From: Geoff Thorpe <geoff@openssl.org>
Date: Thu, 25 Mar 2004 02:52:04 +0000 (+0000)
Subject: By adding a BN_CTX parameter to the 'rsa_mod_exp' callback, private key
X-Git-Tag: OpenSSL_0_9_7e~130^2~27
X-Git-Url: https://git.openssl.org/?p=openssl.git;a=commitdiff_plain;h=46ef873f0b3c04b6415cddac5d4a7b27b53cc482;hp=2d2a5ba32a6da293bbe290529293c485d36e1c19

By adding a BN_CTX parameter to the 'rsa_mod_exp' callback, private key
operations no longer require two distinct BN_CTX structures. This may put
more "strain" on the current BN_CTX implementation (which has a fixed limit
to the number of variables it will hold), but so far this limit is not
triggered by any of the tests pass and I will be changing BN_CTX in the
near future to avoid this problem anyway.

This also changes the default RSA implementation code to use the BN_CTX in
favour of initialising some of its variables locally in each function.
---

diff --git a/CHANGES b/CHANGES
index aebf096f9f..6eceebac1b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -4,6 +4,10 @@
 
  Changes between 0.9.7c and 0.9.8  [xx XXX xxxx]
 
+  *) Add a missing BN_CTX parameter to the 'rsa_mod_exp' callback in RSA_METHOD
+     to allow all RSA operations to function using a single BN_CTX.
+     [Geoff Thorpe]
+
   *) Preliminary support for certificate policy evaluation and checking. This
      is initially intended to pass the tests outlined in "Conformance Testing
      of Relying Party Client Certificate Path Processing Logic" v1.07.
diff --git a/crypto/rsa/rsa.h b/crypto/rsa/rsa.h
index 12689fc22d..b3ed1edd3f 100644
--- a/crypto/rsa/rsa.h
+++ b/crypto/rsa/rsa.h
@@ -93,7 +93,7 @@ typedef struct rsa_meth_st
 	int (*rsa_priv_dec)(int flen,const unsigned char *from,
 			    unsigned char *to,
 			    RSA *rsa,int padding);
-	int (*rsa_mod_exp)(BIGNUM *r0,const BIGNUM *I,RSA *rsa); /* Can be null */
+	int (*rsa_mod_exp)(BIGNUM *r0,const BIGNUM *I,RSA *rsa,BN_CTX *ctx); /* Can be null */
 	int (*bn_mod_exp)(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 			  const BIGNUM *m, BN_CTX *ctx,
 			  BN_MONT_CTX *m_ctx); /* Can be null */
diff --git a/crypto/rsa/rsa_eay.c b/crypto/rsa/rsa_eay.c
index 5beb9c9fdf..b66b4bc140 100644
--- a/crypto/rsa/rsa_eay.c
+++ b/crypto/rsa/rsa_eay.c
@@ -72,7 +72,7 @@ static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
 		unsigned char *to, RSA *rsa,int padding);
 static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 		unsigned char *to, RSA *rsa,int padding);
-static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa);
+static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa, BN_CTX *ctx);
 static int RSA_eay_init(RSA *rsa);
 static int RSA_eay_finish(RSA *rsa);
 static RSA_METHOD rsa_pkcs1_eay_meth={
@@ -137,16 +137,18 @@ static int rsa_eay_mont_helper(BN_MONT_CTX **ptr, const BIGNUM *modulus, BN_CTX
 static int RSA_eay_public_encrypt(int flen, const unsigned char *from,
 	     unsigned char *to, RSA *rsa, int padding)
 	{
-	BIGNUM f,ret;
+	BIGNUM *f,*ret;
 	int i,j,k,num=0,r= -1;
 	unsigned char *buf=NULL;
 	BN_CTX *ctx=NULL;
 
-	BN_init(&f);
-	BN_init(&ret);
 	if ((ctx=BN_CTX_new()) == NULL) goto err;
+	BN_CTX_start(ctx);
+	f = BN_CTX_get(ctx);
+	ret = BN_CTX_get(ctx);
 	num=BN_num_bytes(rsa->n);
-	if ((buf=(unsigned char *)OPENSSL_malloc(num)) == NULL)
+	buf = OPENSSL_malloc(num);
+	if (!f || !ret || !buf)
 		{
 		RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT,ERR_R_MALLOC_FAILURE);
 		goto err;
@@ -174,9 +176,9 @@ static int RSA_eay_public_encrypt(int flen, const unsigned char *from,
 		}
 	if (i <= 0) goto err;
 
-	if (BN_bin2bn(buf,num,&f) == NULL) goto err;
+	if (BN_bin2bn(buf,num,f) == NULL) goto err;
 	
-	if (BN_ucmp(&f, rsa->n) >= 0)
+	if (BN_ucmp(f, rsa->n) >= 0)
 		{	
 		/* usually the padding functions would catch this */
 		RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT,RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
@@ -185,21 +187,23 @@ static int RSA_eay_public_encrypt(int flen, const unsigned char *from,
 
 	MONT_HELPER(rsa, ctx, n, rsa->flags & RSA_FLAG_CACHE_PUBLIC, goto err);
 
-	if (!rsa->meth->bn_mod_exp(&ret,&f,rsa->e,rsa->n,ctx,
+	if (!rsa->meth->bn_mod_exp(ret,f,rsa->e,rsa->n,ctx,
 		rsa->_method_mod_n)) goto err;
 
 	/* put in leading 0 bytes if the number is less than the
 	 * length of the modulus */
-	j=BN_num_bytes(&ret);
-	i=BN_bn2bin(&ret,&(to[num-j]));
+	j=BN_num_bytes(ret);
+	i=BN_bn2bin(ret,&(to[num-j]));
 	for (k=0; k<(num-i); k++)
 		to[k]=0;
 
 	r=num;
 err:
-	if (ctx != NULL) BN_CTX_free(ctx);
-	BN_clear_free(&f);
-	BN_clear_free(&ret);
+	if (ctx != NULL)
+		{
+		BN_CTX_end(ctx);
+		BN_CTX_free(ctx);
+		}
 	if (buf != NULL) 
 		{
 		OPENSSL_cleanse(buf,num);
@@ -265,19 +269,20 @@ err:
 static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
 	     unsigned char *to, RSA *rsa, int padding)
 	{
-	BIGNUM f,ret;
+	BIGNUM *f,*ret;
 	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);
-
 	if ((ctx=BN_CTX_new()) == NULL) goto err;
+	BN_CTX_start(ctx);
+	f = BN_CTX_get(ctx);
+	ret = BN_CTX_get(ctx);
 	num=BN_num_bytes(rsa->n);
-	if ((buf=(unsigned char *)OPENSSL_malloc(num)) == NULL)
+	buf = OPENSSL_malloc(num);
+	if(!f || !ret || !buf)
 		{
 		RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT,ERR_R_MALLOC_FAILURE);
 		goto err;
@@ -298,9 +303,9 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
 		}
 	if (i <= 0) goto err;
 
-	if (BN_bin2bn(buf,num,&f) == NULL) goto err;
+	if (BN_bin2bn(buf,num,f) == NULL) goto err;
 	
-	if (BN_ucmp(&f, rsa->n) >= 0)
+	if (BN_ucmp(f, rsa->n) >= 0)
 		{	
 		/* usually the padding functions would catch this */
 		RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT,RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
@@ -339,7 +344,7 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
 		}
 
 	if (blinding)
-		if (!BN_BLINDING_convert(&f, blinding, ctx)) goto err;
+		if (!BN_BLINDING_convert(f, blinding, ctx)) goto err;
 
 	if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
 		((rsa->p != NULL) &&
@@ -347,29 +352,31 @@ static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
 		(rsa->dmp1 != NULL) &&
 		(rsa->dmq1 != NULL) &&
 		(rsa->iqmp != NULL)) )
-		{ if (!rsa->meth->rsa_mod_exp(&ret,&f,rsa)) goto err; }
+		{ if (!rsa->meth->rsa_mod_exp(ret,f,rsa,ctx)) goto err; }
 	else
 		{
 		MONT_HELPER(rsa, ctx, n, rsa->flags & RSA_FLAG_CACHE_PUBLIC, goto err);
-		if (!rsa->meth->bn_mod_exp(&ret,&f,rsa->d,rsa->n,ctx,
+		if (!rsa->meth->bn_mod_exp(ret,f,rsa->d,rsa->n,ctx,
 				rsa->_method_mod_n)) goto err;
 		}
 
 	if (blinding)
-		if (!BN_BLINDING_invert(&ret, blinding, ctx)) goto err;
+		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 */
-	j=BN_num_bytes(&ret);
-	i=BN_bn2bin(&ret,&(to[num-j]));
+	j=BN_num_bytes(ret);
+	i=BN_bn2bin(ret,&(to[num-j]));
 	for (k=0; k<(num-i); k++)
 		to[k]=0;
 
 	r=num;
 err:
-	if (ctx != NULL) BN_CTX_free(ctx);
-	BN_clear_free(&ret);
-	BN_clear_free(&f);
+	if (ctx != NULL)
+		{
+		BN_CTX_end(ctx);
+		BN_CTX_free(ctx);
+		}
 	if (local_blinding)
 		BN_BLINDING_free(blinding);
 	if (buf != NULL)
@@ -383,7 +390,7 @@ err:
 static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 	     unsigned char *to, RSA *rsa, int padding)
 	{
-	BIGNUM f,ret;
+	BIGNUM *f,*ret;
 	int j,num=0,r= -1;
 	unsigned char *p;
 	unsigned char *buf=NULL;
@@ -391,14 +398,13 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 	int local_blinding = 0;
 	BN_BLINDING *blinding = NULL;
 
-	BN_init(&f);
-	BN_init(&ret);
-	ctx=BN_CTX_new();
-	if (ctx == NULL) goto err;
-
+	if((ctx = BN_CTX_new()) == NULL) goto err;
+	BN_CTX_start(ctx);
+	f = BN_CTX_get(ctx);
+	ret = BN_CTX_get(ctx);
 	num=BN_num_bytes(rsa->n);
-
-	if ((buf=(unsigned char *)OPENSSL_malloc(num)) == NULL)
+	buf = OPENSSL_malloc(num);
+	if(!f || !ret || !buf)
 		{
 		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,ERR_R_MALLOC_FAILURE);
 		goto err;
@@ -413,9 +419,9 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 		}
 
 	/* make data into a big number */
-	if (BN_bin2bn(from,(int)flen,&f) == NULL) goto err;
+	if (BN_bin2bn(from,(int)flen,f) == NULL) goto err;
 
-	if (BN_ucmp(&f, rsa->n) >= 0)
+	if (BN_ucmp(f, rsa->n) >= 0)
 		{
 		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 		goto err;
@@ -453,7 +459,7 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 		}
 
 	if (blinding)
-		if (!BN_BLINDING_convert(&f, blinding, ctx)) goto err;
+		if (!BN_BLINDING_convert(f, blinding, ctx)) goto err;
 
 	/* do the decrypt */
 	if ( (rsa->flags & RSA_FLAG_EXT_PKEY) ||
@@ -462,20 +468,20 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 		(rsa->dmp1 != NULL) &&
 		(rsa->dmq1 != NULL) &&
 		(rsa->iqmp != NULL)) )
-		{ if (!rsa->meth->rsa_mod_exp(&ret,&f,rsa)) goto err; }
+		{ if (!rsa->meth->rsa_mod_exp(ret,f,rsa,ctx)) goto err; }
 	else
 		{
 		MONT_HELPER(rsa, ctx, n, rsa->flags & RSA_FLAG_CACHE_PUBLIC, goto err);
-		if (!rsa->meth->bn_mod_exp(&ret,&f,rsa->d,rsa->n,ctx,
+		if (!rsa->meth->bn_mod_exp(ret,f,rsa->d,rsa->n,ctx,
 				rsa->_method_mod_n))
 			goto err;
 		}
 
 	if (blinding)
-		if (!BN_BLINDING_invert(&ret, blinding, ctx)) goto err;
+		if (!BN_BLINDING_invert(ret, blinding, ctx)) goto err;
 
 	p=buf;
-	j=BN_bn2bin(&ret,p); /* j is only used with no-padding mode */
+	j=BN_bn2bin(ret,p); /* j is only used with no-padding mode */
 
 	switch (padding)
 		{
@@ -501,9 +507,11 @@ static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
 		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,RSA_R_PADDING_CHECK_FAILED);
 
 err:
-	if (ctx != NULL) BN_CTX_free(ctx);
-	BN_clear_free(&f);
-	BN_clear_free(&ret);
+	if (ctx != NULL)
+		{
+		BN_CTX_end(ctx);
+		BN_CTX_free(ctx);
+		}
 	if (local_blinding)
 		BN_BLINDING_free(blinding);
 	if (buf != NULL)
@@ -518,20 +526,19 @@ err:
 static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
 	     unsigned char *to, RSA *rsa, int padding)
 	{
-	BIGNUM f,ret;
+	BIGNUM *f,*ret;
 	int i,num=0,r= -1;
 	unsigned char *p;
 	unsigned char *buf=NULL;
 	BN_CTX *ctx=NULL;
 
-	BN_init(&f);
-	BN_init(&ret);
-	ctx=BN_CTX_new();
-	if (ctx == NULL) goto err;
-
+	if((ctx = BN_CTX_new()) == NULL) goto err;
+	BN_CTX_start(ctx);
+	f = BN_CTX_get(ctx);
+	ret = BN_CTX_get(ctx);
 	num=BN_num_bytes(rsa->n);
-	buf=(unsigned char *)OPENSSL_malloc(num);
-	if (buf == NULL)
+	buf = OPENSSL_malloc(num);
+	if(!f || !ret || !buf)
 		{
 		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,ERR_R_MALLOC_FAILURE);
 		goto err;
@@ -545,9 +552,9 @@ static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
 		goto err;
 		}
 
-	if (BN_bin2bn(from,flen,&f) == NULL) goto err;
+	if (BN_bin2bn(from,flen,f) == NULL) goto err;
 
-	if (BN_ucmp(&f, rsa->n) >= 0)
+	if (BN_ucmp(f, rsa->n) >= 0)
 		{
 		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 		goto err;
@@ -555,11 +562,11 @@ static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
 
 	MONT_HELPER(rsa, ctx, n, rsa->flags & RSA_FLAG_CACHE_PUBLIC, goto err);
 
-	if (!rsa->meth->bn_mod_exp(&ret,&f,rsa->e,rsa->n,ctx,
+	if (!rsa->meth->bn_mod_exp(ret,f,rsa->e,rsa->n,ctx,
 		rsa->_method_mod_n)) goto err;
 
 	p=buf;
-	i=BN_bn2bin(&ret,p);
+	i=BN_bn2bin(ret,p);
 
 	switch (padding)
 		{
@@ -577,9 +584,11 @@ static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
 		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,RSA_R_PADDING_CHECK_FAILED);
 
 err:
-	if (ctx != NULL) BN_CTX_free(ctx);
-	BN_clear_free(&f);
-	BN_clear_free(&ret);
+	if (ctx != NULL)
+		{
+		BN_CTX_end(ctx);
+		BN_CTX_free(ctx);
+		}
 	if (buf != NULL)
 		{
 		OPENSSL_cleanse(buf,num);
@@ -588,37 +597,36 @@ err:
 	return(r);
 	}
 
-static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
+static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
-	BIGNUM r1,m1,vrfy;
+	BIGNUM *r1,*m1,*vrfy;
 	int ret=0;
-	BN_CTX *ctx;
 
-	BN_init(&m1);
-	BN_init(&r1);
-	BN_init(&vrfy);
-	if ((ctx=BN_CTX_new()) == NULL) goto err;
+	BN_CTX_start(ctx);
+	r1 = BN_CTX_get(ctx);
+	m1 = BN_CTX_get(ctx);
+	vrfy = BN_CTX_get(ctx);
 
 	MONT_HELPER(rsa, ctx, p, rsa->flags & RSA_FLAG_CACHE_PRIVATE, goto err);
 	MONT_HELPER(rsa, ctx, q, rsa->flags & RSA_FLAG_CACHE_PRIVATE, goto err);
 	MONT_HELPER(rsa, ctx, n, rsa->flags & RSA_FLAG_CACHE_PUBLIC, goto err);
 
-	if (!BN_mod(&r1,I,rsa->q,ctx)) goto err;
-	if (!rsa->meth->bn_mod_exp(&m1,&r1,rsa->dmq1,rsa->q,ctx,
+	if (!BN_mod(r1,I,rsa->q,ctx)) goto err;
+	if (!rsa->meth->bn_mod_exp(m1,r1,rsa->dmq1,rsa->q,ctx,
 		rsa->_method_mod_q)) goto err;
 
-	if (!BN_mod(&r1,I,rsa->p,ctx)) goto err;
-	if (!rsa->meth->bn_mod_exp(r0,&r1,rsa->dmp1,rsa->p,ctx,
+	if (!BN_mod(r1,I,rsa->p,ctx)) goto err;
+	if (!rsa->meth->bn_mod_exp(r0,r1,rsa->dmp1,rsa->p,ctx,
 		rsa->_method_mod_p)) goto err;
 
-	if (!BN_sub(r0,r0,&m1)) goto err;
+	if (!BN_sub(r0,r0,m1)) goto err;
 	/* This will help stop the size of r0 increasing, which does
 	 * affect the multiply if it optimised for a power of 2 size */
 	if (BN_get_sign(r0))
 		if (!BN_add(r0,r0,rsa->p)) goto err;
 
-	if (!BN_mul(&r1,r0,rsa->iqmp,ctx)) goto err;
-	if (!BN_mod(r0,&r1,rsa->p,ctx)) goto err;
+	if (!BN_mul(r1,r0,rsa->iqmp,ctx)) goto err;
+	if (!BN_mod(r0,r1,rsa->p,ctx)) goto err;
 	/* If p < q it is occasionally possible for the correction of
          * adding 'p' if r0 is negative above to leave the result still
 	 * negative. This can break the private key operations: the following
@@ -628,21 +636,21 @@ static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
          */
 	if (BN_get_sign(r0))
 		if (!BN_add(r0,r0,rsa->p)) goto err;
-	if (!BN_mul(&r1,r0,rsa->q,ctx)) goto err;
-	if (!BN_add(r0,&r1,&m1)) goto err;
+	if (!BN_mul(r1,r0,rsa->q,ctx)) goto err;
+	if (!BN_add(r0,r1,m1)) goto err;
 
 	if (rsa->e && rsa->n)
 		{
-		if (!rsa->meth->bn_mod_exp(&vrfy,r0,rsa->e,rsa->n,ctx,rsa->_method_mod_n)) goto err;
+		if (!rsa->meth->bn_mod_exp(vrfy,r0,rsa->e,rsa->n,ctx,rsa->_method_mod_n)) goto err;
 		/* If 'I' was greater than (or equal to) rsa->n, the operation
 		 * will be equivalent to using 'I mod n'. However, the result of
 		 * the verify will *always* be less than 'n' so we don't check
 		 * for absolute equality, just congruency. */
-		if (!BN_sub(&vrfy, &vrfy, I)) goto err;
-		if (!BN_mod(&vrfy, &vrfy, rsa->n, ctx)) goto err;
-		if (BN_get_sign(&vrfy))
-			if (!BN_add(&vrfy, &vrfy, rsa->n)) goto err;
-		if (!BN_is_zero(&vrfy))
+		if (!BN_sub(vrfy, vrfy, I)) goto err;
+		if (!BN_mod(vrfy, vrfy, rsa->n, ctx)) goto err;
+		if (BN_get_sign(vrfy))
+			if (!BN_add(vrfy, vrfy, rsa->n)) goto err;
+		if (!BN_is_zero(vrfy))
 			/* 'I' and 'vrfy' aren't congruent mod n. Don't leak
 			 * miscalculated CRT output, just do a raw (slower)
 			 * mod_exp and return that instead. */
@@ -651,10 +659,7 @@ static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 		}
 	ret=1;
 err:
-	BN_clear_free(&m1);
-	BN_clear_free(&r1);
-	BN_clear_free(&vrfy);
-	BN_CTX_free(ctx);
+	BN_CTX_end(ctx);
 	return(ret);
 	}
 
diff --git a/engines/e_aep.c b/engines/e_aep.c
index 5083c80ef8..aa4fe75704 100644
--- a/engines/e_aep.c
+++ b/engines/e_aep.c
@@ -106,7 +106,7 @@ static AEP_RV aep_mod_exp_crt(BIGNUM *r,const  BIGNUM *a, const BIGNUM *p,
 
 /* RSA stuff */
 #ifndef OPENSSL_NO_RSA
-static int aep_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa);
+static int aep_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx);
 #endif
 
 /* This function is aliased to mod_exp (with the mont stuff dropped). */
@@ -745,15 +745,11 @@ static int aep_rand_status(void)
 #endif
 
 #ifndef OPENSSL_NO_RSA
-static int aep_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
+static int aep_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
-	BN_CTX *ctx = NULL;
 	int to_return = 0;
 	AEP_RV rv = AEP_R_OK;
 
-	if ((ctx = BN_CTX_new()) == NULL)
-		goto err;
-
 	if (!aep_dso)
 		{
 		AEPHKerr(AEPHK_F_AEP_RSA_MOD_EXP,AEPHK_R_NOT_LOADED);
@@ -767,7 +763,7 @@ static int aep_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 
 		if (rv == FAIL_TO_SW){
 			const RSA_METHOD *meth = RSA_PKCS1_SSLeay();
-			to_return = (*meth->rsa_mod_exp)(r0, I, rsa);
+			to_return = (*meth->rsa_mod_exp)(r0, I, rsa, ctx);
 			goto err;
 		}
 		else if (rv != AEP_R_OK)
@@ -790,8 +786,6 @@ static int aep_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 	to_return = 1;
 
  err:
-	if(ctx)
-		BN_CTX_free(ctx);
 	return to_return;
 }
 #endif
diff --git a/engines/e_atalla.c b/engines/e_atalla.c
index 79abc70678..cc6c9695f0 100644
--- a/engines/e_atalla.c
+++ b/engines/e_atalla.c
@@ -86,7 +86,7 @@ static int atalla_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 
 #ifndef OPENSSL_NO_RSA
 /* RSA stuff */
-static int atalla_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa);
+static int atalla_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx);
 #endif
 /* This function is aliased to mod_exp (with the mont stuff dropped). */
 static int atalla_mod_exp_mont(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
@@ -502,9 +502,8 @@ err:
 	}
 
 #ifndef OPENSSL_NO_RSA
-static int atalla_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
+static int atalla_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
-	BN_CTX *ctx = NULL;
 	int to_return = 0;
 
 	if(!atalla_dso)
@@ -512,8 +511,6 @@ static int atalla_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 		ATALLAerr(ATALLA_F_ATALLA_RSA_MOD_EXP,ATALLA_R_NOT_LOADED);
 		goto err;
 		}
-	if((ctx = BN_CTX_new()) == NULL)
-		goto err;
 	if(!rsa->d || !rsa->n)
 		{
 		ATALLAerr(ATALLA_F_ATALLA_RSA_MOD_EXP,ATALLA_R_MISSING_KEY_COMPONENTS);
@@ -521,8 +518,6 @@ static int atalla_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 		}
 	to_return = atalla_mod_exp(r0, I, rsa->d, rsa->n, ctx);
 err:
-	if(ctx)
-		BN_CTX_free(ctx);
 	return to_return;
 	}
 #endif
diff --git a/engines/e_cswift.c b/engines/e_cswift.c
index 793aaccb11..cc39cd4947 100644
--- a/engines/e_cswift.c
+++ b/engines/e_cswift.c
@@ -103,7 +103,7 @@ static int cswift_mod_exp_crt(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 
 #ifndef OPENSSL_NO_RSA
 /* RSA stuff */
-static int cswift_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa);
+static int cswift_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx);
 #endif
 /* This function is aliased to mod_exp (with the mont stuff dropped). */
 static int cswift_mod_exp_mont(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
@@ -668,13 +668,10 @@ err:
 	}
  
 #ifndef OPENSSL_NO_RSA
-static int cswift_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
+static int cswift_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
-	BN_CTX *ctx;
 	int to_return = 0;
 
-	if((ctx = BN_CTX_new()) == NULL)
-		goto err;
 	if(!rsa->p || !rsa->q || !rsa->dmp1 || !rsa->dmq1 || !rsa->iqmp)
 		{
 		CSWIFTerr(CSWIFT_F_CSWIFT_RSA_MOD_EXP,CSWIFT_R_MISSING_KEY_COMPONENTS);
@@ -683,8 +680,6 @@ static int cswift_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 	to_return = cswift_mod_exp_crt(r0, I, rsa->p, rsa->q, rsa->dmp1,
 		rsa->dmq1, rsa->iqmp, ctx);
 err:
-	if(ctx)
-		BN_CTX_free(ctx);
 	return to_return;
 	}
 #endif
diff --git a/engines/e_ncipher.c b/engines/e_ncipher.c
index e416cffedb..e075d1b459 100644
--- a/engines/e_ncipher.c
+++ b/engines/e_ncipher.c
@@ -102,7 +102,7 @@ static int hwcrhk_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 
 #ifndef OPENSSL_NO_RSA
 /* RSA stuff */
-static int hwcrhk_rsa_mod_exp(BIGNUM *r, const BIGNUM *I, RSA *rsa);
+static int hwcrhk_rsa_mod_exp(BIGNUM *r, const BIGNUM *I, RSA *rsa, BN_CTX *ctx);
 #endif
 /* This function is aliased to mod_exp (with the mont stuff dropped). */
 static int hwcrhk_mod_exp_mont(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
@@ -946,7 +946,7 @@ err:
 	}
 
 #ifndef OPENSSL_NO_RSA 
-static int hwcrhk_rsa_mod_exp(BIGNUM *r, const BIGNUM *I, RSA *rsa)
+static int hwcrhk_rsa_mod_exp(BIGNUM *r, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
 	char tempbuf[1024];
 	HWCryptoHook_ErrMsgBuf rmsg;
diff --git a/engines/e_nuron.c b/engines/e_nuron.c
index e3a9406c49..4df6f0495a 100644
--- a/engines/e_nuron.c
+++ b/engines/e_nuron.c
@@ -192,9 +192,9 @@ static int nuron_mod_exp(BIGNUM *r,const BIGNUM *a,const BIGNUM *p,
 	}
 
 #ifndef OPENSSL_NO_RSA
-static int nuron_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
+static int nuron_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
-	return nuron_mod_exp(r0,I,rsa->d,rsa->n,NULL);
+	return nuron_mod_exp(r0,I,rsa->d,rsa->n,ctx);
 	}
 #endif
 
diff --git a/engines/e_ubsec.c b/engines/e_ubsec.c
index 094458887c..5aa29f1c53 100644
--- a/engines/e_ubsec.c
+++ b/engines/e_ubsec.c
@@ -89,7 +89,7 @@ static int ubsec_mod_exp_crt(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 			const BIGNUM *q, const BIGNUM *dp,
 			const BIGNUM *dq, const BIGNUM *qinv, BN_CTX *ctx);
 #ifndef OPENSSL_NO_RSA
-static int ubsec_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa);
+static int ubsec_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx);
 #endif
 static int ubsec_mod_exp_mont(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 		const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
@@ -590,14 +590,10 @@ static int ubsec_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
 	}
 
 #ifndef OPENSSL_NO_RSA
-static int ubsec_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
+static int ubsec_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 	{
-	BN_CTX *ctx;
 	int to_return = 0;
 
-	if((ctx = BN_CTX_new()) == NULL)
-		goto err;
-
 	if(!rsa->p || !rsa->q || !rsa->dmp1 || !rsa->dmq1 || !rsa->iqmp)
 		{
 		UBSECerr(UBSEC_F_UBSEC_RSA_MOD_EXP, UBSEC_R_MISSING_KEY_COMPONENTS);
@@ -612,11 +608,9 @@ static int ubsec_rsa_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
 	   * Do in software as hardware failed.
 	   */
 	   const RSA_METHOD *meth = RSA_PKCS1_SSLeay();
-	   to_return = (*meth->rsa_mod_exp)(r0, I, rsa);
+	   to_return = (*meth->rsa_mod_exp)(r0, I, rsa, ctx);
 	}
 err:
-	if(ctx)
-		BN_CTX_free(ctx);
 	return to_return;
 	}
 #endif