從main函數開始看，發現在check的時候加載了assets?錄中的?個dex?件，跟進發現在FileUtils??。

主要邏輯在copyfile函數之中，進行異或處理，注意這里的以1024?組進?解密就可以。

key=b'vn2022' f1=open(r'ooo','rb+') f2=open(r'dex','wb+') while True:t=[]s=f1.read(1024)if len(s)==0:breakfor i in range(len(s)):t.append(s[i]^key[i%len(key)])f2.write(bytes(t))

?得到dex我們用jadx打開，主要加密邏輯為xxtea。

?而且對加密數據進行了小端序轉int

a=b'H4pPY_VNCTF!!OvO' r=[0]*4 for i in range(16):i2 = i >> 2r[i2] = r[i2] | ((a[i] & 255) << ((i & 3) << 3)) for i in r:print(hex(i),end=',') print() enc=[0]*11 c=[0x44 ,0x27 ,0xffffffa4 ,0x6c ,0xffffffae ,0xffffffee ,0x48 ,0xffffffc9 ,0x4a ,0xffffffc8 ,0x26 ,0x0b ,0x3c ,0x54 ,0x61 ,0xffffffd8 ,0x57 ,0x47 ,0x63 ,0xffffffae ,0x78 ,0x68 ,0x2f ,0xffffffb9 ,0xffffffc6 ,0xffffffc7 ,0x00 ,0x21 ,0x2a ,0x26 ,0xffffffd4 ,0xffffffd9 ,0xffffffc4 ,0x71 ,0xfffffffe ,0x5c ,0xffffffb5 ,0x76 ,0xffffffb3 ,0x32 ,0xffffff87 ,0x2b ,0x20 ,0xffffff96] for i in range(len(c)):i2 = i >> 2enc[i2] = enc[i2] | ((c[i] & 255) << ((i & 3) << 3)) for i in enc:print(hex(i),end=',')

得到密鑰和密文

再寫腳本解密

#include <stdio.h> #include <stdint.h> #include <windows.h> #define DELTA 0x9e3779b9 #define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (key[(p&3)^e] ^ z))) void btea(uint32_t *v, int n, uint32_t const key[4]) {uint32_t y, z, sum;unsigned p, rounds, e;if (n > 1) /* Coding Part */{rounds = 6 + 52/n;sum = 0;z = v[n-1];do{sum += DELTA;e = (sum >> 2) & 3;for (p=0; p<n-1; p++){y = v[p+1];z = v[p] += MX;}y = v[0];z = v[n-1] += MX;}while (--rounds);}else if (n < -1) /* Decoding Part */{n = -n;rounds = 6 + 52/n;sum = rounds*DELTA;y = v[0];do{e = (sum >> 2) & 3;for (p=n-1; p>0; p--){z = v[p-1];y = v[p] -= MX;}z = v[n-1];y = v[0] -= MX;sum -= DELTA;}while (--rounds);} } int main() {uint32_t key[4] = {1349530696, 1314283353, 558257219, 1333153569};uint32_t v[12] = {1822697284, 3377000110, 187091018, 3630257212, 2925741911, 3106891896, 553699270, 3654559274, 1560179140, 850622133, 2518690695, 0};btea(v, -11, key);printf("%s", (char*)v);return 0; }

總結

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