Make `safe' (EC)DSA nonces the default.

Adam Langley · snhenson · commit 190c615d4398 · 2013-07-15T12:57:48.000+01:00
This change updates 8a99cb2 to make the generation of (EC)DSA nonces using the message digest the default. It also reverts the changes to (EC)DSA_METHOD structure. In addition to making it the default, removing the flag from EC_KEY means that FIPS modules will no longer have an ABI mismatch.
diff --git a/crypto/dsa/dsa.h b/crypto/dsa/dsa.h
@@ -104,14 +104,6 @@
                                               * used for all
                                               * exponents.
                                               */
-#define DSA_FLAG_NONCE_FROM_HASH	0x04 /* Causes the DSA nonce
-					      * to be calculated from
-					      * SHA512(private_key +
-					      * H(message) +
-					      * random). This
-					      * strengthens DSA
-					      * against a weak
-					      * PRNG. */
 
 /* If this flag is set the DSA method is FIPS compliant and can be used
  * in FIPS mode. This is set in the validated module method. If an
@@ -147,9 +139,8 @@ struct dsa_method
 	{
 	const char *name;
 	DSA_SIG * (*dsa_do_sign)(const unsigned char *dgst, int dlen, DSA *dsa);
-	int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in,
-			      BIGNUM **kinvp, BIGNUM **rp,
-			      const unsigned char *dgst, int dlen);
+	int (*dsa_sign_setup)(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
+								BIGNUM **rp);
 	int (*dsa_do_verify)(const unsigned char *dgst, int dgst_len,
 			     DSA_SIG *sig, DSA *dsa);
 	int (*dsa_mod_exp)(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
@@ -353,7 +344,6 @@ void ERR_load_DSA_strings(void);
 #define DSA_R_MISSING_PARAMETERS			 101
 #define DSA_R_MODULUS_TOO_LARGE				 103
 #define DSA_R_NEED_NEW_SETUP_VALUES			 110
-#define DSA_R_NONCE_CANNOT_BE_PRECOMPUTED		 114
 #define DSA_R_NO_PARAMETERS_SET				 107
 #define DSA_R_PARAMETER_ENCODING_ERROR			 105
 #define DSA_R_Q_NOT_PRIME				 113
diff --git a/crypto/dsa/dsa_err.c b/crypto/dsa/dsa_err.c
@@ -112,7 +112,6 @@ static ERR_STRING_DATA DSA_str_reasons[]=
 {ERR_REASON(DSA_R_MISSING_PARAMETERS)    ,"missing parameters"},
 {ERR_REASON(DSA_R_MODULUS_TOO_LARGE)     ,"modulus too large"},
 {ERR_REASON(DSA_R_NEED_NEW_SETUP_VALUES) ,"need new setup values"},
-{ERR_REASON(DSA_R_NONCE_CANNOT_BE_PRECOMPUTED),"nonce cannot be precomputed"},
 {ERR_REASON(DSA_R_NO_PARAMETERS_SET)     ,"no parameters set"},
 {ERR_REASON(DSA_R_PARAMETER_ENCODING_ERROR),"parameter encoding error"},
 {ERR_REASON(DSA_R_Q_NOT_PRIME)           ,"q not prime"},
diff --git a/crypto/dsa/dsa_ossl.c b/crypto/dsa/dsa_ossl.c
@@ -72,9 +72,10 @@
 #endif
 
 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
-static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
-			  BIGNUM **kinvp, BIGNUM **rp,
-			  const unsigned char *dgst, int dlen);
+static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
+static int dsa_sign_setup_with_digest(DSA *dsa, BN_CTX *ctx_in,
+				      BIGNUM **kinvp, BIGNUM **rp,
+				      const unsigned char *dgst, int dlen);
 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
 			 DSA *dsa);
 static int dsa_init(DSA *dsa);
@@ -178,7 +179,7 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 redo:
 	if ((dsa->kinv == NULL) || (dsa->r == NULL))
 		{
-		if (!dsa->meth->dsa_sign_setup(dsa,ctx,&kinv,&r,dgst,dlen))
+		if (!dsa_sign_setup_with_digest(dsa,ctx,&kinv,&r,dgst,dlen))
 			goto err;
 		}
 	else
@@ -239,8 +240,13 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 	}
 
 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
-			  BIGNUM **kinvp, BIGNUM **rp,
-			  const unsigned char *dgst, int dlen)
+			  BIGNUM **kinvp, BIGNUM **rp) {
+	return dsa_sign_setup_with_digest(dsa, ctx_in, kinvp, rp, NULL, 0);
+}
+
+static int dsa_sign_setup_with_digest(DSA *dsa, BN_CTX *ctx_in,
+				      BIGNUM **kinvp, BIGNUM **rp,
+				      const unsigned char *dgst, int dlen)
 	{
 	BN_CTX *ctx;
 	BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
@@ -268,11 +274,11 @@ static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
 	do
 		{
 #ifndef OPENSSL_NO_SHA512
-		if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)
+		if (dgst != NULL)
 			{
-			/* If DSA_FLAG_NONCE_FROM_HASH is set then we calculate k from
-			 * SHA512(private_key + H(message) + random). This protects the
-			 * private key from a weak PRNG. */
+			/* We calculate k from SHA512(private_key + H(message)
+			 * + random). This protects the private key from a weak
+			 * PRNG. */
 			if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst,
 						   dlen, ctx))
 				goto err;
diff --git a/crypto/dsa/dsa_sign.c b/crypto/dsa/dsa_sign.c
@@ -72,12 +72,5 @@ DSA_SIG * DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 
 int DSA_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
 	{
-	if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)
-		{
-		/* One cannot precompute the DSA nonce if it is required to
-		 * depend on the message. */
-		DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_NONCE_CANNOT_BE_PRECOMPUTED);
-		return 0;
-		}
-	return dsa->meth->dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
+	return dsa->meth->dsa_sign_setup(dsa, ctx_in, kinvp, rp);
 	}
diff --git a/crypto/ec/ec.h b/crypto/ec/ec.h
@@ -823,17 +823,6 @@ void *EC_KEY_insert_key_method_data(EC_KEY *key, void *data,
 /* wrapper functions for the underlying EC_GROUP object */
 void EC_KEY_set_asn1_flag(EC_KEY *eckey, int asn1_flag);
 
-/** Sets whether ECDSA operations with the given key will calculate their k
- * value from SHA512(private_key + message + random) in order to protect
- * against a weak PRNG.
- * \param  on  Whether to calculate k from a hash or not
- */
-void EC_KEY_set_nonce_from_hash(EC_KEY *key, int on);
-
-/** Returns the value of nonce_from_hash
- */
-int EC_KEY_get_nonce_from_hash(const EC_KEY *key);
-
 /** Creates a table of pre-computed multiples of the generator to 
  *  accelerate further EC_KEY operations.
  *  \param  key  EC_KEY object
diff --git a/crypto/ec/ec_key.c b/crypto/ec/ec_key.c
@@ -85,7 +85,6 @@ EC_KEY *EC_KEY_new(void)
 	ret->pub_key = NULL;
 	ret->priv_key= NULL;
 	ret->enc_flag= 0; 
-	ret->nonce_from_hash_flag = 0;
 	ret->conv_form = POINT_CONVERSION_UNCOMPRESSED;
 	ret->references= 1;
 	ret->method_data = NULL;
@@ -199,7 +198,6 @@ EC_KEY *EC_KEY_copy(EC_KEY *dest, const EC_KEY *src)
 
 	/* copy the rest */
 	dest->enc_flag  = src->enc_flag;
-	dest->nonce_from_hash_flag = src->nonce_from_hash_flag;
 	dest->conv_form = src->conv_form;
 	dest->version   = src->version;
 	dest->flags = src->flags;
@@ -591,16 +589,6 @@ void EC_KEY_set_enc_flags(EC_KEY *key, unsigned int flags)
 	key->enc_flag = flags;
 	}
 
-int EC_KEY_get_nonce_from_hash(const EC_KEY *key)
-	{
-	return key->nonce_from_hash_flag;
-	}
-
-void EC_KEY_set_nonce_from_hash(EC_KEY *key, int on)
-	{
-	key->nonce_from_hash_flag = on != 0;
-	}
-
 point_conversion_form_t EC_KEY_get_conv_form(const EC_KEY *key)
 	{
 	return key->conv_form;
diff --git a/crypto/ec/ec_lcl.h b/crypto/ec/ec_lcl.h
@@ -246,7 +246,6 @@ struct ec_key_st {
 	BIGNUM	 *priv_key;
 
 	unsigned int enc_flag;
-	char nonce_from_hash_flag;
 	point_conversion_form_t conv_form;
 
 	int 	references;
diff --git a/crypto/ecdsa/ecdsa.h b/crypto/ecdsa/ecdsa.h
@@ -264,7 +264,6 @@ void ERR_load_ECDSA_strings(void);
 #define ECDSA_R_ERR_EC_LIB				 102
 #define ECDSA_R_MISSING_PARAMETERS			 103
 #define ECDSA_R_NEED_NEW_SETUP_VALUES			 106
-#define ECDSA_R_NONCE_CANNOT_BE_PRECOMPUTED		 107
 #define ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED		 104
 #define ECDSA_R_SIGNATURE_MALLOC_FAILED			 105
 
diff --git a/crypto/ecdsa/ecs_err.c b/crypto/ecdsa/ecs_err.c
@@ -84,7 +84,6 @@ static ERR_STRING_DATA ECDSA_str_reasons[]=
 {ERR_REASON(ECDSA_R_ERR_EC_LIB)          ,"err ec lib"},
 {ERR_REASON(ECDSA_R_MISSING_PARAMETERS)  ,"missing parameters"},
 {ERR_REASON(ECDSA_R_NEED_NEW_SETUP_VALUES),"need new setup values"},
-{ERR_REASON(ECDSA_R_NONCE_CANNOT_BE_PRECOMPUTED),"nonce cannot be precomputed"},
 {ERR_REASON(ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED),"random number generation failed"},
 {ERR_REASON(ECDSA_R_SIGNATURE_MALLOC_FAILED),"signature malloc failed"},
 {0,NULL}
diff --git a/crypto/ecdsa/ecs_locl.h b/crypto/ecdsa/ecs_locl.h
@@ -70,9 +70,8 @@ struct ecdsa_method
 	const char *name;
 	ECDSA_SIG *(*ecdsa_do_sign)(const unsigned char *dgst, int dgst_len, 
 			const BIGNUM *inv, const BIGNUM *rp, EC_KEY *eckey);
-	int (*ecdsa_sign_setup)(EC_KEY *eckey, BN_CTX *ctx,
-				BIGNUM **kinv, BIGNUM **r,
-				const unsigned char *dgst, int dlen);
+	int (*ecdsa_sign_setup)(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv,
+			BIGNUM **r);
 	int (*ecdsa_do_verify)(const unsigned char *dgst, int dgst_len, 
 			const ECDSA_SIG *sig, EC_KEY *eckey);
 #if 0
diff --git a/crypto/ecdsa/ecs_ossl.c b/crypto/ecdsa/ecs_ossl.c
@@ -66,9 +66,11 @@
 
 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen, 
 		const BIGNUM *, const BIGNUM *, EC_KEY *eckey);
-static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
-			    BIGNUM **kinvp, BIGNUM **rp,
-			    const unsigned char *dgst, int dlen);
+static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
+		BIGNUM **rp);
+static int ecdsa_sign_setup_with_digest(EC_KEY *eckey, BN_CTX *ctx_in,
+					BIGNUM **kinvp, BIGNUM **rp,
+					const unsigned char *dgst, int dlen);
 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len, 
 		const ECDSA_SIG *sig, EC_KEY *eckey);
 
@@ -90,9 +92,14 @@ const ECDSA_METHOD *ECDSA_OpenSSL(void)
 	return &openssl_ecdsa_meth;
 }
 
-static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
-			    BIGNUM **kinvp, BIGNUM **rp,
-			    const unsigned char *dgst, int dlen)
+static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
+		BIGNUM **rp) {
+	return ecdsa_sign_setup_with_digest(eckey, ctx_in, kinvp, rp, NULL, 0);
+}
+
+static int ecdsa_sign_setup_with_digest(EC_KEY *eckey, BN_CTX *ctx_in,
+					BIGNUM **kinvp, BIGNUM **rp,
+					const unsigned char *dgst, int dlen)
 {
 	BN_CTX   *ctx = NULL;
 	BIGNUM	 *k = NULL, *r = NULL, *order = NULL, *X = NULL;
@@ -147,7 +154,7 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
 		/* get random k */	
 		do
 #ifndef OPENSSL_NO_SHA512
-			if (EC_KEY_get_nonce_from_hash(eckey))
+			if (dgst != NULL)
 			{
 				if (!BN_generate_dsa_nonce(k, order, EC_KEY_get0_private_key(eckey),
 							   dgst, dlen, ctx))
@@ -320,7 +327,8 @@ static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
 	{
 		if (in_kinv == NULL || in_r == NULL)
 		{
-			if (!ecdsa->meth->ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len))
+			if (!ecdsa_sign_setup_with_digest(
+				eckey, ctx, &kinv, &ret->r, dgst, dgst_len))
 			{
 				ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,ERR_R_ECDSA_LIB);
 				goto err;
diff --git a/crypto/ecdsa/ecs_sign.c b/crypto/ecdsa/ecs_sign.c
@@ -58,7 +58,6 @@
 #include <openssl/engine.h>
 #endif
 #include <openssl/rand.h>
-#include <openssl/err.h>
 
 ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dlen, EC_KEY *eckey)
 {
@@ -103,12 +102,5 @@ int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 	ECDSA_DATA *ecdsa = ecdsa_check(eckey);
 	if (ecdsa == NULL)
 		return 0;
-	if (EC_KEY_get_nonce_from_hash(eckey))
-		{
-		/* You cannot precompute the ECDSA nonce if it is required to
-		 * depend on the message. */
-		ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ECDSA_R_NONCE_CANNOT_BE_PRECOMPUTED);
-		return 0;
-		}
-	return ecdsa->meth->ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
+	return ecdsa->meth->ecdsa_sign_setup(eckey, ctx_in, kinvp, rp);
 }

Original file line number	Diff line number	Diff line change
`@@ -72,12 +72,5 @@ DSA_SIG * DSA_do_sign(const unsigned char dgst, int dlen, DSA dsa)`
`72`	`72`
`73`	`73`	`int DSA_sign_setup(DSA dsa, BN_CTX ctx_in, BIGNUM kinvp, BIGNUM rp)`
`74`	`74`	`{`
`75`		`- if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)`
`76`		`- {`
`77`		`- /* One cannot precompute the DSA nonce if it is required to`
`78`		`- * depend on the message. */`
`79`		`- DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_NONCE_CANNOT_BE_PRECOMPUTED);`
`80`		`- return 0;`
`81`		`- }`
`82`		`- return dsa->meth->dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);`
	`75`	`+ return dsa->meth->dsa_sign_setup(dsa, ctx_in, kinvp, rp);`
`83`	`76`	`}`