Mercurial > dropbear

annotate libtomcrypt/src/encauth/ocb/ocb_done_decrypt.c @ 817:a625f9e135a4

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Constant time memcmp for the hmac and password crypt
author Matt Johnston <matt@ucc.asn.au>
date Thu, 03 Oct 2013 22:25:30 +0800
parents 0cbe8f6dbf9e
children f849a5ca2efc
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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.com
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10 */
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11
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12 /**
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13 @file ocb_done_decrypt.c
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14 OCB implementation, terminate decryption, 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 OCB_MODE
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19
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20 /**
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21 Terminate a decrypting OCB state
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22 @param ocb The OCB state
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23 @param ct The ciphertext (if any)
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24 @param ctlen The length of the ciphertext (octets)
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25 @param pt [out] The plaintext
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26 @param tag The authentication tag (to compare against)
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27 @param taglen The length of the authentication tag provided
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28 @param stat [out] The result of the tag comparison
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29 @return CRYPT_OK if the process was successful regardless if the tag is valid
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30 */
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31 int ocb_done_decrypt(ocb_state *ocb,
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32 const unsigned char *ct, unsigned long ctlen,
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33 unsigned char *pt,
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34 const unsigned char *tag, unsigned long taglen, int *stat)
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35 {
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36 int err;
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37 unsigned char *tagbuf;
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38 unsigned long tagbuflen;
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39
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40 LTC_ARGCHK(ocb != NULL);
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41 LTC_ARGCHK(pt != NULL);
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42 LTC_ARGCHK(ct != NULL);
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43 LTC_ARGCHK(tag != NULL);
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44 LTC_ARGCHK(stat != NULL);
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45
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46 /* default to failed */
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47 *stat = 0;
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48
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49 /* allocate memory */
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50 tagbuf = XMALLOC(MAXBLOCKSIZE);
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51 if (tagbuf == NULL) {
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52 return CRYPT_MEM;
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53 }
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54
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55 tagbuflen = MAXBLOCKSIZE;
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56 if ((err = s_ocb_done(ocb, ct, ctlen, pt, tagbuf, &tagbuflen, 1)) != CRYPT_OK) {
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57 goto LBL_ERR;
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58 }
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59
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60 if (taglen <= tagbuflen && XMEMCMP(tagbuf, tag, taglen) == 0) {
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61 *stat = 1;
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62 }
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63
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64 err = CRYPT_OK;
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65 LBL_ERR:
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66 #ifdef LTC_CLEAN_STACK
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67 zeromem(tagbuf, MAXBLOCKSIZE);
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68 #endif
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69
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70 XFREE(tagbuf);
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71
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72 return err;
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73 }
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75 #endif
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78 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_done_decrypt.c,v $ */
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79 /* $Revision: 1.5 $ */
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80 /* $Date: 2006/11/01 09:28:17 $ */