/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* lib/kdb/decrypt_key.c */
/*
 * Copyright 1990,1991 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.
 */
/*
 * Copyright (C) 1998 by the FundsXpress, INC.
 *
 * 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 FundsXpress. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  FundsXpress makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#include "k5-int.h"
#include "kdb.h"

/*
 * Decrypt a key from storage in the database.  "eblock" is used
 * to decrypt the key in "in" into "out"; the storage pointed to by "out"
 * is allocated before use.
 */

krb5_error_code
krb5_dbe_def_decrypt_key_data( krb5_context     context,
                               const krb5_keyblock    * mkey,
                               const krb5_key_data    * key_data,
                               krb5_keyblock  * dbkey,
                               krb5_keysalt   * keysalt)
{
    krb5_error_code       retval = 0;
    krb5_int16            tmplen;
    krb5_octet          * ptr;
    krb5_enc_data         cipher;
    krb5_data             plain;

    if (!mkey)
        return KRB5_KDB_BADSTORED_MKEY;
    ptr = key_data->key_data_contents[0];

    if (ptr) {
        krb5_kdb_decode_int16(ptr, tmplen);
        ptr += 2;

        if (tmplen < 0)
            return EINVAL;
        cipher.enctype = ENCTYPE_UNKNOWN;
        cipher.ciphertext.length = key_data->key_data_length[0]-2;
        cipher.ciphertext.data = (char *) ptr;
        plain.length = key_data->key_data_length[0]-2;
        if ((plain.data = malloc(plain.length)) == NULL)
            return(ENOMEM);

        if ((retval = krb5_c_decrypt(context, mkey, 0 /* XXX */, 0,
                                     &cipher, &plain))) {
            free(plain.data);
            return retval;
        }

        /* tmplen is the true length of the key.  plain.data is the
           plaintext data length, but it may be padded, since the
           old-style etypes didn't store the real length.  I can check
           to make sure that there are enough bytes, but I can't do
           any better than that. */

        if ((unsigned int) tmplen >  plain.length) {
            free(plain.data);
            return(KRB5_CRYPTO_INTERNAL);
        }

        dbkey->magic = KV5M_KEYBLOCK;
        dbkey->enctype = key_data->key_data_type[0];
        dbkey->length = tmplen;
        dbkey->contents = (krb5_octet *) plain.data;
    }

    /* Decode salt data */
    if (keysalt) {
        if (key_data->key_data_ver == 2) {
            keysalt->type = key_data->key_data_type[1];
            if ((keysalt->data.length = key_data->key_data_length[1])) {
                if (!(keysalt->data.data=(char *)malloc(keysalt->data.length))){
                    if (key_data->key_data_contents[0]) {
                        free(dbkey->contents);
                        dbkey->contents = 0;
                        dbkey->length = 0;
                    }
                    return ENOMEM;
                }
                memcpy(keysalt->data.data, key_data->key_data_contents[1],
                       (size_t) keysalt->data.length);
            } else
                keysalt->data.data = (char *) NULL;
        } else {
            keysalt->type = KRB5_KDB_SALTTYPE_NORMAL;
            keysalt->data.data = (char *) NULL;
            keysalt->data.length = 0;
        }
    }

    return retval;
}