Commit 84b1e84a 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 only for the built-in engine
parent 5250725b

CHANGES

+10 −4
Changes for CHANGES: 10 added lines, 4 removed lines.
Original line number Diff line number Diff line
@@ -4,12 +4,18 @@ 


 Changes between 0.9.7a and 0.9.7b  [xx XXX 2003]



  *) Turn on RSA blinding by default, to avoid a timing attack. Applications

     that don't want it can call RSA_blinding_off(). They would be ill-advised

     to do so in most cases. The automatic enabling can also be turned off

     by defining OPENSSL_FORCE_NO_RSA_BLINDING at compile-time.

  *) 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]



  *) Fixed a typo bug that would cause ENGINE_set_default() to set an

     ENGINE as defaults for all supported algorithms irrespective of

     the 'flags' parameter. 'flags' is now honoured, so applications

crypto/rsa/rsa.h

+7 −0
Changes for crypto/rsa/rsa.h: 7 added lines, 0 removed lines.
Original line number Diff line number Diff line
@@ -158,6 +158,11 @@ 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 0.9.7b; 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:
@@ -170,6 +175,8 @@ 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

+5 −5
Changes for crypto/rsa/rsa_eay.c: 5 added lines, 5 removed lines.
Original line number Diff line number Diff line
@@ -208,7 +208,7 @@ static int rsa_eay_blinding(RSA *rsa, BN_CTX *ctx) 


#define BLINDING_HELPER(rsa, ctx, err_instr) \

	do { \

		if(((rsa)->flags & RSA_FLAG_BLINDING) && \

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

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

		    !rsa_eay_blinding(rsa, ctx)) \

		    err_instr \
@@ -260,7 +260,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, 


	BLINDING_HELPER(rsa, ctx, goto err;);



	if (rsa->flags & RSA_FLAG_BLINDING)

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

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



	if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
@@ -275,7 +275,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from, 
		if (!rsa->meth->bn_mod_exp(&ret,&f,rsa->d,rsa->n,ctx,NULL)) 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
@@ -339,7 +339,7 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from, 


	BLINDING_HELPER(rsa, ctx, goto err;);



	if (rsa->flags & RSA_FLAG_BLINDING)

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

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



	/* do the decrypt */
@@ -356,7 +356,7 @@ 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

+11 −4
Changes for crypto/rsa/rsa_lib.c: 11 added lines, 4 removed lines.
Original line number Diff line number Diff line
@@ -74,10 +74,6 @@ RSA *RSA_new(void) 
	{

	RSA *r=RSA_new_method(NULL);



#ifndef OPENSSL_NO_FORCE_RSA_BLINDING

	r->flags|=RSA_FLAG_BLINDING;

#endif



	return r;

	}
@@ -314,6 +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)
@@ -334,13 +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: