Mercurial > dropbear

annotate src/encauth/eax/eax_decrypt_verify_memory.c @ 199:8be64e2c86f4 libtomcrypt

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* SMALL_CODE is now LTC_SMALL_CODE
author Matt Johnston <matt@ucc.asn.au>
date Tue, 10 May 2005 17:02:59 +0000
parents 1c15b283127b
children 39d5d58461d6
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
191
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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_decrypt_verify_memory.c
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14 EAX implementation, 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 EAX_MODE
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19
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20 /**
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21 Decrypt a block of memory and verify the provided MAC tag with EAX
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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 key (octets)
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25 @param nonce The nonce data (use once) for the session
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26 @param noncelen The length of the nonce data.
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27 @param header The session header data
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28 @param headerlen The length of the header (octets)
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29 @param ct The ciphertext
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30 @param ctlen The length of the ciphertext (octets)
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31 @param pt [out] The plaintext
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32 @param tag The authentication tag provided by the encoder
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33 @param taglen [in/out] The length of the tag (octets)
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34 @param stat [out] The result of the decryption (1==valid tag, 0==invalid)
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35 @return CRYPT_OK if successful regardless of the resulting tag comparison
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36 */
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37 int eax_decrypt_verify_memory(int cipher,
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38 const unsigned char *key, unsigned long keylen,
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39 const unsigned char *nonce, unsigned long noncelen,
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40 const unsigned char *header, unsigned long headerlen,
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41 const unsigned char *ct, unsigned long ctlen,
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42 unsigned char *pt,
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43 unsigned char *tag, unsigned long taglen,
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44 int *stat)
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45 {
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46 int err;
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47 eax_state *eax;
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48 unsigned char *buf;
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49 unsigned long buflen;
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50
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51 LTC_ARGCHK(stat != NULL);
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52 LTC_ARGCHK(key != NULL);
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53 LTC_ARGCHK(pt != NULL);
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54 LTC_ARGCHK(ct != NULL);
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55 LTC_ARGCHK(tag != NULL);
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56
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57 /* default to zero */
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58 *stat = 0;
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59
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60 /* allocate ram */
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61 buf = XMALLOC(taglen);
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62 eax = XMALLOC(sizeof(*eax));
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63 if (eax == NULL || buf == NULL) {
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64 if (eax != NULL) {
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65 XFREE(eax);
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66 }
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67 if (buf != NULL) {
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68 XFREE(buf);
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69 }
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70 return CRYPT_MEM;
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71 }
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72
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73 if ((err = eax_init(eax, cipher, key, keylen, nonce, noncelen, header, headerlen)) != CRYPT_OK) {
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74 goto LBL_ERR;
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75 }
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76
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77 if ((err = eax_decrypt(eax, ct, pt, ctlen)) != CRYPT_OK) {
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78 goto LBL_ERR;
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79 }
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80
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81 buflen = taglen;
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82 if ((err = eax_done(eax, buf, &buflen)) != CRYPT_OK) {
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83 goto LBL_ERR;
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84 }
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85
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86 /* compare tags */
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87 if (buflen >= taglen && memcmp(buf, tag, taglen) == 0) {
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88 *stat = 1;
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89 }
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90
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91 err = CRYPT_OK;
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92 LBL_ERR:
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93 #ifdef LTC_CLEAN_STACK
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94 zeromem(buf, taglen);
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95 zeromem(eax, sizeof(*eax));
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96 #endif
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97
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98 XFREE(eax);
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99 XFREE(buf);
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100
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101 return err;
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102 }
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103
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104 #endif