text: /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
  /*
   * lib/crypto/krb/checksum/hmac_md5.c
   *
   * Copyright (C) 2009 by the Massachusetts Institute of Technology.
   * All rights reserved.
   *
   * Export of this software from the United States of America may
   *   require a specific license from the United States Government.
   *   It is the responsibility of any person or organization contemplating
   *   export to obtain such a license before exporting.
   *
   * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
   * distribute this software and its documentation for any purpose and
   * without fee is hereby granted, provided that the above copyright
   * notice appear in all copies and that both that copyright notice and
   * this permission notice appear in supporting documentation, and that
   * the name of M.I.T. not be used in advertising or publicity pertaining
   * to distribution of the software without specific, written prior
   * permission.  Furthermore if you modify this software you must label
   * your software as modified software and not distribute it in such a
   * fashion that it might be confused with the original M.I.T. software.
   * M.I.T. makes no representations about the suitability of
   * this software for any purpose.  It is provided "as is" without express
   * or implied warranty.
   *
   * Microsoft HMAC-MD5 and MD5-HMAC checksums (see RFC 4757):
   *   HMAC(KS, hash(msusage || input))
   * KS is HMAC(key, "signaturekey\0") for HMAC-MD5, or just the key for
   * MD5-HMAC.
   */
  
  #include "k5-int.h"
  #include "cksumtypes.h"
  #include "arcfour.h"
  #include "arcfour-int.h"
  
  krb5_error_code krb5int_hmacmd5_checksum(const struct krb5_cksumtypes *ctp,
                                           krb5_key key, krb5_keyusage usage,
                                           const krb5_crypto_iov *data,
                                           size_t num_data,
                                           krb5_data *output)
  {
      krb5_keyusage ms_usage;
      krb5_error_code ret;
      krb5_keyblock ks, *keyblock;
      krb5_crypto_iov *hash_iov = NULL, iov;
      krb5_data ds = empty_data(), hashval = empty_data();
      char t[4];
  
      if (key == NULL || key->keyblock.length > ctp->hash->blocksize)
          return KRB5_BAD_ENCTYPE;
      if (ctp->ctype == CKSUMTYPE_HMAC_MD5_ARCFOUR) {
  	/* Compute HMAC(key, "signaturekey\0") to get the signing key ks. */
          ret = alloc_data(&ds, ctp->hash->hashsize);
  	if (ret != 0)
  	    goto cleanup;
  
  	iov.flags = KRB5_CRYPTO_TYPE_DATA;
  	iov.data = make_data("signaturekey", 13);
  	ret = krb5int_hmac(ctp->hash, key, &iov, 1, &ds);
  	if (ret)
  	    goto cleanup;
  	ks.length = ds.length;
  	ks.contents = (krb5_octet *) ds.data;
  	keyblock = &ks;
      } else  /* For md5-hmac, just use the key. */
  	keyblock = &key->keyblock;
  
      /* Compute the MD5 value of the input. */
      ms_usage = krb5int_arcfour_translate_usage(usage);
      store_32_le(ms_usage, t);
      hash_iov = k5alloc((num_data + 1) * sizeof(krb5_crypto_iov), &ret);
      if (hash_iov == NULL)
  	goto cleanup;
      hash_iov[0].flags = KRB5_CRYPTO_TYPE_DATA;
      hash_iov[0].data = make_data(t, 4);
      memcpy(hash_iov + 1, data, num_data * sizeof(krb5_crypto_iov));
      ret = alloc_data(&hashval, ctp->hash->hashsize);
      if (ret != 0)
  	goto cleanup;
      ret = ctp->hash->hash(hash_iov, num_data + 1, &hashval);
      if (ret != 0)
  	goto cleanup;
  
      /* Compute HMAC(ks, md5value). */
      iov.flags = KRB5_CRYPTO_TYPE_DATA;
      iov.data = hashval;
      ret = krb5int_hmac_keyblock(ctp->hash, keyblock, &iov, 1, output);
  
  cleanup:
      zapfree(ds.data, ds.length);
      zapfree(hashval.data, hashval.length);
      free(hash_iov);
      return ret;
  }
  