1 | /*
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2 | * options.c -- DHCP server option packet tools
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3 | * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
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4 | */
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5 |
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6 | #include <stdlib.h>
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7 | #include <string.h>
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8 |
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9 | #include "common.h"
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10 | #include "dhcpd.h"
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11 | #include "options.h"
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12 | #include "files.h"
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13 |
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14 |
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15 | /* supported options are easily added here */
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16 | struct dhcp_option dhcp_options[] = {
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17 | /* name[10] flags code */
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18 | {"subnet", OPTION_IP | OPTION_REQ, 0x01},
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19 | {"timezone", OPTION_S32, 0x02},
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20 | {"router", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x03},
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21 | {"timesvr", OPTION_IP | OPTION_LIST, 0x04},
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22 | {"namesvr", OPTION_IP | OPTION_LIST, 0x05},
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23 | {"dns", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x06},
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24 | {"logsvr", OPTION_IP | OPTION_LIST, 0x07},
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25 | {"cookiesvr", OPTION_IP | OPTION_LIST, 0x08},
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26 | {"lprsvr", OPTION_IP | OPTION_LIST, 0x09},
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27 | {"hostname", OPTION_STRING | OPTION_REQ, 0x0c},
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28 | {"bootsize", OPTION_U16, 0x0d},
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29 | {"domain", OPTION_STRING | OPTION_REQ, 0x0f},
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30 | {"swapsvr", OPTION_IP, 0x10},
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31 | {"rootpath", OPTION_STRING, 0x11},
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32 | {"ipttl", OPTION_U8, 0x17},
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33 | {"mtu", OPTION_U16, 0x1a},
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34 | {"broadcast", OPTION_IP | OPTION_REQ, 0x1c},
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35 | {"nisdomain", OPTION_STRING | OPTION_REQ, 0x28},
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36 | {"nissrv", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x29},
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37 | {"ntpsrv", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x2a},
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38 | {"wins", OPTION_IP | OPTION_LIST, 0x2c},
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39 | {"requestip", OPTION_IP, 0x32},
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40 | {"lease", OPTION_U32, 0x33},
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41 | {"dhcptype", OPTION_U8, 0x35},
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42 | {"serverid", OPTION_IP, 0x36},
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43 | {"message", OPTION_STRING, 0x38},
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44 | {"tftp", OPTION_STRING, 0x42},
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45 | {"bootfile", OPTION_STRING, 0x43},
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46 | {"", 0x00, 0x00}
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47 | };
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48 |
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49 | /* Lengths of the different option types */
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50 | int option_lengths[] = {
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51 | [OPTION_IP] = 4,
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52 | [OPTION_IP_PAIR] = 8,
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53 | [OPTION_BOOLEAN] = 1,
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54 | [OPTION_STRING] = 1,
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55 | [OPTION_U8] = 1,
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56 | [OPTION_U16] = 2,
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57 | [OPTION_S16] = 2,
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58 | [OPTION_U32] = 4,
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59 | [OPTION_S32] = 4
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60 | };
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61 |
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62 |
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63 | /* get an option with bounds checking (warning, not aligned). */
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64 | uint8_t *get_option(struct dhcpMessage *packet, int code)
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65 | {
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66 | int i, length;
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67 | uint8_t *optionptr;
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68 | int over = 0, done = 0, curr = OPTION_FIELD;
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69 |
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70 | optionptr = packet->options;
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71 | i = 0;
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72 | length = 308;
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73 | while (!done) {
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74 | if (i >= length) {
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75 | LOG(LOG_WARNING, "bogus packet, option fields too long.");
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76 | return NULL;
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77 | }
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78 | if (optionptr[i + OPT_CODE] == code) {
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79 | if (i + 1 + optionptr[i + OPT_LEN] >= length) {
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80 | LOG(LOG_WARNING, "bogus packet, option fields too long.");
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81 | return NULL;
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82 | }
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83 | return optionptr + i + 2;
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84 | }
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85 | switch (optionptr[i + OPT_CODE]) {
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86 | case DHCP_PADDING:
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87 | i++;
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88 | break;
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89 | case DHCP_OPTION_OVER:
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90 | if (i + 1 + optionptr[i + OPT_LEN] >= length) {
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91 | LOG(LOG_WARNING, "bogus packet, option fields too long.");
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92 | return NULL;
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93 | }
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94 | over = optionptr[i + 3];
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95 | i += optionptr[OPT_LEN] + 2;
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96 | break;
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97 | case DHCP_END:
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98 | if (curr == OPTION_FIELD && over & FILE_FIELD) {
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99 | optionptr = packet->file;
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100 | i = 0;
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101 | length = 128;
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102 | curr = FILE_FIELD;
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103 | } else if (curr == FILE_FIELD && over & SNAME_FIELD) {
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104 | optionptr = packet->sname;
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105 | i = 0;
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106 | length = 64;
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107 | curr = SNAME_FIELD;
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108 | } else done = 1;
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109 | break;
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110 | default:
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111 | i += optionptr[OPT_LEN + i] + 2;
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112 | }
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113 | }
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114 | return NULL;
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115 | }
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116 |
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117 |
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118 | /* return the position of the 'end' option (no bounds checking) */
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119 | int end_option(uint8_t *optionptr)
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120 | {
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121 | int i = 0;
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122 |
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123 | while (optionptr[i] != DHCP_END) {
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124 | if (optionptr[i] == DHCP_PADDING) i++;
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125 | else i += optionptr[i + OPT_LEN] + 2;
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126 | }
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127 | return i;
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128 | }
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129 |
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130 |
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131 | /* add an option string to the options (an option string contains an option code,
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132 | * length, then data) */
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133 | int add_option_string(uint8_t *optionptr, uint8_t *string)
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134 | {
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135 | int end = end_option(optionptr);
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136 |
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137 | /* end position + string length + option code/length + end option */
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138 | if (end + string[OPT_LEN] + 2 + 1 >= 308) {
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139 | LOG(LOG_ERR, "Option 0x%02x did not fit into the packet!", string[OPT_CODE]);
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140 | return 0;
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141 | }
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142 | DEBUG(LOG_INFO, "adding option 0x%02x", string[OPT_CODE]);
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143 | memcpy(optionptr + end, string, string[OPT_LEN] + 2);
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144 | optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
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145 | return string[OPT_LEN] + 2;
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146 | }
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147 |
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148 |
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149 | /* add a one to four byte option to a packet */
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150 | int add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
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151 | {
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152 | struct dhcp_option *dh;
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153 |
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154 | for (dh=dhcp_options; dh->code; dh++) {
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155 | if (dh->code == code) {
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156 | uint8_t option[6], len;
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157 |
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158 | option[OPT_CODE] = code;
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159 | len = option_lengths[dh->flags & TYPE_MASK];
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160 | option[OPT_LEN] = len;
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161 | if (BB_BIG_ENDIAN) data <<= 8 * (4 - len);
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162 | /* This memcpy is for broken processors which can't
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163 | * handle a simple unaligned 32-bit assignment */
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164 | memcpy(&option[OPT_DATA], &data, 4);
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165 | return add_option_string(optionptr, option);
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166 | }
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167 | }
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168 |
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169 | DEBUG(LOG_ERR, "Could not add option 0x%02x", code);
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170 | return 0;
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171 | }
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