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Windows driver: better randomness for wipe bytes by always using Whirlpool hash of current time and random bytes retrieved using CPU RDRAND/RDSEED if available.

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This commit is contained in:
Mounir IDRASSI
2019-01-31 01:10:38 +01:00
parent 61c1baa4bf
commit 5571a8ba6b
3 changed files with 40 additions and 19 deletions
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47
src/Driver/DriveFilter.c
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@@ -28,6 +28,7 @@
#include "DriveFilter.h"
#include "Boot/Windows/BootCommon.h"
#include "cpu.h"
#include "rdrand.h"
static BOOL DeviceFilterActive = FALSE;
@@ -1521,30 +1522,38 @@ static VOID SetupThreadProc (PVOID threadArg)
// generate real random values for wipeRandChars and
// wipeRandCharsUpdate instead of relying on uninitialized stack memory
LARGE_INTEGER iSeed;
byte digest[WHIRLPOOL_DIGESTSIZE];
WHIRLPOOL_CTX tctx;
#ifndef _WIN64
KFLOATING_SAVE floatingPointState;
NTSTATUS saveStatus = STATUS_INVALID_PARAMETER;
if (HasISSE())
saveStatus = KeSaveFloatingPointState (&floatingPointState);
#endif
KeQuerySystemTime( &iSeed );
if (KeGetCurrentIrql() < DISPATCH_LEVEL)
WHIRLPOOL_init (&tctx);
WHIRLPOOL_add ((unsigned char *) &(iSeed.QuadPart), sizeof(iSeed.QuadPart), &tctx);
// use RDSEED or RDRAND from CPU as source of entropy if present
if ( (HasRDSEED() && RDSEED_getBytes (digest, sizeof (digest)))
|| (HasRDRAND() && RDRAND_getBytes (digest, sizeof (digest)))
)
{
ULONG ulRandom;
ulRandom = RtlRandomEx( &iSeed.LowPart );
memcpy (wipeRandChars, &ulRandom, TC_WIPE_RAND_CHAR_COUNT);
ulRandom = RtlRandomEx( &ulRandom );
memcpy (wipeRandCharsUpdate, &ulRandom, TC_WIPE_RAND_CHAR_COUNT);
burn (&ulRandom, sizeof(ulRandom));
WHIRLPOOL_add (digest, sizeof(digest), &tctx);
}
else
{
byte digest[SHA512_DIGESTSIZE];
sha512_ctx tctx;
sha512_begin (&tctx);
sha512_hash ((unsigned char *) &(iSeed.QuadPart), sizeof(iSeed.QuadPart), &tctx);
sha512_end (digest, &tctx);
WHIRLPOOL_finalize (&tctx, digest);
memcpy (wipeRandChars, digest, TC_WIPE_RAND_CHAR_COUNT);
memcpy (wipeRandCharsUpdate, &digest[SHA512_DIGESTSIZE - TC_WIPE_RAND_CHAR_COUNT], TC_WIPE_RAND_CHAR_COUNT);
#if !defined (_WIN64)
if (NT_SUCCESS (saveStatus))
KeRestoreFloatingPointState (&floatingPointState);
#endif
burn (digest, SHA512_DIGESTSIZE);
burn (&tctx, sizeof (tctx));
}
memcpy (wipeRandChars, digest, TC_WIPE_RAND_CHAR_COUNT);
memcpy (wipeRandCharsUpdate, &digest[WHIRLPOOL_DIGESTSIZE - TC_WIPE_RAND_CHAR_COUNT], TC_WIPE_RAND_CHAR_COUNT);
burn (digest, WHIRLPOOL_DIGESTSIZE);
burn (&tctx, sizeof (tctx));
burn (&iSeed, sizeof(iSeed));