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deps: float 949ff366 from openssl (ECDSA blinding)
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Pending OpenSSL 1.0.2p release.

Ref: https://www.nccgroup.trust/us/our-research/technical-advisory-return-of-the-hidden-number-problem/
Ref: #21345
Upstream: openssl/openssl@949ff366
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Shigeki Ohtsu <[email protected]>

Original commit message:

    Add blinding to an ECDSA signature

    Keegan Ryan (NCC Group) has demonstrated a side channel attack on an
    ECDSA signature operation. During signing the signer calculates:

    s:= k^-1 * (m + r * priv_key) mod order

    The addition operation above provides a sufficient signal for a
    flush+reload attack to derive the private key given sufficient signature
    operations.

    As a mitigation (based on a suggestion from Keegan) we add blinding to
    the operation so that:

    s := k^-1 * blind^-1 (blind * m + blind * r * priv_key) mod order

    Since this attack is a localhost side channel only no CVE is assigned.

    Reviewed-by: Rich Salz <[email protected]>
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@rvagg
rvagg committed Jun 18, 2018
1 parent 5a30e0b commit cc6827c
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Showing 2 changed files with 75 additions and 16 deletions.
9 changes: 8 additions & 1 deletion deps/openssl/openssl/crypto/ecdsa/ecdsatest.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -137,7 +137,7 @@ int restore_rand(void)
return 1;
}

static int fbytes_counter = 0;
static int fbytes_counter = 0, use_fake = 0;
static const char *numbers[8] = {
"651056770906015076056810763456358567190100156695615665659",
"6140507067065001063065065565667405560006161556565665656654",
Expand All @@ -158,6 +158,11 @@ int fbytes(unsigned char *buf, int num)
int ret;
BIGNUM *tmp = NULL;

if (use_fake == 0)
return old_rand->bytes(buf, num);

use_fake = 0;

if (fbytes_counter >= 8)
return 0;
tmp = BN_new();
Expand Down Expand Up @@ -199,11 +204,13 @@ int x9_62_test_internal(BIO *out, int nid, const char *r_in, const char *s_in)
/* create the key */
if ((key = EC_KEY_new_by_curve_name(nid)) == NULL)
goto x962_int_err;
use_fake = 1;
if (!EC_KEY_generate_key(key))
goto x962_int_err;
BIO_printf(out, ".");
(void)BIO_flush(out);
/* create the signature */
use_fake = 1;
signature = ECDSA_do_sign(digest, 20, key);
if (signature == NULL)
goto x962_int_err;
Expand Down
82 changes: 67 additions & 15 deletions deps/openssl/openssl/crypto/ecdsa/ecs_ossl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -252,6 +252,7 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
{
int ok = 0, i;
BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
BIGNUM *blind = NULL, *blindm = NULL;
const BIGNUM *ckinv;
BN_CTX *ctx = NULL;
const EC_GROUP *group;
Expand All @@ -269,14 +270,25 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
}

ret = ECDSA_SIG_new();
if (!ret) {
if (ret == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
return NULL;
}
s = ret->s;

if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
(tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
ctx = BN_CTX_new();
if (ctx == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
goto err;
}

BN_CTX_start(ctx);
order = BN_CTX_get(ctx);
tmp = BN_CTX_get(ctx);
m = BN_CTX_get(ctx);
blind = BN_CTX_get(ctx);
blindm = BN_CTX_get(ctx);
if (blindm == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
goto err;
}
Expand Down Expand Up @@ -315,26 +327,70 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
}
}

if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
/*
* The normal signature calculation is:
*
* s := k^-1 * (m + r * priv_key) mod order
*
* We will blind this to protect against side channel attacks
*
* s := k^-1 * blind^-1 * (blind * m + blind * r * priv_key) mod order
*/

/* Generate a blinding value */
do {
if (!BN_rand(blind, BN_num_bits(order) - 1, -1, 0))
goto err;
} while (BN_is_zero(blind));
BN_set_flags(blind, BN_FLG_CONSTTIME);
BN_set_flags(blindm, BN_FLG_CONSTTIME);
BN_set_flags(tmp, BN_FLG_CONSTTIME);

/* tmp := blind * priv_key * r mod order */
if (!BN_mod_mul(tmp, blind, priv_key, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}
if (!BN_mod_mul(tmp, tmp, ret->r, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}

/* blindm := blind * m mod order */
if (!BN_mod_mul(blindm, blind, m, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}

/* s : = (blind * priv_key * r) + (blind * m) mod order */
if (!BN_mod_add_quick(s, tmp, blindm, order)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}

/* s:= s * blind^-1 mod order */
if (BN_mod_inverse(blind, blind, order, ctx) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}
if (!BN_mod_add_quick(s, tmp, m, order)) {
if (!BN_mod_mul(s, s, blind, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}

/* s := s * k^-1 mod order */
if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}

if (BN_is_zero(s)) {
/*
* if kinv and r have been supplied by the caller don't to
* generate new kinv and r values
*/
if (in_kinv != NULL && in_r != NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
ECDSA_R_NEED_NEW_SETUP_VALUES);
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ECDSA_R_NEED_NEW_SETUP_VALUES);
goto err;
}
} else
Expand All @@ -349,15 +405,11 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
ECDSA_SIG_free(ret);
ret = NULL;
}
if (ctx)
if (ctx != NULL) {
BN_CTX_end(ctx);
BN_CTX_free(ctx);
if (m)
BN_clear_free(m);
if (tmp)
BN_clear_free(tmp);
if (order)
BN_free(order);
if (kinv)
}
if (kinv != NULL)
BN_clear_free(kinv);
return ret;
}
Expand Down

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