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      1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
      2  *
      3  * LibTomCrypt is a library that provides various cryptographic
      4  * algorithms in a highly modular and flexible manner.
      5  *
      6  * The library is free for all purposes without any express
      7  * guarantee it works.
      8  *
      9  * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com
     10  */
     11 #include "tomcrypt.h"
     12 
     13 /**
     14   @file hmac_file.c
     15   HMAC support, process a file, Tom St Denis/Dobes Vandermeer
     16 */
     17 
     18 #ifdef LTC_HMAC
     19 
     20 /**
     21   HMAC a file
     22   @param hash     The index of the hash you wish to use
     23   @param fname    The name of the file you wish to HMAC
     24   @param key      The secret key
     25   @param keylen   The length of the secret key
     26   @param out      [out] The HMAC authentication tag
     27   @param outlen   [in/out]  The max size and resulting size of the authentication tag
     28   @return CRYPT_OK if successful, CRYPT_NOP if file support has been disabled
     29 */
     30 int hmac_file(int hash, const char *fname,
     31               const unsigned char *key, unsigned long keylen,
     32                     unsigned char *out, unsigned long *outlen)
     33 {
     34 #ifdef LTC_NO_FILE
     35     return CRYPT_NOP;
     36 #else
     37    hmac_state hmac;
     38    FILE *in;
     39    unsigned char buf[512];
     40    size_t x;
     41    int err;
     42 
     43    LTC_ARGCHK(fname  != NULL);
     44    LTC_ARGCHK(key    != NULL);
     45    LTC_ARGCHK(out    != NULL);
     46    LTC_ARGCHK(outlen != NULL);
     47 
     48    if((err = hash_is_valid(hash)) != CRYPT_OK) {
     49        return err;
     50    }
     51 
     52    if ((err = hmac_init(&hmac, hash, key, keylen)) != CRYPT_OK) {
     53        return err;
     54    }
     55 
     56    in = fopen(fname, "rb");
     57    if (in == NULL) {
     58       return CRYPT_FILE_NOTFOUND;
     59    }
     60 
     61    /* process the file contents */
     62    do {
     63       x = fread(buf, 1, sizeof(buf), in);
     64       if ((err = hmac_process(&hmac, buf, (unsigned long)x)) != CRYPT_OK) {
     65          /* we don't trap this error since we're already returning an error! */
     66          fclose(in);
     67          return err;
     68       }
     69    } while (x == sizeof(buf));
     70 
     71    if (fclose(in) != 0) {
     72       return CRYPT_ERROR;
     73    }
     74 
     75    /* get final hmac */
     76    if ((err = hmac_done(&hmac, out, outlen)) != CRYPT_OK) {
     77       return err;
     78    }
     79 
     80 #ifdef LTC_CLEAN_STACK
     81    /* clear memory */
     82    zeromem(buf, sizeof(buf));
     83 #endif
     84    return CRYPT_OK;
     85 #endif
     86 }
     87 
     88 #endif
     89 
     90 
     91 /* $Source: /cvs/libtom/libtomcrypt/src/mac/hmac/hmac_file.c,v $ */
     92 /* $Revision: 1.5 $ */
     93 /* $Date: 2006/11/03 00:39:49 $ */
     94