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/* $OpenBSD: getentropy_linux.c,v 1.43.4.1 2017/04/29 18:57:00 beck Exp $ */
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/*
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* Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
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* Copyright (c) 2014 Bob Beck <beck@obtuse.com>
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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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* Emulation of getentropy(2) as documented at:
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* http://man.openbsd.org/getentropy.2
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*/
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#define _POSIX_C_SOURCE 199309L
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#define _GNU_SOURCE 1
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/ioctl.h>
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#include <sys/resource.h>
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#include <sys/syscall.h>
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#ifdef SYS__sysctl
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#include <linux/sysctl.h>
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#endif
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#include <sys/statvfs.h>
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#include <sys/socket.h>
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#include <sys/mount.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <sys/time.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <link.h>
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#include <termios.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <time.h>
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#include <openssl/sha.h>
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#include <linux/types.h>
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#include <linux/random.h>
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#ifdef HAVE_GETAUXVAL
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#include <sys/auxv.h>
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#endif
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#include <sys/vfs.h>
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#define REPEAT 5
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#define min(a, b) (((a) < (b)) ? (a) : (b))
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#define HX(a, b) \
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do { \
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if ((a)) \
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HD(errno); \
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else \
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HD(b); \
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} while (0)
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#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
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#define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
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#define HF(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
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int getentropy(void *buf, size_t len);
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static int gotdata(char *buf, size_t len);
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#ifdef SYS_getrandom
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static int getentropy_getrandom(void *buf, size_t len);
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#endif
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static int getentropy_urandom(void *buf, size_t len);
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#ifdef SYS__sysctl
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static int getentropy_sysctl(void *buf, size_t len);
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#endif
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static int getentropy_fallback(void *buf, size_t len);
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static int getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data);
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int
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getentropy(void *buf, size_t len)
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{
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int ret = -1;
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if (len > 256) {
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errno = EIO;
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return (-1);
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}
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#ifdef SYS_getrandom
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/*
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* Try descriptor-less getrandom(), in non-blocking mode.
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*
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* The design of Linux getrandom is broken. It has an
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* uninitialized phase coupled with blocking behaviour, which
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* is unacceptable from within a library at boot time without
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* possible recovery. See http://bugs.python.org/issue26839#msg267745
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*/
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ret = getentropy_getrandom(buf, len);
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if (ret != -1)
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return (ret);
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#endif
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/*
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* Try to get entropy with /dev/urandom
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*
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* This can fail if the process is inside a chroot or if file
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* descriptors are exhausted.
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*/
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ret = getentropy_urandom(buf, len);
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if (ret != -1)
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return (ret);
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#ifdef SYS__sysctl
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/*
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* Try to use sysctl CTL_KERN, KERN_RANDOM, RANDOM_UUID.
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* sysctl is a failsafe API, so it guarantees a result. This
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* should work inside a chroot, or when file descriptors are
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* exhausted.
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*
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* However this can fail if the Linux kernel removes support
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* for sysctl. Starting in 2007, there have been efforts to
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* deprecate the sysctl API/ABI, and push callers towards use
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* of the chroot-unavailable fd-using /proc mechanism --
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* essentially the same problems as /dev/urandom.
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*
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* Numerous setbacks have been encountered in their deprecation
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* schedule, so as of June 2014 the kernel ABI still exists on
|
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* most Linux architectures. The sysctl() stub in libc is missing
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* on some systems. There are also reports that some kernels
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* spew messages to the console.
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*/
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ret = getentropy_sysctl(buf, len);
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if (ret != -1)
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return (ret);
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#endif /* SYS__sysctl */
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/*
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* Entropy collection via /dev/urandom and sysctl have failed.
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*
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* No other API exists for collecting entropy. See the large
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* comment block above.
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*
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* We have very few options:
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* - Even syslog_r is unsafe to call at this low level, so
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* there is no way to alert the user or program.
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* - Cannot call abort() because some systems have unsafe
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* corefiles.
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* - Could raise(SIGKILL) resulting in silent program termination.
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* - Return EIO, to hint that arc4random's stir function
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* should raise(SIGKILL)
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* - Do the best under the circumstances....
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*
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* This code path exists to bring light to the issue that Linux
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* still does not provide a failsafe API for entropy collection.
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*
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* We hope this demonstrates that Linux should either retain their
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* sysctl ABI, or consider providing a new failsafe API which
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* works in a chroot or when file descriptors are exhausted.
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*/
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#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
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#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
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raise(SIGKILL);
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#endif
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ret = getentropy_fallback(buf, len);
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if (ret != -1)
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return (ret);
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errno = EIO;
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return (ret);
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}
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/*
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* Basic sanity checking; wish we could do better.
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*/
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static int
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gotdata(char *buf, size_t len)
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{
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char any_set = 0;
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size_t i;
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for (i = 0; i < len; ++i)
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any_set |= buf[i];
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if (any_set == 0)
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return (-1);
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return (0);
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}
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#ifdef SYS_getrandom
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static int
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getentropy_getrandom(void *buf, size_t len)
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|
{
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int pre_errno = errno;
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int ret;
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if (len > 256)
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return (-1);
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do {
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ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
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} while (ret == -1 && errno == EINTR);
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if (ret != len)
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return (-1);
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errno = pre_errno;
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return (0);
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}
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#endif
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static int
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getentropy_urandom(void *buf, size_t len)
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{
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struct stat st;
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|
size_t i;
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int fd, cnt, flags;
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|
int save_errno = errno;
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start:
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flags = O_RDONLY;
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#ifdef O_NOFOLLOW
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flags |= O_NOFOLLOW;
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#endif
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#ifdef O_CLOEXEC
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flags |= O_CLOEXEC;
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|
#endif
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|
fd = open("/dev/urandom", flags, 0);
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|
|
if (fd == -1) {
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|
if (errno == EINTR)
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|
goto start;
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|
goto nodevrandom;
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|
}
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|
#ifndef O_CLOEXEC
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|
fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
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|
#endif
|
|
|
|
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|
/* Lightly verify that the device node looks sane */
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|
if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
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|
close(fd);
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|
goto nodevrandom;
|
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|
}
|
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|
if (ioctl(fd, RNDGETENTCNT, &cnt) == -1) {
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|
|
close(fd);
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|
goto nodevrandom;
|
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|
}
|
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|
for (i = 0; i < len; ) {
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|
size_t wanted = len - i;
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|
ssize_t ret = read(fd, (char *)buf + i, wanted);
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|
|
|
|
if (ret == -1) {
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|
|
if (errno == EAGAIN || errno == EINTR)
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|
continue;
|
|
|
close(fd);
|
|
|
goto nodevrandom;
|
|
|
}
|
|
|
i += ret;
|
|
|
}
|
|
|
close(fd);
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|
|
if (gotdata(buf, len) == 0) {
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|
|
errno = save_errno;
|
|
|
return (0); /* satisfied */
|
|
|
}
|
|
|
nodevrandom:
|
|
|
errno = EIO;
|
|
|
return (-1);
|
|
|
}
|
|
|
|
|
|
#ifdef SYS__sysctl
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|
static int
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|
getentropy_sysctl(void *buf, size_t len)
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|
|
{
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|
static int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID };
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|
size_t i;
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|
int save_errno = errno;
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|
|
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|
for (i = 0; i < len; ) {
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|
size_t chunk = min(len - i, 16);
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|
|
|
|
/* SYS__sysctl because some systems already removed sysctl() */
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struct __sysctl_args args = {
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.name = mib,
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.nlen = 3,
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.oldval = (char *)buf + i,
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.oldlenp = &chunk,
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};
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|
if (syscall(SYS__sysctl, &args) != 0)
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|
goto sysctlfailed;
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i += chunk;
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}
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if (gotdata(buf, len) == 0) {
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errno = save_errno;
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|
return (0); /* satisfied */
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|
}
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|
sysctlfailed:
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|
errno = EIO;
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|
return (-1);
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}
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|
#endif /* SYS__sysctl */
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static const int cl[] = {
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CLOCK_REALTIME,
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#ifdef CLOCK_MONOTONIC
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CLOCK_MONOTONIC,
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#endif
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#ifdef CLOCK_MONOTONIC_RAW
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CLOCK_MONOTONIC_RAW,
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#endif
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|
#ifdef CLOCK_TAI
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CLOCK_TAI,
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#endif
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#ifdef CLOCK_VIRTUAL
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CLOCK_VIRTUAL,
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#endif
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|
#ifdef CLOCK_UPTIME
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CLOCK_UPTIME,
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#endif
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#ifdef CLOCK_PROCESS_CPUTIME_ID
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CLOCK_PROCESS_CPUTIME_ID,
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|
#endif
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|
#ifdef CLOCK_THREAD_CPUTIME_ID
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CLOCK_THREAD_CPUTIME_ID,
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#endif
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};
|
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|
|
|
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static int
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getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data)
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|
|
{
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SHA512_CTX *ctx = data;
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|
|
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SHA512_Update(ctx, &info->dlpi_addr, sizeof (info->dlpi_addr));
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|
return (0);
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|
}
|
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|
|
|
|
static int
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getentropy_fallback(void *buf, size_t len)
|
|
|
{
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|
|
uint8_t results[SHA512_DIGEST_LENGTH];
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|
int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat;
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static int cnt;
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|
struct timespec ts;
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|
struct timeval tv;
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|
struct rusage ru;
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|
|
sigset_t sigset;
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|
|
struct stat st;
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|
SHA512_CTX ctx;
|
|
|
static pid_t lastpid;
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|
|
pid_t pid;
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|
size_t i, ii, m;
|
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|
char *p;
|
|
|
|
|
|
pid = getpid();
|
|
|
if (lastpid == pid) {
|
|
|
faster = 1;
|
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|
repeat = 2;
|
|
|
} else {
|
|
|
faster = 0;
|
|
|
lastpid = pid;
|
|
|
repeat = REPEAT;
|
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|
}
|
|
|
for (i = 0; i < len; ) {
|
|
|
int j;
|
|
|
SHA512_Init(&ctx);
|
|
|
for (j = 0; j < repeat; j++) {
|
|
|
HX((e = gettimeofday(&tv, NULL)) == -1, tv);
|
|
|
if (e != -1) {
|
|
|
cnt += (int)tv.tv_sec;
|
|
|
cnt += (int)tv.tv_usec;
|
|
|
}
|
|
|
|
|
|
dl_iterate_phdr(getentropy_phdr, &ctx);
|
|
|
|
|
|
for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
|
|
|
HX(clock_gettime(cl[ii], &ts) == -1, ts);
|
|
|
|
|
|
HX((pid = getpid()) == -1, pid);
|
|
|
HX((pid = getsid(pid)) == -1, pid);
|
|
|
HX((pid = getppid()) == -1, pid);
|
|
|
HX((pid = getpgid(0)) == -1, pid);
|
|
|
HX((e = getpriority(0, 0)) == -1, e);
|
|
|
|
|
|
if (!faster) {
|
|
|
ts.tv_sec = 0;
|
|
|
ts.tv_nsec = 1;
|
|
|
(void) nanosleep(&ts, NULL);
|
|
|
}
|
|
|
|
|
|
HX(sigpending(&sigset) == -1, sigset);
|
|
|
HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
|
|
|
sigset);
|
|
|
|
|
|
HF(getentropy); /* an addr in this library */
|
|
|
HF(printf); /* an addr in libc */
|
|
|
p = (char *)&p;
|
|
|
HD(p); /* an addr on stack */
|
|
|
p = (char *)&errno;
|
|
|
HD(p); /* the addr of errno */
|
|
|
|
|
|
if (i == 0) {
|
|
|
struct sockaddr_storage ss;
|
|
|
struct statvfs stvfs;
|
|
|
struct termios tios;
|
|
|
struct statfs stfs;
|
|
|
socklen_t ssl;
|
|
|
off_t off;
|
|
|
|
|
|
/*
|
|
|
* Prime-sized mappings encourage fragmentation;
|
|
|
* thus exposing some address entropy.
|
|
|
*/
|
|
|
struct mm {
|
|
|
size_t npg;
|
|
|
void *p;
|
|
|
} mm[] = {
|
|
|
{ 17, MAP_FAILED }, { 3, MAP_FAILED },
|
|
|
{ 11, MAP_FAILED }, { 2, MAP_FAILED },
|
|
|
{ 5, MAP_FAILED }, { 3, MAP_FAILED },
|
|
|
{ 7, MAP_FAILED }, { 1, MAP_FAILED },
|
|
|
{ 57, MAP_FAILED }, { 3, MAP_FAILED },
|
|
|
{ 131, MAP_FAILED }, { 1, MAP_FAILED },
|
|
|
};
|
|
|
|
|
|
for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
|
|
|
HX(mm[m].p = mmap(NULL,
|
|
|
mm[m].npg * pgs,
|
|
|
PROT_READ|PROT_WRITE,
|
|
|
MAP_PRIVATE|MAP_ANON, -1,
|
|
|
(off_t)0), mm[m].p);
|
|
|
if (mm[m].p != MAP_FAILED) {
|
|
|
size_t mo;
|
|
|
|
|
|
/* Touch some memory... */
|
|
|
p = mm[m].p;
|
|
|
mo = cnt %
|
|
|
(mm[m].npg * pgs - 1);
|
|
|
p[mo] = 1;
|
|
|
cnt += (int)((long)(mm[m].p)
|
|
|
/ pgs);
|
|
|
}
|
|
|
|
|
|
/* Check cnts and times... */
|
|
|
for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
|
|
|
ii++) {
|
|
|
HX((e = clock_gettime(cl[ii],
|
|
|
&ts)) == -1, ts);
|
|
|
if (e != -1)
|
|
|
cnt += (int)ts.tv_nsec;
|
|
|
}
|
|
|
|
|
|
HX((e = getrusage(RUSAGE_SELF,
|
|
|
&ru)) == -1, ru);
|
|
|
if (e != -1) {
|
|
|
cnt += (int)ru.ru_utime.tv_sec;
|
|
|
cnt += (int)ru.ru_utime.tv_usec;
|
|
|
}
|
|
|
}
|
|
|
|
|
|
for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
|
|
|
if (mm[m].p != MAP_FAILED)
|
|
|
munmap(mm[m].p, mm[m].npg * pgs);
|
|
|
mm[m].p = MAP_FAILED;
|
|
|
}
|
|
|
|
|
|
HX(stat(".", &st) == -1, st);
|
|
|
HX(statvfs(".", &stvfs) == -1, stvfs);
|
|
|
HX(statfs(".", &stfs) == -1, stfs);
|
|
|
|
|
|
HX(stat("/", &st) == -1, st);
|
|
|
HX(statvfs("/", &stvfs) == -1, stvfs);
|
|
|
HX(statfs("/", &stfs) == -1, stfs);
|
|
|
|
|
|
HX((e = fstat(0, &st)) == -1, st);
|
|
|
if (e == -1) {
|
|
|
if (S_ISREG(st.st_mode) ||
|
|
|
S_ISFIFO(st.st_mode) ||
|
|
|
S_ISSOCK(st.st_mode)) {
|
|
|
HX(fstatvfs(0, &stvfs) == -1,
|
|
|
stvfs);
|
|
|
HX(fstatfs(0, &stfs) == -1,
|
|
|
stfs);
|
|
|
HX((off = lseek(0, (off_t)0,
|
|
|
SEEK_CUR)) < 0, off);
|
|
|
}
|
|
|
if (S_ISCHR(st.st_mode)) {
|
|
|
HX(tcgetattr(0, &tios) == -1,
|
|
|
tios);
|
|
|
} else if (S_ISSOCK(st.st_mode)) {
|
|
|
memset(&ss, 0, sizeof ss);
|
|
|
ssl = sizeof(ss);
|
|
|
HX(getpeername(0,
|
|
|
(void *)&ss, &ssl) == -1,
|
|
|
ss);
|
|
|
}
|
|
|
}
|
|
|
|
|
|
HX((e = getrusage(RUSAGE_CHILDREN,
|
|
|
&ru)) == -1, ru);
|
|
|
if (e != -1) {
|
|
|
cnt += (int)ru.ru_utime.tv_sec;
|
|
|
cnt += (int)ru.ru_utime.tv_usec;
|
|
|
}
|
|
|
} else {
|
|
|
/* Subsequent hashes absorb previous result */
|
|
|
HD(results);
|
|
|
}
|
|
|
|
|
|
HX((e = gettimeofday(&tv, NULL)) == -1, tv);
|
|
|
if (e != -1) {
|
|
|
cnt += (int)tv.tv_sec;
|
|
|
cnt += (int)tv.tv_usec;
|
|
|
}
|
|
|
|
|
|
HD(cnt);
|
|
|
}
|
|
|
#ifdef HAVE_GETAUXVAL
|
|
|
#ifdef AT_RANDOM
|
|
|
/* Not as random as you think but we take what we are given */
|
|
|
p = (char *) getauxval(AT_RANDOM);
|
|
|
if (p)
|
|
|
HR(p, 16);
|
|
|
#endif
|
|
|
#ifdef AT_SYSINFO_EHDR
|
|
|
p = (char *) getauxval(AT_SYSINFO_EHDR);
|
|
|
if (p)
|
|
|
HR(p, pgs);
|
|
|
#endif
|
|
|
#ifdef AT_BASE
|
|
|
p = (char *) getauxval(AT_BASE);
|
|
|
if (p)
|
|
|
HD(p);
|
|
|
#endif
|
|
|
#endif
|
|
|
|
|
|
SHA512_Final(results, &ctx);
|
|
|
memcpy((char *)buf + i, results, min(sizeof(results), len - i));
|
|
|
i += min(sizeof(results), len - i);
|
|
|
}
|
|
|
explicit_bzero(&ctx, sizeof ctx);
|
|
|
explicit_bzero(results, sizeof results);
|
|
|
if (gotdata(buf, len) == 0) {
|
|
|
errno = save_errno;
|
|
|
return (0); /* satisfied */
|
|
|
}
|
|
|
errno = EIO;
|
|
|
return (-1);
|
|
|
}
|