/* $OpenBSD: rsa_sign.c,v 1.26 2017/01/29 17:49:23 beck Exp $ */
/* 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 <string.h>

#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/objects.h>
#include <openssl/rsa.h>
#include <openssl/x509.h>

#include "rsa_locl.h"

/* Size of an SSL signature: MD5+SHA1 */
#define SSL_SIG_LENGTH	36

int
RSA_sign(int type, const unsigned char *m, unsigned int m_len,
    unsigned char *sigret, unsigned int *siglen, RSA *rsa)
{
	X509_SIG sig;
	ASN1_TYPE parameter;
	int i, j, ret = 1;
	unsigned char *p, *tmps = NULL;
	const unsigned char *s = NULL;
	X509_ALGOR algor;
	ASN1_OCTET_STRING digest;

	if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_sign)
		return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa);

	/* Special case: SSL signature, just check the length */
	if (type == NID_md5_sha1) {
		if (m_len != SSL_SIG_LENGTH) {
			RSAerror(RSA_R_INVALID_MESSAGE_LENGTH);
			return 0;
		}
		i = SSL_SIG_LENGTH;
		s = m;
	} else {
		sig.algor = &algor;
		sig.algor->algorithm = OBJ_nid2obj(type);
		if (sig.algor->algorithm == NULL) {
			RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE);
			return 0;
		}
		if (sig.algor->algorithm->length == 0) {
			RSAerror(RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD);
			return 0;
		}
		parameter.type = V_ASN1_NULL;
		parameter.value.ptr = NULL;
		sig.algor->parameter = &parameter;

		sig.digest = &digest;
		sig.digest->data = (unsigned char *)m; /* TMP UGLY CAST */
		sig.digest->length = m_len;

		i = i2d_X509_SIG(&sig, NULL);
	}
	j = RSA_size(rsa);
	if (i > j - RSA_PKCS1_PADDING_SIZE) {
		RSAerror(RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY);
		return 0;
	}
	if (type != NID_md5_sha1) {
		tmps = malloc(j + 1);
		if (tmps == NULL) {
			RSAerror(ERR_R_MALLOC_FAILURE);
			return 0;
		}
		p = tmps;
		i2d_X509_SIG(&sig, &p);
		s = tmps;
	}
	i = RSA_private_encrypt(i, s, sigret, rsa, RSA_PKCS1_PADDING);
	if (i <= 0)
		ret = 0;
	else
		*siglen = i;

	if (type != NID_md5_sha1) {
		explicit_bzero(tmps, (unsigned int)j + 1);
		free(tmps);
	}
	return (ret);
}

int
int_rsa_verify(int dtype, const unsigned char *m, unsigned int m_len,
    unsigned char *rm, size_t *prm_len, const unsigned char *sigbuf,
    size_t siglen, RSA *rsa)
{
	int i, ret = 0, sigtype;
	unsigned char *s;
	X509_SIG *sig = NULL;

	if (siglen != (unsigned int)RSA_size(rsa)) {
		RSAerror(RSA_R_WRONG_SIGNATURE_LENGTH);
		return 0;
	}

	if ((dtype == NID_md5_sha1) && rm) {
		i = RSA_public_decrypt((int)siglen, sigbuf, rm, rsa,
		    RSA_PKCS1_PADDING);
		if (i <= 0)
			return 0;
		*prm_len = i;
		return 1;
	}

	s = malloc(siglen);
	if (s == NULL) {
		RSAerror(ERR_R_MALLOC_FAILURE);
		goto err;
	}
	if (dtype == NID_md5_sha1 && m_len != SSL_SIG_LENGTH) {
		RSAerror(RSA_R_INVALID_MESSAGE_LENGTH);
		goto err;
	}
	i = RSA_public_decrypt((int)siglen, sigbuf, s, rsa, RSA_PKCS1_PADDING);

	if (i <= 0)
		goto err;

	/* Special case: SSL signature */
	if (dtype == NID_md5_sha1) {
		if (i != SSL_SIG_LENGTH || memcmp(s, m, SSL_SIG_LENGTH))
			RSAerror(RSA_R_BAD_SIGNATURE);
		else
			ret = 1;
	} else {
		const unsigned char *p = s;

		sig = d2i_X509_SIG(NULL, &p, (long)i);

		if (sig == NULL)
			goto err;

		/* Excess data can be used to create forgeries */
		if (p != s + i) {
			RSAerror(RSA_R_BAD_SIGNATURE);
			goto err;
		}

		/* Parameters to the signature algorithm can also be used to
		   create forgeries */
		if (sig->algor->parameter &&
		    ASN1_TYPE_get(sig->algor->parameter) != V_ASN1_NULL) {
			RSAerror(RSA_R_BAD_SIGNATURE);
			goto err;
		}

		sigtype = OBJ_obj2nid(sig->algor->algorithm);

		if (sigtype != dtype) {
			RSAerror(RSA_R_ALGORITHM_MISMATCH);
			goto err;
		}
		if (rm) {
			const EVP_MD *md;

			md = EVP_get_digestbynid(dtype);
			if (md && (EVP_MD_size(md) != sig->digest->length))
				RSAerror(RSA_R_INVALID_DIGEST_LENGTH);
			else {
				memcpy(rm, sig->digest->data,
				    sig->digest->length);
				*prm_len = sig->digest->length;
				ret = 1;
			}
		} else if ((unsigned int)sig->digest->length != m_len ||
		    memcmp(m, sig->digest->data, m_len) != 0) {
			RSAerror(RSA_R_BAD_SIGNATURE);
		} else
			ret = 1;
	}
err:
	if (sig != NULL)
		X509_SIG_free(sig);
	if (s != NULL) {
		explicit_bzero(s, (unsigned int)siglen);
		free(s);
	}
	return ret;
}

int
RSA_verify(int dtype, const unsigned char *m, unsigned int m_len,
    const unsigned char *sigbuf, unsigned int siglen, RSA *rsa)
{
	if ((rsa->flags & RSA_FLAG_SIGN_VER) && rsa->meth->rsa_verify)
		return rsa->meth->rsa_verify(dtype, m, m_len, sigbuf, siglen,
		    rsa);

	return int_rsa_verify(dtype, m, m_len, NULL, NULL, sigbuf, siglen, rsa);
}
