92 lines
3.0 KiB
C
92 lines
3.0 KiB
C
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/****************************************************************************
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* libs/libc/misc/lib_getrandom.c
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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 <sys/random.h>
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#include <fcntl.h>
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#include <unistd.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: getrandom
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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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* flags - Bit mask that can contain zero or more of the ORed values
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* together.
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*
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* Returned Value:
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* On success, getrandom() returns the number of bytes that were copied
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* to the buffer bytes. This may be less than the number of bytes
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* requested via nbytes if either GRND_RANDOM was specified in flags and
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* insufficient entropy was present in the random source or the system
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* call was interrupted by a signal.
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*
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* On error, -1 is returned, and errno is set appropriately.
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*
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****************************************************************************/
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ssize_t getrandom(FAR void *bytes, size_t nbytes, unsigned int flags)
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{
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int oflags = O_RDONLY;
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FAR const char *dev;
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int fd;
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if ((flags & GRND_NONBLOCK) != 0)
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{
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oflags |= O_NONBLOCK;
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}
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if ((flags & GRND_RANDOM) != 0)
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{
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dev = "/dev/random";
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}
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else
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{
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dev = "/dev/urandom";
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}
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fd = open(dev, oflags);
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if (fd < 0)
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{
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return fd;
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}
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nbytes = read(fd, bytes, nbytes);
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close(fd);
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return nbytes;
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}
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