Mercurial > dropbear

annotate src/encauth/gcm/gcm_process.c @ 192:9cc34777b479 libtomcrypt

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propagate from branch 'au.asn.ucc.matt.ltc-orig' (head 9ba8f01f44320e9cb9f19881105ae84f84a43ea9) to branch 'au.asn.ucc.matt.dropbear.ltc' (head dbf51c569bc34956ad948e4cc87a0eeb2170b768)
author Matt Johnston <matt@ucc.asn.au>
date Sun, 08 May 2005 06:36:47 +0000
parents 1c15b283127b
children 39d5d58461d6
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191
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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 * Tom St Denis, [email protected], http://libtomcrypt.org
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10 */
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11
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12 /**
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13 @file gcm_process.c
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14 GCM implementation, process message data, by Tom St Denis
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15 */
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16 #include "tomcrypt.h"
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17
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18 #ifdef GCM_MODE
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19
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20 /**
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21 Process plaintext/ciphertext through GCM
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22 @param gcm The GCM state
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23 @param pt The plaintext
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24 @param ptlen The plaintext length (ciphertext length is the same)
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25 @param ct The ciphertext
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26 @param direction Encrypt or Decrypt mode (GCM_ENCRYPT or GCM_DECRYPT)
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27 @return CRYPT_OK on success
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28 */
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29 int gcm_process(gcm_state *gcm,
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30 unsigned char *pt, unsigned long ptlen,
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31 unsigned char *ct,
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32 int direction)
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33 {
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34 unsigned long x, y;
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35 unsigned char b;
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36 int err;
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37
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38 LTC_ARGCHK(gcm != NULL);
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39 if (ptlen > 0) {
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40 LTC_ARGCHK(pt != NULL);
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41 LTC_ARGCHK(ct != NULL);
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42 }
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43
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44 if (gcm->buflen > 16 || gcm->buflen < 0) {
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45 return CRYPT_INVALID_ARG;
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46 }
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47
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48 if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
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49 return err;
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50 }
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51
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52 /* in AAD mode? */
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53 if (gcm->mode == GCM_MODE_AAD) {
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54 /* let's process the AAD */
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55 if (gcm->buflen) {
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56 gcm->totlen += gcm->buflen * CONST64(8);
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57 gcm_mult_h(gcm, gcm->X);
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58 }
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59
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60 /* increment counter */
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61 for (y = 15; y >= 12; y--) {
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62 if (++gcm->Y[y]) { break; }
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63 }
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64 /* encrypt the counter */
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65 cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K);
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66
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67 gcm->buflen = 0;
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68 gcm->mode = GCM_MODE_TEXT;
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69 }
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70
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71 if (gcm->mode != GCM_MODE_TEXT) {
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72 return CRYPT_INVALID_ARG;
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73 }
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74
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75 x = 0;
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76 #ifdef LTC_FAST
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77 if (gcm->buflen == 0) {
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78 if (direction == GCM_ENCRYPT) {
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79 for (x = 0; x < (ptlen & ~15); x += 16) {
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80 /* ctr encrypt */
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81 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
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82 *((LTC_FAST_TYPE*)(&ct[x + y])) = *((LTC_FAST_TYPE*)(&pt[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y]));
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83 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y]));
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84 }
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85 /* GMAC it */
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86 gcm->pttotlen += 128;
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87 gcm_mult_h(gcm, gcm->X);
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88 /* increment counter */
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89 for (y = 15; y >= 12; y--) {
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90 if (++gcm->Y[y]) { break; }
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91 }
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92 cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K);
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93 }
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94 } else {
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95 for (x = 0; x < (ptlen & ~15); x += 16) {
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96 /* ctr encrypt */
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97 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
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98 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y]));
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99 *((LTC_FAST_TYPE*)(&pt[x + y])) = *((LTC_FAST_TYPE*)(&ct[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y]));
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100 }
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101 /* GMAC it */
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102 gcm->pttotlen += 128;
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103 gcm_mult_h(gcm, gcm->X);
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104 /* increment counter */
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105 for (y = 15; y >= 12; y--) {
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106 if (++gcm->Y[y]) { break; }
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107 }
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108 cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K);
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109 }
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110 }
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111 }
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112 #endif
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113
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114 /* process text */
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115 for (; x < ptlen; x++) {
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116 if (gcm->buflen == 16) {
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117 gcm->pttotlen += 128;
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118 gcm_mult_h(gcm, gcm->X);
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119
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120 /* increment counter */
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121 for (y = 15; y >= 12; y--) {
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122 if (++gcm->Y[y]) { break; }
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123 }
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124 cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K);
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125 gcm->buflen = 0;
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126 }
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127
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128 if (direction == GCM_ENCRYPT) {
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129 b = ct[x] = pt[x] ^ gcm->buf[gcm->buflen];
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130 } else {
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131 b = ct[x];
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132 pt[x] = ct[x] ^ gcm->buf[gcm->buflen];
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133 }
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134 gcm->X[gcm->buflen++] ^= b;
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135 }
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136
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137 return CRYPT_OK;
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138 }
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139
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140
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141
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142 #endif
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143