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3
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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 /* EAX Implementation by Tom St Denis */ |
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13 #include "mycrypt.h" |
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14 |
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15 #ifdef EAX_MODE |
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16 |
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17 int eax_done(eax_state *eax, unsigned char *tag, unsigned long *taglen) |
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18 { |
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19 int err; |
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143
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20 unsigned char *headermac, *ctmac; |
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3
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21 unsigned long x, len; |
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22 |
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23 _ARGCHK(eax != NULL); |
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24 _ARGCHK(tag != NULL); |
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25 _ARGCHK(taglen != NULL); |
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26 |
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143
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27 /* allocate ram */ |
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28 headermac = XMALLOC(MAXBLOCKSIZE); |
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29 ctmac = XMALLOC(MAXBLOCKSIZE); |
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30 |
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31 if (headermac == NULL || ctmac == NULL) { |
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32 if (headermac != NULL) { |
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33 XFREE(headermac); |
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34 } |
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35 if (ctmac != NULL) { |
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36 XFREE(ctmac); |
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37 } |
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38 return CRYPT_MEM; |
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39 } |
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40 |
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3
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41 /* finish ctomac */ |
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143
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42 len = MAXBLOCKSIZE; |
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3
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43 if ((err = omac_done(&eax->ctomac, ctmac, &len)) != CRYPT_OK) { |
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143
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44 goto __ERR; |
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3
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45 } |
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46 |
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47 /* finish headeromac */ |
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48 |
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49 /* note we specifically don't reset len so the two lens are minimal */ |
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50 |
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51 if ((err = omac_done(&eax->headeromac, headermac, &len)) != CRYPT_OK) { |
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143
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52 goto __ERR; |
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3
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53 } |
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54 |
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55 /* compute N xor H xor C */ |
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56 for (x = 0; x < len && x < *taglen; x++) { |
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57 tag[x] = eax->N[x] ^ headermac[x] ^ ctmac[x]; |
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58 } |
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59 *taglen = x; |
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60 |
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143
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61 err = CRYPT_OK; |
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62 __ERR: |
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3
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63 #ifdef CLEAN_STACK |
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143
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64 zeromem(ctmac, MAXBLOCKSIZE); |
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65 zeromem(headermac, MAXBLOCKSIZE); |
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66 zeromem(eax, sizeof(*eax)); |
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3
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67 #endif |
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68 |
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143
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69 XFREE(ctmac); |
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70 XFREE(headermac); |
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71 |
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72 return err; |
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3
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73 } |
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74 |
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75 #endif |
