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>
This commit is contained in:
Dmitry Kasatkin
187
lib/mpi/mpi-inv.c
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187
lib/mpi/mpi-inv.c
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/* mpi-inv.c - MPI functions
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* Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include "mpi-internal.h"
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/****************
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* Calculate the multiplicative inverse X of A mod N
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* That is: Find the solution x for
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* 1 = (a*x) mod n
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*/
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int mpi_invm(MPI x, const MPI a, const MPI n)
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{
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/* Extended Euclid's algorithm (See TAOPC Vol II, 4.5.2, Alg X)
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* modified according to Michael Penk's solution for Exercice 35
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* with further enhancement */
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MPI u = NULL, v = NULL;
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MPI u1 = NULL, u2 = NULL, u3 = NULL;
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MPI v1 = NULL, v2 = NULL, v3 = NULL;
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MPI t1 = NULL, t2 = NULL, t3 = NULL;
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unsigned k;
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int sign;
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int odd = 0;
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int rc = -ENOMEM;
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if (mpi_copy(&u, a) < 0)
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goto cleanup;
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if (mpi_copy(&v, n) < 0)
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goto cleanup;
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for (k = 0; !mpi_test_bit(u, 0) && !mpi_test_bit(v, 0); k++) {
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if (mpi_rshift(u, u, 1) < 0)
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goto cleanup;
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if (mpi_rshift(v, v, 1) < 0)
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goto cleanup;
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}
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odd = mpi_test_bit(v, 0);
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u1 = mpi_alloc_set_ui(1);
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if (!u1)
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goto cleanup;
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if (!odd) {
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u2 = mpi_alloc_set_ui(0);
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if (!u2)
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goto cleanup;
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}
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if (mpi_copy(&u3, u) < 0)
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goto cleanup;
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if (mpi_copy(&v1, v) < 0)
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goto cleanup;
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if (!odd) {
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v2 = mpi_alloc(mpi_get_nlimbs(u));
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if (!v2)
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goto cleanup;
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if (mpi_sub(v2, u1, u) < 0)
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goto cleanup; /* U is used as const 1 */
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}
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if (mpi_copy(&v3, v) < 0)
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goto cleanup;
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if (mpi_test_bit(u, 0)) { /* u is odd */
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t1 = mpi_alloc_set_ui(0);
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if (!t1)
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goto cleanup;
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if (!odd) {
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t2 = mpi_alloc_set_ui(1);
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if (!t2)
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goto cleanup;
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t2->sign = 1;
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}
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if (mpi_copy(&t3, v) < 0)
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goto cleanup;
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t3->sign = !t3->sign;
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goto Y4;
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} else {
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t1 = mpi_alloc_set_ui(1);
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if (!t1)
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goto cleanup;
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if (!odd) {
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t2 = mpi_alloc_set_ui(0);
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if (!t2)
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goto cleanup;
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}
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if (mpi_copy(&t3, u) < 0)
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goto cleanup;
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}
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do {
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do {
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if (!odd) {
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if (mpi_test_bit(t1, 0) || mpi_test_bit(t2, 0)) { /* one is odd */
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if (mpi_add(t1, t1, v) < 0)
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goto cleanup;
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if (mpi_sub(t2, t2, u) < 0)
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goto cleanup;
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}
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if (mpi_rshift(t1, t1, 1) < 0)
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goto cleanup;
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if (mpi_rshift(t2, t2, 1) < 0)
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goto cleanup;
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if (mpi_rshift(t3, t3, 1) < 0)
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goto cleanup;
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} else {
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if (mpi_test_bit(t1, 0))
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if (mpi_add(t1, t1, v) < 0)
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goto cleanup;
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if (mpi_rshift(t1, t1, 1) < 0)
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goto cleanup;
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if (mpi_rshift(t3, t3, 1) < 0)
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goto cleanup;
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}
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Y4:
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;
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} while (!mpi_test_bit(t3, 0)); /* while t3 is even */
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if (!t3->sign) {
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if (mpi_set(u1, t1) < 0)
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goto cleanup;
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if (!odd)
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if (mpi_set(u2, t2) < 0)
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goto cleanup;
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if (mpi_set(u3, t3) < 0)
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goto cleanup;
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} else {
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if (mpi_sub(v1, v, t1) < 0)
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goto cleanup;
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sign = u->sign;
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u->sign = !u->sign;
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if (!odd)
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if (mpi_sub(v2, u, t2) < 0)
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goto cleanup;
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u->sign = sign;
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sign = t3->sign;
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t3->sign = !t3->sign;
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if (mpi_set(v3, t3) < 0)
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goto cleanup;
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t3->sign = sign;
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}
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if (mpi_sub(t1, u1, v1) < 0)
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goto cleanup;
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if (!odd)
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if (mpi_sub(t2, u2, v2) < 0)
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goto cleanup;
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if (mpi_sub(t3, u3, v3) < 0)
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goto cleanup;
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if (t1->sign) {
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if (mpi_add(t1, t1, v) < 0)
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goto cleanup;
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if (!odd)
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if (mpi_sub(t2, t2, u) < 0)
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goto cleanup;
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}
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} while (mpi_cmp_ui(t3, 0)); /* while t3 != 0 */
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/* mpi_lshift( u3, k ); */
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rc = mpi_set(x, u1);
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cleanup:
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mpi_free(u1);
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mpi_free(v1);
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mpi_free(t1);
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if (!odd) {
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mpi_free(u2);
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mpi_free(v2);
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mpi_free(t2);
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}
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mpi_free(u3);
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mpi_free(v3);
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mpi_free(t3);
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mpi_free(u);
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mpi_free(v);
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return rc;
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}
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