330 lines
8.9 KiB
C
330 lines
8.9 KiB
C
/****************************************************************************
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* drivers/crypto/dev_urandom.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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/* This random number generator is simple, fast and portable.
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* Ref: https://en.wikipedia.org/wiki/Xorshift
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*/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <sys/param.h>
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#include <stdbool.h>
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#include <stdlib.h>
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#include <string.h>
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#include <poll.h>
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#include <errno.h>
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#include <assert.h>
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#include <nuttx/lib/lib.h>
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#include <nuttx/lib/xorshift128.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/drivers/drivers.h>
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#include <nuttx/random.h>
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#if defined(CONFIG_DEV_URANDOM) && !defined(CONFIG_DEV_URANDOM_ARCH)
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#if !defined(CONFIG_DEV_URANDOM_CONGRUENTIAL) && \
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!defined(CONFIG_DEV_URANDOM_XORSHIFT128) && \
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!defined(CONFIG_DEV_URANDOM_RANDOM_POOL)
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# ifdef CONFIG_CRYPTO_RANDOM_POOL
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# define CONFIG_DEV_URANDOM_RANDOM_POOL 1
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# else
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# define CONFIG_DEV_URANDOM_XORSHIFT128 1
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# endif
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#endif
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#ifdef CONFIG_DEV_URANDOM_XORSHIFT128
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# define PRNG() do_xorshift128()
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#elif defined(CONFIG_DEV_URANDOM_CONGRUENTIAL)
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# define PRNG() do_congruential()
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#endif
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/****************************************************************************
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* Private Types
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****************************************************************************/
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union xorshift128_state_u
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{
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struct xorshift128_state_s state;
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uint8_t u[16];
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};
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static ssize_t devurand_read(FAR struct file *filep, FAR char *buffer,
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size_t buflen);
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static ssize_t devurand_write(FAR struct file *filep, FAR const char *buffer,
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size_t buflen);
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static int devurand_poll(FAR struct file *filep, FAR struct pollfd *fds,
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bool setup);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations g_urand_fops =
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{
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NULL, /* open */
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NULL, /* close */
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devurand_read, /* read */
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devurand_write, /* write */
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NULL, /* seek */
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NULL, /* ioctl */
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NULL, /* mmap */
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NULL, /* truncate */
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devurand_poll /* poll */
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};
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#ifdef CONFIG_DEV_URANDOM_XORSHIFT128
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static union xorshift128_state_u g_prng;
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#endif
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: do_xorshift128
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****************************************************************************/
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#ifdef CONFIG_DEV_URANDOM_XORSHIFT128
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static inline uint32_t do_xorshift128(void)
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{
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return xorshift128(&g_prng.state);
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}
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#endif
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/****************************************************************************
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* Name: do_congruential
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****************************************************************************/
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#ifdef CONFIG_DEV_URANDOM_CONGRUENTIAL
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static inline uint32_t do_congruential(void)
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{
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/* REVISIT: We could probably generate a 32-bit value with a single
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* call to nrand().
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*/
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return (uint32_t)nrand(65536L) << (uint32_t)nrand(65536L);
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}
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#endif
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/****************************************************************************
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* Name: devurand_read
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****************************************************************************/
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static ssize_t devurand_read(FAR struct file *filep, FAR char *buffer,
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size_t len)
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{
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#ifdef CONFIG_DEV_URANDOM_RANDOM_POOL
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if (len > 0)
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{
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arc4random_buf(buffer, len);
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}
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#else
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size_t n;
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uint32_t rnd;
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n = len;
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/* Align buffer pointer to 4-byte boundary */
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if (((uintptr_t)buffer & 0x03) != 0)
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{
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/* Generate a pseudo random number */
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rnd = PRNG();
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while (((uintptr_t)buffer & 0x03) != 0)
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{
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if (n <= 0)
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{
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return len;
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}
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*buffer++ = rnd & 0xff;
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rnd >>= 8;
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--n;
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}
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}
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/* Stuff buffer with PRNGs 4 bytes at a time */
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while (n >= 4)
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{
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*(uint32_t *)buffer = PRNG();
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buffer += 4;
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n -= 4;
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}
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/* Stuff remaining 1, 2, or 3 bytes */
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if (n > 0)
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{
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/* Generate a pseudo random number */
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rnd = PRNG();
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do
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{
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*buffer++ = rnd & 0xff;
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rnd >>= 8;
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}
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while (--n > 0);
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}
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#endif /* CONFIG_DEV_URANDOM_RANDOM_POOL */
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return len;
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}
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/****************************************************************************
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* Name: devurand_write
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****************************************************************************/
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static ssize_t devurand_write(FAR struct file *filep, FAR const char *buffer,
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size_t len)
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{
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/* Write can be used to re-seed the PRNG state. */
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#ifdef CONFIG_DEV_URANDOM_CONGRUENTIAL
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unsigned int seed = 0;
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len = MIN(len, sizeof(unsigned int));
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memcpy(&seed, buffer, len);
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srand(seed);
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return len;
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#elif defined(CONFIG_DEV_URANDOM_RANDOM_POOL)
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const unsigned int alignmask = sizeof(uint32_t) - 1;
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const size_t initlen = len;
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uint32_t tmp = 0;
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size_t currlen;
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if (!len)
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{
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return 0;
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}
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/* Seed entropy pool with data from user. */
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if ((uintptr_t)buffer & alignmask)
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{
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/* Make unaligned input aligned. */
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currlen = MIN(sizeof(uint32_t) - ((uintptr_t)buffer & alignmask), len);
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memcpy(&tmp, buffer, currlen);
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up_rngaddint(RND_SRC_SW, tmp);
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len -= currlen;
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buffer += currlen;
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}
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if (len >= sizeof(uint32_t))
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{
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/* Handle bulk aligned, word-sized data. */
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DEBUGASSERT(((uintptr_t)buffer & alignmask) == 0);
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currlen = len / sizeof(uint32_t);
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up_rngaddentropy(RND_SRC_SW, (FAR uint32_t *)buffer, currlen);
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buffer += currlen * sizeof(uint32_t);
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len %= sizeof(uint32_t);
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}
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if (len > 0)
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{
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/* Handle trailing bytes. */
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DEBUGASSERT(len < sizeof(uint32_t));
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memcpy(&tmp, buffer, len);
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up_rngaddint(RND_SRC_SW, tmp);
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}
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/* Reseeding of random number generator from entropy pool. */
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up_rngreseed();
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return initlen;
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#else
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len = MIN(len, sizeof(g_prng.u));
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memcpy(&g_prng.u, buffer, len);
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return len;
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#endif
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}
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/****************************************************************************
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* Name: devurand_poll
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****************************************************************************/
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static int devurand_poll(FAR struct file *filep, FAR struct pollfd *fds,
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bool setup)
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{
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if (setup)
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{
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poll_notify(&fds, 1, POLLIN | POLLOUT);
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}
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return OK;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: devurandom_register
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*
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* Description:
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* Register /dev/urandom
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*
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****************************************************************************/
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void devurandom_register(void)
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{
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/* Seed the PRNG */
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#ifdef CONFIG_DEV_URANDOM_CONGRUENTIAL
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srand(10197);
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#elif defined(CONFIG_DEV_URANDOM_RANDOM_POOL)
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up_randompool_initialize();
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#else
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g_prng.state.w = 97;
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g_prng.state.x = 101;
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g_prng.state.y = g_prng.state.w << 17;
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g_prng.state.z = g_prng.state.x << 25;
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#endif
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register_driver("/dev/urandom", &g_urand_fops, 0666, NULL);
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}
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#endif /* CONFIG_DEV_URANDOM && CONFIG_DEV_URANDOM_ARCH */
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