JehanneOS/newlib
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Rearrange RNG code slightly

Browse Source 
In preparation of exporting getentropy/getrandom to userspace, rearrange
code a bit:

- Define RtlGenRandom in ntdll.h.

- Drop calls to getentropy in favor of RtlGenRandom (fhandler_socket,
  fhandler_dev_random).

- Add try/except blocks in fhandler_dev_random to return EFAULT rather
  than crashing if buffer pointer is invalid.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen
2016-12-13 22:59:31 +01:00
parent 80f4987f02
commit 74f7872f89
4 changed files with 52 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

72
winsup/cygwin/fhandler_random.cc
View File

@@ -47,16 +47,26 @@ fhandler_dev_random::write (const void *ptr, size_t len)
}
/* Limit len to a value <= 4096 since we don't want to overact.
Copy to local buffer because CryptGenRandom violates const. */
Copy to local buffer because RtlGenRandom violates const. */
size_t limited_len = MIN (len, 4096);
unsigned char buf[limited_len];
memcpy (buf, ptr, limited_len);
/* Mess up system entropy source. Return error if device is /dev/random. */
if (getentropy (buf, limited_len) && dev () == FH_RANDOM)
return -1;
/* Mess up the pseudo random number generator. */
pseudo_write (buf, limited_len);
__try
{
memcpy (buf, ptr, limited_len);
if (!RtlGenRandom (buf, limited_len) && dev () == FH_RANDOM)
return -1;
/* Mess up the pseudo random number generator. */
pseudo_write (buf, limited_len);
}
__except (EFAULT)
{
len = -1;
}
__endtry
/* Note that we return len, not limited_len. No reason to confuse the
caller... */
return len;
}
@@ -88,32 +98,40 @@ fhandler_dev_random::read (void *ptr, size_t& len)
return;
}
/* /dev/random has to provide high quality random numbers. Therefore we
re-seed the system PRNG for each block of 512 bytes. This results in
sufficiently random sequences, comparable to the Linux /dev/random. */
if (dev () == FH_RANDOM)
__try
{
void *dummy = malloc (RESEED_INTERVAL);
if (!dummy)
/* /dev/random has to provide high quality random numbers. Therefore we
re-seed the system PRNG for each block of 512 bytes. This results in
sufficiently random sequences, comparable to the Linux /dev/random. */
if (dev () == FH_RANDOM)
{
__seterrno ();
len = (size_t) -1;
return;
}
for (size_t offset = 0; offset < len; offset += 512)
{
if (getentropy (dummy, RESEED_INTERVAL) ||
getentropy ((PBYTE) ptr + offset, len - offset))
void *dummy = malloc (RESEED_INTERVAL);
if (!dummy)
{
__seterrno ();
len = (size_t) -1;
break;
return;
}
for (size_t offset = 0; offset < len; offset += 512)
{
if (!RtlGenRandom (dummy, RESEED_INTERVAL) ||
!RtlGenRandom ((PBYTE) ptr + offset, len - offset))
{
len = (size_t) -1;
break;
}
}
free (dummy);
}
free (dummy);
}
/* If device is /dev/urandom, just use system RNG as is, with our own
PRNG as fallback. */
else if (getentropy (ptr, len))
len = pseudo_read (ptr, len);
/* If device is /dev/urandom, just use system RNG as is, with our own
PRNG as fallback. */
else if (!RtlGenRandom (ptr, len))
len = pseudo_read (ptr, len);
}
__except (EFAULT)
{
len = (size_t) -1;
}
__endtry
}