diff options
Diffstat (limited to 'main/hostapd/0005-SAE-Mask-timing-of-MODP-groups-22-23-24.patch')
| -rw-r--r-- | main/hostapd/0005-SAE-Mask-timing-of-MODP-groups-22-23-24.patch | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/main/hostapd/0005-SAE-Mask-timing-of-MODP-groups-22-23-24.patch b/main/hostapd/0005-SAE-Mask-timing-of-MODP-groups-22-23-24.patch new file mode 100644 index 0000000000..11dc244f5f --- /dev/null +++ b/main/hostapd/0005-SAE-Mask-timing-of-MODP-groups-22-23-24.patch @@ -0,0 +1,118 @@ +From 90839597cc4016b33f00055b12d59174c62770a3 Mon Sep 17 00:00:00 2001 +From: Jouni Malinen <jouni@codeaurora.org> +Date: Sat, 2 Mar 2019 12:24:09 +0200 +Subject: [PATCH] SAE: Mask timing of MODP groups 22, 23, 24 + +These groups have significant probability of coming up with pwd-value +that is equal or greater than the prime and as such, need for going +through the PWE derivation loop multiple times. This can result in +sufficient timing different to allow an external observer to determine +how many rounds are needed and that can leak information about the used +password. + +Force at least 40 loop rounds for these MODP groups similarly to the ECC +group design to mask timing. This behavior is not described in IEEE Std +802.11-2016 for SAE, but it does not result in different values (i.e., +only different timing), so such implementation specific countermeasures +can be done without breaking interoperability with other implementation. + +Note: These MODP groups 22, 23, and 24 are not considered sufficiently +strong to be used with SAE (or more or less anything else). As such, +they should never be enabled in runtime configuration for any production +use cases. These changes to introduce additional protection to mask +timing is only for completeness of implementation and not an indication +that these groups should be used. + +This is related to CVE-2019-9494. + +Signed-off-by: Jouni Malinen <jouni@codeaurora.org> +--- + src/common/sae.c | 38 ++++++++++++++++++++++++++++---------- + 1 file changed, 28 insertions(+), 10 deletions(-) + +diff --git a/src/common/sae.c b/src/common/sae.c +index 5df9b95aa..75b1b4a83 100644 +--- a/src/common/sae.c ++++ b/src/common/sae.c +@@ -601,22 +601,27 @@ fail: + } + + ++static int sae_modp_group_require_masking(int group) ++{ ++ /* Groups for which pwd-value is likely to be >= p frequently */ ++ return group == 22 || group == 23 || group == 24; ++} ++ ++ + static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1, + const u8 *addr2, const u8 *password, + size_t password_len, const char *identifier) + { +- u8 counter; ++ u8 counter, k; + u8 addrs[2 * ETH_ALEN]; + const u8 *addr[3]; + size_t len[3]; + size_t num_elem; + int found = 0; ++ struct crypto_bignum *pwe = NULL; + +- if (sae->tmp->pwe_ffc == NULL) { +- sae->tmp->pwe_ffc = crypto_bignum_init(); +- if (sae->tmp->pwe_ffc == NULL) +- return -1; +- } ++ crypto_bignum_deinit(sae->tmp->pwe_ffc, 1); ++ sae->tmp->pwe_ffc = NULL; + + wpa_hexdump_ascii_key(MSG_DEBUG, "SAE: password", + password, password_len); +@@ -640,7 +645,9 @@ static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1, + len[num_elem] = sizeof(counter); + num_elem++; + +- for (counter = 1; !found; counter++) { ++ k = sae_modp_group_require_masking(sae->group) ? 40 : 1; ++ ++ for (counter = 1; counter <= k || !found; counter++) { + u8 pwd_seed[SHA256_MAC_LEN]; + int res; + +@@ -650,19 +657,30 @@ static int sae_derive_pwe_ffc(struct sae_data *sae, const u8 *addr1, + break; + } + +- wpa_printf(MSG_DEBUG, "SAE: counter = %u", counter); ++ wpa_printf(MSG_DEBUG, "SAE: counter = %02u", counter); + if (hmac_sha256_vector(addrs, sizeof(addrs), num_elem, + addr, len, pwd_seed) < 0) + break; +- res = sae_test_pwd_seed_ffc(sae, pwd_seed, sae->tmp->pwe_ffc); ++ if (!pwe) { ++ pwe = crypto_bignum_init(); ++ if (!pwe) ++ break; ++ } ++ res = sae_test_pwd_seed_ffc(sae, pwd_seed, pwe); + if (res < 0) + break; + if (res > 0) { +- wpa_printf(MSG_DEBUG, "SAE: Use this PWE"); + found = 1; ++ if (!sae->tmp->pwe_ffc) { ++ wpa_printf(MSG_DEBUG, "SAE: Use this PWE"); ++ sae->tmp->pwe_ffc = pwe; ++ pwe = NULL; ++ } + } + } + ++ crypto_bignum_deinit(pwe, 1); ++ + return found ? 0 : -1; + } + +-- +2.21.0 + |