Use mgf1_bitspender in ntru_poly_create_from_seed

2 files changed, 16 insertions, 52 deletions

diff --git a/src/libstrongswan/plugins/ntru/ntru_poly.c b/src/libstrongswan/plugins/ntru/ntru_poly.c
index e5089737c..b5b3898f2 100644
--- a/src/libstrongswan/plugins/ntru/ntru_poly.c
+++ b/src/libstrongswan/plugins/ntru/ntru_poly.c
@@ -17,7 +17,7 @@
 
 #include "ntru_poly.h"
 
-#include <crypto/mgf1/mgf1.h>
+#include <crypto/mgf1/mgf1_bitspender.h>
 #include <utils/debug.h>
 #include <utils/test.h>
 
@@ -297,22 +297,17 @@ ntru_poly_t *ntru_poly_create_from_seed(hash_algorithm_t alg, chunk_t seed,
 										bool is_product_form)
 {
 	private_ntru_poly_t *this;
-	size_t hash_len, octet_count = 0, i;
-	uint8_t octets[HASH_SIZE_SHA512], *used, num_left = 0, num_needed;
-	uint16_t index, limit, left = 0;
 	int n, num_indices, index_i = 0;
-	mgf1_t *mgf1;
+	uint32_t index, limit;
+	uint8_t *used;
+	mgf1_bitspender_t *bitspender;
 
-	DBG2(DBG_LIB, "MGF1 is seeded with %u bytes", seed.len);
-	mgf1 = mgf1_create(alg, seed, TRUE);
-	if (!mgf1)
+	bitspender = mgf1_bitspender_create(alg, seed, TRUE);
+	if (!bitspender)
 	{
 	    return NULL;
 	}
-	i = hash_len = mgf1->get_hash_size(mgf1);
-
 	this = ntru_poly_create(N, q, indices_len_p, indices_len_m, is_product_form);
-
 	used = malloc(N);
 	limit = N * ((1 << c_bits) / N);
 
@@ -328,43 +323,13 @@ ntru_poly_t *ntru_poly_create_from_seed(hash_algorithm_t alg, chunk_t seed,
 			/* generate a random candidate index with a size of c_bits */		
 			do
 			{
-				/* use any leftover bits first */
-				index = num_left ? left << (c_bits - num_left) : 0;
-
-				/* get the rest of the bits needed from new octets */
-				num_needed = c_bits - num_left;
-
-				while (num_needed)
+				index = bitspender->get_bits(bitspender, c_bits);
+				if (index == MGF1_BITSPENDER_ERROR)
 				{
-					if (i == hash_len)
-					{
-						/* get another block from MGF1 */
-						if (!mgf1->get_mask(mgf1, hash_len, octets))
-						{
-							mgf1->destroy(mgf1);
-							destroy(this);
-							free(used);
-							return NULL;
-						}
-						octet_count += hash_len;
-						i = 0;
-					}
-					left = octets[i++];
-
-					if (num_needed <= 8)
-					{
-						/* all bits needed to fill the index are in this octet */
-						index |= left >> (8 - num_needed);
-						num_left = 8 - num_needed;
-						num_needed = 0;
-						left &= 0xff >> (8 - num_left);
-					}
-					else
-					{
-						/* more than one octet will be needed */
-						index |= left << (num_needed - 8);
-						num_needed -= 8;
-					}
+					bitspender->destroy(bitspender);
+					destroy(this);
+					free(used);
+					return NULL;
 				}
 			}
 			while (index >= limit);
@@ -380,9 +345,7 @@ ntru_poly_t *ntru_poly_create_from_seed(hash_algorithm_t alg, chunk_t seed,
 		}
 	}
 
-	DBG2(DBG_LIB, "MGF1 generates %u octets to derive %u indices",
-				   octet_count, this->num_indices);
-	mgf1->destroy(mgf1);
+	bitspender->destroy(bitspender);
 	free(used);
 
 	return &this->public;
diff --git a/src/libstrongswan/plugins/ntru/ntru_trits.c b/src/libstrongswan/plugins/ntru/ntru_trits.c
index 83d1939ed..5d8fc599d 100644
--- a/src/libstrongswan/plugins/ntru/ntru_trits.c
+++ b/src/libstrongswan/plugins/ntru/ntru_trits.c
@@ -74,7 +74,8 @@ ntru_trits_t *ntru_trits_create(size_t len, hash_algorithm_t alg, chunk_t seed)
 	size_t hash_len, octet_count = 0, trits_needed, i;
 	mgf1_t *mgf1;
 
-	DBG2(DBG_LIB, "MGF1 is seeded with %u bytes", seed.len);
+	DBG2(DBG_LIB, "mgf1 based on %N is seeded with %u octets",
+		 hash_algorithm_short_names, alg, seed.len);
 	mgf1 = mgf1_create(alg, seed, TRUE);
 	if (!mgf1)
 	{
@@ -122,7 +123,7 @@ ntru_trits_t *ntru_trits_create(size_t len, hash_algorithm_t alg, chunk_t seed)
 		}
 		i++;
 	}
-	DBG2(DBG_LIB, "MGF1 generates %u octets to extract %u trits",
+	DBG2(DBG_LIB, "mgf1 generated %u octets to extract %u trits",
 				   octet_count, len);
 	mgf1->destroy(mgf1);