Mercurial > dropbear

annotate libtomcrypt/src/encauth/ocb/ocb_done_decrypt.c @ 994:5c5ade336926

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Prefer stronger algorithms in algorithm negotiation. Prefer diffie-hellman-group14-sha1 (2048 bit) over diffie-hellman-group1-sha1 (1024 bit). Due to meet-in-the-middle attacks the effective key length of three key 3DES is 112 bits. AES is stronger and faster then 3DES. Prefer to delay the start of compression until after authentication has completed. This avoids exposing compression code to attacks from unauthenticated users. (github pull request #9)
author Fedor Brunner <fedor.brunner@azet.sk>
date Fri, 23 Jan 2015 23:00:25 +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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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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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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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 $ */