1 | /**
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2 | * @file
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3 | * Abstract Syntax Notation One (ISO 8824, 8825) decoding
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4 | *
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5 | * @todo not optimised (yet), favor correctness over speed, favor speed over size
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6 | */
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7 |
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8 | /*
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9 | * Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.
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10 | * All rights reserved.
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11 | *
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12 | * Redistribution and use in source and binary forms, with or without modification,
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13 | * are permitted provided that the following conditions are met:
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14 | *
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15 | * 1. Redistributions of source code must retain the above copyright notice,
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16 | * this list of conditions and the following disclaimer.
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17 | * 2. Redistributions in binary form must reproduce the above copyright notice,
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18 | * this list of conditions and the following disclaimer in the documentation
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19 | * and/or other materials provided with the distribution.
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20 | * 3. The name of the author may not be used to endorse or promote products
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21 | * derived from this software without specific prior written permission.
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22 | *
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23 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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24 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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25 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
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26 | * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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27 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
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28 | * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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29 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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30 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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31 | * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
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32 | * OF SUCH DAMAGE.
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33 | *
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34 | * Author: Christiaan Simons <christiaan.simons@axon.tv>
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35 | */
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36 |
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37 | #include "lwip/opt.h"
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38 |
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39 | #if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
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40 |
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41 | #include "lwip/snmp_asn1.h"
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42 |
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43 | /**
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44 | * Retrieves type field from incoming pbuf chain.
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45 | *
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46 | * @param p points to a pbuf holding an ASN1 coded type field
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47 | * @param ofs points to the offset within the pbuf chain of the ASN1 coded type field
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48 | * @param type return ASN1 type
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49 | * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
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50 | */
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51 | err_t
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52 | snmp_asn1_dec_type(struct pbuf *p, u16_t ofs, u8_t *type)
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53 | {
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54 | u16_t plen, base;
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55 | u8_t *msg_ptr;
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56 |
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57 | plen = 0;
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58 | while (p != NULL)
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59 | {
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60 | base = plen;
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61 | plen += p->len;
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62 | if (ofs < plen)
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63 | {
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64 | msg_ptr = (u8_t*)p->payload;
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65 | msg_ptr += ofs - base;
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66 | *type = *msg_ptr;
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67 | return ERR_OK;
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68 | }
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69 | p = p->next;
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70 | }
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71 | /* p == NULL, ofs >= plen */
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72 | return ERR_ARG;
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73 | }
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74 |
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75 | /**
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76 | * Decodes length field from incoming pbuf chain into host length.
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77 | *
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78 | * @param p points to a pbuf holding an ASN1 coded length
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79 | * @param ofs points to the offset within the pbuf chain of the ASN1 coded length
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80 | * @param octets_used returns number of octets used by the length code
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81 | * @param length return host order length, upto 64k
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82 | * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
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83 | */
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84 | err_t
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85 | snmp_asn1_dec_length(struct pbuf *p, u16_t ofs, u8_t *octets_used, u16_t *length)
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86 | {
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87 | u16_t plen, base;
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88 | u8_t *msg_ptr;
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89 |
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90 | plen = 0;
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91 | while (p != NULL)
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92 | {
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93 | base = plen;
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94 | plen += p->len;
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95 | if (ofs < plen)
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96 | {
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97 | msg_ptr = (u8_t*)p->payload;
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98 | msg_ptr += ofs - base;
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99 |
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100 | if (*msg_ptr < 0x80)
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101 | {
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102 | /* primitive definite length format */
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103 | *octets_used = 1;
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104 | *length = *msg_ptr;
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105 | return ERR_OK;
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106 | }
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107 | else if (*msg_ptr == 0x80)
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108 | {
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109 | /* constructed indefinite length format, termination with two zero octets */
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110 | u8_t zeros;
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111 | u8_t i;
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112 |
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113 | *length = 0;
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114 | zeros = 0;
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115 | while (zeros != 2)
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116 | {
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117 | i = 2;
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118 | while (i > 0)
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119 | {
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120 | i--;
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121 | (*length) += 1;
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122 | ofs += 1;
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123 | if (ofs >= plen)
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124 | {
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125 | /* next octet in next pbuf */
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126 | p = p->next;
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127 | if (p == NULL) { return ERR_ARG; }
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128 | msg_ptr = (u8_t*)p->payload;
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129 | plen += p->len;
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130 | }
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131 | else
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132 | {
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133 | /* next octet in same pbuf */
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134 | msg_ptr++;
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135 | }
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136 | if (*msg_ptr == 0)
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137 | {
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138 | zeros++;
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139 | if (zeros == 2)
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140 | {
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141 | /* stop while (i > 0) */
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142 | i = 0;
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143 | }
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144 | }
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145 | else
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146 | {
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147 | zeros = 0;
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148 | }
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149 | }
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150 | }
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151 | *octets_used = 1;
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152 | return ERR_OK;
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153 | }
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154 | else if (*msg_ptr == 0x81)
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155 | {
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156 | /* constructed definite length format, one octet */
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157 | ofs += 1;
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158 | if (ofs >= plen)
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159 | {
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160 | /* next octet in next pbuf */
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161 | p = p->next;
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162 | if (p == NULL) { return ERR_ARG; }
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163 | msg_ptr = (u8_t*)p->payload;
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164 | }
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165 | else
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166 | {
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167 | /* next octet in same pbuf */
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168 | msg_ptr++;
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169 | }
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170 | *length = *msg_ptr;
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171 | *octets_used = 2;
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172 | return ERR_OK;
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173 | }
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174 | else if (*msg_ptr == 0x82)
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175 | {
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176 | u8_t i;
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177 |
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178 | /* constructed definite length format, two octets */
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179 | i = 2;
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180 | while (i > 0)
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181 | {
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182 | i--;
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183 | ofs += 1;
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184 | if (ofs >= plen)
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185 | {
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186 | /* next octet in next pbuf */
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187 | p = p->next;
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188 | if (p == NULL) { return ERR_ARG; }
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189 | msg_ptr = (u8_t*)p->payload;
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190 | plen += p->len;
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191 | }
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192 | else
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193 | {
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194 | /* next octet in same pbuf */
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195 | msg_ptr++;
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196 | }
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197 | if (i == 0)
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198 | {
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199 | /* least significant length octet */
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200 | *length |= *msg_ptr;
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201 | }
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202 | else
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203 | {
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204 | /* most significant length octet */
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205 | *length = (*msg_ptr) << 8;
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206 | }
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207 | }
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208 | *octets_used = 3;
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209 | return ERR_OK;
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210 | }
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211 | else
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212 | {
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213 | /* constructed definite length format 3..127 octets, this is too big (>64k) */
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214 | /** @todo: do we need to accept inefficient codings with many leading zero's? */
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215 | *octets_used = 1 + ((*msg_ptr) & 0x7f);
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216 | return ERR_ARG;
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217 | }
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218 | }
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219 | p = p->next;
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220 | }
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221 |
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222 | /* p == NULL, ofs >= plen */
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223 | return ERR_ARG;
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224 | }
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225 |
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226 | /**
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227 | * Decodes positive integer (counter, gauge, timeticks) into u32_t.
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228 | *
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229 | * @param p points to a pbuf holding an ASN1 coded integer
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230 | * @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
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231 | * @param len length of the coded integer field
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232 | * @param value return host order integer
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233 | * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
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234 | *
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235 | * @note ASN coded integers are _always_ signed. E.g. +0xFFFF is coded
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236 | * as 0x00,0xFF,0xFF. Note the leading sign octet. A positive value
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237 | * of 0xFFFFFFFF is preceded with 0x00 and the length is 5 octets!!
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238 | */
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239 | err_t
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240 | snmp_asn1_dec_u32t(struct pbuf *p, u16_t ofs, u16_t len, u32_t *value)
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241 | {
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242 | u16_t plen, base;
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243 | u8_t *msg_ptr;
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244 |
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245 | plen = 0;
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246 | while (p != NULL)
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247 | {
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248 | base = plen;
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249 | plen += p->len;
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250 | if (ofs < plen)
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251 | {
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252 | msg_ptr = (u8_t*)p->payload;
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253 | msg_ptr += ofs - base;
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254 | if ((len > 0) && (len < 6))
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255 | {
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256 | /* start from zero */
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257 | *value = 0;
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258 | if (*msg_ptr & 0x80)
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259 | {
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260 | /* negative, expecting zero sign bit! */
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261 | return ERR_ARG;
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262 | }
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263 | else
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264 | {
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265 | /* positive */
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266 | if ((len > 1) && (*msg_ptr == 0))
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267 | {
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268 | /* skip leading "sign byte" octet 0x00 */
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269 | len--;
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270 | ofs += 1;
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271 | if (ofs >= plen)
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272 | {
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273 | /* next octet in next pbuf */
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274 | p = p->next;
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275 | if (p == NULL) { return ERR_ARG; }
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276 | msg_ptr = (u8_t*)p->payload;
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277 | plen += p->len;
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278 | }
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279 | else
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280 | {
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281 | /* next octet in same pbuf */
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282 | msg_ptr++;
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283 | }
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284 | }
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285 | }
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286 | /* OR octets with value */
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287 | while (len > 1)
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288 | {
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289 | len--;
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290 | *value |= *msg_ptr;
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291 | *value <<= 8;
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292 | ofs += 1;
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293 | if (ofs >= plen)
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294 | {
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295 | /* next octet in next pbuf */
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296 | p = p->next;
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297 | if (p == NULL) { return ERR_ARG; }
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298 | msg_ptr = (u8_t*)p->payload;
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299 | plen += p->len;
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300 | }
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301 | else
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302 | {
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303 | /* next octet in same pbuf */
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304 | msg_ptr++;
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305 | }
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306 | }
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307 | *value |= *msg_ptr;
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308 | return ERR_OK;
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309 | }
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310 | else
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311 | {
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312 | return ERR_ARG;
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313 | }
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314 | }
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315 | p = p->next;
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316 | }
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317 | /* p == NULL, ofs >= plen */
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318 | return ERR_ARG;
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319 | }
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320 |
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321 | /**
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322 | * Decodes integer into s32_t.
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323 | *
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324 | * @param p points to a pbuf holding an ASN1 coded integer
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325 | * @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
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326 | * @param len length of the coded integer field
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327 | * @param value return host order integer
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328 | * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
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329 | *
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330 | * @note ASN coded integers are _always_ signed!
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331 | */
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332 | err_t
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333 | snmp_asn1_dec_s32t(struct pbuf *p, u16_t ofs, u16_t len, s32_t *value)
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334 | {
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335 | u16_t plen, base;
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336 | u8_t *msg_ptr;
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337 | #if BYTE_ORDER == LITTLE_ENDIAN
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338 | u8_t *lsb_ptr = (u8_t*)value;
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339 | #endif
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340 | #if BYTE_ORDER == BIG_ENDIAN
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341 | u8_t *lsb_ptr = (u8_t*)value + sizeof(s32_t) - 1;
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342 | #endif
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343 | u8_t sign;
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344 |
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345 | plen = 0;
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346 | while (p != NULL)
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347 | {
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348 | base = plen;
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349 | plen += p->len;
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350 | if (ofs < plen)
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351 | {
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352 | msg_ptr = (u8_t*)p->payload;
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353 | msg_ptr += ofs - base;
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354 | if ((len > 0) && (len < 5))
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355 | {
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356 | if (*msg_ptr & 0x80)
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357 | {
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358 | /* negative, start from -1 */
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359 | *value = -1;
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360 | sign = 1;
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361 | }
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362 | else
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363 | {
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364 | /* positive, start from 0 */
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365 | *value = 0;
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366 | sign = 0;
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367 | }
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368 | /* OR/AND octets with value */
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369 | while (len > 1)
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370 | {
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371 | len--;
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372 | if (sign)
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373 | {
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374 | *lsb_ptr &= *msg_ptr;
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375 | *value <<= 8;
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376 | *lsb_ptr |= 255;
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377 | }
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378 | else
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379 | {
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380 | *lsb_ptr |= *msg_ptr;
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381 | *value <<= 8;
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382 | }
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383 | ofs += 1;
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384 | if (ofs >= plen)
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385 | {
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386 | /* next octet in next pbuf */
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387 | p = p->next;
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388 | if (p == NULL) { return ERR_ARG; }
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389 | msg_ptr = (u8_t*)p->payload;
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390 | plen += p->len;
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391 | }
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392 | else
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393 | {
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394 | /* next octet in same pbuf */
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395 | msg_ptr++;
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396 | }
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397 | }
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398 | if (sign)
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399 | {
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400 | *lsb_ptr &= *msg_ptr;
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401 | }
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402 | else
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403 | {
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404 | *lsb_ptr |= *msg_ptr;
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405 | }
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406 | return ERR_OK;
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407 | }
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408 | else
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409 | {
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410 | return ERR_ARG;
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411 | }
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412 | }
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413 | p = p->next;
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414 | }
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415 | /* p == NULL, ofs >= plen */
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416 | return ERR_ARG;
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417 | }
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418 |
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419 | /**
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420 | * Decodes object identifier from incoming message into array of s32_t.
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421 | *
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422 | * @param p points to a pbuf holding an ASN1 coded object identifier
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423 | * @param ofs points to the offset within the pbuf chain of the ASN1 coded object identifier
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424 | * @param len length of the coded object identifier
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425 | * @param oid return object identifier struct
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426 | * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
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427 | */
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428 | err_t
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429 | snmp_asn1_dec_oid(struct pbuf *p, u16_t ofs, u16_t len, struct snmp_obj_id *oid)
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430 | {
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431 | u16_t plen, base;
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432 | u8_t *msg_ptr;
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433 | s32_t *oid_ptr;
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434 |
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435 | plen = 0;
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436 | while (p != NULL)
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437 | {
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438 | base = plen;
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439 | plen += p->len;
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440 | if (ofs < plen)
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441 | {
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442 | msg_ptr = (u8_t*)p->payload;
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443 | msg_ptr += ofs - base;
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444 |
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445 | oid->len = 0;
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446 | oid_ptr = &oid->id[0];
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447 | if (len > 0)
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448 | {
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449 | /* first compressed octet */
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450 | if (*msg_ptr == 0x2B)
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451 | {
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452 | /* (most) common case 1.3 (iso.org) */
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453 | *oid_ptr = 1;
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454 | oid_ptr++;
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455 | *oid_ptr = 3;
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456 | oid_ptr++;
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457 | }
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458 | else if (*msg_ptr < 40)
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459 | {
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460 | *oid_ptr = 0;
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461 | oid_ptr++;
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462 | *oid_ptr = *msg_ptr;
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463 | oid_ptr++;
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464 | }
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465 | else if (*msg_ptr < 80)
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466 | {
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467 | *oid_ptr = 1;
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468 | oid_ptr++;
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469 | *oid_ptr = (*msg_ptr) - 40;
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470 | oid_ptr++;
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471 | }
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472 | else
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473 | {
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474 | *oid_ptr = 2;
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475 | oid_ptr++;
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476 | *oid_ptr = (*msg_ptr) - 80;
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477 | oid_ptr++;
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478 | }
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479 | oid->len = 2;
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480 | }
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481 | else
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482 | {
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483 | /* accepting zero length identifiers e.g. for
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484 | getnext operation. uncommon but valid */
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485 | return ERR_OK;
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486 | }
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487 | len--;
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488 | if (len > 0)
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489 | {
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490 | ofs += 1;
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491 | if (ofs >= plen)
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492 | {
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493 | /* next octet in next pbuf */
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494 | p = p->next;
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495 | if (p == NULL) { return ERR_ARG; }
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496 | msg_ptr = (u8_t*)p->payload;
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497 | plen += p->len;
|
---|
498 | }
|
---|
499 | else
|
---|
500 | {
|
---|
501 | /* next octet in same pbuf */
|
---|
502 | msg_ptr++;
|
---|
503 | }
|
---|
504 | }
|
---|
505 | while ((len > 0) && (oid->len < LWIP_SNMP_OBJ_ID_LEN))
|
---|
506 | {
|
---|
507 | /* sub-identifier uses multiple octets */
|
---|
508 | if (*msg_ptr & 0x80)
|
---|
509 | {
|
---|
510 | s32_t sub_id = 0;
|
---|
511 |
|
---|
512 | while ((*msg_ptr & 0x80) && (len > 1))
|
---|
513 | {
|
---|
514 | len--;
|
---|
515 | sub_id = (sub_id << 7) + (*msg_ptr & ~0x80);
|
---|
516 | ofs += 1;
|
---|
517 | if (ofs >= plen)
|
---|
518 | {
|
---|
519 | /* next octet in next pbuf */
|
---|
520 | p = p->next;
|
---|
521 | if (p == NULL) { return ERR_ARG; }
|
---|
522 | msg_ptr = (u8_t*)p->payload;
|
---|
523 | plen += p->len;
|
---|
524 | }
|
---|
525 | else
|
---|
526 | {
|
---|
527 | /* next octet in same pbuf */
|
---|
528 | msg_ptr++;
|
---|
529 | }
|
---|
530 | }
|
---|
531 | if (!(*msg_ptr & 0x80) && (len > 0))
|
---|
532 | {
|
---|
533 | /* last octet sub-identifier */
|
---|
534 | len--;
|
---|
535 | sub_id = (sub_id << 7) + *msg_ptr;
|
---|
536 | *oid_ptr = sub_id;
|
---|
537 | }
|
---|
538 | }
|
---|
539 | else
|
---|
540 | {
|
---|
541 | /* !(*msg_ptr & 0x80) sub-identifier uses single octet */
|
---|
542 | len--;
|
---|
543 | *oid_ptr = *msg_ptr;
|
---|
544 | }
|
---|
545 | if (len > 0)
|
---|
546 | {
|
---|
547 | /* remaining oid bytes available ... */
|
---|
548 | ofs += 1;
|
---|
549 | if (ofs >= plen)
|
---|
550 | {
|
---|
551 | /* next octet in next pbuf */
|
---|
552 | p = p->next;
|
---|
553 | if (p == NULL) { return ERR_ARG; }
|
---|
554 | msg_ptr = (u8_t*)p->payload;
|
---|
555 | plen += p->len;
|
---|
556 | }
|
---|
557 | else
|
---|
558 | {
|
---|
559 | /* next octet in same pbuf */
|
---|
560 | msg_ptr++;
|
---|
561 | }
|
---|
562 | }
|
---|
563 | oid_ptr++;
|
---|
564 | oid->len++;
|
---|
565 | }
|
---|
566 | if (len == 0)
|
---|
567 | {
|
---|
568 | /* len == 0, end of oid */
|
---|
569 | return ERR_OK;
|
---|
570 | }
|
---|
571 | else
|
---|
572 | {
|
---|
573 | /* len > 0, oid->len == LWIP_SNMP_OBJ_ID_LEN or malformed encoding */
|
---|
574 | return ERR_ARG;
|
---|
575 | }
|
---|
576 |
|
---|
577 | }
|
---|
578 | p = p->next;
|
---|
579 | }
|
---|
580 | /* p == NULL, ofs >= plen */
|
---|
581 | return ERR_ARG;
|
---|
582 | }
|
---|
583 |
|
---|
584 | /**
|
---|
585 | * Decodes (copies) raw data (ip-addresses, octet strings, opaque encoding)
|
---|
586 | * from incoming message into array.
|
---|
587 | *
|
---|
588 | * @param p points to a pbuf holding an ASN1 coded raw data
|
---|
589 | * @param ofs points to the offset within the pbuf chain of the ASN1 coded raw data
|
---|
590 | * @param len length of the coded raw data (zero is valid, e.g. empty string!)
|
---|
591 | * @param raw_len length of the raw return value
|
---|
592 | * @param raw return raw bytes
|
---|
593 | * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
|
---|
594 | */
|
---|
595 | err_t
|
---|
596 | snmp_asn1_dec_raw(struct pbuf *p, u16_t ofs, u16_t len, u16_t raw_len, u8_t *raw)
|
---|
597 | {
|
---|
598 | u16_t plen, base;
|
---|
599 | u8_t *msg_ptr;
|
---|
600 |
|
---|
601 | if (len > 0)
|
---|
602 | {
|
---|
603 | plen = 0;
|
---|
604 | while (p != NULL)
|
---|
605 | {
|
---|
606 | base = plen;
|
---|
607 | plen += p->len;
|
---|
608 | if (ofs < plen)
|
---|
609 | {
|
---|
610 | msg_ptr = (u8_t*)p->payload;
|
---|
611 | msg_ptr += ofs - base;
|
---|
612 | if (raw_len >= len)
|
---|
613 | {
|
---|
614 | while (len > 1)
|
---|
615 | {
|
---|
616 | /* copy len - 1 octets */
|
---|
617 | len--;
|
---|
618 | *raw = *msg_ptr;
|
---|
619 | raw++;
|
---|
620 | ofs += 1;
|
---|
621 | if (ofs >= plen)
|
---|
622 | {
|
---|
623 | /* next octet in next pbuf */
|
---|
624 | p = p->next;
|
---|
625 | if (p == NULL) { return ERR_ARG; }
|
---|
626 | msg_ptr = (u8_t*)p->payload;
|
---|
627 | plen += p->len;
|
---|
628 | }
|
---|
629 | else
|
---|
630 | {
|
---|
631 | /* next octet in same pbuf */
|
---|
632 | msg_ptr++;
|
---|
633 | }
|
---|
634 | }
|
---|
635 | /* copy last octet */
|
---|
636 | *raw = *msg_ptr;
|
---|
637 | return ERR_OK;
|
---|
638 | }
|
---|
639 | else
|
---|
640 | {
|
---|
641 | /* raw_len < len, not enough dst space */
|
---|
642 | return ERR_ARG;
|
---|
643 | }
|
---|
644 | }
|
---|
645 | p = p->next;
|
---|
646 | }
|
---|
647 | /* p == NULL, ofs >= plen */
|
---|
648 | return ERR_ARG;
|
---|
649 | }
|
---|
650 | else
|
---|
651 | {
|
---|
652 | /* len == 0, empty string */
|
---|
653 | return ERR_OK;
|
---|
654 | }
|
---|
655 | }
|
---|
656 |
|
---|
657 | #endif /* LWIP_SNMP */
|
---|