Commit c554155b authored by Bodo Möller's avatar Bodo Möller
Browse files

make sure RSA blinding works when the PRNG is not properly seeded; 

enable it automatically for the built-in engine
parent a1d12dae

CHANGES

+12 −1
Original line number Diff line number Diff line
@@ -469,8 +469,19 @@ 
     in ssl3_get_client_key_exchange (ssl/s3_srvr.c).

     [Bodo Moeller]



  *) Turn on RSA blinding by default in the default implementation

     to avoid a timing attack. Applications that don't want it can call

     RSA_blinding_off() or use the new flag RSA_FLAG_NO_BLINDING.

     They would be ill-advised to do so in most cases.

     [Ben Laurie, Steve Henson, Geoff Thorpe]



  *) Change RSA blinding code so that it works when the PRNG is not

     seeded (in this case, the secret RSA exponent is abused as

     an unpredictable seed -- if it is not unpredictable, there

     is no point in blinding anyway).

     [Bodo Moeller]



yet to be integrated into this CVS branch:

- RSA blinding changes

- Geoff's ENGINE_set_default() fix



  *) Target "mingw" now allows native Windows code to be generated in

crypto/rsa/rsa.h

+7 −0
Original line number Diff line number Diff line
@@ -162,6 +162,11 @@ struct rsa_st 
#define RSA_FLAG_CACHE_PUBLIC		0x02

#define RSA_FLAG_CACHE_PRIVATE		0x04

#define RSA_FLAG_BLINDING		0x08

#define RSA_FLAG_NO_BLINDING		0x80 /* new with 0.9.6j and 0.9.7b; the built-in

                                              * RSA implementation now uses blinding by

                                              * default (ignoring RSA_FLAG_BLINDING),

                                              * but other engines might not need it

                                              */

#define RSA_FLAG_THREAD_SAFE		0x10

/* This flag means the private key operations will be handled by rsa_mod_exp

 * and that they do not depend on the private key components being present:
@@ -174,6 +179,8 @@ struct rsa_st 
 */

#define RSA_FLAG_SIGN_VER		0x40



#define RSA_FLAG_NO_BLINDING		0x80



#define RSA_PKCS1_PADDING	1

#define RSA_SSLV23_PADDING	2

#define RSA_NO_PADDING		3

crypto/rsa/rsa_eay.c

+27 −8
Original line number Diff line number Diff line
@@ -211,6 +211,25 @@ err: 
	return(r);

	}



static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx)

	{

	int ret = 1;

	CRYPTO_w_lock(CRYPTO_LOCK_RSA);

	/* Check again inside the lock - the macro's check is racey */

	if(rsa->blinding == NULL)

		ret = RSA_blinding_on(rsa, ctx);

	CRYPTO_w_unlock(CRYPTO_LOCK_RSA);

	return ret;

	}



#define BLINDING_HELPER(rsa, ctx, err_instr) \

	do { \

		if((!((rsa)->flags & RSA_FLAG_NO_BLINDING)) && \

		    ((rsa)->blinding == NULL) && \

		    !rsa_eay_blinding(rsa, ctx)) \

			err_instr \

	} while(0)



/* signing */

static int RSA_eay_private_encrypt(int flen, const unsigned char *from,

	     unsigned char *to, RSA *rsa, int padding)
@@ -255,9 +274,9 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, 
		goto err;

		}



	if ((rsa->flags & RSA_FLAG_BLINDING) && (rsa->blinding == NULL))

		RSA_blinding_on(rsa,ctx);

	if (rsa->flags & RSA_FLAG_BLINDING)

	BLINDING_HELPER(rsa, ctx, goto err;);



	if (!(rsa->flags & RSA_FLAG_NO_BLINDING))

		if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;



	if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
@@ -274,7 +293,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, 
				rsa->_method_mod_n)) goto err;

		}



	if (rsa->flags & RSA_FLAG_BLINDING)

	if (!(rsa->flags & RSA_FLAG_NO_BLINDING))

		if (!BN_BLINDING_invert(&ret,rsa->blinding,ctx)) goto err;



	/* put in leading 0 bytes if the number is less than the
@@ -336,9 +355,9 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from, 
		goto err;

		}



	if ((rsa->flags & RSA_FLAG_BLINDING) && (rsa->blinding == NULL))

		RSA_blinding_on(rsa,ctx);

	if (rsa->flags & RSA_FLAG_BLINDING)

	BLINDING_HELPER(rsa, ctx, goto err;);



	if (!(rsa->flags & RSA_FLAG_NO_BLINDING))

		if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;



	/* do the decrypt */
@@ -357,7 +376,7 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from, 
			goto err;

		}



	if (rsa->flags & RSA_FLAG_BLINDING)

	if (!(rsa->flags & RSA_FLAG_NO_BLINDING))

		if (!BN_BLINDING_invert(&ret,rsa->blinding,ctx)) goto err;



	p=buf;

crypto/rsa/rsa_lib.c

+17 −4
Original line number Diff line number Diff line
@@ -72,7 +72,9 @@ static const RSA_METHOD *default_RSA_meth=NULL; 


RSA *RSA_new(void)

	{

	return(RSA_new_method(NULL));

	RSA *r=RSA_new_method(NULL);



	return r;

	}



void RSA_set_default_method(const RSA_METHOD *meth)
@@ -308,6 +310,7 @@ void RSA_blinding_off(RSA *rsa) 
		rsa->blinding=NULL;

		}

	rsa->flags &= ~RSA_FLAG_BLINDING;

	rsa->flags |= RSA_FLAG_NO_BLINDING;

	}



int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx)
@@ -328,13 +331,23 @@ int RSA_blinding_on(RSA *rsa, BN_CTX *p_ctx) 


	BN_CTX_start(ctx);

	A = BN_CTX_get(ctx);

	if ((RAND_status() == 0) && rsa->d != NULL && rsa->d->d != NULL)

		{

		/* if PRNG is not properly seeded, resort to secret exponent as unpredictable seed */

		RAND_add(rsa->d->d, rsa->d->dmax * sizeof rsa->d->d[0], 0);

		if (!BN_pseudo_rand_range(A,rsa->n)) goto err;

		}

	else

		{

		if (!BN_rand_range(A,rsa->n)) goto err;

		}

	if ((Ai=BN_mod_inverse(NULL,A,rsa->n,ctx)) == NULL) goto err;



	if (!rsa->meth->bn_mod_exp(A,A,rsa->e,rsa->n,ctx,rsa->_method_mod_n))

	    goto err;

	rsa->blinding=BN_BLINDING_new(A,Ai,rsa->n);

	rsa->flags |= RSA_FLAG_BLINDING;

	rsa->flags &= ~RSA_FLAG_NO_BLINDING;

	BN_free(Ai);

	ret=1;

err: