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annotate src/encauth/eax/eax_done.c @ 191:1c15b283127b libtomcrypt-orig

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Import of libtomcrypt 1.02 with manual path rename rearrangement etc
author Matt Johnston <matt@ucc.asn.au>
date Fri, 06 May 2005 13:23:02 +0000
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children 39d5d58461d6
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191
1c15b283127b Import of libtomcrypt 1.02 with manual path rename rearrangement etc
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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 eax_done.c
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14 EAX implementation, terminate session, 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 EAX_MODE
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19
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20 /**
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21 Terminate an EAX session and get the tag.
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22 @param eax The EAX state
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23 @param tag [out] The destination of the authentication tag
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24 @param taglen [in/out] The max length and resulting length of the authentication tag
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25 @return CRYPT_OK if successful
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26 */
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27 int eax_done(eax_state *eax, unsigned char *tag, unsigned long *taglen)
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28 {
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29 int err;
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30 unsigned char *headermac, *ctmac;
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31 unsigned long x, len;
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32
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33 LTC_ARGCHK(eax != NULL);
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34 LTC_ARGCHK(tag != NULL);
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35 LTC_ARGCHK(taglen != NULL);
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36
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37 /* allocate ram */
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38 headermac = XMALLOC(MAXBLOCKSIZE);
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39 ctmac = XMALLOC(MAXBLOCKSIZE);
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40
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41 if (headermac == NULL || ctmac == NULL) {
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42 if (headermac != NULL) {
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43 XFREE(headermac);
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44 }
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45 if (ctmac != NULL) {
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46 XFREE(ctmac);
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47 }
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48 return CRYPT_MEM;
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49 }
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50
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51 /* finish ctomac */
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52 len = MAXBLOCKSIZE;
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53 if ((err = omac_done(&eax->ctomac, ctmac, &len)) != CRYPT_OK) {
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54 goto LBL_ERR;
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55 }
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56
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57 /* finish headeromac */
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58
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59 /* note we specifically don't reset len so the two lens are minimal */
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60
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61 if ((err = omac_done(&eax->headeromac, headermac, &len)) != CRYPT_OK) {
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62 goto LBL_ERR;
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63 }
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64
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65 /* terminate the CTR chain */
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66 if ((err = ctr_done(&eax->ctr)) != CRYPT_OK) {
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67 goto LBL_ERR;
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68 }
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69
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70 /* compute N xor H xor C */
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71 for (x = 0; x < len && x < *taglen; x++) {
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72 tag[x] = eax->N[x] ^ headermac[x] ^ ctmac[x];
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73 }
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74 *taglen = x;
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75
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76 err = CRYPT_OK;
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77 LBL_ERR:
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78 #ifdef LTC_CLEAN_STACK
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79 zeromem(ctmac, MAXBLOCKSIZE);
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80 zeromem(headermac, MAXBLOCKSIZE);
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81 zeromem(eax, sizeof(*eax));
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82 #endif
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83
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84 XFREE(ctmac);
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85 XFREE(headermac);
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86
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87 return err;
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88 }
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89
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90 #endif