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-rw-r--r--main/hostapd/0001-OpenSSL-Use-constant-time-operations-for-private-big.patch92
1 files changed, 92 insertions, 0 deletions
diff --git a/main/hostapd/0001-OpenSSL-Use-constant-time-operations-for-private-big.patch b/main/hostapd/0001-OpenSSL-Use-constant-time-operations-for-private-big.patch
new file mode 100644
index 0000000000..516c3b633a
--- /dev/null
+++ b/main/hostapd/0001-OpenSSL-Use-constant-time-operations-for-private-big.patch
@@ -0,0 +1,92 @@
+From d42c477cc794163a3757956bbffca5cea000923c Mon Sep 17 00:00:00 2001
+From: Jouni Malinen <jouni@codeaurora.org>
+Date: Tue, 26 Feb 2019 11:43:03 +0200
+Subject: [PATCH] OpenSSL: Use constant time operations for private bignums
+
+This helps in reducing measurable timing differences in operations
+involving private information. BoringSSL has removed BN_FLG_CONSTTIME
+and expects specific constant time functions to be called instead, so a
+bit different approach is needed depending on which library is used.
+
+The main operation that needs protection against side channel attacks is
+BN_mod_exp() that depends on private keys (the public key validation
+step in crypto_dh_derive_secret() is an exception that can use the
+faster version since it does not depend on private keys).
+
+crypto_bignum_div() is currently used only in SAE FFC case with not
+safe-prime groups and only with values that do not depend on private
+keys, so it is not critical to protect it.
+
+crypto_bignum_inverse() is currently used only in SAE FFC PWE
+derivation. The additional protection here is targeting only OpenSSL.
+BoringSSL may need conversion to using BN_mod_inverse_blinded().
+
+This is related to CVE-2019-9494 and CVE-2019-9495.
+
+Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
+---
+ src/crypto/crypto_openssl.c | 20 +++++++++++++++-----
+ 1 file changed, 15 insertions(+), 5 deletions(-)
+
+diff --git a/src/crypto/crypto_openssl.c b/src/crypto/crypto_openssl.c
+index 9c2ba58d5..ac53cc81a 100644
+--- a/src/crypto/crypto_openssl.c
++++ b/src/crypto/crypto_openssl.c
+@@ -607,7 +607,8 @@ int crypto_mod_exp(const u8 *base, size_t base_len,
+ bn_result == NULL)
+ goto error;
+
+- if (BN_mod_exp(bn_result, bn_base, bn_exp, bn_modulus, ctx) != 1)
++ if (BN_mod_exp_mont_consttime(bn_result, bn_base, bn_exp, bn_modulus,
++ ctx, NULL) != 1)
+ goto error;
+
+ *result_len = BN_bn2bin(bn_result, result);
+@@ -1360,8 +1361,9 @@ int crypto_bignum_exptmod(const struct crypto_bignum *a,
+ bnctx = BN_CTX_new();
+ if (bnctx == NULL)
+ return -1;
+- res = BN_mod_exp((BIGNUM *) d, (const BIGNUM *) a, (const BIGNUM *) b,
+- (const BIGNUM *) c, bnctx);
++ res = BN_mod_exp_mont_consttime((BIGNUM *) d, (const BIGNUM *) a,
++ (const BIGNUM *) b, (const BIGNUM *) c,
++ bnctx, NULL);
+ BN_CTX_free(bnctx);
+
+ return res ? 0 : -1;
+@@ -1380,6 +1382,11 @@ int crypto_bignum_inverse(const struct crypto_bignum *a,
+ bnctx = BN_CTX_new();
+ if (bnctx == NULL)
+ return -1;
++#ifdef OPENSSL_IS_BORINGSSL
++ /* TODO: use BN_mod_inverse_blinded() ? */
++#else /* OPENSSL_IS_BORINGSSL */
++ BN_set_flags((BIGNUM *) a, BN_FLG_CONSTTIME);
++#endif /* OPENSSL_IS_BORINGSSL */
+ res = BN_mod_inverse((BIGNUM *) c, (const BIGNUM *) a,
+ (const BIGNUM *) b, bnctx);
+ BN_CTX_free(bnctx);
+@@ -1413,6 +1420,9 @@ int crypto_bignum_div(const struct crypto_bignum *a,
+ bnctx = BN_CTX_new();
+ if (bnctx == NULL)
+ return -1;
++#ifndef OPENSSL_IS_BORINGSSL
++ BN_set_flags((BIGNUM *) a, BN_FLG_CONSTTIME);
++#endif /* OPENSSL_IS_BORINGSSL */
+ res = BN_div((BIGNUM *) c, NULL, (const BIGNUM *) a,
+ (const BIGNUM *) b, bnctx);
+ BN_CTX_free(bnctx);
+@@ -1504,8 +1514,8 @@ int crypto_bignum_legendre(const struct crypto_bignum *a,
+ /* exp = (p-1) / 2 */
+ !BN_sub(exp, (const BIGNUM *) p, BN_value_one()) ||
+ !BN_rshift1(exp, exp) ||
+- !BN_mod_exp(tmp, (const BIGNUM *) a, exp, (const BIGNUM *) p,
+- bnctx))
++ !BN_mod_exp_mont_consttime(tmp, (const BIGNUM *) a, exp,
++ (const BIGNUM *) p, bnctx, NULL))
+ goto fail;
+
+ if (BN_is_word(tmp, 1))
+--
+2.21.0
+