freebsd-dev/sys/dev/random/random_infra.c

/*-
 * Copyright (c) 2015 Mark R V Murray
 * 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
 *    in this position and unchanged.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/random.h>
#include <sys/sysctl.h>

#if defined(RANDOM_LOADABLE)
#include <sys/lock.h>
#include <sys/sx.h>
#endif

#include <dev/random/randomdev.h>

/* Set up the sysctl root node for the entropy device */
SYSCTL_NODE(_kern, OID_AUTO, random, CTLFLAG_RW, 0,
    "Cryptographically Secure Random Number Generator");
SYSCTL_NODE(_kern_random, OID_AUTO, initial_seeding, CTLFLAG_RW, 0,
    "Initial seeding control and information");

/*
 * N.B., this is a dangerous default, but it matches the behavior prior to
 * r346250 (and, say, OpenBSD -- although they get some guaranteed saved
 * entropy from the prior boot because of their KARL system, on RW media).
 */
bool random_bypass_before_seeding = true;
SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
    bypass_before_seeding, CTLFLAG_RDTUN, &random_bypass_before_seeding,
    0, "If set non-zero, bypass the random device in requests for random "
    "data when the random device is not yet seeded.  This is considered "
    "dangerous.  Ordinarily, the random device will block requests until "
    "it is seeded by sufficient entropy.");

/*
 * This is a read-only diagnostic that reports the combination of the former
 * tunable and actual bypass.  It is intended for programmatic inspection by
 * userspace administrative utilities after boot.
 */
bool read_random_bypassed_before_seeding = false;
SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
    read_random_bypassed_before_seeding, CTLFLAG_RD,
    &read_random_bypassed_before_seeding, 0, "If non-zero, the random device "
    "was bypassed because the 'bypass_before_seeding' knob was enabled and a "
    "request was submitted prior to initial seeding.");

/*
 * This is a read-only diagnostic that reports the combination of the former
 * tunable and actual bypass for arc4random initial seeding.  It is intended
 * for programmatic inspection by userspace administrative utilities after
 * boot.
 */
bool arc4random_bypassed_before_seeding = false;
SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
    arc4random_bypassed_before_seeding, CTLFLAG_RD,
    &arc4random_bypassed_before_seeding, 0, "If non-zero, the random device "
    "was bypassed when initially seeding the kernel arc4random(9), because "
    "the 'bypass_before_seeding' knob was enabled and a request was submitted "
    "prior to initial seeding.");

/*
 * This knob is for users who do not want additional warnings in their logs
 * because they intend to handle bypass by inspecting the status of the
 * diagnostic sysctls.
 */
bool random_bypass_disable_warnings = false;
SYSCTL_BOOL(_kern_random_initial_seeding, OID_AUTO,
    disable_bypass_warnings, CTLFLAG_RDTUN,
    &random_bypass_disable_warnings, 0, "If non-zero, do not log a warning "
    "if the 'bypass_before_seeding' knob is enabled and a request is "
    "submitted prior to initial seeding.");

MALLOC_DEFINE(M_ENTROPY, "entropy", "Entropy harvesting buffers and data structures");

struct sources_head source_list = LIST_HEAD_INITIALIZER(source_list);

#if defined(RANDOM_LOADABLE)
struct random_algorithm *p_random_alg_context = NULL;
#else /* !defined(RANDOM_LOADABLE) */
struct random_algorithm *p_random_alg_context = &random_alg_context;
#endif /* defined(RANDOM_LOADABLE) */

#if defined(RANDOM_LOADABLE)

static void
null_read_random(void *dummy __unused, u_int dummy2 __unused)
{
	panic("%s: no random module is loaded", __func__);
}

static bool
null_is_random_seeded(void)
{
	return (false);
}

struct random_readers {
	int	(*read_random_uio)(struct uio *, bool);
	void	(*read_random)(void *, u_int);
	bool	(*is_random_seeded)(void);
} random_reader_context = {
	(int (*)(struct uio *, bool))nullop,
	null_read_random,
	null_is_random_seeded,
};

struct sx randomdev_config_lock;

static void
random_infra_sysinit(void *dummy __unused)
{

	RANDOM_CONFIG_INIT_LOCK();
}
SYSINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_FIRST, random_infra_sysinit, NULL);

void
random_infra_init(int (*p_random_read_uio)(struct uio *, bool),
    void (*p_random_read)(void *, u_int),
    bool (*p_is_random_seeded)(void))
{

	RANDOM_CONFIG_X_LOCK();
	random_reader_context.read_random_uio = p_random_read_uio;
	random_reader_context.read_random = p_random_read;
	random_reader_context.is_random_seeded = p_is_random_seeded;
	RANDOM_CONFIG_X_UNLOCK();
}

void
random_infra_uninit(void)
{

	RANDOM_CONFIG_X_LOCK();
	random_reader_context.read_random_uio = (int (*)(struct uio *, bool))nullop;
	random_reader_context.read_random = null_read_random;
	random_reader_context.is_random_seeded = null_is_random_seeded;
	RANDOM_CONFIG_X_UNLOCK();
}

static void
random_infra_sysuninit(void *dummy __unused)
{

	RANDOM_CONFIG_DEINIT_LOCK();
}
SYSUNINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_FIRST, random_infra_sysuninit, NULL);

int
read_random_uio(struct uio *uio, bool nonblock)
{
	int retval;

	RANDOM_CONFIG_S_LOCK();
	retval = random_reader_context.read_random_uio(uio, nonblock);
	RANDOM_CONFIG_S_UNLOCK();
	return (retval);
}

void
read_random(void *buf, u_int len)
{

	RANDOM_CONFIG_S_LOCK();
	random_reader_context.read_random(buf, len);
	RANDOM_CONFIG_S_UNLOCK();
}

bool
is_random_seeded(void)
{
	RANDOM_CONFIG_S_LOCK();
	random_reader_context.is_random_seeded();
	RANDOM_CONFIG_S_UNLOCK();
}


#endif /* defined(RANDOM_LOADABLE) */