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Merge pull request #280 from masahisak/fix_dev_urandom

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random-util.c: sync dev_urandom implementation to systemd-udev
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Boian Bonev 2024-04-28 12:49:34 +05:30 committed by GitHub
commit fc9050ca28
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2 changed files with 31 additions and 35 deletions
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4
src/shared/missing.h
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@ -79,6 +79,10 @@ static inline int getrandom(void *buffer, size_t count, unsigned flags) {
#define GRND_RANDOM 0x0002
#endif
#ifndef GRND_INSECURE
#define GRND_INSECURE 0x0004
#endif
#ifndef BTRFS_IOCTL_MAGIC
#define BTRFS_IOCTL_MAGIC 0x94
#endif

62
src/shared/random-util.c
View File

@ -31,45 +31,37 @@
#include "util.h"
int dev_urandom(void *p, size_t n) {
static int have_syscall = -1;
static bool have_getrandom = true, have_grndinsecure = true;
_cleanup_close_ int fd = -EBADF;
_cleanup_close_ int fd = -1;
int r;
if (n == 0)
return 0;
/* Gathers some randomness from the kernel. This call will
* never block, and will always return some data from the
* kernel, regardless if the random pool is fully initialized
* or not. It thus makes no guarantee for the quality of the
* returned entropy, but is good enough for or usual usecases
* of seeding the hash functions for hashtable */
for (;;) {
ssize_t l;
/* Use the getrandom() syscall unless we know we don't have
* it, or when the requested size is too large for it. */
if (have_syscall != 0 || (size_t) (int) n != n) {
r = getrandom(p, n, GRND_NONBLOCK);
if (r == (int) n) {
have_syscall = true;
return 0;
}
if (!have_getrandom)
break;
if (r < 0) {
if (errno == ENOSYS)
/* we lack the syscall, continue with
* reading from /dev/urandom */
have_syscall = false;
else if (errno == EAGAIN)
/* not enough entropy for now. Let's
* remember to use the syscall the
* next time, again, but also read
* from /dev/urandom for now, which
* doesn't care about the current
* amount of entropy. */
have_syscall = true;
else
return -errno;
} else
/* too short read? */
return -ENODATA;
l = getrandom(p, n, have_grndinsecure ? GRND_INSECURE : GRND_NONBLOCK);
if (l > 0) {
if ((size_t) l == n)
return 0; /* Done reading, success. */
p = (uint8_t *) p + l;
n -= l;
continue; /* Interrupted by a signal; keep going. */
} else if (l == 0)
break; /* Weird, so fallback to /dev/urandom. */
else if (errno == ENOSYS) {
have_getrandom = false;
break; /* No syscall, so fallback to /dev/urandom. */
} else if (errno == EINVAL && have_grndinsecure) {
have_grndinsecure = false;
continue; /* No GRND_INSECURE; fallback to GRND_NONBLOCK. */
} else if (errno == EAGAIN && !have_grndinsecure)
break; /* Will block, but no GRND_INSECURE, so fallback to /dev/urandom. */
break; /* Unexpected, so just give up and fallback to /dev/urandom. */
}
fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);