ISC2016训练赛 phrackCTF--Smali

测试文件：https://static2.ichunqiu.com/icq/resources/fileupload/phrackCTF/REVERSE/Crackme.smali

 

参考资料：https://www.cnblogs.com/lz2017/p/6917049.html

 

1.文件分析

使用SmaliJavaUI反编译文件，得到

 1 /**
 2   * Generated by smali2java 1.0.0.558
 3   * Copyright (C) 2013 Hensence.com
 4   */
 5 
 6 package net.bluelotus.tomorrow.easyandroid;
 7 
 8 import android.util.Base64;
 9 import java.io.PrintStream;
10 import java.security.NoSuchAlgorithmException;
11 import javax.crypto.NoSuchPaddingException;
12 import java.security.InvalidKeyException;
13 import javax.crypto.IllegalBlockSizeException;
14 import javax.crypto.BadPaddingException;
15 import javax.crypto.spec.SecretKeySpec;
16 import javax.crypto.Cipher;
17 import java.security.Key;
18 import java.security.GeneralSecurityException;
19 
20 public class Crackme {
21     private String str2 = "cGhyYWNrICBjdGYgMjAxNg==";
22     
23     public Crackme() {
24         GetFlag("sSNnx1UKbYrA1+MOrdtDTA==");
25     }
26     
27     private String GetFlag(String p1) {//将上面两段字符串经过base64解密
28         byte[] "content" = Base64.decode(p1.getBytes(), 0x0);
29         String "kk" = new String(Base64.decode(str2.getBytes(), 0x0));
30         System.out.println(decrypt("content", "kk"));
31         return null;
32     }
33     
34     private String decrypt(byte[] p1, String p2) {//将解密后的序列，一段用来生成key，一段作为被AES加密的字符串。
35         String "m" = 0x0;
36         try {
37             byte[] "keyStr" = p2.getBytes();
38             SecretKeySpec "key" = new SecretKeySpec("keyStr", "AES");
39             Cipher "cipher" = Cipher.getInstance("AES/ECB/NoPadding");
40             "cipher".init(0x2, "key");
41             byte[] "result" = "cipher".doFinal(p1);
42             return "m";
43         } catch(NoSuchPaddingException "e") {
44             "e".printStackTrace();
45         }
46         return  "m";
47     }
48 }

 

2.脚本获取

from Crypto.Cipher import AES
import base64

key = base64.b64decode("cGhyYWNrICBjdGYgMjAxNg==")
str1 = base64.b64decode("sSNnx1UKbYrA1+MOrdtDTA==")

cryptor = AES.new(key, AES.MODE_ECB)
result = cryptor.decrypt(str1)
print(result)

 

 

3.get flag！

PCTF{Sm4liRiver}