annotate libtomcrypt/src/encauth/ocb3/ocb3_decrypt_verify_memory.c @ 1520:84578193ef47

draft CHANGES
author Matt Johnston <matt@ucc.asn.au>
date Sun, 18 Feb 2018 23:48:32 +0800
parents 6dba84798cd5
children
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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
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10 /**
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11 @file ocb3_decrypt_verify_memory.c
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12 OCB implementation, helper to decrypt block of memory, by Tom St Denis
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13 */
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14 #include "tomcrypt.h"
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15
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16 #ifdef LTC_OCB3_MODE
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17
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18 /**
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19 Decrypt and compare the tag with OCB
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20 @param cipher The index of the cipher desired
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21 @param key The secret key
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22 @param keylen The length of the secret key (octets)
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23 @param nonce The session nonce (length of the block size of the block cipher)
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24 @param noncelen The length of the nonce (octets)
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25 @param adata The AAD - additional associated data
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26 @param adatalen The length of AAD (octets)
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27 @param ct The ciphertext
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28 @param ctlen The length of the ciphertext (octets)
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29 @param pt [out] The plaintext
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30 @param tag The tag to compare against
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31 @param taglen The length of the tag (octets)
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32 @param stat [out] The result of the tag comparison (1==valid, 0==invalid)
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33 @return CRYPT_OK if successful regardless of the tag comparison
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34 */
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35 int ocb3_decrypt_verify_memory(int cipher,
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36 const unsigned char *key, unsigned long keylen,
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37 const unsigned char *nonce, unsigned long noncelen,
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38 const unsigned char *adata, unsigned long adatalen,
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39 const unsigned char *ct, unsigned long ctlen,
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40 unsigned char *pt,
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41 const unsigned char *tag, unsigned long taglen,
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42 int *stat)
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43 {
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44 int err;
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45 ocb3_state *ocb;
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46 unsigned char *buf;
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47 unsigned long buflen;
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48
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49 LTC_ARGCHK(stat != NULL);
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50
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51 /* default to zero */
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52 *stat = 0;
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53
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54 /* limit taglen */
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55 taglen = MIN(taglen, MAXBLOCKSIZE);
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56
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57 /* allocate memory */
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58 buf = XMALLOC(taglen);
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59 ocb = XMALLOC(sizeof(ocb3_state));
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60 if (ocb == NULL || buf == NULL) {
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61 if (ocb != NULL) {
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62 XFREE(ocb);
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63 }
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64 if (buf != NULL) {
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65 XFREE(buf);
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66 }
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67 return CRYPT_MEM;
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68 }
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69
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70 if ((err = ocb3_init(ocb, cipher, key, keylen, nonce, noncelen, taglen)) != CRYPT_OK) {
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71 goto LBL_ERR;
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72 }
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73
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74 if (adata != NULL || adatalen != 0) {
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75 if ((err = ocb3_add_aad(ocb, adata, adatalen)) != CRYPT_OK) {
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76 goto LBL_ERR;
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77 }
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78 }
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79
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80 if ((err = ocb3_decrypt_last(ocb, ct, ctlen, pt)) != CRYPT_OK) {
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81 goto LBL_ERR;
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82 }
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83
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84 buflen = taglen;
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85 if ((err = ocb3_done(ocb, buf, &buflen)) != CRYPT_OK) {
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86 goto LBL_ERR;
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87 }
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88
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89 /* compare tags */
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90 if (buflen >= taglen && XMEM_NEQ(buf, tag, taglen) == 0) {
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91 *stat = 1;
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92 }
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93
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94 err = CRYPT_OK;
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95
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96 LBL_ERR:
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97 #ifdef LTC_CLEAN_STACK
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98 zeromem(ocb, sizeof(ocb3_state));
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99 #endif
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100
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101 XFREE(ocb);
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102 XFREE(buf);
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103 return err;
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104 }
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105
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106 #endif
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107
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108 /* ref: $Format:%D$ */
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109 /* git commit: $Format:%H$ */
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110 /* commit time: $Format:%ai$ */