hostapd: SAE/EAP-pwd side-channel attack update
Fixes this security problem: * SAE/EAP-pwd side-channel attack update https://w1.fi/security/2019-6/sae-eap-pwd-side-channel-attack-update.txt Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>master
Hauke Mehrtens
5 years ago
parent
9f34bf51d6
commit
7bed9bf10f
@ -0,0 +1,40 @@
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From 92e1b96c26a84e503847bdd22ebadf697c4031ad Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <j@w1.fi>
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Date: Sat, 13 Apr 2019 17:20:57 +0300
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Subject: EAP-pwd: Disallow ECC groups with a prime under 256 bits
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Based on the SAE implementation guidance update to not allow ECC groups
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with a prime that is under 256 bits, reject groups 25, 26, and 27 in
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EAP-pwd.
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Signed-off-by: Jouni Malinen <j@w1.fi>
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---
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src/eap_common/eap_pwd_common.c | 13 +++++++++++++
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1 file changed, 13 insertions(+)
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--- a/src/eap_common/eap_pwd_common.c
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+++ b/src/eap_common/eap_pwd_common.c
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@@ -85,10 +85,23 @@ static int eap_pwd_kdf(const u8 *key, si
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}
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+static int eap_pwd_suitable_group(u16 num)
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+{
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+ /* Do not allow ECC groups with prime under 256 bits based on guidance
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+ * for the similar design in SAE. */
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+ return num == 19 || num == 20 || num == 21 ||
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+ num == 28 || num == 29 || num == 30;
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+}
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+
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+
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EAP_PWD_group * get_eap_pwd_group(u16 num)
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{
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EAP_PWD_group *grp;
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+ if (!eap_pwd_suitable_group(num)) {
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+ wpa_printf(MSG_INFO, "EAP-pwd: unsuitable group %u", num);
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+ return NULL;
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+ }
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grp = os_zalloc(sizeof(EAP_PWD_group));
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if (!grp)
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return NULL;
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@ -0,0 +1,54 @@
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From db54db11aec763b6fc74715c36e0f9de0d65e206 Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <jouni@codeaurora.org>
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Date: Mon, 8 Apr 2019 18:01:07 +0300
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Subject: SAE: Reject unsuitable groups based on REVmd changes
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The rules defining which DH groups are suitable for SAE use were
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accepted into IEEE 802.11 REVmd based on this document:
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https://mentor.ieee.org/802.11/dcn/19/11-19-0387-02-000m-addressing-some-sae-comments.docx
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Enforce those rules in production builds of wpa_supplicant and hostapd.
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CONFIG_TESTING_OPTIONS=y builds can still be used to select any o the
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implemented groups to maintain testing coverage.
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Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
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---
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src/common/sae.c | 23 +++++++++++++++++++++++
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1 file changed, 23 insertions(+)
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--- a/src/common/sae.c
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+++ b/src/common/sae.c
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@@ -18,10 +18,33 @@
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#include "sae.h"
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+static int sae_suitable_group(int group)
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+{
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+#ifdef CONFIG_TESTING_OPTIONS
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+ /* Allow all groups for testing purposes in non-production builds. */
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+ return 1;
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+#else /* CONFIG_TESTING_OPTIONS */
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+ /* Enforce REVmd rules on which SAE groups are suitable for production
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+ * purposes: FFC groups whose prime is >= 3072 bits and ECC groups
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+ * defined over a prime field whose prime is >= 256 bits. Furthermore,
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+ * ECC groups defined over a characteristic 2 finite field and ECC
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+ * groups with a co-factor greater than 1 are not suitable. */
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+ return group == 19 || group == 20 || group == 21 ||
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+ group == 28 || group == 29 || group == 30 ||
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+ group == 15 || group == 16 || group == 17 || group == 18;
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+#endif /* CONFIG_TESTING_OPTIONS */
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+}
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+
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+
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int sae_set_group(struct sae_data *sae, int group)
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{
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struct sae_temporary_data *tmp;
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+ if (!sae_suitable_group(group)) {
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+ wpa_printf(MSG_DEBUG, "SAE: Reject unsuitable group %d", group);
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+ return -1;
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+ }
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+
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sae_clear_data(sae);
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tmp = sae->tmp = os_zalloc(sizeof(*tmp));
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if (tmp == NULL)
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@ -0,0 +1,26 @@
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From e43f08991f00820c1f711ca254021d5f83b5cd7d Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <jouni@codeaurora.org>
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Date: Thu, 25 Apr 2019 18:52:34 +0300
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Subject: [PATCH 1/6] SAE: Use const_time_memcmp() for pwd_value >= prime
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comparison
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This reduces timing and memory access pattern differences for an
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operation that could depend on the used password.
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Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
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(cherry picked from commit 8e14b030e558d23f65d761895c07089404e61cf1)
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---
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src/common/sae.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/src/common/sae.c
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+++ b/src/common/sae.c
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@@ -317,7 +317,7 @@ static int sae_test_pwd_seed_ecc(struct
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wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
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pwd_value, sae->tmp->prime_len);
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- if (os_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
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+ if (const_time_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
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return 0;
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x_cand = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
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@ -0,0 +1,65 @@
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From 20d7bd83c43fb24c4cf84d3045254d3ee1957166 Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <jouni@codeaurora.org>
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Date: Thu, 25 Apr 2019 19:07:05 +0300
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Subject: [PATCH 2/6] EAP-pwd: Use const_time_memcmp() for pwd_value >= prime
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comparison
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This reduces timing and memory access pattern differences for an
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operation that could depend on the used password.
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Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
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(cherry picked from commit 7958223fdcfe82479e6ed71019a84f6d4cbf799c)
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---
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src/eap_common/eap_pwd_common.c | 13 ++++++++-----
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1 file changed, 8 insertions(+), 5 deletions(-)
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--- a/src/eap_common/eap_pwd_common.c
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+++ b/src/eap_common/eap_pwd_common.c
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@@ -144,6 +144,7 @@ int compute_password_element(EAP_PWD_gro
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u8 qnr_bin[MAX_ECC_PRIME_LEN];
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u8 qr_or_qnr_bin[MAX_ECC_PRIME_LEN];
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u8 x_bin[MAX_ECC_PRIME_LEN];
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+ u8 prime_bin[MAX_ECC_PRIME_LEN];
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struct crypto_bignum *tmp1 = NULL, *tmp2 = NULL, *pm1 = NULL;
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struct crypto_hash *hash;
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unsigned char pwe_digest[SHA256_MAC_LEN], *prfbuf = NULL, ctr;
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@@ -161,6 +162,11 @@ int compute_password_element(EAP_PWD_gro
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os_memset(x_bin, 0, sizeof(x_bin));
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prime = crypto_ec_get_prime(grp->group);
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+ primebitlen = crypto_ec_prime_len_bits(grp->group);
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+ primebytelen = crypto_ec_prime_len(grp->group);
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+ if (crypto_bignum_to_bin(prime, prime_bin, sizeof(prime_bin),
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+ primebytelen) < 0)
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+ return -1;
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cofactor = crypto_bignum_init();
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grp->pwe = crypto_ec_point_init(grp->group);
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tmp1 = crypto_bignum_init();
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@@ -176,8 +182,6 @@ int compute_password_element(EAP_PWD_gro
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"curve");
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goto fail;
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}
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- primebitlen = crypto_ec_prime_len_bits(grp->group);
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- primebytelen = crypto_ec_prime_len(grp->group);
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if ((prfbuf = os_malloc(primebytelen)) == NULL) {
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wpa_printf(MSG_INFO, "EAP-pwd: unable to malloc space for prf "
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"buffer");
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@@ -243,6 +247,8 @@ int compute_password_element(EAP_PWD_gro
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if (primebitlen % 8)
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buf_shift_right(prfbuf, primebytelen,
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8 - primebitlen % 8);
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+ if (const_time_memcmp(prfbuf, prime_bin, primebytelen) >= 0)
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+ continue;
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crypto_bignum_deinit(x_candidate, 1);
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x_candidate = crypto_bignum_init_set(prfbuf, primebytelen);
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@@ -252,9 +258,6 @@ int compute_password_element(EAP_PWD_gro
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goto fail;
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}
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- if (crypto_bignum_cmp(x_candidate, prime) >= 0)
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- continue;
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-
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wpa_hexdump_key(MSG_DEBUG, "EAP-pwd: x_candidate",
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prfbuf, primebytelen);
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const_time_select_bin(found, x_bin, prfbuf, primebytelen,
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@ -0,0 +1,61 @@
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From ee34d8cfbd0fbf7ba7429531d4bee1c43b074d8b Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <jouni@codeaurora.org>
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Date: Thu, 25 Apr 2019 19:23:05 +0300
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Subject: [PATCH 3/6] OpenSSL: Use BN_bn2binpad() or BN_bn2bin_padded() if
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available
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This converts crypto_bignum_to_bin() to use the OpenSSL/BoringSSL
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functions BN_bn2binpad()/BN_bn2bin_padded(), when available, to avoid
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differences in runtime and memory access patterns depending on the
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leading bytes of the BIGNUM value.
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OpenSSL 1.0.2 and LibreSSL do not include such functions, so those cases
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are still using the previous implementation where the BN_num_bytes()
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call may result in different memory access pattern.
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Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
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(cherry picked from commit 1e237903f5b5d3117342daf006c5878cdb45e3d3)
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---
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src/crypto/crypto_openssl.c | 16 ++++++++++++++++
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1 file changed, 16 insertions(+)
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--- a/src/crypto/crypto_openssl.c
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+++ b/src/crypto/crypto_openssl.c
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@@ -1227,7 +1227,13 @@ void crypto_bignum_deinit(struct crypto_
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int crypto_bignum_to_bin(const struct crypto_bignum *a,
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u8 *buf, size_t buflen, size_t padlen)
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{
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+#ifdef OPENSSL_IS_BORINGSSL
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+#else /* OPENSSL_IS_BORINGSSL */
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+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
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+#else
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int num_bytes, offset;
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+#endif
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+#endif /* OPENSSL_IS_BORINGSSL */
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if (TEST_FAIL())
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return -1;
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@@ -1235,6 +1241,14 @@ int crypto_bignum_to_bin(const struct cr
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if (padlen > buflen)
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return -1;
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+#ifdef OPENSSL_IS_BORINGSSL
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+ if (BN_bn2bin_padded(buf, padlen, (const BIGNUM *) a) == 0)
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+ return -1;
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+ return padlen;
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+#else /* OPENSSL_IS_BORINGSSL */
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+#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
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+ return BN_bn2binpad((const BIGNUM *) a, buf, padlen);
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+#else
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num_bytes = BN_num_bytes((const BIGNUM *) a);
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if ((size_t) num_bytes > buflen)
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return -1;
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@@ -1247,6 +1261,8 @@ int crypto_bignum_to_bin(const struct cr
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BN_bn2bin((const BIGNUM *) a, buf + offset);
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return num_bytes + offset;
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+#endif
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+#endif /* OPENSSL_IS_BORINGSSL */
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}
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@ -0,0 +1,54 @@
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From a25b48118d75f3c2d7cb1b2c3b4cffb13091a34c Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <j@w1.fi>
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Date: Mon, 24 Jun 2019 23:01:06 +0300
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Subject: [PATCH 4/6] SAE: Run through prf result processing even if it >=
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prime
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This reduces differences in timing and memory access within the
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hunting-and-pecking loop for ECC groups that have a prime that is not
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close to a power of two (e.g., Brainpool curves).
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Signed-off-by: Jouni Malinen <j@w1.fi>
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(cherry picked from commit 147bf7b88a9c231322b5b574263071ca6dbb0503)
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---
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src/common/sae.c | 15 ++++++++++++---
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1 file changed, 12 insertions(+), 3 deletions(-)
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--- a/src/common/sae.c
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+++ b/src/common/sae.c
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@@ -304,6 +304,8 @@ static int sae_test_pwd_seed_ecc(struct
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struct crypto_bignum *y_sqr, *x_cand;
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int res;
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size_t bits;
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+ int cmp_prime;
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+ unsigned int in_range;
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wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
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@@ -317,8 +319,13 @@ static int sae_test_pwd_seed_ecc(struct
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wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
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pwd_value, sae->tmp->prime_len);
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- if (const_time_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
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- return 0;
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+ cmp_prime = const_time_memcmp(pwd_value, prime, sae->tmp->prime_len);
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+ /* Create a const_time mask for selection based on prf result
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+ * being smaller than prime. */
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+ in_range = const_time_fill_msb((unsigned int) cmp_prime);
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+ /* The algorithm description would skip the next steps if
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+ * cmp_prime >= 0 (reutnr 0 here), but go through them regardless to
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+ * minimize externally observable differences in behavior. */
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x_cand = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
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if (!x_cand)
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@@ -330,7 +337,9 @@ static int sae_test_pwd_seed_ecc(struct
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res = is_quadratic_residue_blind(sae, prime, bits, qr, qnr, y_sqr);
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crypto_bignum_deinit(y_sqr, 1);
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- return res;
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+ if (res < 0)
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+ return res;
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+ return const_time_select_int(in_range, res, 0);
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}
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@ -0,0 +1,52 @@
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From 00a6cc73da61b03c146b6c341d0d1e572bcef432 Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <j@w1.fi>
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Date: Mon, 24 Jun 2019 23:02:51 +0300
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Subject: [PATCH 5/6] EAP-pwd: Run through prf result processing even if it >=
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prime
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This reduces differences in timing and memory access within the
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hunting-and-pecking loop for ECC groups that have a prime that is not
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close to a power of two (e.g., Brainpool curves).
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Signed-off-by: Jouni Malinen <j@w1.fi>
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(cherry picked from commit cd803299ca485eb857e37c88f973fccfbb8600e5)
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---
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src/eap_common/eap_pwd_common.c | 13 ++++++++++---
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1 file changed, 10 insertions(+), 3 deletions(-)
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--- a/src/eap_common/eap_pwd_common.c
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+++ b/src/eap_common/eap_pwd_common.c
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@@ -155,6 +155,8 @@ int compute_password_element(EAP_PWD_gro
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struct crypto_bignum *x_candidate = NULL, *cofactor = NULL;
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const struct crypto_bignum *prime;
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u8 mask, found_ctr = 0, is_odd = 0;
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+ int cmp_prime;
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+ unsigned int in_range;
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if (grp->pwe)
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return -1;
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@@ -247,8 +249,13 @@ int compute_password_element(EAP_PWD_gro
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if (primebitlen % 8)
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buf_shift_right(prfbuf, primebytelen,
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8 - primebitlen % 8);
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- if (const_time_memcmp(prfbuf, prime_bin, primebytelen) >= 0)
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- continue;
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+ cmp_prime = const_time_memcmp(prfbuf, prime_bin, primebytelen);
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+ /* Create a const_time mask for selection based on prf result
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+ * being smaller than prime. */
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+ in_range = const_time_fill_msb((unsigned int) cmp_prime);
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+ /* The algorithm description would skip the next steps if
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+ * cmp_prime >= 0, but go through them regardless to minimize
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+ * externally observable differences in behavior. */
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crypto_bignum_deinit(x_candidate, 1);
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x_candidate = crypto_bignum_init_set(prfbuf, primebytelen);
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@@ -311,7 +318,7 @@ int compute_password_element(EAP_PWD_gro
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goto fail;
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mask = const_time_eq(res, check);
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found_ctr = const_time_select_u8(found, found_ctr, ctr);
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- found |= mask;
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+ found |= mask & in_range;
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}
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if (found == 0) {
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wpa_printf(MSG_INFO,
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@ -0,0 +1,44 @@
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From 558518ed63202e5358116ab7e0afd5e85490f2ef Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <j@w1.fi>
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Date: Sat, 27 Jul 2019 23:19:17 +0300
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Subject: [PATCH 6/6] dragonfly: Disable use of groups using Brainpool curves
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Disable groups that use Brainpool curves for now since they leak more
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timing information due to the prime not being close to a power of two.
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This removes use of groups 28, 29, and 30 from SAE and EAP-pwd.
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Signed-off-by: Jouni Malinen <j@w1.fi>
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(cherry picked from commit 876c5eaa6dae1a87a17603fc489a44c29eedc2e3)
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---
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src/common/sae.c | 6 ++++--
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src/eap_common/eap_pwd_common.c | 3 +--
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2 files changed, 5 insertions(+), 4 deletions(-)
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--- a/src/common/sae.c
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+++ b/src/common/sae.c
|
||||
@@ -28,9 +28,11 @@ static int sae_suitable_group(int group)
|
||||
* purposes: FFC groups whose prime is >= 3072 bits and ECC groups
|
||||
* defined over a prime field whose prime is >= 256 bits. Furthermore,
|
||||
* ECC groups defined over a characteristic 2 finite field and ECC
|
||||
- * groups with a co-factor greater than 1 are not suitable. */
|
||||
+ * groups with a co-factor greater than 1 are not suitable. Disable
|
||||
+ * groups that use Brainpool curves as well for now since they leak more
|
||||
+ * timing information due to the prime not being close to a power of
|
||||
+ * two. */
|
||||
return group == 19 || group == 20 || group == 21 ||
|
||||
- group == 28 || group == 29 || group == 30 ||
|
||||
group == 15 || group == 16 || group == 17 || group == 18;
|
||||
#endif /* CONFIG_TESTING_OPTIONS */
|
||||
}
|
||||
--- a/src/eap_common/eap_pwd_common.c
|
||||
+++ b/src/eap_common/eap_pwd_common.c
|
||||
@@ -89,8 +89,7 @@ static int eap_pwd_suitable_group(u16 nu
|
||||
{
|
||||
/* Do not allow ECC groups with prime under 256 bits based on guidance
|
||||
* for the similar design in SAE. */
|
||||
- return num == 19 || num == 20 || num == 21 ||
|
||||
- num == 28 || num == 29 || num == 30;
|
||||
+ return num == 19 || num == 20 || num == 21;
|
||||
}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue