1
0
Fork 0
mirror of https://passt.top/passt synced 2025-06-07 08:25:34 +02:00

util: Add general low-level random bytes helper

Currently secret_init() open codes getting good quality random bytes from
the OS, either via getrandom(2) or reading /dev/random.  We're going to
add at least one more place that needs random data in future, so make a
general helper for getting random bytes.  While we're there, fix a number
of minor bugs:
 - getrandom() can theoretically return a "short read", so handle that case
 - getrandom() as well as read can return a transient EINTR
 - We would attempt to read data from /dev/random if we failed to open it
   (open() returns -1), but not if we opened it as fd 0 (unlikely, but ok)
 - More specific error reporting

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-11-14 14:33:08 +11:00 committed by Stefano Brivio
parent a60703e899
commit 71d5deed5e
3 changed files with 57 additions and 29 deletions

54
util.c
View file

@ -34,6 +34,9 @@
#include "passt.h"
#include "packet.h"
#include "log.h"
#ifdef HAS_GETRANDOM
#include <sys/random.h>
#endif
/**
* sock_l4_sa() - Create and bind socket to socket address, add to epoll list
@ -783,3 +786,54 @@ bool snprintf_check(char *str, size_t size, const char *format, ...)
return false;
}
#define DEV_RANDOM "/dev/random"
/**
* raw_random() - Get high quality random bytes
* @buf: Buffer to fill with random bytes
* @buflen: Number of bytes of random data to put in @buf
*
* Assumes that the random data is essential, and will die() if unable to obtain
* it.
*/
void raw_random(void *buf, size_t buflen)
{
size_t random_read = 0;
#ifndef HAS_GETRANDOM
int fd = open(DEV_RANDOM, O_RDONLY);
if (fd < 0)
die_perror("Couldn't open %s", DEV_RANDOM);
#endif
while (random_read < buflen) {
ssize_t ret;
#ifdef HAS_GETRANDOM
ret = getrandom((char *)buf + random_read,
buflen - random_read, GRND_RANDOM);
#else
ret = read(dev_random, (char *)buf + random_read,
buflen - random_read);
#endif
if (ret == -1 && errno == EINTR)
continue;
if (ret < 0)
die_perror("Error on random data source");
if (ret == 0)
break;
random_read += ret;
}
#ifndef HAS_GETRANDOM
close(dev_random);
#endif
if (random_read < buflen)
die("Unexpected EOF on random data source");
}