1 /* mpi-mul.c  -  MPI functions
2  * Copyright (C) 1994, 1996, 1998, 2001, 2002,
3  *               2003 Free Software Foundation, Inc.
4  *
5  * This file is part of Libgcrypt.
6  *
7  * Note: This code is heavily based on the GNU MP Library.
8  *	 Actually it's the same code with only minor changes in the
9  *	 way the data is stored; this is to support the abstraction
10  *	 of an optional secure memory allocation which may be used
11  *	 to avoid revealing of sensitive data due to paging etc.
12  */
13 
14 #include "mpi-internal.h"
15 
mpi_mul(MPI w,MPI u,MPI v)16 int mpi_mul(MPI w, MPI u, MPI v)
17 {
18 	mpi_size_t usize, vsize, wsize;
19 	mpi_ptr_t up, vp, wp;
20 	mpi_limb_t cy;
21 	int usign, vsign, sign_product;
22 	int assign_wp = 0;
23 	mpi_ptr_t tmp_limb = NULL;
24 	int err = 0;
25 
26 	if (u->nlimbs < v->nlimbs) {
27 		/* Swap U and V. */
28 		usize = v->nlimbs;
29 		usign = v->sign;
30 		up    = v->d;
31 		vsize = u->nlimbs;
32 		vsign = u->sign;
33 		vp    = u->d;
34 	} else {
35 		usize = u->nlimbs;
36 		usign = u->sign;
37 		up    = u->d;
38 		vsize = v->nlimbs;
39 		vsign = v->sign;
40 		vp    = v->d;
41 	}
42 	sign_product = usign ^ vsign;
43 	wp = w->d;
44 
45 	/* Ensure W has space enough to store the result.  */
46 	wsize = usize + vsize;
47 	if (w->alloced < wsize) {
48 		if (wp == up || wp == vp) {
49 			wp = mpi_alloc_limb_space(wsize);
50 			if (!wp)
51 				return -ENOMEM;
52 			assign_wp = 1;
53 		} else {
54 			err = mpi_resize(w, wsize);
55 			if (err)
56 				return err;
57 			wp = w->d;
58 		}
59 	} else { /* Make U and V not overlap with W.	*/
60 		if (wp == up) {
61 			/* W and U are identical.  Allocate temporary space for U. */
62 			up = tmp_limb = mpi_alloc_limb_space(usize);
63 			if (!up)
64 				return -ENOMEM;
65 			/* Is V identical too?  Keep it identical with U.  */
66 			if (wp == vp)
67 				vp = up;
68 			/* Copy to the temporary space.  */
69 			MPN_COPY(up, wp, usize);
70 		} else if (wp == vp) {
71 			/* W and V are identical.  Allocate temporary space for V. */
72 			vp = tmp_limb = mpi_alloc_limb_space(vsize);
73 			if (!vp)
74 				return -ENOMEM;
75 			/* Copy to the temporary space.  */
76 			MPN_COPY(vp, wp, vsize);
77 		}
78 	}
79 
80 	if (!vsize)
81 		wsize = 0;
82 	else {
83 		err = mpihelp_mul(wp, up, usize, vp, vsize, &cy);
84 		if (err) {
85 			if (assign_wp)
86 				mpi_free_limb_space(wp);
87 			goto free_tmp_limb;
88 		}
89 		wsize -= cy ? 0:1;
90 	}
91 
92 	if (assign_wp)
93 		mpi_assign_limb_space(w, wp, wsize);
94 	w->nlimbs = wsize;
95 	w->sign = sign_product;
96 
97 free_tmp_limb:
98 	if (tmp_limb)
99 		mpi_free_limb_space(tmp_limb);
100 	return err;
101 }
102 EXPORT_SYMBOL_GPL(mpi_mul);
103 
mpi_mulm(MPI w,MPI u,MPI v,MPI m)104 int mpi_mulm(MPI w, MPI u, MPI v, MPI m)
105 {
106 	return mpi_mul(w, u, v) ?:
107 	       mpi_tdiv_r(w, w, m);
108 }
109 EXPORT_SYMBOL_GPL(mpi_mulm);
110