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Provide RNG_TRUE quality in rdrand by mixing reseeded outputs using AES

This commit is contained in:
Martin Willi 2013-01-04 17:34:07 +01:00
parent b9148ea232
commit 19ae23452a
2 changed files with 108 additions and 8 deletions
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2
src/libstrongswan/plugins/rdrand/rdrand_plugin.c
View File

@ -98,6 +98,8 @@ METHOD(plugin_t, get_features, int,
PLUGIN_REGISTER(RNG, rdrand_rng_create),
PLUGIN_PROVIDE(RNG, RNG_WEAK),
PLUGIN_PROVIDE(RNG, RNG_STRONG),
PLUGIN_PROVIDE(RNG, RNG_TRUE),
PLUGIN_DEPENDS(CRYPTER, ENCR_AES_CBC, 16),
};
*features = f;
return countof(f);

114
src/libstrongswan/plugins/rdrand/rdrand_rng.c
View File

@ -15,6 +15,8 @@
#include "rdrand_rng.h"
#include <unistd.h>
typedef struct private_rdrand_rng_t private_rdrand_rng_t;
/**
@ -44,6 +46,11 @@ struct private_rdrand_rng_t {
*/
#define FORCE_RESEED 16
/**
* How many times we mix reseeded RDRAND output when using RNG_TRUE
*/
#define MIX_ROUNDS 32
/**
* Get a two byte word using RDRAND
*/
@ -127,6 +134,29 @@ static bool rdrand8(u_int8_t *out)
return TRUE;
}
/**
* Get a 16 byte word using RDRAND
*/
static bool rdrand128(void *out)
{
#ifdef __x86_64__
if (!rdrand64(out) ||
!rdrand64(out + sizeof(u_int64_t)))
{
return FALSE;
}
#else /* __i386__ */
if (!rdrand32(out) ||
!rdrand32(out + 1 * sizeof(u_int32_t)) ||
!rdrand32(out + 2 * sizeof(u_int32_t)) ||
!rdrand32(out + 3 * sizeof(u_int32_t)))
{
return FALSE;
}
#endif /* __x86_64__ / __i386__ */
return TRUE;
}
/**
* Enforce a DRNG reseed by reading 511 128-bit samples
*/
@ -158,13 +188,11 @@ static bool reseed()
return TRUE;
}
METHOD(rng_t, get_bytes, bool,
private_rdrand_rng_t *this, size_t bytes, u_int8_t *buffer)
/**
* Fill a preallocated chunk of data with random bytes
*/
static bool rdrand_chunk(private_rdrand_rng_t *this, chunk_t chunk)
{
chunk_t chunk;
chunk = chunk_create(buffer, bytes);
if (this->quality == RNG_STRONG)
{
if (!reseed())
@ -293,6 +321,77 @@ METHOD(rng_t, get_bytes, bool,
return TRUE;
}
/**
* Stronger variant mixing reseeded results of rdrand output
*
* This is based on the Intel DRNG "Software Implementation Guide", using
* AES-CBC to mix several reseeded RDRAND outputs.
*/
static bool rdrand_mixed(private_rdrand_rng_t *this, chunk_t chunk)
{
u_char block[16], forward[16], key[16], iv[16];
crypter_t *crypter;
int i, len;
memset(iv, 0, sizeof(iv));
crypter = lib->crypto->create_crypter(lib->crypto, ENCR_AES_CBC, 16);
if (!crypter)
{
return FALSE;
}
for (i = 0; i < sizeof(key); i++)
{
key[i] = i;
}
if (!crypter->set_key(crypter, chunk_from_thing(key)))
{
crypter->destroy(crypter);
return FALSE;
}
while (chunk.len > 0)
{
memset(forward, 0, sizeof(forward));
for (i = 0; i < MIX_ROUNDS; i++)
{
/* sleep to reseed PRNG */
usleep(10);
if (!rdrand128(block))
{
crypter->destroy(crypter);
return FALSE;
}
memxor(forward, block, sizeof(block));
if (!crypter->encrypt(crypter, chunk_from_thing(forward),
chunk_from_thing(iv), NULL))
{
crypter->destroy(crypter);
return FALSE;
}
}
len = min(chunk.len, sizeof(forward));
memcpy(chunk.ptr, forward, len);
chunk = chunk_skip(chunk, len);
}
crypter->destroy(crypter);
return TRUE;
}
METHOD(rng_t, get_bytes, bool,
private_rdrand_rng_t *this, size_t bytes, u_int8_t *buffer)
{
switch (this->quality)
{
case RNG_WEAK:
case RNG_STRONG:
return rdrand_chunk(this, chunk_create(buffer, bytes));
case RNG_TRUE:
return rdrand_mixed(this, chunk_create(buffer, bytes));
default:
return FALSE;
}
}
METHOD(rng_t, allocate_bytes, bool,
private_rdrand_rng_t *this, size_t bytes, chunk_t *chunk)
{
@ -322,10 +421,9 @@ rdrand_rng_t *rdrand_rng_create(rng_quality_t quality)
{
case RNG_WEAK:
case RNG_STRONG:
break;
case RNG_TRUE:
break;
default:
/* not yet */
return NULL;
}