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xmlparse.c: Read /dev/urandom if non-blocking getrandom failed

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This is in line with what recent Python does:

1) Calling getrandom with GRND_NONBLOCK
1abcf6700b/Python/bootstrap_hash.c (L594)

2) Reading /dev/urandom if getrandom failed
1abcf6700b/Python/bootstrap_hash.c (L503)
This commit is contained in:
Sebastian Pipping 2017-07-26 20:40:55 +02:00
parent cfd6b138d6
commit 55839b633f
1 changed files with 40 additions and 1 deletions
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41
expat/lib/xmlparse.c
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@ -21,6 +21,8 @@
#include <sys/time.h> /* gettimeofday() */
#include <sys/types.h> /* getpid() */
#include <unistd.h> /* getpid() */
#include <fcntl.h> /* O_RDONLY */
#include <errno.h>
#endif
#define XML_BUILDING_EXPAT 1
@ -36,7 +38,6 @@
#include "siphash.h"
#if defined(HAVE_GETRANDOM) || defined(HAVE_SYSCALL_GETRANDOM)
# include <errno.h>
# if defined(HAVE_GETRANDOM)
# include <sys/random.h> /* getrandom */
# else
@ -783,6 +784,39 @@ writeRandomBytes_getrandom_nonblock(void * target, size_t count) {
#endif /* defined(HAVE_GETRANDOM) || defined(HAVE_SYSCALL_GETRANDOM) */
#if ! defined(_WIN32)
/* Extract entropy from /dev/urandom */
static int
writeRandomBytes_dev_urandom(void * target, size_t count) {
int success = 0; /* full count bytes written? */
size_t bytesWrittenTotal = 0;
const int fd = open("/dev/urandom", O_RDONLY);
if (fd < 0) {
return 0;
}
do {
void * const currentTarget = (void*)((char*)target + bytesWrittenTotal);
const size_t bytesToWrite = count - bytesWrittenTotal;
const ssize_t bytesWrittenMore = read(fd, currentTarget, bytesToWrite);
if (bytesWrittenMore > 0) {
bytesWrittenTotal += bytesWrittenMore;
if (bytesWrittenTotal >= count)
success = 1;
}
} while (! success && (errno == EINTR));
close(fd);
return success;
}
#endif /* ! defined(_WIN32) */
#if defined(HAVE_ARC4RANDOM)
static void
@ -905,6 +939,11 @@ generate_hash_secret_salt(XML_Parser parser)
return ENTROPY_DEBUG("getrandom", entropy);
}
#endif
#if ! defined(_WIN32)
if (writeRandomBytes_dev_urandom((void *)&entropy, sizeof(entropy))) {
return ENTROPY_DEBUG("/dev/urandom", entropy);
}
#endif /* ! defined(_WIN32) */
/* .. and self-made low quality for backup: */
/* Process ID is 0 bits entropy if attacker has local access */