/* 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; nbytes -= lzeros; nbits = nbytes * 8; if (nbits > MAX_EXTERN_MPI_BITS) { sg_miter_stop(&miter); pr_info("MPI: mpi too large (%u bits)\n", nbits); return NULL; } if (nbytes > 0) nbits -= count_leading_zeros(*buff) - (BITS_PER_LONG - 8); sg_miter_stop(&miter); 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);