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annotate nss/lib/freebl/cts.c @ 1:247cffdc9b89

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Add a pesodo config file for inlcude directories and library names
author Andre Heinecke <andre.heinecke@intevation.de>
date Mon, 28 Jul 2014 13:00:06 +0200
parents 1e5118fa0cb1
children
rev   line source
0
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1 /* This Source Code Form is subject to the terms of the Mozilla Public
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2 * License, v. 2.0. If a copy of the MPL was not distributed with this
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3 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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4
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5 #ifdef FREEBL_NO_DEPEND
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6 #include "stubs.h"
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7 #endif
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8 #include "blapit.h"
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9 #include "blapii.h"
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10 #include "cts.h"
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11 #include "secerr.h"
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12
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13 struct CTSContextStr {
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14 freeblCipherFunc cipher;
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15 void *context;
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16 /* iv stores the last ciphertext block of the previous message.
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17 * Only used by decrypt. */
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18 unsigned char iv[MAX_BLOCK_SIZE];
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19 };
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20
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21 CTSContext *
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22 CTS_CreateContext(void *context, freeblCipherFunc cipher,
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23 const unsigned char *iv, unsigned int blocksize)
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24 {
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25 CTSContext *cts;
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26
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27 if (blocksize > MAX_BLOCK_SIZE) {
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28 PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);
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29 return NULL;
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30 }
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31 cts = PORT_ZNew(CTSContext);
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32 if (cts == NULL) {
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33 return NULL;
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34 }
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35 PORT_Memcpy(cts->iv, iv, blocksize);
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36 cts->cipher = cipher;
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37 cts->context = context;
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38 return cts;
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39 }
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40
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41 void
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42 CTS_DestroyContext(CTSContext *cts, PRBool freeit)
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43 {
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44 if (freeit) {
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45 PORT_Free(cts);
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46 }
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47 }
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48
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49 /*
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50 * See addemdum to NIST SP 800-38A
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51 * Generically handle cipher text stealing. Basically this is doing CBC
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52 * operations except someone can pass us a partial block.
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53 *
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54 * Output Order:
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55 * CS-1: C1||C2||C3..Cn-1(could be partial)||Cn (NIST)
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56 * CS-2: pad == 0 C1||C2||C3...Cn-1(is full)||Cn (Schneier)
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57 * CS-2: pad != 0 C1||C2||C3...Cn||Cn-1(is partial)(Schneier)
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58 * CS-3: C1||C2||C3...Cn||Cn-1(could be partial) (Kerberos)
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59 *
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60 * The characteristics of these three options:
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61 * - NIST & Schneier (CS-1 & CS-2) are identical to CBC if there are no
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62 * partial blocks on input.
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63 * - Scheier and Kerberos (CS-2 and CS-3) have no embedded partial blocks,
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64 * which make decoding easier.
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65 * - NIST & Kerberos (CS-1 and CS-3) have consistent block order independent
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66 * of padding.
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67 *
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68 * PKCS #11 did not specify which version to implement, but points to the NIST
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69 * spec, so this code implements CTS-CS-1 from NIST.
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70 *
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71 * To convert the returned buffer to:
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72 * CS-2 (Schneier): do
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73 * unsigned char tmp[MAX_BLOCK_SIZE];
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74 * pad = *outlen % blocksize;
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75 * if (pad) {
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76 * memcpy(tmp, outbuf+*outlen-blocksize, blocksize);
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77 * memcpy(outbuf+*outlen-pad,outbuf+*outlen-blocksize-pad, pad);
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78 * memcpy(outbuf+*outlen-blocksize-pad, tmp, blocksize);
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79 * }
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80 * CS-3 (Kerberos): do
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81 * unsigned char tmp[MAX_BLOCK_SIZE];
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82 * pad = *outlen % blocksize;
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83 * if (pad == 0) {
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84 * pad = blocksize;
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85 * }
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86 * memcpy(tmp, outbuf+*outlen-blocksize, blocksize);
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87 * memcpy(outbuf+*outlen-pad,outbuf+*outlen-blocksize-pad, pad);
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88 * memcpy(outbuf+*outlen-blocksize-pad, tmp, blocksize);
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89 */
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90 SECStatus
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91 CTS_EncryptUpdate(CTSContext *cts, unsigned char *outbuf,
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92 unsigned int *outlen, unsigned int maxout,
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93 const unsigned char *inbuf, unsigned int inlen,
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94 unsigned int blocksize)
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95 {
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96 unsigned char lastBlock[MAX_BLOCK_SIZE];
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97 unsigned int tmp;
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98 int fullblocks;
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99 int written;
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100 SECStatus rv;
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101
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102 if (inlen < blocksize) {
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103 PORT_SetError(SEC_ERROR_INPUT_LEN);
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104 return SECFailure;
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105 }
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106
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107 if (maxout < inlen) {
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108 *outlen = inlen;
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109 PORT_SetError(SEC_ERROR_OUTPUT_LEN);
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110 return SECFailure;
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111 }
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112 fullblocks = (inlen/blocksize)*blocksize;
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113 rv = (*cts->cipher)(cts->context, outbuf, outlen, maxout, inbuf,
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114 fullblocks, blocksize);
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115 if (rv != SECSuccess) {
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116 return SECFailure;
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117 }
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118 *outlen = fullblocks; /* AES low level doesn't set outlen */
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119 inbuf += fullblocks;
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120 inlen -= fullblocks;
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121 if (inlen == 0) {
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122 return SECSuccess;
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123 }
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124 written = *outlen - (blocksize - inlen);
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125 outbuf += written;
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126 maxout -= written;
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127
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128 /*
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129 * here's the CTS magic, we pad our final block with zeros,
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130 * then do a CBC encrypt. CBC will xor our plain text with
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
131 * the previous block (Cn-1), capturing part of that block (Cn-1**) as it
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
132 * xors with the zero pad. We then write this full block, overwritting
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
133 * (Cn-1**) in our buffer. This allows us to have input data == output
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
134 * data since Cn contains enough information to reconver Cn-1** when
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
135 * we decrypt (at the cost of some complexity as you can see in decrypt
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
136 * below */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
137 PORT_Memcpy(lastBlock, inbuf, inlen);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
138 PORT_Memset(lastBlock + inlen, 0, blocksize - inlen);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
139 rv = (*cts->cipher)(cts->context, outbuf, &tmp, maxout, lastBlock,
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
140 blocksize, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
141 PORT_Memset(lastBlock, 0, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
142 if (rv == SECSuccess) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
143 *outlen = written + blocksize;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
144 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
145 return rv;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
146 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
147
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
148
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
149 #define XOR_BLOCK(x,y,count) for(i=0; i < count; i++) x[i] = x[i] ^ y[i]
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
150
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
151 /*
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
152 * See addemdum to NIST SP 800-38A
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
153 * Decrypt, Expect CS-1: input. See the comment on the encrypt side
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
154 * to understand what CS-2 and CS-3 mean.
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
155 *
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
156 * To convert the input buffer to CS-1 from ...
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
157 * CS-2 (Schneier): do
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
158 * unsigned char tmp[MAX_BLOCK_SIZE];
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
159 * pad = inlen % blocksize;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
160 * if (pad) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
161 * memcpy(tmp, inbuf+inlen-blocksize-pad, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
162 * memcpy(inbuf+inlen-blocksize-pad,inbuf+inlen-pad, pad);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
163 * memcpy(inbuf+inlen-blocksize, tmp, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
164 * }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
165 * CS-3 (Kerberos): do
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
166 * unsigned char tmp[MAX_BLOCK_SIZE];
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
167 * pad = inlen % blocksize;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
168 * if (pad == 0) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
169 * pad = blocksize;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
170 * }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
171 * memcpy(tmp, inbuf+inlen-blocksize-pad, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
172 * memcpy(inbuf+inlen-blocksize-pad,inbuf+inlen-pad, pad);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
173 * memcpy(inbuf+inlen-blocksize, tmp, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
174 */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
175 SECStatus
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
176 CTS_DecryptUpdate(CTSContext *cts, unsigned char *outbuf,
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
177 unsigned int *outlen, unsigned int maxout,
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
178 const unsigned char *inbuf, unsigned int inlen,
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
179 unsigned int blocksize)
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
180 {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
181 unsigned char *Pn;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
182 unsigned char Cn_2[MAX_BLOCK_SIZE]; /* block Cn-2 */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
183 unsigned char Cn_1[MAX_BLOCK_SIZE]; /* block Cn-1 */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
184 unsigned char Cn[MAX_BLOCK_SIZE]; /* block Cn */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
185 unsigned char lastBlock[MAX_BLOCK_SIZE];
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
186 const unsigned char *tmp;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
187 unsigned int tmpLen;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
188 int fullblocks, pad;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
189 unsigned int i;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
190 SECStatus rv;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
191
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
192 if (inlen < blocksize) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
193 PORT_SetError(SEC_ERROR_INPUT_LEN);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
194 return SECFailure;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
195 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
196
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
197 if (maxout < inlen) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
198 *outlen = inlen;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
199 PORT_SetError(SEC_ERROR_OUTPUT_LEN);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
200 return SECFailure;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
201 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
202
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
203 fullblocks = (inlen/blocksize)*blocksize;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
204
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
205 /* even though we expect the input to be CS-1, CS-2 is easier to parse,
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
206 * so convert to CS-2 immediately. NOTE: this is the same code as in
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
207 * the comment for encrypt. NOTE2: since we can't modify inbuf unless
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
208 * inbuf and outbuf overlap, just copy inbuf to outbuf and modify it there
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
209 */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
210 pad = inlen - fullblocks;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
211 if (pad != 0) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
212 if (inbuf != outbuf) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
213 memcpy(outbuf, inbuf, inlen);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
214 /* keep the names so we logically know how we are using the
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
215 * buffers */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
216 inbuf = outbuf;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
217 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
218 memcpy(lastBlock, inbuf+inlen-blocksize, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
219 /* we know inbuf == outbuf now, inbuf is declared const and can't
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
220 * be the target, so use outbuf for the target here */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
221 memcpy(outbuf+inlen-pad, inbuf+inlen-blocksize-pad, pad);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
222 memcpy(outbuf+inlen-blocksize-pad, lastBlock, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
223 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
224 /* save the previous to last block so we can undo the misordered
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
225 * chaining */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
226 tmp = (fullblocks < blocksize*2) ? cts->iv :
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
227 inbuf+fullblocks-blocksize*2;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
228 PORT_Memcpy(Cn_2, tmp, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
229 PORT_Memcpy(Cn, inbuf+fullblocks-blocksize, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
230 rv = (*cts->cipher)(cts->context, outbuf, outlen, maxout, inbuf,
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
231 fullblocks, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
232 if (rv != SECSuccess) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
233 return SECFailure;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
234 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
235 *outlen = fullblocks; /* AES low level doesn't set outlen */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
236 inbuf += fullblocks;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
237 inlen -= fullblocks;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
238 if (inlen == 0) {
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
239 return SECSuccess;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
240 }
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
241 outbuf += fullblocks;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
242 maxout -= fullblocks;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
243
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
244 /* recover the stolen text */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
245 PORT_Memset(lastBlock, 0, blocksize);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
246 PORT_Memcpy(lastBlock, inbuf, inlen);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
247 PORT_Memcpy(Cn_1, inbuf, inlen);
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
248 Pn = outbuf-blocksize;
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
249 /* inbuf points to Cn-1* in the input buffer */
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
250 /* NOTE: below there are 2 sections marked "make up for the out of order
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
251 * cbc decryption". You may ask, what is going on here.
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
252 * Short answer: CBC automatically xors the plain text with the previous
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
253 * encrypted block. We are decrypting the last 2 blocks out of order, so
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
254 * we have to 'back out' the decrypt xor and 'add back' the encrypt xor.
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
255 * Long answer: When we encrypted, we encrypted as follows:
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
256 * Pn-2, Pn-1, (Pn || 0), but on decryption we can't
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
257 * decrypt Cn-1 until we decrypt Cn because part of Cn-1 is stored in
1e5118fa0cb1 This is NSS with a Cmake Buildsyste
Andre Heinecke <andre.heinecke@intevation.de>
parents:
diff changeset
258 * Cn (see below). So above we decrypted all the full blocks:
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259 * Cn-2, Cn,
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260 * to get:
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261 * Pn-2, Pn, Except that Pn is not yet corect. On encrypt, we
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262 * xor'd Pn || 0 with Cn-1, but on decrypt we xor'd it with Cn-2
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263 * To recover Pn, we xor the block with Cn-1* || 0 (in last block) and
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264 * Cn-2 to get Pn || Cn-1**. Pn can then be written to the output buffer
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265 * and we can now reunite Cn-1. With the full Cn-1 we can decrypt it,
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266 * but now decrypt is going to xor the decrypted data with Cn instead of
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267 * Cn-2. xoring Cn and Cn-2 restores the original Pn-1 and we can now
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268 * write that oout to the buffer */
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269
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270 /* make up for the out of order CBC decryption */
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271 XOR_BLOCK(lastBlock, Cn_2, blocksize);
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272 XOR_BLOCK(lastBlock, Pn, blocksize);
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273 /* last buf now has Pn || Cn-1**, copy out Pn */
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274 PORT_Memcpy(outbuf, lastBlock, inlen);
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275 *outlen += inlen;
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276 /* copy Cn-1* into last buf to recover Cn-1 */
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277 PORT_Memcpy(lastBlock, Cn_1, inlen);
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278 /* note: because Cn and Cn-1 were out of order, our pointer to Pn also
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279 * points to where Pn-1 needs to reside. From here on out read Pn in
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280 * the code as really Pn-1. */
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281 rv = (*cts->cipher)(cts->context, Pn, &tmpLen, blocksize, lastBlock,
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282 blocksize, blocksize);
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283 if (rv != SECSuccess) {
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284 return SECFailure;
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285 }
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286 /* make up for the out of order CBC decryption */
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287 XOR_BLOCK(Pn, Cn_2, blocksize);
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288 XOR_BLOCK(Pn, Cn, blocksize);
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289 /* reset iv to Cn */
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290 PORT_Memcpy(cts->iv, Cn, blocksize);
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291 /* This makes Cn the last block for the next decrypt operation, which
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292 * matches the encrypt. We don't care about the contexts of last block,
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293 * only the side effect of setting the internal IV */
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294 (void) (*cts->cipher)(cts->context, lastBlock, &tmpLen, blocksize, Cn,
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295 blocksize, blocksize);
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296 /* clear last block. At this point last block contains Pn xor Cn_1 xor
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297 * Cn_2, both of with an attacker would know, so we need to clear this
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298 * buffer out */
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299 PORT_Memset(lastBlock, 0, blocksize);
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300 /* Cn, Cn_1, and Cn_2 have encrypted data, so no need to clear them */
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301 return SECSuccess;
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302 }
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