path: root/lib/gnutls_mpi.c

/*
 * Copyright (C) 2001-2012 Free Software Foundation, Inc.
 *
 * Author: Nikos Mavrogiannopoulos
 *
 * This file is part of GnuTLS.
 *
 * The GnuTLS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

/* Here lie everything that has to do with large numbers, libgcrypt and
 * other stuff that didn't fit anywhere else.
 */

#include <gnutls_int.h>
#include <libtasn1.h>
#include <gnutls_errors.h>
#include <gnutls_num.h>
#include <gnutls_mpi.h>
#include <random.h>
#include <x509/x509_int.h>

/* Functions that refer to the mpi library.
 */

#define clearbit(v,n)    ((unsigned char)(v) & ~( (unsigned char)(1) << (unsigned)(n)))

bigint_t
_gnutls_mpi_randomize(bigint_t r, unsigned int bits,
		      gnutls_rnd_level_t level)
{
	size_t size = 1 + (bits / 8);
	int ret;
	int rem, i;
	bigint_t tmp;
	uint8_t tmpbuf[512];
	uint8_t *buf;
	int buf_release = 0;

	if (size < sizeof(tmpbuf)) {
		buf = tmpbuf;
	} else {
		buf = gnutls_malloc(size);
		if (buf == NULL) {
			gnutls_assert();
			goto cleanup;
		}
		buf_release = 1;
	}


	ret = _gnutls_rnd(level, buf, size);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	/* mask the bits that weren't requested */
	rem = bits % 8;

	if (rem == 0) {
		buf[0] = 0;
	} else {
		for (i = 8; i >= rem; i--)
			buf[0] = clearbit(buf[0], i);
	}

	ret = _gnutls_mpi_scan(&tmp, buf, size);
	if (ret < 0) {
		gnutls_assert();
		goto cleanup;
	}

	if (buf_release != 0) {
		gnutls_free(buf);
		buf = NULL;
	}

	if (r != NULL) {
		_gnutls_mpi_set(r, tmp);
		_gnutls_mpi_release(&tmp);
		return r;
	}

	return tmp;

      cleanup:
	if (buf_release != 0)
		gnutls_free(buf);
	return NULL;
}

void _gnutls_mpi_release(bigint_t * x)
{
	if (*x == NULL)
		return;

	_gnutls_mpi_ops.bigint_release(*x);
	*x = NULL;
}

/* returns %GNUTLS_E_SUCCESS (0) on success
 */
int _gnutls_mpi_scan(bigint_t * ret_mpi, const void *buffer, size_t nbytes)
{
	*ret_mpi =
	    _gnutls_mpi_ops.bigint_scan(buffer, nbytes,
					GNUTLS_MPI_FORMAT_USG);
	if (*ret_mpi == NULL) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	return 0;
}

/* returns %GNUTLS_E_SUCCESS (0) on success. Fails if the number is zero.
 */
int
_gnutls_mpi_scan_nz(bigint_t * ret_mpi, const void *buffer, size_t nbytes)
{
	int ret;

	ret = _gnutls_mpi_scan(ret_mpi, buffer, nbytes);
	if (ret < 0)
		return ret;

	/* MPIs with 0 bits are illegal
	 */
	if (_gnutls_mpi_cmp_ui(*ret_mpi, 0) == 0) {
		_gnutls_mpi_release(ret_mpi);
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	return 0;
}

int
_gnutls_mpi_scan_pgp(bigint_t * ret_mpi, const void *buffer, size_t nbytes)
{
	*ret_mpi =
	    _gnutls_mpi_ops.bigint_scan(buffer, nbytes,
					GNUTLS_MPI_FORMAT_PGP);
	if (*ret_mpi == NULL) {
		gnutls_assert();
		return GNUTLS_E_MPI_SCAN_FAILED;
	}

	return 0;
}

/* Always has the first bit zero */
int _gnutls_mpi_dprint_lz(const bigint_t a, gnutls_datum_t * dest)
{
	int ret;
	uint8_t *buf = NULL;
	size_t bytes = 0;

	if (dest == NULL || a == NULL)
		return GNUTLS_E_INVALID_REQUEST;

	_gnutls_mpi_print_lz(a, NULL, &bytes);

	if (bytes != 0)
		buf = gnutls_malloc(bytes);
	if (buf == NULL)
		return GNUTLS_E_MEMORY_ERROR;

	ret = _gnutls_mpi_print_lz(a, buf, &bytes);
	if (ret < 0) {
		gnutls_free(buf);
		return ret;
	}

	dest->data = buf;
	dest->size = bytes;
	return 0;
}

int _gnutls_mpi_dprint(const bigint_t a, gnutls_datum_t * dest)
{
	int ret;
	uint8_t *buf = NULL;
	size_t bytes = 0;

	if (dest == NULL || a == NULL)
		return GNUTLS_E_INVALID_REQUEST;

	_gnutls_mpi_print(a, NULL, &bytes);
	if (bytes != 0)
		buf = gnutls_malloc(bytes);
	if (buf == NULL)
		return GNUTLS_E_MEMORY_ERROR;

	ret = _gnutls_mpi_print(a, buf, &bytes);
	if (ret < 0) {
		gnutls_free(buf);
		return ret;
	}

	dest->data = buf;
	dest->size = bytes;
	return 0;
}

/* This function will copy the mpi data into a datum,
 * but will set minimum size to 'size'. That means that
 * the output value is left padded with zeros.
 */
int
_gnutls_mpi_dprint_size(const bigint_t a, gnutls_datum_t * dest,
			size_t size)
{
	int ret;
	uint8_t *buf = NULL;
	size_t bytes = 0;
	unsigned int i;

	if (dest == NULL || a == NULL)
		return GNUTLS_E_INVALID_REQUEST;

	_gnutls_mpi_print(a, NULL, &bytes);
	if (bytes != 0)
		buf = gnutls_malloc(MAX(size, bytes));
	if (buf == NULL)
		return GNUTLS_E_MEMORY_ERROR;

	if (bytes <= size) {
		size_t diff = size - bytes;
		for (i = 0; i < diff; i++)
			buf[i] = 0;
		ret = _gnutls_mpi_print(a, &buf[diff], &bytes);
	} else {
		ret = _gnutls_mpi_print(a, buf, &bytes);
	}

	if (ret < 0) {
		gnutls_free(buf);
		return ret;
	}

	dest->data = buf;
	dest->size = MAX(size, bytes);
	return 0;
}

/* this function reads an integer
 * from asn1 structs. Combines the read and mpi_scan
 * steps.
 */
int
_gnutls_x509_read_int(ASN1_TYPE node, const char *value,
		      bigint_t * ret_mpi)
{
	int result;
	uint8_t *tmpstr = NULL;
	int tmpstr_size;

	tmpstr_size = 0;
	result = asn1_read_value(node, value, NULL, &tmpstr_size);
	if (result != ASN1_MEM_ERROR) {
		gnutls_assert();
		return _gnutls_asn2err(result);
	}

	tmpstr = gnutls_malloc(tmpstr_size);
	if (tmpstr == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	result = asn1_read_value(node, value, tmpstr, &tmpstr_size);
	if (result != ASN1_SUCCESS) {
		gnutls_assert();
		gnutls_free(tmpstr);
		return _gnutls_asn2err(result);
	}

	result = _gnutls_mpi_scan(ret_mpi, tmpstr, tmpstr_size);
	gnutls_free(tmpstr);

	if (result < 0) {
		gnutls_assert();
		return result;
	}

	return 0;
}

/* Writes the specified integer into the specified node.
 */
int
_gnutls_x509_write_int(ASN1_TYPE node, const char *value, bigint_t mpi,
		       int lz)
{
	uint8_t *tmpstr;
	size_t s_len;
	int result;

	s_len = 0;
	if (lz)
		result = _gnutls_mpi_print_lz(mpi, NULL, &s_len);
	else
		result = _gnutls_mpi_print(mpi, NULL, &s_len);

	if (result != GNUTLS_E_SHORT_MEMORY_BUFFER) {
		gnutls_assert();
		return result;
	}

	tmpstr = gnutls_malloc(s_len);
	if (tmpstr == NULL) {
		gnutls_assert();
		return GNUTLS_E_MEMORY_ERROR;
	}

	if (lz)
		result = _gnutls_mpi_print_lz(mpi, tmpstr, &s_len);
	else
		result = _gnutls_mpi_print(mpi, tmpstr, &s_len);

	if (result != 0) {
		gnutls_assert();
		gnutls_free(tmpstr);
		return GNUTLS_E_MPI_PRINT_FAILED;
	}

	result = asn1_write_value(node, value, tmpstr, s_len);

	gnutls_free(tmpstr);

	if (result != ASN1_SUCCESS) {
		gnutls_assert();
		return _gnutls_asn2err(result);
	}

	return 0;
}