Mercurial > dropbear

annotate src/pk/pkcs1/pkcs_1_oaep_decode.c @ 199:8be64e2c86f4 libtomcrypt

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* SMALL_CODE is now LTC_SMALL_CODE
author Matt Johnston <matt@ucc.asn.au>
date Tue, 10 May 2005 17:02:59 +0000
parents 1c15b283127b
children 39d5d58461d6
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
191
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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3 * LibTomCrypt is a library that provides various cryptographic
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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4 * algorithms in a highly modular and flexible manner.
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5 *
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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6 * The library is free for all purposes without any express
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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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
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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10 */
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11 #include "tomcrypt.h"
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12
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13 /**
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14 @file pkcs_1_oaep_decode.c
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15 OAEP Padding for PKCS #1, Tom St Denis
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16 */
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17
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18 #ifdef PKCS_1
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19
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20 /**
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21 PKCS #1 v2.00 OAEP decode
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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22 @param msg The encoded data to decode
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23 @param msglen The length of the encoded data (octets)
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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24 @param lparam The session or system data (can be NULL)
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25 @param lparamlen The length of the lparam
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26 @param modulus_bitlen The bit length of the RSA modulus
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27 @param hash_idx The index of the hash desired
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28 @param out [out] Destination of decoding
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29 @param outlen [in/out] The max size and resulting size of the decoding
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30 @param res [out] Result of decoding, 1==valid, 0==invalid
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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31 @return CRYPT_OK if successful (even if invalid)
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32 */
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33 int pkcs_1_oaep_decode(const unsigned char *msg, unsigned long msglen,
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34 const unsigned char *lparam, unsigned long lparamlen,
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35 unsigned long modulus_bitlen, int hash_idx,
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36 unsigned char *out, unsigned long *outlen,
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37 int *res)
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38 {
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39 unsigned char *DB, *seed, *mask;
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40 unsigned long hLen, x, y, modulus_len;
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41 int err;
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42
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43 LTC_ARGCHK(msg != NULL);
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44 LTC_ARGCHK(out != NULL);
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45 LTC_ARGCHK(outlen != NULL);
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46 LTC_ARGCHK(res != NULL);
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47
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48 /* default to invalid packet */
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49 *res = 0;
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50
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51 /* test valid hash */
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52 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
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53 return err;
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54 }
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55 hLen = hash_descriptor[hash_idx].hashsize;
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56 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
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57
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58 /* test hash/message size */
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59 if ((2*hLen >= (modulus_len - 2)) || (msglen != modulus_len)) {
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60 return CRYPT_PK_INVALID_SIZE;
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61 }
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62
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63 /* allocate ram for DB/mask/salt of size modulus_len */
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64 DB = XMALLOC(modulus_len);
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65 mask = XMALLOC(modulus_len);
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66 seed = XMALLOC(modulus_len);
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67 if (DB == NULL || mask == NULL || seed == NULL) {
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68 if (DB != NULL) {
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69 XFREE(DB);
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70 }
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71 if (mask != NULL) {
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72 XFREE(mask);
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73 }
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74 if (seed != NULL) {
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75 XFREE(seed);
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76 }
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77 return CRYPT_MEM;
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78 }
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79
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80 /* ok so it's now in the form
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81
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82 0x00 || maskedseed || maskedDB
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83
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84 1 || hLen || modulus_len - hLen - 1
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85
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86 */
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87
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88 /* must have leading 0x00 byte */
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89 if (msg[0] != 0x00) {
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90 err = CRYPT_OK;
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91 goto LBL_ERR;
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92 }
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93
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94 /* now read the masked seed */
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95 for (x = 1, y = 0; y < hLen; y++) {
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96 seed[y] = msg[x++];
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97 }
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98
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99 /* now read the masked DB */
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100 for (y = 0; y < modulus_len - hLen - 1; y++) {
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
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101 DB[y] = msg[x++];
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Matt Johnston <matt@ucc.asn.au>
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102 }
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103
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104 /* compute MGF1 of maskedDB (hLen) */
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105 if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) {
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106 goto LBL_ERR;
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107 }
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108
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109 /* XOR against seed */
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110 for (y = 0; y < hLen; y++) {
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Matt Johnston <matt@ucc.asn.au>
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111 seed[y] ^= mask[y];
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Matt Johnston <matt@ucc.asn.au>
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112 }
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113
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114 /* compute MGF1 of seed (k - hlen - 1) */
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115 if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
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116 goto LBL_ERR;
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117 }
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118
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119 /* xor against DB */
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120 for (y = 0; y < (modulus_len - hLen - 1); y++) {
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121 DB[y] ^= mask[y];
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122 }
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123
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124 /* now DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */
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125
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126 /* compute lhash and store it in seed [reuse temps!] */
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127 x = modulus_len;
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128 if (lparam != NULL) {
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129 if ((err = hash_memory(hash_idx, lparam, lparamlen, seed, &x)) != CRYPT_OK) {
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130 goto LBL_ERR;
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131 }
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132 } else {
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133 /* can't pass hash_memory a NULL so use DB with zero length */
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134 if ((err = hash_memory(hash_idx, DB, 0, seed, &x)) != CRYPT_OK) {
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135 goto LBL_ERR;
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136 }
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137 }
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diff changeset
138
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
139 /* compare the lhash'es */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
140 if (memcmp(seed, DB, hLen) != 0) {
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
141 err = CRYPT_OK;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
142 goto LBL_ERR;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
143 }
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
144
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
145 /* now zeroes before a 0x01 */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
146 for (x = hLen; x < (modulus_len - hLen - 1) && DB[x] == 0x00; x++) {
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
147 /* step... */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
148 }
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
149
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
150 /* error out if wasn't 0x01 */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
151 if (x == (modulus_len - hLen - 1) || DB[x] != 0x01) {
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
152 err = CRYPT_OK;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
153 goto LBL_ERR;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
154 }
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
155
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
156 /* rest is the message (and skip 0x01) */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
157 if ((modulus_len - hLen - 1) - ++x > *outlen) {
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
158 err = CRYPT_BUFFER_OVERFLOW;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
159 goto LBL_ERR;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
160 }
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
161
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
162 /* copy message */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
163 *outlen = (modulus_len - hLen - 1) - x;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
164 for (y = 0; x != (modulus_len - hLen - 1); ) {
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
165 out[y++] = DB[x++];
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
166 }
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
167
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
168 /* valid packet */
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
169 *res = 1;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
170
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
171 err = CRYPT_OK;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
172 LBL_ERR:
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
173 #ifdef LTC_CLEAN_STACK
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
174 zeromem(DB, modulus_len);
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
175 zeromem(seed, modulus_len);
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
176 zeromem(mask, modulus_len);
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
177 #endif
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
178
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
179 XFREE(seed);
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
180 XFREE(mask);
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
181 XFREE(DB);
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
182
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
183 return err;
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
184 }
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
185
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
Matt Johnston <matt@ucc.asn.au>
parents:
diff changeset
186 #endif /* PKCS_1 */