992c8dded5
by replacing clock_systime_ticks to clock Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
143 lines
4.1 KiB
C
143 lines
4.1 KiB
C
/****************************************************************************
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* libs/libc/stdlib/lib_arc4random.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <errno.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/param.h>
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#include <sys/random.h>
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#include <time.h>
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#include <nuttx/hashtable.h>
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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#if defined(CONFIG_DEV_URANDOM) || defined(CONFIG_DEV_RANDOM)
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static int getrandom_all(FAR void *buf, size_t size, int flags)
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{
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FAR char *tmp = buf;
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while (size > 0)
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{
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ssize_t ret = getrandom(tmp, size, flags);
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if (ret < 0)
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{
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if (get_errno() == EINTR)
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{
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continue;
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}
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return ret;
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}
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tmp += ret;
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size -= ret;
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}
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return 0;
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}
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: arc4random_buf
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*
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* Description:
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* Fill a buffer of arbitrary length with randomness. This is the
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* preferred interface for getting random numbers. The traditional
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* /dev/random approach is susceptible for things like the attacker
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* exhausting file descriptors on purpose.
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*
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* Note that this function cannot fail, other than by asserting.
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*
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* Input Parameters:
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* bytes - Buffer for returned random bytes
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* nbytes - Number of bytes requested.
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void arc4random_buf(FAR void *bytes, size_t nbytes)
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{
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#if defined(CONFIG_DEV_URANDOM) || defined(CONFIG_DEV_RANDOM)
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if (getrandom_all(bytes, nbytes, GRND_RANDOM) >= 0)
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{
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return;
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}
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if (getrandom_all(bytes, nbytes, 0) >= 0)
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{
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return;
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}
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#endif
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/* Fallback to hash of clock_systime_ticks(), minus nbytes to avoid getting
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* same tick count when looping more than once.
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*/
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while (nbytes > 0)
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{
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uint32_t hash = HASH(clock() - nbytes, 32);
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size_t ncopy = MIN(nbytes, sizeof(hash));
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memcpy(bytes, &hash, ncopy);
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nbytes -= ncopy;
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bytes = (FAR uint8_t *)bytes + ncopy;
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}
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}
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/****************************************************************************
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* Name: arc4random
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*
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* Description:
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* Returns a single 32-bit value. This is the preferred interface for
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* getting random numbers. The traditional /dev/random approach is
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* susceptible for things like the attacker exhausting file
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* descriptors on purpose.
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*
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* Note that this function cannot fail, other than by asserting.
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*
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* Returned Value:
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* a random 32-bit value.
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*
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****************************************************************************/
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uint32_t arc4random(void)
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{
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uint32_t ret;
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arc4random_buf(&ret, sizeof(ret));
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return ret;
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}
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