patch 3/3: modify cprng to make contnuity check fips compliant and allow for a
disabling of the continuity test when the RNG is placed in FIPS mode
Signed-off-by: Neil Horman <nhor...@txudriver.com>
ansi_cprng.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 51 insertions(+), 5 deletions(-)
diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index 3aa6e38..c1ba5e8 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -33,6 +33,7 @@
#define PRNG_FIXED_SIZE 0x1
#define PRNG_NEED_RESET 0x2
+#define PRNG_DISABLE_CONT_TEST 0x3
/*
* Note: DT is our counter value
@@ -85,7 +86,7 @@ static void xor_vectors(unsigned char *in1, unsigned char
*in2,
* Returns DEFAULT_BLK_SZ bytes of random data per call
* returns 0 if generation succeded, <0 if something went wrong
*/
-static int _get_more_prng_bytes(struct prng_context *ctx)
+static int _get_more_prng_bytes(struct prng_context *ctx, int test)
{
int i;
unsigned char tmp[DEFAULT_BLK_SZ];
@@ -130,6 +131,9 @@ static int _get_more_prng_bytes(struct prng_context *ctx)
* First check that we didn't produce the same
* random data that we did last time around through this
*/
+ if (ctx->flags & PRNG_DISABLE_CONT_TEST)
+ goto skip_test;
+
if (!memcmp(ctx->rand_data, ctx->last_rand_data,
DEFAULT_BLK_SZ)) {
if (fips_enabled) {
@@ -146,7 +150,7 @@ static int _get_more_prng_bytes(struct prng_context *ctx)
}
memcpy(ctx->last_rand_data, ctx->rand_data,
DEFAULT_BLK_SZ);
-
+skip_test:
/*
* Lastly xor the random data with I
* and encrypt that to obtain a new secret vector V
@@ -220,7 +224,7 @@ static int get_prng_bytes(char *buf, size_t nbytes, struct
prng_context *ctx)
remainder:
if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
- if (_get_more_prng_bytes(ctx) < 0) {
+ if (_get_more_prng_bytes(ctx, 1) < 0) {
memset(buf, 0, nbytes);
err = -EINVAL;
goto done;
@@ -247,7 +251,7 @@ empty_rbuf:
*/
for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
- if (_get_more_prng_bytes(ctx) < 0) {
+ if (_get_more_prng_bytes(ctx, 1) < 0) {
memset(buf, 0, nbytes);
err = -EINVAL;
goto done;
@@ -306,7 +310,6 @@ static int reset_prng_context(struct prng_context *ctx,
memset(ctx->rand_data, 0, DEFAULT_BLK_SZ);
memset(ctx->last_rand_data, 0, DEFAULT_BLK_SZ);
- ctx->rand_data_valid = DEFAULT_BLK_SZ;
ret = crypto_cipher_setkey(ctx->tfm, prng_key, klen);
if (ret) {
@@ -317,6 +320,18 @@ static int reset_prng_context(struct prng_context *ctx,
ret = 0;
ctx->flags &= ~PRNG_NEED_RESET;
+
+ /*
+ * If we don't disable the continuity test
+ * we need to seed the n=0 iteration for test
+ * comparison, so we get a first block here that
+ * we never return to the user
+ */
+ ctx->rand_data_valid = DEFAULT_BLK_SZ;
+ if (!(ctx->flags & PRNG_DISABLE_CONT_TEST))
+ _get_more_prng_bytes(ctx, 0);
+
+ ctx->rand_data_valid = DEFAULT_BLK_SZ;
out:
spin_unlock_bh(&ctx->prng_lock);
return ret;
@@ -384,6 +399,35 @@ static int cprng_reset(struct crypto_rng *tfm, u8 *seed,
unsigned int slen)
return 0;
}
+ /*
+ * These are the registered functions which export behavioral flags
+ * to the crypto api. Most rng's don't have flags, but some might, like
+ * the cprng which implements a 'test mode' for validation of vecotors
+ * which disables the internal continuity tests
+ */
+static int cprng_set_flags(struct crypto_rng *tfm, u8 flags)
+{
+ struct prng_context *prng = crypto_rng_ctx(tfm);
+
+ if (flags & CRYPTO_RNG_TEST_MODE)
+ prng->flags |= PRNG_DISABLE_CONT_TEST;
+
+ return 0;
+}
+
+ static int cprng_get_flags(struct crypto_rng *tfm, u8 *flags)
+{
+ struct prng_context *prng = crypto_rng_ctx(tfm);
+
+ *flags = 0;
+
+ if (prng->flags & PRNG_DISABLE_CONT_TEST)
+ *flags |= CRYPTO_RNG_TEST_MODE;
+
+ return 0;
+}
+
+
static struct crypto_alg rng_alg = {
.cra_name = "stdrng",
.cra_driver_name = "ansi_cprng",
@@ -399,6 +443,8 @@ static struct crypto_alg rng_alg = {
.rng = {
.rng_make_random = cprng_get_random,
.rng_reset = cprng_reset,
+ .rng_set_flags = cprng_set_flags,
+ .rng_get_flags = cprng_get_flags,
.seedsize = DEFAULT_PRNG_KSZ + 2*DEFAULT_BLK_SZ,
}
}
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