/*
- * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* https://www.openssl.org/source/license.html
*/
-/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
-
#include <stdio.h>
#include "internal/cryptlib.h"
#include <openssl/bn.h>
#include <openssl/sha.h>
#include "dsa_locl.h"
-#include <openssl/rand.h>
#include <openssl/asn1.h>
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
NULL
};
-/*-
- * These macro wrappers replace attempts to use the dsa_mod_exp() and
- * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
- * having a the macro work as an expression by bundling an "err_instr". So;
- *
- * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
- * dsa->method_mont_p)) goto err;
- *
- * can be replaced by;
- *
- * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
- * dsa->method_mont_p);
- */
+static const DSA_METHOD *default_DSA_method = &openssl_dsa_meth;
+
+void DSA_set_default_method(const DSA_METHOD *meth)
+{
+ default_DSA_method = meth;
+}
-#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
- do { \
- int _tmp_res53; \
- if ((dsa)->meth->dsa_mod_exp) \
- _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
- (a2), (p2), (m), (ctx), (in_mont)); \
- else \
- _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
- (m), (ctx), (in_mont)); \
- if (!_tmp_res53) err_instr; \
- } while(0)
-#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
- do { \
- int _tmp_res53; \
- if ((dsa)->meth->bn_mod_exp) \
- _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
- (m), (ctx), (m_ctx)); \
- else \
- _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
- if (!_tmp_res53) err_instr; \
- } while(0)
+const DSA_METHOD *DSA_get_default_method(void)
+{
+ return default_DSA_method;
+}
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 *r, *s;
+ 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;
}
ret = DSA_SIG_new();
if (ret == NULL)
goto err;
-
- DSA_SIG_get0(&r, &s, ret);
+ ret->r = BN_new();
+ ret->s = BN_new();
+ if (ret->r == NULL || ret->s == NULL)
+ goto err;
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, &r, dgst, dlen))
+ if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen))
goto err;
if (dlen > BN_num_bytes(dsa->q))
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, r, dsa->q, ctx))
- goto err; /* s = xr */
- if (!BN_add(s, xr, m))
- goto err; /* s = m + xr */
- if (BN_cmp(s, dsa->q) > 0)
- if (!BN_sub(s, 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;
- if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
+ } 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.
*/
- if (BN_is_zero(r) || BN_is_zero(s))
+ if (BN_is_zero(ret->r) || BN_is_zero(ret->s))
goto redo;
rv = 1;
ret = NULL;
}
BN_CTX_free(ctx);
- BN_clear_free(m);
- BN_clear_free(xr);
BN_clear_free(kinv);
return ret;
}
const unsigned char *dgst, int dlen)
{
BN_CTX *ctx = NULL;
- BIGNUM *k, *kq, *K, *kinv = NULL, *r = *rp;
+ BIGNUM *k, *kinv = NULL, *r = *rp;
+ BIGNUM *l, *m;
int ret = 0;
+ int q_bits;
if (!dsa->p || !dsa->q || !dsa->g) {
DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
}
k = BN_new();
- kq = BN_new();
- if (k == NULL || kq == NULL)
+ l = BN_new();
+ m = BN_new();
+ if (k == NULL || l == NULL || m == NULL)
goto err;
if (ctx_in == NULL) {
} else
ctx = ctx_in;
+ /* Preallocate space */
+ q_bits = BN_num_bits(dsa->q);
+ if (!BN_set_bit(k, q_bits)
+ || !BN_set_bit(l, q_bits)
+ || !BN_set_bit(m, q_bits))
+ goto err;
+
/* Get random k */
do {
if (dgst != NULL) {
if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
dlen, ctx))
goto err;
- } else if (!BN_rand_range(k, dsa->q))
+ } else if (!BN_priv_rand_range(k, dsa->q))
goto err;
} while (BN_is_zero(k));
- if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
- BN_set_flags(k, BN_FLG_CONSTTIME);
- }
+ BN_set_flags(k, BN_FLG_CONSTTIME);
if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
/* Compute r = (g^k mod p) mod q */
- if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
- if (!BN_copy(kq, k))
- goto err;
-
- /*
- * We do not want timing information to leak the length of k, so we
- * compute g^k using an equivalent exponent of fixed length. (This
- * is a kludge that we need because the BN_mod_exp_mont() does not
- * let us specify the desired timing behaviour.)
- */
+ /*
+ * We do not want timing information to leak the length of k, so we
+ * compute G^k using an equivalent scalar of fixed bit-length.
+ *
+ * We unconditionally perform both of these additions to prevent a
+ * small timing information leakage. We then choose the sum that is
+ * one bit longer than the modulus.
+ *
+ * TODO: revisit the BN_copy aiming for a memory access agnostic
+ * conditional copy.
+ */
+ if (!BN_add(l, k, dsa->q)
+ || !BN_add(m, l, dsa->q)
+ || !BN_copy(k, BN_num_bits(l) > q_bits ? l : m))
+ goto err;
- if (!BN_add(kq, kq, dsa->q))
- goto err;
- if (BN_num_bits(kq) <= BN_num_bits(dsa->q)) {
- if (!BN_add(kq, kq, dsa->q))
+ if ((dsa)->meth->bn_mod_exp != NULL) {
+ if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, k, dsa->p, ctx,
+ dsa->method_mont_p))
goto err;
- }
-
- K = kq;
} else {
- K = k;
+ if (!BN_mod_exp_mont(r, dsa->g, k, dsa->p, ctx, dsa->method_mont_p))
+ goto err;
}
- DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
- dsa->method_mont_p);
+
if (!BN_mod(r, r, dsa->q, ctx))
goto err;
if (ctx != ctx_in)
BN_CTX_free(ctx);
BN_clear_free(k);
- BN_clear_free(kq);
+ BN_clear_free(l);
+ BN_clear_free(m);
return ret;
}
BN_CTX *ctx;
BIGNUM *u1, *u2, *t1;
BN_MONT_CTX *mont = NULL;
- BIGNUM *r, *s;
+ const BIGNUM *r, *s;
int ret = -1, i;
if (!dsa->p || !dsa->q || !dsa->g) {
DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
goto err;
- DSA_SIG_get0(&r, &s, sig);
+ DSA_SIG_get0(sig, &r, &s);
if (BN_is_zero(r) || BN_is_negative(r) ||
BN_ucmp(r, dsa->q) >= 0) {
goto err;
}
- DSA_MOD_EXP(goto err, dsa, t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
- mont);
- /* BN_copy(&u1,&t1); */
+ if (dsa->meth->dsa_mod_exp != NULL) {
+ if (!dsa->meth->dsa_mod_exp(dsa, t1, dsa->g, u1, dsa->pub_key, u2,
+ dsa->p, ctx, mont))
+ goto err;
+ } else {
+ if (!BN_mod_exp2_mont(t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
+ mont))
+ goto err;
+ }
+
/* let u1 = u1 mod q */
if (!BN_mod(u1, t1, dsa->q, ctx))
goto err;
BN_free(u1);
BN_free(u2);
BN_free(t1);
- return (ret);
+ return ret;
}
static int dsa_init(DSA *dsa)
{
dsa->flags |= DSA_FLAG_CACHE_MONT_P;
- return (1);
+ return 1;
}
static int dsa_finish(DSA *dsa)
{
BN_MONT_CTX_free(dsa->method_mont_p);
- return (1);
+ return 1;
}
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