hostapd: SAE/EAP-pwd side-channel attack update
authorHauke Mehrtens <hauke@hauke-m.de>
Sun, 8 Sep 2019 21:53:18 +0000 (23:53 +0200)
committerHauke Mehrtens <hauke@hauke-m.de>
Tue, 10 Sep 2019 19:51:41 +0000 (21:51 +0200)
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>
package/network/services/hostapd/Makefile
package/network/services/hostapd/patches/066-0000-EAP-pwd-Disallow-ECC-groups-with-a-prime-under-256-b.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0000-SAE-Reject-unsuitable-groups-based-on-REVmd-changes.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0001-SAE-Use-const_time_memcmp-for-pwd_value-prime-compar.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0002-EAP-pwd-Use-const_time_memcmp-for-pwd_value-prime-co.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0003-OpenSSL-Use-BN_bn2binpad-or-BN_bn2bin_padded-if-avai.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0004-SAE-Run-through-prf-result-processing-even-if-it-pri.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0005-EAP-pwd-Run-through-prf-result-processing-even-if-it.patch [new file with mode: 0644]
package/network/services/hostapd/patches/066-0006-dragonfly-Disable-use-of-groups-using-Brainpool-curv.patch [new file with mode: 0644]

index 18e4ea44906c9f127db94121a4d0adb577026456..233ef389ae50e13d42e2ec9cfeecfb6e2ee462a5 100644 (file)
@@ -7,7 +7,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=hostapd
-PKG_RELEASE:=8
+PKG_RELEASE:=9
 
 PKG_SOURCE_URL:=http://w1.fi/hostap.git
 PKG_SOURCE_PROTO:=git
diff --git a/package/network/services/hostapd/patches/066-0000-EAP-pwd-Disallow-ECC-groups-with-a-prime-under-256-b.patch b/package/network/services/hostapd/patches/066-0000-EAP-pwd-Disallow-ECC-groups-with-a-prime-under-256-b.patch
new file mode 100644 (file)
index 0000000..2d40516
--- /dev/null
@@ -0,0 +1,40 @@
+From 92e1b96c26a84e503847bdd22ebadf697c4031ad Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <j@w1.fi>
+Date: Sat, 13 Apr 2019 17:20:57 +0300
+Subject: EAP-pwd: Disallow ECC groups with a prime under 256 bits
+
+Based on the SAE implementation guidance update to not allow ECC groups
+with a prime that is under 256 bits, reject groups 25, 26, and 27 in
+EAP-pwd.
+
+Signed-off-by: Jouni Malinen <j@w1.fi>
+---
+ src/eap_common/eap_pwd_common.c | 13 +++++++++++++
+ 1 file changed, 13 insertions(+)
+
+--- a/src/eap_common/eap_pwd_common.c
++++ b/src/eap_common/eap_pwd_common.c
+@@ -85,10 +85,23 @@ static int eap_pwd_kdf(const u8 *key, si
+ }
++static int eap_pwd_suitable_group(u16 num)
++{
++      /* 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;
++}
++
++
+ EAP_PWD_group * get_eap_pwd_group(u16 num)
+ {
+       EAP_PWD_group *grp;
++      if (!eap_pwd_suitable_group(num)) {
++              wpa_printf(MSG_INFO, "EAP-pwd: unsuitable group %u", num);
++              return NULL;
++      }
+       grp = os_zalloc(sizeof(EAP_PWD_group));
+       if (!grp)
+               return NULL;
diff --git a/package/network/services/hostapd/patches/066-0000-SAE-Reject-unsuitable-groups-based-on-REVmd-changes.patch b/package/network/services/hostapd/patches/066-0000-SAE-Reject-unsuitable-groups-based-on-REVmd-changes.patch
new file mode 100644 (file)
index 0000000..e1e743f
--- /dev/null
@@ -0,0 +1,54 @@
+From db54db11aec763b6fc74715c36e0f9de0d65e206 Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <jouni@codeaurora.org>
+Date: Mon, 8 Apr 2019 18:01:07 +0300
+Subject: SAE: Reject unsuitable groups based on REVmd changes
+
+The rules defining which DH groups are suitable for SAE use were
+accepted into IEEE 802.11 REVmd based on this document:
+https://mentor.ieee.org/802.11/dcn/19/11-19-0387-02-000m-addressing-some-sae-comments.docx
+
+Enforce those rules in production builds of wpa_supplicant and hostapd.
+CONFIG_TESTING_OPTIONS=y builds can still be used to select any o the
+implemented groups to maintain testing coverage.
+
+Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
+---
+ src/common/sae.c | 23 +++++++++++++++++++++++
+ 1 file changed, 23 insertions(+)
+
+--- a/src/common/sae.c
++++ b/src/common/sae.c
+@@ -18,10 +18,33 @@
+ #include "sae.h"
++static int sae_suitable_group(int group)
++{
++#ifdef CONFIG_TESTING_OPTIONS
++      /* Allow all groups for testing purposes in non-production builds. */
++      return 1;
++#else /* CONFIG_TESTING_OPTIONS */
++      /* Enforce REVmd rules on which SAE groups are suitable for production
++       * 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. */
++      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 */
++}
++
++
+ int sae_set_group(struct sae_data *sae, int group)
+ {
+       struct sae_temporary_data *tmp;
++      if (!sae_suitable_group(group)) {
++              wpa_printf(MSG_DEBUG, "SAE: Reject unsuitable group %d", group);
++              return -1;
++      }
++
+       sae_clear_data(sae);
+       tmp = sae->tmp = os_zalloc(sizeof(*tmp));
+       if (tmp == NULL)
diff --git a/package/network/services/hostapd/patches/066-0001-SAE-Use-const_time_memcmp-for-pwd_value-prime-compar.patch b/package/network/services/hostapd/patches/066-0001-SAE-Use-const_time_memcmp-for-pwd_value-prime-compar.patch
new file mode 100644 (file)
index 0000000..d637a52
--- /dev/null
@@ -0,0 +1,26 @@
+From e43f08991f00820c1f711ca254021d5f83b5cd7d Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <jouni@codeaurora.org>
+Date: Thu, 25 Apr 2019 18:52:34 +0300
+Subject: [PATCH 1/6] SAE: Use const_time_memcmp() for pwd_value >= prime
+ comparison
+
+This reduces timing and memory access pattern differences for an
+operation that could depend on the used password.
+
+Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
+(cherry picked from commit 8e14b030e558d23f65d761895c07089404e61cf1)
+---
+ src/common/sae.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/src/common/sae.c
++++ b/src/common/sae.c
+@@ -317,7 +317,7 @@ static int sae_test_pwd_seed_ecc(struct
+       wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
+                       pwd_value, sae->tmp->prime_len);
+-      if (os_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
++      if (const_time_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
+               return 0;
+       x_cand = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
diff --git a/package/network/services/hostapd/patches/066-0002-EAP-pwd-Use-const_time_memcmp-for-pwd_value-prime-co.patch b/package/network/services/hostapd/patches/066-0002-EAP-pwd-Use-const_time_memcmp-for-pwd_value-prime-co.patch
new file mode 100644 (file)
index 0000000..6bbda2b
--- /dev/null
@@ -0,0 +1,65 @@
+From 20d7bd83c43fb24c4cf84d3045254d3ee1957166 Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <jouni@codeaurora.org>
+Date: Thu, 25 Apr 2019 19:07:05 +0300
+Subject: [PATCH 2/6] EAP-pwd: Use const_time_memcmp() for pwd_value >= prime
+ comparison
+
+This reduces timing and memory access pattern differences for an
+operation that could depend on the used password.
+
+Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
+(cherry picked from commit 7958223fdcfe82479e6ed71019a84f6d4cbf799c)
+---
+ src/eap_common/eap_pwd_common.c | 13 ++++++++-----
+ 1 file changed, 8 insertions(+), 5 deletions(-)
+
+--- a/src/eap_common/eap_pwd_common.c
++++ b/src/eap_common/eap_pwd_common.c
+@@ -144,6 +144,7 @@ int compute_password_element(EAP_PWD_gro
+       u8 qnr_bin[MAX_ECC_PRIME_LEN];
+       u8 qr_or_qnr_bin[MAX_ECC_PRIME_LEN];
+       u8 x_bin[MAX_ECC_PRIME_LEN];
++      u8 prime_bin[MAX_ECC_PRIME_LEN];
+       struct crypto_bignum *tmp1 = NULL, *tmp2 = NULL, *pm1 = NULL;
+       struct crypto_hash *hash;
+       unsigned char pwe_digest[SHA256_MAC_LEN], *prfbuf = NULL, ctr;
+@@ -161,6 +162,11 @@ int compute_password_element(EAP_PWD_gro
+       os_memset(x_bin, 0, sizeof(x_bin));
+       prime = crypto_ec_get_prime(grp->group);
++      primebitlen = crypto_ec_prime_len_bits(grp->group);
++      primebytelen = crypto_ec_prime_len(grp->group);
++      if (crypto_bignum_to_bin(prime, prime_bin, sizeof(prime_bin),
++                               primebytelen) < 0)
++              return -1;
+       cofactor = crypto_bignum_init();
+       grp->pwe = crypto_ec_point_init(grp->group);
+       tmp1 = crypto_bignum_init();
+@@ -176,8 +182,6 @@ int compute_password_element(EAP_PWD_gro
+                          "curve");
+               goto fail;
+       }
+-      primebitlen = crypto_ec_prime_len_bits(grp->group);
+-      primebytelen = crypto_ec_prime_len(grp->group);
+       if ((prfbuf = os_malloc(primebytelen)) == NULL) {
+               wpa_printf(MSG_INFO, "EAP-pwd: unable to malloc space for prf "
+                          "buffer");
+@@ -243,6 +247,8 @@ int compute_password_element(EAP_PWD_gro
+               if (primebitlen % 8)
+                       buf_shift_right(prfbuf, primebytelen,
+                                       8 - primebitlen % 8);
++              if (const_time_memcmp(prfbuf, prime_bin, primebytelen) >= 0)
++                      continue;
+               crypto_bignum_deinit(x_candidate, 1);
+               x_candidate = crypto_bignum_init_set(prfbuf, primebytelen);
+@@ -252,9 +258,6 @@ int compute_password_element(EAP_PWD_gro
+                       goto fail;
+               }
+-              if (crypto_bignum_cmp(x_candidate, prime) >= 0)
+-                      continue;
+-
+               wpa_hexdump_key(MSG_DEBUG, "EAP-pwd: x_candidate",
+                               prfbuf, primebytelen);
+               const_time_select_bin(found, x_bin, prfbuf, primebytelen,
diff --git a/package/network/services/hostapd/patches/066-0003-OpenSSL-Use-BN_bn2binpad-or-BN_bn2bin_padded-if-avai.patch b/package/network/services/hostapd/patches/066-0003-OpenSSL-Use-BN_bn2binpad-or-BN_bn2bin_padded-if-avai.patch
new file mode 100644 (file)
index 0000000..67684cb
--- /dev/null
@@ -0,0 +1,61 @@
+From ee34d8cfbd0fbf7ba7429531d4bee1c43b074d8b Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <jouni@codeaurora.org>
+Date: Thu, 25 Apr 2019 19:23:05 +0300
+Subject: [PATCH 3/6] OpenSSL: Use BN_bn2binpad() or BN_bn2bin_padded() if
+ available
+
+This converts crypto_bignum_to_bin() to use the OpenSSL/BoringSSL
+functions BN_bn2binpad()/BN_bn2bin_padded(), when available, to avoid
+differences in runtime and memory access patterns depending on the
+leading bytes of the BIGNUM value.
+
+OpenSSL 1.0.2 and LibreSSL do not include such functions, so those cases
+are still using the previous implementation where the BN_num_bytes()
+call may result in different memory access pattern.
+
+Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
+(cherry picked from commit 1e237903f5b5d3117342daf006c5878cdb45e3d3)
+---
+ src/crypto/crypto_openssl.c | 16 ++++++++++++++++
+ 1 file changed, 16 insertions(+)
+
+--- a/src/crypto/crypto_openssl.c
++++ b/src/crypto/crypto_openssl.c
+@@ -1227,7 +1227,13 @@ void crypto_bignum_deinit(struct crypto_
+ int crypto_bignum_to_bin(const struct crypto_bignum *a,
+                        u8 *buf, size_t buflen, size_t padlen)
+ {
++#ifdef OPENSSL_IS_BORINGSSL
++#else /* OPENSSL_IS_BORINGSSL */
++#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
++#else
+       int num_bytes, offset;
++#endif
++#endif /* OPENSSL_IS_BORINGSSL */
+       if (TEST_FAIL())
+               return -1;
+@@ -1235,6 +1241,14 @@ int crypto_bignum_to_bin(const struct cr
+       if (padlen > buflen)
+               return -1;
++#ifdef OPENSSL_IS_BORINGSSL
++      if (BN_bn2bin_padded(buf, padlen, (const BIGNUM *) a) == 0)
++              return -1;
++      return padlen;
++#else /* OPENSSL_IS_BORINGSSL */
++#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
++      return BN_bn2binpad((const BIGNUM *) a, buf, padlen);
++#else
+       num_bytes = BN_num_bytes((const BIGNUM *) a);
+       if ((size_t) num_bytes > buflen)
+               return -1;
+@@ -1247,6 +1261,8 @@ int crypto_bignum_to_bin(const struct cr
+       BN_bn2bin((const BIGNUM *) a, buf + offset);
+       return num_bytes + offset;
++#endif
++#endif /* OPENSSL_IS_BORINGSSL */
+ }
diff --git a/package/network/services/hostapd/patches/066-0004-SAE-Run-through-prf-result-processing-even-if-it-pri.patch b/package/network/services/hostapd/patches/066-0004-SAE-Run-through-prf-result-processing-even-if-it-pri.patch
new file mode 100644 (file)
index 0000000..7337cb3
--- /dev/null
@@ -0,0 +1,54 @@
+From a25b48118d75f3c2d7cb1b2c3b4cffb13091a34c Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <j@w1.fi>
+Date: Mon, 24 Jun 2019 23:01:06 +0300
+Subject: [PATCH 4/6] SAE: Run through prf result processing even if it >=
+ prime
+
+This reduces differences in timing and memory access within the
+hunting-and-pecking loop for ECC groups that have a prime that is not
+close to a power of two (e.g., Brainpool curves).
+
+Signed-off-by: Jouni Malinen <j@w1.fi>
+(cherry picked from commit 147bf7b88a9c231322b5b574263071ca6dbb0503)
+---
+ src/common/sae.c | 15 ++++++++++++---
+ 1 file changed, 12 insertions(+), 3 deletions(-)
+
+--- a/src/common/sae.c
++++ b/src/common/sae.c
+@@ -304,6 +304,8 @@ static int sae_test_pwd_seed_ecc(struct
+       struct crypto_bignum *y_sqr, *x_cand;
+       int res;
+       size_t bits;
++      int cmp_prime;
++      unsigned int in_range;
+       wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-seed", pwd_seed, SHA256_MAC_LEN);
+@@ -317,8 +319,13 @@ static int sae_test_pwd_seed_ecc(struct
+       wpa_hexdump_key(MSG_DEBUG, "SAE: pwd-value",
+                       pwd_value, sae->tmp->prime_len);
+-      if (const_time_memcmp(pwd_value, prime, sae->tmp->prime_len) >= 0)
+-              return 0;
++      cmp_prime = const_time_memcmp(pwd_value, prime, sae->tmp->prime_len);
++      /* Create a const_time mask for selection based on prf result
++       * being smaller than prime. */
++      in_range = const_time_fill_msb((unsigned int) cmp_prime);
++      /* The algorithm description would skip the next steps if
++       * cmp_prime >= 0 (reutnr 0 here), but go through them regardless to
++       * minimize externally observable differences in behavior. */
+       x_cand = crypto_bignum_init_set(pwd_value, sae->tmp->prime_len);
+       if (!x_cand)
+@@ -330,7 +337,9 @@ static int sae_test_pwd_seed_ecc(struct
+       res = is_quadratic_residue_blind(sae, prime, bits, qr, qnr, y_sqr);
+       crypto_bignum_deinit(y_sqr, 1);
+-      return res;
++      if (res < 0)
++              return res;
++      return const_time_select_int(in_range, res, 0);
+ }
diff --git a/package/network/services/hostapd/patches/066-0005-EAP-pwd-Run-through-prf-result-processing-even-if-it.patch b/package/network/services/hostapd/patches/066-0005-EAP-pwd-Run-through-prf-result-processing-even-if-it.patch
new file mode 100644 (file)
index 0000000..9ad4747
--- /dev/null
@@ -0,0 +1,52 @@
+From 00a6cc73da61b03c146b6c341d0d1e572bcef432 Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <j@w1.fi>
+Date: Mon, 24 Jun 2019 23:02:51 +0300
+Subject: [PATCH 5/6] EAP-pwd: Run through prf result processing even if it >=
+ prime
+
+This reduces differences in timing and memory access within the
+hunting-and-pecking loop for ECC groups that have a prime that is not
+close to a power of two (e.g., Brainpool curves).
+
+Signed-off-by: Jouni Malinen <j@w1.fi>
+(cherry picked from commit cd803299ca485eb857e37c88f973fccfbb8600e5)
+---
+ src/eap_common/eap_pwd_common.c | 13 ++++++++++---
+ 1 file changed, 10 insertions(+), 3 deletions(-)
+
+--- a/src/eap_common/eap_pwd_common.c
++++ b/src/eap_common/eap_pwd_common.c
+@@ -155,6 +155,8 @@ int compute_password_element(EAP_PWD_gro
+       struct crypto_bignum *x_candidate = NULL, *cofactor = NULL;
+       const struct crypto_bignum *prime;
+       u8 mask, found_ctr = 0, is_odd = 0;
++      int cmp_prime;
++      unsigned int in_range;
+       if (grp->pwe)
+               return -1;
+@@ -247,8 +249,13 @@ int compute_password_element(EAP_PWD_gro
+               if (primebitlen % 8)
+                       buf_shift_right(prfbuf, primebytelen,
+                                       8 - primebitlen % 8);
+-              if (const_time_memcmp(prfbuf, prime_bin, primebytelen) >= 0)
+-                      continue;
++              cmp_prime = const_time_memcmp(prfbuf, prime_bin, primebytelen);
++              /* Create a const_time mask for selection based on prf result
++               * being smaller than prime. */
++              in_range = const_time_fill_msb((unsigned int) cmp_prime);
++              /* The algorithm description would skip the next steps if
++               * cmp_prime >= 0, but go through them regardless to minimize
++               * externally observable differences in behavior. */
+               crypto_bignum_deinit(x_candidate, 1);
+               x_candidate = crypto_bignum_init_set(prfbuf, primebytelen);
+@@ -311,7 +318,7 @@ int compute_password_element(EAP_PWD_gro
+                       goto fail;
+               mask = const_time_eq(res, check);
+               found_ctr = const_time_select_u8(found, found_ctr, ctr);
+-              found |= mask;
++              found |= mask & in_range;
+       }
+       if (found == 0) {
+               wpa_printf(MSG_INFO,
diff --git a/package/network/services/hostapd/patches/066-0006-dragonfly-Disable-use-of-groups-using-Brainpool-curv.patch b/package/network/services/hostapd/patches/066-0006-dragonfly-Disable-use-of-groups-using-Brainpool-curv.patch
new file mode 100644 (file)
index 0000000..28555bb
--- /dev/null
@@ -0,0 +1,44 @@
+From 558518ed63202e5358116ab7e0afd5e85490f2ef Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <j@w1.fi>
+Date: Sat, 27 Jul 2019 23:19:17 +0300
+Subject: [PATCH 6/6] dragonfly: Disable use of groups using Brainpool curves
+
+Disable groups that use Brainpool curves for now since they leak more
+timing information due to the prime not being close to a power of two.
+This removes use of groups 28, 29, and 30 from SAE and EAP-pwd.
+
+Signed-off-by: Jouni Malinen <j@w1.fi>
+(cherry picked from commit 876c5eaa6dae1a87a17603fc489a44c29eedc2e3)
+---
+ src/common/sae.c                | 6 ++++--
+ src/eap_common/eap_pwd_common.c | 3 +--
+ 2 files changed, 5 insertions(+), 4 deletions(-)
+
+--- a/src/common/sae.c
++++ 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;
+ }