diff options
Diffstat (limited to 'compat/getentropy_osx.c')
| -rw-r--r-- | compat/getentropy_osx.c | 417 |
1 files changed, 417 insertions, 0 deletions
diff --git a/compat/getentropy_osx.c b/compat/getentropy_osx.c new file mode 100644 index 0000000..5d4067b --- /dev/null +++ b/compat/getentropy_osx.c @@ -0,0 +1,417 @@ +/* $OpenBSD: getentropy_osx.c,v 1.13 2020/05/17 14:44:20 deraadt Exp $ */ + +/* + * 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 <TargetConditionals.h> +#include <sys/types.h> +#include <sys/param.h> +#include <sys/ioctl.h> +#include <sys/resource.h> +#include <sys/syscall.h> +#include <sys/sysctl.h> +#include <sys/statvfs.h> +#include <sys/socket.h> +#include <sys/mount.h> +#include <sys/mman.h> +#include <sys/stat.h> +#include <sys/time.h> +#include <stdlib.h> +#include <stdint.h> +#include <stdio.h> +#include <termios.h> +#include <fcntl.h> +#include <signal.h> +#include <string.h> +#include <errno.h> +#include <unistd.h> +#include <time.h> +#include <mach/mach_time.h> +#include <mach/mach_host.h> +#include <mach/host_info.h> +#if TARGET_OS_OSX +#include <sys/socketvar.h> +#include <sys/vmmeter.h> +#endif +#include <netinet/in.h> +#include <netinet/tcp.h> +#if TARGET_OS_OSX +#include <netinet/udp.h> +#include <netinet/ip_var.h> +#include <netinet/tcp_var.h> +#include <netinet/udp_var.h> +#endif +#include <CommonCrypto/CommonDigest.h> +#define SHA512_Update(a, b, c) (CC_SHA512_Update((a), (b), (c))) +#define SHA512_Init(xxx) (CC_SHA512_Init((xxx))) +#define SHA512_Final(xxx, yyy) (CC_SHA512_Final((xxx), (yyy))) +#define SHA512_CTX CC_SHA512_CTX +#define SHA512_DIGEST_LENGTH CC_SHA512_DIGEST_LENGTH + +#define REPEAT 5 +#define MINIMUM(a, b) (((a) < (b)) ? (a) : (b)) + +#define HX(a, b) \ + do { \ + if ((a)) \ + HD(errno); \ + else \ + HD(b); \ + } while (0) + +#define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l))) +#define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x))) +#define HF(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (void*))) + +int getentropy(void *buf, size_t len); + +static int getentropy_urandom(void *buf, size_t len); +static int getentropy_fallback(void *buf, size_t len); + +int +getentropy(void *buf, size_t len) +{ + int ret = -1; + + if (len > 256) { + errno = EIO; + return (-1); + } + + /* + * Try to get entropy with /dev/urandom + * + * This can fail if the process is inside a chroot or if file + * descriptors are exhausted. + */ + ret = getentropy_urandom(buf, len); + if (ret != -1) + return (ret); + + /* + * Entropy collection via /dev/urandom and sysctl have failed. + * + * No other API exists for collecting entropy, and we have + * no failsafe way to get it on OSX 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 OSX + * does not provide a failsafe API for entropy collection. + * + * We hope this demonstrates that OSX 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); +} + +static int +getentropy_urandom(void *buf, size_t len) +{ + struct stat st; + size_t i; + int fd, flags; + int save_errno = errno; + +start: + + flags = O_RDONLY; +#ifdef O_NOFOLLOW + flags |= O_NOFOLLOW; +#endif +#ifdef O_CLOEXEC + flags |= O_CLOEXEC; +#endif + fd = open("/dev/urandom", 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); + errno = save_errno; + return (0); /* satisfied */ +nodevrandom: + errno = EIO; + return (-1); +} + +#if TARGET_OS_OSX +static int tcpmib[] = { CTL_NET, AF_INET, IPPROTO_TCP, TCPCTL_STATS }; +static int udpmib[] = { CTL_NET, AF_INET, IPPROTO_UDP, UDPCTL_STATS }; +static int ipmib[] = { CTL_NET, AF_INET, IPPROTO_IP, IPCTL_STATS }; +#endif +static int kmib[] = { CTL_KERN, KERN_USRSTACK }; +static int hwmib[] = { CTL_HW, HW_USERMEM }; + +static int +getentropy_fallback(void *buf, size_t len) +{ + uint8_t results[SHA512_DIGEST_LENGTH]; + int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat; + static int cnt; + struct timespec ts; + struct timeval tv; + struct rusage ru; + sigset_t sigset; + struct stat st; + SHA512_CTX ctx; + static pid_t lastpid; + pid_t pid; + size_t i, ii, m; + char *p; +#if TARGET_OS_OSX + struct tcpstat tcpstat; + struct udpstat udpstat; + struct ipstat ipstat; +#endif + u_int64_t mach_time; + unsigned int idata; + void *addr; + + pid = getpid(); + if (lastpid == pid) { + faster = 1; + repeat = 2; + } else { + faster = 0; + lastpid = pid; + repeat = REPEAT; + } + 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; + } + + mach_time = mach_absolute_time(); + HD(mach_time); + + ii = sizeof(addr); + HX(sysctl(kmib, sizeof(kmib) / sizeof(kmib[0]), + &addr, &ii, NULL, 0) == -1, addr); + + ii = sizeof(idata); + HX(sysctl(hwmib, sizeof(hwmib) / sizeof(hwmib[0]), + &idata, &ii, NULL, 0) == -1, idata); + +#if TARGET_OS_OSX + ii = sizeof(tcpstat); + HX(sysctl(tcpmib, sizeof(tcpmib) / sizeof(tcpmib[0]), + &tcpstat, &ii, NULL, 0) == -1, tcpstat); + + ii = sizeof(udpstat); + HX(sysctl(udpmib, sizeof(udpmib) / sizeof(udpmib[0]), + &udpstat, &ii, NULL, 0) == -1, udpstat); + + ii = sizeof(ipstat); + HX(sysctl(ipmib, sizeof(ipmib) / sizeof(ipmib[0]), + &ipstat, &ii, NULL, 0) == -1, ipstat); +#endif + + 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... */ + mach_time = mach_absolute_time(); + HD(mach_time); + cnt += (int)mach_time; + + 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); + } + + SHA512_Final(results, &ctx); + memcpy((char *)buf + i, results, MINIMUM(sizeof(results), len - i)); + i += MINIMUM(sizeof(results), len - i); + } + explicit_bzero(&ctx, sizeof ctx); + explicit_bzero(results, sizeof results); + errno = save_errno; + return (0); /* satisfied */ +} |