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Commit	Line	Data
	1	/*
	2	* This file is part of DisOrder
	3	* Copyright (C) 2008 Richard Kettlewell
	4	*
	5	* This program is free software: you can redistribute it and/or modify
	6	* it under the terms of the GNU General Public License as published by
	7	* the Free Software Foundation, either version 3 of the License, or
	8	* (at your option) any later version.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	* GNU General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License
	16	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	17	*/
	18
	19	/** @file lib/random.c
	20	* @brief Random number generator
	21	*
	22	*/
	23
	24	#include "common.h"
	25
	26	#include <fcntl.h>
	27	#include <unistd.h>
	28	#include <errno.h>
	29
	30	#include "random.h"
	31	#include "log.h"
	32	#include "salsa208.h"
	33	#include "basen.h"
	34	#include "mem.h"
	35
	36	static int random_count;
	37	static int random_fd = -1;
	38	static salsa208_context random_ctx[1];
	39
	40	/** @brief Rekey the RNG
	41	*
	42	* Resets the RNG's key to a random one read from /dev/urandom
	43	*/
	44	static void random__rekey(void) {
	45	char key[32];
	46	int n;
	47
	48	if(random_fd < 0) {
	49	if((random_fd = open("/dev/urandom", O_RDONLY)) < 0)
	50	disorder_fatal(errno, "opening /dev/urandom");
	51	}
	52	if((n = read(random_fd, key, sizeof key)) < 0)
	53	disorder_fatal(errno, "reading from /dev/urandom");
	54	if((size_t)n < sizeof key)
	55	disorder_fatal(0, "reading from /dev/urandom: short read");
	56	salsa208_setkey(random_ctx, key, sizeof key);
	57	random_count = 256 * 1024 * 1024;
	58	}
	59
	60	/** @brief Get random bytes
	61	* @param ptr Where to put random bytes
	62	* @param bytes How many random bytes to generate
	63	*/
	64	void random_get(void *ptr, size_t bytes) {
	65	if(random_count == 0)
	66	random__rekey();
	67	salsa208_stream(random_ctx, 0, ptr, bytes);
	68	if(bytes > (size_t)random_count)
	69	random_count = 0;
	70	else
	71	random_count -= bytes;
	72	}
	73
	74	/** @brief Return a random ID string */
	75	char *random_id(void) {
	76	uint32_t words[2];
	77	char id[128];
	78
	79	random_get(words, sizeof words);
	80	basen(words, sizeof words / sizeof *words, id, sizeof id, 62);
	81	return xstrdup(id);
	82	}
	83
	84	/*
	85	Local Variables:
	86	c-basic-offset:2
	87	comment-column:40
	88	fill-column:79
	89	indent-tabs-mode:nil
	90	End:
	91	*/