android8.0证书安装

2023-10-18 14:13:14 浏览数 (1)

mobile1(gctf)

下载下来是个apk

jadk打开查看源码

有两个关键方法

代码语言：javascript复制

public static void main(String[] args){
        TestActivity TestActivity=new TestActivity();
        System.out.println(String.valueOf(TestActivity.checkSN(“Tenshine”,“Tenshine”)));
    }
    private boolean checkSN(String userName, String sn) {
        if (userName == null) {
            return false;
        }
        try {
//            if (userName.length() == 0 || sn == null || sn.length() != 22) {
//                return true;
//            }
            MessageDigest digest = MessageDigest.getInstance(“MD5”);
            digest.reset();
            digest.update(userName.getBytes());
            String hexstr = toHexString(digest.digest(), “”);
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < hexstr.length(); i  = 2) {
                sb.append(hexstr.charAt(i));
            }
            System.out.println(“flag{“ sb.toString()  “}”);
            if ((“flag{“   sb.toString()   “}”).equalsIgnoreCase(sn)) {
                return true;
            }
            return false;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return false;
        }
    }
    private static String toHexString(byte[] bytes, String separator) {
        StringBuilder hexString = new StringBuilder();
        for (byte b : bytes) {
            String hex = Integer.toHexString(b & 255);
            if (hex.length() == 1) {
                hexString.append(‘0’);
            }
            hexString.append(hex).append(separator);
        }
        return hexString.toString();
    }

运行输出

获得flag

flag{bc72f242a6af3857}

false

-——————————–

append return string stringbuilder 源码

0 人点赞