1 | /* |
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2 | * dhcpcd - DHCP client daemon |
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3 | * Copyright (c) 2006-2014 Roy Marples <roy@marples.name> |
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4 | * All rights reserved |
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5 | |
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6 | * Redistribution and use in source and binary forms, with or without |
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7 | * modification, are permitted provided that the following conditions |
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8 | * are met: |
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9 | * 1. Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * 2. Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * |
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15 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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16 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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17 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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18 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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19 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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20 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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21 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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22 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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23 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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24 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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25 | * SUCH DAMAGE. |
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26 | */ |
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27 | |
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28 | #include <sys/file.h> |
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29 | #include <sys/queue.h> |
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30 | #include <errno.h> |
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31 | #include <fcntl.h> |
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32 | #include <inttypes.h> |
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33 | #include <stddef.h> |
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34 | #include <stdlib.h> |
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35 | #include <string.h> |
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36 | #include <syslog.h> |
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37 | #include <time.h> |
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38 | #include <unistd.h> |
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39 | |
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40 | #include "config.h" |
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41 | #include "auth.h" |
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42 | #include "crypt/crypt.h" |
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43 | #include "dhcp.h" |
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44 | #include "dhcp6.h" |
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45 | #include "dhcpcd.h" |
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46 | |
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47 | #ifndef htonll |
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48 | #if (BYTE_ORDER == LITTLE_ENDIAN) |
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49 | static inline uint64_t |
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50 | htonll(uint64_t x) |
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51 | { |
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52 | |
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53 | return (uint64_t)htonl((uint32_t)(x >> 32)) | |
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54 | (int64_t)htonl((uint32_t)(x & 0xffffffff)) << 32; |
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55 | } |
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56 | #else /* (BYTE_ORDER == LITTLE_ENDIAN) */ |
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57 | #define htonll(x) (x) |
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58 | #endif |
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59 | #endif /* htonll */ |
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60 | |
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61 | #ifndef ntohll |
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62 | #if (BYTE_ORDER == LITTLE_ENDIAN) |
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63 | static inline uint64_t |
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64 | ntohll(uint64_t x) |
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65 | { |
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66 | |
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67 | return (uint64_t)ntohl((uint32_t)(x >> 32)) | |
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68 | (int64_t)ntohl((uint32_t)(x & 0xffffffff)) << 32; |
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69 | } |
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70 | #else /* (BYTE_ORDER == LITTLE_ENDIAN) */ |
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71 | #define ntohll(x) (x) |
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72 | #endif |
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73 | #endif /* ntohll */ |
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74 | |
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75 | #define HMAC_LENGTH 16 |
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76 | |
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77 | /* |
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78 | * Authenticate a DHCP message. |
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79 | * m and mlen refer to the whole message. |
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80 | * t is the DHCP type, pass it 4 or 6. |
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81 | * data and dlen refer to the authentication option within the message. |
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82 | */ |
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83 | const struct token * |
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84 | dhcp_auth_validate(struct authstate *state, const struct auth *auth, |
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85 | const uint8_t *m, unsigned int mlen, int mp, int mt, |
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86 | const uint8_t *data, unsigned int dlen) |
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87 | { |
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88 | uint8_t protocol, algorithm, rdm, *mm, type; |
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89 | uint64_t replay; |
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90 | uint32_t secretid; |
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91 | const uint8_t *d, *realm; |
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92 | unsigned int realm_len; |
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93 | const struct token *t; |
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94 | time_t now; |
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95 | uint8_t hmac[HMAC_LENGTH]; |
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96 | |
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97 | if (dlen < 3 + sizeof(replay)) { |
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98 | errno = EINVAL; |
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99 | return NULL; |
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100 | } |
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101 | |
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102 | /* Ensure that d is inside m which *may* not be the case for DHPCPv4 */ |
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103 | if (data < m || data > m + mlen || data + dlen > m + mlen) { |
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104 | errno = ERANGE; |
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105 | return NULL; |
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106 | } |
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107 | |
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108 | d = data; |
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109 | protocol = *d++; |
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110 | algorithm = *d++; |
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111 | rdm = *d++; |
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112 | if (!(auth->options & DHCPCD_AUTH_SEND)) { |
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113 | /* If we didn't send any authorisation, it can only be a |
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114 | * reconfigure key */ |
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115 | if (protocol != AUTH_PROTO_RECONFKEY) { |
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116 | errno = EINVAL; |
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117 | return NULL; |
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118 | } |
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119 | } else if (protocol != auth->protocol || |
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120 | algorithm != auth->algorithm || |
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121 | rdm != auth->rdm) |
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122 | { |
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123 | errno = EPERM; |
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124 | return NULL; |
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125 | } |
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126 | |
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127 | dlen -= 3; |
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128 | memcpy(&replay, d, sizeof(replay)); |
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129 | replay = ntohll(replay); |
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130 | d+= sizeof(replay); |
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131 | dlen -= sizeof(replay); |
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132 | |
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133 | if (state->token && replay - state->replay <= 0) { |
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134 | /* Replay attack detected */ |
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135 | errno = EPERM; |
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136 | return NULL; |
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137 | } |
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138 | |
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139 | realm = NULL; |
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140 | realm_len = 0; |
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141 | |
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142 | /* Extract realm and secret. |
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143 | * Rest of data is MAC. */ |
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144 | switch (protocol) { |
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145 | case AUTH_PROTO_TOKEN: |
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146 | secretid = 0; |
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147 | break; |
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148 | case AUTH_PROTO_DELAYED: |
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149 | if (dlen < sizeof(secretid) + sizeof(hmac)) { |
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150 | errno = EINVAL; |
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151 | return NULL; |
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152 | } |
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153 | memcpy(&secretid, d, sizeof(secretid)); |
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154 | d += sizeof(secretid); |
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155 | dlen -= sizeof(secretid); |
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156 | break; |
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157 | case AUTH_PROTO_DELAYEDREALM: |
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158 | if (dlen < sizeof(secretid) + sizeof(hmac)) { |
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159 | errno = EINVAL; |
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160 | return NULL; |
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161 | } |
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162 | realm_len = dlen - (sizeof(secretid) + sizeof(hmac)); |
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163 | if (realm_len) { |
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164 | realm = d; |
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165 | d += realm_len; |
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166 | dlen -= realm_len; |
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167 | } |
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168 | memcpy(&secretid, d, sizeof(secretid)); |
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169 | d += sizeof(secretid); |
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170 | dlen -= sizeof(secretid); |
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171 | break; |
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172 | case AUTH_PROTO_RECONFKEY: |
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173 | if (dlen != 1 + 16) { |
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174 | errno = EINVAL; |
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175 | return NULL; |
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176 | } |
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177 | type = *d++; |
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178 | dlen--; |
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179 | switch (type) { |
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180 | case 1: |
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181 | if ((mp == 4 && mt == DHCP_ACK) || |
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182 | (mp == 6 && mt == DHCP6_REPLY)) |
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183 | { |
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184 | if (state->reconf == NULL) { |
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185 | state->reconf = |
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186 | malloc(sizeof(*state->reconf)); |
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187 | if (state->reconf == NULL) |
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188 | return NULL; |
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189 | state->reconf->key = malloc(16); |
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190 | if (state->reconf->key == NULL) { |
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191 | free(state->reconf); |
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192 | state->reconf = NULL; |
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193 | return NULL; |
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194 | } |
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195 | state->reconf->secretid = 0; |
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196 | state->reconf->expire = 0; |
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197 | state->reconf->realm = NULL; |
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198 | state->reconf->realm_len = 0; |
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199 | state->reconf->key_len = 16; |
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200 | } |
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201 | memcpy(state->reconf->key, d, 16); |
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202 | } else { |
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203 | errno = EINVAL; |
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204 | return NULL; |
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205 | } |
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206 | if (state->reconf == NULL) |
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207 | errno = ENOENT; |
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208 | /* Nothing to validate, just accepting the key */ |
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209 | return state->reconf; |
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210 | case 2: |
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211 | if (state->reconf == NULL) { |
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212 | errno = ENOENT; |
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213 | return NULL; |
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214 | } |
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215 | t = state->reconf; |
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216 | goto gottoken; |
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217 | default: |
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218 | errno = EINVAL; |
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219 | return NULL; |
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220 | } |
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221 | default: |
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222 | errno = ENOTSUP; |
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223 | return NULL; |
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224 | } |
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225 | |
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226 | /* Find a token for the realm and secret */ |
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227 | secretid = ntohl(secretid); |
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228 | TAILQ_FOREACH(t, &auth->tokens, next) { |
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229 | if (t->secretid == secretid && |
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230 | t->realm_len == realm_len && |
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231 | (t->realm_len == 0 || |
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232 | memcmp(t->realm, realm, t->realm_len) == 0)) |
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233 | break; |
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234 | } |
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235 | if (t == NULL) { |
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236 | errno = ESRCH; |
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237 | return NULL; |
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238 | } |
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239 | if (t->expire) { |
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240 | if (time(&now) == -1) |
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241 | return NULL; |
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242 | if (t->expire < now) { |
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243 | errno = EFAULT; |
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244 | return NULL; |
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245 | } |
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246 | } |
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247 | |
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248 | gottoken: |
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249 | /* First message from the server */ |
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250 | if (state->token && state->token != t) { |
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251 | errno = EPERM; |
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252 | return NULL; |
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253 | } |
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254 | |
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255 | /* Special case as no hashing needs to be done. */ |
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256 | if (protocol == AUTH_PROTO_TOKEN) { |
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257 | if (dlen != t->key_len || memcmp(d, t->key, dlen)) { |
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258 | errno = EPERM; |
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259 | return NULL; |
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260 | } |
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261 | goto finish; |
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262 | } |
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263 | |
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264 | /* Make a duplicate of the message, but zero out the MAC part */ |
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265 | mm = malloc(mlen); |
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266 | if (mm == NULL) |
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267 | return NULL; |
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268 | memcpy(mm, m, mlen); |
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269 | memset(mm + (d - m), 0, dlen); |
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270 | |
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271 | /* RFC3318, section 5.2 - zero giaddr and hops */ |
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272 | if (mp == 4) { |
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273 | *(mm + offsetof(struct dhcp_message, hwopcount)) = '\0'; |
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274 | memset(mm + offsetof(struct dhcp_message, giaddr), 0, 4); |
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275 | } |
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276 | |
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277 | memset(hmac, 0, sizeof(hmac)); |
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278 | switch (algorithm) { |
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279 | case AUTH_ALG_HMAC_MD5: |
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280 | hmac_md5(mm, mlen, t->key, t->key_len, hmac); |
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281 | break; |
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282 | default: |
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283 | errno = ENOSYS; |
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284 | free(mm); |
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285 | return NULL; |
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286 | } |
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287 | |
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288 | free(mm); |
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289 | if (memcmp(d, &hmac, dlen)) { |
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290 | errno = EPERM; |
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291 | return NULL; |
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292 | } |
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293 | |
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294 | finish: |
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295 | /* If we got here then authentication passed */ |
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296 | state->replay = replay; |
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297 | state->token = t; |
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298 | |
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299 | return t; |
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300 | } |
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301 | |
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302 | static uint64_t last_rdm; |
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303 | static uint8_t last_rdm_set; |
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304 | static uint64_t |
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305 | get_next_rdm_monotonic(void) |
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306 | { |
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307 | FILE *fp; |
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308 | char *line, *ep; |
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309 | uint64_t rdm; |
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310 | int flocked; |
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311 | |
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312 | fp = fopen(RDM_MONOFILE, "r+"); |
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313 | if (fp == NULL) { |
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314 | if (errno != ENOENT) |
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315 | return ++last_rdm; /* report error? */ |
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316 | fp = fopen(RDM_MONOFILE, "w"); |
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317 | if (fp == NULL) |
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318 | return ++last_rdm; /* report error? */ |
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319 | flocked = flock(fileno(fp), LOCK_EX); |
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320 | rdm = 0; |
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321 | } else { |
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322 | flocked = flock(fileno(fp), LOCK_EX); |
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323 | line = get_line(fp); |
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324 | if (line == NULL) |
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325 | rdm = 0; /* truncated? report error? */ |
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326 | else |
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327 | rdm = strtoull(line, &ep, 0); |
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328 | } |
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329 | |
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330 | rdm++; |
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331 | if (fseek(fp, 0, SEEK_SET) == -1 || |
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332 | ftruncate(fileno(fp), 0) == -1 || |
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333 | fprintf(fp, "0x%016" PRIu64 "\n", rdm) != 19) |
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334 | { |
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335 | if (!last_rdm_set) { |
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336 | last_rdm = rdm; |
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337 | last_rdm_set = 1; |
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338 | } else |
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339 | rdm = ++last_rdm; |
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340 | /* report error? */ |
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341 | } |
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342 | fflush(fp); |
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343 | if (flocked == 0) |
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344 | flock(fileno(fp), LOCK_UN); |
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345 | fclose(fp); |
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346 | return rdm; |
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347 | } |
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348 | |
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349 | |
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350 | /* |
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351 | * Encode a DHCP message. |
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352 | * Either we know which token to use from the server response |
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353 | * or we are using a basic configuration token. |
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354 | * token is the token to encrypt with. |
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355 | * m and mlen refer to the whole message. |
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356 | * mp is the DHCP type, pass it 4 or 6. |
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357 | * mt is the DHCP message type. |
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358 | * data and dlen refer to the authentication option within the message. |
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359 | */ |
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360 | int |
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361 | dhcp_auth_encode(const struct auth *auth, const struct token *t, |
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362 | uint8_t *m, unsigned int mlen, int mp, int mt, |
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363 | uint8_t *data, unsigned int dlen) |
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364 | { |
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365 | uint64_t rdm; |
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366 | uint8_t hmac[HMAC_LENGTH]; |
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367 | time_t now; |
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368 | uint8_t hops, *p, info; |
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369 | uint32_t giaddr, secretid; |
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370 | |
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371 | if (auth->protocol == 0 && t == NULL) { |
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372 | TAILQ_FOREACH(t, &auth->tokens, next) { |
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373 | if (t->secretid == 0 && |
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374 | t->realm_len == 0) |
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375 | break; |
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376 | } |
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377 | if (t == NULL) { |
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378 | errno = EINVAL; |
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379 | return -1; |
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380 | } |
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381 | if (t->expire) { |
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382 | if (time(&now) == -1) |
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383 | return -1; |
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384 | if (t->expire < now) { |
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385 | errno = EPERM; |
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386 | return -1; |
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387 | } |
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388 | } |
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389 | } |
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390 | |
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391 | switch(auth->protocol) { |
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392 | case AUTH_PROTO_TOKEN: |
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393 | case AUTH_PROTO_DELAYED: |
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394 | case AUTH_PROTO_DELAYEDREALM: |
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395 | /* We don't ever send a reconf key */ |
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396 | break; |
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397 | default: |
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398 | errno = ENOTSUP; |
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399 | return -1; |
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400 | } |
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401 | |
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402 | switch(auth->algorithm) { |
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403 | case AUTH_ALG_HMAC_MD5: |
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404 | break; |
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405 | default: |
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406 | errno = ENOTSUP; |
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407 | return -1; |
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408 | } |
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409 | |
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410 | switch(auth->rdm) { |
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411 | case AUTH_RDM_MONOTONIC: |
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412 | break; |
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413 | default: |
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414 | errno = ENOTSUP; |
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415 | return -1; |
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416 | } |
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417 | |
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418 | /* DISCOVER or INFORM messages don't write auth info */ |
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419 | if ((mp == 4 && (mt == DHCP_DISCOVER || mt == DHCP_INFORM)) || |
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420 | (mp == 6 && (mt == DHCP6_SOLICIT || mt == DHCP6_INFORMATION_REQ))) |
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421 | info = 0; |
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422 | else |
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423 | info = 1; |
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424 | |
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425 | /* Work out the auth area size. |
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426 | * We only need to do this for DISCOVER messages */ |
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427 | if (data == NULL) { |
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428 | dlen = 1 + 1 + 1 + 8; |
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429 | switch(auth->protocol) { |
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430 | case AUTH_PROTO_TOKEN: |
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431 | dlen += t->key_len; |
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432 | break; |
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433 | case AUTH_PROTO_DELAYEDREALM: |
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434 | if (info && t) |
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435 | dlen += t->realm_len; |
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436 | /* FALLTHROUGH */ |
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437 | case AUTH_PROTO_DELAYED: |
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438 | if (info && t) |
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439 | dlen += sizeof(t->secretid) + sizeof(hmac); |
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440 | break; |
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441 | } |
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442 | return dlen; |
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443 | } |
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444 | |
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445 | if (dlen < 1 + 1 + 1 + 8) { |
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446 | errno = ENOBUFS; |
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447 | return -1; |
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448 | } |
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449 | |
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450 | /* Ensure that d is inside m which *may* not be the case for DHPCPv4 */ |
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451 | if (data < m || data > m + mlen || data + dlen > m + mlen) { |
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452 | errno = ERANGE; |
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453 | return -1; |
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454 | } |
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455 | |
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456 | /* Write out our option */ |
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457 | *data++ = auth->protocol; |
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458 | *data++ = auth->algorithm; |
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459 | *data++ = auth->rdm; |
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460 | switch (auth->rdm) { |
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461 | case AUTH_RDM_MONOTONIC: |
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462 | rdm = get_next_rdm_monotonic(); |
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463 | break; |
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464 | default: |
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465 | /* This block appeases gcc, clang doesn't need it */ |
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466 | rdm = get_next_rdm_monotonic(); |
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467 | break; |
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468 | } |
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469 | rdm = htonll(rdm); |
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470 | memcpy(data, &rdm, 8); |
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471 | data += 8; |
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472 | dlen -= 1 + 1 + 1 + 8; |
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473 | |
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474 | /* Special case as no hashing needs to be done. */ |
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475 | if (auth->protocol == AUTH_PROTO_TOKEN) { |
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476 | /* Should be impossible, but still */ |
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477 | if (t == NULL) { |
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478 | errno = EINVAL; |
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479 | return -1; |
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480 | } |
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481 | if (dlen < t->key_len) { |
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482 | errno = ENOBUFS; |
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483 | return -1; |
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484 | } |
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485 | memcpy(data, t->key, t->key_len); |
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486 | return dlen - t->key_len; |
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487 | } |
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488 | |
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489 | /* DISCOVER or INFORM messages don't write auth info */ |
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490 | if (!info) |
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491 | return dlen; |
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492 | |
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493 | /* Loading a saved lease without an authentication option */ |
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494 | if (t == NULL) |
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495 | return 0; |
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496 | |
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497 | /* Write out the Realm */ |
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498 | if (auth->protocol == AUTH_PROTO_DELAYEDREALM) { |
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499 | if (dlen < t->realm_len) { |
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500 | errno = ENOBUFS; |
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501 | return -1; |
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502 | } |
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503 | memcpy(data, t->realm, t->realm_len); |
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504 | data += t->realm_len; |
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505 | dlen -= t->realm_len; |
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506 | } |
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507 | |
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508 | /* Write out the SecretID */ |
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509 | if (auth->protocol == AUTH_PROTO_DELAYED || |
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510 | auth->protocol == AUTH_PROTO_DELAYEDREALM) |
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511 | { |
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512 | if (dlen < sizeof(t->secretid)) { |
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513 | errno = ENOBUFS; |
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514 | return -1; |
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515 | } |
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516 | secretid = htonl(t->secretid); |
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517 | memcpy(data, &secretid, sizeof(secretid)); |
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518 | data += sizeof(secretid); |
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519 | dlen -= sizeof(secretid); |
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520 | } |
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521 | |
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522 | /* Zero what's left, the MAC */ |
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523 | memset(data, 0, dlen); |
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524 | |
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525 | /* RFC3318, section 5.2 - zero giaddr and hops */ |
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526 | if (mp == 4) { |
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527 | p = m + offsetof(struct dhcp_message, hwopcount); |
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528 | hops = *p; |
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529 | *p = '\0'; |
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530 | p = m + offsetof(struct dhcp_message, giaddr); |
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531 | memcpy(&giaddr, p, sizeof(giaddr)); |
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532 | memset(p, 0, sizeof(giaddr)); |
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533 | } else { |
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534 | /* appease GCC again */ |
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535 | hops = 0; |
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536 | giaddr = 0; |
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537 | } |
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538 | |
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539 | /* Create our hash and write it out */ |
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540 | switch(auth->algorithm) { |
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541 | case AUTH_ALG_HMAC_MD5: |
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542 | hmac_md5(m, mlen, t->key, t->key_len, hmac); |
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543 | memcpy(data, hmac, sizeof(hmac)); |
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544 | break; |
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545 | } |
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546 | |
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547 | /* RFC3318, section 5.2 - restore giaddr and hops */ |
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548 | if (mp == 4) { |
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549 | p = m + offsetof(struct dhcp_message, hwopcount); |
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550 | *p = hops; |
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551 | p = m + offsetof(struct dhcp_message, giaddr); |
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552 | memcpy(p, &giaddr, sizeof(giaddr)); |
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553 | } |
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554 | |
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555 | /* Done! */ |
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556 | return dlen - sizeof(hmac); /* should be zero */ |
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557 | } |
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