make RSA blinding thread-safe (5679bcce) · Commits · CYBER - Cyber Security / TS 103 523 MSP / TLMSP / TLMSP OpenSSL

CHANGES

+7 −2

Original line number	Diff line number	Diff line
		@@ -483,12 +483,17 @@
		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]
		[Ben Laurie, Steve Henson, Geoff Thorpe, Bodo Moeller]

		*) 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).
		is no point in blinding anyway). Make RSA blinding thread-safe
		by remembering the creator's thread ID in rsa->blinding and
		having all other threads use local one-time blinding factors
		(this requires more computation than sharing rsa->blinding, but
		avoids excessive locking; and if an RSA object is not shared
		between threads, blinding will still be very fast).
		[Bodo Moeller]

		yet to be integrated into this CVS branch:

crypto/bn/bn.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -261,6 +261,8 @@ typedef struct bn_blinding_st
		BIGNUM *A;
		BIGNUM *Ai;
		BIGNUM mod; / just a reference */
		unsigned long thread_id; /* added in OpenSSL 0.9.6j and 0.9.7b;
		* used only by crypto/rsa/rsa_eay.c, rsa_lib.c */
		} BN_BLINDING;

		/* Used for montgomery multiplication */

crypto/rsa/rsa_eay.c

+106 −8

Original line number	Diff line number	Diff line
		@@ -230,6 +230,40 @@ static int rsa_eay_blinding(RSA rsa, BN_CTX ctx)
		err_instr \
		} while(0)

		static BN_BLINDING setup_blinding(RSA rsa, BN_CTX *ctx)
		{
		BIGNUM A, Ai;
		BN_BLINDING *ret = NULL;

		/* added in OpenSSL 0.9.6j and 0.9.7b */

		/* NB: similar code appears in RSA_blinding_on (rsa_lib.c);
		* this should be placed in a new function of its own, but for reasons
		* of binary compatibility can't */

		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;
		ret = BN_BLINDING_new(A,Ai,rsa->n);
		BN_free(Ai);
		err:
		BN_CTX_end(ctx);
		return ret;
		}

		/* signing */
		static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
		unsigned char to, RSA rsa, int padding)
		@@ -238,6 +272,8 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
		int i,j,k,num=0,r= -1;
		unsigned char *buf=NULL;
		BN_CTX *ctx=NULL;
		int local_blinding = 0;
		BN_BLINDING *blinding = NULL;

		BN_init(&f);
		BN_init(&ret);
		@@ -275,9 +311,38 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
		}

		BLINDING_HELPER(rsa, ctx, goto err;);

		blinding = rsa->blinding;

		/* Now unless blinding is disabled, 'blinding' is non-NULL.
		* But the BN_BLINDING object may be owned by some other thread
		* (we don't want to keep it constant and we don't want to use
		* lots of locking to avoid race conditions, so only a single
		* thread can use it; other threads have to use local blinding
		* factors) */
		if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
		if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
		{
		if (blinding == NULL)
		{
		RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT, ERR_R_INTERNAL_ERROR);
		goto err;
		}
		}

		if (blinding != NULL)
		{
		if (blinding->thread_id != CRYPTO_thread_id())
		{
		/* we need a local one-time blinding factor */

		blinding = setup_blinding(rsa, ctx);
		if (blinding == NULL)
		goto err;
		local_blinding = 1;
		}
		}

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

		if ( (rsa->flags & RSA_FLAG_EXT_PKEY) \|\|
		((rsa->p != NULL) &&
		@@ -293,8 +358,8 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
		rsa->_method_mod_n)) goto err;
		}

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

		/* put in leading 0 bytes if the number is less than the
		* length of the modulus */
		@@ -308,6 +373,8 @@ err:
		if (ctx != NULL) BN_CTX_free(ctx);
		BN_clear_free(&ret);
		BN_clear_free(&f);
		if (local_blinding)
		BN_BLINDING_free(blinding);
		if (buf != NULL)
		{
		OPENSSL_cleanse(buf,num);
		@@ -324,6 +391,8 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
		unsigned char *p;
		unsigned char *buf=NULL;
		BN_CTX *ctx=NULL;
		int local_blinding = 0;
		BN_BLINDING *blinding = NULL;

		BN_init(&f);
		BN_init(&ret);
		@@ -356,9 +425,38 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
		}

		BLINDING_HELPER(rsa, ctx, goto err;);

		blinding = rsa->blinding;

		/* Now unless blinding is disabled, 'blinding' is non-NULL.
		* But the BN_BLINDING object may be owned by some other thread
		* (we don't want to keep it constant and we don't want to use
		* lots of locking to avoid race conditions, so only a single
		* thread can use it; other threads have to use local blinding
		* factors) */
		if (!(rsa->flags & RSA_FLAG_NO_BLINDING))
		if (!BN_BLINDING_convert(&f,rsa->blinding,ctx)) goto err;
		{
		if (blinding == NULL)
		{
		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT, ERR_R_INTERNAL_ERROR);
		goto err;
		}
		}

		if (blinding != NULL)
		{
		if (blinding->thread_id != CRYPTO_thread_id())
		{
		/* we need a local one-time blinding factor */

		blinding = setup_blinding(rsa, ctx);
		if (blinding == NULL)
		goto err;
		local_blinding = 1;
		}
		}

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

		/* do the decrypt */
		if ( (rsa->flags & RSA_FLAG_EXT_PKEY) \|\|
		@@ -376,8 +474,8 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
		goto err;
		}

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

		p=buf;
		j=BN_bn2bin(&ret,p); /* j is only used with no-padding mode */

crypto/rsa/rsa_lib.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -329,6 +329,10 @@ int RSA_blinding_on(RSA rsa, BN_CTX p_ctx)
		if (rsa->blinding != NULL)
		BN_BLINDING_free(rsa->blinding);

		/* NB: similar code appears in setup_blinding (rsa_eay.c);
		* this should be placed in a new function of its own, but for reasons
		* of binary compatibility can't */

		BN_CTX_start(ctx);
		A = BN_CTX_get(ctx);
		if ((RAND_status() == 0) && rsa->d != NULL && rsa->d->d != NULL)
		@@ -345,7 +349,10 @@ int RSA_blinding_on(RSA rsa, BN_CTX p_ctx)

		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);
		if ((rsa->blinding=BN_BLINDING_new(A,Ai,rsa->n)) == NULL) goto err;
		/* to make things thread-safe without excessive locking,
		* rsa->blinding will be used just by the current thread: */
		rsa->blinding->thread_id = CRYPTO_thread_id();
		rsa->flags \|= RSA_FLAG_BLINDING;
		rsa->flags &= ~RSA_FLAG_NO_BLINDING;
		BN_free(Ai);