Fix the ECDSA timing attack mentioned in the paper at:

[openssl.git] / crypto / ecdsa / ecs_ossl.c

diff --git a/crypto/ecdsa/ecs_ossl.c b/crypto/ecdsa/ecs_ossl.c
index 32d66a97741d43ae11be4088f0a4767e7826cf06..50d02ed0691c8b9d85e8e5072ef3222de25389fd 100644 (file)
--- a/crypto/ecdsa/ecs_ossl.c
+++ b/crypto/ecdsa/ecs_ossl.c
@@ -56,6 +56,8 @@
  *
  */
 
+#define OPENSSL_FIPSAPI
+
 #include "ecs_locl.h"
 #include <openssl/err.h>
 #include <openssl/obj_mac.h>
@@ -131,6 +133,11 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
                goto err;
        }
+
+#ifdef OPENSSL_FIPS
+       if (!fips_check_ec_prng(eckey))
+               goto err;
+#endif
        
        do
        {
@@ -144,6 +151,16 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
                        }
                while (BN_is_zero(k));
 
+#ifdef ECDSA_POINT_MUL_NO_CONSTTIME
+               /* 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. */
+
+               if (!BN_add(k, k, order)) goto err;
+               if (BN_num_bits(k) <= BN_num_bits(order))
+                       if (!BN_add(k, k, order)) goto err;
+#endif /* def(ECDSA_POINT_MUL_NO_CONSTTIME) */
+
                /* compute r the x-coordinate of generator * k */
                if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))
                {
@@ -159,6 +176,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
                                goto err;
                        }
                }
+#ifndef OPENSSL_NO_EC2M
                else /* NID_X9_62_characteristic_two_field */
                {
                        if (!EC_POINT_get_affine_coordinates_GF2m(group,
@@ -168,6 +186,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
                                goto err;
                        }
                }
+#endif
                if (!BN_nnmod(r, X, order, ctx))
                {
                        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
@@ -212,7 +231,7 @@ err:
 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 
                const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)
 {
-       int     ok = 0;
+       int     ok = 0, i;
        BIGNUM *kinv=NULL, *s, *m=NULL,*tmp=NULL,*order=NULL;
        const BIGNUM *ckinv;
        BN_CTX     *ctx = NULL;
@@ -231,6 +250,11 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
                return NULL;
        }
 
+#ifdef OPENSSL_FIPS
+       if (!fips_check_ec_prng(eckey))
+               return NULL;
+#endif
+
        ret = ECDSA_SIG_new();
        if (!ret)
        {
@@ -251,14 +275,19 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
                goto err;
        }
-       if (dgst_len > BN_num_bytes(order))
+       i = BN_num_bits(order);
+       /* Need to truncate digest if it is too long: first truncate whole
+        * bytes.
+        */
+       if (8 * dgst_len > i)
+               dgst_len = (i + 7)/8;
+       if (!BN_bin2bn(dgst, dgst_len, m))
        {
-               ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
-                       ECDSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
+               ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
                goto err;
        }
-
-       if (!BN_bin2bn(dgst, dgst_len, m))
+       /* If still too long truncate remaining bits with a shift */
+       if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
        {
                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
                goto err;
@@ -267,7 +296,8 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
        {
                if (in_kinv == NULL || in_r == NULL)
                {
-                       if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r))
+                       if (!ecdsa->meth->ecdsa_sign_setup(eckey, ctx,
+                                                               &kinv, &ret->r))
                        {
                                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,ERR_R_ECDSA_LIB);
                                goto err;
@@ -338,7 +368,7 @@ err:
 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
                const ECDSA_SIG *sig, EC_KEY *eckey)
 {
-       int ret = -1;
+       int ret = -1, i;
        BN_CTX   *ctx;
        BIGNUM   *order, *u1, *u2, *m, *X;
        EC_POINT *point = NULL;
@@ -392,11 +422,23 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
                goto err;
        }
        /* digest -> m */
+       i = BN_num_bits(order);
+       /* Need to truncate digest if it is too long: first truncate whole
+        * bytes.
+        */
+       if (8 * dgst_len > i)
+               dgst_len = (i + 7)/8;
        if (!BN_bin2bn(dgst, dgst_len, m))
        {
                ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
                goto err;
        }
+       /* If still too long truncate remaining bits with a shift */
+       if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
+       {
+               ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
+               goto err;
+       }
        /* u1 = m * tmp mod order */
        if (!BN_mod_mul(u1, m, u2, order, ctx))
        {
@@ -429,6 +471,7 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
                        goto err;
                }
        }
+#ifndef OPENSSL_NO_EC2M
        else /* NID_X9_62_characteristic_two_field */
        {
                if (!EC_POINT_get_affine_coordinates_GF2m(group,
@@ -438,7 +481,7 @@ static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
                        goto err;
                }
        }
-       
+#endif 
        if (!BN_nnmod(u1, X, order, ctx))
        {
                ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
@@ -453,3 +496,32 @@ err:
                EC_POINT_free(point);
        return ret;
 }
+
+#ifdef OPENSSL_FIPSCANISTER
+/* FIPS stanadlone version of ecdsa_check: just return FIPS method */
+ECDSA_DATA *fips_ecdsa_check(EC_KEY *key)
+       {
+       static ECDSA_DATA rv = {
+               0,0,0,
+               &openssl_ecdsa_meth
+               };
+       return &rv;
+       }
+/* Standalone digest sign and verify */
+int FIPS_ecdsa_verify_digest(EC_KEY *key,
+                       const unsigned char *dig, int dlen, ECDSA_SIG *s)
+       {
+       ECDSA_DATA *ecdsa = ecdsa_check(key);
+       if (ecdsa == NULL)
+               return 0;
+       return ecdsa->meth->ecdsa_do_verify(dig, dlen, s, key);
+       }
+ECDSA_SIG * FIPS_ecdsa_sign_digest(EC_KEY *key,
+                                       const unsigned char *dig, int dlen)
+       {
+       ECDSA_DATA *ecdsa = ecdsa_check(key);
+       if (ecdsa == NULL)
+               return NULL;
+       return ecdsa->meth->ecdsa_do_sign(dig, dlen, NULL, NULL, key);
+       }
+#endif