/* Read in a seed from the random_seed file and return true if this
was successful.
Note: Multiple instances of applications sharing the same random
seed file can be started in parallel, in which case they will read
out the same pool and then race for updating it (the last update
overwrites earlier updates). They will differentiate only by the
weak entropy that is added in read_seed_file based on the PID and
clock, and up to 16 bytes of weak random non-blockingly. The
consequence is that the output of these different instances is
correlated to some extent. In the perfect scenario, the attacker
can control (or at least guess) the PID and clock of the
application, and drain the system's entropy pool to reduce the "up
to 16 bytes" above to 0. Then the dependencies of the inital
states of the pools are completely known. */
static int
read_seed_file (void)
{
int fd;
struct stat sb;
unsigned char buffer[POOLSIZE];
int n;
gcry_assert (pool_is_locked);
if (!seed_file_name)
return 0;
#ifdef HAVE_DOSISH_SYSTEM
fd = open( seed_file_name, O_RDONLY | O_BINARY );
#else
fd = open( seed_file_name, O_RDONLY );
#endif
if( fd == -1 && errno == ENOENT)
{
allow_seed_file_update = 1;
return 0;
}
if (fd == -1 )
{
log_info(_("can't open `%s': %s\n"), seed_file_name, strerror(errno) );
return 0;
}
if (lock_seed_file (fd, seed_file_name, 0))
{
close (fd);
return 0;
}
if (fstat( fd, &sb ) )
{
log_info(_("can't stat `%s': %s\n"), seed_file_name, strerror(errno) );
close(fd);
return 0;
}
if (!S_ISREG(sb.st_mode) )
{
log_info(_("`%s' is not a regular file - ignored\n"), seed_file_name );
close(fd);
return 0;
}
if (!sb.st_size )
{
log_info(_("note: random_seed file is empty\n") );
close(fd);
allow_seed_file_update = 1;
return 0;
}
if (sb.st_size != POOLSIZE )
{
log_info(_("warning: invalid size of random_seed file - not used\n") );
close(fd);
return 0;
}
do
{
n = read( fd, buffer, POOLSIZE );
}
while (n == -1 && errno == EINTR );
if (n != POOLSIZE)
{
log_fatal(_("can't read `%s': %s\n"), seed_file_name,strerror(errno) );
close(fd);/*NOTREACHED*/
return 0;
}
close(fd);
add_randomness( buffer, POOLSIZE, RANDOM_ORIGIN_INIT );
/* add some minor entropy to the pool now (this will also force a mixing) */
{
pid_t x = getpid();
add_randomness( &x, sizeof(x), RANDOM_ORIGIN_INIT );
}
{
time_t x = time(NULL);
add_randomness( &x, sizeof(x), RANDOM_ORIGIN_INIT );
}
{
clock_t x = clock();
add_randomness( &x, sizeof(x), RANDOM_ORIGIN_INIT );
}
/* And read a few bytes from our entropy source. By using a level
* of 0 this will not block and might not return anything with some
* entropy drivers, however the rndlinux driver will use
* /dev/urandom and return some stuff - Do not read too much as we
* want to be friendly to the scare system entropy resource. */
read_random_source ( RANDOM_ORIGIN_INIT, 16, GCRY_WEAK_RANDOM );
allow_seed_file_update = 1;
return 1;
}
void
_gcry_rngcsprng_update_seed_file (void)
{
unsigned long *sp, *dp;
int fd, i;
/* We do only a basic initialization so that we can lock the pool.
This is required to cope with the case that this function is
called by some cleanup code at a point where the RNG has never
been initialized. */
initialize_basics ();
lock_pool ();
if ( !seed_file_name || !rndpool || !pool_filled )
{
unlock_pool ();
return;
}
if ( !allow_seed_file_update )
{
unlock_pool ();
log_info(_("note: random_seed file not updated\n"));
return;
}
/* At this point we know that there is something in the pool and
thus we can conclude that the pool has been fully initialized. */
/* Copy the entropy pool to a scratch pool and mix both of them. */
for (i=0,dp=(unsigned long*)keypool, sp=(unsigned long*)rndpool;
i < POOLWORDS; i++, dp++, sp++ )
{
*dp = *sp + ADD_VALUE;
}
mix_pool(rndpool); rndstats.mixrnd++;
mix_pool(keypool); rndstats.mixkey++;
#if defined(HAVE_DOSISH_SYSTEM) || defined(__CYGWIN__)
fd = open (seed_file_name, O_WRONLY|O_CREAT|O_TRUNC|O_BINARY,
S_IRUSR|S_IWUSR );
#else
# if LOCK_SEED_FILE
fd = open (seed_file_name, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR );
# else
fd = open (seed_file_name, O_WRONLY|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR );
# endif
#endif
if (fd == -1 )
log_info (_("can't create `%s': %s\n"), seed_file_name, strerror(errno) );
else if (lock_seed_file (fd, seed_file_name, 1))
{
close (fd);
}
#if LOCK_SEED_FILE
else if (ftruncate (fd, 0))
{
log_info(_("can't write `%s': %s\n"), seed_file_name, strerror(errno));
close (fd);
}
#endif /*LOCK_SEED_FILE*/
else
{
do
{
i = write (fd, keypool, POOLSIZE );
}
while (i == -1 && errno == EINTR);
if (i != POOLSIZE)
log_info (_("can't write `%s': %s\n"),seed_file_name, strerror(errno));
if (close(fd))
log_info (_("can't close `%s': %s\n"),seed_file_name, strerror(errno));
}
unlock_pool ();
}
void
update_random_seed_file()
{
ulong *sp, *dp;
int fd, i;
if( !seed_file_name || !is_initialized || !pool_filled )
return;
if( !allow_seed_file_update ) {
log_info(_("note: random_seed file not updated\n"));
return;
}
/* copy the entropy pool to a scratch pool and mix both of them */
for(i=0,dp=(ulong*)keypool, sp=(ulong*)rndpool;
i < POOLWORDS; i++, dp++, sp++ ) {
*dp = *sp + ADD_VALUE;
}
mix_pool(rndpool);
rndstats.mixrnd++;
mix_pool(keypool);
rndstats.mixkey++;
#if defined(HAVE_DOSISH_SYSTEM) || defined(__CYGWIN__)
fd = open( seed_file_name, O_WRONLY|O_CREAT|O_TRUNC|O_BINARY,
S_IRUSR|S_IWUSR );
#else
# if LOCK_SEED_FILE
fd = open( seed_file_name, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR );
# else
fd = open( seed_file_name, O_WRONLY|O_CREAT|O_TRUNC, S_IRUSR|S_IWUSR );
# endif
#endif
if( fd == -1 ) {
log_info(_("can't create `%s': %s\n"), seed_file_name, strerror(errno) );
return;
}
if (lock_seed_file (fd, seed_file_name, 1))
{
close (fd);
return;
}
#if LOCK_SEED_FILE
if (ftruncate (fd, 0))
{
log_info(_("can't write `%s': %s\n"), seed_file_name, strerror(errno));
close (fd);
return;
}
#endif /*LOCK_SEED_FILE*/
do {
i = write( fd, keypool, POOLSIZE );
} while( i == -1 && errno == EINTR );
if( i != POOLSIZE ) {
log_info(_("can't write `%s': %s\n"), seed_file_name, strerror(errno) );
}
if( close(fd) )
log_info(_("can't close `%s': %s\n"), seed_file_name, strerror(errno) );
}
