BreizhCTF - Net Net (Reverse)

Reverse simpliste d’un fichier .NET

Je n’ai malheureusement pas sauvegardé l’énoncé des épreuves
net_net.exe

Lookin’ for what

switch@XXX:/mnt/c/Users/switch/Desktop/breizh$ file breizh.exe
breizh.exe: PE32 executable (console) Intel 80386 Mono/.Net assembly, for MS Windows

Oh un fichier .NET, vite utilisons l’excellent tools de Jetbrain (ça devient une habitude chez eux ahah) : dotPeek

What, really ?

Extrait du code source du programme

Console.WriteLine(str1);
Console.WriteLine("Hold on! Your name first:");
Console.WriteLine("Hi " + Console.ReadLine() + " how are you?");
Console.WriteLine("Enter now your password and I'll let you in (huuum):");
string str3 = Console.ReadLine();
string str5 = "secret_harcoded_password";

if (str3 == str5)
      {
        Console.WriteLine("WowwW! How did you find me...!");
        Console.WriteLine("...Ok, so here Your flag is:" + str2 + "So_Damn_Easy_Obfuscate_NET_Prog!!!}");
      }

Le password était simplement hardcoded, seul le flag était généré à la volé via du base64

#BREIZHCTF{This year, let's come back to roots! Here is a NEaT prog}
Hold on! Your name first:
switch
Hi switch how are you?
Enter now your password and I'll let you in (huuum):
secret_harcoded_password
password
WowwW! How did you find me...!
...Ok, so here Your flag is:BZHCTF{So_Damn_Easy_Obfuscate_NET_Prog!!!}