418 lines
10 KiB
C
Executable File
418 lines
10 KiB
C
Executable File
/* $OpenBSD: getentropy_osx.c,v 1.13 2020/05/17 14:44:20 deraadt 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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#include <TargetConditionals.h>
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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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#include <sys/sysctl.h>
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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 <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 <mach/mach_time.h>
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#include <mach/mach_host.h>
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#include <mach/host_info.h>
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#if TARGET_OS_OSX
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#include <sys/socketvar.h>
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#include <sys/vmmeter.h>
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#endif
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#include <netinet/in.h>
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#include <netinet/tcp.h>
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#if TARGET_OS_OSX
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#include <netinet/udp.h>
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#include <netinet/ip_var.h>
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#include <netinet/tcp_var.h>
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#include <netinet/udp_var.h>
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#endif
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#include <CommonCrypto/CommonDigest.h>
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#define SHA512_Update(a, b, c) (CC_SHA512_Update((a), (b), (c)))
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#define SHA512_Init(xxx) (CC_SHA512_Init((xxx)))
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#define SHA512_Final(xxx, yyy) (CC_SHA512_Final((xxx), (yyy)))
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#define SHA512_CTX CC_SHA512_CTX
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#define SHA512_DIGEST_LENGTH CC_SHA512_DIGEST_LENGTH
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#define REPEAT 5
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#define MINIMUM(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 getentropy_urandom(void *buf, size_t len);
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static int getentropy_fallback(void *buf, size_t len);
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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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/*
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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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/*
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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, and we have
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* no failsafe way to get it on OSX that is not sensitive
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* to resource exhaustion.
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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 OSX
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* does not provide a failsafe API for entropy collection.
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*
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* We hope this demonstrates that OSX should consider
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* providing a new failsafe API which works in a chroot or
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* 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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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, 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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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;
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close(fd);
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goto nodevrandom;
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}
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i += ret;
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}
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close(fd);
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errno = save_errno;
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return (0); /* satisfied */
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nodevrandom:
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errno = EIO;
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return (-1);
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}
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#if TARGET_OS_OSX
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static int tcpmib[] = { CTL_NET, AF_INET, IPPROTO_TCP, TCPCTL_STATS };
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static int udpmib[] = { CTL_NET, AF_INET, IPPROTO_UDP, UDPCTL_STATS };
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static int ipmib[] = { CTL_NET, AF_INET, IPPROTO_IP, IPCTL_STATS };
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#endif
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static int kmib[] = { CTL_KERN, KERN_USRSTACK };
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static int hwmib[] = { CTL_HW, HW_USERMEM };
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static int
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getentropy_fallback(void *buf, size_t len)
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{
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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;
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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;
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#if TARGET_OS_OSX
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struct tcpstat tcpstat;
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struct udpstat udpstat;
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struct ipstat ipstat;
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#endif
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u_int64_t mach_time;
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unsigned int idata;
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void *addr;
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pid = getpid();
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if (lastpid == pid) {
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faster = 1;
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repeat = 2;
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} else {
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faster = 0;
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lastpid = pid;
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repeat = REPEAT;
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}
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for (i = 0; i < len; ) {
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int j;
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SHA512_Init(&ctx);
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for (j = 0; j < repeat; j++) {
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HX((e = gettimeofday(&tv, NULL)) == -1, tv);
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if (e != -1) {
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cnt += (int)tv.tv_sec;
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cnt += (int)tv.tv_usec;
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}
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mach_time = mach_absolute_time();
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HD(mach_time);
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ii = sizeof(addr);
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HX(sysctl(kmib, sizeof(kmib) / sizeof(kmib[0]),
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&addr, &ii, NULL, 0) == -1, addr);
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ii = sizeof(idata);
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HX(sysctl(hwmib, sizeof(hwmib) / sizeof(hwmib[0]),
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&idata, &ii, NULL, 0) == -1, idata);
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#if TARGET_OS_OSX
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ii = sizeof(tcpstat);
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HX(sysctl(tcpmib, sizeof(tcpmib) / sizeof(tcpmib[0]),
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&tcpstat, &ii, NULL, 0) == -1, tcpstat);
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ii = sizeof(udpstat);
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HX(sysctl(udpmib, sizeof(udpmib) / sizeof(udpmib[0]),
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&udpstat, &ii, NULL, 0) == -1, udpstat);
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ii = sizeof(ipstat);
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HX(sysctl(ipmib, sizeof(ipmib) / sizeof(ipmib[0]),
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&ipstat, &ii, NULL, 0) == -1, ipstat);
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#endif
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HX((pid = getpid()) == -1, pid);
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HX((pid = getsid(pid)) == -1, pid);
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HX((pid = getppid()) == -1, pid);
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HX((pid = getpgid(0)) == -1, pid);
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HX((e = getpriority(0, 0)) == -1, e);
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if (!faster) {
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ts.tv_sec = 0;
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ts.tv_nsec = 1;
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(void) nanosleep(&ts, NULL);
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}
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HX(sigpending(&sigset) == -1, sigset);
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HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
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sigset);
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HF(getentropy); /* an addr in this library */
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HF(printf); /* an addr in libc */
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p = (char *)&p;
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HD(p); /* an addr on stack */
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p = (char *)&errno;
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HD(p); /* the addr of errno */
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if (i == 0) {
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struct sockaddr_storage ss;
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struct statvfs stvfs;
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struct termios tios;
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struct statfs stfs;
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socklen_t ssl;
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off_t off;
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/*
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* Prime-sized mappings encourage fragmentation;
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* thus exposing some address entropy.
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*/
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struct mm {
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size_t npg;
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void *p;
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} mm[] = {
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{ 17, MAP_FAILED }, { 3, MAP_FAILED },
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{ 11, MAP_FAILED }, { 2, MAP_FAILED },
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{ 5, MAP_FAILED }, { 3, MAP_FAILED },
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{ 7, MAP_FAILED }, { 1, MAP_FAILED },
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{ 57, MAP_FAILED }, { 3, MAP_FAILED },
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{ 131, MAP_FAILED }, { 1, MAP_FAILED },
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};
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for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
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HX(mm[m].p = mmap(NULL,
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mm[m].npg * pgs,
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PROT_READ|PROT_WRITE,
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MAP_PRIVATE|MAP_ANON, -1,
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(off_t)0), mm[m].p);
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if (mm[m].p != MAP_FAILED) {
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size_t mo;
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/* Touch some memory... */
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p = mm[m].p;
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mo = cnt %
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(mm[m].npg * pgs - 1);
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p[mo] = 1;
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cnt += (int)((long)(mm[m].p)
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/ pgs);
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}
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/* Check cnts and times... */
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mach_time = mach_absolute_time();
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HD(mach_time);
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cnt += (int)mach_time;
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HX((e = getrusage(RUSAGE_SELF,
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&ru)) == -1, ru);
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if (e != -1) {
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cnt += (int)ru.ru_utime.tv_sec;
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cnt += (int)ru.ru_utime.tv_usec;
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}
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}
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for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
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if (mm[m].p != MAP_FAILED)
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munmap(mm[m].p, mm[m].npg * pgs);
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mm[m].p = MAP_FAILED;
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}
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HX(stat(".", &st) == -1, st);
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HX(statvfs(".", &stvfs) == -1, stvfs);
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HX(statfs(".", &stfs) == -1, stfs);
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HX(stat("/", &st) == -1, st);
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HX(statvfs("/", &stvfs) == -1, stvfs);
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HX(statfs("/", &stfs) == -1, stfs);
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HX((e = fstat(0, &st)) == -1, st);
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if (e == -1) {
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if (S_ISREG(st.st_mode) ||
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S_ISFIFO(st.st_mode) ||
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S_ISSOCK(st.st_mode)) {
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HX(fstatvfs(0, &stvfs) == -1,
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stvfs);
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HX(fstatfs(0, &stfs) == -1,
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stfs);
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HX((off = lseek(0, (off_t)0,
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SEEK_CUR)) < 0, off);
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}
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if (S_ISCHR(st.st_mode)) {
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HX(tcgetattr(0, &tios) == -1,
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tios);
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} else if (S_ISSOCK(st.st_mode)) {
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memset(&ss, 0, sizeof ss);
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ssl = sizeof(ss);
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HX(getpeername(0,
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(void *)&ss, &ssl) == -1,
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ss);
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}
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}
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HX((e = getrusage(RUSAGE_CHILDREN,
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&ru)) == -1, ru);
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if (e != -1) {
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cnt += (int)ru.ru_utime.tv_sec;
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cnt += (int)ru.ru_utime.tv_usec;
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}
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} else {
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/* Subsequent hashes absorb previous result */
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HD(results);
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}
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HX((e = gettimeofday(&tv, NULL)) == -1, tv);
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if (e != -1) {
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cnt += (int)tv.tv_sec;
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cnt += (int)tv.tv_usec;
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}
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HD(cnt);
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}
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SHA512_Final(results, &ctx);
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memcpy((char *)buf + i, results, MINIMUM(sizeof(results), len - i));
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i += MINIMUM(sizeof(results), len - i);
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}
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explicit_bzero(&ctx, sizeof ctx);
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explicit_bzero(results, sizeof results);
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errno = save_errno;
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return (0); /* satisfied */
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}
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