/* 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 <asm-generic/bitops/count_zeros.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]); else nbits = 0; 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; int i, j; unsigned nbits, nbytes, nlimbs, nread = 0; mpi_limb_t a; MPI val = NULL; if (*ret_nread < 2) goto leave; nbits = buffer[0] << 8 | buffer[1]; if (nbits > MAX_EXTERN_MPI_BITS) { pr_info("MPI: mpi too large (%u bits)\n", nbits); goto leave; } buffer += 2; nread = 2; nbytes = DIV_ROUND_UP(nbits, 8); nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); val = mpi_alloc(nlimbs); if (!val) return NULL; i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB; i %= BYTES_PER_MPI_LIMB; val->nbits = nbits; j = val->nlimbs = nlimbs; val->sign = 0; for (; j > 0; j--) { a = 0; for (; i < BYTES_PER_MPI_LIMB; i++) { if (++nread > *ret_nread) { printk ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n", nread, *ret_nread); goto leave; } a <<= 8; a |= *buffer++; } i = 0; val->d[j - 1] = a; } leave: *ret_nread = nread; return val; } EXPORT_SYMBOL_GPL(mpi_read_from_buffer); /**************** * Return an allocated buffer with the MPI (msb first). * NBYTES receives the length of this buffer. 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. If sign is not NULL, it will * be set to the sign of the A. */ void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign) { uint8_t *p, *buffer; mpi_limb_t alimb; int i; unsigned int n; if (sign) *sign = a->sign; *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB; if (!n) n++; /* avoid zero length allocation */ p = buffer = kmalloc(n, GFP_KERNEL); if (!p) return NULL; for (i = a->nlimbs - 1; i >= 0; i--) { alimb = a->d[i]; #if BYTES_PER_MPI_LIMB == 4 *p++ = alimb >> 24; *p++ = alimb >> 16; *p++ = alimb >> 8; *p++ = alimb; #elif BYTES_PER_MPI_LIMB == 8 *p++ = alimb >> 56; *p++ = alimb >> 48; *p++ = alimb >> 40; *p++ = alimb >> 32; *p++ = alimb >> 24; *p++ = alimb >> 16; *p++ = alimb >> 8; *p++ = alimb; #else #error please implement for this limb size. #endif } /* this is sub-optimal but we need to do the shift operation * because the caller has to free the returned buffer */ for (p = buffer; !*p && *nbytes; p++, --*nbytes) ; if (p != buffer) memmove(buffer, p, *nbytes); return buffer; } EXPORT_SYMBOL_GPL(mpi_get_buffer); /**************** * Use BUFFER to update MPI. */ int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign) { const uint8_t *buffer = xbuffer, *p; mpi_limb_t alimb; int nlimbs; int i; nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB); if (RESIZE_IF_NEEDED(a, nlimbs) < 0) return -ENOMEM; a->sign = sign; for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) { #if BYTES_PER_MPI_LIMB == 4 alimb = (mpi_limb_t) *p--; alimb |= (mpi_limb_t) *p-- << 8; alimb |= (mpi_limb_t) *p-- << 16; alimb |= (mpi_limb_t) *p-- << 24; #elif BYTES_PER_MPI_LIMB == 8 alimb = (mpi_limb_t) *p--; alimb |= (mpi_limb_t) *p-- << 8; alimb |= (mpi_limb_t) *p-- << 16; alimb |= (mpi_limb_t) *p-- << 24; alimb |= (mpi_limb_t) *p-- << 32; alimb |= (mpi_limb_t) *p-- << 40; alimb |= (mpi_limb_t) *p-- << 48; alimb |= (mpi_limb_t) *p-- << 56; #else #error please implement for this limb size. #endif a->d[i++] = alimb; } if (p >= buffer) { #if BYTES_PER_MPI_LIMB == 4 alimb = *p--; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 8; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 16; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 24; #elif BYTES_PER_MPI_LIMB == 8 alimb = (mpi_limb_t) *p--; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 8; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 16; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 24; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 32; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 40; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 48; if (p >= buffer) alimb |= (mpi_limb_t) *p-- << 56; #else #error please implement for this limb size. #endif a->d[i++] = alimb; } a->nlimbs = i; if (i != nlimbs) { pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i, nlimbs); BUG(); } return 0; } EXPORT_SYMBOL_GPL(mpi_set_buffer);