按照着wp的思路，照着走一遍之后，大致理清楚了这道题的加密思路

通过wireshark我们可以将server发送到clientd的数据提取出来

通过分析我们可以得知，对于整个TCP流，是运用了rc4的加密方式，通过动态调试，我们可以调试出密钥为explorer

通过解密（解密后如下）我们我们可以看出这个是有着头的流量，因为前面我们知道，对于流量是有加密层的，因此我们不能直接看出流量中的数据是什么、

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我们对规律的0进行分开一下

我们可以得到如下图的流量

对于第一个字节表示得是数据长度

00000008 | 00000000 00000000 表示这里有0x08 = 8 bytes 的数据
0000000a | 00000001 00000000 b30c 表示这里有0x0a = 10 bytes 的数据，以此类推

对于第二数，我们可以发现其值为0,1,2,三个数，通过socket的server和client编写经验,再加上“猜”，我们可知其中，0代表开启一个stream（进行连接），1是正在传输数据，2代表接收完成，关闭。

第三个，通过我们编写一个客户端与服务端的经验，一个服务端一般会对应的接收来自多个客户端传入的数据，为了分辨传输给谁和谁传输的，就需要一个id进行识别，因此这里我们猜测这个是stream-id(流id）

后面的数据自然而然就知道是我们传输的数据了。

由此我们的协议组成就是：**数据总长度(**4 bytes) + 状态表示 (4 bytes) + 流id (4 bytes) + 传输数据(x bytes)

密钥对接

通过提取传入的字符串，我们可以发现，rsa加密后的公钥与私钥

pubkey: |
    -----BEGIN RSA PUBLIC KEY----
    MIIBCgKCAQEA231sNrX6WxlQpfsy8u6VR9rw4H4lY93fspAmXefjDhQhYCPM+Syp
    (..)
    H5YyTi1cOvMFsN+oPGxgBGpSqYCxmPwINwIDAQAB
    -----END RSA PUBLIC KEY-----

mkey: explorer

privkey: |
    -----BEGIN PRIVATE KEY-----
    MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQC93GDINPM6HX2+
    (..)
    p2eXdqH59DvauggbiS3h4p9k2kxWTocztarvdftMW0ncmA4yCKiUQEmWD784JCyx
    OupNNfr2rgViWggVBEtJUIg=
    -----END PRIVATE KEY-----

在key_exchange中，我们可以看到这里rand生成了数据存储在了，v59中16个字节

rand：Rust随机数库简介 | 子飞的网络日志 (chirsz.cc)

生成随机值 - Rust Cookbook 中文版 (rustwiki.org)

use rand::{thread_rng, Rng};
let mut rng = thread_rng();
let x: u128 = rng.gen();
println!("{}", x);

这里将我们的rand出来的16比特的数，进行了rsa加密，从而使得我们的key变成了256位的密钥

这里可以推测出是PublicKey（公钥加密）的RSA算法加密

(87条消息) 公开密钥加密之RSA算法【概念+计算+代码实现】_rsa算法代码_MIKE笔记的博客-CSDN博客

之后将server发送过来的密钥进行解密之后，异或上原本产生的16字节的随机数据，产生了新的密钥（也就是我们后面流量加密的密钥）

接着上一步，将异或后的数据进行sha-256加密，然后发送给server，双方进行对比验证，确定是同一个密钥，从而完成了密钥交换

对包加密的传输

这里我们很容易的分辨出是进行了aes-cbc模式下的加密

对于前面得到rc4解密后的流量数据，进行分组之后，我们分析其后面的发送数据与协议。

我们可以在协议中观察到以下几点:

1、第7行的数据与我们在前面的例子中交换密钥时得到的SHA256哈希值相配:118d31c061936b811327f1645c9f8deef4c6628e3ee21b39950213ddd0cf2141

2、该行之后的所有内容都可能是AES加密的，而该行之前的内容将是RSA加密并与密钥交换相关。

3、第2、3、4、5行消息长度分别为(64+64+64+64= 256 bytes=2048)位 = RSA 密钥大小）

被加密的流量也有流量头，前4字节的代表数据长度的值，其后跟着一个16字节的当前加密所用的iv。因此我们可以使用aes_128_c进行bc解密。

总的加密思路：

首先就是收包，对包进行rc4的最外层解密，然后就是进行密钥交换，双方通过随机数生成16字节的随机密钥，首先进行rsa公钥加密，加密之后，将密钥发送给对方，双方进行解密之后，将获取的对方的随机数与自己本身产生的随机数进行异或，生成派生密钥，然后将生成的派生密钥进行sha-256加密之后，向对方发送过去，双方进行验证是否为同一密钥。之后就通过派生密钥，按照着传输协议，将数据流量进行解密，从而得到真正的发送原文（flag）。

参考文章：

(87条消息) 2023 RealWorldCTF “Ferris proxy”逆向题分析（不算wp）_sln_1550的博客-CSDN博客

Realworld CTF 2023 Ferris_proxy Writeup-CTF对抗-看雪-安全社区|安全招聘|kanxue.com

https://vrls.ws/posts/2023/01/real-world-ctf-2023-ferris-proxy-reverse-engineering