BUUCTF：[羊城杯 2020]image_rar

Posted 2021-07-30 末 初

binwalk分析xiao_mi2.mp4发现很多压缩包，压缩了很多图片


将xiao_mi2.mp4修改后缀改为xiao_mi2.zip

得到一个hint，但这个压缩包密码并不是指当前的zip压缩包

继续往后看，解压这些图片之后发现里面只有65.jpg显示不正常

010 Editor打开65.jpg

文件头ara!，非常类似rar压缩包的文件头Rar!，修改文件头为Rar!(52 61 72 21)

并修改后缀为.rar，即可打开

有密码，hint的密码指的是rar的密码

压缩包密码（6位）：GWxxxx
后面可能会用到的哦

而且还是RAR5，ARCHPR无法爆破RAR5的密码。

利用rar2john提取hash

root@mochu7-pc:/mnt/c/Users/Administrator/Downloads# rar2john 65.rar
65.rar:$rar5$16$a2dce3925af59efb2df9851dbfc24fb1$15$bb005ea8f91bf0356c8dddcfa41ac4cb$8$62293dc5e26e9e7f
root@mochu7-pc:/mnt/c/Users/Administrator/Downloads#

然后利用hashcat爆破hash

PS D:\\Tools\\Misc\\hashcat-6.2.2> .\\hashcat.exe -m 13000 -a 3 '$rar5$16$a2dce3925af59efb2df9851dbfc24fb1$15$bb005ea8f91bf0356c8dddcfa41ac4cb$8$62293dc5e26e9e7f' GW?a?a?a?a
hashcat (v6.2.2) starting...

Successfully initialized NVIDIA CUDA library.

Failed to initialize NVIDIA RTC library.

* Device #1: CUDA SDK Toolkit not installed or incorrectly installed.
             CUDA SDK Toolkit required for proper device support and utilization.
             Falling back to OpenCL runtime.

* Device #2: Unstable OpenCL driver detected!

This OpenCL driver may fail kernel compilation or produce false negatives.
You can use --force to override, but do not report related errors.

nvmlDeviceGetFanSpeed(): Not Supported

OpenCL API (OpenCL 1.2 CUDA 11.1.114) - Platform #1 [NVIDIA Corporation]
========================================================================
* Device #1: GeForce GTX 1050, 3328/4096 MB (1024 MB allocatable), 5MCU

OpenCL API (OpenCL 3.0 ) - Platform #2 [Intel(R) Corporation]
=============================================================
* Device #2: Intel(R) UHD Graphics 630, skipped

Minimum password length supported by kernel: 0
Maximum password length supported by kernel: 256

Hashes: 1 digests; 1 unique digests, 1 unique salts
Bitmaps: 16 bits, 65536 entries, 0x0000ffff mask, 262144 bytes, 5/13 rotates

Optimizers applied:
* Zero-Byte
* Single-Hash
* Single-Salt
* Brute-Force
* Slow-Hash-SIMD-LOOP

Watchdog: Temperature abort trigger set to 90c

Host memory required for this attack: 87 MB

[s]tatus [p]ause [b]ypass [c]heckpoint [f]inish [q]uit =>

Session..........: hashcat
Status...........: Quit
Hash.Name........: RAR5
Hash.Target......: $rar5$16$a2dce3925af59efb2df9851dbfc24fb1$15$bb005e...6e9e7f
Time.Started.....: Fri Jul 02 21:04:28 2021 (2 secs)
Time.Estimated...: Fri Jul 02 23:44:57 2021 (2 hours, 40 mins)
Kernel.Feature...: Pure Kernel
Guess.Mask.......: GW?a?a?a?a [6]
Guess.Queue......: 1/1 (100.00%)
Speed.#1.........:     8460 H/s (9.29ms) @ Accel:4 Loops:128 Thr:1024 Vec:1
Recovered........: 0/1 (0.00%) Digests
Progress.........: 0/81450625 (0.00%)
Rejected.........: 0/0 (0.00%)
Restore.Point....: 0/81450625 (0.00%)
Restore.Sub.#1...: Salt:0 Amplifier:0-1 Iteration:25472-25600
Candidate.Engine.: Device Generator
Candidates.#1....: GWEERA -> GW#cke
Hardware.Mon.#1..: Temp: 60c Util: 99% Core:1683MHz Mem:3504MHz Bus:8

Started: Fri Jul 02 21:04:25 2021
Stopped: Fri Jul 02 21:04:32 2021
PS D:\\Tools\\Misc\\hashcat-6.2.2>

• -m指定爆破文档类型

- [ Hash modes ] -

      # | Name                                                | Category
  ======+=====================================================+======================================
  13000 | RAR5                                                | Archives

• -a指定爆破模式

- [ Attack Modes ] -

  # | Mode
 ===+======
  0 | Straight
  1 | Combination
  3 | Brute-force
  6 | Hybrid Wordlist + Mask
  7 | Hybrid Mask + Wordlist
  9 | Association

• GW?a?a?a，?a包含大小写字母、数字及特殊字符

爆破出来密码为：GW5!3#

解压得到文件flag

添加后缀.png即可

flag{R3fresh_1s_so_Cool}