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 | /* ====================================================================
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11 | * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
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12 | * Portions of this software developed by SUN MICROSYSTEMS, INC.,
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13 | * and contributed to the OpenSSL project.
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14 | */
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15 |
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16 | #include <openssl/err.h>
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17 | #include <openssl/symhacks.h>
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18 |
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19 | #include "ec_lcl.h"
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20 |
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21 | int ec_GFp_simple_set_compressed_coordinates(const EC_GROUP *group,
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22 | EC_POINT *point,
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23 | const BIGNUM *x_, int y_bit,
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24 | BN_CTX *ctx)
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25 | {
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26 | BN_CTX *new_ctx = NULL;
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27 | BIGNUM *tmp1, *tmp2, *x, *y;
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28 | int ret = 0;
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29 |
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30 | /* clear error queue */
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31 | ERR_clear_error();
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32 |
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33 | if (ctx == NULL) {
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34 | ctx = new_ctx = BN_CTX_new();
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35 | if (ctx == NULL)
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36 | return 0;
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37 | }
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38 |
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39 | y_bit = (y_bit != 0);
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40 |
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41 | BN_CTX_start(ctx);
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42 | tmp1 = BN_CTX_get(ctx);
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43 | tmp2 = BN_CTX_get(ctx);
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44 | x = BN_CTX_get(ctx);
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45 | y = BN_CTX_get(ctx);
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46 | if (y == NULL)
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47 | goto err;
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48 |
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49 | /*-
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50 | * Recover y. We have a Weierstrass equation
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51 | * y^2 = x^3 + a*x + b,
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52 | * so y is one of the square roots of x^3 + a*x + b.
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53 | */
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54 |
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55 | /* tmp1 := x^3 */
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56 | if (!BN_nnmod(x, x_, group->field, ctx))
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57 | goto err;
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58 | if (group->meth->field_decode == 0) {
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59 | /* field_{sqr,mul} work on standard representation */
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60 | if (!group->meth->field_sqr(group, tmp2, x_, ctx))
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61 | goto err;
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62 | if (!group->meth->field_mul(group, tmp1, tmp2, x_, ctx))
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63 | goto err;
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64 | } else {
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65 | if (!BN_mod_sqr(tmp2, x_, group->field, ctx))
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66 | goto err;
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67 | if (!BN_mod_mul(tmp1, tmp2, x_, group->field, ctx))
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68 | goto err;
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69 | }
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70 |
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71 | /* tmp1 := tmp1 + a*x */
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72 | if (group->a_is_minus3) {
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73 | if (!BN_mod_lshift1_quick(tmp2, x, group->field))
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74 | goto err;
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75 | if (!BN_mod_add_quick(tmp2, tmp2, x, group->field))
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76 | goto err;
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77 | if (!BN_mod_sub_quick(tmp1, tmp1, tmp2, group->field))
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78 | goto err;
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79 | } else {
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80 | if (group->meth->field_decode) {
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81 | if (!group->meth->field_decode(group, tmp2, group->a, ctx))
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82 | goto err;
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83 | if (!BN_mod_mul(tmp2, tmp2, x, group->field, ctx))
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84 | goto err;
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85 | } else {
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86 | /* field_mul works on standard representation */
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87 | if (!group->meth->field_mul(group, tmp2, group->a, x, ctx))
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88 | goto err;
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89 | }
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90 |
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91 | if (!BN_mod_add_quick(tmp1, tmp1, tmp2, group->field))
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92 | goto err;
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93 | }
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94 |
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95 | /* tmp1 := tmp1 + b */
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96 | if (group->meth->field_decode) {
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97 | if (!group->meth->field_decode(group, tmp2, group->b, ctx))
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98 | goto err;
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99 | if (!BN_mod_add_quick(tmp1, tmp1, tmp2, group->field))
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100 | goto err;
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101 | } else {
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102 | if (!BN_mod_add_quick(tmp1, tmp1, group->b, group->field))
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103 | goto err;
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104 | }
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105 |
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106 | if (!BN_mod_sqrt(y, tmp1, group->field, ctx)) {
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107 | unsigned long err = ERR_peek_last_error();
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108 |
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109 | if (ERR_GET_LIB(err) == ERR_LIB_BN
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110 | && ERR_GET_REASON(err) == BN_R_NOT_A_SQUARE) {
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111 | ERR_clear_error();
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112 | ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES,
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113 | EC_R_INVALID_COMPRESSED_POINT);
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114 | } else
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115 | ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES,
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116 | ERR_R_BN_LIB);
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117 | goto err;
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118 | }
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119 |
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120 | if (y_bit != BN_is_odd(y)) {
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121 | if (BN_is_zero(y)) {
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122 | int kron;
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123 |
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124 | kron = BN_kronecker(x, group->field, ctx);
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125 | if (kron == -2)
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126 | goto err;
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127 |
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128 | if (kron == 1)
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129 | ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES,
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130 | EC_R_INVALID_COMPRESSION_BIT);
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131 | else
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132 | /*
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133 | * BN_mod_sqrt() should have cought this error (not a square)
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134 | */
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135 | ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES,
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136 | EC_R_INVALID_COMPRESSED_POINT);
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137 | goto err;
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138 | }
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139 | if (!BN_usub(y, group->field, y))
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140 | goto err;
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141 | }
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142 | if (y_bit != BN_is_odd(y)) {
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143 | ECerr(EC_F_EC_GFP_SIMPLE_SET_COMPRESSED_COORDINATES,
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144 | ERR_R_INTERNAL_ERROR);
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145 | goto err;
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146 | }
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147 |
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148 | if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx))
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149 | goto err;
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150 |
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151 | ret = 1;
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152 |
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153 | err:
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154 | BN_CTX_end(ctx);
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155 | BN_CTX_free(new_ctx);
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156 | return ret;
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157 | }
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158 |
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159 | size_t ec_GFp_simple_point2oct(const EC_GROUP *group, const EC_POINT *point,
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160 | point_conversion_form_t form,
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161 | unsigned char *buf, size_t len, BN_CTX *ctx)
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162 | {
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163 | size_t ret;
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164 | BN_CTX *new_ctx = NULL;
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165 | int used_ctx = 0;
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166 | BIGNUM *x, *y;
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167 | size_t field_len, i, skip;
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168 |
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169 | if ((form != POINT_CONVERSION_COMPRESSED)
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170 | && (form != POINT_CONVERSION_UNCOMPRESSED)
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171 | && (form != POINT_CONVERSION_HYBRID)) {
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172 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_INVALID_FORM);
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173 | goto err;
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174 | }
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175 |
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176 | if (EC_POINT_is_at_infinity(group, point)) {
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177 | /* encodes to a single 0 octet */
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178 | if (buf != NULL) {
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179 | if (len < 1) {
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180 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
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181 | return 0;
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182 | }
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183 | buf[0] = 0;
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184 | }
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185 | return 1;
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186 | }
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187 |
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188 | /* ret := required output buffer length */
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189 | field_len = BN_num_bytes(group->field);
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190 | ret =
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191 | (form ==
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192 | POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
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193 |
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194 | /* if 'buf' is NULL, just return required length */
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195 | if (buf != NULL) {
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196 | if (len < ret) {
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197 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, EC_R_BUFFER_TOO_SMALL);
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198 | goto err;
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199 | }
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200 |
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201 | if (ctx == NULL) {
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202 | ctx = new_ctx = BN_CTX_new();
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203 | if (ctx == NULL)
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204 | return 0;
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205 | }
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206 |
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207 | BN_CTX_start(ctx);
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208 | used_ctx = 1;
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209 | x = BN_CTX_get(ctx);
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210 | y = BN_CTX_get(ctx);
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211 | if (y == NULL)
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212 | goto err;
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213 |
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214 | if (!EC_POINT_get_affine_coordinates_GFp(group, point, x, y, ctx))
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215 | goto err;
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216 |
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217 | if ((form == POINT_CONVERSION_COMPRESSED
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218 | || form == POINT_CONVERSION_HYBRID) && BN_is_odd(y))
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219 | buf[0] = form + 1;
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220 | else
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221 | buf[0] = form;
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222 |
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223 | i = 1;
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224 |
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225 | skip = field_len - BN_num_bytes(x);
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226 | if (skip > field_len) {
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227 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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228 | goto err;
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229 | }
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230 | while (skip > 0) {
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231 | buf[i++] = 0;
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232 | skip--;
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233 | }
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234 | skip = BN_bn2bin(x, buf + i);
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235 | i += skip;
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236 | if (i != 1 + field_len) {
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237 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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238 | goto err;
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239 | }
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240 |
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241 | if (form == POINT_CONVERSION_UNCOMPRESSED
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242 | || form == POINT_CONVERSION_HYBRID) {
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243 | skip = field_len - BN_num_bytes(y);
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244 | if (skip > field_len) {
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245 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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246 | goto err;
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247 | }
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248 | while (skip > 0) {
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249 | buf[i++] = 0;
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250 | skip--;
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251 | }
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252 | skip = BN_bn2bin(y, buf + i);
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253 | i += skip;
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254 | }
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255 |
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256 | if (i != ret) {
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257 | ECerr(EC_F_EC_GFP_SIMPLE_POINT2OCT, ERR_R_INTERNAL_ERROR);
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258 | goto err;
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259 | }
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260 | }
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261 |
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262 | if (used_ctx)
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263 | BN_CTX_end(ctx);
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264 | BN_CTX_free(new_ctx);
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265 | return ret;
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266 |
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267 | err:
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268 | if (used_ctx)
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269 | BN_CTX_end(ctx);
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270 | BN_CTX_free(new_ctx);
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271 | return 0;
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272 | }
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273 |
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274 | int ec_GFp_simple_oct2point(const EC_GROUP *group, EC_POINT *point,
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275 | const unsigned char *buf, size_t len, BN_CTX *ctx)
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276 | {
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277 | point_conversion_form_t form;
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278 | int y_bit;
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279 | BN_CTX *new_ctx = NULL;
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280 | BIGNUM *x, *y;
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281 | size_t field_len, enc_len;
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282 | int ret = 0;
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283 |
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284 | if (len == 0) {
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285 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_BUFFER_TOO_SMALL);
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286 | return 0;
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287 | }
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288 | form = buf[0];
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289 | y_bit = form & 1;
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290 | form = form & ~1U;
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291 | if ((form != 0) && (form != POINT_CONVERSION_COMPRESSED)
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292 | && (form != POINT_CONVERSION_UNCOMPRESSED)
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293 | && (form != POINT_CONVERSION_HYBRID)) {
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294 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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295 | return 0;
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296 | }
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297 | if ((form == 0 || form == POINT_CONVERSION_UNCOMPRESSED) && y_bit) {
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298 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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299 | return 0;
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300 | }
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301 |
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302 | if (form == 0) {
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303 | if (len != 1) {
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304 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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305 | return 0;
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306 | }
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307 |
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308 | return EC_POINT_set_to_infinity(group, point);
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309 | }
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310 |
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311 | field_len = BN_num_bytes(group->field);
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312 | enc_len =
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313 | (form ==
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314 | POINT_CONVERSION_COMPRESSED) ? 1 + field_len : 1 + 2 * field_len;
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315 |
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316 | if (len != enc_len) {
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317 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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318 | return 0;
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319 | }
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320 |
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321 | if (ctx == NULL) {
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322 | ctx = new_ctx = BN_CTX_new();
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323 | if (ctx == NULL)
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324 | return 0;
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325 | }
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326 |
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327 | BN_CTX_start(ctx);
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328 | x = BN_CTX_get(ctx);
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329 | y = BN_CTX_get(ctx);
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330 | if (y == NULL)
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331 | goto err;
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332 |
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333 | if (!BN_bin2bn(buf + 1, field_len, x))
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334 | goto err;
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335 | if (BN_ucmp(x, group->field) >= 0) {
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336 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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337 | goto err;
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338 | }
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339 |
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340 | if (form == POINT_CONVERSION_COMPRESSED) {
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341 | if (!EC_POINT_set_compressed_coordinates_GFp
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342 | (group, point, x, y_bit, ctx))
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343 | goto err;
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344 | } else {
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345 | if (!BN_bin2bn(buf + 1 + field_len, field_len, y))
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346 | goto err;
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347 | if (BN_ucmp(y, group->field) >= 0) {
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348 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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349 | goto err;
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350 | }
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351 | if (form == POINT_CONVERSION_HYBRID) {
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352 | if (y_bit != BN_is_odd(y)) {
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353 | ECerr(EC_F_EC_GFP_SIMPLE_OCT2POINT, EC_R_INVALID_ENCODING);
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354 | goto err;
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355 | }
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356 | }
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357 |
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358 | /*
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359 | * EC_POINT_set_affine_coordinates_GFp is responsible for checking that
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360 | * the point is on the curve.
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361 | */
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362 | if (!EC_POINT_set_affine_coordinates_GFp(group, point, x, y, ctx))
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363 | goto err;
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364 | }
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365 |
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366 | ret = 1;
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367 |
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368 | err:
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369 | BN_CTX_end(ctx);
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370 | BN_CTX_free(new_ctx);
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371 | return ret;
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372 | }
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