/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or 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. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/blockcancel.internal.h"
#include "libc/calls/calls.h"
#include "libc/calls/cp.internal.h"
#include "libc/calls/internal.h"
#include "libc/calls/struct/sigaction.h"
#include "libc/calls/struct/sigset.h"
#include "libc/calls/struct/sigset.internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/calls/syscall_support-nt.internal.h"
#include "libc/calls/syscall_support-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/asmflag.h"
#include "libc/intrin/strace.h"
#include "libc/intrin/weaken.h"
#include "libc/macros.h"
#include "libc/nexgen32e/kcpuids.h"
#include "libc/nexgen32e/rdtsc.h"
#include "libc/nexgen32e/vendor.internal.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/nexgen32e/x86info.h"
#include "libc/nt/runtime.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/rand.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/at.h"
#include "libc/sysv/consts/auxv.h"
#include "libc/sysv/consts/grnd.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/sig.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/thread.h"
__static_yoink("rdrand_init");
int sys_getentropy(void *, size_t) asm("sys_getrandom");
ssize_t sys_getrandom_metal(char *, size_t, int);
static bool have_getrandom;
static void GetRandomEntropy(char *p, size_t n) {
unassert(n <= 256);
if (sys_getentropy(p, n))
notpossible;
}
static void GetRandomArnd(char *p, size_t n) {
size_t m;
int cmd[2];
cmd[0] = 1; // CTL_KERN
cmd[1] = IsFreebsd() ? 37 : 81; // KERN_ARND
unassert((m = n) <= 256);
if (sysctl(cmd, 2, p, &n, 0, 0) == -1)
notpossible;
if (m != n)
notpossible;
}
static ssize_t GetRandomBsd(char *p, size_t n, void impl(char *, size_t)) {
size_t m, i;
for (i = 0;;) {
m = MIN(n - i, 256);
impl(p + i, m);
if ((i += m) == n) {
return n;
}
}
}
static ssize_t GetDevUrandom(char *p, size_t n, unsigned f) {
int fd;
int oflags;
ssize_t rc;
const char *dev;
BEGIN_CANCELATION_POINT;
if (f & GRND_RANDOM) {
dev = "/dev/random";
} else {
dev = "/dev/urandom";
}
oflags = O_RDONLY | O_CLOEXEC;
if (f & GRND_NONBLOCK)
oflags |= O_NONBLOCK;
fd = sys_openat(AT_FDCWD, dev, oflags, 0);
if (fd != -1) {
rc = sys_read(fd, p, n);
sys_close(fd);
} else {
rc = -1;
}
END_CANCELATION_POINT;
return rc;
}
ssize_t __getrandom(void *p, size_t n, unsigned f) {
ssize_t rc;
if (IsWindows()) {
rc = ProcessPrng(p, n) ? n : __winerr();
} else if (have_getrandom) {
if (IsXnu() || IsOpenbsd()) {
rc = GetRandomBsd(p, n, GetRandomEntropy);
} else {
BEGIN_CANCELATION_POINT;
rc = sys_getrandom(p, n, f);
END_CANCELATION_POINT;
}
} else if (IsFreebsd() || IsNetbsd()) {
rc = GetRandomBsd(p, n, GetRandomArnd);
#ifdef __x86_64__
} else if (IsMetal()) {
rc = sys_getrandom_metal(p, n, f);
#endif
} else {
BEGIN_CANCELATION_POINT;
rc = GetDevUrandom(p, n, f);
END_CANCELATION_POINT;
}
return rc;
}
/**
* Returns cryptographic random data.
*
* This random number seed generator obtains information from:
*
* - ProcessPrng() on Windows
* - getentropy() on XNU and OpenBSD
* - getrandom() on Linux, FreeBSD, and NetBSD
* - sysctl(KERN_ARND) on older versions of FreeBSD and NetBSD
*
* Unlike getentropy() this function is interruptible. However EINTR
* shouldn't be possible if `f` is zero and `n` is no more than 256,
* noting that kernels are a bit vague with their promises here, and
* if you're willing to trade some performance for a more assurances
* that EINTR won't happen, then either consider using getentropy(),
* or using the `SA_RESTART` flag on your signal handlers.
*
* Unlike getentropy() you may specify an `n` greater than 256. When
* larger amounts are specified, the caller must be prepared for the
* case where fewer than `n` bytes are returned. In that case, it is
* likely that a signal delivery occured. Cancellations in mask mode
* also need to be suppressed while processing the bytes beyond 256.
* On BSD OSes, this entire process is uninterruptible so be careful
* when using large sizes if interruptibility is needed.
*
* Unlike getentropy() this function is a cancelation point. But it
* shouldn't be a problem, unless you're using masked mode, in which
* case extra care must be taken to consider the result.
*
* It's recommended that `f` be set to zero, although it may include
* the following flags:
*
* - `GRND_NONBLOCK` when you want to elevate the insecurity of your
* random data
*
* - `GRND_RANDOM` if you want to have the best possible chance your
* program will freeze and the system operator is paged to address
* the outage by driving to the data center and jiggling the mouse
*
* @note this function could block a nontrivial time on old computers
* @note this function is indeed intended for cryptography
* @note this function takes around 900 cycles
* @raise EINVAL if `f` is invalid
* @raise ECANCELED if thread was cancelled in masked mode
* @raise EFAULT if the `n` bytes at `p` aren't valid memory
* @raise EINTR if we needed to block and a signal was delivered instead
* @cancelationpoint
* @asyncsignalsafe
* @restartable
* @vforksafe
*/
ssize_t getrandom(void *p, size_t n, unsigned f) {
ssize_t rc;
if ((!p && n)) {
rc = efault();
} else if (f & ~(GRND_RANDOM | GRND_NONBLOCK)) {
rc = einval();
} else {
rc = __getrandom(p, n, f);
}
STRACE("getrandom(%p, %'zu, %#x) → %'ld% m", p, n, f, rc);
return rc;
}
__attribute__((__constructor__(30))) static textstartup void getrandom_init(
void) {
int e, rc;
if (IsWindows() || IsMetal())
return;
BLOCK_CANCELATION;
e = errno;
if (!(rc = sys_getrandom(0, 0, 0))) {
have_getrandom = true;
} else {
errno = e;
}
ALLOW_CANCELATION;
STRACE("sys_getrandom(0,0,0) → %d% m", rc);
}