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56 lines
1.6 KiB
Diff
56 lines
1.6 KiB
Diff
From c93461c1d98f52681717a088776ab32fd97872b0 Mon Sep 17 00:00:00 2001
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From: Jouni Malinen <jouni@codeaurora.org>
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Date: Fri, 8 Mar 2019 00:24:12 +0200
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Subject: [PATCH 03/14] OpenSSL: Use constant time selection for
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crypto_bignum_legendre()
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Get rid of the branches that depend on the result of the Legendre
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operation. This is needed to avoid leaking information about different
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temporary results in blinding mechanisms.
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This is related to CVE-2019-9494 and CVE-2019-9495.
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Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
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---
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src/crypto/crypto_openssl.c | 15 +++++++++------
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1 file changed, 9 insertions(+), 6 deletions(-)
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--- a/src/crypto/crypto_openssl.c
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+++ b/src/crypto/crypto_openssl.c
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@@ -24,6 +24,7 @@
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#endif /* CONFIG_ECC */
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#include "common.h"
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+#include "utils/const_time.h"
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#include "wpabuf.h"
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#include "dh_group5.h"
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#include "sha1.h"
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@@ -1435,6 +1436,7 @@ int crypto_bignum_legendre(const struct
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BN_CTX *bnctx;
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BIGNUM *exp = NULL, *tmp = NULL;
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int res = -2;
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+ unsigned int mask;
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if (TEST_FAIL())
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return -2;
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@@ -1453,12 +1455,13 @@ int crypto_bignum_legendre(const struct
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(const BIGNUM *) p, bnctx, NULL))
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goto fail;
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- if (BN_is_word(tmp, 1))
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- res = 1;
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- else if (BN_is_zero(tmp))
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- res = 0;
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- else
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- res = -1;
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+ /* Return 1 if tmp == 1, 0 if tmp == 0, or -1 otherwise. Need to use
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+ * constant time selection to avoid branches here. */
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+ res = -1;
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+ mask = const_time_eq(BN_is_word(tmp, 1), 1);
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+ res = const_time_select_int(mask, 1, res);
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+ mask = const_time_eq(BN_is_zero(tmp), 1);
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+ res = const_time_select_int(mask, 0, res);
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fail:
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BN_clear_free(tmp);
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