diff options
| -rw-r--r-- | CHANGES | 4 | ||||
| -rw-r--r-- | crypto/dsa/dsa_ossl.c | 66 | ||||
| -rw-r--r-- | crypto/ec/ecdsa_ossl.c | 14 |
3 files changed, 58 insertions, 26 deletions
@@ -13,8 +13,8 @@ chosen point SCA attacks. [Sohaib ul Hassan, Nicola Tuveri, Billy Bob Brumley] - *) Add blinding to an ECDSA signature to protect against side channel attacks - discovered by Keegan Ryan (NCC Group). + *) Add blinding to ECDSA and DSA signatures to protect against side channel + attacks discovered by Keegan Ryan (NCC Group). [Matt Caswell] *) Enforce checking in the pkeyutl command line app to ensure that the input diff --git a/crypto/dsa/dsa_ossl.c b/crypto/dsa/dsa_ossl.c index d78c5f00cb..5237794d8f 100644 --- a/crypto/dsa/dsa_ossl.c +++ b/crypto/dsa/dsa_ossl.c @@ -59,19 +59,13 @@ const DSA_METHOD *DSA_OpenSSL(void) static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) { BIGNUM *kinv = NULL; - BIGNUM *m; - BIGNUM *xr; + BIGNUM *m, *blind, *blindm, *tmp; BN_CTX *ctx = NULL; int reason = ERR_R_BN_LIB; DSA_SIG *ret = NULL; int rv = 0; - m = BN_new(); - xr = BN_new(); - if (m == NULL || xr == NULL) - goto err; - - if (!dsa->p || !dsa->q || !dsa->g) { + if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) { reason = DSA_R_MISSING_PARAMETERS; goto err; } @@ -87,6 +81,13 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) ctx = BN_CTX_new(); if (ctx == NULL) goto err; + m = BN_CTX_get(ctx); + blind = BN_CTX_get(ctx); + blindm = BN_CTX_get(ctx); + tmp = BN_CTX_get(ctx); + if (tmp == NULL) + goto err; + redo: if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen)) goto err; @@ -101,17 +102,50 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) if (BN_bin2bn(dgst, dlen, m) == NULL) goto err; - /* Compute s = inv(k) (m + xr) mod q */ - if (!BN_mod_mul(xr, dsa->priv_key, ret->r, dsa->q, ctx)) - goto err; /* s = xr */ - if (!BN_add(ret->s, xr, m)) - goto err; /* s = m + xr */ - if (BN_cmp(ret->s, dsa->q) > 0) - if (!BN_sub(ret->s, ret->s, dsa->q)) + /* + * The normal signature calculation is: + * + * s := k^-1 * (m + r * priv_key) mod q + * + * We will blind this to protect against side channel attacks + * + * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q + */ + + /* Generate a blinding value */ + do { + if (!BN_priv_rand(blind, BN_num_bits(dsa->q) - 1, + BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY)) 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 q */ + if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->q, ctx)) + goto err; + if (!BN_mod_mul(tmp, tmp, ret->r, dsa->q, ctx)) + goto err; + + /* blindm := blind * m mod q */ + if (!BN_mod_mul(blindm, blind, m, dsa->q, ctx)) + goto err; + + /* s : = (blind * priv_key * r) + (blind * m) mod q */ + if (!BN_mod_add_quick(ret->s, tmp, blindm, dsa->q)) + goto err; + + /* s := s * k^-1 mod q */ if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->q, ctx)) goto err; + /* s:= s * blind^-1 mod q */ + if (BN_mod_inverse(blind, blind, dsa->q, ctx) == NULL) + goto err; + if (!BN_mod_mul(ret->s, ret->s, blind, dsa->q, ctx)) + goto err; + /* * Redo if r or s is zero as required by FIPS 186-3: this is very * unlikely. @@ -128,8 +162,6 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) ret = NULL; } BN_CTX_free(ctx); - BN_clear_free(m); - BN_clear_free(xr); BN_clear_free(kinv); return ret; } diff --git a/crypto/ec/ecdsa_ossl.c b/crypto/ec/ecdsa_ossl.c index 640593bc2d..cdd0cf0228 100644 --- a/crypto/ec/ecdsa_ossl.c +++ b/crypto/ec/ecdsa_ossl.c @@ -288,7 +288,7 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len, * * We will blind this to protect against side channel attacks * - * s := k^-1 * blind^-1 * (blind * m + blind * r * priv_key) mod order + * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod order */ /* Generate a blinding value */ @@ -323,18 +323,18 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len, goto err; } - /* s:= s * blind^-1 mod order */ - if (BN_mod_inverse(blind, blind, order, ctx) == NULL) { + /* s := s * k^-1 mod order */ + if (!BN_mod_mul(s, s, ckinv, order, ctx)) { ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB); goto err; } - if (!BN_mod_mul(s, s, blind, order, ctx)) { + + /* s:= s * blind^-1 mod order */ + if (BN_mod_inverse(blind, blind, order, ctx) == NULL) { ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB); goto err; } - - /* s := s * k^-1 mod order */ - if (!BN_mod_mul(s, s, ckinv, order, ctx)) { + if (!BN_mod_mul(s, s, blind, order, ctx)) { ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB); goto err; } |