Mercurial > dropbear

annotate libtomcrypt/src/encauth/ocb/ocb_decrypt_verify_memory.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
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
285
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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 *
382
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9 * Tom St Denis, [email protected], http://libtomcrypt.com
285
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10 */
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11
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12 /**
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13 @file ocb_decrypt_verify_memory.c
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14 OCB implementation, helper to decrypt block of memory, 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 Decrypt and compare the tag with OCB.
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22 @param cipher The index of the cipher desired
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23 @param key The secret key
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24 @param keylen The length of the secret key (octets)
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25 @param nonce The session nonce (length of the block size of the block cipher)
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26 @param ct The ciphertext
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27 @param ctlen The length of the ciphertext (octets)
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28 @param pt [out] The plaintext
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29 @param tag The tag to compare against
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30 @param taglen The length of the tag (octets)
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31 @param stat [out] The result of the tag comparison (1==valid, 0==invalid)
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32 @return CRYPT_OK if successful regardless of the tag comparison
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33 */
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34 int ocb_decrypt_verify_memory(int cipher,
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35 const unsigned char *key, unsigned long keylen,
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36 const unsigned char *nonce,
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37 const unsigned char *ct, unsigned long ctlen,
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38 unsigned char *pt,
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39 const unsigned char *tag, unsigned long taglen,
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40 int *stat)
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41 {
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42 int err;
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43 ocb_state *ocb;
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44
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45 LTC_ARGCHK(key != NULL);
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46 LTC_ARGCHK(nonce != NULL);
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47 LTC_ARGCHK(pt != NULL);
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48 LTC_ARGCHK(ct != NULL);
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49 LTC_ARGCHK(tag != NULL);
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50 LTC_ARGCHK(stat != NULL);
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51
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52 /* allocate memory */
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53 ocb = XMALLOC(sizeof(ocb_state));
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54 if (ocb == NULL) {
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55 return CRYPT_MEM;
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56 }
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57
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58 if ((err = ocb_init(ocb, cipher, key, keylen, nonce)) != CRYPT_OK) {
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59 goto LBL_ERR;
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60 }
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61
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62 while (ctlen > (unsigned long)ocb->block_len) {
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63 if ((err = ocb_decrypt(ocb, ct, pt)) != CRYPT_OK) {
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64 goto LBL_ERR;
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65 }
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66 ctlen -= ocb->block_len;
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67 pt += ocb->block_len;
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68 ct += ocb->block_len;
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69 }
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70
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71 err = ocb_done_decrypt(ocb, ct, ctlen, pt, tag, taglen, stat);
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72 LBL_ERR:
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73 #ifdef LTC_CLEAN_STACK
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74 zeromem(ocb, sizeof(ocb_state));
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75 #endif
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76
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77 XFREE(ocb);
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78
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79 return err;
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80 }
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81
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82 #endif
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83
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84 /* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_decrypt_verify_memory.c,v $ */
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85 /* $Revision: 1.4 $ */
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86 /* $Date: 2006/03/31 14:15:35 $ */