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-rw-r--r--main/wpa_supplicant/0021-SAE-Run-through-prf-result-processing-even-if-it-pri.patch59
1 files changed, 59 insertions, 0 deletions
diff --git a/main/wpa_supplicant/0021-SAE-Run-through-prf-result-processing-even-if-it-pri.patch b/main/wpa_supplicant/0021-SAE-Run-through-prf-result-processing-even-if-it-pri.patch
new file mode 100644
index 0000000000..0a2f398527
--- /dev/null
+++ b/main/wpa_supplicant/0021-SAE-Run-through-prf-result-processing-even-if-it-pri.patch
@@ -0,0 +1,59 @@
+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(-)
+
+diff --git a/src/common/sae.c b/src/common/sae.c
+index 0d56e5505..759e48e22 100644
+--- a/src/common/sae.c
++++ b/src/common/sae.c
+@@ -304,6 +304,8 @@ static int sae_test_pwd_seed_ecc(struct sae_data *sae, const u8 *pwd_seed,
+ 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 sae_data *sae, const u8 *pwd_seed,
+ 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 sae_data *sae, const u8 *pwd_seed,
+
+ 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);
+ }
+
+
+--
+2.20.1
+