Mercurial > dropbear

annotate src/encauth/gcm/gcm_add_aad.c @ 195:19e5d79b7190 libtomcrypt

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Cleanup of import of LTC 1.02, still problematic for Dropbear
author Matt Johnston <matt@ucc.asn.au>
date Mon, 09 May 2005 09:33:00 +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_add_aad.c
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14 GCM implementation, Add AAD data to the stream, 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 Add AAD to the GCM state
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22 @param gcm The GCM state
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23 @param adata The additional authentication data to add to the GCM state
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24 @param adatalen The length of the AAD data.
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25 @return CRYPT_OK on success
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26 */
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27 int gcm_add_aad(gcm_state *gcm,
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28 const unsigned char *adata, unsigned long adatalen)
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29 {
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30 unsigned long x, y;
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31 int err;
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32
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33 LTC_ARGCHK(gcm != NULL);
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34 if (adatalen > 0) {
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35 LTC_ARGCHK(adata != NULL);
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36 }
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37
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38 if (gcm->buflen > 16 || gcm->buflen < 0) {
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39 return CRYPT_INVALID_ARG;
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40 }
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41
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42 if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
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43 return err;
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44 }
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45
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46 /* in IV mode? */
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47 if (gcm->mode == GCM_MODE_IV) {
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48 /* let's process the IV */
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49 if (gcm->ivmode || gcm->buflen != 12) {
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50 for (x = 0; x < (unsigned long)gcm->buflen; x++) {
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51 gcm->X[x] ^= gcm->buf[x];
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52 }
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53 if (gcm->buflen) {
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54 gcm->totlen += gcm->buflen * CONST64(8);
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55 gcm_mult_h(gcm, gcm->X);
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56 }
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57
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58 /* mix in the length */
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59 zeromem(gcm->buf, 8);
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60 STORE64H(gcm->totlen, gcm->buf+8);
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61 for (x = 0; x < 16; x++) {
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62 gcm->X[x] ^= gcm->buf[x];
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63 }
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64 gcm_mult_h(gcm, gcm->X);
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65
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66 /* copy counter out */
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67 XMEMCPY(gcm->Y, gcm->X, 16);
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68 zeromem(gcm->X, 16);
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69 } else {
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70 XMEMCPY(gcm->Y, gcm->buf, 12);
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71 gcm->Y[12] = 0;
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72 gcm->Y[13] = 0;
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73 gcm->Y[14] = 0;
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74 gcm->Y[15] = 1;
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75 }
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76 XMEMCPY(gcm->Y_0, gcm->Y, 16);
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77 zeromem(gcm->buf, 16);
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78 gcm->buflen = 0;
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79 gcm->totlen = 0;
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80 gcm->mode = GCM_MODE_AAD;
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81 }
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82
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83 if (gcm->mode != GCM_MODE_AAD || gcm->buflen >= 16) {
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84 return CRYPT_INVALID_ARG;
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85 }
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86
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87 x = 0;
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88 #ifdef LTC_FAST
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89 if (gcm->buflen == 0) {
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90 for (x = 0; x < (adatalen & ~15); x += 16) {
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91 for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
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92 *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&adata[x + y]));
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93 }
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94 gcm_mult_h(gcm, gcm->X);
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95 gcm->totlen += 128;
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96 }
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97 adata += x;
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98 }
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99 #endif
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100
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101
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102 /* start adding AAD data to the state */
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103 for (; x < adatalen; x++) {
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104 gcm->X[gcm->buflen++] ^= *adata++;
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105
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106 if (gcm->buflen == 16) {
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107 /* GF mult it */
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108 gcm_mult_h(gcm, gcm->X);
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109 gcm->buflen = 0;
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110 gcm->totlen += 128;
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111 }
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112 }
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113
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114 return CRYPT_OK;
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115 }
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116 #endif
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117