897ddc488975d048b86a7471715b5c595b48ba596a5f58536b2a27488945e0488955e8c745f04f525d5166c745f45100c745fc00000000c745fc00000000eb208b45fc48980fb64405e089c28b45fc01d089c28b45fc4898885405e08345fc01837dfc147eda488d45e04889c7e87dfeffffb800000000c9c3
(Hint: the only "call" in the assembly is just a "puts" call)
>>> jtqq[\Y[Yj_XSk*'OR]QQ
❌ 🆘

15: I've extracted the "main" function from an x86-64 ELF binary. What does it print?
554889e54883ec30897ddc488975d048b86a7471715b5c595b48ba596a5f58536b2a27488945e0488955e8c745f04f525d5166c745f45100c745fc00000000c745fc00000000eb208b45fc48980fb64405e089c28b45fc01d089c28b45fc4898885405e08345fc01837dfc147eda488d45e04889c7e87dfeffffb800000000c9c3
(Hint: the only "call" in the assembly is just a "puts" call)
>>> just_a_basic_x86_code
✔️ 👍

3 questions remaining!

*** Web section ***
16: What is not the requirement of the Application Transport Security in iOS?
    a) The certificate must use SHA-256 or greater.
    b) The server certificate must be signed with either at least 2048-bit RSA, or at least 256-bit ECC.
    c) Data must be exchanged using either the AES-128 or the AES-256 symmetric cipher.
    d) The link must support perfect forward secrecy through ECDHE key exchange.
    e) The connection must use TLS 1.3.
>>> a
❌ ❌

16: What is not the requirement of the Application Transport Security in iOS?
    a) The certificate must use SHA-256 or greater.
    b) The server certificate must be signed with either at least 2048-bit RSA, or at least 256-bit ECC.
    c) Data must be exchanged using either the AES-128 or the AES-256 symmetric cipher.
    d) The link must support perfect forward secrecy through ECDHE key exchange.
    e) The connection must use TLS 1.3.
>>> e
✔️ 👍

2 questions remaining!

17: What web attack/vulnerability connects Han Solo and the Transfer-Encoding header?
>>> smuggling
✔️ 🤓

1 questions remaining!

18: What does the following JavaScript code print?
[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]][([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((!![]+[])[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+!+[]]+(+[![]]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+!+[]]]+(!![]+[])[!+[]+!+[]+!+[]]+(+(!+[]+!+[]+!+[]+[+!+[]]))[(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([]+[])[([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]][([][[]]+[])[+!+[]]+(![]+[])[+!+[]]+((+[])[([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]+[])[+!+[]+[+!+[]]]+(!![]+[])[!+[]+!+[]+!+[]]]](!+[]+!+[]+!+[]+[!+[]+!+[]])+(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]])()([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]][([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((!![]+[])[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+!+[]]+([]+[])[(![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(!![]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]()[+!+[]+[!+[]+!+[]]]+((!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(+(+!+[]+[+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+[!+[]+!+[]]+[+[]])+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[+[]]+(!![]+[])[+[]]+[!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(![]+[])[+[]]+([][[]]+[])[+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[+!+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+[!+[]+!+[]+!+[]+!+[]]+[!+[]+!+[]]+(!![]+[])[+[]]+[!+[]+!+[]+!+[]+!+[]+!+[]]+[+!+[]])[(![]+[])[!+[]+!+[]+!+[]]+(+(!+[]+!+[]+[+!+[]]+[+!+[]]))[(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([]+[])[([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+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>>> this_is_jsfuck
✔️ 🏆

0 questions remaining!

You've finished our little mix!
Here is your reward: cd21{...}