openssl/crypto/rsa/rsa_eay.c

/* crypto/rsa/rsa_eay.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 * 
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 * 
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from 
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 * 
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/rand.h>

#ifndef RSA_NULL

static int RSA_eay_public_encrypt(int flen, const unsigned char *from,
		unsigned char *to, RSA *rsa,int padding);
static int RSA_eay_private_encrypt(int flen, const unsigned char *from,
		unsigned char *to, RSA *rsa,int padding);
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_init(RSA *rsa);
static int RSA_eay_finish(RSA *rsa);
static RSA_METHOD rsa_pkcs1_eay_meth={
	"Eric Young's PKCS#1 RSA",
	RSA_eay_public_encrypt,
	RSA_eay_public_decrypt, /* signature verification */
	RSA_eay_private_encrypt, /* signing */
	RSA_eay_private_decrypt,
	RSA_eay_mod_exp,
	BN_mod_exp_mont, /* XXX probably we should not use Montgomery if  e == 3 */
	RSA_eay_init,
	RSA_eay_finish,
	0, /* flags */
	NULL,
	0, /* rsa_sign */
	0, /* rsa_verify */
	NULL /* rsa_keygen */
	};

const RSA_METHOD *RSA_PKCS1_SSLeay(void)
	{
	return(&rsa_pkcs1_eay_meth);
	}

/* Static helper to reduce oodles of code duplication. As a slight
 * optimisation, the "MONT_HELPER() macro must be used as front-end to this
 * function, to prevent unnecessary function calls - there is an initial test
 * that is performed by the macro-generated code. */
static int rsa_eay_mont_helper(BN_MONT_CTX **ptr, const BIGNUM *modulus, BN_CTX *ctx)
	{
	BN_MONT_CTX *bn_mont_ctx;
	if((bn_mont_ctx = BN_MONT_CTX_new()) == NULL)
		return 0;
	if(!BN_MONT_CTX_set(bn_mont_ctx, modulus, ctx))
		{
		BN_MONT_CTX_free(bn_mont_ctx);
		return 0;
		}
	if (*ptr == NULL) /* other thread may have finished first */
		{
		CRYPTO_w_lock(CRYPTO_LOCK_RSA);
		if (*ptr == NULL) /* check again in the lock to stop races */
			{
			*ptr = bn_mont_ctx;
			bn_mont_ctx = NULL;
			}
		CRYPTO_w_unlock(CRYPTO_LOCK_RSA);
		}
	if (bn_mont_ctx)
		BN_MONT_CTX_free(bn_mont_ctx);
	return 1;
	}
/* Usage example;
 *    MONT_HELPER(rsa, bn_ctx, p, rsa->flags & RSA_FLAG_CACHE_PRIVATE, goto err);
 */
#define MONT_HELPER(rsa, ctx, m, pre_cond, err_instr) \
	if((pre_cond) && ((rsa)->_method_mod_##m == NULL) && \
			!rsa_eay_mont_helper(&((rsa)->_method_mod_##m), \
				(rsa)->m, (ctx))) \
		err_instr

static int RSA_eay_public_encrypt(int flen, const unsigned char *from,
	     unsigned char *to, RSA *rsa, int padding)
	{
	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;
	num=BN_num_bytes(rsa->n);
	if ((buf=(unsigned char *)OPENSSL_malloc(num)) == NULL)
		{
		RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT,ERR_R_MALLOC_FAILURE);
		goto err;
		}

	switch (padding)
		{
	case RSA_PKCS1_PADDING:
		i=RSA_padding_add_PKCS1_type_2(buf,num,from,flen);
		break;
#ifndef OPENSSL_NO_SHA
	case RSA_PKCS1_OAEP_PADDING:
	        i=RSA_padding_add_PKCS1_OAEP(buf,num,from,flen,NULL,0);
		break;
#endif
	case RSA_SSLV23_PADDING:
		i=RSA_padding_add_SSLv23(buf,num,from,flen);
		break;
	case RSA_NO_PADDING:
		i=RSA_padding_add_none(buf,num,from,flen);
		break;
	default:
		RSAerr(RSA_F_RSA_EAY_PUBLIC_ENCRYPT,RSA_R_UNKNOWN_PADDING_TYPE);
		goto err;
		}
	if (i <= 0) goto err;

	if (BN_bin2bn(buf,num,&f) == NULL) goto err;
	
	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);
		goto err;
		}

	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,
		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]));
	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 (buf != NULL) 
		{
		OPENSSL_cleanse(buf,num);
		OPENSSL_free(buf);
		}
	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)

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)
	{
	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;
	num=BN_num_bytes(rsa->n);
	if ((buf=(unsigned char *)OPENSSL_malloc(num)) == NULL)
		{
		RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT,ERR_R_MALLOC_FAILURE);
		goto err;
		}

	switch (padding)
		{
	case RSA_PKCS1_PADDING:
		i=RSA_padding_add_PKCS1_type_1(buf,num,from,flen);
		break;
	case RSA_NO_PADDING:
		i=RSA_padding_add_none(buf,num,from,flen);
		break;
	case RSA_SSLV23_PADDING:
	default:
		RSAerr(RSA_F_RSA_EAY_PRIVATE_ENCRYPT,RSA_R_UNKNOWN_PADDING_TYPE);
		goto err;
		}
	if (i <= 0) goto err;

	if (BN_bin2bn(buf,num,&f) == NULL) goto err;
	
	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);
		goto err;
		}

	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 (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) &&
		(rsa->q != NULL) &&
		(rsa->dmp1 != NULL) &&
		(rsa->dmq1 != NULL) &&
		(rsa->iqmp != NULL)) )
		{ if (!rsa->meth->rsa_mod_exp(&ret,&f,rsa)) 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,
				rsa->_method_mod_n)) 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 */
	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 (local_blinding)
		BN_BLINDING_free(blinding);
	if (buf != NULL)
		{
		OPENSSL_cleanse(buf,num);
		OPENSSL_free(buf);
		}
	return(r);
	}

static int RSA_eay_private_decrypt(int flen, const unsigned char *from,
	     unsigned char *to, RSA *rsa, int padding)
	{
	BIGNUM f,ret;
	int j,num=0,r= -1;
	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);
	ctx=BN_CTX_new();
	if (ctx == NULL) goto err;

	num=BN_num_bytes(rsa->n);

	if ((buf=(unsigned char *)OPENSSL_malloc(num)) == NULL)
		{
		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,ERR_R_MALLOC_FAILURE);
		goto err;
		}

	/* This check was for equality but PGP does evil things
	 * and chops off the top '0' bytes */
	if (flen > num)
		{
		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,RSA_R_DATA_GREATER_THAN_MOD_LEN);
		goto err;
		}

	/* make data into a big number */
	if (BN_bin2bn(from,(int)flen,&f) == NULL) goto err;

	if (BN_ucmp(&f, rsa->n) >= 0)
		{
		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
		goto err;
		}

	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 (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) ||
		((rsa->p != NULL) &&
		(rsa->q != NULL) &&
		(rsa->dmp1 != NULL) &&
		(rsa->dmq1 != NULL) &&
		(rsa->iqmp != NULL)) )
		{ if (!rsa->meth->rsa_mod_exp(&ret,&f,rsa)) 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,
				rsa->_method_mod_n))
			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 */

	switch (padding)
		{
	case RSA_PKCS1_PADDING:
		r=RSA_padding_check_PKCS1_type_2(to,num,buf,j,num);
		break;
#ifndef OPENSSL_NO_SHA
        case RSA_PKCS1_OAEP_PADDING:
	        r=RSA_padding_check_PKCS1_OAEP(to,num,buf,j,num,NULL,0);
                break;
#endif
 	case RSA_SSLV23_PADDING:
		r=RSA_padding_check_SSLv23(to,num,buf,j,num);
		break;
	case RSA_NO_PADDING:
		r=RSA_padding_check_none(to,num,buf,j,num);
		break;
	default:
		RSAerr(RSA_F_RSA_EAY_PRIVATE_DECRYPT,RSA_R_UNKNOWN_PADDING_TYPE);
		goto err;
		}
	if (r < 0)
		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 (local_blinding)
		BN_BLINDING_free(blinding);
	if (buf != NULL)
		{
		OPENSSL_cleanse(buf,num);
		OPENSSL_free(buf);
		}
	return(r);
	}

/* signature verification */
static int RSA_eay_public_decrypt(int flen, const unsigned char *from,
	     unsigned char *to, RSA *rsa, int padding)
	{
	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;

	num=BN_num_bytes(rsa->n);
	buf=(unsigned char *)OPENSSL_malloc(num);
	if (buf == NULL)
		{
		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,ERR_R_MALLOC_FAILURE);
		goto err;
		}

	/* This check was for equality but PGP does evil things
	 * and chops off the top '0' bytes */
	if (flen > num)
		{
		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,RSA_R_DATA_GREATER_THAN_MOD_LEN);
		goto err;
		}

	if (BN_bin2bn(from,flen,&f) == NULL) goto err;

	if (BN_ucmp(&f, rsa->n) >= 0)
		{
		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
		goto err;
		}

	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,
		rsa->_method_mod_n)) goto err;

	p=buf;
	i=BN_bn2bin(&ret,p);

	switch (padding)
		{
	case RSA_PKCS1_PADDING:
		r=RSA_padding_check_PKCS1_type_1(to,num,buf,i,num);
		break;
	case RSA_NO_PADDING:
		r=RSA_padding_check_none(to,num,buf,i,num);
		break;
	default:
		RSAerr(RSA_F_RSA_EAY_PUBLIC_DECRYPT,RSA_R_UNKNOWN_PADDING_TYPE);
		goto err;
		}
	if (r < 0)
		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 (buf != NULL)
		{
		OPENSSL_cleanse(buf,num);
		OPENSSL_free(buf);
		}
	return(r);
	}

static int RSA_eay_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
	{
	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;

	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,
		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,
		rsa->_method_mod_p)) 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 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
	 * second correction should *always* correct this rare occurrence.
	 * This will *never* happen with OpenSSL generated keys because
         * they ensure p > q [steve]
         */
	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 (rsa->e && rsa->n)
		{
		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))
			/* '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. */
			if (!rsa->meth->bn_mod_exp(r0,I,rsa->d,rsa->n,ctx,
					rsa->_method_mod_n)) goto err;
		}
	ret=1;
err:
	BN_clear_free(&m1);
	BN_clear_free(&r1);
	BN_clear_free(&vrfy);
	BN_CTX_free(ctx);
	return(ret);
	}

static int RSA_eay_init(RSA *rsa)
	{
	rsa->flags|=RSA_FLAG_CACHE_PUBLIC|RSA_FLAG_CACHE_PRIVATE;
	return(1);
	}

static int RSA_eay_finish(RSA *rsa)
	{
	if (rsa->_method_mod_n != NULL)
		BN_MONT_CTX_free(rsa->_method_mod_n);
	if (rsa->_method_mod_p != NULL)
		BN_MONT_CTX_free(rsa->_method_mod_p);
	if (rsa->_method_mod_q != NULL)
		BN_MONT_CTX_free(rsa->_method_mod_q);
	return(1);
	}

#endif