Mercurial > dropbear

annotate libtomcrypt/src/modes/xts/xts_decrypt.c @ 1629:258b57b208ae

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Fix for issue successfull login of disabled user (#78) This commit introduces fix for scenario: 1. Root login disabled on dropbear 2. PAM authentication model enabled While login as root user, after prompt for password user is being notified about login failrue, but after second attempt of prompt for password within same session, login becames succesfull. Signed-off-by: Pawel Rapkiewicz <[email protected]>
author vincentto13 <33652988+vincentto13@users.noreply.github.com>
date Wed, 20 Mar 2019 15:03:40 +0100
parents 6dba84798cd5
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 /**
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12 Source donated by Elliptic Semiconductor Inc (www.ellipticsemi.com) to the LibTom Projects
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13 */
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14
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15 #ifdef LTC_XTS_MODE
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16
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17 static int _tweak_uncrypt(const unsigned char *C, unsigned char *P, unsigned char *T, symmetric_xts *xts)
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18 {
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19 unsigned long x;
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20 int err;
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21
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22 /* tweak encrypt block i */
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23 #ifdef LTC_FAST
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24 for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) {
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25 *(LTC_FAST_TYPE_PTR_CAST(&P[x])) = *(LTC_FAST_TYPE_PTR_CAST(&C[x])) ^ *(LTC_FAST_TYPE_PTR_CAST(&T[x]));
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26 }
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27 #else
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28 for (x = 0; x < 16; x++) {
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29 P[x] = C[x] ^ T[x];
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30 }
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31 #endif
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32
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33 err = cipher_descriptor[xts->cipher].ecb_decrypt(P, P, &xts->key1);
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34
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35 #ifdef LTC_FAST
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36 for (x = 0; x < 16; x += sizeof(LTC_FAST_TYPE)) {
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37 *(LTC_FAST_TYPE_PTR_CAST(&P[x])) ^= *(LTC_FAST_TYPE_PTR_CAST(&T[x]));
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38 }
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39 #else
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40 for (x = 0; x < 16; x++) {
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41 P[x] = P[x] ^ T[x];
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42 }
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43 #endif
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44
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45 /* LFSR the tweak */
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46 xts_mult_x(T);
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47
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48 return err;
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49 }
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50
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51 /** XTS Decryption
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52 @param ct [in] Ciphertext
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53 @param ptlen Length of plaintext (and ciphertext)
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54 @param pt [out] Plaintext
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55 @param tweak [in] The 128--bit encryption tweak (e.g. sector number)
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56 @param xts The XTS structure
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57 Returns CRYPT_OK upon success
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58 */
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59 int xts_decrypt(const unsigned char *ct, unsigned long ptlen, unsigned char *pt, unsigned char *tweak,
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60 symmetric_xts *xts)
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61 {
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62 unsigned char PP[16], CC[16], T[16];
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63 unsigned long i, m, mo, lim;
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64 int err;
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65
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66 /* check inputs */
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67 LTC_ARGCHK(pt != NULL);
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68 LTC_ARGCHK(ct != NULL);
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69 LTC_ARGCHK(tweak != NULL);
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70 LTC_ARGCHK(xts != NULL);
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71
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72 /* check if valid */
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73 if ((err = cipher_is_valid(xts->cipher)) != CRYPT_OK) {
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74 return err;
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75 }
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76
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77 /* get number of blocks */
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78 m = ptlen >> 4;
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79 mo = ptlen & 15;
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80
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81 /* must have at least one full block */
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82 if (m == 0) {
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83 return CRYPT_INVALID_ARG;
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84 }
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85
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86 if (mo == 0) {
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87 lim = m;
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88 } else {
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89 lim = m - 1;
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90 }
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91
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92 if (cipher_descriptor[xts->cipher].accel_xts_decrypt && lim > 0) {
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93
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94 /* use accelerated decryption for whole blocks */
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95 if ((err = cipher_descriptor[xts->cipher].accel_xts_decrypt(ct, pt, lim, tweak, &xts->key1, &xts->key2)) !=
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96 CRYPT_OK) {
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97 return err;
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98 }
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99 ct += lim * 16;
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100 pt += lim * 16;
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101
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102 /* tweak is encrypted on output */
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103 XMEMCPY(T, tweak, sizeof(T));
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104 } else {
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105 /* encrypt the tweak */
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106 if ((err = cipher_descriptor[xts->cipher].ecb_encrypt(tweak, T, &xts->key2)) != CRYPT_OK) {
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107 return err;
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108 }
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109
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110 for (i = 0; i < lim; i++) {
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111 if ((err = _tweak_uncrypt(ct, pt, T, xts)) != CRYPT_OK) {
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112 return err;
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113 }
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114 ct += 16;
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115 pt += 16;
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116 }
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117 }
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118
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119 /* if ptlen not divide 16 then */
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120 if (mo > 0) {
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121 XMEMCPY(CC, T, 16);
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122 xts_mult_x(CC);
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123
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124 /* PP = tweak decrypt block m-1 */
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125 if ((err = _tweak_uncrypt(ct, PP, CC, xts)) != CRYPT_OK) {
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126 return err;
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127 }
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128
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129 /* Pm = first ptlen % 16 bytes of PP */
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130 for (i = 0; i < mo; i++) {
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131 CC[i] = ct[16 + i];
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132 pt[16 + i] = PP[i];
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133 }
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134 for (; i < 16; i++) {
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135 CC[i] = PP[i];
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136 }
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137
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138 /* Pm-1 = Tweak uncrypt CC */
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139 if ((err = _tweak_uncrypt(CC, pt, T, xts)) != CRYPT_OK) {
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140 return err;
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141 }
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142 }
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143
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144 /* Decrypt the tweak back */
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145 if ((err = cipher_descriptor[xts->cipher].ecb_decrypt(T, tweak, &xts->key2)) != CRYPT_OK) {
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146 return err;
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147 }
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148
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149 return CRYPT_OK;
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150 }
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151
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152 #endif
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153
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154 /* ref: $Format:%D$ */
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155 /* git commit: $Format:%H$ */
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156 /* commit time: $Format:%ai$ */