Remove some unneeded code

[openssl.git] / crypto / ec / ecdsa_ossl.c

diff --git a/crypto/ec/ecdsa_ossl.c b/crypto/ec/ecdsa_ossl.c
index c7ab0ee1a377f09640a6e4d32ac61b05529b631f..2c9e5a88cf5a45c5e4c2bcf64d16abca6dbdc6cd 100644 (file)
--- a/crypto/ec/ecdsa_ossl.c
+++ b/crypto/ec/ecdsa_ossl.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2002-2018 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
@@ -41,6 +41,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
     EC_POINT *tmp_point = NULL;
     const EC_GROUP *group;
     int ret = 0;
+    int order_bits;
 
     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
@@ -77,6 +78,13 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
         goto err;
     }
 
+    /* Preallocate space */
+    order_bits = BN_num_bits(order);
+    if (!BN_set_bit(k, order_bits)
+        || !BN_set_bit(r, order_bits)
+        || !BN_set_bit(X, order_bits))
+        goto err;
+
     do {
         /* get random k */
         do
@@ -89,7 +97,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
                     goto err;
                 }
             } else {
-                if (!BN_rand_range(k, order)) {
+                if (!BN_priv_rand_range(k, order)) {
                     ECerr(EC_F_ECDSA_SIGN_SETUP,
                              EC_R_RANDOM_NUMBER_GENERATION_FAILED);
                     goto err;
@@ -100,13 +108,19 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
         /*
          * 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 order.  This guarantees the code
+         * path used in the constant time implementations elsewhere.
+         *
+         * TODO: revisit the BN_copy aiming for a memory access agnostic
+         * conditional copy.
          */
-
-        if (!BN_add(k, k, order))
+        if (!BN_add(r, k, order)
+            || !BN_add(X, r, order)
+            || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))
             goto err;
-        if (BN_num_bits(k) <= BN_num_bits(order))
-            if (!BN_add(k, k, order))
-                goto err;
 
         /* compute r the x-coordinate of generator * k */
         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
@@ -139,30 +153,33 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
     }
     while (BN_is_zero(r));
 
-    /* compute the inverse of k */
-    if (EC_GROUP_get_mont_data(group) != NULL) {
-        /*
-         * We want inverse in constant time, therefore we utilize the fact
-         * order must be prime and use Fermats Little Theorem instead.
-         */
-        if (!BN_set_word(X, 2)) {
-            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
-            goto err;
-        }
-        if (!BN_mod_sub(X, order, X, order, ctx)) {
-            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
-            goto err;
-        }
-        BN_set_flags(X, BN_FLG_CONSTTIME);
-        if (!BN_mod_exp_mont_consttime
-            (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
-            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
-            goto err;
-        }
-    } else {
-        if (!BN_mod_inverse(k, k, order, ctx)) {
-            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
-            goto err;
+    /* Check if optimized inverse is implemented */
+    if (EC_GROUP_do_inverse_ord(group, k, k, ctx) == 0) {
+        /* compute the inverse of k */
+        if (group->mont_data != NULL) {
+            /*
+             * We want inverse in constant time, therefore we utilize the fact
+             * order must be prime and use Fermats Little Theorem instead.
+             */
+            if (!BN_set_word(X, 2)) {
+                ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+                goto err;
+            }
+            if (!BN_mod_sub(X, order, X, order, ctx)) {
+                ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+                goto err;
+            }
+            BN_set_flags(X, BN_FLG_CONSTTIME);
+            if (!BN_mod_exp_mont_consttime(k, k, X, order, ctx,
+                                           group->mont_data)) {
+                ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+                goto err;
+            }
+        } else {
+            if (!BN_mod_inverse(k, k, order, ctx)) {
+                ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
+                goto err;
+            }
         }
     }
 
@@ -182,7 +199,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
         BN_CTX_free(ctx);
     EC_POINT_free(tmp_point);
     BN_clear_free(X);
-    return (ret);
+    return ret;
 }
 
 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
@@ -284,7 +301,7 @@ ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
         }
         if (BN_is_zero(s)) {
             /*
-             * if kinv and r have been supplied by the caller don't to
+             * if kinv and r have been supplied by the caller, don't
              * generate new kinv and r values
              */
             if (in_kinv != NULL && in_r != NULL) {
@@ -327,7 +344,7 @@ int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
 
     s = ECDSA_SIG_new();
     if (s == NULL)
-        return (ret);
+        return ret;
     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
         goto err;
     /* Ensure signature uses DER and doesn't have trailing garbage */
@@ -338,7 +355,7 @@ int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
  err:
     OPENSSL_clear_free(der, derlen);
     ECDSA_SIG_free(s);
-    return (ret);
+    return ret;
 }
 
 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
@@ -393,9 +410,12 @@ int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
         goto err;
     }
     /* calculate tmp1 = inv(S) mod order */
-    if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
-        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
-        goto err;
+    /* Check if optimized inverse is implemented */
+    if (EC_GROUP_do_inverse_ord(group, u2, sig->s, ctx) == 0) {
+        if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
+            ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
+            goto err;
+        }
     }
     /* digest -> m */
     i = BN_num_bits(order);