1 | /*
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2 | * Copyright 2011-2016 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 | #ifndef OPENSSL_NO_SRP
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11 | # include "internal/cryptlib.h"
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12 | # include <openssl/sha.h>
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13 | # include <openssl/srp.h>
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14 | # include <openssl/evp.h>
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15 | # include "internal/bn_srp.h"
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16 |
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17 | /* calculate = SHA1(PAD(x) || PAD(y)) */
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18 |
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19 | static BIGNUM *srp_Calc_xy(const BIGNUM *x, const BIGNUM *y, const BIGNUM *N)
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20 | {
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21 | unsigned char digest[SHA_DIGEST_LENGTH];
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22 | unsigned char *tmp = NULL;
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23 | int numN = BN_num_bytes(N);
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24 | BIGNUM *res = NULL;
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25 | if (x != N && BN_ucmp(x, N) >= 0)
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26 | return NULL;
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27 | if (y != N && BN_ucmp(y, N) >= 0)
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28 | return NULL;
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29 | if ((tmp = OPENSSL_malloc(numN * 2)) == NULL)
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30 | goto err;
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31 | if (BN_bn2binpad(x, tmp, numN) < 0
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32 | || BN_bn2binpad(y, tmp + numN, numN) < 0
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33 | || !EVP_Digest(tmp, numN * 2, digest, NULL, EVP_sha1(), NULL))
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34 | goto err;
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35 | res = BN_bin2bn(digest, sizeof(digest), NULL);
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36 | err:
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37 | OPENSSL_free(tmp);
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38 | return res;
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39 | }
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40 |
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41 | static BIGNUM *srp_Calc_k(const BIGNUM *N, const BIGNUM *g)
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42 | {
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43 | /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
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44 | return srp_Calc_xy(N, g, N);
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45 | }
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46 |
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47 | BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N)
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48 | {
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49 | /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
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50 | return srp_Calc_xy(A, B, N);
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51 | }
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52 |
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53 | BIGNUM *SRP_Calc_server_key(const BIGNUM *A, const BIGNUM *v, const BIGNUM *u,
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54 | const BIGNUM *b, const BIGNUM *N)
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55 | {
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56 | BIGNUM *tmp = NULL, *S = NULL;
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57 | BN_CTX *bn_ctx;
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58 |
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59 | if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)
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60 | return NULL;
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61 |
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62 | if ((bn_ctx = BN_CTX_new()) == NULL || (tmp = BN_new()) == NULL)
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63 | goto err;
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64 |
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65 | /* S = (A*v**u) ** b */
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66 |
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67 | if (!BN_mod_exp(tmp, v, u, N, bn_ctx))
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68 | goto err;
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69 | if (!BN_mod_mul(tmp, A, tmp, N, bn_ctx))
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70 | goto err;
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71 |
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72 | S = BN_new();
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73 | if (S != NULL && !BN_mod_exp(S, tmp, b, N, bn_ctx)) {
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74 | BN_free(S);
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75 | S = NULL;
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76 | }
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77 | err:
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78 | BN_CTX_free(bn_ctx);
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79 | BN_clear_free(tmp);
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80 | return S;
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81 | }
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82 |
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83 | BIGNUM *SRP_Calc_B(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,
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84 | const BIGNUM *v)
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85 | {
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86 | BIGNUM *kv = NULL, *gb = NULL;
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87 | BIGNUM *B = NULL, *k = NULL;
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88 | BN_CTX *bn_ctx;
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89 |
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90 | if (b == NULL || N == NULL || g == NULL || v == NULL ||
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91 | (bn_ctx = BN_CTX_new()) == NULL)
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92 | return NULL;
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93 |
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94 | if ((kv = BN_new()) == NULL ||
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95 | (gb = BN_new()) == NULL || (B = BN_new()) == NULL)
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96 | goto err;
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97 |
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98 | /* B = g**b + k*v */
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99 |
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100 | if (!BN_mod_exp(gb, g, b, N, bn_ctx)
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101 | || (k = srp_Calc_k(N, g)) == NULL
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102 | || !BN_mod_mul(kv, v, k, N, bn_ctx)
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103 | || !BN_mod_add(B, gb, kv, N, bn_ctx)) {
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104 | BN_free(B);
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105 | B = NULL;
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106 | }
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107 | err:
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108 | BN_CTX_free(bn_ctx);
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109 | BN_clear_free(kv);
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110 | BN_clear_free(gb);
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111 | BN_free(k);
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112 | return B;
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113 | }
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114 |
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115 | BIGNUM *SRP_Calc_x(const BIGNUM *s, const char *user, const char *pass)
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116 | {
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117 | unsigned char dig[SHA_DIGEST_LENGTH];
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118 | EVP_MD_CTX *ctxt;
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119 | unsigned char *cs = NULL;
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120 | BIGNUM *res = NULL;
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121 |
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122 | if ((s == NULL) || (user == NULL) || (pass == NULL))
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123 | return NULL;
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124 |
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125 | ctxt = EVP_MD_CTX_new();
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126 | if (ctxt == NULL)
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127 | return NULL;
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128 | if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)
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129 | goto err;
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130 |
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131 | if (!EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL)
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132 | || !EVP_DigestUpdate(ctxt, user, strlen(user))
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133 | || !EVP_DigestUpdate(ctxt, ":", 1)
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134 | || !EVP_DigestUpdate(ctxt, pass, strlen(pass))
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135 | || !EVP_DigestFinal_ex(ctxt, dig, NULL)
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136 | || !EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL))
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137 | goto err;
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138 | BN_bn2bin(s, cs);
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139 | if (!EVP_DigestUpdate(ctxt, cs, BN_num_bytes(s)))
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140 | goto err;
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141 |
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142 | if (!EVP_DigestUpdate(ctxt, dig, sizeof(dig))
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143 | || !EVP_DigestFinal_ex(ctxt, dig, NULL))
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144 | goto err;
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145 |
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146 | res = BN_bin2bn(dig, sizeof(dig), NULL);
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147 |
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148 | err:
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149 | OPENSSL_free(cs);
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150 | EVP_MD_CTX_free(ctxt);
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151 | return res;
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152 | }
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153 |
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154 | BIGNUM *SRP_Calc_A(const BIGNUM *a, const BIGNUM *N, const BIGNUM *g)
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155 | {
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156 | BN_CTX *bn_ctx;
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157 | BIGNUM *A = NULL;
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158 |
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159 | if (a == NULL || N == NULL || g == NULL || (bn_ctx = BN_CTX_new()) == NULL)
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160 | return NULL;
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161 |
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162 | if ((A = BN_new()) != NULL && !BN_mod_exp(A, g, a, N, bn_ctx)) {
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163 | BN_free(A);
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164 | A = NULL;
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165 | }
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166 | BN_CTX_free(bn_ctx);
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167 | return A;
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168 | }
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169 |
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170 | BIGNUM *SRP_Calc_client_key(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,
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171 | const BIGNUM *x, const BIGNUM *a, const BIGNUM *u)
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172 | {
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173 | BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;
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174 | BN_CTX *bn_ctx;
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175 |
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176 | if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL
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177 | || a == NULL || (bn_ctx = BN_CTX_new()) == NULL)
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178 | return NULL;
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179 |
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180 | if ((tmp = BN_new()) == NULL ||
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181 | (tmp2 = BN_new()) == NULL ||
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182 | (tmp3 = BN_new()) == NULL)
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183 | goto err;
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184 |
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185 | if (!BN_mod_exp(tmp, g, x, N, bn_ctx))
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186 | goto err;
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187 | if ((k = srp_Calc_k(N, g)) == NULL)
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188 | goto err;
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189 | if (!BN_mod_mul(tmp2, tmp, k, N, bn_ctx))
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190 | goto err;
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191 | if (!BN_mod_sub(tmp, B, tmp2, N, bn_ctx))
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192 | goto err;
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193 | if (!BN_mul(tmp3, u, x, bn_ctx))
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194 | goto err;
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195 | if (!BN_add(tmp2, a, tmp3))
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196 | goto err;
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197 | K = BN_new();
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198 | if (K != NULL && !BN_mod_exp(K, tmp, tmp2, N, bn_ctx)) {
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199 | BN_free(K);
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200 | K = NULL;
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201 | }
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202 |
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203 | err:
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204 | BN_CTX_free(bn_ctx);
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205 | BN_clear_free(tmp);
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206 | BN_clear_free(tmp2);
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207 | BN_clear_free(tmp3);
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208 | BN_free(k);
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209 | return K;
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210 | }
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211 |
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212 | int SRP_Verify_B_mod_N(const BIGNUM *B, const BIGNUM *N)
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213 | {
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214 | BIGNUM *r;
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215 | BN_CTX *bn_ctx;
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216 | int ret = 0;
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217 |
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218 | if (B == NULL || N == NULL || (bn_ctx = BN_CTX_new()) == NULL)
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219 | return 0;
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220 |
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221 | if ((r = BN_new()) == NULL)
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222 | goto err;
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223 | /* Checks if B % N == 0 */
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224 | if (!BN_nnmod(r, B, N, bn_ctx))
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225 | goto err;
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226 | ret = !BN_is_zero(r);
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227 | err:
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228 | BN_CTX_free(bn_ctx);
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229 | BN_free(r);
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230 | return ret;
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231 | }
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232 |
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233 | int SRP_Verify_A_mod_N(const BIGNUM *A, const BIGNUM *N)
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234 | {
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235 | /* Checks if A % N == 0 */
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236 | return SRP_Verify_B_mod_N(A, N);
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237 | }
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238 |
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239 | static SRP_gN knowngN[] = {
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240 | {"8192", &bn_generator_19, &bn_group_8192},
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241 | {"6144", &bn_generator_5, &bn_group_6144},
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242 | {"4096", &bn_generator_5, &bn_group_4096},
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243 | {"3072", &bn_generator_5, &bn_group_3072},
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244 | {"2048", &bn_generator_2, &bn_group_2048},
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245 | {"1536", &bn_generator_2, &bn_group_1536},
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246 | {"1024", &bn_generator_2, &bn_group_1024},
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247 | };
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248 |
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249 | # define KNOWN_GN_NUMBER sizeof(knowngN) / sizeof(SRP_gN)
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250 |
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251 | /*
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252 | * Check if G and N are known parameters. The values have been generated
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253 | * from the ietf-tls-srp draft version 8
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254 | */
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255 | char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N)
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256 | {
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257 | size_t i;
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258 | if ((g == NULL) || (N == NULL))
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259 | return 0;
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260 |
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261 | for (i = 0; i < KNOWN_GN_NUMBER; i++) {
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262 | if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)
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263 | return knowngN[i].id;
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264 | }
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265 | return NULL;
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266 | }
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267 |
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268 | SRP_gN *SRP_get_default_gN(const char *id)
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269 | {
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270 | size_t i;
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271 |
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272 | if (id == NULL)
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273 | return knowngN;
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274 | for (i = 0; i < KNOWN_GN_NUMBER; i++) {
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275 | if (strcmp(knowngN[i].id, id) == 0)
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276 | return knowngN + i;
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277 | }
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278 | return NULL;
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279 | }
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280 | #endif
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