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-rw-r--r--lib/util/getentropy.c605
1 files changed, 605 insertions, 0 deletions
diff --git a/lib/util/getentropy.c b/lib/util/getentropy.c
new file mode 100644
index 0000000..bfd7dcd
--- /dev/null
+++ b/lib/util/getentropy.c
@@ -0,0 +1,605 @@
+/*
+ * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
+ * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Emulation of getentropy(2) as documented at:
+ * http://man.openbsd.org/getentropy.2
+ */
+
+#include <config.h>
+
+#ifndef HAVE_GETENTROPY
+
+#include <sys/param.h>
+#include <sys/mman.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#ifdef HAVE_SYSCTL
+# include <sys/sysctl.h>
+#endif
+#ifdef HAVE_SYS_STATVFS_H
+# include <sys/statvfs.h>
+#endif
+#include <sys/stat.h>
+#include <sys/time.h>
+#ifdef HAVE_SYS_SYSCALL_H
+# include <sys/syscall.h>
+#endif
+#ifdef HAVE_LINUX_RANDOM_H
+# include <linux/types.h>
+# include <linux/random.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <time.h>
+#include <unistd.h>
+#if defined(HAVE_STDINT_H)
+# include <stdint.h>
+#elif defined(HAVE_INTTYPES_H)
+# include <inttypes.h>
+#endif
+#ifdef HAVE_GETAUXVAL
+# include <sys/auxv.h>
+#endif
+#ifdef HAVE_DL_ITERATE_PHDR
+# include <link.h>
+#endif
+
+#include "sudo_compat.h"
+#include "sudo_digest.h"
+#include "sudo_rand.h"
+
+#if !defined(MAP_ANON) && defined(MAP_ANONYMOUS)
+# define MAP_ANON MAP_ANONYMOUS
+#endif
+
+#define REPEAT 5
+#define min(a, b) (((a) < (b)) ? (a) : (b))
+
+#define HX(a, b) \
+ do { \
+ if ((a)) \
+ HD(errno); \
+ else \
+ HD(b); \
+ } while (0)
+
+#define HR(x, l) (sudo_digest_update(ctx, (char *)(x), (l)))
+#define HD(x) (sudo_digest_update(ctx, (char *)&(x), sizeof (x)))
+#define HF(x) (sudo_digest_update(ctx, (char *)&(x), sizeof (void*)))
+
+int sudo_getentropy(void *buf, size_t len);
+
+static int getentropy_getrandom(void *buf, size_t len);
+static int getentropy_sysctl(void *buf, size_t len);
+static int getentropy_urandom(void *buf, size_t len, const char *path,
+ int devfscheck);
+static int getentropy_fallback(void *buf, size_t len);
+static int gotdata(char *buf, size_t len);
+#ifdef HAVE_DL_ITERATE_PHDR
+static int getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data);
+#endif
+
+int
+sudo_getentropy(void *buf, size_t len)
+{
+ int ret = -1;
+
+ if (len > 256) {
+ errno = EIO;
+ return (-1);
+ }
+
+ ret = getentropy_getrandom(buf, len);
+ if (ret != -1)
+ return (ret);
+
+ ret = getentropy_sysctl(buf, len);
+ if (ret != -1)
+ return (ret);
+
+ /*
+ * Try to get entropy with /dev/urandom
+ */
+ ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
+ if (ret != -1)
+ return (ret);
+
+ /*
+ * Entropy collection via /dev/urandom has failed.
+ *
+ * No other API exists for collecting entropy, and we have no
+ * failsafe way to get it that is not sensitive to resource exhaustion.
+ *
+ * We have very few options:
+ * - Even syslog_r is unsafe to call at this low level, so
+ * there is no way to alert the user or program.
+ * - Cannot call abort() because some systems have unsafe
+ * corefiles.
+ * - Could raise(SIGKILL) resulting in silent program termination.
+ * - Return EIO, to hint that arc4random's stir function
+ * should raise(SIGKILL)
+ * - Do the best under the circumstances....
+ *
+ * This code path exists to bring light to the issue that the OS
+ * does not provide a failsafe API for entropy collection.
+ *
+ * We hope this demonstrates that the OS should consider
+ * providing a new failsafe API which works in a chroot or
+ * when file descriptors are exhausted.
+ */
+#undef FAIL_INSTEAD_OF_TRYING_FALLBACK
+#ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
+ raise(SIGKILL);
+#endif
+ ret = getentropy_fallback(buf, len);
+ if (ret != -1)
+ return (ret);
+
+ errno = EIO;
+ return (ret);
+}
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+/*
+ * Basic sanity checking; wish we could do better.
+ */
+static int
+gotdata(char *buf, size_t len)
+{
+ char any_set = 0;
+ size_t i;
+
+ for (i = 0; i < len; ++i)
+ any_set |= buf[i];
+ if (any_set == 0)
+ return (-1);
+ return (0);
+}
+
+static int
+getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
+{
+ struct stat st;
+ size_t i;
+ int fd, flags;
+ int save_errno = errno;
+
+start:
+
+ /* We do not use O_NOFOLLOW since /dev/urandom is a link on Solaris. */
+ flags = O_RDONLY;
+#ifdef O_CLOEXEC
+ flags |= O_CLOEXEC;
+#endif
+ fd = open(path, flags, 0);
+ if (fd == -1) {
+ if (errno == EINTR)
+ goto start;
+ goto nodevrandom;
+ }
+#ifndef O_CLOEXEC
+ fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
+#endif
+
+ /* Lightly verify that the device node looks sane */
+ if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
+ close(fd);
+ goto nodevrandom;
+ }
+ for (i = 0; i < len; ) {
+ size_t wanted = len - i;
+ ssize_t ret = read(fd, (char *)buf + i, wanted);
+
+ if (ret == -1) {
+ if (errno == EAGAIN || errno == EINTR)
+ continue;
+ close(fd);
+ goto nodevrandom;
+ }
+ i += ret;
+ }
+ close(fd);
+ if (gotdata(buf, len) == 0) {
+ errno = save_errno;
+ return (0); /* satisfied */
+ }
+nodevrandom:
+ errno = EIO;
+ return (-1);
+}
+
+#if defined(HAVE_SYSCTL) && defined(KERN_ARND)
+static int
+getentropy_sysctl(void *buf, size_t len)
+{
+ int save_errno = errno;
+ int mib[2];
+ size_t i;
+
+ mib[0] = CTL_KERN;
+ mib[1] = KERN_ARND;
+
+ for (i = 0; i < len; ) {
+ size_t chunk = len - i;
+
+ if (sysctl(mib, 2, (char *)buf + i, &chunk, NULL, 0) == -1)
+ goto sysctlfailed;
+ i += chunk;
+ }
+ if (gotdata(buf, len) == 0) {
+ errno = save_errno;
+ return (0); /* satisfied */
+ }
+sysctlfailed:
+ errno = EIO;
+ return (-1);
+}
+#elif defined(SYS__sysctl) && defined(RANDOM_UUID)
+static int
+getentropy_sysctl(void *buf, size_t len)
+{
+ static int mib[3];
+ size_t i;
+ int save_errno = errno;
+
+ mib[0] = CTL_KERN;
+ mib[1] = KERN_RANDOM;
+ mib[2] = RANDOM_UUID;
+
+ for (i = 0; i < len; ) {
+ size_t chunk = min(len - i, 16);
+
+ /* SYS__sysctl because some systems already removed sysctl() */
+ struct __sysctl_args args = {
+ .name = mib,
+ .nlen = 3,
+ .oldval = (char *)buf + i,
+ .oldlenp = &chunk,
+ };
+ if (syscall(SYS__sysctl, &args) != 0)
+ goto sysctlfailed;
+ i += chunk;
+ }
+ if (gotdata(buf, len) == 0) {
+ errno = save_errno;
+ return (0); /* satisfied */
+ }
+sysctlfailed:
+ errno = EIO;
+ return (-1);
+}
+#else
+static int
+getentropy_sysctl(void *buf, size_t len)
+{
+ errno = ENOTSUP;
+ return (-1);
+}
+#endif
+
+#if defined(SYS_getrandom) && defined(GRND_NONBLOCK)
+static int
+getentropy_getrandom(void *buf, size_t len)
+{
+ int pre_errno = errno;
+ int ret;
+
+ /*
+ * Try descriptor-less getrandom(), in non-blocking mode.
+ *
+ * The design of Linux getrandom is broken. It has an
+ * uninitialized phase coupled with blocking behaviour, which
+ * is unacceptable from within a library at boot time without
+ * possible recovery. See http://bugs.python.org/issue26839#msg267745
+ */
+ do {
+ ret = syscall(SYS_getrandom, buf, len, GRND_NONBLOCK);
+ } while (ret == -1 && errno == EINTR);
+
+ if (ret < 0 || (size_t)ret != len)
+ return (-1);
+ errno = pre_errno;
+ return (0);
+}
+#else
+static int
+getentropy_getrandom(void *buf, size_t len)
+{
+ errno = ENOTSUP;
+ return (-1);
+}
+#endif
+
+#ifdef HAVE_CLOCK_GETTIME
+static const int cl[] = {
+ CLOCK_REALTIME,
+#ifdef CLOCK_MONOTONIC
+ CLOCK_MONOTONIC,
+#endif
+#ifdef CLOCK_MONOTONIC_RAW
+ CLOCK_MONOTONIC_RAW,
+#endif
+#ifdef CLOCK_TAI
+ CLOCK_TAI,
+#endif
+#ifdef CLOCK_VIRTUAL
+ CLOCK_VIRTUAL,
+#endif
+#ifdef CLOCK_UPTIME
+ CLOCK_UPTIME,
+#endif
+#ifdef CLOCK_PROCESS_CPUTIME_ID
+ CLOCK_PROCESS_CPUTIME_ID,
+#endif
+#ifdef CLOCK_THREAD_CPUTIME_ID
+ CLOCK_THREAD_CPUTIME_ID,
+#endif
+};
+#endif /* HAVE_CLOCK_GETTIME */
+
+#ifdef HAVE_DL_ITERATE_PHDR
+static int
+getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data)
+{
+ struct sudo_digest *ctx = data;
+
+ sudo_digest_update(ctx, &info->dlpi_addr, sizeof (info->dlpi_addr));
+ return (0);
+}
+#endif
+
+static int
+getentropy_fallback(void *buf, size_t len)
+{
+ unsigned char *results = NULL;
+ int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
+ int ret = -1;
+ static int cnt;
+ struct timespec ts;
+ struct timeval tv;
+ struct rusage ru;
+ sigset_t sigset;
+ struct stat st;
+ struct sudo_digest *ctx;
+ static pid_t lastpid;
+ pid_t pid;
+ size_t i, ii, m, digest_len;
+ char *p;
+
+ if ((ctx = sudo_digest_alloc(SUDO_DIGEST_SHA512)) == NULL)
+ goto done;
+ digest_len = sudo_digest_getlen(SUDO_DIGEST_SHA512);
+ if (digest_len == (size_t)-1 || (results = malloc(digest_len)) == NULL)
+ goto done;
+
+ pid = getpid();
+ if (lastpid == pid) {
+ faster = 1;
+ repeat = 2;
+ } else {
+ faster = 0;
+ lastpid = pid;
+ repeat = REPEAT;
+ }
+ for (i = 0; i < len; ) {
+ int j;
+ 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;
+ }
+#ifdef HAVE_DL_ITERATE_PHDR
+ dl_iterate_phdr(getentropy_phdr, ctx);
+#endif
+
+#ifdef HAVE_CLOCK_GETTIME
+ for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
+ HX(clock_gettime(cl[ii], &ts) == -1, ts);
+#endif /* HAVE_CLOCK_GETTIME */
+
+ 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(sudo_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) {
+#ifdef HAVE_SYS_STATVFS_H
+ struct statvfs stvfs;
+#endif
+ struct termios tios;
+ 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(stat("/", &st) == -1, st);
+
+#ifdef HAVE_SYS_STATVFS_H
+ HX(statvfs(".", &stvfs) == -1, stvfs);
+ HX(statvfs("/", &stvfs) == -1, stvfs);
+#endif
+ 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)) {
+#ifdef HAVE_SYS_STATVFS_H
+ HX(fstatvfs(0, &stvfs) == -1,
+ stvfs);
+#endif
+ HX((off = lseek(0, (off_t)0,
+ SEEK_CUR)) < 0, off);
+ }
+ if (S_ISCHR(st.st_mode)) {
+ HX(tcgetattr(0, &tios) == -1,
+ tios);
+#if 0
+ } else if (S_ISSOCK(st.st_mode)) {
+ struct sockaddr_storage ss;
+ socklen_t ssl;
+ memset(&ss, 0, sizeof ss);
+ ssl = sizeof(ss);
+ HX(getpeername(0,
+ (void *)&ss, &ssl) == -1,
+ ss);
+#endif
+ }
+ }
+
+ 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 */
+ HR(results, digest_len);
+ }
+
+ 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 /* HAVE_GETAUXVAL */
+
+ sudo_digest_final(ctx, results);
+ sudo_digest_reset(ctx);
+ memcpy((char *)buf + i, results, min(digest_len, len - i));
+ i += min(digest_len, len - i);
+ }
+ if (gotdata(buf, len) == 0) {
+ errno = save_errno;
+ ret = 0; /* satisfied */
+ } else {
+ errno = EIO;
+ }
+done:
+ sudo_digest_free(ctx);
+ if (results != NULL) {
+ memset_s(results, sizeof(results), 0, sizeof(results));
+ free(results);
+ }
+ return (ret);
+}
+
+#endif /* HAVE_GETENTROPY */
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