src/peer/spoof.c

   1 /*****************************************************************************
   2  * Copyright 2005 Daniel Ferullo                                             *
   3  *                                                                           *
   4  * Licensed under the Apache License, Version 2.0 (the "License");           *
   5  * you may not use this file except in compliance with the License.          *
   6  * You may obtain a copy of the License at                                   *
   7  *                                                                           *
   8  *    http://www.apache.org/licenses/LICENSE-2.0                             *
   9  *                                                                           *
  10  * Unless required by applicable law or agreed to in writing, software       *
  11  * distributed under the License is distributed on an "AS IS" BASIS,         *
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  *
  13  * See the License for the specific language governing permissions and       *
  14  * limitations under the License.                                            *
  15  *                                                                           *
  16  *****************************************************************************/
  17
  18 /**
  19  * @file spoof.c
  20  * @author Daniel Ferullo (ferullo@cmu.edu)
  21  *
  22  * @brief functions to spoof/forge network packets
  23  */
  24
  25 #include "spoof.h"
  26 #include "spoof_private.h"
  27 #include <libnet.h>
  28 #include "debug.h"
  29 #include "peerdef.h"
  30
  31 errorcode spoof(tcp_packet_info_t *tcp_hdr, char *device, void *payload,
  32                                         unsigned long payload_len, short ttl){
  33
  34         /* declare local variables */
  35         int c;
  36         libnet_t *lib;
  37         libnet_ptag_t t;
  38         char errbuf[LIBNET_ERRBUF_SIZE];
  39         unsigned char tcp_flags;
  40
  41         /* error check arguments */
  42         CHECK_NOT_NULL(tcp_hdr,ERROR_NULL_ARG_1);
  43         CHECK_NOT_NULL(device,ERROR_NULL_ARG_2);
  44         if ( (payload==NULL) && (payload_len!=0))
  45                 return ERROR_ARG_3;
  46
  47         /* do function */
  48
  49         /* set the tcp_flags */
  50         tcp_flags = 0;
  51         tcp_flags |= ( (tcp_hdr->syn_flag==FLAG_SET) ? TH_SYN : 0);
  52         tcp_flags |= ( (tcp_hdr->ack_flag==FLAG_SET) ? TH_ACK : 0);
  53
  54         /* Initialize the library.  Root priviledges are required. */
  55         lib = libnet_init(
  56                 LIBNET_RAW4,                 /* injection type */
  57                 device,                      /* network interface */
  58                 errbuf);                     /* errbuf */
  59
  60         if (lib == NULL) {
  61                 DEBUG(DBG_SPOOF,"SPOOF:libnet_init() failed\n");
  62                 return ERROR_1;
  63         }
  64
  65         /* make sure to put ports, seq_num, ack_num and window in host byte
  66          * order because libnet doesn't want them in network byte order. */
  67         t = libnet_build_tcp(
  68                 PORT_2HBO(tcp_hdr->s_port),     /* source port */
  69                 PORT_2HBO(tcp_hdr->d_port),     /* destination port */
  70                 SEQ_NUM_2HBO(tcp_hdr->seq_num), /* sequence number */
  71                 SEQ_NUM_2HBO(tcp_hdr->ack_num), /* acknowledgement number */
  72                 tcp_flags,                      /* control flags */
  73                 WINDOW_2HBO(tcp_hdr->window),   /* window size */
  74                 0,                              /* checksum */
  75                 0,                              /* urgent pointer */
  76                 LIBNET_TCP_H + payload_len,     /* TCP packet size */
  77                 payload,                        /* payload */
  78                 payload_len,                    /* payload size */
  79                 lib,                            /* libnet handle */
  80                 0                               /* libnet id */
  81             );
  82
  83         if (t == -1) {
  84                 DEBUG(DBG_SPOOF,"SPOOF:can't build TCP header\n");
  85                 libnet_destroy(lib);
  86                 return ERROR_2;
  87         }
  88
  89         t = libnet_build_ipv4(
  90                 LIBNET_IPV4_H+LIBNET_TCP_H+payload_len,  /* length */
  91                 0,                                       /* TOS */
  92                 242,                                     /* IP ID */
  93                 0,                                       /* IP Frag */
  94                 ttl,                                      /* TTL */
  95                 IPPROTO_TCP,                             /* protocol */
  96                 0,                                       /* checksum */
  97                 tcp_hdr->s_addr,                         /* source IP */
  98                 tcp_hdr->d_addr,                         /* destination IP */
  99                 NULL,                                    /* payload */
 100                 0,                                       /* payload size */
 101                 lib,                                     /* libnet handle */
 102                 0                                        /* libnet id */
 103             );
 104
 105         if (t == -1) {
 106                 DEBUG(DBG_SPOOF,"SPOOF:can't build IP header\n");
 107                 libnet_destroy(lib);
 108                 return ERROR_3;
 109         }
 110
 111         /* Write it to the wire. */
 112         c = libnet_write(lib);
 113
 114         if (c == -1) {
 115                 DEBUG(DBG_SPOOF,"SPOOF:write error\n");
 116                 libnet_destroy(lib);
 117                 return ERROR_4;
 118         }
 119
 120         libnet_destroy(lib);
 121         return SUCCESS;
 122 }
 123