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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 pkcs_1_mgf1.c
     15   The Mask Generation Function (MGF1) for PKCS #1, Tom St Denis
     16 */
     17 
     18 #ifdef PKCS_1
     19 
     20 /**
     21    Perform PKCS #1 MGF1 (internal)
     22    @param seed        The seed for MGF1
     23    @param seedlen     The length of the seed
     24    @param hash_idx    The index of the hash desired
     25    @param mask        [out] The destination
     26    @param masklen     The length of the mask desired
     27    @return CRYPT_OK if successful
     28 */
     29 int pkcs_1_mgf1(int                  hash_idx,
     30                 const unsigned char *seed, unsigned long seedlen,
     31                       unsigned char *mask, unsigned long masklen)
     32 {
     33    unsigned long hLen, x;
     34    ulong32       counter;
     35    int           err;
     36    hash_state    *md;
     37    unsigned char *buf;
     38 
     39    LTC_ARGCHK(seed != NULL);
     40    LTC_ARGCHK(mask != NULL);
     41 
     42    /* ensure valid hash */
     43    if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
     44       return err;
     45    }
     46 
     47    /* get hash output size */
     48    hLen = hash_descriptor[hash_idx].hashsize;
     49 
     50    /* allocate memory */
     51    md  = XMALLOC(sizeof(hash_state));
     52    buf = XMALLOC(hLen);
     53    if (md == NULL || buf == NULL) {
     54       if (md != NULL) {
     55          XFREE(md);
     56       }
     57       if (buf != NULL) {
     58          XFREE(buf);
     59       }
     60       return CRYPT_MEM;
     61    }
     62 
     63    /* start counter */
     64    counter = 0;
     65 
     66    while (masklen > 0) {
     67        /* handle counter */
     68        STORE32H(counter, buf);
     69        ++counter;
     70 
     71        /* get hash of seed || counter */
     72        if ((err = hash_descriptor[hash_idx].init(md)) != CRYPT_OK) {
     73           goto LBL_ERR;
     74        }
     75        if ((err = hash_descriptor[hash_idx].process(md, seed, seedlen)) != CRYPT_OK) {
     76           goto LBL_ERR;
     77        }
     78        if ((err = hash_descriptor[hash_idx].process(md, buf, 4)) != CRYPT_OK) {
     79           goto LBL_ERR;
     80        }
     81        if ((err = hash_descriptor[hash_idx].done(md, buf)) != CRYPT_OK) {
     82           goto LBL_ERR;
     83        }
     84 
     85        /* store it */
     86        for (x = 0; x < hLen && masklen > 0; x++, masklen--) {
     87           *mask++ = buf[x];
     88        }
     89    }
     90 
     91    err = CRYPT_OK;
     92 LBL_ERR:
     93 #ifdef LTC_CLEAN_STACK
     94    zeromem(buf, hLen);
     95    zeromem(md,  sizeof(hash_state));
     96 #endif
     97 
     98    XFREE(buf);
     99    XFREE(md);
    100 
    101    return err;
    102 }
    103 
    104 #endif /* PKCS_1 */
    105 
    106 /* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_mgf1.c,v $ */
    107 /* $Revision: 1.6 $ */
    108 /* $Date: 2006/03/31 14:15:35 $ */
    109