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/*
* Copyright (c) 1997 - 2008 Kungliga Tekniska Högskolan
* (Royal Institute of Technology, Stockholm, Sweden).
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "krb5_locl.h"
#undef HEIMDAL_WARN_UNUSED_RESULT_ATTRIBUTE
#define HEIMDAL_WARN_UNUSED_RESULT_ATTRIBUTE
#define ENTROPY_NEEDED 128
static HEIMDAL_MUTEX crypto_mutex = HEIMDAL_MUTEX_INITIALIZER;
static int
seed_something(void)
{
#ifndef NO_RANDFILE
char buf[1024], seedfile[256];
/* If there is a seed file, load it. But such a file cannot be trusted,
so use 0 for the entropy estimate */
if (RAND_file_name(seedfile, sizeof(seedfile))) {
int fd;
fd = open(seedfile, O_RDONLY | O_BINARY | O_CLOEXEC);
if (fd >= 0) {
ssize_t ret;
rk_cloexec(fd);
ret = read(fd, buf, sizeof(buf));
if (ret > 0)
RAND_add(buf, ret, 0.0);
close(fd);
} else
seedfile[0] = '\0';
} else
seedfile[0] = '\0';
#endif
/* Calling RAND_status() will try to use /dev/urandom if it exists so
we do not have to deal with it. */
if (RAND_status() != 1) {
/* TODO: Once a Windows CryptoAPI RAND method is defined, we
can use that and failover to another method. */
}
if (RAND_status() == 1) {
#ifndef NO_RANDFILE
/* Update the seed file */
if (seedfile[0])
RAND_write_file(seedfile);
#endif
return 0;
} else
return -1;
}
/**
* Fill buffer buf with len bytes of PRNG randomness that is ok to use
* for key generation, padding and public diclosing the randomness w/o
* disclosing the randomness source.
*
* This function can fail, and callers must check the return value.
*
* @param buf a buffer to fill with randomness
* @param len length of memory that buf points to.
*
* @return return 0 on success or HEIM_ERR_RANDOM_OFFLINE if the
* funcation failed to initialize the randomness source.
*
* @ingroup krb5_crypto
*/
HEIMDAL_WARN_UNUSED_RESULT_ATTRIBUTE
KRB5_LIB_FUNCTION krb5_error_code KRB5_LIB_CALL
krb5_generate_random(void *buf, size_t len)
{
static int rng_initialized = 0;
int ret;
HEIMDAL_MUTEX_lock(&crypto_mutex);
if (!rng_initialized) {
if (seed_something()) {
HEIMDAL_MUTEX_unlock(&crypto_mutex);
return HEIM_ERR_RANDOM_OFFLINE;
}
rng_initialized = 1;
}
if (RAND_bytes(buf, len) <= 0)
ret = HEIM_ERR_RANDOM_OFFLINE;
else
ret = 0;
HEIMDAL_MUTEX_unlock(&crypto_mutex);
return ret;
}
/**
* Fill buffer buf with len bytes of PRNG randomness that is ok to use
* for key generation, padding and public diclosing the randomness w/o
* disclosing the randomness source.
*
* This function can NOT fail, instead it will abort() and program will crash.
*
* If this function is called after a successful krb5_init_context(),
* the chance of it failing is low due to that krb5_init_context()
* pulls out some random, and quite commonly the randomness sources
* will not fail once it have started to produce good output,
* /dev/urandom behavies that way.
*
* @param buf a buffer to fill with randomness
* @param len length of memory that buf points to.
*
* @ingroup krb5_crypto
*/
KRB5_LIB_FUNCTION void KRB5_LIB_CALL
krb5_generate_random_block(void *buf, size_t len)
{
int ret = krb5_generate_random(buf, len);
if (ret)
krb5_abortx(NULL, "Failed to generate random block");
}
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