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/*
 * crypto.c :  cryptographic routines
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */

#include "crypto.h"

#ifdef SVN_HAVE_CRYPTO
#include <apr_random.h>
#include <apr_crypto.h>
#endif /* SVN_HAVE_CRYPTO */

#include "svn_types.h"
#include "svn_checksum.h"

#include "svn_private_config.h"
#include "private/svn_atomic.h"


/* 1000 iterations is the recommended minimum, per RFC 2898, section 4.2.  */
#define NUM_ITERATIONS 1000


/* Size (in bytes) of the random data we'll prepend to encrypted data. */
#define RANDOM_PREFIX_LEN 4


/* A structure for containing Subversion's cryptography-related bits
   (so we can avoid passing around APR-isms outside this module). */
struct svn_crypto__ctx_t {
#ifdef SVN_HAVE_CRYPTO
  apr_crypto_t *crypto;  /* APR cryptography context. */

#if 0
  /* ### For now, we will use apr_generate_random_bytes(). If we need
     ### more strength, then we can set this member using
     ### apr_random_standard_new(), then use
     ### apr_generate_random_bytes() to generate entropy for seeding
     ### apr_random_t. See httpd/server/core.c:ap_init_rng()  */
  apr_random_t *rand;
#endif /* 0 */
#else /* SVN_HAVE_CRYPTO */
  int unused_but_required_to_satisfy_c_compilers;
#endif /* SVN_HAVE_CRYPTO */
};



/*** Helper Functions ***/
#ifdef SVN_HAVE_CRYPTO


/* One-time initialization of the cryptography subsystem. */
static volatile svn_atomic_t crypto_init_state = 0;


#define CRYPTO_INIT(scratch_pool) \
  SVN_ERR(svn_atomic__init_once(&crypto_init_state, \
                                crypto_init, NULL, (scratch_pool)))


/* Initialize the APR cryptography subsystem (if available), using
   ANY_POOL's ancestor root pool for the registration of cleanups,
   shutdowns, etc.   */
/* Don't call this function directly!  Use svn_atomic__init_once(). */
static svn_error_t *
crypto_init(void *baton, apr_pool_t *any_pool)
{
  /* NOTE: this function will locate the topmost ancestor of ANY_POOL
     for its cleanup handlers. We don't have to worry about ANY_POOL
     being cleared.  */
  apr_status_t apr_err = apr_crypto_init(any_pool);
  if (apr_err)
    return svn_error_wrap_apr(apr_err,
                              _("Failed to initialize cryptography "
                                "subsystem"));

  return SVN_NO_ERROR;
}