c2ca066705
We have to bootstrap arc4random.c, so guard the FenestrasX code to avoid using it on Linux/macOS. Reviewed By: cem Differential Revision: https://reviews.freebsd.org/D26738
151 lines
4.1 KiB
C
151 lines
4.1 KiB
C
/* $OpenBSD: arc4random.h,v 1.4 2015/01/15 06:57:18 deraadt Exp $ */
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/*
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* Copyright (c) 1996, David Mazieres <dm@uun.org>
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* Copyright (c) 2008, Damien Miller <djm@openbsd.org>
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* Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
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* Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* $FreeBSD$
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*/
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/*
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* Stub functions for portability.
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*/
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#include <sys/elf.h>
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#include <sys/endian.h>
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#include <sys/mman.h>
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#if ARC4RANDOM_FXRNG != 0
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#include <sys/time.h> /* for sys/vdso.h only. */
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#include <sys/vdso.h>
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#include <machine/atomic.h>
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#endif
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#include <err.h>
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#include <errno.h>
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#include <signal.h>
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#include <stdbool.h>
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#include <stdint.h>
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#if ARC4RANDOM_FXRNG != 0
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/*
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* The kernel root seed version is a 64-bit counter, but we truncate it to a
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* 32-bit value in userspace for the convenience of 32-bit platforms. 32-bit
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* rollover is not possible with the current reseed interval (1 hour at limit)
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* without dynamic addition of new random devices (which also force a reseed in
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* the FXRNG design). We don't have any dynamic device mechanism at this
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* time, and anyway something else is very wrong if billions of new devices are
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* being added.
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*
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* As is, it takes roughly 456,000 years of runtime to overflow the 32-bit
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* version.
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*/
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#define fxrng_load_acq_generation(x) atomic_load_acq_32(x)
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static struct vdso_fxrng_generation_1 *vdso_fxrngp;
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#endif
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static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
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#define _ARC4_LOCK() \
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do { \
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if (__isthreaded) \
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_pthread_mutex_lock(&arc4random_mtx); \
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} while (0)
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#define _ARC4_UNLOCK() \
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do { \
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if (__isthreaded) \
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_pthread_mutex_unlock(&arc4random_mtx); \
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} while (0)
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static inline void
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_getentropy_fail(void)
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{
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raise(SIGKILL);
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}
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static inline void
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_rs_initialize_fxrng(void)
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{
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#if ARC4RANDOM_FXRNG != 0
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struct vdso_fxrng_generation_1 *fxrngp;
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int error;
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error = _elf_aux_info(AT_FXRNG, &fxrngp, sizeof(fxrngp));
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if (error != 0) {
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/*
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* New userspace on an old or !RANDOM_FENESTRASX kernel; or an
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* arch that does not have a VDSO page.
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*/
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return;
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}
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/* Old userspace on newer kernel. */
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if (fxrngp->fx_vdso_version != VDSO_FXRNG_VER_1)
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return;
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vdso_fxrngp = fxrngp;
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#endif
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}
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static inline int
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_rs_allocate(struct _rs **rsp, struct _rsx **rsxp)
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{
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struct {
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struct _rs rs;
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struct _rsx rsx;
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} *p;
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if ((p = mmap(NULL, sizeof(*p), PROT_READ|PROT_WRITE,
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MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
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return (-1);
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/* Allow bootstrapping arc4random.c on Linux/macOS */
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#ifdef INHERIT_ZERO
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if (minherit(p, sizeof(*p), INHERIT_ZERO) == -1) {
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munmap(p, sizeof(*p));
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return (-1);
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}
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#endif
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_rs_initialize_fxrng();
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*rsp = &p->rs;
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*rsxp = &p->rsx;
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return (0);
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}
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/*
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* This isn't only detecting fork. We're also using the existing callback from
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* _rs_stir_if_needed() to force arc4random(3) to reseed if the fenestrasX root
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* seed version has changed. (That is, the root random(4) has reseeded from
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* pooled entropy.)
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*/
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static inline void
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_rs_forkdetect(void)
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{
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/* Detect fork (minherit(2) INHERIT_ZERO). */
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if (__predict_false(rs == NULL || rsx == NULL))
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return;
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#if ARC4RANDOM_FXRNG != 0
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/* If present, detect kernel FenestrasX seed version change. */
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if (vdso_fxrngp == NULL)
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return;
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if (__predict_true(rsx->rs_seed_generation ==
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fxrng_load_acq_generation(&vdso_fxrngp->fx_generation32)))
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return;
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#endif
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/* Invalidate rs_buf to force "stir" (reseed). */
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memset(rs, 0, sizeof(*rs));
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}
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