1 | /*
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2 | * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
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3 | *
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4 | * Licensed under the OpenSSL license (the "License"). You may not use
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5 | * this file except in compliance with the License. You can obtain a copy
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6 | * in the file LICENSE in the source distribution or at
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7 | * https://www.openssl.org/source/license.html
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8 | */
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9 |
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10 | #include <stdio.h>
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11 | #include "internal/cryptlib.h"
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12 | #include <openssl/bn.h>
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13 | #include "dh_locl.h"
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14 |
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15 | /*-
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16 | * Check that p and g are suitable enough
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17 | *
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18 | * p is odd
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19 | * 1 < g < p - 1
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20 | */
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21 |
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22 | int DH_check_params(const DH *dh, int *ret)
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23 | {
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24 | int ok = 0;
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25 | BIGNUM *tmp = NULL;
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26 | BN_CTX *ctx = NULL;
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27 |
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28 | *ret = 0;
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29 | ctx = BN_CTX_new();
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30 | if (ctx == NULL)
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31 | goto err;
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32 | BN_CTX_start(ctx);
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33 | tmp = BN_CTX_get(ctx);
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34 | if (tmp == NULL)
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35 | goto err;
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36 |
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37 | if (!BN_is_odd(dh->p))
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38 | *ret |= DH_CHECK_P_NOT_PRIME;
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39 | if (BN_is_negative(dh->g) || BN_is_zero(dh->g) || BN_is_one(dh->g))
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40 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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41 | if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
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42 | goto err;
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43 | if (BN_cmp(dh->g, tmp) >= 0)
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44 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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45 |
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46 | ok = 1;
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47 | err:
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48 | if (ctx != NULL) {
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49 | BN_CTX_end(ctx);
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50 | BN_CTX_free(ctx);
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51 | }
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52 | return (ok);
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53 | }
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54 |
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55 | /*-
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56 | * Check that p is a safe prime and
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57 | * if g is 2, 3 or 5, check that it is a suitable generator
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58 | * where
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59 | * for 2, p mod 24 == 11
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60 | * for 3, p mod 12 == 5
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61 | * for 5, p mod 10 == 3 or 7
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62 | * should hold.
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63 | */
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64 |
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65 | int DH_check(const DH *dh, int *ret)
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66 | {
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67 | int ok = 0, r;
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68 | BN_CTX *ctx = NULL;
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69 | BN_ULONG l;
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70 | BIGNUM *t1 = NULL, *t2 = NULL;
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71 |
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72 | *ret = 0;
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73 | ctx = BN_CTX_new();
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74 | if (ctx == NULL)
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75 | goto err;
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76 | BN_CTX_start(ctx);
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77 | t1 = BN_CTX_get(ctx);
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78 | if (t1 == NULL)
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79 | goto err;
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80 | t2 = BN_CTX_get(ctx);
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81 | if (t2 == NULL)
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82 | goto err;
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83 |
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84 | if (dh->q) {
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85 | if (BN_cmp(dh->g, BN_value_one()) <= 0)
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86 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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87 | else if (BN_cmp(dh->g, dh->p) >= 0)
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88 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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89 | else {
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90 | /* Check g^q == 1 mod p */
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91 | if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
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92 | goto err;
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93 | if (!BN_is_one(t1))
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94 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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95 | }
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96 | r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
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97 | if (r < 0)
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98 | goto err;
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99 | if (!r)
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100 | *ret |= DH_CHECK_Q_NOT_PRIME;
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101 | /* Check p == 1 mod q i.e. q divides p - 1 */
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102 | if (!BN_div(t1, t2, dh->p, dh->q, ctx))
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103 | goto err;
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104 | if (!BN_is_one(t2))
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105 | *ret |= DH_CHECK_INVALID_Q_VALUE;
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106 | if (dh->j && BN_cmp(dh->j, t1))
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107 | *ret |= DH_CHECK_INVALID_J_VALUE;
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108 |
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109 | } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
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110 | l = BN_mod_word(dh->p, 24);
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111 | if (l == (BN_ULONG)-1)
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112 | goto err;
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113 | if (l != 11)
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114 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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115 | } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
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116 | l = BN_mod_word(dh->p, 10);
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117 | if (l == (BN_ULONG)-1)
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118 | goto err;
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119 | if ((l != 3) && (l != 7))
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120 | *ret |= DH_NOT_SUITABLE_GENERATOR;
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121 | } else
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122 | *ret |= DH_UNABLE_TO_CHECK_GENERATOR;
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123 |
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124 | r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
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125 | if (r < 0)
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126 | goto err;
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127 | if (!r)
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128 | *ret |= DH_CHECK_P_NOT_PRIME;
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129 | else if (!dh->q) {
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130 | if (!BN_rshift1(t1, dh->p))
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131 | goto err;
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132 | r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
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133 | if (r < 0)
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134 | goto err;
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135 | if (!r)
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136 | *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
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137 | }
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138 | ok = 1;
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139 | err:
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140 | if (ctx != NULL) {
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141 | BN_CTX_end(ctx);
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142 | BN_CTX_free(ctx);
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143 | }
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144 | return (ok);
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145 | }
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146 |
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147 | int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
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148 | {
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149 | int ok = 0;
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150 | BIGNUM *tmp = NULL;
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151 | BN_CTX *ctx = NULL;
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152 |
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153 | *ret = 0;
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154 | ctx = BN_CTX_new();
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155 | if (ctx == NULL)
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156 | goto err;
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157 | BN_CTX_start(ctx);
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158 | tmp = BN_CTX_get(ctx);
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159 | if (tmp == NULL || !BN_set_word(tmp, 1))
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160 | goto err;
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161 | if (BN_cmp(pub_key, tmp) <= 0)
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162 | *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
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163 | if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
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164 | goto err;
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165 | if (BN_cmp(pub_key, tmp) >= 0)
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166 | *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
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167 |
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168 | if (dh->q != NULL) {
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169 | /* Check pub_key^q == 1 mod p */
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170 | if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx))
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171 | goto err;
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172 | if (!BN_is_one(tmp))
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173 | *ret |= DH_CHECK_PUBKEY_INVALID;
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174 | }
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175 |
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176 | ok = 1;
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177 | err:
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178 | if (ctx != NULL) {
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179 | BN_CTX_end(ctx);
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180 | BN_CTX_free(ctx);
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181 | }
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182 | return (ok);
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183 | }
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