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annotate libtomcrypt/src/encauth/ocb3/ocb3_done.c @ 1471:6dba84798cd5

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Update to libtomcrypt 1.18.1, merged with Dropbear changes
author Matt Johnston <matt@ucc.asn.au>
date Fri, 09 Feb 2018 21:44:05 +0800
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1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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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_done.c
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12 OCB implementation, INTERNAL ONLY helper, 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 Finish OCB processing and compute the tag
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20 @param ocb The OCB state
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21 @param tag [out] The destination for the authentication tag
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22 @param taglen [in/out] The max size and resulting size of the authentication tag
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23 @return CRYPT_OK if successful
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24 */
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25 int ocb3_done(ocb3_state *ocb, unsigned char *tag, unsigned long *taglen)
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26 {
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27 unsigned char tmp[MAXBLOCKSIZE];
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28 int err, x;
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29
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30 LTC_ARGCHK(ocb != NULL);
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31 LTC_ARGCHK(tag != NULL);
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32 LTC_ARGCHK(taglen != NULL);
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33 if ((err = cipher_is_valid(ocb->cipher)) != CRYPT_OK) {
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34 goto LBL_ERR;
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35 }
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36
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37 /* check taglen */
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38 if ((int)*taglen < ocb->tag_len) {
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39 *taglen = (unsigned long)ocb->tag_len;
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40 return CRYPT_BUFFER_OVERFLOW;
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41 }
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42
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43 /* finalize AAD processing */
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44
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45 if (ocb->adata_buffer_bytes>0) {
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46 /* Offset_* = Offset_m xor L_* */
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47 ocb3_int_xor_blocks(ocb->aOffset_current, ocb->aOffset_current, ocb->L_star, ocb->block_len);
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48
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49 /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
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50 ocb3_int_xor_blocks(tmp, ocb->adata_buffer, ocb->aOffset_current, ocb->adata_buffer_bytes);
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51 for(x=ocb->adata_buffer_bytes; x<ocb->block_len; x++) {
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52 if (x == ocb->adata_buffer_bytes) {
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53 tmp[x] = 0x80 ^ ocb->aOffset_current[x];
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54 }
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55 else {
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56 tmp[x] = 0x00 ^ ocb->aOffset_current[x];
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57 }
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58 }
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59
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60 /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
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61 if ((err = cipher_descriptor[ocb->cipher].ecb_encrypt(tmp, tmp, &ocb->key)) != CRYPT_OK) {
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62 goto LBL_ERR;
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63 }
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64 ocb3_int_xor_blocks(ocb->aSum_current, ocb->aSum_current, tmp, ocb->block_len);
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65 }
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66
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67 /* finalize TAG computing */
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68
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69 /* at this point ocb->aSum_current = HASH(K, A) */
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70 /* tag = tag ^ HASH(K, A) */
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71 ocb3_int_xor_blocks(tmp, ocb->tag_part, ocb->aSum_current, ocb->block_len);
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72
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73 /* copy tag bytes */
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74 for(x = 0; x < ocb->tag_len; x++) tag[x] = tmp[x];
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75 *taglen = (unsigned long)ocb->tag_len;
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76
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77 err = CRYPT_OK;
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78
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79 LBL_ERR:
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80 #ifdef LTC_CLEAN_STACK
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81 zeromem(tmp, MAXBLOCKSIZE);
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82 zeromem(ocb, sizeof(*ocb));
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83 #endif
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84
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85 return err;
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86 }
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87
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88 #endif
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89
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90 /* ref: $Format:%D$ */
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91 /* git commit: $Format:%H$ */
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92 /* commit time: $Format:%ai$ */