1 | /*-
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2 | * Copyright (c) 2001 Charles Mott <cm@linktel.net>
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3 | * All rights reserved.
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4 | *
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5 | * Redistribution and use in source and binary forms, with or without
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6 | * modification, are permitted provided that the following conditions
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7 | * are met:
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8 | * 1. Redistributions of source code must retain the above copyright
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9 | * notice, this list of conditions and the following disclaimer.
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10 | * 2. Redistributions in binary form must reproduce the above copyright
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11 | * notice, this list of conditions and the following disclaimer in the
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12 | * documentation and/or other materials provided with the distribution.
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13 | *
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14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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15 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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16 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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17 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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18 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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19 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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20 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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21 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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22 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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23 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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24 | * SUCH DAMAGE.
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25 | */
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26 |
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27 | #include <sys/cdefs.h>
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28 | __FBSDID("$FreeBSD: src/sys/netinet/libalias/alias_irc.c,v 1.23.2.2.4.1 2009/04/15 03:14:26 kensmith Exp $");
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29 |
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30 | /* Alias_irc.c intercepts packages contain IRC CTCP commands, and
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31 | changes DCC commands to export a port on the aliasing host instead
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32 | of an aliased host.
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33 |
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34 | For this routine to work, the DCC command must fit entirely into a
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35 | single TCP packet. This will usually happen, but is not
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36 | guaranteed.
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37 |
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38 | The interception is likely to change the length of the packet.
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39 | The handling of this is copied more-or-less verbatim from
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40 | ftp_alias.c
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41 |
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42 | Initial version: Eivind Eklund <perhaps@yes.no> (ee) 97-01-29
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43 |
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44 | Version 2.1: May, 1997 (cjm)
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45 | Very minor changes to conform with
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46 | local/global/function naming conventions
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47 | withing the packet alising module.
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48 | */
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49 |
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50 | /* Includes */
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51 | #ifdef _KERNEL
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52 | #include <sys/param.h>
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53 | #include <sys/ctype.h>
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54 | #include <sys/limits.h>
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55 | #include <sys/systm.h>
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56 | #include <sys/kernel.h>
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57 | #include <sys/module.h>
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58 | #else
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59 | #include <errno.h>
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60 | #include <sys/types.h>
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61 | #include <stdio.h>
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62 | #include <stdlib.h>
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63 | #include <string.h>
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64 | #include <limits.h>
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65 | #endif
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66 |
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67 | #include <netinet/in_systm.h>
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68 | #include <netinet/in.h>
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69 | #include <netinet/ip.h>
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70 | #include <netinet/tcp.h>
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71 |
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72 | #ifdef _KERNEL
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73 | #include <netinet/libalias/alias.h>
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74 | #include <netinet/libalias/alias_local.h>
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75 | #include <netinet/libalias/alias_mod.h>
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76 | #else
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77 | #include "alias_local.h"
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78 | #include "alias_mod.h"
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79 | #endif
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80 |
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81 | #define IRC_CONTROL_PORT_NUMBER_1 6667
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82 | #define IRC_CONTROL_PORT_NUMBER_2 6668
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83 |
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84 | #define PKTSIZE (IP_MAXPACKET + 1)
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85 | char *newpacket;
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86 |
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87 | /* Local defines */
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88 | #define DBprintf(a)
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89 |
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90 | static void
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91 | AliasHandleIrcOut(struct libalias *, struct ip *, struct alias_link *,
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92 | int maxpacketsize);
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93 |
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94 | static int
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95 | fingerprint(struct libalias *la, struct ip *pip, struct alias_data *ah)
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96 | {
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97 |
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98 | if (ah->dport == NULL || ah->lnk == NULL ||
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99 | ah->maxpktsize == 0)
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100 | return (-1);
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101 | if (ntohs(*ah->dport) == IRC_CONTROL_PORT_NUMBER_1
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102 | || ntohs(*ah->dport) == IRC_CONTROL_PORT_NUMBER_2)
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103 | return (0);
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104 | return (-1);
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105 | }
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106 |
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107 | static int
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108 | protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
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109 | {
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110 |
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111 | newpacket = malloc(PKTSIZE);
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112 | if (newpacket) {
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113 | AliasHandleIrcOut(la, pip, ah->lnk, ah->maxpktsize);
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114 | free(newpacket);
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115 | }
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116 | return (0);
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117 | }
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118 |
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119 | struct proto_handler handlers[] = {
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120 | {
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121 | .pri = 90,
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122 | .dir = OUT,
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123 | .proto = TCP,
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124 | .fingerprint = &fingerprint,
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125 | .protohandler = &protohandler
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126 | },
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127 | { EOH }
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128 | };
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129 |
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130 | static int
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131 | mod_handler(module_t mod, int type, void *data)
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132 | {
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133 | int error;
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134 |
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135 | switch (type) {
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136 | case MOD_LOAD:
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137 | error = 0;
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138 | LibAliasAttachHandlers(handlers);
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139 | break;
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140 | case MOD_UNLOAD:
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141 | error = 0;
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142 | LibAliasDetachHandlers(handlers);
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143 | break;
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144 | default:
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145 | error = EINVAL;
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146 | }
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147 | return (error);
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148 | }
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149 |
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150 | #ifdef _KERNEL
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151 | static
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152 | #endif
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153 | moduledata_t alias_mod = {
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154 | "alias_irc", mod_handler, NULL
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155 | };
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156 |
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157 | /* Kernel module definition. */
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158 | #ifdef _KERNEL
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159 | DECLARE_MODULE(alias_irc, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
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160 | MODULE_VERSION(alias_irc, 1);
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161 | MODULE_DEPEND(alias_irc, libalias, 1, 1, 1);
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162 | #endif
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163 |
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164 | static void
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165 | AliasHandleIrcOut(struct libalias *la,
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166 | struct ip *pip, /* IP packet to examine */
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167 | struct alias_link *lnk, /* Which link are we on? */
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168 | int maxsize /* Maximum size of IP packet including
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169 | * headers */
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170 | )
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171 | {
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172 | int hlen, tlen, dlen;
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173 | struct in_addr true_addr;
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174 | u_short true_port;
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175 | char *sptr;
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176 | struct tcphdr *tc;
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177 | int i; /* Iterator through the source */
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178 |
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179 | /* Calculate data length of TCP packet */
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180 | tc = (struct tcphdr *)ip_next(pip);
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181 | hlen = (pip->ip_hl + tc->th_off) << 2;
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182 | tlen = ntohs(pip->ip_len);
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183 | dlen = tlen - hlen;
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184 |
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185 | /*
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186 | * Return if data length is too short - assume an entire PRIVMSG in
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187 | * each packet.
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188 | */
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189 | if (dlen < (int)sizeof(":A!a@n.n PRIVMSG A :aDCC 1 1a") - 1)
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190 | return;
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191 |
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192 | /* Place string pointer at beginning of data */
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193 | sptr = (char *)pip;
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194 | sptr += hlen;
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195 | maxsize -= hlen; /* We're interested in maximum size of
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196 | * data, not packet */
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197 |
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198 | /* Search for a CTCP command [Note 1] */
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199 | for (i = 0; i < dlen; i++) {
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200 | if (sptr[i] == '\001')
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201 | goto lFOUND_CTCP;
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202 | }
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203 | return; /* No CTCP commands in */
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204 | /* Handle CTCP commands - the buffer may have to be copied */
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205 | lFOUND_CTCP:
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206 | {
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207 | unsigned int copyat = i;
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208 | unsigned int iCopy = 0; /* How much data have we written to
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209 | * copy-back string? */
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210 | unsigned long org_addr; /* Original IP address */
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211 | unsigned short org_port; /* Original source port
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212 | * address */
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213 |
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214 | lCTCP_START:
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215 | if (i >= dlen || iCopy >= PKTSIZE)
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216 | goto lPACKET_DONE;
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217 | newpacket[iCopy++] = sptr[i++]; /* Copy the CTCP start
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218 | * character */
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219 | /* Start of a CTCP */
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220 | if (i + 4 >= dlen) /* Too short for DCC */
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221 | goto lBAD_CTCP;
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222 | if (sptr[i + 0] != 'D')
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223 | goto lBAD_CTCP;
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224 | if (sptr[i + 1] != 'C')
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225 | goto lBAD_CTCP;
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226 | if (sptr[i + 2] != 'C')
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227 | goto lBAD_CTCP;
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228 | if (sptr[i + 3] != ' ')
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229 | goto lBAD_CTCP;
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230 | /* We have a DCC command - handle it! */
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231 | i += 4; /* Skip "DCC " */
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232 | if (iCopy + 4 > PKTSIZE)
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233 | goto lPACKET_DONE;
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234 | newpacket[iCopy++] = 'D';
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235 | newpacket[iCopy++] = 'C';
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236 | newpacket[iCopy++] = 'C';
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237 | newpacket[iCopy++] = ' ';
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238 |
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239 | DBprintf(("Found DCC\n"));
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240 | /*
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241 | * Skip any extra spaces (should not occur according to
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242 | * protocol, but DCC breaks CTCP protocol anyway
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243 | */
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244 | while (sptr[i] == ' ') {
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245 | if (++i >= dlen) {
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246 | DBprintf(("DCC packet terminated in just spaces\n"));
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247 | goto lPACKET_DONE;
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248 | }
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249 | }
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250 |
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251 | DBprintf(("Transferring command...\n"));
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252 | while (sptr[i] != ' ') {
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253 | newpacket[iCopy++] = sptr[i];
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254 | if (++i >= dlen || iCopy >= PKTSIZE) {
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255 | DBprintf(("DCC packet terminated during command\n"));
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256 | goto lPACKET_DONE;
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257 | }
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258 | }
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259 | /* Copy _one_ space */
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260 | if (i + 1 < dlen && iCopy < PKTSIZE)
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261 | newpacket[iCopy++] = sptr[i++];
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262 |
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263 | DBprintf(("Done command - removing spaces\n"));
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264 | /*
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265 | * Skip any extra spaces (should not occur according to
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266 | * protocol, but DCC breaks CTCP protocol anyway
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267 | */
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268 | while (sptr[i] == ' ') {
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269 | if (++i >= dlen) {
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270 | DBprintf(("DCC packet terminated in just spaces (post-command)\n"));
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271 | goto lPACKET_DONE;
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272 | }
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273 | }
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274 |
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275 | DBprintf(("Transferring filename...\n"));
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276 | while (sptr[i] != ' ') {
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277 | newpacket[iCopy++] = sptr[i];
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278 | if (++i >= dlen || iCopy >= PKTSIZE) {
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279 | DBprintf(("DCC packet terminated during filename\n"));
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280 | goto lPACKET_DONE;
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281 | }
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282 | }
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283 | /* Copy _one_ space */
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284 | if (i + 1 < dlen && iCopy < PKTSIZE)
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285 | newpacket[iCopy++] = sptr[i++];
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286 |
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287 | DBprintf(("Done filename - removing spaces\n"));
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288 | /*
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289 | * Skip any extra spaces (should not occur according to
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290 | * protocol, but DCC breaks CTCP protocol anyway
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291 | */
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292 | while (sptr[i] == ' ') {
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293 | if (++i >= dlen) {
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294 | DBprintf(("DCC packet terminated in just spaces (post-filename)\n"));
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295 | goto lPACKET_DONE;
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296 | }
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297 | }
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298 |
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299 | DBprintf(("Fetching IP address\n"));
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300 | /* Fetch IP address */
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301 | org_addr = 0;
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302 | while (i < dlen && isdigit(sptr[i])) {
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303 | if (org_addr > ULONG_MAX / 10UL) { /* Terminate on overflow */
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304 | DBprintf(("DCC Address overflow (org_addr == 0x%08lx, next char %c\n", org_addr, sptr[i]));
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305 | goto lBAD_CTCP;
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306 | }
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307 | org_addr *= 10;
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308 | org_addr += sptr[i++] - '0';
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309 | }
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310 | DBprintf(("Skipping space\n"));
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311 | if (i + 1 >= dlen || sptr[i] != ' ') {
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312 | DBprintf(("Overflow (%d >= %d) or bad character (%02x) terminating IP address\n", i + 1, dlen, sptr[i]));
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313 | goto lBAD_CTCP;
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314 | }
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315 | /*
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316 | * Skip any extra spaces (should not occur according to
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317 | * protocol, but DCC breaks CTCP protocol anyway, so we
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318 | * might as well play it safe
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319 | */
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320 | while (sptr[i] == ' ') {
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321 | if (++i >= dlen) {
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322 | DBprintf(("Packet failure - space overflow.\n"));
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323 | goto lPACKET_DONE;
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324 | }
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325 | }
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326 | DBprintf(("Fetching port number\n"));
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327 | /* Fetch source port */
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328 | org_port = 0;
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329 | while (i < dlen && isdigit(sptr[i])) {
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330 | if (org_port > 6554) { /* Terminate on overflow
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331 | * (65536/10 rounded up */
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332 | DBprintf(("DCC: port number overflow\n"));
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333 | goto lBAD_CTCP;
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334 | }
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335 | org_port *= 10;
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336 | org_port += sptr[i++] - '0';
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337 | }
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338 | /* Skip illegal addresses (or early termination) */
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339 | if (i >= dlen || (sptr[i] != '\001' && sptr[i] != ' ')) {
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340 | DBprintf(("Bad port termination\n"));
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341 | goto lBAD_CTCP;
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342 | }
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343 | DBprintf(("Got IP %lu and port %u\n", org_addr, (unsigned)org_port));
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344 |
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345 | /* We've got the address and port - now alias it */
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346 | {
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347 | struct alias_link *dcc_lnk;
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348 | struct in_addr destaddr;
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349 |
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350 |
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351 | true_port = htons(org_port);
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352 | true_addr.s_addr = htonl(org_addr);
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353 | destaddr.s_addr = 0;
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354 |
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355 | /* Sanity/Security checking */
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356 | if (!org_addr || !org_port ||
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357 | pip->ip_src.s_addr != true_addr.s_addr ||
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358 | org_port < IPPORT_RESERVED)
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359 | goto lBAD_CTCP;
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360 |
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361 | /*
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362 | * Steal the FTP_DATA_PORT - it doesn't really
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363 | * matter, and this would probably allow it through
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364 | * at least _some_ firewalls.
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365 | */
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366 | dcc_lnk = FindUdpTcpOut(la, true_addr, destaddr,
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367 | true_port, 0,
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368 | IPPROTO_TCP, 1);
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369 | DBprintf(("Got a DCC link\n"));
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370 | if (dcc_lnk) {
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371 | struct in_addr alias_address; /* Address from aliasing */
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372 | u_short alias_port; /* Port given by
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373 | * aliasing */
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374 | int n;
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375 |
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376 | #ifndef NO_FW_PUNCH
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377 | /* Generate firewall hole as appropriate */
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378 | PunchFWHole(dcc_lnk);
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379 | #endif
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380 |
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381 | alias_address = GetAliasAddress(lnk);
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382 | n = snprintf(&newpacket[iCopy],
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383 | PKTSIZE - iCopy,
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384 | "%lu ", (u_long) htonl(alias_address.s_addr));
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385 | if (n < 0) {
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386 | DBprintf(("DCC packet construct failure.\n"));
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387 | goto lBAD_CTCP;
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388 | }
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389 | if ((iCopy += n) >= PKTSIZE) { /* Truncated/fit exactly
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390 | * - bad news */
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391 | DBprintf(("DCC constructed packet overflow.\n"));
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392 | goto lBAD_CTCP;
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393 | }
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394 | alias_port = GetAliasPort(dcc_lnk);
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395 | n = snprintf(&newpacket[iCopy],
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396 | PKTSIZE - iCopy,
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397 | "%u", htons(alias_port));
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398 | if (n < 0) {
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399 | DBprintf(("DCC packet construct failure.\n"));
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400 | goto lBAD_CTCP;
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401 | }
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402 | iCopy += n;
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403 | /*
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404 | * Done - truncated cases will be taken
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405 | * care of by lBAD_CTCP
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406 | */
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407 | DBprintf(("Aliased IP %lu and port %u\n", alias_address.s_addr, (unsigned)alias_port));
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408 | }
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409 | }
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410 | /*
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411 | * An uninteresting CTCP - state entered right after '\001'
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412 | * has been pushed. Also used to copy the rest of a DCC,
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413 | * after IP address and port has been handled
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414 | */
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415 | lBAD_CTCP:
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416 | for (; i < dlen && iCopy < PKTSIZE; i++, iCopy++) {
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417 | newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
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418 | if (sptr[i] == '\001') {
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419 | goto lNORMAL_TEXT;
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420 | }
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421 | }
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422 | goto lPACKET_DONE;
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423 | /* Normal text */
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424 | lNORMAL_TEXT:
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425 | for (; i < dlen && iCopy < PKTSIZE; i++, iCopy++) {
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426 | newpacket[iCopy] = sptr[i]; /* Copy CTCP unchanged */
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427 | if (sptr[i] == '\001') {
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428 | goto lCTCP_START;
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429 | }
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430 | }
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431 | /* Handle the end of a packet */
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432 | lPACKET_DONE:
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433 | iCopy = iCopy > maxsize - copyat ? maxsize - copyat : iCopy;
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434 | memcpy(sptr + copyat, newpacket, iCopy);
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435 |
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436 | /* Save information regarding modified seq and ack numbers */
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437 | {
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438 | int delta;
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439 |
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440 | SetAckModified(lnk);
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441 | delta = GetDeltaSeqOut(pip, lnk);
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442 | AddSeq(pip, lnk, delta + copyat + iCopy - dlen);
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443 | }
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444 |
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445 | /* Revise IP header */
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446 | {
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447 | u_short new_len;
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448 |
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449 | new_len = htons(hlen + iCopy + copyat);
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450 | DifferentialChecksum(&pip->ip_sum,
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451 | &new_len,
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452 | &pip->ip_len,
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453 | 1);
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454 | pip->ip_len = new_len;
|
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455 | }
|
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456 |
|
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457 | /* Compute TCP checksum for revised packet */
|
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458 | tc->th_sum = 0;
|
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459 | #ifdef _KERNEL
|
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460 | tc->th_x2 = 1;
|
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461 | #else
|
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462 | tc->th_sum = TcpChecksum(pip);
|
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463 | #endif
|
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464 | return;
|
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465 | }
|
---|
466 | }
|
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467 |
|
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468 | /* Notes:
|
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469 | [Note 1]
|
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470 | The initial search will most often fail; it could be replaced with a 32-bit specific search.
|
---|
471 | Such a search would be done for 32-bit unsigned value V:
|
---|
472 | V ^= 0x01010101; (Search is for null bytes)
|
---|
473 | if( ((V-0x01010101)^V) & 0x80808080 ) {
|
---|
474 | (found a null bytes which was a 01 byte)
|
---|
475 | }
|
---|
476 | To assert that the processor is 32-bits, do
|
---|
477 | extern int ircdccar[32]; (32 bits)
|
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478 | extern int ircdccar[CHAR_BIT*sizeof(unsigned int)];
|
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479 | which will generate a type-error on all but 32-bit machines.
|
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480 |
|
---|
481 | [Note 2] This routine really ought to be replaced with one that
|
---|
482 | creates a transparent proxy on the aliasing host, to allow arbitary
|
---|
483 | changes in the TCP stream. This should not be too difficult given
|
---|
484 | this base; I (ee) will try to do this some time later.
|
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485 | */
|
---|