/* mpicoder.c  -  Coder for the external representation of MPIs * Copyright (C) 1998, 1999 Free Software Foundation, Inc. * * This file is part of GnuPG. * * GnuPG is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * GnuPG 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include <linux/bitops.h>#include <linux/count_zeros.h>#include <linux/byteorder/generic.h>#include <linux/scatterlist.h>#include <linux/string.h>#include "mpi-internal.h" #define MAX_EXTERN_MPI_BITS 16384 /** * mpi_read_raw_data - Read a raw byte stream as a positive integer * @xbuffer: The data to read * @nbytes: The amount of data to read */MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes){	const uint8_t *buffer = xbuffer;	int i, j;	unsigned nbits, nlimbs;	mpi_limb_t a;	MPI val = NULL; 	while (nbytes > 0 && buffer[0] == 0) {		buffer++;		nbytes--;	} 	nbits = nbytes * 8;	if (nbits > MAX_EXTERN_MPI_BITS) {		pr_info("MPI: mpi too large (%u bits)\n", nbits);		return NULL;	}	if (nbytes > 0)		nbits -= count_leading_zeros(buffer[0]) - (BITS_PER_LONG - 8); 	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);	val = mpi_alloc(nlimbs);	if (!val)		return NULL;	val->nbits = nbits;	val->sign = 0;	val->nlimbs = nlimbs; 	if (nbytes > 0) {		i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;		i %= BYTES_PER_MPI_LIMB;		for (j = nlimbs; j > 0; j--) {			a = 0;			for (; i < BYTES_PER_MPI_LIMB; i++) {				a <<= 8;				a |= *buffer++;			}			i = 0;			val->d[j - 1] = a;		}	}	return val;}EXPORT_SYMBOL_GPL(mpi_read_raw_data); MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread){	const uint8_t *buffer = xbuffer;	unsigned int nbits, nbytes;	MPI val; 	if (*ret_nread < 2)		return ERR_PTR(-EINVAL);	nbits = buffer[0] << 8 | buffer[1]; 	if (nbits > MAX_EXTERN_MPI_BITS) {		pr_info("MPI: mpi too large (%u bits)\n", nbits);		return ERR_PTR(-EINVAL);	} 	nbytes = DIV_ROUND_UP(nbits, 8);	if (nbytes + 2 > *ret_nread) {		pr_info("MPI: mpi larger than buffer nbytes=%u ret_nread=%u\n",				nbytes, *ret_nread);		return ERR_PTR(-EINVAL);	} 	val = mpi_read_raw_data(buffer + 2, nbytes);	if (!val)		return ERR_PTR(-ENOMEM); 	*ret_nread = nbytes + 2;	return val;}EXPORT_SYMBOL_GPL(mpi_read_from_buffer); static int count_lzeros(MPI a){	mpi_limb_t alimb;	int i, lzeros = 0; 	for (i = a->nlimbs - 1; i >= 0; i--) {		alimb = a->d[i];		if (alimb == 0) {			lzeros += sizeof(mpi_limb_t);		} else {			lzeros += count_leading_zeros(alimb) / 8;			break;		}	}	return lzeros;} /** * mpi_read_buffer() - read MPI to a bufer provided by user (msb first) * * @a:		a multi precision integer * @buf:	bufer to which the output will be written to. Needs to be at *		leaset mpi_get_size(a) long. * @buf_len:	size of the buf. * @nbytes:	receives the actual length of the data written on success and *		the data to-be-written on -EOVERFLOW in case buf_len was too *		small. * @sign:	if not NULL, it will be set to the sign of a. * * Return:	0 on success or error code in case of error */int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,		    int *sign){	uint8_t *p;#if BYTES_PER_MPI_LIMB == 4	__be32 alimb;#elif BYTES_PER_MPI_LIMB == 8	__be64 alimb;#else#error please implement for this limb size.#endif	unsigned int n = mpi_get_size(a);	int i, lzeros; 	if (!buf || !nbytes)		return -EINVAL; 	if (sign)		*sign = a->sign; 	lzeros = count_lzeros(a); 	if (buf_len < n - lzeros) {		*nbytes = n - lzeros;		return -EOVERFLOW;	} 	p = buf;	*nbytes = n - lzeros; 	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,			lzeros %= BYTES_PER_MPI_LIMB;		i >= 0; i--) {#if BYTES_PER_MPI_LIMB == 4		alimb = cpu_to_be32(a->d[i]);#elif BYTES_PER_MPI_LIMB == 8		alimb = cpu_to_be64(a->d[i]);#else#error please implement for this limb size.#endif		memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros);		p += BYTES_PER_MPI_LIMB - lzeros;		lzeros = 0;	}	return 0;}EXPORT_SYMBOL_GPL(mpi_read_buffer); /* * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first). * Caller must free the return string. * This function does return a 0 byte buffer with nbytes set to zero if the * value of A is zero. * * @a:		a multi precision integer. * @nbytes:	receives the length of this buffer. * @sign:	if not NULL, it will be set to the sign of the a. * * Return:	Pointer to MPI buffer or NULL on error */void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign){	uint8_t *buf;	unsigned int n;	int ret; 	if (!nbytes)		return NULL; 	n = mpi_get_size(a); 	if (!n)		n++; 	buf = kmalloc(n, GFP_KERNEL); 	if (!buf)		return NULL; 	ret = mpi_read_buffer(a, buf, n, nbytes, sign); 	if (ret) {		kfree(buf);		return NULL;	}	return buf;}EXPORT_SYMBOL_GPL(mpi_get_buffer); /** * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first) * * This function works in the same way as the mpi_read_buffer, but it * takes an sgl instead of u8 * buf. * * @a:		a multi precision integer * @sgl:	scatterlist to write to. Needs to be at least *		mpi_get_size(a) long. * @nbytes:	the number of bytes to write.  Leading bytes will be *		filled with zero. * @sign:	if not NULL, it will be set to the sign of a. * * Return:	0 on success or error code in case of error */int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes,		     int *sign){	u8 *p, *p2;#if BYTES_PER_MPI_LIMB == 4	__be32 alimb;#elif BYTES_PER_MPI_LIMB == 8	__be64 alimb;#else#error please implement for this limb size.#endif	unsigned int n = mpi_get_size(a);	struct sg_mapping_iter miter;	int i, x, buf_len;	int nents; 	if (sign)		*sign = a->sign; 	if (nbytes < n)		return -EOVERFLOW; 	nents = sg_nents_for_len(sgl, nbytes);	if (nents < 0)		return -EINVAL; 	sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_TO_SG);	sg_miter_next(&miter);	buf_len = miter.length;	p2 = miter.addr; 	while (nbytes > n) {		i = min_t(unsigned, nbytes - n, buf_len);		memset(p2, 0, i);		p2 += i;		nbytes -= i; 		buf_len -= i;		if (!buf_len) {			sg_miter_next(&miter);			buf_len = miter.length;			p2 = miter.addr;		}	} 	for (i = a->nlimbs - 1; i >= 0; i--) {#if BYTES_PER_MPI_LIMB == 4		alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0;#elif BYTES_PER_MPI_LIMB == 8		alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0;#else#error please implement for this limb size.#endif		p = (u8 *)&alimb; 		for (x = 0; x < sizeof(alimb); x++) {			*p2++ = *p++;			if (!--buf_len) {				sg_miter_next(&miter);				buf_len = miter.length;				p2 = miter.addr;			}		}	} 	sg_miter_stop(&miter);	return 0;}EXPORT_SYMBOL_GPL(mpi_write_to_sgl); /* * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with *			     data from the sgl * * This function works in the same way as the mpi_read_raw_data, but it * takes an sgl instead of void * buffer. i.e. it allocates * a new MPI and reads the content of the sgl to the MPI. * * @sgl:	scatterlist to read from * @nbytes:	number of bytes to read * * Return:	Pointer to a new MPI or NULL on error */MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes){	struct sg_mapping_iter miter;	unsigned int nbits, nlimbs;	int x, j, z, lzeros, ents;	unsigned int len;	const u8 *buff;	mpi_limb_t a;	MPI val = NULL; 	ents = sg_nents_for_len(sgl, nbytes);	if (ents < 0)		return NULL; 	sg_miter_start(&miter, sgl, ents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); 	lzeros = 0;	len = 0;	while (nbytes > 0) {		while (len && !*buff) {			lzeros++;			len--;			buff++;		} 		if (len && *buff)			break; 		sg_miter_next(&miter);		buff = miter.addr;		len = miter.length; 		nbytes -= lzeros;		lzeros = 0;	} 	miter.consumed = lzeros;	sg_miter_stop(&miter); 	nbytes -= lzeros;	nbits = nbytes * 8;	if (nbits > MAX_EXTERN_MPI_BITS) {		pr_info("MPI: mpi too large (%u bits)\n", nbits);		return NULL;	} 	if (nbytes > 0)		nbits -= count_leading_zeros(*buff) - (BITS_PER_LONG - 8); 	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);	val = mpi_alloc(nlimbs);	if (!val)		return NULL; 	val->nbits = nbits;	val->sign = 0;	val->nlimbs = nlimbs; 	if (nbytes == 0)		return val; 	j = nlimbs - 1;	a = 0;	z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;	z %= BYTES_PER_MPI_LIMB; 	while (sg_miter_next(&miter)) {		buff = miter.addr;		len = miter.length; 		for (x = 0; x < len; x++) {			a <<= 8;			a |= *buff++;			if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {				val->d[j--] = a;				a = 0;			}		}		z += x;	} 	return val;}EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);