diff options
author | Dmitry Kasatkin <dmitry.kasatkin@intel.com> | 2011-11-07 15:16:37 +0200 |
---|---|---|
committer | Dmitry Kasatkin <dmitry.kasatkin@intel.com> | 2011-11-09 11:47:26 +0200 |
commit | 7e8dec918ef8e0f68b4937c3c50fa57002077a4d (patch) | |
tree | a17d33fa54fcb18c335b36c4550b889b206015f4 /lib/mpi/mpi-div.c | |
parent | d9c46b184fcfd33c85a7dc48a653435a08e21f56 (diff) |
crypto: GnuPG based MPI lib - additional sources (part 4)
Adds the multi-precision-integer maths library which was originally taken
from GnuPG and ported to the kernel by (among others) David Howells.
This version is taken from Fedora kernel 2.6.32-71.14.1.el6.
The difference is that checkpatch reported errors and warnings have been fixed.
This library is used to implemenet RSA digital signature verification
used in IMA/EVM integrity protection subsystem.
Due to patch size limitation, the patch is divided into 4 parts.
This code is unnecessary for RSA digital signature verification,
but for completeness it is included here and can be compiled,
if CONFIG_MPILIB_EXTRA is enabled.
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Diffstat (limited to 'lib/mpi/mpi-div.c')
-rw-r--r-- | lib/mpi/mpi-div.c | 333 |
1 files changed, 333 insertions, 0 deletions
diff --git a/lib/mpi/mpi-div.c b/lib/mpi/mpi-div.c new file mode 100644 index 000000000000..c3087d1390ce --- /dev/null +++ b/lib/mpi/mpi-div.c @@ -0,0 +1,333 @@ +/* mpi-div.c - MPI functions + * Copyright (C) 1994, 1996 Free Software Foundation, Inc. + * Copyright (C) 1998, 1999, 2000, 2001 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 + * + * Note: This code is heavily based on the GNU MP Library. + * Actually it's the same code with only minor changes in the + * way the data is stored; this is to support the abstraction + * of an optional secure memory allocation which may be used + * to avoid revealing of sensitive data due to paging etc. + * The GNU MP Library itself is published under the LGPL; + * however I decided to publish this code under the plain GPL. + */ + +#include <linux/string.h> +#include "mpi-internal.h" +#include "longlong.h" + +int mpi_fdiv_r(MPI rem, MPI dividend, MPI divisor) +{ + int rc = -ENOMEM; + int divisor_sign = divisor->sign; + MPI temp_divisor = NULL; + + /* We need the original value of the divisor after the remainder has been + * preliminary calculated. We have to copy it to temporary space if it's + * the same variable as REM. */ + if (rem == divisor) { + if (mpi_copy(&temp_divisor, divisor) < 0) + goto nomem; + divisor = temp_divisor; + } + + if (mpi_tdiv_qr(NULL, rem, dividend, divisor) < 0) + goto nomem; + if (((divisor_sign ? 1 : 0) ^ (dividend->sign ? 1 : 0)) && rem->nlimbs) + if (mpi_add(rem, rem, divisor) < 0) + goto nomem; + + rc = 0; + +nomem: + if (temp_divisor) + mpi_free(temp_divisor); + return rc; +} + +/**************** + * Division rounding the quotient towards -infinity. + * The remainder gets the same sign as the denominator. + * rem is optional + */ + +ulong mpi_fdiv_r_ui(MPI rem, MPI dividend, ulong divisor) +{ + mpi_limb_t rlimb; + + rlimb = mpihelp_mod_1(dividend->d, dividend->nlimbs, divisor); + if (rlimb && dividend->sign) + rlimb = divisor - rlimb; + + if (rem) { + rem->d[0] = rlimb; + rem->nlimbs = rlimb ? 1 : 0; + } + return rlimb; +} + +int mpi_fdiv_q(MPI quot, MPI dividend, MPI divisor) +{ + MPI tmp = mpi_alloc(mpi_get_nlimbs(quot)); + if (!tmp) + return -ENOMEM; + mpi_fdiv_qr(quot, tmp, dividend, divisor); + mpi_free(tmp); + return 0; +} + +int mpi_fdiv_qr(MPI quot, MPI rem, MPI dividend, MPI divisor) +{ + int divisor_sign = divisor->sign; + MPI temp_divisor = NULL; + + if (quot == divisor || rem == divisor) { + if (mpi_copy(&temp_divisor, divisor) < 0) + return -ENOMEM; + divisor = temp_divisor; + } + + if (mpi_tdiv_qr(quot, rem, dividend, divisor) < 0) + goto nomem; + + if ((divisor_sign ^ dividend->sign) && rem->nlimbs) { + if (mpi_sub_ui(quot, quot, 1) < 0) + goto nomem; + if (mpi_add(rem, rem, divisor) < 0) + goto nomem; + } + + if (temp_divisor) + mpi_free(temp_divisor); + + return 0; + +nomem: + mpi_free(temp_divisor); + return -ENOMEM; +} + +/* If den == quot, den needs temporary storage. + * If den == rem, den needs temporary storage. + * If num == quot, num needs temporary storage. + * If den has temporary storage, it can be normalized while being copied, + * i.e no extra storage should be allocated. + */ + +int mpi_tdiv_r(MPI rem, MPI num, MPI den) +{ + return mpi_tdiv_qr(NULL, rem, num, den); +} + +int mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den) +{ + int rc = -ENOMEM; + mpi_ptr_t np, dp; + mpi_ptr_t qp, rp; + mpi_size_t nsize = num->nlimbs; + mpi_size_t dsize = den->nlimbs; + mpi_size_t qsize, rsize; + mpi_size_t sign_remainder = num->sign; + mpi_size_t sign_quotient = num->sign ^ den->sign; + unsigned normalization_steps; + mpi_limb_t q_limb; + mpi_ptr_t marker[5]; + int markidx = 0; + + memset(marker, 0, sizeof(marker)); + + /* Ensure space is enough for quotient and remainder. + * We need space for an extra limb in the remainder, because it's + * up-shifted (normalized) below. */ + rsize = nsize + 1; + if (mpi_resize(rem, rsize) < 0) + goto nomem; + + qsize = rsize - dsize; /* qsize cannot be bigger than this. */ + if (qsize <= 0) { + if (num != rem) { + rem->nlimbs = num->nlimbs; + rem->sign = num->sign; + MPN_COPY(rem->d, num->d, nsize); + } + if (quot) { + /* This needs to follow the assignment to rem, in case the + * numerator and quotient are the same. */ + quot->nlimbs = 0; + quot->sign = 0; + } + return 0; + } + + if (quot) + if (mpi_resize(quot, qsize) < 0) + goto nomem; + + /* Read pointers here, when reallocation is finished. */ + np = num->d; + dp = den->d; + rp = rem->d; + + /* Optimize division by a single-limb divisor. */ + if (dsize == 1) { + mpi_limb_t rlimb; + if (quot) { + qp = quot->d; + rlimb = mpihelp_divmod_1(qp, np, nsize, dp[0]); + qsize -= qp[qsize - 1] == 0; + quot->nlimbs = qsize; + quot->sign = sign_quotient; + } else + rlimb = mpihelp_mod_1(np, nsize, dp[0]); + rp[0] = rlimb; + rsize = rlimb != 0 ? 1 : 0; + rem->nlimbs = rsize; + rem->sign = sign_remainder; + return 0; + } + + if (quot) { + qp = quot->d; + /* Make sure QP and NP point to different objects. Otherwise the + * numerator would be gradually overwritten by the quotient limbs. */ + if (qp == np) { /* Copy NP object to temporary space. */ + np = marker[markidx++] = mpi_alloc_limb_space(nsize); + MPN_COPY(np, qp, nsize); + } + } else /* Put quotient at top of remainder. */ + qp = rp + dsize; + + count_leading_zeros(normalization_steps, dp[dsize - 1]); + + /* Normalize the denominator, i.e. make its most significant bit set by + * shifting it NORMALIZATION_STEPS bits to the left. Also shift the + * numerator the same number of steps (to keep the quotient the same!). + */ + if (normalization_steps) { + mpi_ptr_t tp; + mpi_limb_t nlimb; + + /* Shift up the denominator setting the most significant bit of + * the most significant word. Use temporary storage not to clobber + * the original contents of the denominator. */ + tp = marker[markidx++] = mpi_alloc_limb_space(dsize); + if (!tp) + goto nomem; + mpihelp_lshift(tp, dp, dsize, normalization_steps); + dp = tp; + + /* Shift up the numerator, possibly introducing a new most + * significant word. Move the shifted numerator in the remainder + * meanwhile. */ + nlimb = mpihelp_lshift(rp, np, nsize, normalization_steps); + if (nlimb) { + rp[nsize] = nlimb; + rsize = nsize + 1; + } else + rsize = nsize; + } else { + /* The denominator is already normalized, as required. Copy it to + * temporary space if it overlaps with the quotient or remainder. */ + if (dp == rp || (quot && (dp == qp))) { + mpi_ptr_t tp; + + tp = marker[markidx++] = mpi_alloc_limb_space(dsize); + if (!tp) + goto nomem; + MPN_COPY(tp, dp, dsize); + dp = tp; + } + + /* Move the numerator to the remainder. */ + if (rp != np) + MPN_COPY(rp, np, nsize); + + rsize = nsize; + } + + q_limb = mpihelp_divrem(qp, 0, rp, rsize, dp, dsize); + + if (quot) { + qsize = rsize - dsize; + if (q_limb) { + qp[qsize] = q_limb; + qsize += 1; + } + + quot->nlimbs = qsize; + quot->sign = sign_quotient; + } + + rsize = dsize; + MPN_NORMALIZE(rp, rsize); + + if (normalization_steps && rsize) { + mpihelp_rshift(rp, rp, rsize, normalization_steps); + rsize -= rp[rsize - 1] == 0 ? 1 : 0; + } + + rem->nlimbs = rsize; + rem->sign = sign_remainder; + + rc = 0; +nomem: + while (markidx) + mpi_free_limb_space(marker[--markidx]); + return rc; +} + +int mpi_tdiv_q_2exp(MPI w, MPI u, unsigned count) +{ + mpi_size_t usize, wsize; + mpi_size_t limb_cnt; + + usize = u->nlimbs; + limb_cnt = count / BITS_PER_MPI_LIMB; + wsize = usize - limb_cnt; + if (limb_cnt >= usize) + w->nlimbs = 0; + else { + mpi_ptr_t wp; + mpi_ptr_t up; + + if (RESIZE_IF_NEEDED(w, wsize) < 0) + return -ENOMEM; + wp = w->d; + up = u->d; + + count %= BITS_PER_MPI_LIMB; + if (count) { + mpihelp_rshift(wp, up + limb_cnt, wsize, count); + wsize -= !wp[wsize - 1]; + } else { + MPN_COPY_INCR(wp, up + limb_cnt, wsize); + } + + w->nlimbs = wsize; + } + return 0; +} + +/**************** + * Check whether dividend is divisible by divisor + * (note: divisor must fit into a limb) + */ +int mpi_divisible_ui(MPI dividend, ulong divisor) +{ + return !mpihelp_mod_1(dividend->d, dividend->nlimbs, divisor); +} |