OSEC

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ekg insecure temporary file creation and arbitrary code execution

From: ZATAZ Audits (exploitszataz.net)
Date: Tue Jul 05 2005 - 01:51:07 CDT


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ekg insecure temporary file creation and arbitrary code execution

Vendor: http://dev.null.pl/ekg/
Advisory: http://www.zataz.net/adviso/ekg-06062005.txt
Vendor informed: yes
Exploit available: no
Impact : high
Exploitation : high

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The vulnerabilities are caused due to temporary file being created
insecurely.
This can be exploited via symlink attacks in combination to create and
overwrite
arbitrary files with the privileges of the user running the affected
script and
also arbitrary command possible by spiking the temporary file.

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Versions:
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ekg <= 2005-06-05 22:03

##########
Solution:
##########

For the symlink attack use kernel patch such as grsecurity

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Timeline:
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Discovered : 2005-05-27
Vendor notified : 2005-06-06
Vendor response : no response
Vendor fix : no fix
Vendor Sec report (vendor-seclst.de) : 2005-06-27
Disclosure : 2005-07-04

#####################
Technical details :
#####################

Vulnerable code :
-----------------

In contrib/scripts/linki.py

95 def czyjest ():
96 if os.path.exists('/tmp/rmrmg_ekg_url'):
97 wejsc= open ('/tmp/rmrmg_ekg_url')
98 file = wejsc.readlines()
99 dlug=len(file)
100 wejsc.close()
101 #ekg.printf("generic", "liczność %d" %(dlug))
102 return file
103 else:
104 return 0

Then

35 def handle_keypress(meta, key):
36 if key == 269:
37 ekg.printf("generic", "wciśnieto F5")
38 nurl=czyjest()
39 if nurl == 0:
40 ekg.printf("generic", "nie ma zadnego adresu URL")
41 else:
42 dlug=len(nurl)
43 if dlug == 1:
44 ekg.printf("generic", "otwieram %s w nowej zakładce"
%(nurl[0]))
45 os.system("MozillaFirebird -remote
'openURL(%s,new-tab)'" %(nurl[0]))
46 os.system('rm /tmp/rmrmg_ekg_url')
47 else:
48 ekg.printf("generic", "linków mam %d" %(dlug))
49 wielejest(nurl)
50 ekg.printf("generic", "otwieram %s w nowej zakładce"
%(nurl[0]))
51 os.system("MozillaFirebird -remote 'openURL(%s,
new-tab)'" %(nurl[0]))
52 elif key == 270:
53 ekg.printf("generic", "wcisnięto F6")
54 nurl=czyjest()
55 if nurl == 0:
56 ekg.printf("generic", "nic nie moge skasować - nie
mazadnego adresu URL")
57 else:
58 dlug=len(nurl)
59 if dlug == 1:
60 ekg.printf("generic", "kasuje adres %s" %(nurl[0]))

61 os.system('rm /tmp/rmrmg_ekg_url')
62 else:
63 ekg.printf("generic", "jest wiele linków")
64 wielejest(nurl)
65 ekg.printf("generic", "kasuje pierwszy czyli:
%s"%(nurl[0]))
66 elif key == 271:
67 ekg.printf("generic", "wcisnięto F7")
68 nurl=czyjest()
69 if nurl == 0:
70 ekg.printf("generic", "nie ma zadnego adresu URL")
71 else:
72 dlug=len(nurl)
73 if dlug == 1:
74 ekg.printf("generic", "otwieram %s w nowym
oknie"%(nurl[0]))
75 os.system("MozillaFirebird %s" %(nurl[0]))
76 os.system('rm /tmp/rmrmg_ekg_url')
77 else:
78 ekg.printf("generic", "linków mam %d" %(dlug))
79 wielejest(nurl)
80 ekg.printf("generic", "otwieram %s w nowym
oknie"%(nurl[0]))
81 elif key == 272:
82 ekg.printf("generic", "wcisnięto F8")
83 nurl=czyjest()
84 ekg.printf("generic", "F5 - otwiera w nowej zakładce; F7
wnowym oknie, a F6 kasuje, wszystko tyczy się pierwszej po zycji
zlisty")
85 if nurl == 0:
86 ekg.printf("generic", "nie ma zadnego adresu URL")
87 else:
88 dlug=len(nurl)
89 ekg.printf("generic", "linków mam %d oto one:" %(dlug))
90 for po in nurl:
91 ekg.printf("generic", "%s" %(po))
92 return 1

#########
Related :
#########

Gentoo Bugs report : http://bugs.gentoo.org/show_bug.cgi?id=94172
CVE : CAN-2005-1916

#####################
Credits :
#####################

Eric Romang (eromangzataz.net - ZATAZ Audit)
Thxs to Gentoo Security Team. (Taviso, jaervosz, solar, tigger, etc.)