b8ea0db3ae
* gnu/packages/patches/openssl-1.0.2-CVE-2018-0495.patch, gnu/packages/patches/openssl-1.0.2-CVE-2018-0732.patch: New files. * gnu/local.mk (dist_patch_DATA): Add them. * gnu/packages/tls.scm (openssl)[replacement]: New field. (openssl/fixed): New variable.
215 lines
6.9 KiB
Diff
215 lines
6.9 KiB
Diff
Fix CVE-2018-0495:
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https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-0495
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https://www.nccgroup.trust/us/our-research/technical-advisory-return-of-the-hidden-number-problem/
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Patch copied from upstream source repository:
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https://github.com/openssl/openssl/commit/949ff36623eafc3523a9f91784992965018ffb05
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From 949ff36623eafc3523a9f91784992965018ffb05 Mon Sep 17 00:00:00 2001
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From: Matt Caswell <matt@openssl.org>
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Date: Fri, 25 May 2018 12:10:13 +0100
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Subject: [PATCH] Add blinding to an ECDSA signature
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Keegan Ryan (NCC Group) has demonstrated a side channel attack on an
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ECDSA signature operation. During signing the signer calculates:
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s:= k^-1 * (m + r * priv_key) mod order
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The addition operation above provides a sufficient signal for a
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flush+reload attack to derive the private key given sufficient signature
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operations.
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As a mitigation (based on a suggestion from Keegan) we add blinding to
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the operation so that:
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s := k^-1 * blind^-1 (blind * m + blind * r * priv_key) mod order
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Since this attack is a localhost side channel only no CVE is assigned.
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Reviewed-by: Rich Salz <rsalz@openssl.org>
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---
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CHANGES | 4 ++
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crypto/ecdsa/ecdsatest.c | 9 ++++-
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crypto/ecdsa/ecs_ossl.c | 82 ++++++++++++++++++++++++++++++++--------
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3 files changed, 79 insertions(+), 16 deletions(-)
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diff --git a/crypto/ecdsa/ecdsatest.c b/crypto/ecdsa/ecdsatest.c
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index 0f301f86d9..a130fc9117 100644
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--- a/crypto/ecdsa/ecdsatest.c
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+++ b/crypto/ecdsa/ecdsatest.c
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@@ -137,7 +137,7 @@ int restore_rand(void)
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return 1;
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}
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-static int fbytes_counter = 0;
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+static int fbytes_counter = 0, use_fake = 0;
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static const char *numbers[8] = {
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"651056770906015076056810763456358567190100156695615665659",
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"6140507067065001063065065565667405560006161556565665656654",
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@@ -158,6 +158,11 @@ int fbytes(unsigned char *buf, int num)
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int ret;
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BIGNUM *tmp = NULL;
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+ if (use_fake == 0)
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+ return old_rand->bytes(buf, num);
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+
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+ use_fake = 0;
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+
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if (fbytes_counter >= 8)
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return 0;
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tmp = BN_new();
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@@ -199,11 +204,13 @@ int x9_62_test_internal(BIO *out, int nid, const char *r_in, const char *s_in)
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/* create the key */
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if ((key = EC_KEY_new_by_curve_name(nid)) == NULL)
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goto x962_int_err;
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+ use_fake = 1;
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if (!EC_KEY_generate_key(key))
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goto x962_int_err;
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BIO_printf(out, ".");
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(void)BIO_flush(out);
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/* create the signature */
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+ use_fake = 1;
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signature = ECDSA_do_sign(digest, 20, key);
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if (signature == NULL)
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goto x962_int_err;
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diff --git a/crypto/ecdsa/ecs_ossl.c b/crypto/ecdsa/ecs_ossl.c
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index 16d4f59b9b..1d37551803 100644
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--- a/crypto/ecdsa/ecs_ossl.c
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+++ b/crypto/ecdsa/ecs_ossl.c
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@@ -252,6 +252,7 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
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{
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int ok = 0, i;
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BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
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+ BIGNUM *blind = NULL, *blindm = NULL;
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const BIGNUM *ckinv;
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BN_CTX *ctx = NULL;
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const EC_GROUP *group;
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@@ -269,14 +270,25 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
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}
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ret = ECDSA_SIG_new();
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- if (!ret) {
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+ if (ret == NULL) {
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ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
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return NULL;
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}
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s = ret->s;
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- if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
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- (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
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+ ctx = BN_CTX_new();
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+ if (ctx == NULL) {
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+ ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
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+ goto err;
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+ }
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+
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+ BN_CTX_start(ctx);
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+ order = BN_CTX_get(ctx);
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+ tmp = BN_CTX_get(ctx);
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+ m = BN_CTX_get(ctx);
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+ blind = BN_CTX_get(ctx);
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+ blindm = BN_CTX_get(ctx);
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+ if (blindm == NULL) {
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ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
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goto err;
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}
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@@ -315,26 +327,70 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
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}
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}
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- if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
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+ /*
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+ * The normal signature calculation is:
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+ *
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+ * s := k^-1 * (m + r * priv_key) mod order
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+ *
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+ * We will blind this to protect against side channel attacks
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+ *
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+ * s := k^-1 * blind^-1 * (blind * m + blind * r * priv_key) mod order
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+ */
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+
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+ /* Generate a blinding value */
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+ do {
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+ if (!BN_rand(blind, BN_num_bits(order) - 1, -1, 0))
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+ goto err;
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+ } while (BN_is_zero(blind));
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+ BN_set_flags(blind, BN_FLG_CONSTTIME);
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+ BN_set_flags(blindm, BN_FLG_CONSTTIME);
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+ BN_set_flags(tmp, BN_FLG_CONSTTIME);
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+
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+ /* tmp := blind * priv_key * r mod order */
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+ if (!BN_mod_mul(tmp, blind, priv_key, order, ctx)) {
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+ ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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+ goto err;
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+ }
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+ if (!BN_mod_mul(tmp, tmp, ret->r, order, ctx)) {
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+ ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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+ goto err;
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+ }
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+
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+ /* blindm := blind * m mod order */
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+ if (!BN_mod_mul(blindm, blind, m, order, ctx)) {
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+ ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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+ goto err;
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+ }
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+
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+ /* s : = (blind * priv_key * r) + (blind * m) mod order */
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+ if (!BN_mod_add_quick(s, tmp, blindm, order)) {
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+ ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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+ goto err;
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+ }
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+
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+ /* s:= s * blind^-1 mod order */
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+ if (BN_mod_inverse(blind, blind, order, ctx) == NULL) {
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ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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goto err;
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}
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- if (!BN_mod_add_quick(s, tmp, m, order)) {
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+ if (!BN_mod_mul(s, s, blind, order, ctx)) {
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ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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goto err;
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}
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+
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+ /* s := s * k^-1 mod order */
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if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
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ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
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goto err;
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}
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+
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if (BN_is_zero(s)) {
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/*
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* if kinv and r have been supplied by the caller don't to
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* generate new kinv and r values
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*/
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if (in_kinv != NULL && in_r != NULL) {
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- ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
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- ECDSA_R_NEED_NEW_SETUP_VALUES);
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+ ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ECDSA_R_NEED_NEW_SETUP_VALUES);
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goto err;
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}
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} else
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@@ -349,15 +405,11 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
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ECDSA_SIG_free(ret);
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ret = NULL;
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}
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- if (ctx)
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+ if (ctx != NULL) {
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+ BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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- if (m)
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- BN_clear_free(m);
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- if (tmp)
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- BN_clear_free(tmp);
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- if (order)
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- BN_free(order);
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- if (kinv)
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+ }
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+ if (kinv != NULL)
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BN_clear_free(kinv);
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return ret;
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}
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--
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2.17.1
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