Share common SAE and EAP-pwd functionality: random qr/qnr creation

Use a shared helper function to create random qr/qnr values.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/common/dragonfly.c

@@ -10,6 +10,7 @@
 #include "utils/includes.h"
 
 #include "utils/common.h"
+#include "crypto/crypto.h"
 #include "dragonfly.h"
 
 
@@ -25,3 +26,35 @@ int dragonfly_suitable_group(int group, int ecc_only)
 		(!ecc_only &&
 		 (group == 15 || group == 16 || group == 17 || group == 18));
 }
+
+
+int dragonfly_get_random_qr_qnr(const struct crypto_bignum *prime,
+				struct crypto_bignum **qr,
+				struct crypto_bignum **qnr)
+{
+	*qr = *qnr = NULL;
+
+	while (!(*qr) || !(*qnr)) {
+		struct crypto_bignum *tmp;
+		int res;
+
+		tmp = crypto_bignum_init();
+		if (!tmp || crypto_bignum_rand(tmp, prime) < 0)
+			break;
+
+		res = crypto_bignum_legendre(tmp, prime);
+		if (res == 1 && !(*qr))
+			*qr = tmp;
+		else if (res == -1 && !(*qnr))
+			*qnr = tmp;
+		else
+			crypto_bignum_deinit(tmp, 0);
+	}
+
+	if (*qr && *qnr)
+		return 0;
+	crypto_bignum_deinit(*qr, 0);
+	crypto_bignum_deinit(*qnr, 0);
+	*qr = *qnr = NULL;
+	return -1;
+}

src/common/dragonfly.h

@@ -10,6 +10,11 @@
 #ifndef DRAGONFLY_H
 #define DRAGONFLY_H
 
+struct crypto_bignum;
+
 int dragonfly_suitable_group(int group, int ecc_only);
+int dragonfly_get_random_qr_qnr(const struct crypto_bignum *prime,
+				struct crypto_bignum **qr,
+				struct crypto_bignum **qnr);
 
 #endif /* DRAGONFLY_H */

src/common/sae.c

@@ -401,42 +401,6 @@ fail:
 }
 
 
-static int get_random_qr_qnr(const u8 *prime, size_t prime_len,
-			     const struct crypto_bignum *prime_bn,
-			     size_t prime_bits, struct crypto_bignum **qr,
-			     struct crypto_bignum **qnr)
-{
-	*qr = NULL;
-	*qnr = NULL;
-
-	while (!(*qr) || !(*qnr)) {
-		u8 tmp[SAE_MAX_ECC_PRIME_LEN];
-		struct crypto_bignum *q;
-		int res;
-
-		if (random_get_bytes(tmp, prime_len) < 0)
-			break;
-		if (prime_bits % 8)
-			buf_shift_right(tmp, prime_len, 8 - prime_bits % 8);
-		if (os_memcmp(tmp, prime, prime_len) >= 0)
-			continue;
-		q = crypto_bignum_init_set(tmp, prime_len);
-		if (!q)
-			break;
-		res = crypto_bignum_legendre(q, prime_bn);
-
-		if (res == 1 && !(*qr))
-			*qr = q;
-		else if (res == -1 && !(*qnr))
-			*qnr = q;
-		else
-			crypto_bignum_deinit(q, 0);
-	}
-
-	return (*qr && *qnr) ? 0 : -1;
-}
-
-
 static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
 			      const u8 *addr2, const u8 *password,
 			      size_t password_len, const char *identifier)
@@ -455,7 +419,6 @@ static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
 	u8 x_cand_bin[SAE_MAX_ECC_PRIME_LEN];
 	u8 qr_bin[SAE_MAX_ECC_PRIME_LEN];
 	u8 qnr_bin[SAE_MAX_ECC_PRIME_LEN];
-	size_t bits;
 	int res = -1;
 	u8 found = 0; /* 0 (false) or 0xff (true) to be used as const_time_*
 		       * mask */
@@ -472,14 +435,12 @@ static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
 	if (crypto_bignum_to_bin(sae->tmp->prime, prime, sizeof(prime),
 				 prime_len) < 0)
 		goto fail;
-	bits = crypto_ec_prime_len_bits(sae->tmp->ec);
 
 	/*
 	 * Create a random quadratic residue (qr) and quadratic non-residue
 	 * (qnr) modulo p for blinding purposes during the loop.
 	 */
-	if (get_random_qr_qnr(prime, prime_len, sae->tmp->prime, bits,
-			      &qr, &qnr) < 0 ||
+	if (dragonfly_get_random_qr_qnr(sae->tmp->prime, &qr, &qnr) < 0 ||
 	    crypto_bignum_to_bin(qr, qr_bin, sizeof(qr_bin), prime_len) < 0 ||
 	    crypto_bignum_to_bin(qnr, qnr_bin, sizeof(qnr_bin), prime_len) < 0)
 		goto fail;

src/eap_common/eap_pwd_common.c

@@ -168,21 +168,8 @@ int compute_password_element(EAP_PWD_group *grp, u16 num,
 		goto fail;
 
 	/* get a random quadratic residue and nonresidue */
-	while (!qr || !qnr) {
-		if (crypto_bignum_rand(tmp1, prime) < 0)
-			goto fail;
-		res = crypto_bignum_legendre(tmp1, prime);
-		if (!qr && res == 1) {
-			qr = tmp1;
-			tmp1 = crypto_bignum_init();
-		} else if (!qnr && res == -1) {
-			qnr = tmp1;
-			tmp1 = crypto_bignum_init();
-		}
-		if (!tmp1)
-			goto fail;
-	}
-	if (crypto_bignum_to_bin(qr, qr_bin, sizeof(qr_bin),
+	if (dragonfly_get_random_qr_qnr(prime, &qr, &qnr) < 0 ||
+	    crypto_bignum_to_bin(qr, qr_bin, sizeof(qr_bin),
 				 primebytelen) < 0 ||
 	    crypto_bignum_to_bin(qnr, qnr_bin, sizeof(qnr_bin),
 				 primebytelen) < 0)